increases in snow albedo, and their inclusion in relevant chemical and climate models deserves consideration.

Taillandier, A. S., F. Domine, W. R. Simpson, M. Sturm, and T. A. Douglas (2007) : **Rate of decrease of the specific surface area of dry snow: Isothermal and temperature gradient conditions.** Journal of Geophysical Research-Earth Surface, 112(F3), F03003.

*Abstract:* The specific surface area (SSA) of snow is the surface area available to gases per unit mass. It is an important variable for quantifying air- snow exchange of chemical species, and it is closely related to other variables such as albedo. Snow SSA decreases during metamorphism, but few data are available to quantify its rate of decrease. We have performed laboratory experiments under isothermal and temperature gradient conditions during which the SSA of snow samples was monitored for several months. We have also monitored the SSA of snowfalls subjected to large temperature gradients at a field site in the central Alaskan taiga. The same snow layers were also monitored in a manipulated snowpack where the temperature gradient was greatly reduced. In all cases, the SSA decay follows a logarithmic equation with three adjustable variables that are parameterized using the initial snow SSA and the time- averaged temperature of the snow. Two parameterizations of the three adjustable variables are found: One applies to the isothermal experiments and to the quasi- isothermal cases studied in Alaska (equitemperature (ET) metamorphism), and the other is applicable to both the laboratory experiments performed under temperature gradients and to the natural snowpack in Alaska (temperature gradient (TG) metamorphism). Higher temperatures accelerate the decrease in SSA, and this decrease is faster under TG than ET conditions. We discuss the conditions of applicability of these parameterizations and use them to speculate on the effect of climate change on snow SSA. Depending on the climate regime, changes in the rate of decay of snow SSA and hence in snow albedo may produce either negative or positive feedbacks on climate change.

Morin., S., F. Domine, L. Arnaud and G. Picard (2010), **In-situ monitoring of the effective thermal conductivity of snow**, Cold Reg. Sci. Technol., 64, 73–80.

*Abstract:* We report on a 3-month long time series of in-situ measurements of the effective thermal conductivity ($k_{eff}$) of snow at 6 heights in an Alpine snowpack in the Mont-Blanc mountain range, France, at an altitude of 2400 m. Measurements were carried out automatically every 2 days using heated-needle probes embedded in the snowpack. The experimental procedure used is presented in detail and demonstrates the applicability of single heated-needle probes for the evaluation of $k_{eff}$ in snow, both for long-term measurements within the snowpack and occasional use in the field. Results based on 139 automatically collected data show $k_{eff}$ values ranging between 0.04 and 0.35 W m⁻¹ K⁻¹, and a consistent pattern of effective thermal conductivity increase throughout the measurements campaign. The temporal rate of change of $k_{eff}$ varies up to 0.01 W m⁻¹ K⁻¹ day⁻¹, with maximum values just after snowfall.

### 1-1-2 – Other references without abstracts

King, C. and Pomeroy, J.; Gray, D. M.; Fierz, C.; Föhn, P.; Harding, R.; Jordan, R. & Martin, E. and Plüss, C. Armstrong, R. & Brun, E. (Eds.) (2008), **Snow-atmosphere energy and mass balance Snow and Climate: Physical Processes, Surface Energy Exchange and Modelling**, Cambridge University Press, 70-124.
# 1-2 Snow observation (including remote sensing).

## 1-2-1 Main references with abstracts

Brucker, L., Picard, G. and Fily, M. **Snow grain size profiles deduced from microwave snow emissivities in Antarctica**. *Journal of Glaciology*, 56(197), 514-526, 2010 **TOC**

**ABSTRACT.** Spaceborne microwave radiometers are an attractive tool for observing Antarctic climate because their measurements are related to the snow temperature. However, the conversion from microwave emission to snow temperature is not simple and strongly depends on the emissivity through snow properties. This difficulty in predicting the snow property profile for Antarctic conditions is the main bottleneck in the retrieval of accurate climate information from microwave radiometers. We attempt to explain the vertically polarized emissivity at 19.3 and 37GHz derived from brightness temperatures acquired by the Special Sensor Microwave/Imager (SSM/I) and physical temperature from the ERA-40 re-analysis. In Antarctica the snow emissivities at 19.3 and 37GHz are nearly equal, although a decrease with frequency is expected. To explain this, we consider various profiles of snow grain size and density and predict their emissivity using a dense-medium radiative transfer (DMRT) model. The results show that the emissivities cannot be explained by constant profiles of grain size and density. Heterogeneous snowpacks need to be considered. We first test random variations of snow density and grain radius with depth and then monotonic and continuous variations in the snow grain radius. In both cases, we show that an overall increase of the snow grain radius with depth is required to match the observed emissivity in Antarctica. In addition, two parameters characterizing the snow grain profiles are retrieved and compared with (1) in situ measurements of grain size at various locations in East Antarctica, (2) grain size estimated using visible spaceborne radiometers and (3) a semi-empirical relationship for grain growth.

J.-C. Gallet, F. Domine, C. Zender, and G. Picard **Measurement of the specific surface area of snow using infrared reflectance in an integrating sphere at 1310 and 1550 nm**

*The Cryosphere* Vol.3, pp. 167-182, 2009

**Abstract.** Even though the specific surface area (SSA) and the snow area index (SAI) of snow are crucial variables to determine the chemical and climatic impact of the snow cover, few data are available on the subject. We propose here a novel method to measure snow SSA and SAI. It is based on the measurement of the hemispherical infrared reflectance of snow samples using the DUFISSS instrument (DUal Frequency Integrating Sphere for Snow SSA measurement). DUFISSS uses the 1310 or 1550 nm radiation of laser diodes, an integrating sphere 15 cm in diameter, and InGaAs photodiodes. For SSA<60 m² kg⁻¹, we use the 1310 nm radiation, reflectance is between 15 and 50% and the accuracy of SSA determination is 10%. For SSA>60 m² kg⁻¹, snow is usually of low density (typically 30 to 100 kg m⁻³), resulting in insufficient optical depth and 1310 nm radiation reaches the bottom of the sample, causing artifacts. The 1550 nm radiation is therefore used for SSA>60 m² kg⁻¹. Reflectance is then in the range 5 to 12% and the accuracy on SSA is 12%. We propose empirical equations to determine SSA from reflectance at both wavelengths, with that for 1310 nm taking into account the snow density. DUFISSS has been used to measure the SSA of snow and the SAI of snowpacks in polar and Alpine regions.
G. Picard, L. Brucker, M. Fily, H. Gallée, G. Krinner, **Modeling timeseries of
microwave brightness temperature in Antarctica**. *Journal of Glaciology*, 55 (191), pp
537-551, 2009.

ABSTRACT. This paper aims to interpret the temporal variations of microwave brightness temperature (at 19 and 37GHz and at vertical and horizontal polarizations) in Antarctica using a physically based snow dynamic and emission model (SDEM). SDEM predicts time series of top-of-atmosphere brightness temperature from widely available surface meteorological data (ERA-40 re-analysis). To do so, it successively computes the heat flux incoming the snowpack, the snow temperature profile, the microwaves emitted by the snow and, finally, the propagation of the microwaves through the atmosphere up to the satellite. Since the model contains several parameters whose value is variable and uncertain across the continent, the parameter values are optimized for every 50 km × 50 km pixel. Simulation results show that the model is inadequate in the melt zone (where surface melting occurs on at least a few days a year) because the snowpack structure and its temporal variations are too complex. In contrast, the accuracy is reasonably good in the dry zone and varies between 2 and 4 K depending on the frequency and polarization of observations and on the location. At the Antarctic scale, the error is larger where wind is usually stronger, suggesting either that meteorological data are less accurate in windy regions or that some neglected processes (e.g. windpumping, surface scouring) are important. At Dome C, in calm conditions, a detailed analysis shows that most of the error is due to inaccuracy of the ERA-40 air temperature (2 K). Finally, the paper discusses the values of the optimized parameters and their spatial variations across the Antarctic.

A. Mialon, Royer, A., Fily, M., Picard, G., 2007, **Daily Microwave-Derived Surface Temperature over Canada/Alaska** *Journal of Applied Meteorology and Climatology*, vol 46, issue 5 (May 2007), p 591-604.

The land surface temperature variation over northern high latitudes in response to the increase in greenhouse gases is challenging because of the lack of meteorological stations. A new method to derive the surface temperature from satellite microwave measurements that improves the frequency of measurements relative to that of infrared data is presented. The daily Special Sensor Microwave Imager 25 km × 25 km Equal-Area Scalable Earth Grid (EASE-Grid) dataset provided by the National Snow and Ice Data Center in Boulder, Colorado, is processed to derive the surface temperature using the method proposed by Fily et al. A normalization approach based on the 40-yr ECMWF reanalysis (ERA-40; 2.5°) temperature diurnal cycle fitted for each pixel is applied to overcome the time acquisition variation of measurements as well as to interpolate missing data. An adaptive mask for discriminating between ice-free pixels and snow-free pixels is also applied. The resulting database is thus a new consistent hourly series of near-surface air temperatures during the summer (without snow). The mean accuracy is on the order of 2.5–3 K when compared with the synchronous in situ air temperature and different gridded datasets over Canada and Alaska. The trend over the last 10 yr confirms observed climate evolution: an increase in summer surface temperature of +0.09° ± 0.04°C yr⁻¹, at the 90% confidence level, for Canada between 1992 and 2002, whereas a decrease of -0.15° ± 0.05°C yr⁻¹, at the 95% confidence level, is observed for Alaska. Spatial and temporal anomalies show regional impacts of meteorological phenomena such as the El Niño extreme warm summer episode of 1998, the decrease in temperatures in 1992 in Canada following the volcanic eruption of Mount Pinatubo in June 1991, and the strong drought in the
prairies in 2001. The annual sum of positive degree-days (thawing index) has been related to the permafrost distribution. The lower values of the derived thawing index (<1400 degree-days) are related well to the presence of continuous and dense discontinuous permafrost. The observed increase in the thawing index during the 1992–2002 period represents a decrease of classified permafrost area of 7%.

Bouchard, A., F. Rabier, V. Guidard, F. Karbou (2010), Enhancement of satellite data assimilation over Antarctica, Monthly Weather Review, Vol. 138, No. 6., 2149–2173, doi: 10.1175/2009MWR3071.1.

**Abstract:** The Concordiasi field experiment, which is took place in Antarctica, involved the launching of radiosoundings and stratospheric balloons. One of the main goals of this campaign is the validation of the Infrared Atmospheric Sounding Interferometer (IASI) radiance assimilation. Prior to the campaign, it was necessary to improve satellite data assimilation at high latitudes. Two types of sensors, microwave and infrared, have been considered to help with this issue. A major problem associated with microwave satellite data is the calculation of the surface emissivity. An innovative approach, based on satellite observations, improves the surface emissivity modeling over land and sea ice within the constraints of the four-dimensional variational data assimilation (4D-VAR) system. With this new calculation of emissivity, it has been possible to include many more microwave observations during the assimilation. In this study, this method has been applied to high latitudes, after some adjustments have been made to assimilate additional Advanced Microwave Sounding Unit-A/B (AMSU-A/B) data over sea ice and snow. The use of additional data from IASI and the Atmospheric Infrared Sounder (AIRS) sensors over land and sea ice has also been tested. The use of the microwave and infrared data over this polar area has modified the dynamical and thermodynamical model fields such as the snow precipitation quantity. Additional data have been found to have a positive impact on the skill of a model specially tuned for Antarctica (see the accompanying figure for some forecast scores).

Guedj, S., F. Karbou, F. Rabier, A. Bouchard (2010), Microwave land emissivity over Antarctica: Impact of the surface approximation, IEEE Trans. on Geoscience and Remote sensing, Vol. 48, Issue 4, 1976-1985, 10.1109/TGRS.2009.2036254

**Abstract:** This work is in direct line with the Concordiasi international project. It aims to better constrain atmospheric analyses by improving the assimilation of low-level Advanced Microwave Sounding Unit (AMSU)-A and AMSU-B microwave observations over Antarctica. So far, a very small amount of available AMSU observations is effectively assimilated over Antarctica. To assimilate more observations, different issues have to be dealt with. In this work, the surface emissivity issue over Antarctica is examined. In a first step, a thorough review of the use of a specular assumption to calculate emissivity from AMSU-A measurements has been undertaken. The effect of five different assumptions about the surface on retrieved AMSU emissivities has then been evaluated using a one-year database: specular, Lambertian, and three intermediate assumptions. Simulations of brightness temperatures at AMSU sounding frequencies have been produced using a radiative transfer model. The emissivities obtained using the five assumptions have been found very useful in improving these simulations (see the following figure). The most successful schemes are found to be the Lambertian scheme during the winter season and a specular or an intermediate scheme (50% specular, 50% Lambertian) during Antarctica's short summer.
Longepe, N., S. Allain, L. Ferro-Famil, E. Pottier and Y. Durand (2009) : **Snowpack Characterization in Mountainous Regions Using C-Band SAR Data and a Meteorological Model**. IEEE Transactions on Geoscience and Remote Sensing, 47(2), 406-418.

***Abstract***: This paper presents a method to characterize snow cover in mountainous regions using dual-polarization C-band synthetic aperture radar (SAR) data. It is demonstrated that an accurate modeling of the liquid water distribution inside the snowpack, using a multilayer meteorological snow model, is required to characterize snow with precision. A multilayer-snow electromagnetic (EM) backscattering model is developed based on the vector radiative transfer, the strong fluctuation theory, and physical parameters supplied by the meteorological model. However, the limited resolution of the meteorological snow model is insufficient for predicting a refined EM backscattering at a massif scale. An adequate spatial reorganization of these snow profiles, based on a comparison between simulated and measured dual-polarization SAR data, leads to a better estimation of some snowpack parameters. In particular, the monitoring of snow liquid water content is presented improving the capacity of wet snow mapping as compared to a classical SAR-based method. This methodology shows good capacities both for qualitative and quantitative snow assessments, opening the way for a new operational method.

**1-2-2 – Other references without abstracts**

Dumont, M., Brissaud, O., Picard, G., Schmitt, B., Gallet, J.-C., and Arnaud, Y. **High-accuracy measurements of snow Bidirectional Reflectance Distribution Function at visible and NIR wavelengths - comparison with modelling results**, *Atmos. Chem. Phys.*, 10, 2507-2520.

J.C. Gallet, F. Domine, L. Arnaud, G. Picard, and J. Savarino, **Vertical profiles of the specific surface area of the snow at Dome C, Antarctica**, *The Cryosphere Discussion*, 4, 1647-1708, 2010.

Langlois, A., Royer, A., Montpetit, B., Picard, G., Brucker, L., Arnaud, L., Goïta, K. and Fily, M. **On the relationship between snow grain morphology and in-situ near infrared calibrated reflectance photographs**, *Cold Regions Science and Technology*, 61, pp 34-42, 2010.

M. van den Broeke, G. König-Langlo, G. Picard, P. Kuipers Munneke and J. Lenaerts **Surface energy balance, melt and sublimation at Neumayer Station, East Antarctica**. *Antarctic Science*, 22 (01), pp 87-96, Feb 2010.

G. Picard, L. Arnaud, F. Domine, M. Fily, **Determining snow specific surface area from near-infrared reflectance measurements: numerical study of the influence of grain shape**. *Cold Region Science and Technology*, 56 (1), pp 10-17, 2009.

Lacroix, P., Legresy, B., Remy, F., Blarel, F., Picard, G. and Brucker, L. **Rapid change of the snow surface properties at Vostok, East Antarctica, revealed by altimetry and radiometry**. *Remote Sensing of Environment*, 113(12), pp 2633-2641, Dec 2009.
# 1-3 Snow chemistry (including water isotopes)

## 1-3-1 Main references with abstracts

Amoroso, A., et al. (2010): **Microorganisms in Dry Polar Snow Are Involved in the Exchanges of Reactive Nitrogen Species with the Atmosphere**, Environmental Science & Technology. 44(2), 714-719.

**Abstract:** The snowpack is a complex photochemical reactor that emits a wide variety of reactive molecules to the atmosphere. In particular, the photolysis of nitrate ions, NO3-, produces NO, NO2, and HONO, which affects the oxidative capacity of the atmosphere. We report measurements in the European High Arctic where we observed for the first time emissions of NO, NO2, and HONO by the seasonal snowpack in winter, in the complete or near-complete absence of sunlight and in the absence of melting. We also detected unusually high concentrations of nitrite ions, NO2-, in the snow. These results suggest that microbial activity in the snowpack is responsible for the observed emissions. Isotopic analysis of NO2- and NO3- in the snow confirm that these ions, at least in part, do not have an atmospheric origin and are most likely produced by the microbial oxidation of NH4+ coming from clay minerals into NO2- and NO3-. These metabolic pathways also produce NO. Subsequent dark abiotic reactions lead to NO2 and HONO production. The snow cover is therefore not only an active photochemical reactor but also a biogeochemical reactor active in the cycling of nitrogen and it can affect atmospheric composition all year round.

Domine, F., S. Houdier, A. S. Taillandier, and W. R. Simpson (2010): **Acetaldehyde in the Alaskan subarctic snowpack**. Atmospheric Chemistry and Physics, 10(3), 919-929.

**Abstract:** Acetaldehyde is a reactive intermediate in hydrocarbon oxidation. It is both emitted and taken up by snowpacks and photochemical and physical processes are probably involved. Understanding the reactivity of acetaldehyde in snow and its processes of physical and chemical exchanges requires the knowledge of its incorporation mechanism in snow crystals. We have performed a season-long study of the evolution of acetaldehyde concentrations in the subarctic snowpack near Fairbanks (65 degrees N), central Alaska, which is subjected to a vigorous metamorphism due to persistent elevated temperature gradients in the snowpack, between 20 and 200 degrees C m(-1). The snowpack therefore almost entirely transforms into depth hoar. We have also analyzed acetaldehyde in a manipulated snowpack where temperature gradients were suppressed. Snow crystals there transformed much more slowly and their original shapes remained recognizable for months. The specific surface area of snow layers in both types of snowpacks was also measured. We deduce that acetaldehyde is not adsorbed onto the surface of snow crystals and that most of the acetaldehyde is probably not dissolved in the ice lattice of the snow crystals. We propose that most of the acetaldehyde measured is either trapped or dissolved within organic aerosol particles trapped in snow, or that acetaldehyde is formed by the hydrolysis of organic precursors contained in organic aerosols trapped in the snow, when the snow is melted for analysis. These precursors are probably aldehyde polymers formed within the aerosol particles by acid catalysis, but might also be biological molecules. In a laboratory experiment, acetaldehyde-din-hexyl acetal, representing a potential acetaldehyde precursor, was subjected to our analytical procedure and reacted to form acetaldehyde. This confirms our suggestion that acetaldehyde detected in snow could be produced during the melting of snow for analysis.
Domine, F., A. Cincinelli, E. Bonnaud, T. Martellini, and S. Picaud (2007) : **Adsorption of phenanthrene on natural snow**. Environmental Science & Technology, 41, 6033-6038.

**Abstract** : The snowpack is a reservoir for semivolatile organic compounds (SVOCs) and, in particular, for persistent organic pollutants (POPS), which are sequestered in winter and released to the atmosphere or hydrosphere in the spring. Modeling these processes usually assumes that SVOCs are incorporated into the snowpack by adsorption to snow surfaces, but this has never been proven because the specific surface area (SSA) of snow has never been measured together with snow composition. Here we expose natural snow to phenanthrene vapors (one of the more volatile POPs) and measure for the first time both the SSA and the chemical composition of the snow. The results are consistent with an adsorption equilibrium. The measured Henry's law constant is H-Phen(T) = 2.88 x 10(22) exp(-10660/T) Pa m(2) mol(-1), with Tin Kelvin. The adsorption enthalpy is Delta H-ads = -89 +/- 18 kJ mol(-1). We also perform molecular dynamics calculations of phenanthrene adsorption to ice and obtain Delta H-ads = -85 +/- 8 kJ mol(-1), close to the experimental value. Results are applied to the adsorption of phenanthrene to the Arctic and subarctic snowpacks. The subarctic snowpack, with a low snow area index (SAI = 1000), is a negligible reservoir of phenanthrene, but the colder Arctic snowpack, with SAI = 2500, sequesters most of the phenanthrene present in the (snow + boundary layer) system.

Savarino, J., J. Kaiser, S. Morin, D. M. Sigman, and M. H. Thiemens (2007), **Nitrogen and oxygen isotopic constraints on the origin of atmospheric nitrate in coastal Antarctica**, *Atmospheric Chemistry and Physics*, 7, 1925-1945.

Throughout the year 2001, aerosol sam-ples were collected continuously for 10 to 15
days at the French Antarctic Station Dumont d'Urville (DDU) (66°40'S, 140°01'E,
40 m above mean sea level). The nitrogen and oxygen isotopic ratios of particulate
nitrate at DDU exhibit seasonal variations that are among the most extreme observed
for nitrate on Earth. In association with concentration measurements, the isotope
ratios delineate four distinct periods, broadly consistent with previous studies on
Antarctic coastal areas. Based on the measured isotopic composition, known
atmospheric trans port patterns and the current understanding of kinetics and isotope
effects of relevant atmospheric chemical processes, we suggest that elevated
tropospheric nitrate levels during Period 3 are most likely the result of nitrate
sedimentation from polar stratospheric clouds (PSCs), whereas elevated nitrate levels
during Period 4 are likely to result from snow re-emission of nitrogen oxide species.
We are unable to attribute the source of the nitrate during periods 1 and 2 to local
production or long-range transport, but note that the oxygen isotopic composition is in
agreement with day and night time nitrate chemistry driven by the diurnal solar cycle.
A precise quantification is difficult, due to our insufficient knowledge of isotope
fractionation during the reactions leading to nitrate formation, among other reasons.

Morin, S., J. Savarino, N. Yan, M. M. Frey, J. Bottenheim, S. Bekki, and J. Martins (2008),
**Tracing the origin and fate of NOx in the Arctic atmosphere using stable isotopes**,
*Science*, 322, 730-732.

Atmospheric nitrogen oxides (NOx = NO + NO2) play a pivotal role in the cycling of reactive nitrogen (ultimately deposited as nitrate) and the oxidative capacity of the atmosphere. Combined measurements of nitrogen and oxygen stable isotope ratios of nitrate collected in the Arctic atmosphere were used to infer the origin and fate of NOx and nitrate on a seasonal basis. In spring, photochemically driven emissions of
reactive nitrogen from the snowpack into the atmosphere make local oxidation of NOx by bromine oxide the major contributor to the nitrate budget. The comprehensive isotopic composition of nitrate provides strong constraints on the relative importance of the key atmospheric oxidants in the present atmosphere, with the potential for extension into the past using ice cores.

Frey, M. M., J. Savarino, S. Morin, J. Erbland, and J. M. F. Martins (2009), **Photolysis imprint in the nitrate stable isotope signal in snow and atmosphere of East Antarctica and implications for reactive nitrogen cycling**, *Atmospheric Chemistry and Physics*, 9, 8681–8696.

The nitrogen (δ15N) and triple oxygen (δ17O and δ18O) isotopic composition of nitrate (NO3-) was measured year-round in the atmosphere and snow pits at Dome C, Antarctica (DC, 75.1° S, 123.3° E), and in surface snow on a transect between DC and the coast. Comparison to the isotopic signal in atmospheric NO3- shows that snow NO3 is significantly enriched in δ15N by >200‰ and depleted in δ18O by <40‰. Post-depositional fractionation in δ17O(NO3-) is small, potentially allowing reconstruction of past shifts in tropospheric oxidation pathways from ice cores. Assuming a Rayleigh-type process we find fractionation constants of 60±15‰, 8±2 and 1±1‰, for δ15N, δ18O and δ17O, respectively. A photolysis model yields an upper limit for the photolytic fractionation constant 15 of δ15N, consistent with lab and field measurements, and demon- strates a high sensitivity of 15Îµ to the incident actinic flux spectrum. The photolytic 15 is process-specific and therefore applies to any snow covered location. Previously published 15 values are not representative for conditions at the Earth surface, but apply only to the UV lamp used in the reported experiment (Blunier et al., 2005; Jacobi et al., 2006). Depletion of oxygen stable isotopes is attributed to photolysis followed by isotopic exchange with water and hydroxyl radicals. Conversely, 15N enrichment of the NO3-fraction in the snow implies 15N depletion of emissions. Indeed, δ15N in atmospheric NO3- shows a strong decrease from background levels (4±7‰) to 35‰ in spring ng followed by recovery during summer, consistent with significant snowpack emissions of reactive nitrogen. Field and lab evidence therefore suggest that photolysis is an important process driving fractionation and associated NO3- loss from snow. The δ17O signature confirms previous coastal measurements that the peak of at- mospheric NOâ''3 in spring is of stratospheric origin. After sunrise photolysis drives then redistribution of NO3- from the snowpack photic zone to the atmosphere and a snow surface skin layer, thereby concentrating NO3 at the surface. Little NO3- appears to be exported off the EAIS plateau, still snow emissions from as far as 600 km inland can contribute to the coastal NO3- budget.

Legrand, M., S. Preunkert, B. Jourdain, H. Gallée, F. Goutail, R. Weller, and J. Savarino (2009), **Year-round record of surface ozone at coastal (Dumont d'Urville) and inland (Concordia) sites in East Antarctica**, *Journal of Geophysical Research*, 114(D20), D20306,10.1029/2008jd011667.

Surface ozone is measured since 2004 at the coastal East Antarctic station of Dumont d'Urville (DDU) and since 2007 at the Concordia station located on the high East Antarctic plateau. Ozone levels at Concordia reach a maximum of 35 ppbv in July and a minimum of 21 ppbv in February. From November to January, sudden increases of the ozone level, up to 15–20 ppbbv above average, often take place. They are attributed to local photochemical ozone production as previously seen at the South Pole. The detailed examination of the diurnal ozone record in summer at Concordia
suggests a local photochemical ozone production of around 0.2 ppbv during the morning. The ozone record at DDU exhibits a maximum of 35 ppbv in July and a minimum of 18 ppbv in January. Mixing ratios at DDU are always higher than those at Neumayer (NM), another coastal Antarctic station. A noticeable difference in the ozone records at the two coastal sites lies in the larger ozone depletion events occurring from July to September at NM compared to DDU, likely due to stronger BrO episodes in relation with a larger sea ice coverage offshore that site. A second difference is the large day-to-day fluctuations which are observed from November to January at DDU but not at NM. That is attributed to a stronger impact at DDU than at NM of air masses coming from the Antarctic plateau. The consequences of such a high oxidizing property of the atmosphere over East Antarctica are discussed with regard to the dimethylsulfide (DMS) chemistry.

Larose, C., Dommergue, A., De Angelis, M., Cossa, D., Averty, B., Marusczak, N., Soumis, N., Schneider, D., Ferrari, C., 2010. **Springtime changes in snow chemistry lead to new insights into mercury methylation in the Arctic.** *Geochimica et Cosmochimica Acta* 74, 6263-6275.

Seasonal snow is an active media and an important climate factor that governs nutrient transfer in Arctic ecosystems. Since the snow stores and transforms nutrients and contaminants, it is of crucial importance to gain a better understanding of the dynamics of contaminant cycling within the snowpack and its subsequent release to catchments via meltwater. Over the course of a two-month field study in the spring of 2008, we collected snow and meltwater samples from a seasonal snowpack in Ny-Ålesund, Norway (78_560N, 11_520E), which were analyzed for major inorganic ions and some organic acids, as well as total, dissolved, bioavailable mercury (THg, DHg, BioHg, respectively) and monomethylmercury (MMHg) species. We observe a seasonal gradient for ion concentrations, with surface samples becoming less concentrated as the season progressed. A significant negative correlation between BioHg and MMHg was observed in the snowpack. MMHg was positively and significantly correlated to methanesulfonate concentrations. Based on these results, we propose a new model for aerobic methylation of mercury involving species in the dimethylsulfoniopropionate cycle.

Dommergue, A., Larose, C., Faïn, X., Clarisse, O., Foucher, D., Hintelmann, H., Schneider, D., Ferrari, C.P., 2010. **Deposition of mercury species in the Ny-Ålesund area (79°N) and their transfer during snowmelt.** *Environmental Science and Technology* 44, 901-907.

Arctic snowpacks are often considered as temporary reservoirs for atmospheric mercury (Hg) deposited during springtime deposition events (AMDEs). The fate of deposited species is of utmost importance because melt leads to the transfer of contaminants to snowmelt-fed ecosystems. Here, we examined the deposition, fate, and transfer of mercury species (total Hg (THg) and methylmercury (MeHg)) in an arctic environment from the beginning of mass deposition of Hg during AMDEs to the full melt of the snow. Following these events, important amounts of THg were deposited onto the snow surface with concentrations reaching 373 ng · L⁻¹ and estimated deposition fluxes of 200-2160 ng · m⁻². Most of the deposited Hg was reemitted to the atmosphere via photochemical reactions. However, a fraction remained stored in the snow and we estimated that the spring melt contributed to an input of 1.5-3.6 kg · year⁻¹ of THg to the fjord (i.e., 8-21% of the fjord's THg content). A monitoring of MeHg in snow using a new technique (DGT sensors) is also presented.
Dommergue, A., Bahlmann, E., Ebinghaus, R., Ferrari, C., Boutron, C., 2007. **Laboratory simulation of Hg° emissions from a snowpack. Analytical and Bioanalytical Chemistry** 388, 319-327.

Snow surfaces play an important role in the biogeochemical cycle of mercury in high-latitude regions. Snowpacks act both as sources and sinks for gaseous compounds. Surprisingly, the roles of each environmental parameter that can govern the air-surface exchange over snow are not well understood owing to the lack of systematic studies. A laboratory system called the laboratory flux measurement system was used to study the emission of gaseous elemental mercury from a natural snowpack under controlled conditions. The first results from three snowpacks originating from alpine, urban and polar areas are presented. Consistent with observations in the field, we were able to reproduce gaseous mercury emissions and showed that they are mainly driven by solar radiation and especially UV-B radiation. From these laboratory experiments, we derived kinetic constants which show that divalent mercury can have a short natural lifetime of about 4–6 h in snow.

V.Masson-Delmotte et al., **A review of Antarctic surface snow isotopic composition : observations, atmospheric circulation and isotopic modelling**, J. Climate, 21, 13, 3359-3387, 2008.

A database of surface Antarctic snow isotopic composition is constructed using available measurements, with an estimate of data quality and local variability. Although more than 1000 locations are documented, the spatial coverage remains uneven with a majority of sites located in specific areas of East Antarctica. The database is used to analyze the spatial variations in snow isotopic composition with respect to geographical characteristics (elevation, distance to the coast) and climatic features (temperature, accumulation) and with a focus on deuterium excess. The capacity of theoretical isotopic, regional, and general circulation atmospheric models (including “isotopic” models) to reproduce the observed features and assess the role of moisture advection in spatial deuterium excess fluctuations is analyzed.

### 1-3-2 – Other references without abstracts

Bock, J., and H.-W. Jacobi, **Development of a mechanism for nitrate photochemistry in snow**, J.Phys.Chem.A 114, 1790–1796, 2010.

F. Domine, M. Albert, T. Huthwelker, H.-W. Jacobi, A. A. Kokhanovsky, M. Lehning, G. Picard, and W. R. Simpson, **Snow physics as relevant to snow photochemistry**, *Atmos. Chem. Phys.*, 8, 171-208, 2008

Grannas, A.M., et al. **An overview of snow photochemistry: Evidence, mechanisms and impacts**, Atmos.Chem.Phys. 7, 4329-4373, 2007.

Castebrunet, H., P. Martinerie, C. Genthon and E. Cosme, **A three-dimensional model study of methanesulphonic acid to non sea salt sulphate ratio at mid and high-southern latitudes**. Atmos. Chem. Phys., 9, 9449-9469, 2009.

Fain, X., C. P. Ferrari, A. Dommergue, M. Albert, M. Battle, L. Arnaud, J.M. Barnola, W. Cairns, C. Barbante and C. Boutron, **Mercury in the snow and firn at Summit Station, Central Greenland, and implications for the study of past atmospheric mercury levels**. Atmos. Chem. Phys., 7, 18221-18268, 2007.
Fain, X., S. Grangeon, E. Bahlmann, J. Fritsche, D. Obrist, A. Dommergue, C. Ferrari, W. Cairns, R. Ebinghaus, C. Barbante, P. Cescon and C. Boutron, *Diurnal production of gaseous mercury in the alpine snowpack before snowmelt*. Journal Geophys. Res., 10.1029/2007JD008520, 112, 2007.

Fain, X., S. Grangeon, E. Bahlmann, Fritsche J., D. Obrist, C.P. Ferrari, W. Cairns, W. Ebinghaus, C. Barbante, P. Cescon and C. Boutron, *Diurnal production of Gaseous Mercury in the alpine snowpack before snowmelt*. Journal of Geophysical Research, 10.029/2007JD008520, 112, D21311, 2007.

U.Heikkilä, Beer, J., Jouzel, J., Feitchter, J., Kubik, P., 10Be measured in a GRIP snowpit and modelled using the ECHAM5-HAM general circulation model, Geophys. Res. Lett., 35, 5, L05817, 2008.

Wang Y.T, Hou S.G, Masson-Delmotte, V. and Jouzel J. *A new spatial distribution map of d18O in Antarctic surface snow*. Geophys. Res. Lett., 36, L06501, 2009.

Y.T.Wang, S.G.Hou, V.Masson-Delmotte and J.Jouzel, *A generalized additive model for the spatial distribution of stable isotopic composition in Antarctic surface snow*. Chemical Geology, 271, 3-4, 133-141, 2010.
**2-1 Main references with abstracts**

Wagnon, P., A. Linda, Y. Arnaud, R. Kumar, P. Sharma, C. Vincent, J. Pottakal, E. Berthier, A. Ramanathan, S.I; Hasnain & P. Chevallier, **Four years of mass balance of Chhota Shigri glacier (Himachal Pradesh, India), a new benchmark glacier in western Himalaya**, *J. Glaciol.*, 53(183), 603-610, 2007.

Little is known about the Himalayan glaciers although they are of particular interest in terms of future water supply, regional climate change and sea level rise. In 2002, a long-term monitoring program was started on Chhota Shigri glacier (32.2°N, 77.5°E; 15.7 km², 6263 to 4050 m a.s.l., 9 km long) located in Lahaul and Spiti valley, Himachal Pradesh, India. This glacier lies in the monsoon-arid transition zone (western Himalaya) which is alternatively influenced by Asian monsoon in summer and the mid-latitude westerlies in winter. Here, we present the results of 4 years of mass balance and surface velocities. Overall specific mass balances are mostly negative during the study period and vary from a minimum value of -1.4 m water equivalent (w.e.) in 2002-2003 and 2005-2006 (Equilibrium line altitude (ELA) at ~5180 m a.s.l.) to a maximum value of +0.1 m w.e. in 2004-2005 (ELA at 4855 m a.s.l.). Chhota Shigri glacier seems rather similar to mid-latitude glaciers with an ablation season limited to the summer months and a mean vertical gradient of mass balance in the ablation zone (uncovered part) of 0.7 m w.e. 100 m⁻¹, similar to those reported in the Alps. Mass balance is strongly dependent on debris cover, exposure and shading effect of surrounding steep slopes.

Vuille M., B. Francou, P. Wagnon, I. Juen, G. Kaser, B. Mark, R. Bradley, **Climate change and tropical Andean glaciers - past, present and future**, *Earth Science Review*, 89, 79-96, 2008.

Observations on glacier extent from Ecuador, Peru and Bolivia give a detailed and unequivocal account of rapid shrinkage of tropical Andean glaciers since the Little Ice Age (LIA). This retreat however, was not continuous but interrupted by several periods of stagnant or even advancing glaciers, most recently around the end of the 20^th^ century. New data from mass balance networks established on over a dozen glaciers allows comparison of the glacier behavior in the inner and outer tropics. It appears that glacier variations are quite coherent throughout the region, despite different sensitivities to climatic forcing such as temperature, precipitation, humidity etc. In parallel with the glacier retreat, climate in the tropical Andes has changed significantly over the past 50-60 years. Temperature in the Andes has increased by approximately 0.1°C/decade, with only two of the last 20 years being below the 1961-90 average. Precipitation has slightly increased in the second half of the 20^th^ century in the inner tropics and decreased in the outer tropics. The general pattern of moistening in the inner tropics and drying in the subtropical Andes is dynamically consistent with observed changes in the large-scale circulation, suggesting a strengthening of the tropical atmospheric circulation. Model projections of future climate change in the tropical Andes indicate a continued warming of the tropical troposphere throughout the 21^st^ century, with a temperature increase that is enhanced at higher elevations. By the end of the 21^st^ century, following the SRES A2 emission scenario, the tropical Andes may experience a massive warming on the order of 4.5°-5°C. Predicted changes in precipitation include an increase in precipitation during the
wet season and a decrease during the dry season, which would effectively enhance the seasonal hydrological cycle in the tropical Andes.

These observed and predicted changes in climate affect the tropical glacier energy balance through its sensitivity to changes in atmospheric humidity (which governs sublimation), precipitation (whose variability induces a positive feedback on albedo) and cloudiness (which controls the incoming long-wave radiation). In the inner tropics air temperature also significantly influences the energy balance, albeit not through the sensible heat flux, but indirectly through fluctuations in the rain-snow line and hence changes in albedo and net radiation receipts.

Given the projected changes in climate, based on different IPCC scenarios for 2050 and 2080, simulations with a tropical glacier-climate model indicate that glaciers will continue to retreat. Many smaller, low-lying glaciers are already completely out of equilibrium with current climate and will disappear within a few decades. But even in catchments where glaciers do not completely disappear, the change in streamflow seasonality, due to the reduction of the glacial buffer during the dry season, will significantly affect the water availability downstream. In the short-term, as glaciers retreat and lose mass, they add to a temporary increase in runoff to which downstream users will quickly adapt, thereby raising serious sustainability concerns.

Gilbert, A. P. Wagnon, C. Vincent, P. Ginot & M. Funk, 20th century temperature reconstitution in a high altitude tropical site from Illimani (6340 m a.s.l., Bolivia 16°39'S) englacial temperature, *J. Geophys. Res.*, 115, D10109, doi:10.1029/2009JD012961, 2010.

In June 1999, a deep (138.7-meter) ice core was extracted from the summit glacier of Illimani (Bolivia, 6340 m a.s.l., 16°39′S) and an englacial temperature profile was measured in the borehole. Using on-site and regional meteorological data as well as ice core stratigraphy, past surface temperatures were reconstructed with a heat flow model. The englacial temperature measurements exhibit a profile that is far from a steady state, reflecting an increasing atmospheric temperature over several years and non-stationary climatic conditions. Englacial temperature interpretation using air temperature data, borehole temperature inversion and melting rate quantification based on ice core density shows two warming phases from 1900 to 1960 (+0.5 ± 0.3 K starting approximately in 1920-1930) and from 1985 to 1999 (+0.6 ± 0.2 K), corresponding to a mean atmospheric temperature rise of 1.1 ± 0.2 K over the 20th century. According to various climate change scenarios, the future evolution of englacial temperatures was simulated to estimate when and under what conditions this high-elevation site on the Illimani summit glacier could become temperate in the future. Results show that this glacier might remain cold for more than 90 years in the case of a +2 K rise over the 21st century, but could become temperate in the first 20 meters depth between 2050 and 2060 if warming reaches +5 K.

Berthier, E., R. Le Bris, L. Mabileau, L. Testut, and F. Rémy (2009), *Ice wastage on the Kerguelen Islands (49S, 69E) between 1963 and 2006*, *Journal of Geophysical Research*, 114, F03005, doi: 10.1029/2008JF001192.

We observed the wastage of ice masses on the Kerguelen Islands (Indian Ocean, 49°S, 69°E) using historical information and recent satellite data. Overall, the total ice-covered area on the islands declined from 703 to 552 km² between 1963 and 2001, a reduction of 21%. The area of Cook ice cap (the main ice body) decreased asymmetrically from 501 to 403 km². West-flowing glaciers lost 11% of their area while east-flowing glaciers lost 28%. After 1991, the retreat rate accelerated from 1.9
km²/yr (1963-1991) to 3.8 km²/yr (1991-2003). Between 1963 and 2000, the ice volume loss was 25-30 km³, equivalent to an area-average ice thinning rate of 1.4-1.7 m/yr. The glacial retreat took place in the climatic context of a relatively low level of precipitation (compared to the 1950s) and a ~1°C warming that occurred between 1964 and 1982. The acceleration of the ice losses since, at least, the 1990s indicates that the state of the ice bodies on the Kerguelen Islands is still far from balanced. Together with other studies in Patagonia, South Georgia and Heard Island, our analysis is consistent with a pattern of strong and accelerated wastage of ice masses influenced by the Southern Ocean.

Berthier, E., E. Schiefer, G.K.C. Clarke, B. Menounos, and F. Rémy (2010), **Contribution of Alaskan glaciers to sea level rise derived from satellite imagery**, Nature Geoscience, 3(2), 92-95.

Over the last 50 years, retreating glaciers and ice caps (GIC) contributed 0.5 mm/yr to sea level rise (SLR), and one third is believed to originate from ice masses bordering the Gulf of Alaska. However, these estimates of ice wastage in Alaska are based on methods that measure a limited number of glaciers and extrapolate the results to estimate ice loss for the many thousands of others. How these methods capture the complex pattern of decadal elevation changes at the scale of individual glacier and mountain range is unclear. Here, combining a comprehensive glacier inventory with elevation changes derived from sequential digital elevation models (DEMs), we found that, between 1962 and 2006, Alaskan glaciers lost 41.9±8.6 km³/yr water equivalent (w.e.) and contributed 0.12±0.02 mm/yr to SLR. Our ice loss is 34% lower than previous estimates. Reasons for our lower values include the higher spatial resolution of our glacier inventory and the reduction of ice thinning under debris and at the glacier margins which were not resolved in earlier work. Estimates of mass loss from GIC in other mountain regions could be subject to similar revisions.

Sicart, J. E., R. Hock, P. Ribstein and J. P. Chazarin (2010), **Sky long-wave radiation on tropical Andean glaciers: parameterization and sensitivity to atmospheric variables**, Journal of Glaciology, 56 (199), 854–860.

Abstract. In mountain environments, long-wave radiation provides large amounts of melt energy for high-albedo snow surfaces and can dominate in the energy balance of snow or glacier surfaces under cloudy skies. This study examines the atmospheric controls of sky long-wave radiation at Zongo Glacier, Bolivia (16°15'S, 5060 m asl) over an entire year to derive a parameterization suitable for melt studies. Tropical glaciers are characterized by a pronounced seasonality of long-wave radiation due to cloud emissions during the wet season that strongly enhance the small emissivity of the thin and dry clear-sky atmosphere of very high altitudes. Clear-sky radiation is well simulated as a function of air temperature and humidity but changes in humidity atmospheric profiles from daytime to nighttime entail different optimized coefficients for hourly and daily data. Cloud emission, which enhances clear-sky emissivity by up to 60% with an average of 20%, is estimated using daily atmospheric transmissivity for solar radiation. Partial correlations show that in high mountains cloud emissions control the variations of long-wave radiation, far more than clear-sky emissivity and temperature of the emitting low atmosphere. An independent test on Antizana Glacier in the humid tropics of Ecuador (0°28'S, 4860 m asl) indicates that the parameterization is robust for the Central Andes.
Sicart J. E., R. Hock, D. Six (2008), **Glacier melt, air temperature, and energy balance in different climates: The Bolivian Tropics, the French Alps, and northern Sweden,** Journal of Geophysical Research, 113, D24113, doi:10.1029/2008JD010406.

*Abstract.* This study investigates the physical basis of temperature-index models for three glaciers in contrasting climates: Zongo (16°S, 5050 m, Bolivian tropics), St Sorlin (45°N, 2760 m, French Alps), and Storglaciären (67°N, 1370 m, northern Sweden). The daily energy fluxes were computed during melt seasons and correlated with each other and with air temperature on and outside the glacier. The relative contribution of each flux to the correlations between temperature and melt energy was assessed. At Zongo, net short-wave radiation controls the variability of the energy balance and is poorly correlated to temperature. On tropical glaciers, temperature remains low and varies little, melt energy is poorly correlated to temperature, and degree-day models are not appropriate to simulate daily melting. At the yearly scale, the temperature is better correlated to the mass balance because it integrates the ablation and the accumulation processes over a long time period. At Sorlin, the turbulent sensible heat flux is greater because of higher temperatures, but melt variability is still controlled by short-wave radiation. Temperature correlates well with melt energy mainly through short-wave radiation, probably due to diurnal advection of warm air from the valley. At Storglaciären, high correlations between temperature and melt energy result from substantial variability and good correlations with temperature of the turbulent fluxes of sensible and latent heat, which both supply energy to the glacier. In the three climates, long-wave irradiance is the main source of energy, but its variability is small and poorly correlated to the temperature mainly because of cloud emissions

Pomeroy, J. W., A. Rowlands, J. Hardy, T. Link, D. Marks, R. Essery, J. E. Sicart, and C. R. Ellis (2008), **Spatial Variability of Shortwave Irradiance for Snowmelt in Forests**, Journal of Hydrometeorology, 9(6), 1482–1490, doi: 10.1175/2008JHM86.

*Abstract.* The spatial variation of melt energy can influence snow cover depletion rates and in turn be influenced by the spatial variability of shortwave irradiance to snow. The spatial variability of shortwave irradiance during melt under uniform and discontinuous evergreen canopies at a U. S. Rocky Mountains site was measured, analyzed, and then compared to observations from mountain and boreal forests in Canada. All observations used arrays of pyranometers randomly spaced under evergreen canopies of varying structure and latitude. The spatial variability of irradiance for both overcast and clear conditions declined dramatically, as the sample averaging interval increased from minutes to 1 day. At daily averaging intervals, there was little influence of cloudiness on the variability of subcanopy irradiance; instead, it was dominated by stand structure. The spatial variability of irradiance on daily intervals was higher for the discontinuous canopies, but it did not scale reliably with canopy sky view. The spatial variation in irradiance resulted in a coefficient of variation of melt energy of 0.23 for the set of U. S. and Canadian stands. This variability in melt energy smoothed the snow-covered area depletion curve in a distributed melt simulation, thereby lengthening the duration of melt by 20%. This is consistent with observed natural snow cover depletion curves and shows that variations in melt energy and snow accumulation can influence snow-covered area depletion under forest canopies.

Sicart, J. E., and Y. Arnaud (2007), **Preliminary spectral characterization of snow in a high altitude tropical glacier and potential effects of impurities in snow on albedo of tropical glaciers**, Hydrological Processes, 21(26), 3642-3644.
Abstract. This paper presents some preliminary measurements of snow spectral reflectance on the tropical Bolivian Zongo glacier. Measurements show a correct agreement with theoretical spectral albedo of pure snow in the near infrared region, but lower values in the visible region (by 10-20%) probably due to aerosols contained in snow. Impurity contents ranged from 10 to 100 ppmw in one-week-old snow collected from the Zongo glacier, but measurements are scarce. Large amounts of snowfall partly compensate the proximity of dust sources in mid-latitude glaciers, whereas on outer-tropical glaciers precipitations are not abundant and are very seasonal, and sources of aerosols are proximate.

Sicart, J. E., P. Ribstein, B. Francou, B. Pouyaud, and T. Condom (2007), **Glacier mass balance of tropical Zongo glacier, Bolivia, comparing hydrological and glaciological methods**, *Global Planetary Change*, 59(1), 27-36.

Abstract. A glaciological program has been undertaken since 1991 on Zongo glacier in Bolivia (6000-4850 m asl, 2.4 km(2), 16 degrees S). This program involves mass balance measurements, hydrological studies and energy balance investigations. On outer-tropical glaciers, melting and snow accumulation are both maximum in the wet season (austral summer), whereas the dry season (winter) is a period of low ablation. Errors on each term of the glaciological (stakes, snow-pits and integration method of the measurements) and hydrological (precipitation, discharge and runoff coefficient of free ice areas) methods are investigated to estimate the overall accuracy of the mass balance measurements. The hydrological budget is less than the glaciological one (mean difference: 60 cm w.e. per year), but both methods reproduce similar inter-annual variations. Errors in assessment of evaporation or water storage inside the glacier cannot explain the discrepancy. Errors using the glaciological method are large (around +/- 40 cm w.e. per year), but no bias can explain the departure from the hydrological balance. Errors on discharge measurements are small and the uncertainty on the runoff coefficient has a minor effect on the mass balance. We concluded that hydrological budgets are too low due to the catch deficiency of rain gauges and absence of precipitation measurements at high altitudes, emphasizing the difficulty to assess snowfall distribution in high mountainous basins.

Berthier, E., Y. Arnaud, S. Ahmad, R. Kumar, P. Wagnon, and P. Chevallier (2007), **Remote sensing estimates of glacier mass balances in the Himachal Pradesh (Western Himalaya, India)**. *Remote Sensing of the Environment*, 108(3), 327-338.

Although they correspond to an important fraction of the total area of mountain glaciers (33,000 km2 out of 546,000 km2), Himalayan glaciers and their mass balance are poorly sampled. For example, between 1977 and 1999, the average area surveyed each year on the field was 6.8 km2 only. No direct mass balance measurement is available after 1999. To contribute to fill this gap, we use remote sensing data to monitor glacier elevation changes and mass balances in the Spiti/Lahaul region (32.2°N, 77.6°E, Himachal Pradesh, Western Himalaya, India). Our measurements are obtained by comparing a 2004 digital elevation model (DEM) to the 2000 SRTM (Shuttle Radar Topographic Mission) topography. The 2004 DEM is derived from two SPOT5 satellite optical images without any ground control points. This is achieved thanks to the good onboard geolocation of SPOT5 scenes and using SRTM elevations as a reference on the ice free zones. Before comparison on glaciers, the two DEMs are analyzed on the stable areas surrounding the glaciers where no elevation change is expected. Two different biases are detected. A long wavelength bias affects the SPOT5 DEM and is correlated to an anomaly in the roll of the SPOT5 satellite. A bias is also
observed as a function of altitude and is attributed to the SRTM dataset. Both biases
are modeled and removed to permit unbiased comparison of the two DEM on the 915
km2 ice-covered area digitized from an ASTER image. On most glaciers, a clear
thinning is measured at low elevations, even on debris-covered tongues. Between 1999
and 2004, we obtain an overall specific mass balance of –0.7 to –0.85 m/a (water
equivalent) depending on the density we use for the lost (or gained) material in the
accumulation zone. This rate of ice loss is twice higher than the long-term (1977 to
1999) mass balance record for Himalaya indicating an increase in the pace of glacier
wastage. To assess whether these ice losses are size-dependant, all glaciers were
classified into three samples according to their areal extent. All three samples show
ice loss, the loss being higher for glaciers larger than 30 km2. In the case of the
benchmark Chhota Shigri glacier, a good agreement is found between our satellite
observations and the mass balances measured on the field during hydrological years
2002–2003 and 2003–2004. Future studies using a similar methodology could
determine whether similar ice losses have occurred in other parts of the Himalaya and
may allow evaluation of the contribution of this mountain range to ongoing sea level
rise.

Caballero, Y., P. Chevallier, A. Boone, J. Noilhan, and F. Habets (2007), **Calibration of the Interaction Soil Biosphere Atmosphere land-surface scheme on a small tropical high-mountain basin (Cordillera Real, Bolivia)**, *Wat.Resour.Res.*, **43**(W07423).

In a continuing effort to test the behaviour of Meteo France's land-surface scheme, ISBA, under a wide range of hydro-meteorological conditions, the scheme was applied to a small tropical high mountain river basin of the Cordillera Real in Bolivia. The surface scheme simulates the key hydrological processes, such as evaporation, infiltration, surface runoff, and snow and soil ice freeze-thaw processes, which are essential for accurately simulating the hydrological behaviour of the river basin in this type of location. The 12.5 km² nonglacierized sub-basin has been divided into homogeneous surface units with irregular shapes, based on their elevation and soil surface characteristics. The ISBA scheme was applied to each unit and the water fluxes were transferred from one unit to another using a system dynamics modelling approach. The method was applied step by step, improving its efficiency based on several hypotheses. This special application of the ISBA scheme, combining the high mountain conditions and the tropical seasonality is discussed.

Lopez, P., P. Sirguey, Y. Arnaud, B. Pouyaud, and P. Chevallier (2008), **Snow cover monitoring of Northern Patagonia Icefield using MODIS satellite images (2000-2006)**, *Global & Planetary Change*, **61**, 103-116.

The snow cover of the Northern Patagonia Icefield (NPI) was monitored after applying the Normalized Difference Snow Index (NDSI) and the Red/NIR band ratio to 134 Moderate Resolution Imaging Spectroradiometer (MODIS) images captured between 2000 and 2006. The final results show that the snow cover extent of the NPI fluctuates a lot in winter, in addition to its seasonal behaviour. The minimum snow cover extent of the period (3600 km2) was observed in March 2000 and the maximum (11,623 km2) in August 2001. We found that temperature accounts for approximately 76% of the variation of the snow cover extent over the entire icefield. We also show two different regimes of winter snow cover fluctuations corresponding to the eastern and the western sides of the icefield. The seasonality of the snow cover on the western side was determined by temperature rather than precipitation, while on the east side the seasonality of the snow cover was influenced by the seasonal behaviour of both
temperature and precipitation. This difference can be explained by the two distinct climates: coastal and continental. The fluctuations in the winter snow cover extent were more pronounced and less controlled by temperature on the western side than on the eastern side of the icefield. Snow cover extent was correlated with temperature R2 = 0.75 and R2 = 0.74 for the western and eastern sides, respectively. Since limited meteorological data are available in this region, our investigation confirmed that the change in snow cover is an interesting climatic indicator over the NPI providing important insights in mass balance comprehension. Since snow and ice were distinguished snow cover fluctuations can be associated to fluctuations in the snow accumulation area of the NPI. In addition, days with minimum snow covers of summer season can be associated to the period in which Equilibrium Line Altitude (ELA) is the highest.

Lopez, P., P. Chevallier, V. Favier, B. Pouyaud, F. Ordenes, and J. Oerlemans (2010), A **regional view of fluctuations in glacier length in Southern South America**, *Global & Planetary Change*, 71(1-2), 85-108.

Fluctuations in the length of 72 glaciers in the Northern and Southern Patagonia Icefield (NPI and SPI, respectively) and the Cordillera Darwin Icefield (CDI) were estimated between 1945 and 2005. The information obtained from historical maps based on 1945 aerial photographs was compared to ASTER and Landsat satellite images and to information found in the literature. The majority of glaciers have retreated considerably, with maximum values of 12.2 km for Marinelli Glacier in the CDI, 11.6 km for O'Higgins Glacier in the SPI and 5.7 km for San Rafael Glacier in the NPI. Among the 20 glaciers that have retreated the most relative to their size, small (less than 50 km²) and medium (between 50 and 200 km²) glaciers are the most affected. However, no direct relation between glacier retreat and size was found for the 72 glaciers studied. The highest percentage retreat in the CDI was by the CDI-03 Glacier (37.9%) and Marinelli Glacier (37.6%). In the SPI, relative retreats were heterogeneous and fluctuated between 27.2% (Amelia Glacier) and 0.4% (Viedma Glacier). In the NPI, relative retreat was very high for Strindberg and Cachet glaciers (35.9% and 27.6%, respectively) but for the remaining glaciers in this icefield it ranged between 11.8% (Piscis Glacier) and 3.6% (San Quintín Glacier). In addition to surface area, the surface slope (calculated on the basis of the DEM SRTM) was also related to the relative retreat and no straightforward relation was found. From a global point of view, we suggest that glacier retreat in the region is controlled firstly by atmospheric warming, as it has been reported in this area. Besides the general increase in temperature observed, no signal of a geographical pattern for the fluctuations in glacier length was found. Consequently, glaciers appear to initially react to local conditions most probably induced by their exposition, geometry and hypsometry. The heterogeneity of rates of retreat suggests that differences in basin geometry, glacier dynamics and response time are key features to explain fluctuations of each glacier.

Suarez, W., P. Chevallier, B. Pouyaud, and P. Lopez (2008), Modelling the water balance in the glacierized Parón Lake basin (White Cordillera, Peru), *Hydrological Sciences Journal*, 53(1), 266-277.

The White Cordillera (northern Peru), with a glacial surface of 631 km², is the largest glacierized mountain range in the Tropics. Due to the lack of physical data from most of its sub-basins, it is difficult to build a physical model to estimate the water resource flowing from the glaciers at the present time and a fortiori for the future. The most
recent GCM simulations indicate a significant increase in the temperature and an
accelerated shrinking of the glaciers. Consequently, we sought a model that would be
based on the data available within instrumented sub-basins. A theoretical/conceptual
water model makes it possible to quantify the local glacier contribution, which could
then be applied to the other non-instrumented subbasins. A total of 43.6% of Parón
Lake's instrumented sub-basin area (47.4 km²) corresponds to glacial surfaces.
Within this sub-basin, a smaller watershed (8.8 km²), called Artesón, with 72.9%
glacierized area, has been accurately observed over a 5-year hydrological period
(September 2000–August 2005). This information allowed us to calibrate the model
over the Artesón sub-basin. The parameters obtained were applied to the entire Parón
basin using the same modelling approach.

Trouvé, E. et al., 2007, **Combining Airborne Photographs and Spaceborne SAR Data to Monitor Temperate Glaciers: Potentials and Limits** IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING, VOL. 45, NO. 4, APRIL 2007

*Abstract*—Monitoring temperate glacier activity has become more and more
necessary for economical and security reasons and as an indicator of the local effects
of global climate change. Remote sensing data provide useful information on such
complex geophysical objects, but they require specific processing techniques to cope
with the difficult context of moving and changing features in high-relief areas. This
paper presents the first results of a project involving four laboratories developing and
combining specific methods to extract information from optical and synthetic aperture
radar (SAR) data. Two different information sources are processed, namely: 1)
airborne photography and 2) spaceborne C-band SAR interferometry. The difficulties
and limitations of their processing in the context of Alpine glaciers are discussed and
illustrated on two glaciers located in the Mont-Blanc area. The results obtained by
aerial triangulation techniques provide digital terrain models with an accuracy that is
better than 30 cm, which is compatible with the computation of volume balance and
useful for precise georeferencing and slope measurement updating. The results
obtained by SAR differential interferometry using European Remote Sensing Satellite
images show that it is possible to measure temperate glacier surface velocity fields
from October to April in one-day interferograms with approximately 20-m ground
sampling. This allows to derive ice surface strain rate fields required to model the
glacier flow. These different measurements are complementary to results obtained
during the summer from satellite optical data and ground measurements that are
available only in few accessible points.

Pétillot Ivan, Emmanuel Trouvé, Philippe Bolon, Andreea Julea, Yajing Yan, Michel Gay, and Jean-Michel Vanpe. Radar-Coding and Geocoding Lookup Tables for the Fusion of GIS and SAR Data in Mountain Areas IEEE GEOSCIENCE AND REMOTE SENSING LETTERS, VOL. 7, NO. 2, APRIL 2010

*Abstract*—Synthetic aperture radar (SAR) image orthorectification induces an important alteration of information due to the side-looking geometry of SAR acquisition. In high-relief areas, the difficulty is increased by the foldover effect: The images acquired with low incidence angles cannot be registered by a bijective transformation like polynomial transformations, as usually proposed by conventional software. In this letter, a simple and efficient method, fitted to geocoded data and SAR images, is introduced to propose a generic coregistration tool that takes SAR geometry into account without requiring the exact sensor model, specific parameters, and precise navigation data. This method is based on a simulated SAR image and on the
computation of lookup tables (LUTs) that represent the coordinate transform from one geometry to the other. Results are presented on a high-relief area in the Alps, where satellite and airborne SAR images are used for glacier evolution monitoring. A comparison to other sensor-independent approaches has been performed, showing that the proposed approach performs better in mountain areas. The resulting LUTs allow merging SAR data with the georeferenced data, either in ground geometry by orthorectifying the SAR information or in radar geometry by the inverse transformation, namely, radar-coding data from a geographic information system, to improve the analysis of SAR images and the result interpretation.

Rabatel, A., V. Jomelli, B. Francou, P. Naveau, D. Grancher. 2008. **The Little Ice Age in the tropical Andes of Bolivia (16°S) and its implication for a climate reconstruction.**

*Quaternary Research*, 70, 198-212, doi: 10.1016/j.yqres.2008.02.012.

**Abstract:** Dating moraines by lichenometry enabled us to reconstruct glacier recession in the Bolivian Andes since the Little Ice Age maximum. On the 15 proglacial margins studied, we identified a system of ten principal moraines that marks the successive positions of glaciers over the last four centuries. Moraines were dated by performing statistical analysis of lichen measurements based on the extreme values theory. Like glaciers in many mid-latitude mountain areas, Bolivian glaciers reached their maximal extent during the second half of the 17th century. This glacier maximum coincides with the Maunder minimum of solar irradiance. By reconstructing the equilibrium-line altitude and changes in mass-balance, we think the glacier maximum may be due to a 20 to 30% increase in precipitation and a 1.1 to 1.2 °C decrease in temperature compared with present conditions. In the early 18th century, glaciers started to retreat at varying rates until the late 19th to early 20th century; this trend was generally associated with decreasing accumulation rates. By contrast, glacier recession in the 20th century was mainly the consequence of an increase in temperature and humidity. These results are consistent with observations made in the study region based on other proxies.

Rabatel, A., J.-P. Dedieu, E. Thibert, A. Letreguilly, C. Vincent. 2008. **Twenty-five years of equilibrium-line altitude and mass balance reconstruction on the Glacier Blanc, French Alps (1981-2005), using remote-sensing method and meteorological data.** *Journal of Glaciology*, 54 (185), 307-314.

**ABSTRACT.** Annual equilibrium-line altitude (ELA) and surface mass balance of Glacier Blanc, Ecrins region, French Alps, were reconstructed from a 25 year time series of satellite images (1981–2005). The remote-sensing method used was based on identification of the snowline, which is easy to discern on optical satellite images taken at the end of the ablation season. In addition, surface mass balances at the ELA were reconstructed for the same period using meteorological data from three nearby weather stations. A comparison of the two types of series reveals a correlation of $r > 0.67$ at the 0.01 level of significance. Furthermore, the surface mass balances obtained from remote-sensing data are consistent with those obtained from field measurements on five other French glaciers ($r \approx 0.76, p < 0.01$). Also consistent for Glacier Blanc is the total mass loss (10.8mw.e.) over the studied period. However, the surface mass balances obtained with the remote-sensing method show lower interannual variability. Given that the remote-sensing method is based on changes in the ELA, this difference probably results from the lower sensitivity of the surface mass balance to climate parameters at the ELA.
## 2-2 – Other references without abstracts

Lejeune, Y., P. Wagnon, L. Bouilloud, P. Chevallier, P. Etchevers, E. Martin, J.E. Sicart, F. Habets, **Melting of snow cover in a tropical mountain environment: processes and melting**, *J. Hydrometeorol.*, **8**, 922-937, Doi: 10.1175/JHM590.1, 2007.

Blard, P.H., J. Lavé, R. Pik, P. Wagnon & D. Bourlès, **Persistence of full glacial conditions in the central Pacific until 15,000 years ago**, *Nature*, **449**, doi:10.1038/nature06142, 2007.

Favier, V., A. Coudrain, E. Cadier, B. Francou, E. Ayabacha, L. Maisinsho, E. Praderio, M. Villacis, P. Wagnon, **Evidences of underground circulations on Antizana ice covered volcano**, *Ecuador, Hydrol. Sci.J.*, **53**(1), 278-291, 2008.

Soruco, A., C. Vincent, B. Francou, P. Ribstein, T. Berger, J.E. Sicart, P. Wagnon, Y. Arnaud, V. Favier & Y. Lejeune, **Mass balance of Glaciar Zongo, Bolivia, between 1956 and 2006, using glaciological, hydrological and geodetic methods**, *Ann. Glaciol.*, **50**, 1-8, 2009.

Winkler, M., I. Juen, T. Mölg, P. Wagnon, J. Gómez, and G. Kaser, **Measured and modelled sublimation on the tropical Glaciar Artesonraju, Perú, The Cryosphere**, *3*, 21-30, 2009.

Six, D., Wagnon, P., Sicart, J.E. & Vincent C., **Meteorological controls on snow and ice ablation for two contrasting months on Glacier de Saint-Sorlin, France**, *Ann. Glaciol.*, **50**(50), 66-72, 2009.

Gascoin, S., C. Kinnard, R. Ponce, S. Lhermitte, S. MacDonell, A. Rabatel. 2010. **Glacier contribution to streamflow in two headwaters of the Huasco River, Dry Andes of Chile. The Cryosphere Discussion**. 4, 2373-2413, doi:10.5194/tcd-4-2373-2010.

Rabatel, A., H. Castebrunet, V. Favier, L. Nicholson, C. Kinnard. 2010. **Glacier changes in the Pascua-Lama region, Chilean Andes (29°S): recent mass-balance and 50-year surface-area variations. The Cryosphere Discussion**, 4, 2307-2336, doi:10.5194/tcd-4-2307-2010.

Nicholson, L., J. Marín, D. Lopez, A. Rabatel, F. Bown, A. Rivera. 2009. **Glacier inventory of the upper Huasco valley: glacier characteristics, recent change and comparison to the upper Aconcagua valley**, Chile. *Annals of Glaciology*, **53**, 111-118

Jomelli, V., V. Favier, A. Rabatel, D. Brunstein, G. Hoffmann, B. Francou. 2009. **Fluctuations of glaciers in the tropical Andes over the last millennium and paleoclimatic implications: a review. Palaeogeography, Palaeoclimatology, Palaeoecology**, **281**, 269-282. doi:10.1016/j.palaeo.2008.10.033.

Favier, V., M. Falvey, A. Rabatel, E. Praderio, D. Lopez. 2009. **Interpreting discrepancies between discharge and precipitation 1 n in high altitude 2 area of Chile's Norte Chico region (26°S-32°S). Water Resources Research**, 45, W02424, doi:10.1029/2008WR006802.

Vincent, C., A. Soruco, D. Six and E. Le Meur, **Glacier thickening and decay analysis from fifty years of glaciological observations performed on Argentière glacier, Mont-Blanc area, France. Annals of glaciology**, **50**, 73-79, 2009.

Le Meur, E., M. Gerbaux, M. Schäfer and C. Vincent, **Disappearance of an Alpine glacier over the 21st Century simulated from modeling its future surface mass balance. Earth Planet. Sci. Lett.**, 10.1016/j.epsl.2007.07.022, (261) 367-374, 2007.

Schaefer, M. and E. Le Meur, **Improvements on a 2D-SIA ice flow model ; application to the Saint Sorlin glacier, France,** *Journal of Glaciology*, **53**, (183) 713-722, 2007.
Vincent, C., E. Le Meur, D. Six, M. Funk, M. Hoelzle and S. Preunkert, Very high-elevation Mont Blanc glaciated areas not affected by the 20th Century climate change. *Journal of Geophysical research*, **112**, (D9) D09120, 2007.

Vincent, C., E. Le Meur, D. Six, P. Possenti, E. Lefebvre and M. Funk, Climate warming revealed by englacial temperatures at Col du Dôme (4250 m, Mont Blanc area). *Geophys. Res. Lett.*, 10.1029/2007GL029933, **34**, L16502, 2007.

Vincent, C., S. Auclair and E. LeMeur, Outburst flood hazard for glacier-dammed Rochemelon lake (France), 56. *Journal of Glaciology*, 56, (195) 91-100, 2010.

Vincent, C., S. Garambois, E. Thibert, E. Lefebvre, E. LeMeur and D. Six, Origin of the outburst flood from Tête Rousse glacier in 1892 (Mont-Blanc area, France). *Journal of Glaciology*, 56, (198) 688-698, 2010.
**3-1- Main references with abstracts**

Girard, L., S. Bouillon, J. Weiss, D. Amitrano, T. Fichefet, V. Legat, **A new modelling framework for sea ice ice mechanics based on elasto-brittle rheology**, *Annals Glaciol.*, 52(57), 123-132, 2011

*We present a new modeling framework for sea-ice mechanics based on elasto-brittle (EB) behavior. The EB framework considers sea ice as a continuous elastic plate encountering progressive damage, simulating the opening of cracks and leads. As a result of long-range elastic interactions, the stress relaxation following a damage event can induce an avalanche of damage. Damage propagates in narrow linear features, resulting in a very heterogeneous strain field. Idealized simulations of the Arctic sea-ice cover are analyzed in terms of ice strain rates and contrasted to observations and simulations performed with the classical viscous-plastic (VP) rheology. The statistical and scaling properties of ice strain rates are used as the evaluation metric. We show that EB simulations give a good representation of the shear faulting mechanism that accommodates most sea-ice deformation. The distributions of strain rates and the scaling laws of ice deformation are well captured by the EB framework, which is not the case for VP simulations. These results suggest that the properties of ice deformation emerge from elasto-brittle ice-mechanical behavior and motivate the implementation of the EB framework in a global sea-ice model.*

Rampal, P., Weiss, J. and Marsan, D., **Positive trend in the mean speed and deformation rate of Arctic sea ice, 1979-2007**, *J. Geophys. Res.*, 114, C05013, 2009

*Using buoy data from the International Arctic buoy Program, we found that the sea ice mean speed has substantially increased over the last 29 years (+17% per decade for winter; +8.5% for summer). A strong seasonal dependence of the mean speed is also revealed, with a maximum in October and a minimum in April. The sea ice mean strain rate also increased significantly over the period (+51% per decade for winter; +52% for summer). We check that these increases in both sea ice mean speed and deformation rate are unlikely a consequence of a stronger atmospheric forcing. Instead, they suggest that sea ice kinematics plays a fundamental role in the albedo feedback loop and sea ice decline: increasing deformation means stronger fracturing, hence more lead opening and therefore a decreasing albedo. This accelerates sea ice thinning in summer and delays refreezing in early winter, therefore decreasing the mechanical strength of the cover and allowing even more fracturing and larger drifting speed and deformation, and possibly a faster export of sea ice through the Fram Strait. The September minimum sea ice extent of 2007 might be a good illustration of this interplay between sea ice deformation and sea ice shrinking, as we found that for both winter 2007 and summer 2007, exceptionally large deformation rates affected the Arctic sea ice cover.*

Weiss, J., Schulson, E.M., Stern, H.L., **Sea ice rheology from in-situ, satellite and laboratory observations: Fracture and friction**, *Earth Planet. Sci. Lett.*, 255, 1-8, 2007

*On the basis of an analysis of in-situ ice stresses and of satellite-derived ice strain-rates, as well as of a comparison between field and laboratory behaviour, we describe*
an alternative viewpoint for modelling sea ice deformation during winter. We propose that fracture and frictional sliding govern inelastic deformation over all spatial and temporal scales, even under small stresses. Consequently, winter and/or perennial sea ice does not behave as a viscous material, even at large scales, the normal flow rule is not obeyed (as observed during laboratory tests on sea ice samples harvested from the field), and stresses are highly intermittent and poorly correlated spatially.

Pierre Mathiot, Bernard Barnier, Hubert Gallée, Jean Marc Molines, Julien Le Sommer, Mélanie Juza and Thierry Penduff, **Introducing katabatic winds in global ERA40 fields to simulate their impacts on the Southern Ocean and sea-ice**, OCEAN MODELLING

Volume: 35 Issue: 3 Pages: 146-160, doi:10.1016/j.ocemod.2010.07.001

A medium resolution (10–20 km around Antarctica) global ocean/sea-ice model is used to evaluate the impact of katabatic winds on sea-ice and hydrography. A correction is developed to compensate for the drastic underestimation of these katabatic winds in the ERA40 reanalysis. This correction derives from a comparison over 1980–1989 between wind stress in ERA40 and those downscaled from ERA40 by the MAR regional atmospheric model. The representation in MAR of the continental orography surrounding the ocean, like the Transantarctic Mountains, and a specific parameterisation of roughness length in the planetary boundary layer yield a major improvement in the representation of katabatic winds along the coast of Antarctica. Wind stress directions at the first ocean point are remarkably similar in ERA40 and MAR, but MAR wind stress amplitudes are much greater. From this comparison, a scale factor constant in time (i.e. no seasonal variation) but spatially varying (decreasing off-shore over a distance of about 150 km) is created for the meridional and zonal wind stress components and adapted to the wind vector. The correction thus consists of a local amplification of the amplitude of the 6-hourly ERA40 wind vector components at ocean points near the coast. The impact of katabatic wind correction is investigated in 40-year long twin simulations of a global ocean/sea-ice model. The wind stress over polynyas is increased by a factor of 2, and amplitudes of sensible and latent air–sea heat exchanges are increased by 28% and 18%, respectively. Sea-ice thickness and ice-fraction near the coast of Antarctica show a marked decrease. The amplified katabatic winds also increase the extent of coastal polynyas by 24% (i.e. the total polynya area is augmented by 60,000 km³ around Antarctica), and the winter sea-ice production in polynyas is greater by 42%. Outside polynyas, the impact is a reduction of sea-ice production in the Southern Ocean sea-ice pack. Impacts on the ocean circulation are also marked. Katabatic wind amplification strengthens the local overturning in coastal polynyas with a more intense transformation of Antarctic Surface Waters into colder and denser shelf waters (in total over all polynyas around Antarctica, the overturning reaches 4.7 Sv in annual mean, an increase of 1.8 Sv, and peaks to 6 Sv in winter). The modification of shelf water properties and of the zonal surface winds yields an increase of the amplitude of the seasonal cycle of the Antarctic Coastal Current.

Houssais M.-N., Herbaut C., Schlichtholz P. and C. Rousset, **Arctic salinity anomalies and their link to the North Atlantic during positive phases of the Arctic Oscillation**, *Progress in Oceanogr.*, 73, 160-189, 2007

Many of the changes observed during the last two decades of the 20th century in the Arctic Ocean and adjacent seas have been linked to the concomitant abrupt decrease of the sea level pressure associated with a shift of the Arctic Oscillation (AO) to a
positive phase, which persisted throughout the mid 1990s. The present study investigates modifications in the ocean circulation and in the fresh water storage and transport by sea ice in the context of idealized ice-ocean experiments forced by atmospheric surface wind-stress or temperature anomalies representative of a positive AO index. Wind stress anomalies representative of a positive AO index generate a decrease of the fresh water content of the upper Arctic Ocean, which is mainly concentrated in the eastern Arctic. Sea ice contributes to about two-third of this salinification. The volume of ice exported through Fram Strait increases by 20% primarily due to thicker ice advected into the strait from the northern Greenland sector, the increase of ice drift velocities having comparatively less influence. The export anomaly is comparable to those observed during events of Great Salinity Anomalies and induces substantial freshening in the Greenland Sea, which in turn contributes to increasing the fresh water export to the North Atlantic via Denmark Strait. With a fresh water export anomaly of 7 mSv, the latter is the main fresh water supplier to the subpolar North Atlantic. The removal of fresh water by sea ice mainly occurs through enhanced thin ice growth in the eastern Arctic. Winter SAT anomalies have little impact on the thermodynamic sea ice response, which is rather dictated by wind driven ice deformation changes. The global sea ice mass balance of the western Arctic indicates almost no net sea ice melt due to competing seasonal thermodynamic processes. The surface freshening and likely enhanced sea ice melt observed in the western Arctic during the 1990s should therefore be attributed to extra-winter atmospheric effects, such as the noticeable recent spring-summer warming in the Canada-Alaska sector, or to other modes of atmospheric circulations than the AO, especially in relation to the North Pacific variability.

Williams, G. D., Hindell M., Houssais M.-N., Tamura T. and I. C. Field, Upper ocean stratification and sea ice growth rates during the summer-fall transition, as revealed by Elephant seal foraging in the Adélie Depression, East Antarctica, Ocean Sci. Discuss., 7, 1–40.

Southern elephant seals (Mirounga leonina), fitted with Conductivity-Temperature-Depth sensors at Macquarie Island in January 2005 and 2010, collected unique oceanographic observations of the Adélie and George V Land continental shelf (140–148°E) during the summer-fall transition (late February through April). This is a key region of dense shelf water formation from enhanced sea ice growth/brine-rejection in the local coastal polynyas. In 2005 two seals occupied the continental shelf break near the grounded icebergs at the northern end of the Mertz Glacier Tongue for nearly two weeks at the onset of sea ice growth. In 2010, after that years calving of the Mertz Glacier Tongue, two seals migrated to the same region but penetrated much further southwest across the Adélie Depression and occupied the Commonwealth Bay polynya from March through April. Here we present unique observations of the regional oceanography during the summer-fall transition, in particular the upper ocean stratification across the Adélie Depression, including alongside iceberg C28 that calved from the Mertz Glacier and the convective overturning of the deep remnant seasonal mixed layer in Commonwealth Bay from sea ice growth (7.5–12.5 cm s⁻¹). Heat and freshwater budgets to 200–300m are used to estimate the ocean heat content, heat flux and sea ice growth rates. We speculate that the continuous foraging by the seals within Commonwealth Bay during the summer-fall transition was due to favorable feeding conditions resulting from the convective overturning of the deep seasonal mixed layer and chlorophyll maximum that is a reported feature of this location.
Krinner, G., A. Rinke, K. Dethloff, et I. Gorodetskaya. **Impact of prescribed Arctic sea ice thickness in simulations of the present and future climate. Climate Dynamics**, 35, 619-633, 2010.

This paper describes atmospheric general circulation model climate change experiments in which the Arctic sea-ice thickness is either fixed to 3 m or somewhat more realistically parameterized in order to take into account essentially the spatial variability of Arctic sea-ice thickness, which is, to a first approximation, a function of ice type (perennial or seasonal). It is shown that, both at present and at the end of the twenty-first century (under the SRES-A1B greenhouse gas scenario), the impact of a variable sea-ice thickness compared to a uniform value is essentially limited to the cold seasons and the lower troposphere. However, because first-year ice is scarce in the Central Arctic today, but not under SRES-A1B conditions at the end of the twenty-first century, and because the impact of a sea-ice thickness reduction can be masked by changes of the open water fraction, the spatial and temporal patterns of the effect of sea-ice thinning on the atmosphere differ between the two periods considered. As a consequence, not only the climate simulated at a given period, but also the simulated Arctic climate change over the twenty-first century is affected by the way sea-ice thickness is prescribed.

### 3-2 - Other references:

Marsan, D., Weiss, J., Metaxian, J.P., Grangeon, J., Roux, P.F. and Haapala, J., **Low frequency bursts of horizontally-polarized waves in the Arctic sea ice cover: a signature of remote regional-scale icequakes?**, *J. Glaciol.*, in press

Rampal, P., Weiss, J., Marsan, D. and Bourgoin, M., **Arctic sea ice velocity field: general circulation and turbulent-like fluctuations**, *J. Geophys. Res.*, 114, C10014, 2009

Girard, L., Weiss, J., Molines, J.M., Barnier, B. and Bouillon, S., **Evaluation of high resolution sea ice models on the basis of statistical and scaling properties of Arctic sea ice drift and deformation**, *J. Geophys. Res.*, 114, C08015, 2009

Weiss, J. and Schulson, E.M., **Coulombic faulting from the grain scale to the geophysical scale: Lessons from ice**, *J. Phys. D: Appl. Phys.*, 42, 214017, 2009

Weiss, J., Marsan, D. and Rampal, P., **Space and time scaling laws induced by the multiscale fracturing of the Arctic sea ice cover**, in *Scaling in Solid Mechanics*, IUTAM Bookseries Vol. 10, Springer (P. Borodich Ed.), 101-109, 2009

Weiss, J., **Intermittency of principal stress directions within Arctic sea ice**, *Phys. Rev. E*, 77, 056106, 2008

Rampal, P., Weiss, J., Marsan, D., Lindsay, R., Stern, H., **Scaling properties of sea ice deformation from buoy dispersion analysis**, *J. Geophys. Res.*, 113, C03002, 2008

Germe, A., Houssais M.-N., Herbaut C. and C. Cassou, **Greenland Sea sea ice variability over 1979-2007 and its link to the surface atmosphere**, *J. Geophys. Res.*, submitted, 2010.

Schlichtholz, P. and M.-N. Houssais, **Forcing of oceanic heat anomalies by air-sea interactions in the Nordic Seas area**, *J. Geophys. Res.*, doi:10.1029/2009JC005944, 2010.
**4-1 Dynamics and modelling**

**4-1-1 - Main references with abstracts**

Alvarez-Solas, J., S. Charbit, C. Ritz, D. Paillard, G. Ramstein and C. Dumas, Links between ocean temperature and iceberg discharge during Heinrich events. Nature Geoscience, 10.1038/ngeo752, 10.1038/ngeo752, (122126) 2010.

Palaeoclimate records have revealed the presence of millennial-scale climate oscillations throughout the last glacial period1. Six periods of extreme cooling in the Northern Hemisphere—known as Heinrich events—were marked by an enhanced discharge of icebergs into the North Atlantic Ocean2,3, increasing the deposition of ice-rafted debris2. Increased sliding at the base of ice sheets as a result of basal warming has been proposed to explain the iceberg pulses4–6, but recent observations7,8 suggest that iceberg discharge is related to a strong coupling between ice sheets, ice shelves and ocean conditions. Here we use a conceptual numerical model to simulate the effect of ocean temperature on ice-shelf width, as well as the impact of the resultant changes in ice-shelf geometry on ice-stream velocities. Our results demonstrate that ocean temperature oscillations affect the basal melting of the ice shelf and will generate periodic pulses of iceberg discharge in an ice sheet with a fringing shelf. We also find that the irregular occurrence of Heinrich events seen in the palaeoclimate records can be simulated by periodic ocean forcing combined with varying accumulation rates of the ice sheet. Our model simulations support a link between millennial-scale ocean temperature variability and Heinrich events during the last glacial period.

Charbit, S., C. Ritz, G. Philippon, V. Peyaud and M. Kageyama, Numerical reconstructions of the Northern Hemisphere ice sheets through the last glacial-interglacial cycle. Climate of the Past, 15-37, 2007.

A 3-dimensional thermo-mechanical ice-sheet model is used to simulate the evolution of the Northern Hemisphere ice sheets through the last glacial-interglacial cycle. The ice-sheet model is forced by the results from six different atmospheric general circulation models (AGCMs). The climate evolution over the period under study is reconstructed using two climate equilibrium simulations performed for the Last Glacial Maximum (LGM) and for the present-day periods and an interpolation through time between these snapshots using a glacial index calibrated against the GRIP 18O record. Since it is driven by the timing of the GRIP signal, the temporal evolution of the ice volume and the ice-covered area is approximately the same from one simulation to the other. However, both ice volume curves and spatial distributions of the ice sheets present some major differences from one AGCM forcing to the other. The origin of these differences, which are most visible in the maximum amplitude of the ice volume, is analyzed in terms of differences in climate forcing. This analysis allows for a partial evaluation of the ability of GCMs to simulate climates consistent with the reconstructions of past ice sheets. Although some models properly reproduce the advance or retreat of ice sheets in some specific areas, none of them is able to reproduce both North American or Eurasian ice complexes in full agreement with observed sea-level variations and geological data. These deviations can be attributed to shortcomings in the climate forcing and in the LGM ice-sheet reconstruction used
as a boundary condition for GCM runs, but also to missing processes in the ice-sheet model itself.

Peyaud, V., C. Ritz and G. Krinner, Modelling the Early Weichselian Eurasian ice sheets: role of ice shelves and influence of ice-dammed lakes. Climate of the Past, 375-386, 2007.

During the last glaciation, a marine ice sheet repeatedly appeared in Eurasia. The floating part of this ice sheet was essential to its rapid extension over the seas. During the earliest stage (90 kyr BP), large ice-dammed lakes formed south of the ice sheet. These lakes are believed to have cooled the climate at the margin of the ice. Using an ice sheet model, we investigated the role of ice shelves during the inception and the influence of ice-dammed lakes on the ice sheet evolution. Inception in Barents sea seems due to thickening of a large ice shelf. We observe a substantial impact of the lakes on the evolution of the ice sheets. Reduced summer ablation enhances ice extent and thickness, and the deglaciation is delayed by 2000 years.

Gagliardini, O., G. Durand, T. Zwinger, R. Hindmarsh and E. LeMeur, Coupling of ice-shelf melting and buttressing is a key process in ice-sheets dynamics. Geophys. Res. Lett., 10.1029/2010GL043334, [10.1029/2010GL043334](https://doi.org/10.1029/2010GL043334), (L14501) 2010.

Increase in ice-shelf melting is generally presumed to have triggered recent coastal ice-sheet thinning. Using a full-Stokes finite element model which includes a proper description of the grounding line dynamics, we investigate the impact of melting below ice shelves. We argue that the influence of ice-shelf melting on the ice-sheet dynamics induces a complex response, and the first naive view that melting inevitably leads to loss of grounded ice is erroneous. We demonstrate that melting acts directly on the magnitude of the buttressing force by modifying both the area experiencing lateral resistance and the ice-shelf velocity, indicating that the decrease of back stress imposed by the ice-shelf is the prevailing cause of inland dynamical thinning. We further show that feedback from melting and buttressing forces can lead to nontrivial results, as an increase in the average melt rate may lead to inland ice thickening and grounding line advance.

Durand, G., O. Gagliardini, B. De Fleurian, T. Zwinger and E. Le Meur, Marine Ice-Sheet Dynamics: Hysteresis and Neutral Equilibrium. J. of Geophys. Res., 10.1029/2008JF001170, [10.1029/2008JF001170](https://doi.org/10.1029/2008JF001170), (114) F03009, 2009.

The stability of marine ice sheets and outlet glaciers is mostly controlled by the dynamics of their grounding line, i.e., where the bottom contact of the ice changes from bedrock or till to ocean water. The last report of the Intergovernmental Panel on Climate Change has clearly underlined the poor ability of models to capture the dynamics of outlet glaciers. Here we present computations of grounding line dynamics on the basis of numerical solutions of the full Stokes equations for ice velocity, coupled with the evolution of the air ice- and sea ice-free interfaces. The grounding line position is determined by solving the contact problem between the ice and a rigid bedrock using the finite element code Elmer. Results of the simulations show that marine ice sheets are unstable on upsloping beds and undergo hysteresis under perturbation of ice viscosity, confirming conclusions from boundary layer theory. The present approach also indicates that a 2-D unconfined marine ice sheet sliding over a downsloping bedrock does not exhibit neutral equilibrium. It is shown that mesh resolution around the grounding line is a crucial issue. A very fine grid size (<100 m spacing) is needed in order to achieve consistent results.
Parrenin, F., et al. 1-D ice flow modelling at EPICA Dome C and Dome Fuji, East Antarctica. Climate of the Past, 3, 243-259, 2007.

One-dimensional (1-D) ice flow models are used to construct the age scales at the Dome C and Dome Fuji drilling sites (East Antarctica). The poorly constrained glaciological parameters at each site are recovered by fitting independent age markers identified within each core. We reconstruct past accumulation rates, that are larger than those modelled using the classical vapour saturation pressure relationship during glacial periods by up to a factor 1.5. During the Early Holocene, changes in reconstructed accumulation are not linearly related to changes in ice isotopic composition. A simple model of past elevation changes is developed and shows an amplitude variation of 110–120m at both sites. We suggest that there is basal melting at DomeC (0.56±0.19 mm/yr). The reconstructed velocity profile is highly non-linear at both sites, which suggests complex ice flow effects. This induces a non-linear thinning function in both drilling sites, which is also characterized by bumps corresponding to variations in ice thickness with time.

Colleoni, F., G. Krinner, et M. Jakobsson. The role of an Arctic ice shelf in the climate of the last glacial maximum of MIS 6 (140 ka). Quat. Sci. Res., 29, 3590-3597, 2010.

During the last decade, Arctic icebreaker and nuclear submarine expeditions have
revealed large-scale Pleistocene glacial erosion on the Lomonosov Ridge, Chukchi
Borderland and along the Northern Alaskan margin indicating that the glacial Arctic
Ocean hosted large Antarctic-style ice shelves. Dating of sediment cores indicates that
the most extensive and deepest ice grounding occurred during Marine Isotope Stage
(MIS) 6. The precise extents of Pleistocene ice shelves in the Arctic Ocean are
unknown but seem comparable to present existing Antarctic ice shelves. How would
an Antarctic-style ice shelf in the MIS 6 Arctic Ocean influence the Northern
Hemisphere climate? Could it have impacted on the surface mass balance (SMB) of
the MIS 6 Eurasian ice sheet and contributed to its large southward extent? We use an
Atmospheric General Circulation Model (AGCM) to investigate the climatic impacts
of both a limited MIS 6 ice shelf covering portions of the Canada Basin and a fully ice
shelf covered Arctic Ocean. The AGCM results show that both ice shelves cause a
temperature cooling of about 3 °C over the Arctic Ocean mainly due to the combined
effect of ice elevation and isolation from the underlying ocean heat fluxes stopping the
snow cover from melting during summer. The calculated SMB of the ice shelves are
positive. The ice front horizontal velocity of the Canada Basin ice shelf is estimated
to ≈ 1 km yr⁻¹ which is comparable to the recent measurements of the Ross ice shelf,
Antarctica. The existence of a large continuous ice shelf covering the entire Arctic
Ocean would imply a mean annual velocity of icebergs of ≈12 km yr⁻¹ through the
Fram Strait. Our modeling results show that both ice shelf configurations could be
viable under the MIS 6 climatic conditions. However, the cooling caused by these ice
shelves only affects the Arctic margins of the continental ice sheets and is not strong
enough to significantly influence the surface mass balance of the entire MIS 6
Eurasian ice sheet.
## 4-2 Surface mass-balance

### 4-2-1 - Main references with abstracts

O. Magand, G. Picard, L. Brucker, M. Fily, and C. Genthon **Snow melting bias in microwave mapping of Antarctic snow accumulation** *The Cryosphere*, 2, 109-115, 2008

*Abstract.* Satellite records of microwave surface emission have been used to interpolate in-situ observations of Antarctic surface mass balance (SMB) and build continental-scale maps of accumulation. Using a carefully screened subset of SMB measurements in the 90°–180° E sector, we show a reasonable agreement with microwave-based accumulation map in the dry-snow regions, but large discrepancies in the coastal regions where melt occurs during summer. Using an emission microwave model, we explain the failure of microwave sensors to retrieve SMB by the presence of layers created by melt/refreeze cycles. We conclude that regions potentially affected by melting should be masked-out in microwave-based interpolation schemes.

Urbini S., Frezzotti M., Gandolfi S., Vincent C., Scarchilli C., Vittuari L., Fily M., 2008, **Historical behaviour of Dome C and Talos Dome (East Antarctica) as investigated by snow accumulation and ice velocity measurements.**, *Global and Planetary Change*, 60, 576-588.

Ice divide-dome behaviour is used for ice sheet mass balance studies and interpretation of ice core records. In order to characterize the historical behaviour (last 400 yr) of Dome C and Talos Dome (East Antarctica), ice velocities have been measured since 1996 using a GPS system, and the palaeo-spatial variability of snow accumulation has been surveyed using snow radar and firn cores. The snow accumulation distribution of both domes indicates distributions of accumulation that are non-symmetrical in relation to dome morphology. Changes in spatial distributions have been observed over the last few centuries, with a decrease in snow accumulation gradient along the wind direction at Talos Dome and a counter-clockwise rotation of accumulation distribution in the northern part of Dome C. Observations at Dome C reveal a significant increase in accumulation since the 1950s, which could correlate to altered snow accumulation patterns due to changes in snowfall trajectory. Snow accumulation mechanisms are different at the two domes: a wind-driven snow accumulation process operates at Talos Dome, whereas snowfall trajectory direction is the main factor at Dome C. Repeated GPS measurements made at Talos Dome have highlighted changes in ice velocity, with a deceleration in the NE portion, acceleration in the SW portion and migration of dome summit, which are apparently correlated with changes in accumulation distribution. The observed behaviour in accumulation and velocity indicates that even the most remote areas of East Antarctica have changed from a decadal to secular scale.

Magand, O., C. Genthon, M. Fily, G. Krinner, G. Picard, M. Frezzotti, and A. A. Ekaykin, 2007, **An up-to-date quality-controlled surface mass balance data set for the 90 180E Antarctica sector and 1950 2005 period**, *J. Geophys. Res.*, 112, D12106, doi:10.1029/2006JD007691.

On the basis of thousands of surface mass balance (SMB) field measurements over the entire Antarctic ice sheet it is currently estimated that more than 2 Gt of ice accumulate each year at the surface of Antarctica. However, these estimates suffer from large uncertainties. Various problems affect Antarctic SMB measurements, in
particular, limited or unwarranted spatial and temporal representativeness,
measurement inaccuracy, and lack of quality control. We define quality criteria on the
basis of (1) an up-to-date review and quality rating of the various SMB measurement
methods and (2) essential information (location, dates of measurements, time period
covered by the SMB values, and primary data sources) related to each SMB data. We
apply these criteria to available SMB values from Queen Mary to Victoria lands (90–
180E Antarctic sector) from the early 1950s to present. This results in a new set of
observed SMB values for the 1950–2005 time period with strong reduction in density
and coverage but also expectedly reduced inaccuracies and uncertainties compared to
other compilations. The quality-controlled SMB data set also contains new results
from recent field campaigns (International Trans-Antarctic Scientific Expedition
(ITASE), Russian Antarctic Expedition (RAE), and Australian National Antarctic
Research Expeditions (ANARE) projects) which comply with the defined quality
criteria. A comparative evaluation of climate model results against the quality-
controlled updated SMB data set and other widely used ones illustrates that such
Antarctic SMB studies are significantly affected by the quality of field SMB values
used as reference.

Fettweis, X., E. Hanna, H. Gallée, P. Huybrechts and M. Erpicum, **Estimation of tfe**
**Greenland ice sheet surface mass balance for the 20th and 21st centuries.** *The*
*Cryosphere, **2**, 117-129, 2008.

Results from a regional climate simulation (1970 2006) over the Greenland ice sheet (GrIS) reveals that more than 97% of the interannual variability of the modelled Surface Mass Balance (SMB) can be explained by the GrIS summer temperature anomaly and the GrIS annual precipitation anomaly. This multiple regression is then used to empirically estimate the GrIS SMB since 1900 from climatological time series. The projected SMB changes in the 21st century are investigated with the set of simulations performed with atmosphere-ocean general circulation models (AOGCMs) of the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR4). These estimates show that the high surface mass loss rates of recent years are not unprecedented in the GrIS history of the last hundred years. The minimum SMB rate seems to have occurred earlier in the 1930s and corresponds to a zero SMB rate. The AOGCMs project that the SMB rate of the 1930s would be common at the end of 2100. The temperature would be higher than in the 1930s but the increase of accumulation in the 21st century would partly offset the acceleration of surface melt due to the temperature increase. However, these assumptions are based on an empirical multiple regression only validated for recent/current climatic conditions, and the accuracy and time homogeneity of the data sets and AOGCM results used in these estimations constitute a large uncertainty.

Fettweis, X., J.P. Van Ypersele, H. Gallée, F. Lefebre and W. Lefebvre, **The 1979-2005**
**Greenland ice sheet melt extent from passive microwave data using and improved**
**version of the melt retrieval XPGR algorithm.** *Geophysical Research*
*Letter*, **10.1029/2006GL028787**, **34**, L05502, 2007.

Analysis of passive microwave satellite observations over the Greenland ice sheet reveals a significant increase in surface melt over the period 1979-2005. Since 1979, the total melt area was found to have increased by +1.22 x 10(7) km(2). An improved version of the cross-polarized gradient ratio (XPGR) technique is used to identify the melt from the brightness temperatures. The improvements in the melt retrieval XPGR algorithm as well as the surface melt acceleration are discussed with results from a
coupled atmosphere-snow regional climate model. From 1979 to 2005, the ablation period has been increasing everywhere over the melt zone except in the regions where the model simulates an increased summer snowfall. Indeed, more snowfall in summer decreases the liquid water content of the snowpack, raises the albedo and therefore reduces the melt. Finally, the observed melt acceleration over the Greenland ice sheet is highly correlated with both Greenland and global warming suggesting a continuing surface melt increase in the future.

Eisen, O., et al. **Snow accumulation in East Antarctica.** *Review of Geophysics*, 10.1029/2006RG000218, **46**, (46) RG2001, 2008.

The East Antarctic Ice Sheet is the largest, highest, coldest, driest, and windiest ice sheet on Earth. Understanding of the surface mass balance (SMB) of Antarctica is necessary to determine the present state of the ice sheet, to make predictions of its potential contribution to sea level rise, and to determine its past history for paleoclimatic reconstructions. However, SMB values are poorly known because of logistic constraints in extreme polar environments, and they represent one of the biggest challenges of Antarctic science. Snow accumulation is the most important parameter for the SMB of ice sheets. SMB varies on a number of scales, from small-scale features (sastrugi) to ice-sheet-scale SMB patterns determined mainly by temperature, elevation, distance from the coast, and wind-driven processes. In situ measurements of SMB are performed at single points by stakes, ultrasonic sounders, snow pits, and firn and ice cores and laterally by continuous measurements using ground-penetrating radar. SMB for large regions can only be achieved practically by using remote sensing and/or numerical climate modeling. However, these techniques rely on ground truthing to improve the resolution and accuracy. The separation of spatial and temporal variations of SMB in transient regimes is necessary for accurate interpretation of ice core records. In this review we provide an overview of the various measurement techniques, related difficulties, and limitations of data interpretation; describe spatial characteristics of East Antarctic SMB and issues related to the spatial and temporal representativity of measurements; and provide recommendations on how to perform in situ measurements

Krinner, G., B. Guicherd, K. Ox, C. Genthon and O. Magand, **Influence of oceanic boundary conditions in simulations of Antarctic climate and surface mass balance change during the coming century.** *J. of Climate*, 10.1175/2007JCLI1690.1, **21**, 938-962, 2008.

This article reports on high-resolution (60 km) atmospheric general circulation model simulations of the Antarctic climate for the periods 1981-2000 and 2081-2100. The analysis focuses on the surface mass balance change, one of the components of the total ice sheet mass balance, and its impact on global eustatic sea level. Contrary to previous simulations, in which the authors directly used sea surface boundary conditions produced by a coupled ocean-atmosphere model for the last decades of both centuries, an anomaly method was applied here in which the present-day simulations use observed sea surface conditions, while the simulations for the end of the twenty-first century use the change in sea surface conditions taken from the coupled simulations superimposed on the present-day observations. It is shown that the use of observed oceanic boundary conditions clearly improves the simulation of the present-day Antarctic climate, compared to model runs using boundary conditions from a coupled climate model. Moreover, although the spatial patterns of the simulated climate change are similar, the two methods yield significantly different
estimates of the amplitude of the future climate and surface mass balance change over the Antarctic continent. These differences are of similar magnitude as the intermodel dispersion in the current Intergovernmental Panel on Climate Change (IPCC) exercise: selecting a method for generating boundary conditions for a high-resolution model may be just as important as selecting the climate model itself. Using the anomaly method, the simulated mean surface mass balance change over the grounded ice sheet from 1981-2000 to 2081-2100 is 43-mm water equivalent per year, corresponding to a eustatic sea level decrease of 1.5 mm yr⁻¹. A further result of this work is that future continental-mean surface mass balance changes are dominated by the coastal regions, and that high-resolution models, which better resolve coastal processes, tend to predict stronger precipitation changes than models with lower spatial resolution.

Krinner, G., O. Magand, I. Simmonds, C. Genthon, and J.-L. Dufresne. Simulated Antarctic precipitation and surface mass balance at the end of the 20th and 21st centuries. *Clim. Dyn.*, **28**, 215-230, 2007.

The aim of this work is to assess potential future Antarctic surface mass balance changes, the underlying mechanisms, and the impact of these changes on global sea level. To this end, this paper presents simulations of the Antarctic climate for the end of the twentieth and twenty-first centuries. The simulations were carried out with a stretched-grid atmospheric general circulation model, allowing for high horizontal resolution (60 km) over Antarctica. It is found that the simulated present-day surface mass balance is skilful on continental scales. Errors on regional scales are moderate when observed sea surface conditions are used; more significant regional biases appear when sea surface conditions from a coupled model run are prescribed. The simulated Antarctic surface mass balance increases by 32 mm water equivalent per year in the next century, corresponding to a sea level decrease of 1.2 mm year⁻¹ by the end of the twenty-first century. This surface mass balance increase is largely due to precipitation changes, while changes in snow melt and turbulent latent surface fluxes are weak. The temperature increase leads to an increased moisture transport towards the interior of the continent because of the higher moisture holding capacity of warmer air, but changes in atmospheric dynamics, in particular off the Antarctic coast, regionally modulate this signal.

### 4-2-2 – Other references without abstracts

G. Picard, M. Fily, H. Gallee, Surface melting derived from microwave radiometers: a climatic indicator in Antarctica. *Annals of Glaciology*, vol 46, pp 29-34, 2007

Genthon, C., Magand, O., Krinner, G., Fily, M., 2009, Do climate models underestimate snow accumulation on the Antarctic plateau? A reevalutation of / from in-situ observations in East Wilkes and – Victoria Lands, *Annals of Glaciology*, **50**, 61-65.

Genthon, C., G. Krinner and H. Castebrunet, Antarctic precipitation and climate change predictions: Horizontal resolution and margin vs plateau issues. *Annals of glaciology*, **50**, 55-60, 2009.

Genthon, C., P Lardeux and G. Krinner, The surface accumulation and ablation of a blue ice area near Cap Prudhomme, Adélie Land, Antarctica. *J. Glaciol.*, **183**, (53) 635645, 2007.
# 5 - ICE CORES AND POLAR FIRN

## 5-1 Ice cores

### 5-1-1 Main references with abstracts

Jouzel J. et al., Orbital and millenial antarctic climate variability over the last 800 000 years, *Science*, 317, 793, 2007, DOI: 10.1126/science.1141038

*Abstract:* A high-resolution deuterium profile is now available along the entire European Project for Ice Coring in Antarctica Dome C ice core, extending this climate record back to marine isotope stage 20.2, ~800,000 years ago. Experiments performed with an atmospheric general circulation model including water isotopes support its temperature interpretation. We assessed the general correspondence between Dansgaard-Oeschger events and their smoothed Antarctic counterparts for this Dome C record, which reveals the presence of such features with similar amplitudes during previous glacial periods. We suggest that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records.

K.Kawamura, et al., Northern Hemisphere forcing of climatic cycles in Antarctica over the past 360,000 years. *Nature*, 2007

*Abstract:* The Milankovitch theory of climate change proposes that glacial-interglacial cycles are driven by changes in summer insolation at high northern latitudes. The timing of climate change in the Southern Hemisphere at glacial-interglacial transitions (which are known as terminations) relative to variations in summer insolation in the Northern Hemisphere is an important test of this hypothesis. So far, it has only been possible to apply this test to the most recent termination, because the dating uncertainty associated with older terminations is too large to allow phase relationships to be determined. Here we present a new chronology of Antarctic climate change over the past 360,000 years that is based on the ratio of oxygen to nitrogen molecules in air trapped in the Dome Fuji and Vostok ice cores. This ratio is a proxy for local summer insolation, and thus allows the chronology to be constructed by orbital tuning without the need to assume a lag between a climate record and an orbital parameter. The accuracy of the chronology allows us to examine the phase relationships between climate records from the ice cores and changes in insolation. Our results indicate that orbital-scale Antarctic climate change lags Northern Hemisphere insolation by a few millennia, and that the increases in Antarctic temperature and atmospheric carbon dioxide concentration during the last four terminations occurred within the rising phase of Northern Hemisphere summer insolation. These results support the Milankovitch theory that Northern Hemisphere summer insolation triggered the last four deglaciations.

Loulergue, L., Schilt, A., Spahni, R., Masson-Delmotte, V., Blunier, T., Lemieux, B., Barnola, J.-M., Raynaud, D., Stocker, T. F., and Chappellaz, J. (2008). **Orbital and millennial-scale features of atmospheric CH4 over the past 800,000 years.** *Nature* 453, 383-386.

*Abstract:* Atmospheric methane is an important greenhouse gas and a sensitive indicator of climate change and millennial-scale temperature variability. Its concentrations over the past 650,000 years have varied between ,350 and ,800 parts
per 109 by volume (p.p.b.v.) during glacial and interglacial periods, respectively.
In comparison, present-day methane levels of, 1,770 p.p.b.v. have been reported.
Insights into the external forcing factors and internal feedbacks controlling
atmospheric methane are essential for predicting the methane budget in a warmer
world.
Here we present a detailed atmospheric methane record from the EPICA
Dome C ice core that extends the history of this greenhouse gas to 800,000 yr before
present. The average time resolution of the new data is ,380 yr and permits the
identification of orbital and millennial-scale features. Spectral analyses indicate that
the longterm variability in atmospheric methane levels is dominated by ,100,000 yr
glacial-interglacial cycles up to ,400,000 yr ago with an increasing contribution of
the precessional component during the four more recent climatic cycles. We suggest
that changes in the strength of tropical methane sources and sinks (wetlands,
atmospheric oxidation), possibly influenced by changes in monsoon systems and the
position of the intertropical convergence zone, controlled the atmospheric methane
budget, with an additional source input during major terminations as the retreat of the
northern ice sheet allowed higher methane emissions from extending periglacial
wetlands. Millennial-scale changes in methane levels identified in our record as being
associated with Antarctic isotope maxima events1,4 are indicative of ubiquitous
millennial-scale temperature variability during the past eight glacial cycles.

Lüthi, D., Le Floch M., Bereiter B., Blunier T., Barnola J.M., Siegenthaler U., Raynaud R., Jouzel J., Fischer H., Kawamura K. and Stocker T.F. (2008). **High-resolution carbon dioxide concentration record 650,000-800,000 years before present**, Nature, 453: 379-382.

Abstract: Changes in past atmospheric carbon dioxide concentrations can be determined by measuring the composition of air trapped in ice cores from Antarctica. So far, the Antarctic Vostok and EPICA Dome C ice cores have provided a composite record of atmospheric carbon dioxide levels over the past 650,000 years1–4. Here we present results of the lowest 200m of the Dome C ice core, extending the record of atmospheric carbon dioxide concentration by two complete glacial cycles to 800,000 yr before present. From previously published data1–8 and the present work, we find that atmospheric carbon dioxide is strongly correlated with Antarctic temperature throughout eight glacial cycles but with significantly lower concentrations between 650,000 and 750,000 yr before present. Carbon dioxide levels are below 180 parts per million by volume (p.p.m.v.) for a period of 3,000 yr during Marine Isotope Stage 16, possibly reflecting more pronounced oceanic carbon storage. We report the lowest carbon dioxide concentration measured in an ice core, which extends the pre-industrial range of carbon dioxide concentrations during the late Quaternary by about 10 p.p.m.v. to 172–300 p.p.m.v.

Lourantou A., Lavric J.V., Köhler P., Barnola J.M., Michel E., Paillard D., Raynaud D. and Chappellaz J. (2010). **Constraint of the CO2 rise by new atmospheric carbon isotopic measurements during the last deglaciation**. Global Biogeochemical Cycles, 24, GB2015, doi:10.1029/2009GB003545, 2010.

Abstract: The causes of the 80 ppmv increase of atmospheric carbon dioxide (CO2) during the last glacial-interglacial climatic transition remain debated. We analyzed the parallel evolution of CO2 and its stable carbon isotopic ratio (δ13CO2) in the European Project for Ice Coring in Antarctica (EPICA) Dome C ice core to bring additional constraints. Agreeing well but largely improving the Taylor Dome ice core record of lower resolution, our δ13CO2 record is characterized by a W shape, with two negative δ13CO2 excursions of 0.5‰ during Heinrich 1 and Younger Dryas events, bracketing a positive δ13CO2 peak during the Bølling/Allerød warm period. The comparison with marine records and the outputs of two C cycle box models
suggest that changes in Southern Ocean ventilation drove most of the CO₂ increase, with additional contributions from marine productivity changes on the initial CO₂ rise and δ¹³CO₂ decline and from rapid vegetation buildup during the CO₂ plateau of the Bølling/Allerød.

Baroni, M., M. H. Thiemens, R. J. Delmas, and J. Savarino (2007), **Mass-independent sulfur isotopic compositions in stratospheric volcanic eruptions**, *Science*, **315*(5808), 84-87.

The observed mass-independent sulfur isotopic composition (Î"33S) of volcanic sulfate from the Agung (March 1963) and Pinatubo (June 1991) eruptions recorded in the Antarctic snow provides a mechanism for documenting stratospheric events. The sign of Î"33S changes over time from an initial positive component to a negative value. Î"33S is created during photochemical oxidation of sulfur dioxide to sulfuric acid on a monthly time scale, which indicates a fast process. The reproducibility of the results reveals that Î"33S is a reliable tracer to chemically identify atmospheric processes involved during stratospheric volcanism.

Baroni, M., J. Savarino, J. Cole-Dai, V. K. Rai, and M. H. Thiemens (2008), **Anomalous sulfur isotope compositions of volcanic sulfate over the last millennium in Antarctic ice cores**, *Journal of Geophysical Research*, **113**(D20), D20112, 10.1029/2008jd010185.

The reconstruction of past volcanism from glaciological archives is based on the measurement of sulfate concentrations in ice. This method does not allow a proper evaluation of the climatic impact of an eruption owing to the uncertainty in classifying an event between stratospheric or tropospheric. This work develops a new method, using anomalous sulfur isotope composition of volcanic sulfate in order to identify stratospheric eruptions over the last millennium. The advantages and limits of this new method are established with the examination of the 10 largest volcanic signals in ice cores from Dome C and South Pole, Antarctica. Of the 10, seven are identified as stratospheric eruptions. Among them, three have been known to be stratospheric (Tambora, Kuwae, the 1259 Unknown Event) and they exhibit anomalous sulfur isotope compositions. Three unknown events (circa 1277, 1230, 1170 A.D.) and the Serua eruption have been identified as stratospheric eruptions, which suggests for the first time that they could have had significant climatic impact. However, the Kuwae and the 1259 Unknown Event stratospheric eruptions exhibit different anomalous sulfur isotope compositions between South Pole and Dome C samples. Differences in sulfate deposition and preservation patterns between the two sites can help explain these discrepancies. This study shows that the presence of an anomalous sulfur isotope composition of volcanic sulfate in ice core indicates a stratospheric eruption, but the absence of such composition does not necessarily lead to the conclusion of a tropospheric process because of differences in the sulfate deposition on the ice sheet.

Cole-Dai, J., D. Ferris, A. Lanciki, J. Savarino, M. Baroni, and M. H. Thiemens (2009), **Cold decade (AD 1810-1819) caused by Tambora (1815) and another (1809) stratospheric volcanic eruption**, *Geophysical Research Letters*, **36**(22), L22703, doi:22710.21029/22009GL040882.

Climate records indicate that the decade of AD 1810–1819 including the year without a summer (1816) is probably the coldest during the past 500 years or longer, and the cause of the climatic extreme has been attributed primarily to the 1815 cataclysmic Tambora eruption in Indonesia. But the cold temperatures in the early part of the decade and the timing of the Tambora eruption call into question the real climatic impact of volcanic eruptions. Here we present new evidence, based on sulfur
isotope anomaly (D33S), a unique indicator of volcanic sulfuric acid produced in the stratosphere and preserved in polar snow, and on the precise timing of the volcanic deposition in both polar regions, that another large eruption in 1809 of a volcano is also stratospheric and occurred in the tropics. The Tambora eruption and the undocumented 1809 eruption are together responsible for the unusually cold decade.

### 5-1-2 – Other references without abstracts

2007

J.Jouzel, M.Stiévenard, S.J.Johnsen, K.Fuhrer, A.Landais, V.Masson-Delmotte, A.E.Sveinbjörnsdottir, F.Vimeux, J.W.C.White. The GRIP deuterium-excess record, Quat.Sci.Rev., 26, 1-17, 2007.

Hou, S., et al. (2007) Summer temperature trend over the past two millennia using air content in Himalayan ice. Climate of the Past, 3, 1-7

A.Landais, N.Combourieu Nebout, V.Masson-Delmotte, J.Jouzel, T.Blunier, M.Leuenberger, D.Dahl-Jensen, S.J. Johnsen et B.Luz, Millenial scale variations of the isotopic composition of atmospheric oxygen over Marine Isotopic Stage 4. Earth.Planet.Sci.Lett., 258 (1-2): 101-113, 2007.

F. Parrenin, et al., 1-D-ice flow modelling at EPICA Dome C and Dome Fuji, East Antarctica. Climate of the past 3 (2): 243-259, 2007

G.Raisbeck, F.Yiou, J.Jouzel, T.Stocker, Direct North-South synchronisation of abrupt climate changes using Beryllium 10, Climate of the past, 3, 1-7, 2007

G.Dreyfus, F.Parrenin, B.Lemieux-Dudon, G.Durand, V.Masson-Delmotte, J.Jouzel, J.M.Barnola, L.Panno, R.Spahni, A.Tisserand, U.Siegenthaler, M.Leuenberger, Anomalous flow below 2700 m in the EPICA Dome C ice core detected using d18O of atmospheric oxygen measurements, Climate of the Past, Special issue (EPICA ice cores age scales), 3, 341-353, 2007.

F.Parrenin, et al., The EDC3 chronology of the EPICA Dome C ice core, Climate of the Past, Special issue (EPICA ice cores age scales), 3, 485-497, 2007.

E. Bard, Raisbeck, G., Yiou, F., Jouzel, J. Comment on "Solar activity during the last 1000 yr inferred from radionuclide records" by Muscheler et al. (2007), Quat. Sci. Rev., 26, 17 - 18, 2301 - 2304, 2007.

Raynaud, D., Lipenkov, V., Lemieux-Dudon, B., Duval, P., Loutre, M-F., and Lhomme, N. (2007) : The local insolation signature of air content in Antarctic ice: A new step toward an absolute dating of ice records: Earth and Planetary Science Letters, doi:10.1016/j.epsl.2007.06.025.

2008

C. Waelbroeck, J. Jouzel, F. Parrenin, V. Masson-Delmotte, D. Genty, Tranferring radiometric dating of the last interglacial sea level high stand to marine and ice core records. Earth Planet Sci. Lett., 265, 183-194, 2008.

D. Luthi, Le Floch, M., Bereiter, B., Blunier, B., Barnola, J.M., Siegenthaler, U., Raynaud, D., Jouzel, J., Fischer, H., Kawamura, K., Stocker F.. Low carbon dioxyde in Dome C ice 650,000 - 800,000 years before present. Nature, 453, 7193, 379 - 382, 2008.

J.P.Steffensen, et al. High resolution ice core data show abrupt climate change happens in few years, Science, 321, 5889, 680-689, 2008.
G. Dreyfus, Raisbeck, G.M., Parrenin, F., Jouzel, J., Guyodo, Y., Nomade, S., Mazaud, A. "An ice core perspective on the age of the Matuyama - Brunhes boundary. *Earth Planet Sci. Lett.*, 274, 151 - 156, 2008.

2009

Tzedakis, P. C., Raynaud, D., McManus, J. F., Berger, A., Brovkin, V., and Kiefer, T. (2009). **Interglacial diversity.** *Nature Geoscience*, **2**, 751-755.

Vinther, B. M., et al., (2009). **Significant Holocene thinning of the Greenland ice sheet.** *Nature* 461, 385-388

2010

A.Landais, G. Dreyfus, E. Capron, V. Masson-Delmotte, M.F. Sanchez-Goñi, S.Desprat, G.Hoffmann, J.Jouzel, M.Leuenberger, S.Johnsen. **What drives the millennial and orbital variations of $d^{18}O_{atm}$?** *Quaternary Science Review*, 29, 1-2, 235-246, 2010.

V.Masson-Delmotte, B.Stenni, K.Pol, P.Braconnot, O.Cattani, S.Falourd, J.Jouzel, A.Landais, B.Minster, J.R.Petit, S.Johnsen, R.Röthlisberger, J.Chappellaz, J.Hansen, **EPICA Dome C record of glacial and interglacial intensities**, *Quaternary Science Review*, 29, 1-2, 113-128, 2010.

G.Dreyfus, J.Jouzel, M.L.Bender, A.Landais, V. Masson-Delmotte, M. Leuenberger, **Firn processes and $\delta^{15}N$: potential for a gas-phase climate proxy**, *Quaternary Science Review*, 29, 1-2, 28-42, 2010.

B.Stenni, V.Masson-Delmotte, E.Selmo, H.Oerter, H.Meyer, R.Rothlisberger, J.Jouzel, O.Cattani, S.Falourd, H.Fischer, G.Hoffmann, P.Iacumin, S.Johnsen, B.Minster. **The deuterium excess records of EPICA Dome C and Dronning Maud Land ice cores (East Antarctica)**, *Quaternary Science Review*, 29, 1-2, 146-159, 2010.

C.Risi, A.Landais, S.Bony, J.Jouzel, V.Masson-Delmotte, F.Vimeux. **Understanding the $^{17}$O-excess glacial-interglacial variations in Vostok precipitation**. *J.Geophys.Res.* 115, D10112, 2010.

A.A.Ekaykin, Lipenkov, V.Ya., Petit, J.R., Johnsen, S., Jouzel, J., Masson-Delmotte, V. **Insights into hydrological regime of Lake Vostok from differential behavior of deuterium and oxygen-18 in accreted ice**. *J.Geophys.Res.*, 115, C05003, 2010.

V.Masson-Delmotte, et al., **Abrupt change of Antarctic moisture origin at the end of Termination II**, *P.N.A.S*, 107, 27, 12091-12094, 2010.

K.Pol, et al., **New MIS 19 EPICA Dome C high resolution deuterium data: hints for a problematic preservation of climate variability in the "oldest ice"**, *Earth Planet.Sci. Lett.*, 298, 1-2, 95-103, 2010.

E.Capron, et al., **Millennial and sub-millennial climatic variations recorded in polar ice cores over the last glacial period**. *Clim Past*, 6, 345 - 365, 2010.

J.Jouzel and V.Masson-Delmotte. **deep ice cores : the need for going back in time**. *Quaternary Science Review*, 29 Issue: 27-28 Pages: 3683-3689, 2010

Lourantou, A., Chappellaz, J., Barnola J-M., Masson-Delmotte, V., Raynaud, D. (2010). **Changes in atmospheric CO2 and its carbon isotopic ratio during the penultimate deglaciation**, *Quaternary Science Reviews*, 29, 1983-1992
## 5-2 Polar firn

### 5-2-1 Main references with abstracts

Faïn, X., Ferrari, C.P., Dommergue, A., Albert, M.R., Battle, M., Severinghaus, J., Arnaud, L., Barnola, J.-M., Cairns, W., Barbante, C., Boutron, C., 2009. **Polar firn air reveals large-scale impact of anthropogenic mercury emissions during the 1970s. Proceedings of the National Academy of Sciences of the United States of America** 106, 16114-16119.

Mercury (Hg) is an extremely toxic pollutant, and its biogeochemical cycle has been perturbed by anthropogenic emissions during recent centuries. In the atmosphere, gaseous elemental mercury (GEM; Hg°) is the predominant form of mercury (up to 95%). Here we report the evolution of atmospheric levels of GEM in mid- to high-northern latitudes inferred from the interstitial air of firn (perennial snowpack) at Summit, Greenland. GEM concentrations increased rapidly after World War II from _1.5 ng m⁻³ reaching a maximum of _3 ng m⁻³ around 1970 and decreased until stabilizing at _1.7 ng m⁻³ around 1995._ This reconstruction reproduces real-time measurements available from the Arctic since 1995 and exhibits the same general trend observed in Europe since 1990. Anthropogenic emissions caused a two-fold rise in boreal atmospheric GEM concentrations before the 1970s, which likely contributed to higher deposition of mercury in both industrialized and remotes areas. Once deposited, this toxin becomes available for methylation and, subsequently, the contamination of ecosystems. Implementation of air pollution regulations, however, enabled a large-scale decline in atmospheric mercury levels during the 1980s. The results shown here suggest that potential increases in emissions in the coming decades could have a similar large-scale impact on atmospheric Hg levels.

Martinerie, P., E. Nourtier-Mazauric, J. M. Barnola, W. Sturges, D. R. Worton, E. Atlas, L. Gohar, K. Shine, G. P. Brasseur, **Long-lived halocarbon trends and budgets from atmospheric chemistry modelling constrained with measurements in polar firn. Atmos. Chem. Phys.**, 9, 3911-3934, 2009.

*Abstract:* The budgets of seven halogenated gases (CFC-11, CFC-12, CFC-113, CFC-114, CFC-115, $CCl_4$ and $SF_6$) are studied by comparing measurements in polar firn air from

two Arctic and three Antarctic sites, and simulation results of two numerical models: a 2-D atmospheric chemistry model and a 1-D firn diffusion model. The first one is used to calculate atmospheric concentrations from emission trends based on industrial inventories; the calculated concentration trends are used by the second one to produce depth concentration profiles in the firn. The 2-D atmospheric model is validated in the boundary layer by comparison with atmospheric station measurements, and vertically for CFC-12 by comparison with balloon and FTIR measurements. Firn air measurements provide constraints on historical atmospheric concentrations over the last century. Age distributions in the firn are discussed using a Green function approach. Finally, our results are used as input to a radiative model in order to evaluate the radiative forcing of our target gases. Multi-species and multi-site firn air studies allow to better constrain atmospheric trends. The low concentrations of all studied gases at the bottom of the firn, and their consistency with our model results confirm that their natural sources are small. Our results indicate that the emissions, sinks and trends of CFC-11, CFC-12, CFC-113, CFC-115 and $SF_6$ are well constrained, whereas it is not the case for CFC-114 and $CCl_4$. Significant emission-dependent changes in the lifetimes of halocarbons destroyed in the stratosphere were
obtained. Those result from the time needed for their transport from the surface where they are emitted to the stratosphere where they are destroyed. Efforts should be made to update and reduce the large uncertainties on CFC lifetimes.

**5-2-2 – Other references without abstracts**

Clark, I.D., L. Henderson, J. Chappellaz, D. Fisher, R. Koerner, D.E.J. Worthy, T. Kotzer, A.L. Norman, J.M. Barnola, CO₂ isotopes as tracers of firn air diffusion and age in an Arctic ice cap with summer melting, Devon Island, Canada. *J. Geophys. Res.*, 112, D01301, 2007.

Worton, D. R., W. Sturges, L. Gohar, K. Shine, P. Martinerie, D. Oram, S.P. Humpfrey, P. Begley, R. Gunn, J.M. Barnola, J. Schwander, R. Mulvaney, Atmospheric trends and radiative forcings of CF₄ and C₂F₆ inferred from firn air. *Environ. Sci. Technol.*, 31, 2184-2189, 2007.

Laube, J.C., P. Martinerie, E. Witrant, T. Blunier, J. Schwander, C.A.M. Brenninkmeijer, T.J. Schuck, M. Bolder, T. Röckmann, C. Van Der Veen, H. Bönisch, A. Engel, G.P. Mills, M.J. Newland, D.E. Oram, C.E. Reeves, WT. Sturges, Accelerating growth of HFC-227ea (1,1,1,2,3,3,3heptafluoropropane) in the atmosphere. *Atmos. Chem. Phys.*, 10, 5903-5910, 2010.

Witrant, E., P. Martinerie, A Variational Approach for Optimal Diffusivity Identification in Firns. *Proc. of the 18th IEEE Med. Conf. on Control & Automation*, 892-897, 2010.

G.Dreyfus, J.Jouzel, M.L.Bender, A.Landais, V. Masson - Delmotte, M. Leuenberger, Firn processes and δ15N: potential for a gas-phase climate proxy, Quaternary Science Review, 29, 1-2, 28-42, 2010.
**6-1- Main references with abstracts**

Koven, C., P. Friedlingstein, P. Ciais, D. Khvorostiyanov, G. Krinner, et C. Tarnocai. The effects of cryoturbation and insulation by organic matter on the formation of high-latitude soil carbon stocks in a land surface model. Geophys. Res. Lett., 36, L21501, 2009.

We modify the soil component of the ORCHIDEE terrestrial carbon cycle model to include vertically-discretized soil carbon. With this model, we investigate the feedback of considering thermal insulation by soil carbon, which modifies the soil thermal regime by lowering the thermal conductivity and increasing the heat capacity of a carbon-rich soil, on the total carbon stocks the model builds up. In addition, we demonstrate the effects of diffusive vertical mixing of soil organic matter by cryoturbation on the total carbon stocks that the model builds up in mineral soils in equilibrium with a steady climate. We show that including these two effects together leads to up to 30% higher soil carbon stocks in the top meter of permafrost soils, as well as large stocks of carbon below 1m in the upper permafrost soil layers. The vertical profile of partitioning of carbon between different lability pools is also affected, as the slower pools are more deeply mixed; also the time to reach equilibrium lengthens considerably. These effects are largest in the coldest regions such as Eastern Siberia. The inclusion of cryoturbative mixing and insulation by soil carbon leads to better agreement with estimates of high-latitude soil carbon stocks, where substantial amounts of carbon are found in permafrost regions, to depths of three meters; however we do not include peat, Yedoma, or alluvial deposition processes here, so the total carbon stocks are still lower than observed.

Khvorostyanov, D., G. Krinner, P. Ciais, M. Heimann, and S.A. Zimov. Vulnerability of permafrost carbon to global warming. Part I. Model description and role of heat generated by organic matter decomposition. Tellus, 60, 250-264, doi:10.1111/j.1600-0889.2007.00333.x, 2008.

We constructed a new model to study the sensitivity of permafrost carbon stocks to future climate warming. The one-dimensional model solves an equation for diffusion of heat penetrating from the overlying atmosphere and takes into account additional in situ heat production by active soil microorganisms. Decomposition of frozen soil organic matter and produced CO2 and methane fluxes result from an interplay of soil heat conduction and phase transitions, respiration, methanogenesis and methanotrophy processes. Respiration and methanotrophy consume soil oxygen and thus can only develop in an aerated top-soil column. In contrast, methanogenesis is not limited by oxygen and can be sustained within the deep soil, releasing sufficient heat to further thaw in depth the frozen carbon-rich soil organic matter. Heat production that accompanies decomposition and methanotrophy can be an essential process providing positive feedback to atmospheric warming through self-sustaining transformation of initially frozen soil carbon into CO2 and CH4. This supplementary heat becomes crucial, however, only under certain climate conditions. Oxygen limitation to soil respiration slows down the process, so that the mean flux of carbon released during the phase of intense decomposition is more than two times less than without oxygen limitation. Taking into account methanogenesis increases the mean carbon flux by 20%. Part II of this study deals with mobilization of frozen carbon stock in transient climate change scenarios with more elaborated methane module,
which makes it possible to consider more general cases with various site
configurations. Part I (this manuscript) studies mobilization of 400 GtC carbon stock
of the Yedoma in response to a stepwise rapid warming focusing on the role of
supplementary heat that is released to the soil during decomposition of organic
matter.
# RAPPORT QUADRIENNAL DU CNFGG A L'UGGI

## QUADRENNIAL REPORT OF CNFGG TO IUGG

### ANNEXES

### ANNEX
## Bureau du CNFGG / Bureau of CNFGG

Jérôme Dyment (Président / President)

jdy@ipgp.fr

Roland Schlich (Trésorier / Treasurer)

roland.schlich@orange.fr

Michel Menvielle (Secrétaire Général / Secretary General)

michel.menvielle@latmos.ipsl.fr

Claude Boucher (Premier Vice Président / First Vice President)

claude-boucher@club-internet.fr

Daniel Schertzer (Second Vice Président / Second Vice President)

daniel.schertzer@enpc.fr

## Bureau des Sections / Bureau of the Sections

### Section 1: Géodésie / Geodesy

Richard Biancale (Président / President)

richard.biancale@cnes.fr

Pascal Willis (Vice Président / Vice President)

willis@ipgp.fr

Stéphane Durand (Secrétaire / Secretary)

stephane.durand@esgt.cnam.fr

Claude Boucher (Ancien Président / Past Président)

claude-boucher@club-internet.fr

### Section 2: Sismologie et Physique de l'Intérieur de la Terre / Seismology and Physics of the Earth Interior

Tony Monfret (Président / President)

monfret@geoazur.unice.fr

Hélène Lyon-Caen (Vice Président / Vice President)

helene.lyon-caen@ens.fr

Mireille Laigle (Secrétaire / Secretary)

laigle@ipgp.fr

Anne Deschamps (Ancien Président / Past Président)

deschamps@geoazur.unice.fr

### Section 3: Volcanologie et Chimie de l'Intérieur de la Terre / Volcanology and Chemistry of the Earth Interior

Patrick Allard (Président / President)

pallard@ipgp.fr

Pierre Briole (Secrétaire / Secretary)

pierre.briole@ens.fr
**Section 4: Géomagnétisme et Aéronomie / Geomagnetism and Aeronomy**

Benoit Langlais (Président / President)

benoit.langlais@univ-nantes.fr

Jean-Baptiste Renard (Vice Président / Vice President)
jbrenard@cnrs-orleans.fr

Erwan Thébault (Secrétaire / Secretary)
ethebault@ipgp.fr

**Section 5: Météorologie et Sciences de l'Atmosphère / Meteorology and Atmospheric Sciences**

Vacant

**Section 6: Sciences Hydrologiques / Hydrological Sciences**

Pierrick Givone (Président / President)
pierrick.givone@cemagref.fr

Marc Lointier (Secrétaire / Secretary)
lointier@teledetection.fr

Claude Cosandey (Ancien Président / Past Président)
Claude.Cosandey@cnrs-bellevue.fr

**Section 7: Sciences Physiques de l'Océan / Physical Sciences of the Ocean**

Alain Colin de Verdière (Président / President)
acolindv@univ-brest.fr

Marie-Noëlle Houssais (Secrétaire / Secretary)
mnh@locean-ipsl.upmc.fr

Michel Crépon (Ancien Président / Past Président)
crepon@locean.jussieu.fr

**Section 8: Sciences de la Cryosphère / Cryospheric Sciences**

Michel Fily (Président / President)
Michel.Fily@lgge obs.ujf-grenoble.fr

**Conseil du CNFGG / Council of CNFGG**

Le Conseil du CNFGG est constitué du bureau du CNFGG, des bureaux des sections, et des membres français du bureau de l'UGGI ou de l'une de ses Associations. Sont membres du Conseil à ce dernier titre :

The Council of CNFGG is made of the Bureau of CNFGG, the bureaus of the Sections, and the French members of the IUGG bureau or the bureau of one of the Associations. Are members of the Council as for the latter rule:

Pierre Hubert (Secrétaire Général de l'AISH / Secretary General of IAHS)

pjy.hubert@free.fr

Mioara Mandéa (Secrétaire Général de l'AIGA / Secretary General of IAGA)
mioara@ipgp.fr