bluuebunny/crossref_metadata_2025 huggingface dataset:
Alkenone-based temperature patterns along the eastern South Pacific Coastal Ocean: the effect of upwelling and advection on the sedimentary alkenone unsaturation-index (U37K')
Authors: Placencia J. A. , Garcés-Vargas J. , Lange C. B. , Hebbeln D.
Published: April 2010

Abstract. We report that the sedimentary record of alkenone unsaturation-index (U37K') in the eastern South Pacific displays a wide range of temperatures, in response to sea surface temperature (SST), as well as nutrient concentrations. The U37K' inshore-offshore trend shows low-correlation with SSTs at many transitional sites (50–200 km offshore), and in one oligotrophic coastal site (~20° S). In contrast, in open-ocean sites SSTs play the expected dominant role. The latitudinal trend shows that nitrate, phosphate and/or temperature affect distinctively the U37K', suggesting progressive high-impacts in areas with permanent nutrient-stress conditions (~20° S), which is consistent with previous experiments. In contrast, this impact is slightly and not observable in transitional and open-ocean areas, respectively, where the coupling between offshore propagation of mesoscale eddies and upwelling filaments supply additional chlorophyll/nutrient. This study is a first field approximation to the impacts of thermal/non-thermal factors over the unsaturation-index in eastern Boundary Current systems, which would help in future temperature reconstructions.
VOC emissions from dry leaf litter and their dependence on temperature
Authors: Derendorp L. , Holzinger R. , Wishkerman A. , Keppler F. , Röckmann T.
Published: April 2010

Abstract. Emissions of several volatile organic compounds (VOCs) from dry leaf litter at temperatures in the range 20–100 °C are reported for different plant species. The emission rates of ethane, ethene, propane, propene, n-pentane and methyl chloride increase exponentially with temperature and follow the Arrhenius relation. Emission rates up to 650 ng/gdw/h were observed for hydrocarbons at 70 °C, while for methyl chloride emission rates up to 18 μg/gdw/h were observed at this temperature. The emissions are of abiotic origin, which is indicated by activation energies higher than 50 kJ/mol. The emission of VOCs from dry leaf litter decreases in time, due to depletion of the precursor reservoirs. At low temperatures (20–30 °C) the decrease is very slow, but at higher temperatures (80–100 °C) it is noticeable on a timescale of hours. Our results show that hydrocarbons can be produced in the leaf, but the production requires oxygen. Emissions of methyl chloride from dry leaves can be significant for the global budget of methyl chloride.
A timescale analysis of the Northern Hemisphere temperature response to volcanic and solar forcing
Authors: Weber S. L.
Published: April 2010

Abstract. The Northern Hemisphere temperature response to volcanic and solar forcing in the time interval 1000–1850 AD is studied using first a set of simulations with an intermediate-complexity climate model, driven by reconstructed forcings. Results are then compared with those obtained from the seven high-resolution reconstructed temperature records for the last millenium that are at present available. Focus of the analysis is on the timescale dependence of the response. Results between the model and the proxy-based reconstructions are remarkably consistent. The response to solar forcing is found to equilibrate at interdecadal timescales, reaching an equilibrium value for the regression of 0.2–0.3°C per W/m2. The time interval between volcanic eruptions is typically shorter than the dissipation timescale of the climate system, so that the response to volcanic forcing never equilibrates. As a result, the regression on the volcanic forcing is always lower than the equilibrium value and goes to zero for the longest temporal scales. The trends over the pre-anthropogenic period are found to be relatively large in all reconstructed temperature records, given the trends in the reconstructed forcing and the equilibrium value for the regression. This is at variance with a recent claim that reconstructed temperature records underestimate climatic variations at multi-centennial timescales.
Synoptic climate change as a driver of late Quaternary glaciations in the mid-latitudes of the Southern Hemisphere
Authors: Rother H. , Shulmeister J.
Published: April 2010

Abstract. The relative timing of late Quaternary glacial advances in mid-latitude (40-55° S) mountain belts of the Southern Hemisphere (SH) has become a critical focus in the debate on global climate teleconnections. On the basis of glacial data from New Zealand (NZ) and southern South America it has been argued that interhemispheric synchrony or asynchrony of Quaternary glacial events is due to Northern Hemisphere (NH) forcing of SH climate through either the ocean or atmosphere systems. Here we present a glacial snow-mass balance model that demonstrates that large scale glaciation in the temperate and hyperhumid Southern Alps of New Zealand can be generated with moderate cooling. This is because the rapid conversion of precipitation from rainfall to snowfall drives massive ice accumulation at small thermal changes (1-4°C). Our model is consistent with recent paleo-environmental reconstructions showing that glacial advances in New Zealand during the Last Glacial Maximum (LGM) and the Last Glacial Interglacial Transition (LGIT) occurred under very moderate cooling. We suggest that such moderate cooling could be generated by changes in synoptic climatology, specifically through enhanced regional flow of moist westerly air masses. Our results imply that NH climate forcing may not have been the exclusive driver of Quaternary glaciations in New Zealand and that synoptic style climate variations are a better explanation for at least some late Quaternary glacial events, in particular during the LGIT (e.g. Younger Dryas and/or Antarctic Cold Reversal).
Effect of land albedo, CO2, orography, and oceanic heat transport on extreme climates
Authors: Romanova V. , Lohmann G. , Grosfeld K.
Published: April 2010

Abstract. Using an atmospheric general circulation model of intermediate complexity coupled to a sea ice – slab ocean model, we perform a number of sensitivity experiments under present-day orbital conditions and geographical distribution to assess the possibility that land albedo, atmospheric CO2, orography and oceanic heat transport may cause an ice-covered Earth. Changing only one boundary or initial condition, the model produces solutions with at least some ice-free oceans in the low latitudes. Using some combination of these forcing parameters, a full Earth's glaciation is obtained. We find that the most significant factor leading to an ice-covered Earth is the high land albedo in combination with initial temperatures set equal to the freezing point. Oceanic heat transport and orography play only a minor role for the climate state. Extremely low concentrations of CO2 also appear to be insufficient to provoke a runaway ice-albedo feedback, but the strong deviations in surface air temperatures in the Northern Hemisphere point to the existence of a strong nonlinearity in the system. Finally, we argue that the initial condition determines whether the system can go into a completely ice covered state, indicating multiple equilibria, a feature known from simple energy balance models.
New constraints on the gas age-ice age difference along the EPICA ice cores, 0–50 kyr
Authors: Loulergue L. , Parrenin F. , Blunier T. , Barnola J.-M. , Spahni R. , Schilt A. , Raisbeck G. , Chappellaz J.
Published: April 2010

Abstract. Gas is trapped in polar ice sheets at ~50–120 m below the surface and is therefore younger than the surrounding ice. Firn densification models are used to evaluate this ice age-gas age difference (Δage) in the past. However, such models need to be validated by data, in particular for periods colder than present day on the East Antarctic plateau. Here we bring new constraints to test a firn densification model applied to the EPICA Dome C (EDC) site for the last 50 kyr, by linking the EDC ice core to the EPICA Dronning Maud Land (EDML) ice core, both in the ice phase (using volcanic horizons) and in the gas phase (using rapid methane variations). We also use the structured 10Be peak, occurring 41 kyr before present (BP) and due to the low geomagnetic field associated with the Laschamp event, to experimentally estimate the Δage during this event. Our results seem to reveal an overestimate of the Δage by the firn densification model during the last glacial period at EDC. Tests with different accumulation rates and temperature scenarios do not entirely resolve this discrepancy. Although the exact reasons for the Δage overestimate at the two EPICA sites remain unknown at this stage, we conclude that current densification model simulations have deficits under glacial climatic conditions. Whatever the cause of the Δage overestimate, our finding suggests that the phase relationship between CO2 and EDC temperature previously inferred for the start of the last deglaciation (lag of CO2 by 800±600 yr) seems to be overestimated.
LGM and Late Glacial glacier advances in the Cordillera Real and Cochabamba (Bolivia) deduced from 10Be surface exposure dating
Authors: Zech R. , Kull Ch. , Kubik P. W. , Veit H.
Published: April 2010

Abstract. Surface exposure dating (SED) is an innovative tool already being widely applied for moraine dating and for Late Quaternary glacier and climate reconstruction. Here we present exposure ages of 28 boulders from the Cordillera Real and the Cordillera Cochabamba, Bolivia. Our results indicate that the local Last Glacial Maximum (LGM) in the Eastern Cordilleras occurred at ~22–25 ka and was thus synchronous to the global temperature minimum. We were also able to date several Late Glacial moraines to ~11–13 ka, which likely document lower temperatures and increased precipitation ("Coipasa" humid phase). Additionally, we recognize the existence of older Late Glacial moraines re-calculated to ~15 ka from published cosmogenic nuclide data. Those may coincide with the cold Heinrich 1 event in the North Atlantic region and the pronounced "Tauca" humid phase. We conclude that (i) exposure ages in the tropical Andes may have been overestimated so far due to methodological uncertainties, and (ii) although precipitation plays an important role for glacier mass balances in the tropical Andes, it becomes the dominant forcing for glaciation only in the drier and thus more precipitation-sensitive regions farther west and south.
Orbital forcings of the Earth’s climate in wavelet domain
Authors: Glushkov A. V. , Khokhlov V. N. , Loboda N. S. , Rusov V. D. , Vaschenko V. N.
Published: April 2010

Abstract. We examine two paleoclimate proxy records – the temperature differences from the Antarctic Vostok ice core and the composite δ18O record from three sites (V19-30, ODP 677, and ODP 846) – in order to search for indications of orbital forcings. We demonstrate that the non-decimated wavelet transform is an appropriate tool for investigating temporarily changing spectral properties of records. Our results indicate that abrupt climate warmings with cyclicity of ~100 kiloyears during the last 400 kiloyears were caused by the combined unidirectional influences of three orbital parameters and the eccentricity can be considered as a modulator defining transitions from the Ice Ages to the periods of comparative warmings. Non-decimated wavelet transform avails discovering the possible part played in climate change by the eccentricity-forced variations. Up to approximately 1.7 million years BP, the influence of this variations of eccentricity appears in increasing for almost all local maxima of δ18O. Since the ~1.7 million years BP, minor and significant maxima alternated and this not affected as much the variations of δ18O.
Modelling ocean circulation, climate and oxygen isotopes in the ocean over the last 120 000 years
Authors: Marsh R. , Smith M. P. L. M. , Rohling E. J. , Lunt D. J. , Lenton T. M. , Williamson M. S. , Yool A.
Published: April 2010

Abstract. A new Earth System Model of Intermediate Complexity, GENIE-1, is used to simulate the most recent glacial-interglacial cycle by prescribing orbital forcing, atmospheric CO2 concentration, and the time evolution of ice sheet extent and orography. A series of experiments investigates uncertainty in the amplitude, frequency and location of prescribed meltwater pulses (MWPs) associated with Heinrich events in the North Atlantic and layers enriched in ice rafted debris around Antarctica. Associated with each MWP is a flux into the ocean of very light glacial oxygen isotope ratios, which serve as a tracer of the melt water. Additionally accounted for are temperature-related changes in the fractionation of stable oxygen isotopes between water and calcite. Modelled forwards from 120 000 years ago, simulated oxygen isotope records can thus be directly compared with measurements in calcite taken from International Marine Global Change Study (IMAGES) and Ocean Drilling Program (ODP) sediment cores at three locations representative of the North and South Atlantic, and the South Pacific. During the period of simulation corresponding to Marine Isotope Stage 3, the best agreement between the simulated oxygen isotope record in the North Atlantic and core measurements is found in the experiment that includes MWPs around Antarctica as well as into the North Atlantic. This challenges previous assumptions about the dominant role of northern ice sheets in glacial sea-level variability.
Anthropogenic effects on subsurface temperature in Bangkok
Authors: Taniguchi M.
Published: April 2010

Abstract. Subsurface temperatures in Bangkok, where population and density increase rapidly, were analyzed to evaluate the effects of surface warming due to urbanization. The magnitude of surface warming evaluated from subsurface temperature in Bangkok was 1.7°C which agreed with meteorological data during the last 50 years. The depth apart from steady thermal gradient, which shows an indicator of the magnitude of surface warming due to additional heat from urbanization, was deeper at the center of the city than in the suburb areas of Bangkok. In order to separate surface warming effects into global warming effect and urbanization effect, analyses of subsurface temperature have been done depending on the distance from the city center. The results show that the expansion of urbanization in Bangkok reaches up to 80 km from the city center.
Potential imprint of Spörer and Maunder solar minima on coral skeleton carbon isotopes
Authors: Ourbak T. , Malaizé B. , Corrège T.
Published: April 2010

Abstract. Despite being routinely measured with δ18O in corals, records of δ13C are seldom presented in paleoceanographic studies. Numerous factors influence the biologically-mediated fractionation of carbon isotopes during skeletogenesis, resulting in a complex behaviour of this tracer. Here we present a long coral δ13C series, dating back to 1475, and showing the potential impact of solar activity. We note a significant decrease of δ13C during the Spörer and Maunder minima. We argue for a change in metabolical processes, from an autotrophical pattern to a more heterotrophical mode of feeding guided by change in sun irradiation. In addition, nearby volcanic eruptions might also have an impact and cause δ13C shifts, depending on the dust load associated with the eruption. Following previous work, we advocate the systematic presentation of δ13C vs. δ18O plots in coral studies to identify whether isotopic fractionation might have been affected by change in mode of feeding.
Two modes of glacial climate during the late stage 5 identified in Greenland ice core records
Authors: Siggaard-Andersen M.-L. , Ditlevsen P. D. , Walløe Hansen A. , Johnsen S. J.
Published: April 2010

Abstract. From a detailed analysis of marine and terrestrial aerosol tracers in the NGRIP ice core we identified two distinct glacial atmospheric flow patterns. The climate transition from Marine Isotope Stage 5 (MIS 5) to MIS 4, at approximately 75 kyr BP, marks a shift between two different atmospheric flow regimes. Before this transition, during MIS 5d-a, the state of atmospheric flow was alternating between the two modes of different flow patterns, while a more persistent flow pattern was prevailing through the glacial period afterwards. These changes are accompanied by strong changes in an independent Greenland ice core proxy, namely the deuterium excess from the GRIP ice core, reflecting changes in the hydrological cycle and moisture source temperatures as well. The changes in atmospheric flow pattern are correlated with changed extent of ice-rafted detritus (IRD) deposition in the North Atlantic, indicating that the state of the atmospheric flow was highly sensitive to the waxing and waning of the Laurentide ice sheet.
New constraints on the gas age-ice age difference along the EPICA ice cores, 0–50 kyr
Authors: Loulergue L. , Parrenin F. , Blunier T. , Barnola J.-M. , Spahni R. , Schilt A. , Raisbeck G. , Chappellaz J.
Published: April 2010

Abstract. Gas is trapped in polar ice sheets at ~50–120 m below the surface and is therefore younger than the surrounding ice. Firn densification models are used to evaluate this ice age-gas age difference (Δage) in the past. However, such models are not well tested on low accumulation and cold sites of the East Antarctic plateau, especially for periods with different climatic conditions. Here we bring new constraints to test a firn densification model applied to the EPICA Dome C (EDC) site for the last 50 kyr, by linking the EDC ice core to the EPICA Dronning Maud Land (EDML) ice core, both in the ice phase (using volcanic horizons) and in the gas phase (using rapid methane variations). We use the structured 10Be peak, occurring 41 kyr before present (BP) and due to the low geomagnetic field associated with the Laschamp event, to experimentally estimate the Δage and Δdepth during this event. It allows us to evaluate the model and to link together climatic archives from EDC and EDML to NorthGRIP (Greenland). Our results reveal an overestimate of the Δage by the firn densification model during the last glacial period at EDC. Tests with different accumulation rates and temperature scenarios do not entirely resolve this discrepancy. Our finding suggests that the phase relationship between CO2 and EDC temperature inferred at the start of the last deglaciation (lag of CO2 by 800±600 yr) is overestimated and that the CO2 increase could well have been in phase or slightly leading the temperature increase at EDC.
Were last glacial climate events simultaneous between Greenland and western Europe?
Authors: Blaauw M. , Wohlfarth B. , Christen J. A. , Ampel L. , Veres D. , Hughen K. A. , Preusser F. , Svensson A.
Published: April 2010

Abstract. During the last glacial period, several large abrupt climate fluctuations took place on the Greenland ice cap and elsewhere. Often these Dansgaard/Oeschger events are assumed to have been synchronous, and then used as tie-points to link chronologies between the proxy archives. However, if temporally separate events are lumped into one illusionary event, climatic interpretations of the tuned events will obviously be flawed. Here, we compare Dansgaard/Oeschger-type events in a well-dated record from south-eastern France with those in Greenland ice cores. Instead of assuming simultaneous climate events between both archives, we keep their age models independent. Even these well-dated archives possess large chronological uncertainties, that prevent us from inferring synchronous climate events at decadal to multi-centennial time scales. If possible, tuning of proxy archives should be avoided.
Influence of orbital forcing on the seasonality and regionality of the Asian Summer monsoon precipitation
Authors: Hori M. E. , Abe M. , Yasunari T. , Kitoh A.
Published: April 2010

Abstract. The response of Asian monsoon precipitation to contrasting orbital parameters is simulated using the MRI-CGCM climate model. Results show that for the 125 kya B. P. experiment, a large continental heating due to obliquity forcing is apparent and accounts for the strengthened cross equatorial flow, stronger monsoon westerly over the Arabian Sea, and an enhanced precipitation over the Indian subcontinent. For the 115 kya B. P. experiment, while the monsoon westerly becomes weaker in the Arabian Sea, the overall strength of the monsoon westerly becomes stronger in the Bay of Bengal. This eastward extension of the monsoon westerly converges with the equatorial trade wind to give rise to an increased precipitation over the maritime continent and Indochina peninsula. Such increase in precipitation is accompanied with an earlier onset of the Asian monsoon, and an earlier warming of the tropical SST due to precessional forcing. It is concluded that while the obliquity forcing creates the baseline land-sea contrast which maintains the Asian monsoon westerly, when such forcing is comparably weaker, the Indian monsoon is diminished and the precessional forcing becomes more dominating to create a distinct earlier warming of the tropical SST which leads to an earlier onset of the maritime monsoon over the western Pacific. This study implies that even under weaker insolation forcing, the precessional signal may act to enhance certain regional precipitation and onset timing of the Asian monsoon.
Eliminating the "divergence problem" at Alaska's northern treeline
Authors: Wilmking M. , Singh J.
Published: April 2010

Abstract. Recently, an increasing off-set between tree-ring based temperature reconstructions and measured temperatures at high latitudes has been reported, the so called "divergence problem" (here "divergence effect"). This "divergence effect" seriously questions the validity of tree-ring based climate reconstructions, since it seems to violate the assumption of a stable response of trees to changing climate over time. In this study we eliminated the "divergence effect" in northern Alaska by careful selection of individual trees with consistently significant positive relationships with climate (17% of sample) and successfully attempted a divergence-free climate reconstruction using this sub-set. However, the majority of trees (83%) did not adhere to the uniformitarian principle as usually applied in dendroclimatology. Our results thus support the notion, that factors acting on an individual tree basis are the primary causes for the "divergence effect" (at least in northern Alaska). Neither different detrending methods nor factors acting on larger scales such as global dimming or an increase in UV-B radiation could explain our results. Our results also highlight the necessity to adapt the methods of paleoreconstruction using tree rings to account for non-stable climate growth relationships as these are found in the vast majority of sampled trees and seem to be the norm rather than the exception.
Synchronous variations of precipitation and temperature at Lake Qinghai, NE Tibetan Plateau during the past 800 years and their relations to solar activity: evidence from Li/Ca ratios and δ18O values of ostracod shells
Authors: Zhu Z. , Chen J. , Li J. , Zeng Y. , Li J. , Wang J. , Qi L.
Published: April 2010

Abstract. Variations of precipitation and temperature at Lake Qinghai, NE Tibetan Plateau on decadal scales during the past 800 years were reconstructed based on the oxygen isotope values and Li/Ca ratios from ostracod shells of the single species Eucypris inflata. Higher temperature relates to lower Li/Ca ratios; higher precipitation relates to lower δ18O values, and vice versa. The good correlation between Li/Ca ratios and δ18O values of ostracod shells indicates that temperature variations corresponded well with precipitation variations on decadal scales during the past 800 years. Variations of precipitation and temperature are synchronous with variations of solar activity reconstructed from the atmospheric 14C concentration in tree rings and the 10Be concentration in ice cores. These findings suggest that, on decadal scales solar activity may be responsible for the synchronous variations of precipitation and temperature at Lake Qinghai, NE Tibetan Plateau during the past 800 years. Keywords: Precipitation variations; Temperature variations; Eucypris inflata; Li/Ca; δ18O; Synchronous variations; Lake Qinghai; Solar activity.
Strong indications for nonlinear dynamics during Dansgaard-Oeschger events
Authors: Braun H.
Published: April 2010

Abstract. Many climate records show the occurrence of large amplitude (10–15 K), millennial-scale warming events during glacial times, the Dansgaard-Oeschger (DO) events. So far these events have almost exclusively been investigated by means of linear time series analysis. The scope of this paper is to test if the assumption of linearity is fulfilled during DO events. By means of a surrogate-based Monte Carlo method, I here demonstrate that the 60 000-year long δ18O-record from the NGRIP ice core from Greenland allows to reject the null hypothesis of linearity beyond any reasonable level of doubt. Instead, the ice core record supports the interpretation that the events represent regime switches between different states of operation of glacial climate. As a conclusion, future studies on DO events should focus on the development and the application of more adequate (i.e., nonlinear) methods of time series analysis.
Refining error estimates for a millennial temperature reconstruction
Authors: Juckes M. N.
Published: April 2010

Abstract. The statistical uncertainties in a 1000 year Northern Hemisphere mean temperature reconstruction obtained from 15 proxy chronologies are examined in detail by analysing the range of estimates obtained from all possible subsets of the proxy collection with up to 6 proxies omitted. The study is motivated in part by the large range of recently published reconstructions in the 15th and 16th centuries. The uncertainty estimates support the conclusions of the 3rd and 4th Intergovernmental Panel on Climate Change (IPCC) assessment reports concerning the likelihood that temperatures at the end of the 20th century were likely (greater than 66% confidence) to have been exceptional. It is also shown that the last ten years to date have been warmer than any decade of the past millennium with 95% confidence.
Astronomical forcing and mathematical theory of glacial-interglacial cycles
Authors: Kislov A. V.
Published: April 2010

Abstract. There are three important features of a proxy time series recorded during the Late Pleistocene. They are: 1) 100 000-year cycle as a dominant control of global glacial-interglacials through the late Quaternary, 2) fluctuations with periods of about 40 and 20 thousand years (their contribution to dispersion is no more than 20%), 3) ''Red-noise'' behavior of the time series. Direct influence of the insolation change created by fluctuations of the eccentricity is too weak to cause the observed 100 000-year climate fluctuations. Therefore, other mechanisms of such a rhythm are proposed. On the basis of the equation of the heat budget, the equation describing dynamics of zonally averaged temperature is developed. Various combinations of terms of this equation are discussed. They present a linear response to the Milankovitch periodicity, the Langeven stochastic equation, the equation of delay oscillator, the stochastic equation of spontaneous transitions, and the equation of stochastic resonance. Orbitally-induced changes in the solar energy flux received by the Earth play an important role as a mechanism starting process of climate changes which is supported and intensified by different feedbacks within the climate system. Positive anomalies of solar radiation serve as a mechanism causing reorganization of the climate only in rare cases when inclination of Earth axis of rotation increases and, simultaneously, perihelion takes place during the summer time (for the Northern Hemisphere).
Western equatorial African forest-savanna mosaics: a legacy of late Holocene climatic change?
Authors: Ngomanda A. , Chepstow-Lusty A. , Makaya M. , Favier C. , Schevin P. , Maley J. , Fontugne M. , Oslisly R. , Jolly D.
Published: April 2010

Abstract. Past vegetation and climate changes reconstructed using two pollen records from Lakes Maridor and Nguène, Gabon, provide new insights into the environmental history of western equatorial African rainforests during the last 4500 cal yr BP. The Lake Maridor pollen record indicates that the coastal savannas of western equatorial Africa did not exist during the mid-Holocene and instead the region was covered by evergreen rainforests. In the Lake Nguène pollen record, a rapid decline of hygrophilous evergreen rainforest occurred around 4000 cal yr BP, synchronously with grassland expansion around Lake Maridor. The establishment of coastal savannas in Gabon suggests decreasing humidity at the onset of the late Holocene. The marked reduction in evergreen rainforest and subsequent savanna expansion was associated with the colonization of secondary forests dominated by the palm, Elaeis guineensis, in the coastal region and the shrub, Alchornea cordifolia, further inland. A return to wetter climatic conditions from about 1400 cal yr BP led to the renewed spread of evergreen rainforest inland, whereas a forest-savanna mosaic still persists in the coastal region. There is no evidence to suggest that the major environmental changes observed are driven by human impact.
How to treat climate evolution in the assessment of the long-term safety of disposal facilities for radioactive waste: examples from Belgium
Authors: Van Geet M. , De Craen M. , Mallants D. , Wemaere I. , Wouters L. , Cool W.
Published: April 2010

Abstract. In order to protect man and the environment, long-lasting, passive solutions are needed for the different categories of radioactive waste. In Belgium, three main categories of conditioned radioactive waste (termed A, B and C) are defined by radiological and thermal power criteria. It is expected that Category A waste – low and intermediate level short-lived waste – will be disposed in a near-surface facility, whereas Category B and C wastes – high-level and other long-lived radioactive waste – will be disposed in a deep geological repository. In both cases, the long-term safety of a given disposal facility is evaluated. Different scenarios and assessment cases are developed illustrating the range of possibilities for the evolution and performance of a disposal system without trying to predict its precise behaviour. Within these scenarios, the evolution of the climate will play a major role as the time scales of the evaluation and long term climate evolution overlap. In case of a near-surface facility (Category A waste), ONDRAF/NIRAS is considering the conclusions of the IPCC, demonstrating that a global warming is nearly unavoidable. The consequences of such a global warming and the longer term evolutions on the evolution of the near-surface facility are considered. In case of a geological repository, in which much longer time frames are considered, even larger uncertainties exist in the various climate models. Therefore, the robustness of the geological disposal system towards the possible results of a spectrum of potential climate changes and their time of occurrence will be evaluated. The results of climate modelling and knowledge of past climate changes will merely be used as guidance of the extremes of climate changes to be considered and their consequences.
Individual and combined effects of ice sheets and precession on MIS-13 climate
Authors: Yin Q. Z. , Berger A. , Crucifix M.
Published: April 2010

Abstract. Simulations with an Earth System Model of Intermediate Complexity are made to investigate the role of insolation and the size of ice sheets on the regional and global climate for marine isotope stage (MIS) 13. The astronomical forcing is selected at two dates with opposite precession, one when Northern Hemisphere summer (NHS) occurs at perihelion (at 506 ka BP) and the other when it occurs at aphelion (at 495 ka BP). Experiments with five different volumes of the Eurasian and North American ice sheets (ranging from 0 to the Last Glacial Maximum one) are done under these two astronomical conditions. When NHS is at perihelion, the Earth is warmer, the seasonal contrast in Northern (Southern) Hemisphere is larger (smaller) and summer precipitation in Northern Hemisphere monsoon regions is more abundant than when it is at aphelion. The global cooling due to the ice sheets is mainly related to the ice sheet area, little to their height. The regional cooling and warming anomalies caused by the ice sheets get intensified with increasing ice sheet size. The cooling is different whether the NHS occurs at aphelion or at perihelion. Precipitation over different monsoon regions responds differently to the size of the ice sheets. Over North Africa, the ice sheets always reduce precipitation, larger the size less the precipitation. Over East China, when NHS is at perihelion, the ice sheets reinforce the summer precipitation whatever their sizes. But when NHS is at aphelion, there is a threshold in the ice volume beyond which the ice sheets start to reduce the precipitation over East China. This underlies the importance of insolation in shaping the ice sheet impact on the precipitation over the East Asian Summer Monsoon (EASM) region.
Surface circulation patterns and the pathways of sea surface carbon dioxide (CO2) off northern Chile (~27.5° S) between 30 and 10 kyr BP: global and/or local forcing?
Authors: Placencia J. A. , Harada N. , Torres R. , Lange C. B. , Hebbeln D.
Published: April 2010

Abstract. We present a reconstruction of past changes in partial pressure of CO2 (pCO2) from northern Chile (~27° S), between 10 and 30 kyr BP, based on carbon isotope composition of C37:2-alkenone. The high-pCO2 during the entire time series indicates that northern Chile upwelling system has been a permanent source of CO2 to the atmosphere. The multiproxy reconstruction suggests that the CO2 outgassing and sequestration pathways were modulated by local and global mechanisms. During global glacial conditions, an enhanced coastal upwelling forcing resulted in high-availability of deep water macronutrients and a CO2-supersaturated water column, which combined with high-inputs of iron from the continent, intensified the carbon sequestration pathway of the biological pump, through diatom biomass export. During the deglacial, a decrease in the upwelling forcing, an increment in water column stability and reduced continental inputs of iron are consistent with a larger role of calcifying organisms in the plankton assemblage in terms of carbon sequestration pathway through the carbonate system.
Last-glacial to postglacial climate formation in the continental interior inferred from multi-proxy records of Lake Hovsgol, Mongolia
Authors: Minoura K. , Sugawara D. , Kawai T.
Published: April 2010

Abstract. Knowledge of the evolution of arboreal forests is necessary to interpret the cause of climate formation in intracontinental regions. Paleoproxy records of sediment cores from Lake Hovsgol, Mongolia show that watershed conditions have fluctuated widely during the last 30 ka because of changing orbital parameters. Termination of glacial cooling and the subsequent prevalence of deglacial warming were consequences of solar forcing. Arboreal forests exerted an important influence on the atmospheric moisture cycle at high latitudes. Air pressure decreased because of raised humidity from water vapor penetration into inland regions that occurred along with summer monsoons. Data showing utilization of solar energy are necessary for establishing climate conditions. Atmospheric warming under increased insolation caused a shift of the monsoon limit to the north, amplifying the summer moisture supply to the watershed. That amplification engendered the appearance of the maximum vegetation in the Hovsgol drainage basin at the beginning of the Holocene. The retreat of arboreal forests that occurred along with decreased solar energy shrank the humidification-vegetation feedback loop, thereby decreasing the atmospheric humidity. The consequently lowered vapor pressure contributed to the incursion of cool air masses from the north.
Micro-components survey of residential indoor water consumption in Chiang Mai
Authors: Otaki Y. , Otaki M. , Pengchai P. , Ohta Y. , Aramaki T.
Published: April 2010

Abstract. The direct measurement of the micro-components of water consumption (i.e., consumption by each residential activity, such as toilet-, laundry-, bath-, and kitchen-use), both in the dry season and in the rainy season, was conducted in Chiang Mai, Thailand. It was expected that rainfall differences between the dry and rainy season would influence awareness for water resources so that water consumption in the dry season would be smaller than that in the rainy season. In addition, it was examined whether the differences in water resources such as public waterworks or non-public waterworks (i.e., community waterworks, mountainous water and groundwater), affected the amount of water use. A small-sized accumulative water meter was developed for measurement. This survey provides important information for water demand estimations and water supply planning in middle-developed countries where water consumption is expected to increase in future.
Importance of demand modelling in network water quality models: a review
Authors: Blokker E. J. M. , Vreeburg J. H. G. , Buchberger S. G. , van Dijk J. C.
Published: April 2010

Abstract. Today, there is a growing interest in network water quality modelling. The water quality issues of interest relate to both dissolved and particulate substances. For dissolved substances the main interest is in residual chlorine and (microbiological) contaminant propagation; for particulate substances it is in sediment leading to discolouration. There is a strong influence of flows and velocities on transport, mixing, production and decay of these substances in the network. This imposes a different approach to demand modelling which is reviewed in this article. For the large diameter lines that comprise the transport portion of a typical municipal pipe system, a skeletonised network model with a top-down approach of demand pattern allocation, a hydraulic time step of 1 h, and a pure advection-reaction water quality model will usually suffice. For the smaller diameter lines that comprise the distribution portion of a municipal pipe system, an all-pipes network model with a bottom-up approach of demand pattern allocation, a hydraulic time step of 1 min or less, and a water quality model that considers dispersion and transients may be needed. Demand models that provide stochastic residential demands per individual home and on a one-second time scale are available. A stochastic demands based network water quality model needs to be developed and validated with field measurements. Such a model will be probabilistic in nature and will offer a new perspective for assessing water quality in the drinking water distribution system.
Arsenic in drinking water: a worldwide water quality concern for water supply companies
Authors: van Halem D. , Bakker S. A. , Amy G. L. , van Dijk J. C.
Published: April 2010

Abstract. For more than a decade it has been known that shallow tube wells in Bangladesh are frequently contaminated with arsenic concentrations at a level that is harmful to human health. By now it is clear that a disaster of an unheard magnitude is going on: the World Health Organization has estimated that long-term exposure to arsenic in groundwater, at concentrations over 500 μg L−1, causes death in 1 in 10 adults. Other studies show that problems with arsenic in groundwater/drinking water occur in many more countries worldwide, such as in the USA and China. In Europe the focus on arsenic problems is currently confined to countries with high arsenic levels in their groundwater, such as Serbia, Hungary and Italy. In most other European countries, the naturally occurring arsenic concentrations are mostly lower than the European drinking water standard of 10 μg L−1. However, from the literature review presented in this paper, it is concluded that at this level health risks cannot be excluded. As consumers in European countries expect the drinking water to be of impeccable quality, it is recommended that water supply companies optimize arsenic removal to a level of <1 μg L−1, which is technically feasible.
Technical Note: Community of bacteria attached on the PVDF MF membrane surface fouled from drinking water treatment, in Seoul, Korea
Authors: Chon K. , Chon K. , Chang J.-S. , Oh H. , Lee E. , Cho J.
Published: April 2010

Abstract. Alpha, beta, and gamma proteobacteria comprise approximately 68, 16, and 7% of all identified bacteria. In this study, bacterial communities that had fouled polyvinylidene fluoride microfiltration membranes, which are used for drinking water treatment, over an 18 month period were analyzed using the 16s rRNA gene clone library method. The alpha, beta, and gamma proteobacteria were composed of mainly Bradyrhizobium and Rhodopseudomonas, Ralstonia, and Legionella, respectively. The presence of a relatively high amount of alpha proteobacteria was due to the oligotrophic condition of the drinking water source, the Han River, tested in this specific case study. The second most prominent bacteria community was the beta proteobacteria, which are typically found in a freshwater environment. This finding supports the notion that the drinking water source was relatively clean. Analyses of the organic foulants indicated that they were most likely from extra cellular polymers and/or cell fractured chemicals from bacteria or micro-organisms, as identified using organic characterizing tools, including 3-D fluorescence excitation-emission matrix and Fourier transform IR analyses.
Development of a predictive model to determine micropollutant removal using granular activated carbon
Authors: de Ridder D. J. , McConville M. , Verliefde A. R. D. , van der Aa L. T. J. , Heijman S. G. J. , Verberk J. Q. J. C. , Rietveld L. C. , van Dijk J. C.
Published: April 2010

Abstract. The occurrence of organic micropollutants in drinking water and its sources has opened up a field of study related to monitoring concentration levels in water sources, evaluating their toxicity and estimating their removal in drinking water treatment processes. Because a large number of organic micropollutants is currently present (although in relatively low concentrations) in drinking water sources, a method should be developed to select which micropollutants has to be evaluated with priority. In this paper, a screening model is presented that can predict solute removal by activated carbon, in ultrapure water and in natural water. Solute removal prediction is based on a combination of solute hydrophobicity (expressed as log D, the pH corrected log Kow), solute charge and the carbon dose. Solute molecular weight was also considered as model input parameter, but this solute property appeared to relate insufficiently to solute removal. Removal of negatively charged solutes by preloaded activated carbon was reduced while the removal of positively charged solutes was increased, compared with freshly regenerated activated carbon. Differences in charged solute removal by freshly regenerated activated carbon were small, indicating that charge interactions are an important mechanism in adsorption onto preloaded carbon. The predicted solute removal was within 20 removal-% deviation of experimentally measured values for most solutes.
Impact of decreasing water demand on bank filtration in Saxony, Germany
Authors: Grischek T. , Schoenheinz D. , Syhre C. , Saupe K.
Published: April 2010

Abstract. Bank filtration has been of great importance to the drinking water supply in Germany for many decades. The water quality of pumped raw water from bank filtration sites depends to a high degree on the water quality of the infiltrating surface water and the landside groundwater, the mixed portion of both, as well as the flow and transport conditions in the aquifer. Following the improvement of river water quality and a drastic decrease in water demand during the last 20 years in Germany, the influence of landside groundwater quality has become more important for the raw water quality of waterworks relying on bank filtration. The hydrogeologic analysis of three bank filtration sites in Saxony and the management of abstraction rates and well operation in response to fluctuating water demand are discussed.
Importance of demand modelling in network water quality models: a review
Authors: Blokker E. J. M. , Vreeburg J. H. G. , Buchberger S. G. , van Dijk J. C.
Published: April 2010

Abstract. Today, there is a growing interest in network water quality modelling. The water quality issues of interest relate to both dissolved and particulate substances, with the main interest in residual chlorine and (microbiological) contaminant propagation, respectively in sediment leading to discolouration. There is a strong influence of flows and velocities on transport, mixing, production and decay of these substances in the network. This imposes a different approach to demand modelling which is reviewed in this article. For transport systems the current hydraulic models suffice; for the more detailed distribution system a network water quality model is needed that is based on short time scale demands that considers the effect of dispersion and transients. Demand models that provide stochastic residential demands per individual home and on a one-second time scale are available. A stochastic demands based network water quality model needs to be developed and validated with field measurements. Such a model will be probabilistic in nature and will offer a new perspective for assessing water quality in the DWDS.
Method development for arsenic analysis by modification in spectrphotometric technique
Authors: Tahir M. A. , Rasheed H. , Malana A.
Published: April 2010

Abstract. Arsenic is a non-metallic constituent, present naturally in groundwater due to some minerals and rocks. Arsenic is not geologically uncommon and occurs in natural water as arsenate and arsenite. Additionally, arsenic may occur from industrial discharges or insecticide application. World Health Organization (WHO) and Pakistan Standard Quality Control Authority have recommended a permissible limit of 10 ppb for arsenic in drinking water. The arsenic at lower concentrations can be determined in water by using high tech instruments like Atomic Absorption Spectrometer (hydride generation). The arsenic concentration at low limits of 1 ppb could not be determined easily with simple spectrophotometric technique. Therefore, Spectrphotometric technique using the silver diethyldithiocarbamate was modified to achieve the better results, up to the extent of 1 ppb arsenic concentration.
Hydraulic modelling of drinking water treatment plant operations
Authors: Worm G. I. M. , Mesman G. A. M. , van Schagen K. M. , Borger K. J. , Rietveld L. C.
Published: April 2010

Abstract. For a drinking water treatment plant simulation, water quality models, a hydraulic model, a process-control model, an object model, data management, training and decision-support features and a graphic user interface have been integrated. The integration of a hydraulic model in the simulator is necessary to correctly determine the division of flows over the plant's lanes and, thus, the flow through the individual treatment units, based on valve positions and pump speeds. The flow through a unit is one of the most important parameters in terms of a unit's effectiveness. In the present paper, a new EPAnet library is presented with the typical hydraulic elements for drinking water treatment processes. Using this library, a hydraulic model was set up and validated for the drinking water treatment plant Harderbroek.