recent glacier decline in the kerguelen islands 49 s 69 e derived from modeling field observations and satellite data the retreat of glaciers in the kerguelen islands 49 s 69 e and their associated climatic causes have been analyzed using field data and moderate resolution imaging spectroradiometer modis satellite images to validate a positive degree day pdd model forced by data from local meteorological stations mass balance measurements made during recent field campaigns on the largest glacier of the cook ice cap were compared to data from the early 1970s providing a 40 year view of the differences in the spatial distribution of surface mass balance smb to obtain additional regional data for the validation of our models we analyzed modis images 2000 2012 to determine if our model was capable of reproducing variations in the transient snow line the pdd model correctly simulated the variations in the snow line the spatial variations in the smb and its trend with elevation yet current smb values diverge from their classic linear representation with elevation and stake data at high altitudes now display more negative smb values than expected by analyzing modis albedo we observed that these values are caused by the disappearance of snow and associated feedback on melt rates in addition certain parts of ampere glacier could not be reproduced by the surface energy balance model because of overaccumulation due to wind deposition finally the modis data field data and our models suggest that the acceleration of glacier wastage in kerguelen is due to reduced net accumulation and an associated rise in the snow line since the 1970s

regionally differentiated contribution of mountain glaciers and ice caps to future sea level rise the contribution to sea level rise from mountain glaciers and ice caps has grown over the past decades a projection of their melting during the twenty first century based on temperature and precipitation projections from ten climate models suggests that by 2100 these glaciers will lose about 21 of their total global volume

the effect of paleotopography on lithic distribution and facies associations of small volume ignimbrites the wtt cupa roccamonfina volcano italy abstract the distribution of lithic clasts within two trachytic small volume pumiceous ignimbrites are described from the quaternary white trachytic tuff cupa formation of roccamonfina volcano italy the ignimbrites show a downslope grading of lithics with a maximum size where there is a major break in the volcano s slope rather than at proximal locations this is also the location where ignimbrites are thickest and most massive the break in slope is interpreted to have reduced flow capacity and velocity increasing the sedimentation rate so that massive ignimbrite formed by hindered settling sedimentation ignimbrite cc exhibits no vertical grading of lithics though it does show downslope grading with maximum size at the major break in slope and a rapid decrease further downslope ignimbrite cc thins away from the break in slope and shows an upward fining of the grain size within the topmost few decimeters of the unit the ignimbrite is stratified proximally and grades to massive facies at the break in slope and distally to stratified facies with numerous inverse graded beds the simplest mechanism accounting for these downslope variations is progressive aggradation from a quasi steady nonuniform pyroclastic density current the changes in deposit thickness and facies are interpreted to record downcurrent changes in sedimentation rate the upward fining reflects waning flow inversely graded bedded depositional facies in distal areas is interpreted to reflect flow unsteadiness and a decrease in suspended sediment load ignimbrite cd shows vertical as well as downslope grading of lithics this characteristic coupled with the widespread massive facies of the deposit and the tabular unit geometry are features that can be reconciled with both the debris flow plug analogy for pyroclastic flows sparks 1976 and the progressive aggradation model branney and kokelaar 1992 however none of them appears to satisfy completely the field evidences implying that when dealing with massive ignimbrites other evidence than lithic grading needs to be presented to better understand the related transport and depositional processes

present day south american climate abstract this paper documents the main features of the climate and climate variability over south america on the basis of instrumental observations gathered during the 20th century it should provide a modern reference framework for paleoclimate research in south america targeting high resolution proxies over the past few centuries several datasets suitable for present day climate research are first described highlighting their advantages as well as their limitations we then provide a basic physical understanding of the mean annual cycle of the precipitation and atmospheric circulation over the continent and the adjacent oceans in particular the diversity of precipitation temperature and wind patterns is interpreted in terms of the long meridional extent of the continent and the disruption of the large scale circulation caused by the andes cordillera the contrasting oceanic boundary conditions and the landmass distribution similarly the intensity and timing of the interannual and interdecadal climatic fluctuations exhibit considerable geographical dependence as some regions are more influenced by large scale phenomena rooted in the tropical oceans while others are more influenced by high latitude phenomena the impact of these large scale phenomena over south america is documented by a regression analysis between selected atmospheric indices and the precipitation and temperature fields we have included a discussion on the seasonality and long term stability of such impacts and complemented our general description by an updated review of the literature on climate variability over specific regions

a distributed temperature index ice and snowmelt model including potential direct solar radiation hourly melt and discharge of storglaciaren a small glacier in sweden were computed for two melt seasons applying temperature index methods to a 30 m resolution grid for the melt component the classical degree day method yielded a good simulation of the seasonal patient of discharge but the pronounced melt induced daily discharge cycles were not captured modelled degree day factors calculated for every hour and each gridcell from melt obtained from a distributed energy balance model varied substantially both diurnally and spatially a new distributed temperature index model is suggested attempting to capture both the pronounced diurnal melt cycles and the spatial variations in melt due to the effects of surrounding topography this is accomplished by including a radiation index in terms of potential clear sky direct solar radiation and thus without the need for other data besides air temperature this approach improved considerably the simulation of diurnal discharge fluctuations and yielded a more realistic spatial distribution of melt rates the incorporation of measured global radiation to account for the reduction in direct solar radiation due to cloudiness did not lead to additional improvement in model performance

testing the hydrological coherence of high resolution gridded precipitation and temperature data sets testing the hydrological coherence of high resolution gridded precipitation and temperature data sets

ice loss from the southern patagonian ice field south america between 2000 and 2012 1 a time series composed of 156 aster derived digital elevation models dems and a radar penetration bias corrected version of the shuttle radar topography mission srtm dem is used to derive ice surface height and volume changes at the southern patagonian ice field spi in southern south america the observations made between february 2000 and march 2012 indicate that the ice field is rapidly losing volume at many of the largest outlet glaciers and in most cases thinning extends to the highest elevations of the ice field mass loss is occurring at a rate of 20 0 1 2 gt a 1 which when summed with mass loss at the adjacent northern patagonian ice field results in a combined rate of 24 4 1 4 gt a 1 equivalent to 0 067 0 004 mm a 1of sea level rise our decade long mass loss rates are substantially higher than those derived during the last three decades of the 20th century but are in good agreement with recent grace observations our volume loss estimate is sensitive to constraints applied to the amount of thickening in the accumulation zone new field measurements and a continued dem time series will be required to refine our estimates

past and future mass balance of ka roimata o hine hukatere franz josef glacier new zealand despite their relatively small total ice volume mid latitude valley glaciers are expected to make a significant contribution to global sea level rise over the next century due to the sensitivity of their mass balance systems to small changes in climate here we use a degree day model to reconstruct the past century of mass balance variation at ka roimata o hine hukatere franz josef glacier new zealand and to predict how mass balance may change over the next century analysis of the relationship between temperature precipitation and mass balance indicates that temperature is a stronger control than precipitation on the mass balance of franz josef glacier the glacier s mass balance relative to its 1986 geometry has decreased at a mean annual rate of 0 02 m a 1 w e between 1894 and 2005 we compare this reduction to observations of terminus advance and retreat of which franz josef glacier has the best record in the southern hemisphere for the years 2000 05 the relative mass balance ranged from 0 75 to 1 50 m a 1 w e with 2000 01 the only year showing a negative mass balance in a regionally downscaled intergovernmental panel on climate change mean warming scenario the annual relative mass balance will continue to decrease at 0 02 m a 1 w e through the next century

contribution of the patagonia icefields of south america to sea level rise digital elevation models of the northern and southern patagonia icefields of south america generated from the 2000 shuttle radar topography mission were compared with earlier cartography to estimate the volume change of the largest 63 glaciers during the period 1968 1975 2000 these glaciers lost ice at a rate equivalent to a sea level rise of 0 042 0 002 millimeters per year in the more recent years 1995 2000 average ice thinning rates have more than doubled to an equivalent sea level rise of 0 105 0 011 millimeters per year the glaciers are thinning more quickly than can be explained by warmer air temperatures and decreased precipitation and their contribution to sea level per unit area is larger than that of alaska glaciers

can the snowline be used as an indicator of the equilibrium line and mass balance for glaciers in the outer tropics because the glacier snowline is easy to identify on optical satellite images and because in certain conditions it can be used as an indicator of the equilibrium line it may be a relevant parameter for the study of the relationships between climate and glaciers although several studies have shown that the snowline altitude sla at the end of the hydrological year is a good indicator of the equilibrium line altitude ela for mid latitude glaciers such a relationship remains conjectural for tropical glaciers indeed unlike in mid latitudes tropical climate conditions result in a distinct seasonality of accumulation ablation processes we examine this relationship using direct field ela and mass balance measurements made on glaciar zongo bolivia 168 s and glaciar artesonraju peru 98 s and the sla retrieved from satellite images acquired in the past two decades we show that on glaciers in the outer tropics 1 ablation is reduced during the dry season in austral winter may august the sla does not change much and satellite images acquired between may and august could be used to compute the sla and 2 the highest sla detected on a number of satellite images acquired during the dry season provides a good estimate of the annual ela however as snowfall events can occur during the dry season the sla detected on satellite images tends to underestimate the ela thus we recommend validating the sla computed from satellite images with field data collected on a benchmark glacier before measuring the sla on other glaciers in the same mountain range for which no field data are available this study is a major step towards extending the measurement of glacier parameters ela and mass balance at the scale of a whole mountain range in the outer tropics to better document the relationships between climate and glaciers

glacier extent in sub antarctic kerguelen archipelago from mis 3 period evidence from 36cl dating documenting sub antarctic glacier variations during the local last glacial maximum is of major interest to better understand their sensitivity to atmospheric and oceanic temperature changes in conjunction with antarctic ice sheet changes however data are sparse because evidence of earlier glacier extents is for most sub antarctic islands located offshore making their observation complex here we present cosmogenic 36cl surface exposure ages obtained from five sites at kerguelen to document the glacial history the 36cl ages from roche moutonnee surfaces erratics and boulders collected on moraines span from 41 9 4 4 ka to 14 3 1 1 ka ice began to retreat on the eastern part of the main island before 41 4 4 4 ka slow deglaciation occurred from 41 to 29 ka there is no evidence of advances between 29 ka and the antarctic cold reversal acr period 14 5 12 9 ka period during the acr however the bontemps and possibly belvedere moraines were formed by the advance of a cook ice cap outlet glacier and a local glacier on the presque ile jeanne d arc respectively this glacier evolution differs partly from that of glaciers in new zealand and in patagonia these asynchronous glacier changes in the sub antarctic region are however in agreement with sea surface temperature changes recorded around antarctica which suggest differences in the climate evolution of the indo pacific and atlantic sectors of antarctica

degree day glacier mass balance modelling with applications to glaciers in iceland norway and greenland a degree day glacier mass balance model is applied to three glaciers in iceland norway and greenland for which detailed mass balance measurements are available over a period of several years model results are in good agreement with measured variations in the mass balance with elevation over the time periods considered for each glacier in addition the model explains 60 80 of the year to year variance in the elevation averaged summer season mass balance measurements on the glaciers using a single parameter set for each glacier the increase in ablation on the glaciers due to a warming of 2 c is predicted to range from about 1 m w e year 1 at the highest elevations to about 2 5 m w e year 1 at the lowest elevations predicted changes in the winter balance measured between fixed date are relatively small except at the lowest elevations on the icelandic and norwegian glaciers where the winter balance is significantly reduced equilibrium line altitudes are raised by 200 300 m on the icelandic and norwegian glaciers except at the highest elevations the winter balance of the icelandic and norwegian glaciers is predicted to decrease even if the warming is accompanied by a 10 increase in the precipitation no firm evidence of a climate related variation in the degree day factors or in the temperature lapse rate on the same glacier could be found the model furthermore reproduces large variations in the mass balance with elevation and from year to year on each glacier using the same parameter set we assume therefore that these parameters will not change significantly for the climate scenarios considered here

development of a three dimensional meso γ primitive equation model katabatic winds simulation in the area of terra nova bay antarctica the spatial evolution of antarctic katabatic winds in the area of terra nova bay is examined using the three dimensional version of the universite catholique de louvain modele atmospherique regional ucl mar mesoscale primitive equation models the ability of the model to replicate classical linear mountain wave simulations is verified then three dimensional experiments are performed for the terrain configuration of terra nova ross sea coastal zone using different horizontal resolutions 5 10 and 20 km the model converges for resolutions lower than 10 km results are in qualitative agreement with available observations and previous modeling work strong katabatic winds are simulated with a jet over terra nova bay the model seems able to initiate the mesocyclonic activity in the ross sea due to the katabatic circulation

assessment of multispectral glacier mapping methods and derivation of glacier area changes 1978 2002 in the central southern alps new zealand from aster satellite data field survey and existing inventory data we have measured the glacier area changes in the central southern alps new zealand between 1978 and 2002 and have compiled the 2002 glacier outlines using an image scene from the advanced spaceborne thermal emission and reflection radiometer aster three automated classification methods were tested 1 band ratio 2 normalized difference snow index and 3 supervised classification the results were compared with the glacier outlines photo interpreted from the aster data and were further validated using gps aided field mapping of selected test glaciers the aster 3 4 band ratio provided the best results however all the classification methods failed to extract extensive debris covered parts of the glaciers therefore the photo interpreted 2002 outlines were used when comparing with the existing 1978 glacier inventory derived from aerial photographs our results show a 17 reduction of glacier area mainly driven by the retreat of the large valley glaciers despite the large climatic gradient from west to east glaciers on both sides of the main divide lost similar percentages of area except franz josef and fox glaciers which advanced smaller glaciers were found to have changed very little in the study period

separation of tectonic and local components of horizontal gps station velocities a case study for glacial isostatic adjustment in east antarctica accurate measurement of the local component of geodetic motion at gps stations presents a challenge due to the need to separate this signal from the tectonic plate rotation a pressing example is the observation of glacial isostatic adjustment gia which constrains the earth s response to ice unloading and hence contributions of ice covered regions such as antarctica to global sea level rise following ice mass loss while both vertical and horizontal motions are of interest in general we focus on horizontal gps velocities which typically contain a large component of plate rotation and a smaller local component primarily relating to gia incomplete separation of these components introduces significant bias into estimates of gia motion vectors we present the results of a series of tests based on the motions of gps stations from east antarctica 1 signal separation for sets of synthetic data that replicate the geometric character of non separable and separable gia like horizontal velocities and 2 signal separation for real gps station data with an appraisal of uncertainties for both synthetic and real motions we compare results where the stations are unweighted and where each station is areal weighted using a metric representing the inverse of the spatial density of neighbouring stations from the synthetic tests we show that a gia like signal is recoverable from the plate rotation signal providing it has geometric variability across east antarctica we also show that areal weighting has a very significant effect on the ability to recover a gia like signal with geometric variability and hence on separating the plate rotation and local components for the real data assuming a rigid antarctic plate fitted plate rotation parameters compare well with other studies in the literature we find that 25 out of 36 gps stations examined in east antarctica have non zero local horizontal velocities at the 2 level after signal separation we make the code for weighted signal separation available to assist in the consistent appraisal of separated signals and the comparison of likely uncertainty bounds for future studies

climate sensitivity of a high precipitation glacier in new zealand the sensitivity of glaciers to climatic change is key information in assessing the response and sea level implications of projected future warming new zealand glaciers are important globally as an example of how maritime glaciers will contribute to sea level rise a spatially distributed energy balance model is applied to brewster glacier new zealand in order to calculate glacier mass balance run off and sensitivity to climate change the model successfully simulates four annual mass balance cycles close to half 52 of the energy available for melt on the glacier is supplied by turbulent heat fluxes with radiation less important except during the winter model sensitivity to temperature change is one of the largest reported on earth at 2 0 m w e a 1 8c 1 in contrast a 50 change in precipitation is required to offset the mass balance change resulting from a 18c temperature change meltwater run off sensitivity is also very high increasing 60 with a 18c warming the extreme sensitivity of mass balance to temperature change suggests that significant ice loss will occur with even moderate climate warming

ice wastage on the kerguelen islands 49 s 69 e between 1963 and 2006 1 we observed the wastage of ice masses on the kerguelen islands indian ocean 49 s 69 e using historical information and recent satellite data overall the total ice covered area on the islands declined from 703 to 552 km2 between 1963 and 2001 a reduction of 21 the area of cook ice cap the main ice body decreased asymmetrically from 501 to 403 km2 west flowing glaciers lost 11 of their area while east flowing glaciers lost 28 after 1991 the retreat rate accelerated from 1 9 km2 a 1963 1991 to 3 8 km2 a 1991 2003 between 1963 and 2000 the ice volume loss was 25 30 km3 equivalent to an area average ice thinning rate of 1 4 1 7 m a the glacial retreat took place in the climatic context of a relatively low level of precipitation compared to the 1950s and a 1 c warming that occurred between 1964 and 1982 the acceleration of the ice losses since at least the 1990s indicates that the state of the ice bodies on the kerguelen islands is still far from balanced together with other studies in patagonia south georgia and heard island our analysis is consistent with a pattern of strong and accelerated wastage of ice masses influenced by the southern ocean

ice loss rates at the northern patagonian icefield derived using a decade of satellite remote sensing abstract we use a satellite based survey of glacier surface elevation changes speeds and surface melt conditions between 2000 and 2011 to quantify mass loss from the northern patagonian icefield npi chile a history of ice elevation change is found by differencing aster digital elevation models dems relative to a void filled version of the dem collected by the shuttle radar topography mission srtm in february 2000 thinning rates have accelerated at lower elevations while above the equilibrium line altitude ela recent thinning rates are not significantly different from those observed in previous studies a volumetric change of 4 06 0 11 km 3 yr is found by summing surface elevation changes over all glaciers in the npi this is regarded as a lower bound because volume loss due to frontal retreat and sub aqueous melting is not included this volume change is converted to a mass loss of 3 40 0 07 gt yr taking into account density differences above and below the equilibrium line we find that the npi is providing at least 0 009 0 0002 mm yr to ongoing sea level change in agreement with previous estimates sub pixel offset tracking of aster image pairs is used to produce glacier displacements over intervals typically ranging from 6 days to 18 months the first whole icefield composite velocity map is presented the terminus of the san rafael glacier on the western side of the npi sustained a peak calving front speed of 19 7 1 2 m day for 7 days in the austral fall of 2007 passive microwave observations indicate that the surface of the accumulation basin of the glacier was wet during this period of rapid motion suggesting that the fast speed may be a consequence of a rise in sub glacial water pressure sourced from melt or rainwater making its way to the glacier bed and reducing basal friction several other outlet glaciers including the benito and hpn1 glaciers on the isolated western side of the icefield accelerated while thinning between 2007 and 2011 marked acceleration also occurred after 2007 at the front of the san quintin glacier the largest outlet glacier of the npi the paucity of thickness measurements at the outlet glaciers means it is impossible to accurately gauge the mass flux of the icefield and thus give a full estimate of the mass balance

late holocene glacier reconstruction reveals retreat behind present limits and two stage little ice age on subantarctic south georgia observational data show that climate in the southern ocean region is rapidly changing however past the instrumental period our understanding of climate variability in the region is limited by a scarcity of highresolution palaeoclimate records alpine glaciers present on many southern ocean islands may provide such data because changes in their mass balance extent and erosion rates often mark a response to climate shifts rock flour the fine grained fraction of the glacial erosion process is suspended in meltwater streams and transferred into the sediments of downstream lakes continuously recording glacier variations here we utilize this relationship to present a reconstruction of the late holocene glacier history of subantarctic south georgia using sediments from the glacier fed middle hamberg lake to fingerprint a glacial erosion size signal we used titanium counts validated against changes in sediment density and grain size allowing a continuous reconstruction of glacier variations over the past similar to 1250 years together with local moraine evidence and supporting evidence from other southern hemisphere glaciers on new zealand and in patagonia our findings reveal a series of consecutively diminishing late holocene advances in addition to a glacier maximum before 1250 cal a bp these include a twostage litle ice age with advances around 300 and 120 cal a bp in line with evidence from southern patagonia in addition we present evidence for an unreported retreat behind present limits around 500 cal bp

regional modeling of surface mass balance on the cook ice cap kerguelen islands 49 circ mathrm s 49 s 69 circ mathrm e 69 e we assess the ability of the regional circulation model mar to represent the recent negative surface mass balance smb observed over the kerguelen islands 49 circ hbox s 69 circ hbox e and evaluate the uncertainties in smb projections until the end of the century the mar model forced by era interim reanalysis shows a good agreement with meteorological observations at kerguelen particularly after slight adjustment of the forcing fields 10 humidity 0 8 circ hbox c all year round to improve precipitation occurrence and intensity the modeled smb and surface energy balance seb are also successfully evaluated with observations and spatial distributions are explained as being largely driven by the elevation gradient and by the strong west to east foehn effect occurring on the ice cap we select five general circulation models gcms from the coupled model intercomparison project phase 5 cmip5 by evaluating their ability to represent temperature and humidity in the southern mid latitudes over 1980 1999 with respect to era interim and use them to force the mar model these simulations fail to replicate smb observations even when outputs from the best cmip5 model access1 3 are used as forcing because all gcms fail in accurately reproducing the circulation changes observed at kerguelen since the mid 1970s global models chosen to represent extreme values of smb drivers also fail in producing extreme values of smb suggesting that more rigorous modeling of present and future circulation changes with gcms is still needed to accurately assess future changes of the cryosphere in this area