historical glacier fluctuations of jostedalsbreen and folgefonna southern norway reassessed by new pictorial and written evidence glaciers are sensitive indicators of past climate and thus valuable sources of climate history unfortunately direct determinations of glacier changes variations in length and mass balance did not start with increasing accuracy before the end of the nineteenth century therefore historical and geomorphological evidence has to be used to reconstruct glacier variability for preceding time periods here we present new glacier length reconstructions for selected outlet glaciers of jostedalsbreen and folgefonna two ice caps in southern norway a wealth of different historical sources drawings paintings prints photographs maps written accounts about 400 documents allows reconstruction of glacier length variations for the last 300 jostedalsbreen and 200 years folgefonna respectively we present historical material newly collected for briksdalsbreen boyabreen store supphellebreen bergsetbreen nigardsbreen lodalsbreen all jostedalsbreen and bondhusbrea buerbreen both southern folgefon

the effect of geomorphological setting on holocene lake sediment variability northern swedish lapland the effect of geomorphological setting on holocene lake sediment variability northern swedish lapland

latest pleistocene and holocene glacier fluctuations in the himalaya and tibet abstract the timing and extent of latest pleistocene and holocene alpine glacier fluctuations in the himalaya and tibet are poorly defined due to the logistical and political inaccessibility of the region and the general lack of modern studies of the glacial successions nevertheless renewed interest in the region and the aid of newly developing numerical dating techniques have provided new insights into the nature of latest pleistocene and holocene glacier oscillations these studies provide abundant evidence for significant glacial advances throughout the last glacial cycle in most high himalayan and tibetan regions glaciers reached their maximum extent early in the last glacial cycle however true last glacial maximum glacier advances were significantly less extensive notable glacier advances occurred during the lateglacial and the early holocene with minor advances in some regions during the mid holocene there is abundant evidence for multiple glacial advances throughout the latter part of the holocene although these are generally very poorly defined and were less extensive than the early holocene glacier advances the poor chronological control on latest pleistocene and holocene glacial successions makes it difficult to construct correlations across the region and with other glaciated regions in the world which in turn makes it hard to assess the relative importance of the different climatic mechanisms that force glaciation in this region the lateglacial and holocene glacial record however is particularly well preserved in several regions notably in muztag ata and kongur and the khumbu himal these successions have the potential to be examined in detail using newly developing numerical dating methods to derive a high resolution record of glaciation to help in paleoclimatic reconstruction and understanding the dynamics of climate and glaciation in the himalaya and tibet

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

holocene glacier fluctuations a global overview of glacier advances and retreats grouped by regions and by millennia for the holocene is compiled from previous studies the reconstructions of glacier fluctuations are based on 1 mapping and dating moraines defined by 14 c tcn osl lichenometry and tree rings discontinuous records time series and 2 sediments from proglacial lakes and speleothems continuous records time series using 189 continuous and discontinuous time series the long term trends and centennial fluctuations of glaciers were compared to trends in the recession of northern and mountain tree lines and with orbital solar and volcanic studies to examine the likely forcing factors that drove the changes recorded a general trend of increasing glacier size from the earlyemid holocene to the late holocene in the extra tropical areas of the northern hemisphere nh is related to overall summer temperature forced by orbitally controlled insolation the glaciers in new zealand and in the tropical andes also appear to follow the orbital trend i e they were decreasing from the early holocene to the present in contrast glacier fluctuations in some monsoonal areas of asia and southern south america generally did not follow the orbital trends but fluctuated at a higher frequency possibly triggered by distinct teleconnections patterns during the neoglacial advances clustered at 4 4e4 2 ka 3 8e3 4 ka 3 3e2 8 ka 2 6 ka 2 3e2 1 ka 1 5e1 4 ka 1 2e1 0 ka 0 7e0 5 ka corresponding to general cooling periods in the north atlantic some of these episodes coincide with multidecadal periods of low solar activity but it is unclear what mechanism might link small changes in irradiance to widespread glacier fluctuations explosive volcanism may have played a role in some periods of glacier advances such as around 1 7e1 6 ka coinciding with the taupo volcanic eruption at 232 5 ce but the record of explosive volcanism is poorly known through the holocene the compilation of ages suggests that there is no single mechanism driving glacier fluctuations on a global scale multidecadal variations of solar and volcanic activity supported by positive feedbacks in the climate system may have played a critical role in holocene glaciation but further research on such linkages is needed the rate and the global character of glacier retreat in the 20th through early 21st centuries appears unusual in the context of holocene glaciation though the retreating glaciers in most parts of the northern hemisphere are still larger today than they were in the early and or mid holocene the current retreat

exact dating of the meghalayan lower boundary based on high latitude tree ring isotope chronology abstract subdivision of the holocene series epoch into the greenlandian northgrippian and meghalayan stages ages has recently been ratified based on stable isotope records from ice core and speleothem archives the base of the most recent chronostratigraphic unit corresponding to the northgrippian meghalayan boundary coincides with the 4 2 ka event recognised as a low latitude drought anomaly the global stratotype section and point gssp for the boundary the oxygen isotope record from the mawmluh cave speleothem india demonstrates this event with markedly weakened asian summer monsoon here we contribute to the assessments of the geological time scale and the global characteristics of this event by detailing an isotopic excursion in tree ring carbon isotopes from high latitude subarctic europe the 13c chronology demonstrates extremely overcast wet conditions especially between 2190 and 2100 bce with anomalous conditions sustaining until 1990 bce in addition to demonstrating its exact dating and duration the 13c data also illustrate the two stage nature of the event and highlight the greater magnitude of the earlier stage this reinforces the characterisation of this meghalayan anomaly in the context of other proxy sites around the world the north atlantic forcing previously associated with weakened asian summer monsoon accords with the suggested roles of north atlantic oscillation and or southwards shift of inter tropical convergence zone in producing the hydroclimatic anomaly in fact it would be clarifying to separate the hydroclimatic meghalayan anomaly from the broadly cited and potentially longer lasting 4 2 ka event to analyse their respective forcing mechanisms we conclude by dating the meghalayan lower boundary to 2190 bce

lake sediment studies of holocene glacial activity in the karsa valley northern sweden contrasts in interpretation a multidisciplinary study of lake sediments deposited in lake basins in the karsa valley northern sweden suggests the complete disappearance of the karsa glacier during the early and mid holocene glacier reformation indicated by the deposition of sediment with a fine particle size distribution and low organic content in the three lakes took place at c 3000 14 c years bp this interpretation contrasts with a study based on the weight loss on ignition of the same sediments which suggests several glacier advances throughout the entire holocene the contrasting interpretation is due to different methodological approaches single core site studies should be avoided in the future and only features that are consistently reproducible and can be dated in spatially distributed cores should be interpreted in terms of variations in glacial activity environmental conditions and ultimately climate

glacier fluctuations equilibrium line altitudes and palaeoclimate in lyngen northern norway during the lateglacial and holocene based on lacustrine and morpho stratigraphical evidence from lyngen in troms northern norway 13 marginal moraines have been mapped in front of lenangsbreene in strupskardet moraines m1 m13 are inferred to represent glacier halts or advance readvance taking place during the lateglacial and holocene the presence of collapse depressions suggests that some of them were ice cored m1 m3 a chronological framework taking into account a combination of former shorelines and related glacier meltwater channels lichenometry and ams radiocarbon dated lacustrine sediments spanning the last 20 000 cal yr bp has been established the distal glacier fed lake aspvatnet was isolated from the sea c 10 300 cal yr bp and the lacustrine sediments have been investigated by use of loss on ignition loi magnetic susceptibility water content wet and dry bulk density dbd and the magnetic parameters anhysteretic remanent magnetization arm and saturation remanent magnetization sirm there is in general good agr

high frequency holocene glacier fluctuations in new zealand differ from the northern signature understanding the timings of interhemispheric climate changes during the holocene along with their causes remains a major problem of climate science here we present a high resolution 10be chronology of glacier fluctuations in new zealand s southern alps over the past 7000 years including at least five events during the last millennium the extents of glacier advances decreased from the middle to the late holocene in contrast with the northern hemisphere pattern several glacier advances occurred in new zealand during classic northern warm periods these findings point to the importance of regional driving and or amplifying mechanisms we suggest that atmospheric circulation changes in the southwest pacific were one important factor in forcing high frequency holocene glacier fluctuations in new zealand

latest pleistocene and holocene glaciation of baffin island arctic canada key patterns and chronologies abstract melting glaciers and ice caps on baffin island contribute roughly half of the sea level rise from all ice in arctic canada although they comprise only one fourth of the total ice in the region the uncertain future response of arctic glaciers and ice caps to climate change motivates the use of paleodata to evaluate the sensitivity of glaciers to past warm intervals and to constrain mechanisms that drive glacier change we review the key patterns and chronologies of latest pleistocene and holocene glaciation on baffin island the deglaciation by the laurentide ice sheet occurred generally slowly and steadily throughout the holocene to its present margin barnes ice cap except for two periods of rapid retreat an early interval 12 to 10 ka when outlet glaciers retreated rapidly through deep fiords and sounds and a later interval 7 ka when ice over foxe basin collapsed in coastal settings alpine glaciers were smaller during the younger dryas period than during the little ice age at least some alpine glaciers apparently survived the early holocene thermal maximum which was several degrees warmer than today although data on glacier extent during the early holocene is extremely sparse following the early holocene thermal maximum glaciers advanced during neoglaciation beginning in some places as early as 6 ka although most sites do not record near little ice age positions until 3 5 to 2 5 ka alpine glaciers reached their largest holocene extents during the little ice age when temperatures were 1 1 5 c cooler than during the late 20th century synchronous advances across baffin island throughout neoglaciation indicate sub milankovitch controls on glaciation that could involve major volcanic eruptions and solar variability future work should further elucidate the state of glaciers and ice caps during the early holocene thermal maximum and glacier response to climate forcing mechanisms

multi proxy record of holocene glacial history of the spearhead and fitzsimmons ranges southern coast mountains british columbia abstract evidence from glacier forefields and lakes is used to reconstruct holocene glacier fluctuations in the spearhead and fitzsimmons ranges in southwest british columbia radiocarbon ages on detrital wood and trees killed by advancing ice and changes in sediment delivery to downstream proglacial lakes indicate that glaciers expanded from minimum extents in the early holocene to their maximum extents about two to three centuries ago during the little ice age the data indicate that glaciers advanced 8630 8020 6950 6750 3580 2990 and probably 4530 4090 cal yr bp and repeatedly during the past millennium little ice age moraines dated using dendrochronology and lichenometry date to early in the 18th century and in the 1830s and 1890s limitations inherent in lacustrine and terrestrial based methods of documenting holocene glacier fluctuations are minimized by using the two records together

10 be exposure dating of the timing of neoglacial glacier advances in the ecrins pelvoux massif southern french alps alpine glacier variations are known to be reliable proxies of holocene climate here we present a terrestrial cosmogenic nuclide tcn based glacier chronology relying on 24 new be 10 exposure ages which constrain maximum neoglacial positions of four small to mid sized glaciers rateau lautaret bonnepierre and etages in the ecrins pelvoux massif southern french alps glacier advances marked by mainly lateral moraine ridges that are located slightly outboard of the little ice age lia c 1250 1860 ad maximum positions were dated to 4 25 0 44 ka 3 66 0 09 ka 2 09 0 10 ka c 1 31 0 17 ka and to 0 92 0 02 ka the 4 2 ka advance albeit constrained by rather scattered dates is to our knowledge exposure dated here for the first time in the alps it is considered as one of the first major neoglacial advance in the western alps in agreement with other regional paleoclimatological proxies we further review alpine and northern hemisphere mid to high latitude evidence for climate change and glacier activity concomitant with the 4 2 ka event the 2 1 ka advance was not extensively dated in the alps and is thought to represent a prominent advance in early roman times other neoglacial advances dated here match the timing of previously described alpine neoglacial events our results also suggest that a neoglacial maximum occurred at etages glacier 0 9 ka ago i e during the medieval climate anomaly mca c 850 1250 ad at rateau glacier discordant results are thought to reflect exhumation and snow cover of the shortest moraine boulders overall this study highlights the need to combine several sites to develop robust neoglacial glacier chronologies in order to take into account the variability in moraine deposition pattern and landform obliteration and conservation

rapid oceanic and atmospheric changes during the younger dryas cold period the younger dryas event which began approximately 12 900 years ago was a period of rapid cooling in the northern hemisphere driven by large scale reorganizations of patterns of atmospheric and oceanic circulation 1 3 environmental changes during this period have been documented by both proxy based reconstructions 3 and model simulations 4 but there is currently no consensus on the exact mechanisms of onset stabilization or termination of the younger dryas 5 8 here we present high resolution records from two sediment cores obtained from lake krakenes in western norway and the nordic seas multiple proxies from lake krakenes are indicative of rapid alternations between glacial growth and melting during the later younger dryas meanwhile reconstructed sea surface temperature and salinity from the nordic seas show an alternation between sea ice cover and the influx of warm salty north atlantic waters we suggest that the influx of warm water enabled the westerly wind systems to drift northward closer to their present day positions the winds thus brought relatively warm maritime air to northern europe resulting in rising temperatures and the melting of glaciers subsequent input of this fresh meltwater into the ocean spurred the formation of sea ice which forced the westerly winds back to the south cooling northern europe we conclude that rapid alternations between these two states immediately preceded the termination of the younger dryas and the permanent transition to an interglacial state the impact of freshwater pulses released from northern hemisphere ice sheets on the north atlantic meridional overturning circulation has been suggested as a likely mechanism for the younger dryas cooling 7 11 in addition a responsive sea ice cover has been proposed as a mechanism that could rapidly alter the heat exchange between the ocean and atmosphere during the last glacial period 12 13 the roles of the ocean and the atmosphere in triggering the climate shifts around the younger dryas are much discussed 9 these hypotheses are difficult to resolve partly because the temporal resolution of most palaeoclimate archives is too coarse to enable the anatomy of the younger dryas stadial to be adequately described 14 to address these questions we here present a lake sediment record at sub annual resolution together with new data on the sea surface conditions of the norwegian atlantic current nwac throughouttheyoungerdryasstadial fig 1

western canadian glaciers advance in concert with climate change circa 4 2 ka 1 disparate climate proxies from the northern hemisphere record a climate event at 4 2 3 8 ka here we show that glaciers throughout the mountain ranges of western canada advanced at about this time this conclusion is based on 1 new and previously reported radiocarbon ages on in situ stumps logs branches and soils exposed by recent retreat in glacier forefields and 2 clastic rich sediment intervals in cores retrieved from four montane lakes these glacier and lacustrine data indicate a period of several decades to century length when climate conditions cool summers wet winters or both favoured glacier nourishment and advance across western canada

defining modern day area altitude balance ratios aabrs and their use in glacier climate reconstructions abstract with the increasing use of digital elevation models in palaeo glacier reconstructions and the availability of freeware spreadsheets the area altitude balance ratio aabr and balance ratio br methods are becoming increasingly used in palaeo glacier reconstruction for estimating equilibrium line altitudes ela and subsequently deriving quantitative estimates of palaeo climate while there are many data detailing contemporary accumulation area ratios there are still only a few studies that have established from contemporary environments aabr br ratios publicly available glacier mass balance world glacier monitoring service us geological survey and norwegian water directorate and spatial extent datasets provided the basis for this research from a time series of mass balance regressing specific net balance against ela allows the zero net balance ela to be identified once the zero balance ela is established the glacier hypsometry above and below the ela is defined the aabr br is calculated by using the right hand side the following aabr b n a b b n a c z a c a a c z a b a a b where b nab and b nac are the net mass balance gradients in the ablation and accumulation zones respectively z a c and z a b are the area weighted mean altitudes of the accumulation and ablation areas respectively and a ac and a ab are the areas of the accumulation and ablation areas respectively aabrs are calculated for a suite of glaciers located across a range of climatic zones and glacier types with antarctica being excluded the following representative aabrs are found a global aabr 1 75 0 71 mid latitude maritime 1 9 0 81 high latitude 2 24 0 85 north america west coast 2 09 0 93 north america eastern rockies 1 11 0 1 canadian arctic 2 91 0 35 svalbard 2 13 0 52 western norway 1 5 0 4 european alps 1 59 0 6 central asia 1 75 0 56 kamchatka 3 18 0 16 this study provides an empirically derived dataset characterising aabr ratios which may be used for ela estimation in palaeo glacier reconstructions and for palaeo climate quantification

diatom oxygen isotopes in pro glacial lake sediments from northern sweden a 5000 year record of atmospheric circulation we use a pro glacial oxygen isotope record of diatom silica 18odiatom and a sedimentary proxy for glacier flutuations to determine centennial millennial scale climate change during the last 5000

two millennia of glacier advances from southern iceland dated by tephrochronology two glaciers at eyjafjallajokull south iceland provide a record of multiple episodes of glacier advance since the sub atlantic period ca 2000 yr ago a combination of tephrochronology and lichenometry was applied to date ice marginal moraines tills and meltwater deposits two glacier advances occurred before the 3rd century ad others in the 9th and 12th centuries bracketing the medieval warm period and five groups of advances occurred between ad 1700 and 1930 within the little ice age the advances of eyjafjallajokull before the norse settlement ca ad 870 were synchronous with other glacier advances identified in iceland in contrast medieval glacier advances between the 9th and 13th centuries are firmly identified for the first time in iceland this challenges the view of a prolonged medieval warm period and supports fragmentary historical data that indicate significant medieval episodes of cooler and wetter conditions in iceland an extended and more detailed glacier chronology of the mid and late little ice age is established which demonstrates that some small outlet glaciers achieved their little ice age maxima around ad 1700 while little ice age advances across iceland appear to synchronous the timing of the maximum differs between glacier type and region

latest pleistocene and holocene alpine glacier fluctuations in scandinavia abstract during the early holocene abrupt decadal to centennial scale climate variations caused significant glacier variations in norway increased freshwater inflow to the north atlantic and arctic oceans has been suggested as one of the most likely mechanisms to explain the abrupt and significant lateglacial and early holocene climatic events in nw europe the largest early holocene glacier readvances occurred 11 200 10 500 10 100 9700 9200 and 8400 8000 cal yr bp the studied norwegian glaciers apparently melted away at least once during the early mid holocene the period with the most contracted glaciers in scandinavia was between 6600 and 6000 cal yr bp subsequent to 6000 cal yr bp the glaciers started to advance and the most extensive glaciers existed at about 5600 4400 3300 2300 1600 cal yr bp and during the little ice age times with overall less glacier activity were apparently around 5000 4000 3000 2000 and 1200 cal yr bp it has been proposed that several glacier advances occurred in scandinavia including northern sweden at 8500 7900 7400 7200 6300 6100 5900 5800 5600 5300 5100 4800 4600 4200 3400 3200 3000 2800 2700 2000 1900 1600 1200 1000 and 700 200 cal yr bp glaciers in northern sweden probably reached their greatest little ice age extent between the 17th and the beginning of the 18th centuries evidence for early holocene glacier advances in northern scandinavia however has been questioned by more recent multi disciplinary studies the early to mid holocene glacier episodes in northern sweden may therefore be questioned most norwegian glaciers attained their maximum little ice age extent during the mid 18th century cumulative glacier length variations in southern norway based on marginal moraines dated by lichenometry and historic evidence show an overall retreat from the mid 18th century until the 1930s 40s subsequently most norwegian glaciers retreated significantly maritime outlet glaciers with short frontal time lags 15 20 years continued their retreat to the 1970s and 1980s however maritime glaciers started to advance as a response to higher winter accumulation during the first part of the 1990s after 2000 several of the observed glaciers have retreated remarkably fast annual frontal retreat 100 m mainly due to high summer temperatures the general glacier retreat during the early holocene and the neoglacial advances after 6000 cal yr bp are in line with orbital forcing due to the decrease of northern hemisphere summer solar insolation and the increase in winter insolation in addition regional weather modes such as the north atlantic oscillation nao and the arctic oscillation ao play a significant role with respect to decadal and multi decadal climate variability

a new interpretation of the date of the little ice age glacier maximum at svartisen and okstindan northern norway new results concerning the dating of little ice age glacier variations at svartisen and okstindan northern norway are presented measurements of lichens of the rhizocarpon subgenus on gravestones are used to construct several local sets of lichenometric dating curves these are partly adjusted in relation to well established lichenometric dating curves from southern norway the little ice age maximum at svartisen and okstindan is thereby dated to the mid eighteenth century i e in agreement with southern norway pre viously suggested earlier little ice age advances are demonstrated to have resulted from an underestimation of the growth rates of the rhizocarpon subgenus synchroneity of little ice age maxima in southern norway and at svartisen and okstindan suggest that a north south migration of latitudinal depressional tracks can be excluded as the main forcing factor as an alternative an increased se nw trend of moist air ow in winter parallel to the coast of norway is suggested as the

the loch lomond readvance on the isle of mull scotland glacier reconstruction and palaeoclimatic implications geomorphological mapping of mull provides evidence for an icefield 143 km2 in area flanked by six corrie glaciers with a total area of ca 13 km2 the absence of lateglacial periglacial features shorelines and pollen sites from the area occupied by this readvance together with radiocarbon dating of shell fragments confirm that it occurred during the loch lomond younger dryas stade the thickness of glacigenic deposits within the area of the readvance is attributed to reworking of paraglacial sediments up valley continuity of recessional moraines indicates that the ice remained active and near to equilibrium during retreat consistent with slow warming following the coldest part of the stade reconstructed equilibrium line altitudes elas imply vigorous snow blowing by westerly winds and are consistent with a general southwestwards decline in elas across the scottish highlands an ela of 250 m was calculated for the mull icefield using an ablation accumulation balance ratio abr approach palaeotemperature and palaeoprecipitation estimates were derived by calculating a theoretical regional ela from meteorological data and assuming that the combination of temperature and precipitation implied by the theoretical ela approximates conditions at 250 m on mull during the loch lomond stade the result indicates a mean july sea level temperature of 5 7 0 5 c and a mean annual precipitation at 250 m of ca 2700 3800 mm best estimate 3200 mm indicating higher precipitation totals than at present owing to more vigorous atmospheric circulation copyright 2002 john wiley sons ltd

glacier and lake level variations in west central europe over the last 3500 years on the basis of glacier and lake level records this paper attempts for the first time a comparison between high resolution palaeohydrological and palaeoglaciological data in west central europe over the past 3500 years a data set of tree ring width radiocarbon and archaeological data in addition to historical sources were used to reconstruct fluctuations of the great aletsch the gorner and the lower grindelwald glaciers in the swiss alps the three ice streams experienced nearly synchronous advances at c 1000 600 bc and ad 500 600 800 900 1100 1200 and 1300 1860 these glacier fluctuations show strong correspondence with lake level variations reconstructed in eastern france jura mountains and pre alps and on the swiss plateau this supports the hypothesis of climatically driven fluctuations historical data available for the period since ad 1550 reveal in detail various meteorological conditions behind the successive glacier advances however in agreement with the general trend shown by th

local glaciers record delayed peak holocene warmth in south greenland abstract local glaciers and ice caps gics respond sensitively and quickly on the scale of decades to centuries to climate variations continuous records of past fluctuations in gic size provide information on the timing and magnitude of holocene climate shifts and a longer term perspective on 21st century glacier retreat although there is broad scale agreement on millennial scale trends in holocene climate variability and fluctuations in local gics in greenland regional variations are only loosely constrained here we present three holocene proglacial lake sediment records from south greenland an area with abundant local glaciers but few holocene length paleoclimate records in addition we use geospatial analysis to model past equilibrium line altitudes elas and thereby constrain the magnitude of ablation season temperature change during the warmest and coolest periods of the holocene physical and geochemical sedimentary characteristics show that two of the proglacial lakes continued to receive glacial meltwater input until 7 3 and 7 1 ka bp the survival of local glaciers implies that south greenland remained relatively cool and that summer temperatures gradually warmed but did not warm well beyond 1 2 c above present in the early holocene in the mid holocene from 7 1 to 5 5 ka bp organic sedimentation at these two sites indicates that local glaciers became very small or more likely melted away completely the glaciers within the third lake s catchment melted away prior to 5 2 ka bp as sediments deposited earlier in the holocene could not be dated at this site we estimate that summer temperatures increased by at least 1 2 1 8 c above present by 7 3 7 1 ka bp our results are consistent with other observations that suggest a north to south gradient in the timing of holocene thermal maximum conditions with southern greenland experiencing a delayed warming relative to other regions in greenland as summer temperatures cooled in the neoglacial our records show that sustained glacier regrowth began 3 1 ka bp with glaciers in the southernmost catchment which at present receive the most precipitation in the other two catchments which host smaller glaciers in a drier environment regrowth began at 1 3 and 1 2 ka bp the timing of which is in agreement with other glacial records from the arctic atlantic region local glaciers reached their maximum late holocene extents during a cooler second phase of the little ice age lia 0 2 0 1 ka bp that we estimate was at least 0 4 0 9 c cooler than present overall these findings improve understanding of the spatio temporal dynamics of holocene glacier and climate change in greenland potentially yielding valuable information about their future response

a complete record of holocene glacier variability at austre okstindbreen northern norway an integrated approach arctic glaciers are currently undergoing major changes but accurate knowledge about how they varied during the entire holocene is still scarce here we present a new complete glacier record from austre okstindbreen in nordland northern norway this reconstruction is based on a number of short and long cores retrieved from several downstream basins which have been analyzed by a suite of methods including geochemical elements xrf rock magnetic properties dry bulk density dbd and loss on ignition loi lake sediment distribution was surveyed and mapped prior to coring by the use of ground penetrating radar gpr independently lichen dated marginal moraines and historical information about the glacier frontal positions from old photographs and maps have made it possible to link the moraine sequence to the 210pb dated lake sediment chronology this integrated approach reveals that austre okstindbreen is the first known glacier in scandinavia to possibly have survived the holocene thermal optimum it also brackets the four largest glacier advances to c 7400 7000 1400 1200 900 700 and 300 150 years before ad 2000 b2k in contrast to most reconstructed glaciers in scandinavia the largest glacier advance was not associated with the little ice age but rather to an earlier period centred at 1300 b2k both the moraine chronology and the lacustrine records document this neoglacial advance compared to other glacier reconstructions from the northern hemisphere we identify near synchronous glacier advances occurring roughly at 4000 b2k 2700 b2k 1300 b2k and during the little ice age these correlative advances across the northern hemisphere suggest that these observed centennial scale events are a shared feature regardless of the large geographical distances separating them some minor discrepancies between different geographical areas may be caused by lack of precise dating but local climatic conditions may play a role as well

the avaatech xrf core scanner technical description and applications to ne atlantic sediments abstract x ray fluorescence xrf core scanning provides rapid high resolution down to 1 mm records of chemical composition on split sediment cores the measurements are non destructive and require very limited sample preparation the new avaatech xrf core scanner operational since 2002 covers the atomic mass range from al to u instrument parameters especially tube voltage can be adjusted to provide optimum settings for selected elements or sets thereof owing to the nature of the surface of split sediment cores particularly effects resulting from sample inhomogeneity and surface roughness results are semiquantitative yet provide reliable records of the relative variability in elemental composition downcore selected case studies from diverse sedimentary settings in the ne atlantic ocean illustrate a range of applications of xrf logging data these include preliminary stratigraphic interpretations glacial interglacial cycles provenance studies of the terrigenous sediment fraction lithological characterization early diagenetic processes and distinction between carbonate phases aragonite v calcite

sporteggbreen western norway in the past present and future simulations with a two dimensional dynamical glacier model a two dimensional shallow ice flow model yielding the glacier geometry at selected time intervals is used to simulate the development of sporteggbreen 1 from 8000 cal yr bp to the present 2 from ad 2011 to 2050 and 3 extending forward in time to ad 2100 and 2200 glacier surface geometry subglacial topography mass balance data internal deformation and subglacial sliding are used as input data for the model runs to force the model from 8000 cal yr bp to the present a mass balance series based on the equilibrium line altitude ela variations on jostedalsbreen to the west of sporteggbreen is applied a 50 reduction of the ela amplitude at jostedalsbreen is used to construct a new mass balance series and it was found that this gives a reasonably good coherence between the modelled and the real glacier the modelled time series for ela and length changes indicate that the glacier melted away c 7300 cal yr bp and was absent for c 1700 years it reformed c 5400 cal yr bp because of a mo

modern glacier characteristics as a basis for inferring former climates with particular reference to the loch lomond stadial abstract studies of the mass balance of modern glaciers have indicated that the equilibrium line altitude ela is the most critical parameter in the link between glaciers and climate average accumulation on a glacier includes components derived from direct precipitation on the glacier surface as well as wind drifting and avalanching of snow and approximates closely to accumulation at the equilibrium line ablation is most usefully predicted by mean summer temperature and there is a close non linear relationship between accumulation and mean summer temperature at the equilibrium line following discussion of methods of reconstructing former glaciers and calculating their equilibrium line altitudes the application of the above relationships to the loch lomond readvance glaciers of highland britain is considered and an outline of the precipitation pattern and the mean summer temperature of the loch lomond stadial is given

latest pleistocene and holocene glacier fluctuations in western canada we summarize evidence of the latest pleistocene and holocene glacier fluctuations in the canadian cordillera our review focuses primarily on studies completed after 1988 when the first comprehensive review of such evidence was published the cordilleran ice sheet reached its maximum extent about 16 ka and then rapidly decayed some lobes of the ice sheet valley glaciers and cirque glaciers advanced one or more times between 15 and 11 ka by 11 ka or soon thereafter glacier cover in the cordillera was no more extensive than at the end of the 20th century glaciers were least extensive between 11 and 7 ka a general expansion of glaciers began as early as 8 4 ka when glaciers overrode forests in the southern coast mountains it culminated with the climactic advances of the little ice age holocene glacier expansion was not continuous but rather was punctuated by advances and retreats on a variety of timescales radiocarbon ages of wood collected from glacier forefields reveal six major periods of glacier advance 8 59 8 18 7 36 6 45 4 40 3 97 3 54 2 77 1 71 1 30 ka and the past millennium tree ring and lichenometric dating shows that glaciers began their little ice age advances as early as the 11th century and reached their maximum holocene positions during the early 18th or mid 19th century our data confirm a previously suggested pattern of episodic but successively greater holocene glacier expansion from the early holocene to the climactic advances of the little ice age presumably driven by decreasing summer insolation throughout the holocene proxy climate records indicate that glaciers advanced during the little ice age in response to cold conditions that coincided with times of sunspot minima priority research required to further advance our understanding of late pleistocene and holocene glaciation in western canada includes constraining the age of late pleistocene moraines in northern british columbia and yukon territory expanding the use of cosmogenic surface exposure dating techniques using multi proxy paleoclimate approaches and directing more of the research effort to the northern canadian cordillera

a new approach to calculating holocene winter precipitation by combining glacier equilibrium line altitudes and pine tree limits a case stud from hardangerjokulen central southern norway at hardangerjokulen central southern norway detailed knowledge of the number age and magnitude of holocene glacier fluctuations is used to reconstruct variations in equilibrium line altitude ela for the last 10 000 years present and past elas are based on an accumulation area ratio aar of 0 7 and are adjusted for land uplift a synchronous relationship between advanced glacier positions and the highest pine tree limits pinus sylvestris l is demonstrated for the early to mid holocene in southern scandinavia which indicates that warm summers were compensated for by high winter precipitation based on pine tree limit fluctuations as a measure of mean ablation season temperature holocene variations in winter precipitation at hardangerjokulen have been calculated by substitution in the close exponential relationship between mean ablation season temperature and winter precipitation at the ela of norwegian glaciers setting the winter precipitation during the period ad 1961 1990 at 100 mean values

holocene climate variability and periodicities in south central sweden as interpreted from peat humification analysis analysis of the decomposition of peat has been used to identify climatic shifts over the last 10 000 years in two raised bogs stomyren and kortlandamossen south central sweden age depth curves have been constructed using radiocarbon dates and tephra layers peat humification data have been subjected to spectral analyses using the lomb scargle fourier method and reveal a periodicity of c 250 years in both records cycles of c 200 yr and c 400 yr were found at stomyren and at kortlandamossen respectively these periodicities could correspond to changes in solar activity levels a test estimating the possible level of noise has been applied to the spectral analyses the humification indices indicate prominent shifts to wetter conditions at c 7500 4300 4200 3700 3500 and 2800 2400 cal yr bp the most distinct drier phases start at c 4500 and 3250 cal yr bp

an inverse approach to the course of the little ice age glacier advance and the following deglaciation at austerdalsisen eastern svartisen northern norway the course of the little ice age lia in scandinavia is characterized by large glacier advances that started at about ad 1300 and culminated at about ad 1750 the end of the lia is marked as an unprecedented and ongoing glacier retreat that accelerated from the early 20th century the course of the lia is here presented based on fluctuations of austerdalsisen the largest valley outlet glacier draining the austre svartisen ostisen ice cap nordland northern norway during the lia glacierization austerdalsisen separated into two branches and relative to the present glacier terminus a western valley glacier advanced more than 4 km whereas a se valley glacier advanced about 3 km at present meltwater from austerdalsisen drains towards se if the glacier obtains a critical magnitude however most of the meltwater is drained westwards across a higher overflow gap based on radiocarbon dated lake sediments distal proglacial glaciolacustrine glaciofluvial sediments and historical observations the c

latest pleistocene and holocene glacier variations in the european alps in the alps climatic conditions reflected in glacier and rock glacier activity in the earliest holocene show a strong affinity to conditions in the latest pleistocene younger dryas glacier advances in the alps related to younger dryas cooling led to the deposition of egesen stadial moraines egesen stadial moraines can be divided into three or in some cases even more phases sub stadials moraines of the earliest and most extended advance the egesen maximum stabilized at 12 2 1 0 ka based on 10be exposure dating at the schonferwall tyrol austria and the julier pass outer moraine switzerland final stabilization of moraines at the end of the egesen stadial was at 11 3 0 9 ka as shown by 10be data from four sites across the alps from west to east the sites are piano del praiet northwestern italy grosser aletschgletscher central switzerland julier pass inner moraine eastern switzerland and val viola northeastern italy there is excellent agreement of the 10be ages from the four sites in the earliest holocene glaciers in the northernmost mountain ranges advanced at around 10 8 1 1 ka as shown by 10be data from the kartell site northern tyrol austria in more sheltered drier regions rock glacier activity dominated as shown for example at julier pass and larstig valley tyrol austria new 10be dates presented here for two rock glaciers in larstig valley indicate final stabilization no later than 10 5 0 8 ka based on this data we conclude the earliest holocene between 11 6 and about 10 5 ka was still strongly affected by the cold climatic conditions of the younger dryas and the preboreal oscillation with the intervening warming phase having had the effect of rapid downwasting of egesen glaciers at or slightly before 10 5 ka rapid shrinkage of glaciers to a size smaller than their late 20th century size reflects markedly warmer and possibly also drier climate between about 10 5 ka and 3 3 ka conditions in the alps were not conducive to significant glacier expansion except possibly during rare brief intervals past tree line data from kaunertal tyrol austria in concert with radiocarbon and dendrochronologically dated wood fragments found recently in the glacier forefields in both the swiss and austrian alps points to long periods during the holocene when glaciers were smaller than they were during the late 20th century equilibrium line altitudes ela were about 200 m higher than they are today and about 300 m higher in comparison to little ice age lia elas the larstig rock glacier site we dated with 10be is the type area for a postulated mid holocene cold period called the larstig oscillation presumed age about 7 0 ka our data point to final stabilization of those rock glaciers in the earliest holocene and not in the middle holocene the combined data indicate there was no time window in the middle holocene long enough for rock glaciers of the size and at the elevation of the larstig site to have formed during the short infrequent cold oscillations between 10 5 and 3 3 ka small glaciers less than several km2 may have advanced to close to their lia dimensions overall the cold periods were just too short for large glaciers to advance after 3 3 ka climate conditions became generally colder and warm periods were brief and less frequent large glaciers for example grosser aletschgletscher advanced markedly at 3 0 2 6 ka around 600 ad and during the lia glaciers in the alps attained their lia maximum extents in the 14th 17th and 19th centuries with most reaching their greatest lia extent in the final 1850 1860 ad advance

a theoretical approach to glacier equilibrium line altitudes using meteorological data and glacier mass balance records from southern norway based on a close exponential relationship between mean ablation season temperature and winter precipitation at the equilibrium line altitude ela of 10 norwegian glaciers three equations are derived the e rst equation enables calculation of the minimum altitude of areas climatically suited for glacier formation and is termed the altitude of instantaneous glacierization aig equation 2 is derived based on the principle of terrain adaptation enabling quantie cation of the glacial buildup sensitivity gbs in presently non glaciated areas the theoretical climatic temperature precipitation ela c tp ela in presently non glaciated areas is calculated in equation three by combining gbs with terrain altitude mass balance records from four modern glaciers a lfotbreen nigardsbreen storbreen and gra subreen situated in maritime to continental climate regimes in southern norway are used to test these equations correlation between aig and net balance measure ments bn yielded correlation coefe cients of r 0 80 to r 0 84 calculated aigs correspond well with observed elas on a lfotbreen nigardsbreen and gra subreen while it deviates from the observed ela on storbreen the latter is probably due to leeward accumulation of wind blown snow on this cirque glacier based on this approach regional representative climatic elas can be calculated for non glaciated areas with instrumental records of ablation season temperature and winter precipitation

reconstruction of former glacier equilibrium line altitudes based on proglacial sites an evaluation of approaches and selection of sites abstract various approaches are used to record variations in glacier activity and equilibrium line altitudes elas based on proglacial sites lacustrine and terrestrial these approaches are based on a conceptual model of glacier meltwater induced sedimentation in which the minerogenic nonorganic component of the sediments is related to the occurrence of a glacier in the catchment the principal coupling to former glacier activity and elas is common for these approaches however different methods and techniques may complement each other and both possibilities and limitations are demonstrated site selection for reconstructing variations in glacier activity elas is evaluated and critical factors are discussed rerouting of glacier meltwater streams across local watersheds in combination with proglacial sites gives a distinct on off signal for former glacier activity elas together with representative lateral moraines of known age local watersheds are important for calibrating reconstructed glacier activity elas based on a chain of proglacial lakes based on the modern analogue principle various proxies can record whenever glaciers existed in a catchment in a chain of proglacial lakes with different sensitivity to record variations in glacier activity elas these proxies can be calibrated against independent records for one site approaches however variations in glacier activity elas depend on the interpretation and sensitivity of the proxies used

influence of geomorphological setting fluvial glaciofluvial and mass movement processes on sedimentation in alpine lakes lacustrine sediments are often used for paleoclimate reconstructions as continuous archives of several physical and biological proxies the relation between autochthonous and allochthonous sedimentation in alpine lakes is a complex system that may cause difficulties when interpreting biological and physical parameters results from previous studies of alpine lakes in northern sweden have demonstrated that non glacial processes produce minerogenic lake deposits with similar physical characteristics density loi magnetic susceptibility grain size as those that have been associated with glacier fluctuations in proglacial lakes in this study of two consecutive proglacial alpine lakes we show that fluvial redeposition of alluvial fan deposits significantly affects the holocene lake sedimentation depending on the geomorphological setting such fluvial redeposition signals may actually overprint a glaciofluvial signal we also show that minerogenic laminations of fluvial origin are impossible to separate f

cirque glacier activity in arctic norway during the last deglaciation abstract numerous cirques of the lofoten vesteralen archipelago in northern norway have distinct moraine sequences that previously have been assigned to the allerod younger dryas 13 400 to 11 700 yr bp interval constraining the regional distribution of the equilibrium line altitude ela of cirque and valley glaciers here we present evidence from a once glacier fed lake on southern andoya that contests this view analyses of radiocarbon dated lacustrine sediments including rock magnetic parameters grain size organic matter dry bulk density and visual interpretation suggest that no glacier was present in the low lying cirque during the younger dryas allerod the initiation of the glacial retreat commenced with the onset of the bolling warming 14 700 yr bp and was completed by the onset of allerod interstade 13 400 yr bp the reconstructed glacier stages of the investigated cirque coincide with a cool and dry period from 17 500 to 14 700 yr bp and a somewhat larger last glacial maximum lgm advance possibly occurring between 21 050 and 19 100 yr bp

holocene fluctuations of a polythermal glacier in high alpine eastern jotunheimen central southern norway abstract bukkehammarbreen is a polythermal cirque glacier lying in the permafrost zone of eastern jotunheimen central southern norway in the proglacial lake bukkehammartjorna sediment analyses of loss on ignition loi magnetic susceptibility and analyses of grain size distribution have been used to reconstruct holocene variations in glacier activity and other catchment processes the glacier has low sediment production hence a low signal to noise ratio of minerogenic sediment flux is found grain size analyses are used to enhance the glacigenic signal and to detect glacier variations and other changes in sediment input the sedimentological record from bukkehammartjorn is compared with three other lake records from the same region in order to separate the glacial signal from variations in organic production and episodes of enhanced non glacial minerogenic sedimentation subsequent to the deglaciation after the younger dryas a preboreal glacial advance culminated before 10 100 cal bp this was followed by a prolonged period with no glaciers in the catchment until 7500 cal bp after which there is evidence of limited glacier activity lasting until 6800 cal bp between 6700 and 6000 cal bp the catchment was deglaciated after 6000 cal bp bukkehammarbreen reformed increasing in size towards 3800 cal bp with evidence for reduced glacier activity around 5200 cal bp a glacier with approximately similar size as at present has existed after 3800 cal bp the investigation has demonstrated the usefulness of multi site and multi parameter lacustrine investigations in reconstructing glacier fluctuations and for testing and validating the results the investigations have shown that grain size variations in sediment cores located at increasing distance from the meltwater inlet of a lake may provide an indicator of paraglacial activity in the catchment during the holocene the results also suggest that the lower altitudinal limit of permafrost in eastern jotunheimen remained below about 1800 m during the holocene

mid to late holocene climate change an overview the last 6000 years are of particular interest to the understanding of the earth system because the boundary conditions of the climate system did not change dramatically in comparison to larger glacial interglacial changes and because abundant detailed regional palaeoclimatic proxy records cover this period we use selected proxy based reconstructions of different climate variables together with state of the art time series of natural forcings orbital variations solar activity variations large tropical volcanic eruptions land cover and greenhouse gases underpinned by results from general circulation models gcms and earth system models of intermediate complexity emics to establish a comprehensive explanatory framework for climate changes from the mid holocene mh to pre industrial time the redistribution of solar energy due to orbital forcing on a millennial timescale was the cause of a progressive southward shift of the northern hemisphere nh summer position of the intertropical convergence zone itcz this was accompanied by a pronounced weakening of the monsoon systems in africa and asia and increasing dryness and desertification on both continents the associated summertime cooling of the nh combined with changing temperature gradients in the world oceans likely led to an increasing amplitude of the el nin o southern oscillation enso and possibly increasingly negative north atlantic oscillation nao indices up to the beginning of the last millennium on decadal to multi century timescales a worldwide coincidence between solar irradiance minima tropical volcanic eruptions and decadal to multi century scale cooling events was not found however reconstructions show that widespread decadal to multi century scale cooling events accompanied by advances of mountain glaciers occurred in the nh e g in scandinavia and the european alps this occurred namely during the little ice age lia between ad w1350 and 1850 when the lower summer insolation in the nh due to orbital forcing coincided with solar activity minima and several strong tropical volcanic eruptions the role of orbital forcing in the nh cooling the southward itcz shift and the desertifi cation of the sahara are supported by numerous model simulations other simulations have suggested that the fingerprint of solar activity variations should be strongest in the tropics but there is also evidence that changes in the ocean heat transport took place during the lia at high northern latitudes with possible additional implications for climates of the southern hemisphere sh

holocene and latest pleistocene climate and glacier fluctuations in iceland abstract multiproxy climate records from iceland document complex changes in terrestrial climate and glacier fluctuations through the holocene revealing some coherent patterns of change as well as significant spatial variability most studies on the last glacial maximum and subsequent deglaciation reveal a dynamic iceland ice sheet iis that responded abruptly to changes in ocean currents and sea level the iis broke up catastrophically around 15 ka as the polar front migrated northward and sea level rose indications of regional advance or halt of the glaciers are seen in late allerod early younger dryas time and again in preboreal time due to the apparent rise of relative sea level in iceland during this time most sites contain evidence for fluctuating tidewater glacier termini occupying paleo fjords and bays the time between the end of the younger dryas and the preboreal was characterized by repeated jokulhlaups that eroded glacial deposits by 10 3 ka the main ice sheet was in rapid retreat across the highlands of iceland the holocene thermal maximum htm was reached after 8 ka with land temperatures estimated to be 3 c higher than the 1961 1990 reference and net precipitation similar to modern such temperatures imply largely ice free conditions across iceland in the early to mid holocene several marine and lacustrine sediment climate proxies record substantial summer temperature depression between 8 5 and 8 ka but no moraines have been detected from that time termination of the htm and onset of neoglacial cooling took place sometime after 6 ka with increased glacier activity between 4 5 and 4 0 ka intensifying between 3 0 and 2 5 ka although a distinct warming during the medieval warm period is not dramatically apparent in icelandic records the interval from ca ad 0 to 1200 is commonly characterized by relative stability with slow rates of change the literature most commonly describes little ice age moraines ca ad 1250 1900 as representing the most extensive ice margins since early holocene deglaciation with temperature depressions of 1 2 c compared to the ad 1961 1990 average steep north south and west east temperature gradients are reconstructed in the holocene records of iceland suggesting a strong maritime influence on the terrestrial climate of iceland

paleoclimatic implications based on equilibrium line altitude depressions of reconstructed younger dryas and holocene cirque glaciers in inner nordfjord western norway abstract relative to a present cirque glacier in innner nordfjord western norway equilibrium line altitude ela depressions for reconstructed cirque glaciers formed during the younger dryas 11 000 10 000 yr b p the erdalen event 9100 200 yr b p and the little ice age mid 18th century are calculated by the use of accumulation area ratio aar and compared to the corresponding values for plateau glaciers the temperature precipitation ela tp ela as reflected by plateau glaciers gives considerably larger ela depressions than use of the temperature precipitation wind ela tpw ela for cirque glaciers ela depressions during the younger dryas erdalen event and the little ice age thus strongly indicate that cirque glaciers are much more sensitive to changes in winter precipitation than plateau glaciers the difference in ela depressions of contemporaneous plateau and cirque glaciers during the younger dryas erdalen event and the little ice age suggests that winter precipitation was reduced to 59 7 71 6 and 88 7 compared to present values taken into account the reduced winter precipitation the corresponding mean ablation season temperature depressions were probably 4 3 0 3 3 0 0 2 0 3 and 1 4 0 3 0 2 c respectively

the use of hypsometry to indicate long term stability and response of valley glaciers to changes in mass transfer a simple equation is derived relating the net mass balance and hypsometric curves of a steady state valley glacier it is used to examine how valley shape is linked to disparate extents and responses of glaciers subjected to similar climatic conditions examples are given which show that area based indices e g aar for estimating the equilibrium line altitude ela may be subject to a substantial built in variance because they implicitly rely upon similarity of glacier shape and regimen over a region if accurate topographic maps are available the equation may be used to infer the regimen of modern glaciers in the form of a dimensionless ratio of net mass balance gradients alternatively if similar information is available concerning regional glacier regimen disparate extents and responses may be collectively utilized to estimate values of ela or to infer climatic influence taking glacier hypsometry into account

palaeoenvironmental change and glacier fluctuations in the high tian shan mountains during the last millennium based on sediments from lake ala kol kyrgyzstan abstract a suite of limnological proxies measured in clastic sediments of the glacier fed lake ala kol ne kyrgyzstan document palaeoenvironmental change and glacier fluctuations in the central tian shan over the last millennium rock magnetic and geochemical data provide supporting evidence for three glacier expansion episodes occurring in 1200 1400 ce 1500 1850 ce and 1900 1950 ce and glacier retreat periods during 1000 1200 ce and the intervening periods the maximal glacier extent as inferred from high lf si inc coh ca inc coh and low arm30 arm is recorded between 1500 and 1850 ce and corresponds to cold and wet conditions during the little ice age in the high central tian shan periods of glacier waxing and waning recorded at lake ala kol present a close correspondence to ice accumulation rate in the northern tibetan plateau suggesting that precipitation changes are the main driver of glacier fluctuations in central tian shan during the last millennium although temperature may have exerted a more complex influence on centennial timescales

late holocene glacier growth in svalbard documented by subglacial relict vegetation and living soil microbes much renewed research interest in arctic regions stems from the increasing concentration of atmospheric greenhouse gases and the alleged climatic sensitivity of high latitude areas glacier and permafrost changes are among a number of proxies used for monitoring past and present arctic climate change here we present observations on frozen in situ soil and vegetation found below cold based glacier longyearbreen 78813 n 2 km upstream from the present glacier terminus dating of the relict vegetation indicates that the glacier has increased in length from about 3 km to its present size of about 5 km during the last c 1100 years the meteorological setting of non surging longyearbreen suggests this example of late holocene glacier growth represents a widespread phenomenon in svalbard and in adjoining arctic regions in addition we use the subglacial permafrozen soil system to evaluate microbial survival capacity over considerable time periods and we present evidence for microbes having survived more than 1100 years in a subglacial permafrozen state

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

lateglacial and early holocene palaeoclimatic reconstruction based on glacier fluctuations and equilibrium line altitudes at northern folgefonna hardanger western norway northern folgefonna c 23 km 2 is a nearly circular maritime ice cap located on the folgefonna peninsula in hardanger western norway by combining the position of marginal mor aines with ams radiocarbon dated glacier meltwater induced sediments in proglacial lakes draining northern folgefonna a continuous high resolution record of variations in glacier size and equili brium line altitudes elas during the lateglacial and early holocene has been obtained after the termination of the younger dryas c 11 500 cal yr bp a short lived 100 150 years climatically induced glacier readvance termed the jondal event 1 occurred within the preboreal oscillation pbo c 11 100 cal yr bp bracketed to 10 550 10 450 cal yr bp a second glacier readvance is named the jondal event 2 a third readvance occurred about 10 000 cal yr bp and corresponds with the erdalen event 1 recorded at jostedalsbreen an exponential relationship between mean solid winter precipitation and ablation season temperature at the ela of norwegian glaciers is used to reconstruct former variations in winter precipitation based on the corresponding ela and an indepen dent proxy for summer temperature compared to the present the younger dryas was much colder and drier the jondal event 1 pbo was colder and somewhat drier and the jondal event 2 was much wetter the erdalen event 1 started as rather dry and terminated as somewhat wetter varia tions in glacier magnitude elas and corresponding palaeoclimatic reconstructions at northern folge fonna suggest that low altitude cirque glaciers lowest altitude of marginal moraines 290 m in the area existed for the last time during the younger dryas these low altitude cirque glaciers of sug gested younger dryas age do not fit into the previous reconstructions of the younger dryas ice sheet in hardanger copyright 2005 john wiley sons ltd

utilizing physical sediment variability in glacier fed lakes for continuous glacier reconstructions during the holocene northern folgefonna western norway the maritime plateau glacier of northern folgefonna in western norway has a short subdecadal response time to climatic shifts and is therefore well suited for reconstructing high resolution glac

holocene glacier fluctuations of flatebreen and winter precipitation changes in the jostedalsbreen region western norvay based on glaciolacustrine sediment records the history of holocene glacier variations of flatebreen an independent glacier close to the sw part of the jostedalsbreen ice cap has been reconstructed from lacustrine sediments in the proglacial lake jarbuvatnet the sedimentary succession shows evidence of three maini episodes of holocene glacier expansion the first is recorded in the basal part of the core up to 370 cm according to the age depth relationship in the sediment core based on 12 ams radiocarbon dates this glacier expansion episode terminated about 10200 cal yr bp the second major glacier phase lasted from 8400 to 8100 cal yr bp while the third was initiated around 4000 cal yr bp and has continued up to the present at 43 cm in the core the medium silt content increases significantly accompanied by a minor increase in the sand content this textural change is interpreted as the first time that the tenninus of flatebreen extended inlto an upstream lake at 1083 m a s l the age model suggests that this event took place around

effects of strongly temperature dependent viscosity on time dependent three dimensional models of mantle convection numerical simulations of thermal convection in a wide 8 8 1 cartesian box heated from below with temperature dependent viscosity contrasts of 1000 and rayleigh number 105 show that boundary conditions and aspect ratio have an enormous effect on the preferred flow pattern with rigid upper and lower boundaries spoke pattern flow with small diameter 1 5 cells is obtained consistent with laboratory experiments and previous numerical results however with the arguably more realistic stress free boundaries the flow chooses the largest possible wavelength forming a single square cell of aspect ratio 8 with one huge cylindrical downwelling surrounded by upwelling sheets the addition of stress dependence to the rheology weakens the stiff upper boundary layer resulting in smaller cells though still with upwelling sheets and downwelling plumes