smoke signals from corals isotopic signature of the 1997 indonesian haze event abstract from september to november 1997 most of indonesia was covered by a dense blanket of haze originating from fires on sumatra and borneo specimens of porites lobata were collected from two locations i e the riau archipelago south of singapore where the haze was most dense and the karimunjawa islands north of central java where the effects were less severe all corals exhibited strong kinetic isotope effects kie on plots of 18 o vs 13 c shifts in coral metabolism associated with the haze event could be estimated from the distance individual values are positioned from the theoretical kie line skeletons of corals affected by the haze showed decreased 13 c values perhaps produced by a shift to a more heterotrophic mode of feeding these results suggest that wildfires and major forest fire events on tropical coastlines may be recorded in nearby corals as could temporal variation in frequency of major fires moreover information on coral metabolism may be determined by examining shifts of coral skeletal values in c o space

the influence of debris cover and glacial lakes on the recession of glaciers in sikkim himalaya india we investigated area changes in glaciers covering an area of similar to 200 km 2 in the tista basin sikkim eastern indian himalaya between similar to 1990 and 2010 using landsat thematic mapper tm and indian remote sensing satellite irs images and related the changes to debris cover supraglacial lakes and moraine dam lakes the glaciers lost an area of 3 3 0 8 between 1989 90 and 2010 more detailed analysis revealed an area loss of 2 00 0 82 2 56 0 61 and 2 28 2 01 km 2 for the periods 1989 97 1997 2004 05 and 2004 2009 10 respectively this indicates an accelerated retreat of glaciers after 1997 on further analysis we observed 1 the formation and expansion of supraglacial lakes on many debris covered glaciers and 2 the merging of these lakes over time leading to the development of large moraine dam lakes we also observed that debris covered glaciers with lakes lose a greater area than debris covered glaciers without lakes and debris free glaciers the climatic data for 24 years 1987 2011 measured at the gangtok meteorological station 1812 m a s l showed that the region experienced a 1 0 degrees c rise in the summer minimum temperature and a 2 0 degrees c rise in the winter minimum temperature indicating hotter summers and warmer winters there was no significant trend in the total annual precipitation we find that glacier retreat is caused mainly by a temperature increase and that debris covered glaciers can retreat at a faster rate than debris free glaciers if associated with lakes

biological and physical controls on n2 o2 and co2 distributions in contrasting southern ocean surface waters we present measurements of pco2 o2 concentration biological oxygen saturation o2 ar and n2 saturation n2 in southern ocean surface waters during austral summer 2010 2011 phytoplankton biomass varied strongly across distinct hydrographic zones with high chlorophyll a chl a concentrations in regions of frontal mixing and sea ice melt pco2 and o2 ar exhibited large spatial gradients range 90 to 450 atm and 10 to 60 respectively and covaried strongly with chl a however the ratio of biological o2 accumulation to dissolved inorganic carbon dic drawdown was significantly lower than expected from photosynthetic stoichiometry reflecting the differential time scales of o2 and co2 air sea equilibration we measured significant oceanic co2 uptake with a mean air sea flux 10 mmol m 2 d 1 that significantly exceeded regional climatological values n2 was mostly supersaturated in surface waters mean n2 of 2 5 while physical processes resulted in both supersaturation and undersaturation of mixed layer o2 mean o2phys 2 1 box model calculations were able to reproduce much of the spatial variability of n2 and o2phys along the cruise track demonstrating significant effects of air sea exchange processes e g atmospheric pressure changes and bubble injection and mixed layer entrainment on surface gas disequilibria net community production ncp derived from entrainment corrected surface o2 ar data ranged from 40 to 300 mmol o2 m 2 d 1 and showed good coherence with independent ncp estimates based on seasonal mixed layer dic deficits elevated ncp was observed in hydrographic frontal zones and stratified regions of sea ice melt reflecting physical controls on surface water light fields and nutrient availability

dissolved iron in the southern ocean atlantic sector abstract we report a comprehensive dataset of dissolved iron fe comprising 482 values at 22 complete vertical profiles along a 1 latitudinal section at the zero meridian in addition a shorter high resolution 00 09 surface section of the southernmost part of the transect 66 00 69 35 s is presented within the upper surface mixed layer the concentrations of dissolved fe vary between 0 1 and 0 3 nm an inverse trend versus fluorescence suggests significant fe removal by plankton blooms vertical mixing and upwelling are the most important supply mechanisms of iron from deep waters to the upper surface mixed layer at lower latitude 42 s there is a distinct maximum of 0 6 0 7 nm in the 2000 3000 m depth range due to inflow of north atlantic deep water in one region 55 s elevated dissolved fe found in the surface mixed layer is ascribed to the recent deposition of aeolian dust originating from south america close to the antarctic continent there is an indication of fe supply in surface waters from icebergs in the deep waters there is a strong indication of a hydrothermal plume of dissolved fe and mn over the ridge in the bouvet region 52 56 s in the weddell gyre basin the dissolved fe in the deep water is 0 47 0 16 nm in the eastward flow at 56 62 s and is lower with a value of 0 34 0 14 nm in the westward flow at high 62 69 s latitude at the edge of the continental ice sheet on the prime meridian the continental margin of the antarctic continent appears to be lesser source of dissolved fe than in any other place in the world this is likely because it is unique in being overlain by the extending continental ice sheet that largely prevents biogeochemical cycling

particulate organic carbon fluxes to the ocean interior and factors controlling the biological pump a synthesis of global sediment trap programs since 1983 particulate organic carbon poc is vertically transported to the oceanic interior by aggregates and their ballasts mainly caco3 and biogenic opal with a smaller role for lithogenic aerosols through the mesopelagic zone diel migrating zooplankton communities effect vertical transport and remineralization of poc in the upper layers of the ocean below 1 5 km the presence of zooplankton is reduced and thus the aggregates travel mainly by gravitational transport we normalized the fluxes of poc caco3 and biogenic opal from data published on samples collected at 134 globally distributed bottom tethered time series sediment trap ts trap stations to annual mole fluxes at the mesopelagic bathypelagic boundary m b at 2 km and defined them as fm bcorg fm bcinorg and fm bsibio using this global data set we investigated 1 the geographic contrasts of poc export at m b and 2 the supply rate of co2 to the world mesopelagic water column fm bcorg varies from 25 pacific warm pool to 605 divergent arabian sea mmolc m 2 yr 1 fm bcinorg varies from 8 high latitude polar oceans or 15 pacific warm pool to 459 divergent arabian sea mmolc m 2 yr 1 and fm bsibio the most spatially temporally variable flux ranges from 6 north atlantic drift to 1118 pacific subarctic gyre mmolsi m 2 yr 1 the oceanic region exhibiting the highest poc flux over a significantly large region is the area of the north pacific boreal gyres where the average fm bcorg 213 fm bcinorg 126 and fm bsibio 578 mmol m 2 yr 1 fm bcorg and fm bcinorg are particularly high in large upwelling margins including the divergent arabian sea and off cape verde one of the data sets showing the lowest flux over a significant region basin is fm bcorg 39 fm bcinorg 69 and fm bsibio 22 mmol m 2 yr 1 in the north pacific subtropical tropical gyres pan atlantic average fluxes are similar except fm bsibio fluxes are even lower where corg cinorg and sibio cinorg are 1 defines the carbonate ocean and where these ratios are 1 defines the silica ocean the carbonate ocean occupies about 80 of the present world pelagic ocean between the two major oceanographic fronts the north pacific polar front and the antarctic polar front and the silica ocean is found on the polar sides of these fronts the total global annual fluxes of fm bcorg fm bcinorg and fm bsibio at m b calculated by parameterizations of the export flux data from 134 stations are surprisingly similar 36 2 33 8 and 34 6 teramol yr 1 120 112 and 114 mmol m 2 yr 1 respectively resulting in a near uniform binary ratio between the above three elements of about one the global ternary ratios estimated from 152 ts trap samples of the three elements are 35 32 33 from our global fm bcorg and a published model estimate of the global export production we estimate the regeneration rate of co2 through the mesopelagic zone by the biological pump is 441 teramolc yr 1 based on our global fm bcinorg and recently estimated global primary production of pic 36 86 teramolc yr 1 of pic is assumed to be dissolved within the upper 2 km of the water column

surface ocean variability at galapagos from 1936 1982 calibration of geochemical tracers in corals a variety of geochemical tracers has been developed in reef corals as a means of reconstructing the natural variability of the tropical surface ocean over wide ranging time frames the purpose of this paper is to calibrate the performance of five of these tracers in a modern coral colony over an extended period a 47 year growth interval 1936 1982 in a colony of pavona clavus taken from san cristobal island galapagos islands was sectioned into 187 quarterly intervals and analyzed for 18o 13o ba ca cd ca and mn ca the resulting time series are compared with eastern pacific sea surface temperatures one of few instrumental data bases available for calibration over this time period linear least squares regressions of four of the tracers 18o 13o ba ca cd ca against peruvian sst show highly significant correlations p 0 0001 over the annual biennial and enso 3 8 years frequency bands cross spectral comparisons show even stronger coherency with sst frequently accounting for 70 80 of the variance in these tracers these results as well as the phase relationships determined from the spectral analyses suggest that the coupling between sst and 18o and the nutrientlike tracers ba and cd is controlled principally by seasonal upwelling cycles and interannual interruptions of these cycles brought about by el nino and anti el nino phenomena an inverse relationship between sst and 13c has its primary origins in the co occurrence of the warm sst phase with high light levels during the first half of the calendar year the association with sunlight derives from the photosynthetic response of algal symbionts which results in fractionation of light and heavy carbon isotopes between soft tissues and caco3 skeleton the fifth tracer the transition metal mn exhibits poorer correlations against both sst and the other tracers slight shifts in phasing of the historical mn ca annual cycle suggest that the general water column distribution of this tracer which is the reverse of a nutrient may not be stable the erratic behavior of mn illustrates how complex hydrography near galapagos may influence tracers with diverse source signatures

a physically based 3 d model of ice cliff evolution over debris covered glaciers we use high resolution digital elevation models dems from unmanned aerial vehicle uav surveys to document the evolution of four ice cliffs on the debris covered tongue of lirung glacier nepal over one ablation season observations show that out of four cliffs three different patterns of evolution emerge i reclining cliffs that flatten during the ablation season ii stable cliffs that maintain a self similar geometry and iii growing cliffs expanding laterally we use the insights from this unique data set to develop a 3 d model of cliff backwasting and evolution that is validated against observations and an independent data set of volume losses the model includes ablation at the cliff surface driven by energy exchange with the atmosphere reburial of cliff cells by surrounding debris and the effect of adjacent ponds the cliff geometry is updated monthly to account for the modifications induced by each of those processes model results indicate that a major factor affecting the survival of steep cliffs is the coupling with ponded water at its base which prevents progressive flattening and possible disappearance of a cliff the radial growth observed at one cliff is explained by higher receipts of longwave and shortwave radiation calculated taking into account atmospheric fluxes shading and the emission of longwave radiation from debris surfaces the model is a clear step forward compared to existing static approaches that calculate atmospheric melt over an invariant cliff geometry and can be used for long term simulations of cliff evolution and to test existing hypotheses about cliffs survival

regulation of algal blooms in antarctic shelf waters by the release of iron from melting sea ice during summer 1995 96 we measured iron in the water column and conducted iron enrichment bottle incubation experiments at a station in the central ross sea 76 30 s 170 40 w first in the presence of melting sea ice and 17 days later in ice free conditions we observed a striking temporal change in mixed layer dissolved iron concentrations at this station from 0 72 2 3 nm with sea ice present to 0 16 0 17 nm in ice free conditions these changes were accompanied by a significant drawdown in macronutrients and an approximate doubling of algal diatom biomass our incubation experiments suggest that conditions were iron replete in the presence of sea ice and iron deficient in the absence of sea ice we surmise that bioavailable iron was released into seawater from the melting sea ice stimulating phytoplankton production and the biological removal of dissolved iron from the mixed layer until iron limited conditions developed these observations suggest that the episodic release of bioavailable iron from melting sea ice is an important factor regulating phytoplankton production particularly ice edge blooms in seasonally ice covered antarctic waters

moored sediment trap measurements of carbon export in the subantarctic and polar frontal zones of the southern ocean south of australia sediment trap moorings were deployed from september 21 1997 through february 21 1998 at three locations south of australia along 140 e at 47 s in the central subantarctic zone saz with traps at 1060 2050 and 3850 m depth at 51 s in the subantarctic front with one trap at 3080 m and at 54 s in the polar frontal zone pfz with traps at 830 and 1580 m particle fluxes were high at all the sites 18 32 g m 2 yr 1 total mass and 0 5 1 4 g organic carbon m 2 yr 1 at 1000 m assuming minimal flux outside the sampled summer period these values are similar to other southern ocean results and to the median estimated for the global ocean by lampitt and antia 1997 and emphasize that the southern ocean exports considerable carbon to the deep sea despite its high nutrient low chlorophyll characteristics the saz site was dominated by carbonate 50 of total mass and the pfz site by biogenic silica 50 of total mass both sites exhibited high export in spring and late summer with an intervening low flux period in december for the 153 day collection period particulate organic carbon export was somewhat higher in all the traps in the saz range 0 57 0 84 gc m 2 than in the pfz range 0 31 0 53 with an intermediate value observed at the saf 0 60 the fraction of surface organic carbon export estimated from seasonal nutrient depletion lourey and trull 2001 reaching 1000 m was indistinguishable in the saz and pfz despite different algal communities

contrasting patterns of early twenty first century glacier mass change in the himalayas glaciers are among the best terrestrial climate indicators an important water resource in mountains1 2 and a major contributor to global sea level rise3 4 in the hindu kush karakoram himalaya region hkkh a paucity of appropriate glacier data has prevented a comprehensive assessment of current regional mass balance5 however there are indirect evidences of a complex pattern of glacial responses5 8 in reaction to heterogeneous climate change signals9 here we provide the first coherent data set of detailed glacier thickness changes over the hkkh during 2003 2009 by combining satellite laser altimetry and a global elevation model in the eastern central and south western parts of the hkkh glacier wastage is widespread with regional thinning rates up to 0 66 0 09 m a 1 in the jammu kashmir region conversely in the karakoram glaciers are close to balance with only a slight thinning of 0 07 0 04 m a 1 regionally averaged thinning rates under debris mantled ice are similar to those of clean ice despite insulation by debris covers the 2003 2008 specific mass balance for our hkkh study region is 0 21 0 05 m a 1 water equivalent we significantly less negative than the global average of 0 7 m a 1 we for glaciers and ice caps4 10 this difference is mainly an effect of the balanced glacier mass budget in the karakoram the corresponding hkkh sea level contribution is 0 035 0 009 mm a 1 amounting to 1 of the present day sea level rise11 our 2003 2008 mass budget of 12 8 3 5 gt a 1 is more negative than recent satellite gravimetry based estimates of 5 6 gt a 1 over 2003 2010 ref 12 for the mountain catchments of the indus and ganges basins13 the glacier imbalance contributes 3 5 and 2 0 respectively to the annual average river discharge13 and up to 10 for the upper indus basin14

stable isotope geochemistry of corals from costa rica as proxy indicator of the el nino southern oscillation enso abstract we analyzed the 18 o and 13 c time series contained in coral skeletons collected from isla del cano costa rica that survived the 1982 1983 el nino warming event coral 18 o give a record of thermal histories with a precision of 0 5 c for this locality we have determined that the average w effect in the coral skeletons is equivalent to 33 of the skeletal 18 o range therefore if w effects are not compensated for the annual skeletal 18 o range displays a temperature range of 1 c lower than actual values the isotopic record of porites lobata skeletons shows simultaneous depletions in 18 o and 13 c at skeletal levels corresponding to 1983 coincident with the el nino southern oscillation enso event therefore the el nino event is not only recorded as negative 18 o anomalies in the skeleton suggesting the warming of ambient waters but also in the 13 c signal as negative anomalies indicating coral bleaching contrary to the predictions of the 13 c insolation model that the annual carbon isotope variation should be attenuated with depth in proportion to the decrease in light intensity variation with depth we found a clear trend where 13 c increases with depth coral bioenergetics which depends on both coral physiology and ecology may adequately explain the unexpected increase in 13 c range with depth without contradicting the seasonal character of 13 c variability with the solar irradiance cycle although some authors have determined the presence of hiatuses in the skeletal record due to severe stress and growth cessation in this study it has been found that skeletal growth was not seriously diminished during the el nino year of 1983 we attribute the good agreement of the 18 o record with the timing and magnitude of the el nino 1982 1983 warming event to the nature of the warming trend in the area as well as to some synergistic implications of coral tolerance to thermal stress

response of debris covered glaciers in the mount everest region to recent warming and implications for outburst flood hazards abstract in areas of high relief many glaciers have extensive covers of supraglacial debris in their ablation zones which alters both rates and spatial patterns of melting with important consequences for glacier response to climate change wastage of debris covered glaciers can be associated with the formation of large moraine dammed lakes posing risk of glacier lake outburst floods glofs in this paper we use observations of glaciers in the mount everest region to present an integrated view of debris covered glacier response to climate change which helps provide a long term perspective on evolving glof risks in recent decades debris covered glaciers in the everest region have been losing mass at a mean rate of 0 32 m yr 1 although in most cases there has been little or no change in terminus position mass loss occurs by 4 main processes 1 melting of clean ice close to glacier elas 2 melting beneath surface debris 3 melting of ice cliffs and calving around the margins of supraglacial ponds and 4 calving into deep proglacial lakes modelling of processes 1 and 2 shows that everest region glaciers typically have an inverted ablation gradient in their lower reaches due to the effects of a down glacier increase in debris thickness mass loss is therefore focused in the mid parts of glacier ablation zones causing localised surface lowering and a reduction in downglacier surface gradient which in turn reduce driving stress and glacier velocity so the lower ablation zones of many glaciers are now stagnant model results also indicate that increased summer temperatures have raised the altitude of the rain snow transition during the summer monsoon period reducing snow accumulation and ice flux to lower elevations as downwasting proceeds formerly efficient supraglacial and englacial drainage networks are broken up and supraglacial lakes form in hollows on the glacier surface ablation rates around supraglacial lakes are typically one or two orders of magnitude greater than sub debris melt rates so extensive lake formation accelerates overall rates of ice loss most supraglacial lakes are perched above hydrological base level and are susceptible to drainage if they become connected to the englacial drainage system speleological surveys of conduits show that large englacial voids can be created by drainage of warm lake waters along pre existing weaknesses in the ice roof collapses can open these voids up to the surface and commonly provide the nuclei of new lakes thus by influencing both lake drainage and formation englacial conduits exert a strong control on surface ablation rates an important threshold is crossed when downwasting glacier surfaces intersect the hydrological base level of the glacier base level lakes formed behind intact moraine dams can grow monotonically and in some cases can pose serious glof hazards glacier termini can evolve in different ways in response to the same climatic forcing so that potentially hazardous lakes will form in some situations but not others additionally the probability of a flood is not simply a function of lake volume but depends on the geometry and structure of the dam and possible trigger mechanisms such as ice or rockfalls into the lake satellite based measurements of glacier surface gradient and ice velocities allow probable future locations of base level lakes to be identified a base level lake has begun to grow rapidly on ngozumpa glacier west of mount everest and could attain a volume of 10 8 m 3 within the next 2 or 3 decades unless mitigation efforts are undertaken this lake could pose considerable glof hazard potential

a physically based model of the year round surface energy and mass balance of debris covered glaciers debris covered glaciers respond to atmospheric conditions in different ways from debris free glaciers due to the presence of debris at the surface during the ablation season and at the snow ice interface during the accumulation season understanding the response of debris covered glaciers to a variety of meteorological conditions in a physically sound manner is essential to quantify meltwater discharge and to predict their response to climate change to tackle this issue we developed the crocus deb model as an adaptation of the detailed snowpack model crocus to simulate the energy and mass balance of debris covered glaciers including periods when debris is covered by snow crocus deb was evaluated with data gathered during a field experiment using artificial debris covering the snowpack at col de porte france with very good results in terms of conductive heat flux both at the surface and at the interface between the debris and the underlying dense snow taken as a surrogate for ice with and without snow overlying the debris the model was also evaluated using field data from the debris covered glacier changri nup nepal himalaya this paper introduces the design of the model its performance and its ability to explore relationships between model parameters meteorological conditions and the critical debris thickness

internal accumulation on storglaciaren sweden in a multi layer snow model coupled to a distributed energy and mass balance model to investigate the internal accumulation on storglaciaren sweden we couple a multilayer snow model to a distributed energy and mass balance model the snow model describes the temperature density and water content evolution of the snow ice pack and includes the processes of percolation and refreezing of water the model is run for the period 9 may 2 september 1999 and validated against weather station and mass balance observations on the glacier the model performs reasonably well with an average summer mass balance for the location of stake observations of 1 56 m w e compared to 1 59 m w e observed however the amount of melt is overestimated in the higher parts of the accumulation area and underestimated in the lower parts of the ablation area the modelled mass balance is most sensitive to the albedo parameterization the chosen momentum and scalar roughness lengths and all parameters related to snowfall the modelled internal accumulation is 0 25 m w e which amounts to about 20 of the winter accumulation and results in a positive net balance for 1999 of 0 23 m w e the modelled internal accumulation is most sensitive to the initial subsurface temperature profile and the irreducible water content

transmission of solar radiation through clouds on melting glaciers a comparison of parameterizations and their impact on melt modelling we explore the robustness and transferability of parameterizations of cloud radiative forcing used in glacier melt models at two sites in the swiss alps we also look at the rationale behind some of the most commonly used approaches and explore the relationship between cloud transmittance and several standard meteorological variables the 2 m air temperature diurnal range is the best predictor of variations in cloud transmittance however linear and exponential parameterizations can only explain 30 50 of the observed variance in computed cloud transmittance factors we examine the impact of modelled cloud transmittance factors on both solar radiation and ablation rates computed with an enhanced temperature index model the melt model performance decreases when modelled radiation is used the reduction being due to an underestimation of incoming solar radiation on clear sky days the model works well under overcast conditions we also seek alternatives to the use of in situ ground data however outputs from an atmospheric model 2 2 km horizontal resolution do not seem to provide an alternative to the parameterizations of cloud radiative forcing based on observations of air temperature at glacier automatic weather stations conversely the correct definition of overcast conditions is important

equatorial carbonates an earth systems approach the hypothesis here is that an earth systems processes to products approach can be used to better develop predictive models for the recognition and assessment of under evaluated equatorial carbonate systems warm temperatures together with common clastic fresh water and nutrient influx as well as basinal settings in the equatorial tropics all have a major impact on carbonate deposition and diagenesis specific features of equatorial carbonate systems resulting from the combination of processes acting in the region include common occurrence of photoautotrophs and heterotrophs aragonitic and or calcitic dominant mineralogies lack of coated grains or aggregates common associations with clastics lack of associations with evaporites and diversity of platform types including oligophotic ones additional diagenetic characteristics include common micritization and bioerosion paucity of marine cements extensive vadose dissolution and concomitant phreatic cementation there is also significant replacement of aragonite by calcite in regions of meteoric groundwater flow common burial compaction and leaching as well as localized massive dolomitization via sea water or continental derived groundwater flow although equatorial carbonates fall into the warm water photozoan association many of the features described above are at odds with models derived from their warm water arid zone counterparts instead a range of the equatorial carbonate features show some similarities with those formed in cool waters and there have been difficulties separating carbonates from these two very different climatic regimes recommendations for the recognition of phanerozoic regional equatorial carbonate development are i a diversity of calcitic and or aragonitic photoautotrophs plus ii common elements of the heterozoan association plus iii independent for example isotopic evidence for warm temperatures 22 c additional indicators towards a humid equatorial setting are iv situation in appropriate palaeolatitudes v lack of association with sedimentary evaporites coated grain or aggregates and vi geochemical evidence for reduced marine salinity and or nutrient upwelling the aim is that this work will lead to greater awareness and understanding of equatorial carbonate systems and contribute to the development of globally predictive models to better understand past and likely future environmental change

backwasting rate on debris covered koxkar glacier tuomuer mountain china a physically based energy balance model with improved parameterization of solar radiation for a sloped ice surface has been developed to estimate the backwasting rate of an ice cliff in a debris covered area the model has been tested against observations between 5 august and 5 september 2008 on 38 ice cliffs in the debris covered area of koxkar glacier tuomuer mountain china we calculated that the energy balance model gave a good estimate of the backwasting rates with errors in the range 1 96 cm d 1 and root mean square errors of 0 99 cm d 1 errors arising from setting of surface albedo and turbulent flux parameterization were limited we found that shortwave radiation is the most important heat source for ice cliff ablation contributing about 76 of the total heat available for ice melt while the sensible heat flux provides nearly 24 of the total heat for ice cliff wastage the latent heat flux and net longwave radiation are comparatively small according to the model calculation the mean backwasting rate of ice cliffs in the debris covered area of koxkar glacier is estimated at 7 64 m a 1 when the winter ablation is neglected with this annual backwasting rate and given a mean slope angle of 46 48 the backwasting of ice cliffs produces about 1 60 10 6 m 3 of meltwater accounting for about 7 3 of the total melt runoff from the debris covered area

measurement and parameterization of aerodynamic roughness length variations at haut glacier d arolla switzerland spatial and temporal variations in aerodynamic roughness length z0 on haut glacier d arolla switzerland during the 1993 and 1994 ablation seasons are described based on measure ments of surface microtopography the validity of the microtopographic z0 measurements is established through comparison with independent vertical wind profile z0 measurements over melting snow slush and ice the z0 variations are explained through correlation and regression analyses using independent measurements of meteorological and surface variables and parameterizations are developed to calculate z0 variations for use in surface energy balance melt models several independent variables successfully explain snow z0 variation through their correlation with increasing surface roughness caused by ablation hollow formation during snow melt non linear parameterizations based on either accumulated melt or accumulated daily maximum temperatures since the most recent snowfall explain over 80 of snow z0 variation the z0 following a fresh snowfall on an ice surface is parameterized based on relationships with the underlying ice z0 snow depth and accumulated daily maximum temperatures none of the independent variables were able to successfully explain ice z0 variation although further comparative studies are needed the results lend strong support to the microtopo graphic technique of measuring z0 over melting glacier surfaces

aspect controls the survival of ice cliffs on debris covered glaciers supraglacial ice cliffs exist on debris covered glaciers worldwide but despite their importance as melt hot spots their life cycle is little understood early field observations had advanced a hypothesis of survival of north facing and disappearance of south facing cliffs which is central for predicting the contribution of cliffs to total glacier mass losses their role as windows of energy transfer suggests they may explain the anomalously high mass losses of debris covered glaciers in high mountain asia hma despite the insulating debris currently at the center of a debated controversy we use a 3d model of cliff evolution coupled to very high resolution topographic data to demonstrate that ice cliffs facing south in the northern hemisphere disappear within a few months due to enhanced solar radiation receipts and that aspect is the key control on cliffs evolution we reproduce continuous flattening of south facing cliffs a result of their vertical gradient of incoming solar radiation and sky view factor our results establish that only north facing cliffs are recurrent features and thus stable contributors to the melting of debris covered glaciers satellite observations and mass balance modeling confirms that few south facing cliffs of small size exist on the glaciers of langtang and their contribution to the glacier volume losses is very small 1 this has major implications for the mass balance of hma debris covered glaciers as it provides the basis for new parameterizations of cliff evolution and distribution to constrain volume losses in a region where glaciers are highly relevant as water sources for millions of people

growth and drainage of supraglacial lakes on debris mantled ngozumpa glacier khumbu himal nepal ablation of debris mantled glaciers in nepal has resulted in the formation of several potentially unstable moraine dammed lakes some of which constitute serious hazards ngozumpa glacier khumbu himal has undergone significant downwasting in recent decades and is believed to lie close to the threshold for moraine dammed lake formation the debris mantled ablation area of the glacier is studded with numerous supraglacial lakes the majority of which occupy closed basins with no perennial connections to the englacial drainage system perched lakes perched lakes can undergo rapid growth by subaerial and water line melting of exposed ice faces and calving subaerial and subaqueous melting beneath thick 1 m debris mantles is comparatively insignificant although lake expansion can contribute substantially to ablation of the glacier perched lakes cannot continue to grow indefinitely but are subject to rapid drainage once a connection is made to englacial conduits the level of one of the lakes on the ngozumpa however is controlled by the altitude of a spillway through the lateral moraine of the glacier this lake underwent only limited growth in the period 1998 2000 but is likely to experience monotonic growth if glacier mass balance continues to be negative

thickness estimation of supraglacial debris above ice cliff exposures using a high resolution digital surface model derived from terrestrial photography the thickness of supraglacial debris cover controls how it impacts the ablation rate of underlying glacier ice yet this quantity remains challenging to measure particularly at glacier scales we present a relatively straightforward and cost effective method to estimate debris thickness exposed above ice cliffs using simplified geometrical measurements from a high resolution digital surface model dsm derived from a terrestrial photographic survey and a structure from motion with multi view stereo workflow sfm mvs as the ice surface relief beneath the debris cover is unknown we assume it to be horizontal and provide error bounds based on characteristic ice surface slope at the visible debris ice interface debris thickness around the three sampled ice cliffs was highly variable interquartile range of 0 80 2 85 m and negatively skewed with a mean thickness of 2 08 0 68 m manual and high frequency radar determinations of debris thickness in the same area show similar thickness distributions but statistically different mean debris thickness due to local heterogeneity debris thickness values derived in this study all exceed estimates from satellite surface temperature inversions wider application of the method presented here would provide useful data for improving debris thickness approximations from satellite imagery

mass balance changes of the debris covered glaciers in the langtang himal nepal from 1974 to 1999 thick debris cover on glaciers can significantly reduce ice melt however several studies have suggested that debris covered glaciers in the himalaya might have lost mass at a rate similar to debris free glaciers we reconstruct elevation and mass changes for the debris covered glaciers of the upper langtang valley nepalese himalaya using a digital elevation model dem from 1974 stereo hexagon satellite data and the 2000 srtm shuttle radar topography mission dem uncertainties are high in the accumulation areas due to data gaps in the srtm and difficulties with delineation of the glacier borders even with these uncertainties we obtain thinning rates comparable to those of several other studies in the himalaya in particular we obtain a total mass balance for the investigated debris covered glaciers of the basin of 0 32 0 18 m w e a 1 however there are major spatial differences both between glaciers and within any single glacier exhibiting a very distinct nonlinear mass balance profile with elevation through analysis of surface velocities derived from landsat etm imagery we show that thinning occurs in areas of low velocity and low slope these areas are prone to a general dynamic decay of surface features and to the development of supraglacial lakes and ice cliffs which may be responsible for a considerable increase in overall glacier ablation

importance of longwave emissions from adjacent terrain on patterns of tropical glacier melt and recession tropical glaciers constitute an important source of water for downstream populations however our understanding of glacial melt processes is still limited one observed process that has not yet been quantified for tropical glaciers is the enhanced melt caused by the longwave emission transfer here we use high resolution surface temperatures obtained from the thermal infrared imagery of the cuchillacocha glacier in the cordillera blanca peru in june 2014 to calculate a margin longwave flux this longwave flux reaching the glacier margin from the adjacent exposed rock varies between 81 and 120 w m 2 daily this flux is incorporated into a physically based melt model to assess the net radiation budget at the modeled glacier margin the simulation results show an increase in the energy available for melt by an average of 106 w m 2 during the day when compared with the simulation where the lw margin flux is not accounted for this value represents an increase in ablation of 1 7 m at the glacier margin for the duration of the dry season this study suggests that including the quantification of the glacier margin longwave flux in physically based melt models results in an improved assessment of tropical glacier energy budget and meltwater generation

retreat rates of debris covered and debris free glaciers in the koshi river basin central himalayas from 1975 to 2010 debris covered glaciers are common in the himalayas and play a key role in understanding future regional water availability and management previous studies of regional glacial changes have often neglected debris covered glaciers or have mixed them with debris free glaciers in this study we generated a new glacier data set that includes debris covered and debris free glaciers to study the glacial surface area change in the koshi river basin in the central himalayas long time series landsat data were used to extract the glacier boundaries using automatic and manual classification methods the glacial area decreased by 10 4 from 1975 to 2010 at a rate of 0 30 a 1 with accelerated melting since 2000 0 47 a 1 small glaciers melted faster than large glaciers in terms of distinctive glacier types debris free glaciers shrank at a rate of 0 45 a 1 faster than debris covered glaciers 0 18 a 1 while debris covered glaciers larger than 5 0 km2 retreated at a rate faster than debris free glaciers of the same sized group we also studied the potential interactions between 222 supraglacial lakes and debris covered glaciers debris covered glaciers with glacial lakes melt faster than glaciers without lakes this study can improve our understanding of the differences in the changes between debris covered and debris free glaciers in the central himalayas and help evaluate water resource changes in the himalayas

spatial and temporal variability of air temperature on a melting glacier atmospheric controls extrapolation methods and their effect on melt modeling juncal norte glacier chile 1 temperature data from three automatic weather stations and twelve temperature loggers are used to investigate the spatiotemporal variability of temperature over a glacier its main atmospheric controls the suitability of extrapolation techniques and their effect on melt modeling we use data collected on juncal norte glacier central chile during one ablation season we examine temporal and spatial variability in lapse rates lrs together with alternative statistical interpolation methods the main control over the glacier thermal regime is the development of a katabatic boundary layer kbl katabatic wind occurs at night and in the morning and is eroded in the afternoon lrs reveal strong diurnal variability with steeper lrs during the day when the katabatic wind weakens and shallower lrs during the night and morning we suggest that temporally variable lrs should be used to account for the observed change they tend to be steeper than equivalent constant lrs and therefore result in a reduction in simulated melt compared to use of constant lrs when extrapolating from lower to higher elevations in addition to the temporal variability the temperature elevation relationship varies also in space differences are evident between local lrs and including such variability in melt modeling affects melt simulations extrapolation methods based on the spatial variability of the observations after removal of the elevation trend such as inverse distance weighting or kriging do not seem necessary for simulations of gridded temperature data over a glacier

highly variable aerodynamic roughness length z0 for a hummocky debris covered glacier the aerodynamic roughness length z0 is an essential parameter in surface energy balance studies but few literature values exist for debris covered glaciers we use microtopographic and aerodynamic methods to assess the spatial variability of z0 for lirung glacier nepal we apply structure from motion to produce digital elevation models for three nested domains five 1 m2 plots a 21 300 m2 surface depression and lower 550 000 m2 of the debris mantled tongue wind and temperature sensor towers were installed in the vicinity of the plots within the surface depression in october 2014 we calculate z0 according to a variety of transect based microtopographic parameterisations for each plot then develop a grid version of the algorithms by aggregating data from all transects this grid approach is applied to the surface depression dem to characterize z0 spatial variability the algorithms reproduce the same variability among transects and plots but z0 estimates vary by an order of magnitude between algorithms across the study depression results from different algorithms are strongly correlated using monin obukov similarity theory we derive z0 values from the meteorological data using different stability criteria we derive median values of z0 between 0 03 m and 0 05 m but with considerable uncertainty due to the glacier s complex topography considering estimates from these algorithms results suggest that z0 varies across lirung glacier between 0 005 m gravels to 0 5 m boulders future efforts should assess the importance of such variable z0 values in a distributed energy balance model

a grid based model of backwasting of supraglacial ice cliffs on debris covered glaciers ice cliffs might be partly responsible for the high mass losses of debris covered glaciers in the hindu kush karakoram himalaya region the few existing models of cliff backwasting are point scale models applied at few locations or assume cliffs to be planes with constant slope and aspect a major simplification given the complex surfaces of most cliffs we develop the first grid based model of cliff backwasting for two cliffs on debris covered lirung glacier nepal the model includes an improved representation of shortwave and longwave radiation and their interplay with the glacier topography shortwave radiation varies considerably across the two cliffs mostly due to direct radiation diffuse radiation is the major shortwave component as the direct component is strongly reduced by the cliffs aspect and slope through self shading incoming longwave radiation is higher than the total incoming shortwave flux due to radiation emitted by the surrounding terrain which is 25 of the incoming flux melt is highly variable in space suggesting that simple models provide inaccurate estimates of total melt volumes although only representing 0 09 of the glacier tongue area the total melt at the two cliffs over the measurement period is 2313 and 8282 m3 1 23 of the total melt simulated by a glacio hydrological model for the glacier s tongue

quantifying ice cliff evolution with multi temporal point clouds on the debris covered khumbu glacier nepal measurements of glacier ice cliff evolution are sparse but where they do exist they indicate that such areas of exposed ice contribute a disproportionate amount of melt to the glacier ablation budget we used structure from motion sfm photogrammetry with multi view stereo mvs to derive 3d point clouds for nine ice cliffs on khumbu glacier nepal in november 2015 may 2016 and october 2016 by differencing these clouds we could quantify the magnitude seasonality and spatial variability of ice cliff retreat mean retreat rates of 0 30 to 1 49 cm d 1 were observed during the winter interval november 2015 to may 2016 and 0 74 to 5 18 cm d 1 were observed during the summer may 2016 to october 2016 four ice cliffs which all featured supraglacial ponds persisted over the full study period in contrast ice cliffs without a pond or with a steep back slope degraded over the same period the rate of thermo erosional undercutting was over double that of subaerial retreat overall 3d topographic differencing allowed an improved process based understanding of cliff evolution and cliff pond coupling which will become increasingly important for monitoring and modelling the evolution of thinning debris covered glaciers

a 173 year stable isotope record from a tropical south pacific coral 0 we have generated a 173 year long time series a d 1806 to 1979 of changes in the 18 o and 13 c composition of a coral head platygyra lamellina to investigate environmental change in the climatologically sensitive region of the tropical south pacific little is known about decadal and centennial scale climate change at sea level in this region our coral is from near the south coast of espiritu santo island 15 s 167 e republic of vanuatu the stable isotope record from this coral is consistent with meteorological and oceanographic records during the period of overlap in the records 1964 1978 18 o values positively correlate with sst r 0 77 and 13 c values are highly coherent with rainfall r 0 82 at the annual cycle these relations suggest that the 18 o signal in this coral is a function of variations in sst and rainfall induced changes in sss whereas the 13 c signal may be related to rainfall and cloud cover modulation of photosynthesis in the coral 18 o and 13 c values are positively correlated over the entire length of the record r 0 65 a relation that is even stronger between 1806 and 1866 r 0 81 i e prior to the time of possible anthropogenic influence on the 13 c record because of the positive correlation between temperature and rainfall in this region we interpret the long term record of 18 o in terms of joint variations of these two variables the most significant cool dry excursion in the santo record occurs during the nineteenth century 1832 1866 and ends abruptly in 1866 with a change to modern values superimposed on this pattern is a slight 0 2 cooling drying toward the end of the twentieth century cross spectral analysis of the 18 o and 13 c records indicates a strong concentration of variance at the quasi biennial 2 years and el nino southern oscillation enso 4 5 years frequency bands in addition to a 15 year peak found also in global temperature records cross spectral analysis of coral isotope records from santo and the philippine sea indicate a concentration of variance at enso 4 5 years frequency bands however comparison of the santo coral isotope record with high latitude northern hemisphere temperature records indicates that the major cool dry excursion in the santo record 1832 1866 is not seen in the northern hemisphere record if verified in other tropical south pacific coral records the results have implications concerning the global scale of cooling for little ice age events

change of the enso related δ18o sst correlation from coral skeletons in northern south china sea a possible influence from the kuroshio current abstract chemical proxies are useful analogs for reconstructing physical properties of sea water such as sea surface temperature sst and sea surface salinity sss time series of these inferred properties would allow for reconstructions of past el nino southern oscillation enso events where no instrumental records exist in this study a monthly oxygen isotope record from a porites coral is used to explain how past enso events are recorded in the coral skeletons the sample covers a 12 year period and was collected from nanwan bay taiwan during el nino events the coral skeleton is shown to produce a 18o sst correlation with a slope of 0 12 0 04 c 1 during other times this value is significantly different with a slope of 0 21 0 04 c 1 coral that grew during el nino summers have 18o values which are enriched by 0 2 relative to other times a possible mechanism to explain this difference may be enhanced penetration of kuroshio current waters into the south china sea during summer the observed contrast in the correlation of 18o sst variability in this sample supports the influence of el nino in eastern asia

modelling ice cliff backwasting on a debris covered glacier in the nepalese himalaya ice cliffs have been identified as a reason for higher ablation rates on debris covered glaciers than are implied by the insulation effects of the debris this study aims to improve our understanding of cliff backwasting and the role of radiative fluxes in particular an energy balance model is forced with new data gathered in may and october 2013 on lirung glacier nepalese himalaya observations show substantial variability in melt between cliffs between locations on any cliff and between seasons using a high resolution digital elevation model we calculate longwave fluxes incident to the cliff from surrounding terrain and include the effect of local shading on shortwave radiation this is an advance over previous studies that made simplified assumptions on cliff geometry and radiative fluxes measured melt rates varied between 3 25 and 8 6cm d 1 in may and 0 18 and 1 34 cmd 1 in october model results reproduce the strong variability in space and time suggesting considerable differences in radiative fluxes over one cliff in october the model fails to reproduce stake readings probably due to the lack of a refreezing component disregarding local topography can lead to overestimation of melt at the point scale by up to 9

a physically based method for estimating supraglacial debris thickness from thermal band remote sensing data in order to account for the effects of debris cover in model scenarios of the response of glaciers to climate change and water resource planning it is important to know the distribution and thickness of supraglacial debris and to monitor its change over time previous attempts to map surface debris thickness using thermal band remote sensing have relied upon time specific empirical relationships between surface temperature and thickness limiting their general applicability in this paper we develop a physically based model that utilizes advanced spaceborne thermal emission and reflection radiometer aster thermal band remotely sensed imagery and is based on a solution of the energy balance at the debris surface the model is used to estimate debris thickness on miage glacier italy and is validated using field debris thickness measurements and a previously published debris thickness map the temporal transferability of the model is demonstrated through successful application to a separate aster image from a different year using reanalysis meteorological input data this model has the potential to be used for regional scale supraglacial debris thickness mapping and monitoring for debris up to at least 0 50 m thickness but improved understanding of the spatial patterns of air temperature aerodynamic roughness length and thermal properties across debriscovered glaciers is needed

spatial distribution of pco2 δo2 ar and dimethylsulfide dms in polynya waters and the sea ice zone of the amundsen sea antarctica we report the first simultaneous measurements of surface water pco2 biological oxygen saturation o2 ar and dimethylsulfide dms concentrations in polynya waters and the sea ice zone of the amundsen sea antarctica across our survey region we observed large spatial variability in surface water gas concentrations tied to strong gradients in hydrography and phytoplankton biomass variability in sea surface temperature and salinity was attributed to the interacting effects of surface ocean circulation and heat fluxes sea ice melt and the upwelling of relatively warm saline and nutrient rich modified circumpolar deep water phytoplankton biomass ranged from 1 g l 1 to 40 g l 1 chlorophyll a chl a with the highest values observed in regions of shallow mixed layer depths phytoplankton assemblages were dominated by the colonial haptophyte phaeocystis antarctica at most sampling stations with lesser abundances of diatoms found throughout the polynya and sea ice zone cryptophytes were abundant at a few stations along the continental shelf break across the open polynya waters and sea ice zone o2 ar ranged from 40 to 40 mean 8 6 pco2 ranged from 80 to 530 atm mean 250 atm and dms concentrations varied from 1 nm to 350 nm strong gradients in gas concentrations were observed over short i e 10 km spatial scales the distribution of pco2 and o2 ar across our survey transects reflected the balance between deep water entrainment and net community production with a significant imprint of air sea exchange chl a concentrations were significantly correlated to both pco2 and o2 ar and the slope of the o2 ar vs pco2 relationship was consistent with photosynthetic stoichiometry 1 25 mol o2 evolved per mol dic removed dms and chl a concentrations were also correlated in surface waters but the spatial distribution of dms was often uncoupled from pco2 and o2 ar likely due to complex microbial cycling processes sea surface temperature and salinity were related to surface gas concentrations through their effects on mixed layer depth and as tracers of upwelling during the time of our cruise the amundsen sea acted as an overall net sink for co2 mean sea air flux 15 9 mmol m 2 d 1 and a dms source mean sea air flux 23 1 mol m 2 d 1 sea air co2 and dms fluxes were more than 2 fold higher in open polynya waters relative to the overall cruise means simple calculations suggest that the amundsen sea contributes 5 of total southern ocean co2 fluxes and 1 of dms fluxes

vertical water mass mixing and plankton blooms recorded in skeletal stable carbon isotopes of a red sea coral the environmental interpretation of the 13c 12c variations in the skeletons of massive corals is still a matter of debate a 19 year seasonal skeletal 13c 12c record of a shallow water porites coral from the northern red sea gulf of aqaba documents interannual events of extraordinarily large plankton blooms indicated by anomalous 3c depletions in the coral skeleton these blooms are caused by deep vertical water mass mixing convectively driven in colder winters which results in increased supplies of nutrients to the surface waters the deep vertical mixings can sometimes be driven by the cooling occurring throughout the middle east after large tropical volcanic eruptions we therefore have evidence in our coral skeletal 13c 12c record for an indirect volcanic signal of the eruptions of e1 chich6n 1982 and mount pinatubo 1991 deep mixing induced 13c 12c variations of the dissolved inorganic carbon in the surface waters can be neglected at this location we therefore suggest that the 3c skeletal depletions can be best explained by changes in the coral s autotrophy heterotrophy diet through increased heterotrophic feeding on zooplankton during the blooms increased feeding on 3c depleted zooplankton or increased heterotrophy at the expense of autotrophy can both 3 result in a c depleted coral skeleton however this suggestion requires more testing if our conclusions are substantiated seasonal skeletal 3c r2c records of corals which change from autotrophy under normal conditions to increased heterotrophy during bloom events may be used as indicators of ocean paleoproductivity at interannual resolution available from no other source

rapid climate change in the north atlantic during the younger dryas recorded by deep sea corals research on global climate change has increasingly focused on rapid century scale and decadal changes one such climate shift the younger dryas cooling event1 took place during the last deglaciation from 13 000 to 11 700 years bp climate records from greenland ice cores and north atlantic sediment cores show high frequency fluctuations implying significant 5 c shifts in temperature at this time taking place within 50 100 years ref 2 the origin of the younger dryas has recently been attributed to a reduction or cessation of deep water production in the north atlantic and a concurrent lessening of the heat flux from low latitudes3 4 the role of intermediate waters 1 000 2 000 m depth is less certain however because climate proxies for this ocean reservoir are rare and ambiguous here we report on the use of a new climate archive deep sea corals from orphan knoll 1 600m depth in the northwestern atlantic ocean the oxygen isotope ratios in the coral skeletons accurately dated by the 230th 234u chronometric method change markedly coincident with the initiation of the younger dryas suggesting that there were profound changes in intermediate water circulation at this time

high resolution monitoring of himalayan glacier dynamics using unmanned aerial vehicles himalayan glacier tongues are commonly debris covered and they are an important source of melt water however they remain relatively unstudied because of the inaccessibility of the terrain and the difficulties in field work caused by the thick debris mantles observations of debris covered glaciers are therefore scarce and airborne remote sensing may bridge the gap between scarce field observations and coarse resolution space borne remote sensing in this study we deploy an unmanned aerial vehicle uav before and after the melt and monsoon season may and october 2013 over the debris covered tongue of the lirung glacier in nepal based on stereo imaging and the structure for motion algorithm we derive highly detailed ortho mosaics and digital elevation models dems which we geometrically correct using differential gps observations collected in the field based on dem differencing and manual feature tracking we derive the mass loss and the surface velocity of the glacier at a high spatial accuracy on average mass loss is limited and the surface velocity is very small however the spatial variability of melt rates is very high and ice cliffs and supra glacial ponds show mass losses that can be an order of magnitude higher than the average we suggest that future research should focus on the interaction between supra glacial ponds ice cliffs and englacial hydrology to further understand the dynamics of debris covered glaciers finally we conclude that uav deployment has large potential in glaciology and it may revolutionize methods currently applied in studying glacier surface features

the surface energy balance of an active ice covered volcano villarrica volcano southern chile the energy balance of bare snow and tephra covered ice near the glacier equilibrium line elevation on villarrica volcano southern chile was investigated during 2004 and 2005 combining meteorological surface temperature and ablation measurements with energy balance modelling a tephra thermal conductivity of 0 35 w m 1 k 1 and a critical tephra thickness of 0 1 m tephra windblown tephra impurities lowered snow albedo but increased snowmelt by only an estimated 0 28 m w e over the same period the net mass balance impact of supraglacial tephra at villarrica volcano is therefore positive as thick ash and lapilli mantle most of the glacier ablation zones probably reducing annual ablation by several metres w e in the accumulation seasons frequent melting events were recorded with modelled daily snowmelt rates of up to 50 mm w e

luminescence and density banding patterns in massive porites corals around the thai malay peninsula southeast asia we characterized the annual luminescent and skeletal density banding patterns in 51 massive porites corals from 15 reefs from six locations around the thai malay peninsula in southeast asia and explored the seasonal environmental cues drivers of band formation location specific recurrent annual luminescent banding patterns were found at all study locations with a brighter band occurring toward the end of the year october november december at five locations and in june one location annual density banding patterns could only be discerned at four locations and were categorized into those that formed a dense band commencing november december and those starting may june overall compared to luminescence variations in skeletal density provided a less clear signal for demarcation of annual growth increments seasonal variations in luminescence showed clearest relationships with salinity as a proxy for freshwater river runoff no convincing relationship between intra annual luminescence intensity and density variations was found which supports the notion that luminescent banding is due to inclusions of fluorophores into the coral skeleton rather than variations in skeletal architecture the relationships between seasonal density variations and significant wave height and rainfall suggest density banding in this region is likely related to wave energy or some other correlated environmental parameter s the large variability in skeletal banding patterns not only highlights the current relatively poor understanding of their nature and causes but also the need for replication in their interpretation especially in settings with complex seasonal hydrodynamic hydrological patterns such as those found around the thai malay peninsula

ice cliff dynamics in the everest region of the central himalaya the importance of ice cliffs for glacier scale ablation on debris covered glaciers is now widely recognised however a paucity of data exists to describe the spatio temporal distribution of ice cliffs in this study we analysed the position and geometry of 8229 ice cliffs and 5582 supraglacial ponds on 14 glaciers in the everest region between 2000 and 2015 we observed notable ice cliff and pond spatial coincidence on average across our study glaciers 77 of supraglacial pond area was associated with an adjacent ice cliff and 49 of ice cliffs featured an adjacent supraglacial pond the spatial density of ice cliffs was not directly related to glacier velocity but did peak within zones of active ice furthermore we found that ice cliff density was glacier specific temporally variable and was positively correlated with surface lowering and decreasing debris thickness for individual glaciers ice cliffs predominantly had a north facing commonly north westerly aspect which was independent of glacier flow direction thereby signifying a strong solar radiation control on cliff evolution independent field observations indicated that cliff morphology was related to aspect local debris thickness and presence of a supraglacial pond and highlighted the importance of surface runnel formation which acts as a preferential pathway for meltwater and debris fluxes overall by coupling remote sensing and in situ observations it has been possible to capture local and glacier scale ice cliff dynamics across 14 glaciers which is necessary if explicit parameterisation of ice cliffs in dynamic glacier models is to be achieved

object based analysis of unmanned aerial vehicle imagery to map and characterise surface features on a debris covered glacier debris covered glaciers in the himalaya may have spatially averaged rates of surface height change that are similar to those observed on bare ice glaciers despite the insulating effects of thick debris spatially heterogeneous melt patterns caused by the development and evolution of ice cliffs and supraglacial pond systems result in substantial mass losses over time however mechanisms controlling the formation and survival of cliffs and ponds remain largely unknown to study the distribution and characteristics of these surface features we deploy an unmanned aerial vehicle uav over a stretch of the debris covered langtang glacier nepal acquired images are processed into high resolution orthomosaics and elevation models with the structure from motion sfm photogrammetry algorithm ice cliffs and ponds are classified using object based image analysis obia and their morphology and spatial distribution are analysed and evaluated using object pixel and point cloud approaches results show that ice cliffs are predominantly north facing and larger ice cliffs are generally coupled with supraglacial ponds which may affect their evolution considerably the spatial distribution of ice cliffs indicates that they are more likely to form in areas where high strain rates are expected the spatial configuration of ponds over the entire tongue reveals high pond density near confluences possibly due to closure of conduits via transverse compression we conclude that the combination of obia and uav imagery is a valuable tool in the semi automatic and objective analysis of surface features on debris covered glaciers the technique may also have potential for upscaling to the use of spaceborne imagery and the use of uav derived point clouds to analyse ice cliff undercuts is promising

atmospheric and oceanic evidences of el nino southern oscillation events in the south central pacific ocean from coral stable isotopic records over the last 137 years we measured 18o and 13c in porites lutea collected in the moorea lagoon where the instrumental records show that an el nino southern oscillation enso event implies both a cloud cover decrease and a weak sea surface temperature sst increase two proxies allow an enso record to be reconstructed at moorea the annual 13c anomaly associated with the south pacific convergence zone motion and an annual 18o anomaly showing increased sst the frequency bands exhibited by the singular spectral analysis ssa and the multitaper method of the annual 18o and 13c records are centered on 2 5 and 5 2 years and 2 4 and 3 2 years respectively which are the main enso modes we used ssa to reconstruct enso events at moorea over the past 137 years results indicate that climate variability at this site is strongly affected by enso events

quantifying volume loss from ice cliffs on debris covered glaciers using high resolution terrestrial and aerial photogrammetry mass losses originating from supraglacial ice cliffs at the lower tongues of debris covered glaciers are a potentially large component of the mass balance but have rarely been quantified in this study we develop a method to estimate ice cliff volume losses based on high resolution topographic data derived from terrestrial and aerial photogrammetry we apply our method to six cliffs monitored in may and october 2013 and 2014 using four different topographic datasets collected over the debris covered lirung glacier of the nepalese himalayas during the monsoon the cliff mean backwasting rate was relatively consistent in 2013 3 8 0 3 cm w e d 1 and more heterogeneous among cliffs in 2014 3 1 0 7 cm w e d 1 and the geometric variations between cliffs are larger their mean backwasting rate is significantly lower in winter october 2013 may 2014 at 1 0 0 3 cm w e d 1 these results are consistent with estimates of cliff ablation from an energy balance model developed in a previous study the ice cliffs lose mass at rates six times higher than estimates of glacier wide melt under debris which seems to confirm that ice cliffs provide a large contribution to total glacier melt

elevation changes of glaciers revealed by multitemporal digital elevation models calibrated by gps survey in the khumbu region nepal himalaya 1992 2008 due to remoteness and high altitude only a few ground based glacier change studies are available in high mountain areas in the himalaya however digital elevation models based on remotely sensed data rs dems provide feasible opportunities to evaluate how fast himalayan glaciers are changing here we compute elevation changes in glacier surface total area 183 3 km in the khumbu region nepal himalaya for the period 1992 2008 using multitemporal rs dems and a map derived dem calibrated with differential gps survey data in 2007 elevation change is calculated by generating a weighted least squares linear regression model our method enables us to provide the distribution of uncertainty of the elevation change debris covered areas show large lowering rates the spatial distribution of elevation change shows that the different wastage features of the debris covered glaciers depend on their scale slope and the existence of glacial lakes the elevation changes of glaciers in the eastern khumbu region are in line with previous studies the regional average mass balance of 0 40 0 25mw e a for the period 1992 2008 is consistent with a global value of about 0 55mw e a for the period 1996 2005

rapid calculation of terrain parameters for radiation modeling from digital elevation data digital elevation models are widely used to calculate terrain parameters to determine incoming solar and longwave radiation for use in surface climate models interpretation of remote sensing data and parameters in hydrologic models because of the large number of points in an elevation grid fast algorithms are useful to save computation time a description is given of rapid methods for calculating slope and azimuth solar illumination angle horizons and view factors for radiation from sky and terrain calculation time is reduced by fast algorithms and lookup tables

supraglacial ice cliffs and ponds on debris covered glaciers spatio temporal distribution and characteristics ice cliffs and ponds on debris covered glaciers have received increased attention due to their role in amplifying local melt however very few studies have looked at these features on the catchment scale to determine their patterns and changes in space and time we have compiled a detailed inventory of cliffs and ponds in the langtang catchment central himalaya from six high resolution satellite orthoimages and dems between 2006 and 2015 and a historic orthophoto from 1974 cliffs cover between 1 4 0 4 in the dry and 3 4 0 9 in the wet seasons and ponds between 0 6 0 1 and 1 6 0 3 of the total debris covered tongues we find large variations between seasons as cliffs and ponds tend to grow in the wetter monsoon period but there is no obvious trend in total area over the study period the inventory further shows that cliffs are predominately north facing irrespective of the glacier flow direction both cliffs and ponds appear in higher densities several hundred metres from the terminus in areas where tributaries reach the main glacier tongue on the largest glacier in the catchment 10 of all cliffs and ponds persisted over nearly a decade

on the relationship between fronts of the antarctic circumpolar current and surface chlorophyll concentrations in the southern ocean 1 we reexamine the relationship between circulation bathymetry and surface chlorophyll in the southern ocean using new high resolution maps of the frontal structure of the antarctic circumpolar current acc derived from satellite altimetry the maps reveal that the acc consists of multiple filaments or jets by averaging surface chlorophyll measurements along streamlines we show that the fronts define the limits of zones with similar concentrations and seasonality of surface chlorophyll the overall pattern of surface chlorophyll is consistent with strongest upwelling of nutrient rich deep water south of the polar front pf however the distribution of chlorophyll in the southern ocean is concentrated in a number of persistent blooms observed downstream of islands and bathymetric features in contrast to previous studies we find little evidence that the fronts of the acc are associated with enhanced productivity at least where the fronts are distant from topography rather we find that most regions of elevated chlorophyll in the open southern ocean can be explained by upwelling of nutrients both macronutrients and micronutrients where the acc interacts with topography followed by downstream advection the upwelling is shown to be the consequence of the bottom pressure torque established by the large scale flow rather than being due to small scale instabilities of the jets the interaction of the flow with the topography therefore establishes both the large scale dynamical balance of the acc and determines the productivity of the open southern ocean

the dynamic response of the greenland and antarctic ice sheets to multiple century climatic warming new calculations were performed to investigate the combined response of the greenland and antarctic ice sheets to a range of climatic warming scenarios over the next millennium use was made of fully dynamic 3d thermomechanic ice sheet models which were coupled to a two dimensional climate model the experiments were initialized with simulations over the last two glacial cycles to estimate the present evolution and were subsequently forced with temperature scenarios resulting from greenhouse emission scenarios which assume equivalent co2 increases of two four and eight times the present 1990 a d value by the year 2130 a d and a stabilization after that the calculations brought to light that during the next century short term effect the background evolution trend would dominate the response of the antarctic ice sheet but would be negligible for the greenland ice sheet on that timescale the greenland and antarctic ice sheets would roughly balance one another for the middle scenario similar to the ipcc96 is92a scenario with respective contributions to the worldwide sea level stand on the order of about 610 cm on the longer term however both ice sheets would contribute positively to the worldwide sea level stand and the most important effect would come from melting on the greenland ice sheet sensitivity experiments highlighted the role of ice dynamics and the height massbalance feedback on the results it was found that ice dynamics cannot be neglected for the greenland ice sheet not even on a century timescale but becomes only important for antarctica on the longer term the latter is related to an increased outflow of ice into the ice shelves and to the grounding line retreat of the west antarctic ice sheet which are both found to be sensitive to basal melting below ice shelves and the effective viscosity of the ice shelves stretching parameters to their limits yielded a combined maximum rate of sea level rise of 85 cm century21 of which 60 cm would originate from the greenland ice sheet alone

modeling the refreezing of meltwater as superimposed ice on a high arctic glacier a comparison of approaches 1 the refreezing of meltwater is known to be a critical factor when assessing the mass balance state of glaciers in the high arctic several different models of this process are widely used in numerical glacier simulations but as yet no attempt has been made to compare these approaches or to assess their relative performance against field measurements such models are likely to include implicit calibrations which may prove to be invalid under conditions different from those for which they were constructed we test a selection of six refreezing algorithms taken from the literature against field measurements of net mass balance and superimposed ice formation made at a high arctic glacier running these models for 1971 2002 using daily meteorological data and forward until 2050 using a range of future scenarios for the climate of svalbard we are able to make the following conclusions concerning mass balance modeling 1 the choice of meltwater refreezing model has a significant impact on the calculated net mass balance of a glacier 2 three of the models tested could with suitable tuning simultaneously reproduce both superimposed ice quantities and net mass balance measurements within their respective bounds of uncertainty while the other three could not 3 in situations where the model can be tuned to field measurements indicative of mass balance future predictions of mass balance are largely independent of the specific meltwater refreezing model used

environmental significance of carbon and oxygen isotope ratios of banded corals from lakshadweep india abstract the stable isotope ratios 18o and 13c of the coral porites compressa from the lakshadweep islands eastern arabian sea preserve environmental parameters related to monsoon induced upwelling the oxygen isotopic ratios in p compressa record the seasonal drop in sea surface temperature sst during the monsoon season an earlier calibration of the coralline 18o with observed changes in sst is used to estimate past sst changes and to evaluate the relationship with upwelling and rainfall the seasonal variations in carbon isotope ratios seem to be controlled by photosynthesis of the algal symbiont which in turn is modulated by monsoon activities sedimentation sediment suspension water current and turbidity both 18o and 13c in this species do reflect the monsoon clearly

comparison of the meteorology and surface energy fluxes of debris free and debris covered glaciers in the southeastern tibetan plateau knowledge of debris free and debris covered glaciers is important for understanding the varying response of glaciers to climate change measurements at the debris free parlung no 4 glacier and the debris covered 24 k glacier in the southeastern tibetan plateau were carried out to compare the meteorology and surface energy fluxes and to understand the factors controlling the melting process the meteorological comparisons displayed temporally synchronous fluctuations in air temperature relative humidity and incoming longwave radiation l in but notable differences in precipitation incoming shortwave radiation s in and wind speed under the prevailing regional precipitation and debris conditions more l in 42 w m 2 was supplied from warmer and more humid air and more s in 58 w m 2 was absorbed at the 24 k glacier the relatively high energy supply led mainly to an increased energy output via turbulent heat fluxes and outgoing longwave radiation rather than glacier melting beneath the thick debris the sensitivity experiment showed that melt rates were sensitive to energy supply at debris thicknesses similar to 10 cm in contrast energy supply to the parlung no 4 glacier mainly resulted in snow ice melting the magnitude of which was significantly influenced by energy supplied by s in and the sensible heat flux

assessing ice cliff backwasting and its contribution to total ablation of debris covered miage glacier mont blanc massif italy continuous surface debris cover strongly reduces the ablation of glaciers but high melt rates may occur at ice cliffs that are too steep to hold debris this study assesses the contribution of ice cliff backwasting to total ablation of miage glacier mont blanc massif italy in 2010 and 2011 based on field measurements physical melt models and mapping of ice cliffs using a high resolution 1 m digital elevation model dem short term model calculations closely match the measured melt rates a model sensitivity analysis indicates that the effects of cliff slope and albedo are more important for ablation than enhanced longwave incidence from sun warmed debris or reduced turbulent fluxes at sheltered cliff bases analysis of the dem indicates that ice cliffs account for at most 1 3 of the 1 m pixels in the glacier s debris covered zone but application of a distributed model indicates that ice cliffs account for 7 4 of total ablation we conclude that ice cliffs make an important contribution to the ablation of debris covered glaciers even when their spatial extent is very small

ground penetrating radar measurements of debris thickness on lirung glacier nepal m m is funded by nerc dtp grant number ne l002507 1 receives case funding from reynolds international ltd and was provided travel support by the jesus college doctoral research fund i w was funded by the bb roberts fund university travel fund and st catharine s college research fund equipment gpr and dgps was provided under nerc geophysical equipment facility grant number 1014

fluorescent bands in massive corals record centuries of coastal rainfall massive coral colonies on the great barrier reef grow outwards at 5 25 mm yr 1 ref 1 skeletal density varies seasonally in all massive corals from the great barrier reef and an exact temporal record of growth can be obtained by x radiography of appropriately cut sections of the colony2 3 environmental influences on coral growth have been described from such analyses4 6 this is the first report from the skeletons of massive corals of yellow green fluorescent bands which appear under long wave uv light such fluorescence is confined to corals growing within 20 km of the shore and is not present in massive corals from mid and outer shelf reefs of the central great barrier reef region the timing width and intensity of the fluorescent bands correlate strongly with summer monsoonal rainfall and coastal runoff large colonies several centuries old can provide long records of the strength and periodicity of terrestrial runoff to the tropical nearshore environment such records are potentially important to climatology meteorology agriculture civil engineering and management of the great barrier reef

refined energy balance modelling of a supraglacial pond langtang khola nepal supraglacial ponds on debris covered glaciers present a mechanism of atmosphere glacier energy transfer that is poorly studied and only conceptually included in mass balance studies of debris covered glaciers this research advances previous efforts to develop a model of mass and energy balance for supraglacial ponds by applying a free convection approach to account for energy exchanges at the subaqueous bare ice surfaces we develop the model using field data from a pond on lirung glacier nepal that was monitored during the 2013 and 2014 monsoon periods sensitivity testing is performed for several key parameters and alternative melt algorithms are compared with the model the pond acts as a significant recipient of energy for the glacier system and actively participates in the glacier s hydrologic system during the monsoon melt rates are 2 4 cm d 1 total of 98 5 m3 over the study period for bare ice in contact with the pond and 1 mm d 1 total of 10 6 m3 for the saturated debris zone the majority of absorbed atmospheric energy leaves the pond system through englacial conduits delivering sufficient energy to melt 2612m3 additional ice over the study period 38 4 m3 d 1 such melting might be expected to lead to subsidence of the glacier surface supraglacial ponds efficiently convey atmospheric energy to the glacier s interior and rapidly promote the downwasting process

slight mass gain of karakoram glaciers in the early twenty first century the mass balance of hindu kush karakoram himalaya glaciers has been debated partly because of a severe lack of observations from the region an analysis of the regional mass balance of karakoram glaciers by comparison of digital elevation models from 1999 to 2008 reveals a small glacier mass gain in the area

spatial seasonal and interannual variability of supraglacial ponds in the langtang valley of nepal 1999 2013 supraglacial ponds play a key role in absorbing atmospheric energy and directing it to the ice of debris covered glaciers but the spatial and temporal distribution of these features is not well documented we analyse 172 landsat tm etm scenes for the period 1999 2013 to identify thawed supraglacial ponds for the debris covered tongues of five glaciers in the langtang valley of nepal we apply an advanced atmospheric correction routine landcor 6s and use band ratio and image morphological techniques to identify ponds and validate our results with 2 5 m cartosat 1 observations we then characterize the spatial seasonal and interannual patterns of ponds we find high variability in pond incidence between glaciers may october means of 0 08 1 69 of debris area with ponds most frequent in zones of low surface gradient and velocity the ponds show pronounced seasonality appearing in the pre monsoon as snow melts peaking at the monsoon onset at 2 of debris covered area then declining in the post monsoon as ponds drain or freeze ponds are highly recurrent and persistent with 40 5 of pond locations occurring for multiple years rather than a trend in pond cover over the study period we find high interannual variability for each glacier after controlling for seasonality

an enhanced temperature index glacier melt model including the shortwave radiation balance development and testing for haut glacier d arolla switzerland an enhanced temperature index glacier melt model incorporating incoming shortwave radiation and albedo is presented the model is an attempt to combine the high temporal resolution and accuracy of physically based melt models with the lower data requirements and computational simplicity of empirical melt models represented by the degree day method and its variants the model is run with both measured and modelled radiation data to test its applicability to glaciers with differing data availability five automatic weather stations were established on haut glacier d arolla switzerland between may and september 2001 reference surface melt rates were calculated using a physically based energy balance melt model the performance of the enhanced temperature index model was tested at each of the four validation stations by comparing predicted hourly melt rates with reference melt rates predictions made with three other temperature index models were evaluated in the same way for comparison the enhanced temperature index model offers significant improvements over the other temperature index models and accounts for 90 95 of the variation in the reference melt rate the improvement is lower but still significant when the model is forced by modelled shortwave radiation data thus offering a better alternative to existing models that require only temperature data input

variability of air temperature over a debris covered glacier in the nepalese himalaya estimates of melt from debris covered glaciers require distributed estimates of meteorological variables and air temperature in particular meteorological data are scarce for this environment and spatial variability of temperature over debris is poorly understood based on multiple measurements of air and surface temperature from three ablation seasons 2012 14 we investigate the variability of temperature over lirung glacier nepal in order to reveal how air temperature is affected by the debris cover and improve ways to extrapolate it we investigate how much on glacier temperature deviates from that predicted from a valley lapse rate lr analyse on glacier lrs and test regression models of air temperature and surface temperature air temperature over the debris covered glacier tongue is much higher than what a valley lr would prescribe so an extrapolation from off glacier stations is not applicable an on glacier lr is clearly defined at night with strong correlation but not during the day when the warming debris disrupts the elevation control an alternative to derive daytime air temperature is to use a relationship between air and surface temperature as previously suggested we find strong variability during daytime that should be accounted for if these regressions are used for temperature extrapolation

air temperature variability in a high elevation himalayan catchment air temperature is a key control of processes affecting snow and glaciers in high elevation catchments including melt snowfall and sublimation it is therefore a key input variable to models of land surface atmosphere interaction despite this importance its spatial variability is poorly understood and simple assumptions are made to extrapolate it from point observations to the catchment scale we use a dataset of 2 75 years of air temperature measurements from may 2012 to november 2014 at a network of up to 27 locations in the langtang river nepal catchment to investigate air temperature seasonality and consistency between years we use observations from high elevations and from the easternmost section of the basin to corroborate previous findings of shallow lapse rates seasonal variability is strong with shallowest lapse rates during the monsoon season diurnal variability is also strong and should be taken into account since processes such as melt have a pronounced diurnal variability use of seasonal lapse rates seems crucial for glacio hydrological modelling but seasonal lapse rates seem stable over the 2 3 years investigated lateral variability at transects across valley is high and dominated by aspect with south facing sites being warmer than north facing sites and deviations from the fitted lapse rates of up to several degrees local factors e g topographic shading can reduce or enhance this effect the interplay of radiation aspect and elevation should be further investigated with high elevation transects

coastal southern ocean a strong anthropogenic co2 sink 1 large scale estimates of the southern ocean co2 sink do not adequately resolve the fluxes associated with antarctic continental shelves using a mechanistic three dimensional biogeochemical model of the ross sea we show that antarctic shelf waters are a strong sink for co2 due to high biological productivity intense winds high ventilation rates and extensive winter sea ice cover net primary production npp in these waters is 0 055 pg c yr 1 some of this carbon sinks to depth driving an influx of co2 of 20 50 g c m 2 yr 1 although currently unaccounted for the total atmospheric co2 sink on the ross sea continental shelf of 0 013 pg c yr 1 is equivalent to 27 of the most recent estimate of the co2 sink for the entire southern ocean given these results these and other highly productive waters around the antarctic continent need to be included in future budgets of anthropogenic co2