detrital carbonate peaks on the labrador shelf a 13 7 ka template for freshwater forcing from the hudson strait outlet of the laurentide ice sheet into the subpolar gyre abstract the laurentide ice sheet lis was a large dynamic ice sheet in the early holocene the glacial events through hudson strait leading to its eventual demise are recorded in the well dated labrador shelf core md99 2236 from the cartwright saddle we develop a detailed history of the timing of ice sheet discharge events from the hudson strait outlet of the lis during the holocene using high resolution detrital carbonate ice rafted detritus ird 18o and sediment color data eight detrital carbonate peaks dcps associated with ird peaks and light oxygen isotope events punctuate the md99 2236 record between 11 5 and 8 0 ka we use the stratigraphy of the dcps developed from md99 2236 to select the appropriate r to calibrate the ages of recorded glacial events in hudson bay and hudson strait such that they match the dcps in md99 2236 we associate the eight dcps with h0 gold cove advance noble inlet advance initial retreat of the hudson strait ice stream hsis from hudson strait opening of the tyrrell sea and drainage of glacial lakes agassiz and ojibway the opening of foxe channel and retreat of glacial ice from foxe basin are represented by a shoulder in the carbonate data r of 350 years applied to the radiocarbon ages constraining glacial events h0 through the opening of the tyrell sea provided the best match with the md99 2236 dcps r values and ages from the literature are used for the younger events a very close age match was achieved between the 8 2 ka cold event in the greenland ice cores dcp7 8 15 ka bp and the drainage of glacial lakes agassiz and ojibway our stratigraphic comparison between the dcps in md99 2236 and the calibrated ages of hudson strait bay deglacial events shows that the retreat of the hsis the opening of the tyrell sea and the catastrophic drainage of glacial lakes agassiz and ojibway at 8 2 ka are separate events that have been combined in previous estimates of the timing of the 8 2 ka event from marine records sw iceland shelf core md99 2256 documents freshwater entrainment into the subpolar gyre from the hudson strait outlet via the labrador north atlantic and irminger currents the timing of freshwater release from the lis hudson strait outlet in md99 2236 matches evidence for freshwater forcing and lis icebergs carrying foreign minerals to the sw iceland shelf between 11 5 and 8 2 ka the congruency of these records supports the conclusion of the entrainment of freshwater from the retreat of the lis through hudson strait into the subpolar gyre and provides specific time periods when pulses of lis freshwater were present to influence climate

linking the 8 2 ka event and its freshwater forcing in the labrador sea 1 the 8 2 ka event was the last deglacial abrupt climate event a reduction in the atlantic meridional overturning circulation amoc attributed to the drainage of glacial lake agassiz may have caused the event but the freshwater signature of lake agassiz discharge has yet to be identified in 18o of foraminiferal calcite records from the labrador sea calling into question the connection between freshwater discharge to the north atlantic and amoc strength using mg ca paleothermometry we demonstrate that 3 c of near surface ocean cooling masked an 1 0 decrease in western labrador sea 18o of seawater concurrent with lake agassiz drainage comparison with north atlantic 18o of seawater records shows that the freshwater discharge was transported to regions of deep water formation where it could perturb amoc and force the 8 2 ka event

using relative sea level data to constrain the deglacial and holocene history of southern greenland this paper presents new holocene relative sea level rsl data collected from isolation basins close to the town of paamiut in south west greenland the data shows a rapid fall from a marine limit of c 52 m asl at c 10 9 cal ka bp to close to present by c 9 5 cal ka bp at rates of up to c 32 mm yr falling below present for the majority of the holocene before rising to present in the last 2000 years the elevation of the rsl lowstand is not well constrained but was at least below 3 m this pattern of rapid rsl fall during the early holocene matches the pattern seen at other southern greenland locations suggesting rapid largely simultaneous ice retreat from the area surrounding the qassimiut lobe at the start of the holocene occurring c 2000 years after the initial deglaciation of the extreme southern tip of greenland the rsl histories from this and other southern greenland locations are distinct to those recorded further north along the west coast and are in broad agreement with a pattern of vertical land motion and rsl predicted by the huy2 model simpson et al 2009 which predicts an 80 m drop in the contribution of vertical land motion to rsl at 10 cal ka bp between sisimiut and paamiut on the west coast despite this broad scale spatial agreement between the rsl data and the huy2 model it fails to satisfactorily predict the holocene rsl histories at paamiut and other southern greenland locations sensitivity tests indicate that the data model misfits are most likely due to an over estimate of the forcing during the holocene thermal maximum or the response to this forcing in southern greenland and error in the north american ice sheets component of the background deglaciation model our new data suggests that much of the southern part of the ice sheet acted differently to the area further north however rsl changes at paamiut are also largely impacted by regional and larger scale processes including a bulls eye of uplift centred on the west the impact of the holocene thermal maximum and the influence of the collapse of the north american ice sheets

late holocene expansion of istorvet ice cap liverpool land east greenland abstract the greenland ice sheet is undergoing dynamic changes that will have global implications if they continue into the future in this regard an understanding of how the ice sheet responded to past climate changes affords a baseline for anticipating future behavior small independent ice caps adjacent to the greenland ice sheet hereinafter called local ice caps are sensitive indicators of the response of greenland ice marginal zones to climate change therefore we reconstructed late holocene ice marginal fluctuations of the local istorvet ice cap in east greenland using radiocarbon dates of subfossil plants 10 be dates of surface boulders and analyses of sediment cores from both threshold and control lakes during the last termination the istorvet ice cap had retreated close to its maximum holocene position by 11 730 cal yr bp radiocarbon dates of subfossil plants exposed by recent recession of the ice margin indicate that the istorvet cap was smaller than at present from ad 200 to ad 1025 sediments from a threshold lake show no glacial input until the ice cap advanced to within 365 m of its holocene maximum position by ad 1150 thereafter the ice cap remained at or close to this position until at least ad 1660 the timing of this the most extensive of the holocene expansion is similar to that recorded at some glaciers in the alps and in southern alaska however in contrast to these other regions the expansion in east greenland at ad 1150 appears to have been very close to if not at a maximum holocene value comparison of the istorvet ice cap fluctuations with holocene glacier extents in southern hemisphere middle to high latitude locations on the antarctic peninsula and in the andes and the southern alps suggests an out of phase relationship if correct this pattern supports the hypothesis that a bipolar see saw of oceanic and or atmospheric circulation during the holocene produced asynchronous glacier response at some localities in the two polar hemispheres

abrupt holocene climate transitions in the northern north atlantic region recorded by synchronized lacustrine records in iceland abstract two high sediment accumulation rate icelandic lakes the glacial lake hvitarvatn and the non glacial lake haukadalsvatn contain numerous tephra layers of known age which together with high resolution paleomagnetic secular variations allow synchronization with a well dated marine core from the shelf north of iceland a composite standardized climate record from the two lakes provides a single time series that efficiently integrates multi proxy data that reflect the evolution of summer temperatures through the holocene the first order trends in biogenic silica bsi 13c and c n rise relatively abruptly following deglaciation reaching maximum values shortly after 8 ka following a complex minimum between 8 7 and 8 0 ka the holocene thermal maximum htm in the lakes is marked by all proxies with a sharp transition out of the 8 ka cold event into peak summer warmth by 7 9 ka and continuing warm with some fluctuations until 5 5 ka decreasing summer insolation after the htm is reflected by incremental cooling initially 5 5 ka with subsequent cold perturbations recorded by all proxies 4 3 to 4 0 ka and 3 1 to 2 8 ka the strongest disturbance occurred after 2 ka with initial summer cooling occurring between 1 4 and 1 0 ka followed by a more severe drop in summer temperatures after 0 7 ka culminating between 0 5 and 0 2 ka following each late holocene cold departure bsi re equilibrated at a lower value independent of the sediment accumulation rate some of the abrupt shifts may be related to icelandic volcanism influencing catchment stability but the lack of a full recovery to pre existing values after the perturbation suggests increased periglacial activity decreased vegetation cover and glacier growth in the highlands of iceland the similarity in timing direction and magnitude of our multi proxy records from glacial and non glacial lakes and from the adjacent marine shelf suggests that our composite record reflects large scale shifts in ocean atmosphere circulation throughout the northern north atlantic

holocene environmental variability in southern greenland inferred from lake sediments abstract sediments from qipisarqo lake provide a continuous holocene paleoenvironmental record from southern greenland following deglaciation and glacio isostatic emergence of the basin from the sea 9100 cal yr b p proxies of lake paleoproductivity including biogenic silica and organic matter increased markedly until 6000 cal yr b p and thereafter remained stable over the ensuing warm three millennia subsequent decreases in these proxies most dramatically between 3000 and 2000 cal yr b p show the lake s responses to initial neoglacial cooling intervals of ameliorated limnological conditions occurred between 1300 and 900 and between 500 and 280 cal yr b p briefly interrupting the decreasing trend in productivity that culminated in the little ice age increased lake productivity during the latter half of the 20th century which reflects the limnological response to circum arctic warming still has not reached peak holocene values the neoglacial climate of the last 2000 yr includes the most rapid high amplitude environmental changes of the past nine millennia the norse thus migrated around the north atlantic ocean region in the most environmentally unstable period since deglaciation lacustrine sediment records provide a context with which to consider future environmental changes in the labrador sea region in particular any future warming will be superposed on a regional climate system that is currently exhibiting highly unstable behavior at submillennial timescales

dinocyst based reconstructions of sea ice cover concentration during the holocene in the arctic ocean the northern north atlantic ocean and its adjacent seas abstract sea ice cover extent expressed in terms of mean annual concentration was reconstructed from the application of the modern analogue technique to dinocyst assemblages the use of an updated database which includes 1492 sites and 66 taxa yields sea ice concentration estimates with an accuracy of 1 1 10 holocene reconstructions of sea ice cover were made from dinocyst counts in 35 cores of the northern north atlantic and arctic seas in the canadian arctic the results show high sea ice concentration 7 10 with little variations throughout the interval in contrast in arctic areas such as the chukchi sea and the barents sea the reconstructions show large amplitude variations of sea ice cover suggesting millennial type oscillations with a pacing almost opposite in western vs eastern arctic other records show tenuous changes with some regionalism either in trends or sea ice cover variability during the mid holocene and notably at 6 0 5 ka minimum sea ice concentration is recorded in the eastern fram strait northern baffin bay and labrador sea however this minimum cannot be extrapolated at the scale of the arctic and circum arctic the comparison of recent observations and reconstructions suggests larger variations in the arctic sea ice cover during the last decades than throughout the holocene

holocene climate changes in southern greenland evidence from lake sediments a holocene lake sediment record is presented from lake n14 situated on angissoq island 15 km off the main coast of southern greenland the palaeoclimatic development has been interpreted on the basis of flux and percentage content of biogenic silica clastic material organic material and sulphur as well as sedimentation rate moss content and magnetic susceptibility a total of 43 radiocarbon dates has ensured a reliable chronology it is argued that varying sediment composition mainly reflects changing precipitation by analogy with the present meteorological conditions in southern greenland holocene climate development is inferred between 11550 and 9300 cal yr bp temperature and precipitation increase markedly but this period is climatically unstable from 9300 yr bp conditions become more stable and a holocene climatic optimum characterised by warm and humid conditions is observed from 8000 to 5000 cal yr bp from 4700 cal yr bp the first signs of a climatic deterioration are observed and from 3700 cal yr bp the climate has become more dry and cold superimposed on the climatic long term trend is climate variability on a centennial time scale that increases in amplitude after 3700 cal yr bp a climatic scenario related to the strength and position of the greenland high pressure cell and the iceland low pressure cell is proposed to explain the holocene centennial climate variability a comparison of the lake n14 record with a terrestrial as well as a marine record from the eastern north atlantic ocean suggests that the centennial climate variability was uniform over large areas at certain times less

anomalously mild younger dryas summer conditions in southern greenland the first late glacial lake sediments found in greenland were analyzed with respect to a variety of environmental variables the analyzed sequence covers the time span between 14400 and 10500 calendar yr b p and the data imply that the conditions in southernmost greenland during the younger dryas stadial 12800 11550 calendar yr b p were characterized by an arid climate with cold winters and mild summers preceded by humid conditions with cooler summers climate models imply that such an anomaly may be explained by local climatic phenomenon caused by high insolation and fohn effects it shows that regional and local variations of younger dryas summer conditions in the north atlantic region may have been larger than previously found from proxy data and modeling experiments

early to middle holocene valley glaciations on northernmost greenland abstract this paper presents the glacial stratigraphy and palaeoenvironmental evolution around constable bugt johannes v jensen land located on the north coast of greenland this is a land of extreme climate polar desert conditions and a coast bound by a permanent sea ice cover our data covers the period from the last glacial maximum lgm 18 22 cal ka bp into the holocene it records the history of a shelf based glaciation with ice flowing eastward along the coast as well as two local valley glacier advances from the south during the holocene with ice on the coastal plain during the lgm glaciolacustrine basins formed in marginal positions and in ice dammed valleys to the south into the mountainous area of peary land with the break up of shelf based ice there was a gradual marine inundation at which the marine limit formed at 45 m a s l this initial early holocene ice advance from the south formed prominent valley mouth moraines especially in sifs valley here both glaciolacustrine and marine sediments were remoulded and or dislocated as thrust blocks into a moraine ridge spanning more than 1 km in width and 60 m in height radiocarbon ages of sediments incorporated in this moraine as well as from on lapping sediments suggest that the moraine formed between 9 6 and 6 3 cal ka bp based on 14 c dating results the youngest ice advance phase can be narrowed down to 14 c ages between 5 5 5 0 cal ka bp the recorded ice advances took place during the holocene thermal maximum htm for north greenland the last one close to the beginning of the neoglacial cooling during the htm we have recorded a period of 2500 years during which the north coast of greenland as opposed to today experienced an absence to very restricted occurrence of land fast or multi year sea ice this observation can be explained by the altitudinal and temporal distribution of beach ridge complexes that must have formed by wave action and thus requiring at least partial open water conditions with a moisture source at hand we propose that this lead to enhanced precipitation in the near coastal areas which coupled to documented htm cold reversals caused a lowered glaciation limit and led to a positive mass balance and subsequent ice advance

fluctuations of local glaciers in greenland during latest pleistocene and holocene time abstract this paper is the first to summarize research on fluctuations of local glaciers in greenland e g ice caps and mountain glaciers independent of the greenland ice sheet during latest pleistocene and holocene time in contrast to the extensive data available for fluctuations of the greenland ice sheet surprisingly little data exist to constrain local glacier extents much of the available research was conducted prior to wide spread use of ams radiocarbon dating and the advent of surface exposure and luminescence dating although there is a paucity of data generally similar patterns of local glacier fluctuations are observed in all regions of greenland and likely reflect changes in paleoclimate which must have influenced at least the margins of the inland ice absolute age data for late glacial and early holocene advances of local glaciers are reported from only two locations disko island and the scoresby sund region subsequent to late glacial or early holocene time most local glaciers were smaller than at present or may have disappeared completely during the holocene thermal maximum in general local glacier advances that occurred during historical time 1200 1940 ad are the most extensive since late glacial or early holocene time historical documents and more recent aerial photographs provide useful information about local glacier fluctuations during the last 100 yrs in all but one area north greenland local glaciers are currently receding from historical extents

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

anomalies of mantle derived helium during the 1997 1998 seismic swarm of umbria marche italy more than 100 he 4he isotope ratios were measured in co2 dominated gas samples collected during the 1997 1998 seismic crisis that shook the umbria marche central apennines italy although the gas emissions were located in a typical crustal environment the measured values delineate variable mixing proportions between mantle derived and crustal helium during the monitoring period anomalous he 4he ratios were observed together with a significant increase of fluid outflows the observed he 4he anomalies appear to be driven by stress induced crustal deformations affecting micro fracturing and bulk permeability and in turn by a seismogenic induced modification of the crustal permeability of rocks since crustal deformations can also occur aseismically the geochemical anomalies must be considered indicators of processes occurring below the surface which could eventually help to estimate the probability increase of an impending earthquake instead of pure empirical precursors

spatial and temporal variability of holocene temperature in the north atlantic region the early holocene climate of the north atlantic region was influenced by two boundary conditions that were fundamentally different from the present the presence of the decaying laurentide ice sheet lis and higher than present summer solar insolation in order to assess spatial and temporal patterns of holocene climate evolution across this region we collated quantitative paleotemperature records at sub millennial resolution and synthesized their temporal variability using principal components analysis pca the analysis reveals considerable spatial variability most notably in the time transgressive expression of the holocene thermal maximum htm most of the region but especially areas peripheral to the labrador sea and hence closest to the locus of lis disintegration experienced maximum holocene temperatures that lagged peak summer insolation by 1000 3000 years many sites from the northeastern north atlantic sector including the nordic seas and scandinavia either warmed in phase with maximum summer insolation 11 000 9000 years ago or were less strongly lagged than the baffin bay labrador sea region these spatially complex patterns of holocene climate development which are defined by the pca resulted from the interplay between final decay of the lis and solar insolation forcing

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

mass balance and equilibrium line altitudes of glaciers in high mountain environments abstract the mass balance characteristics of glaciers in high mountain environments complicate the relationship between glacier equilibrium line altitudes elas and climatic variables such as precipitation and air temperature therefore methods of ela reconstruction employed in low relief environments are commonly not applicable in high mountains or require some modification we review the concept of the ela with reference to the mass balance of a range of glacier types found in high mountain regions we examine the applicability of several commonly used methods of ela reconstruction for different glacier types and propose some general principles to guide the choice of appropriate methods

restricted impact of holocene climate variations on the southern greenland ice sheet abstract we use an ice marginal threshold lake lower nordboso in southern greenland to record episodes when the southern greenland ice sheet sgis was close to the present extent represented by beds of clastic sediments whereas gyttja deposition reflects periods when the glacier was behind the threshold and no glacial meltwater input the results show that the sedimentation was initiated at c 10 6 cal ka bp when the ice margin had reached the present extent following the deglaciation after this the ice margin remained close to the present extent until c 6 9 cal ka bp when it retreated behind the threshold and first reappeared with a clear glacial signal at c 3 0 2 8 cal ka bp and from c 0 5 cal ka bp until the present an overall good correlation between clastic input into lower nordboso and ird events from narsaq sound suggests that they represent a general glacial proximity signal of the sgis our data demonstrates that the sgis behaved less vigorously to holocene climate changes compared to previous reconstructions the ice sheet only retreated behind the present ice extent from c 6 9 to 3 0 cal ka bp and c 2 8 to 0 5 cal ka bp in the mountainous southern greenland whereas the more sensitive low lying qassimiut lobe was behind its present margin from c 9 ka until the little ice age accordingly the ice marginal behavior in southern greenland is not only governed by climate changes but also strongly influenced by the local topographic setting

the lacustrine sedimentary sequence in sygneskardvatnet western norway a continuous high resolution record of the jostedalsbreen ice cap during the holocene abstract two lacustrine sediment cores from sygneskardvatnet sunndalen confirm that at least the northern part of the jostedalsbreen ice cap melted away during the atlantic chronozone between 6475 and 5300 14 c yr bp 7340 and 6150 cal bp possibly interrupted for short intervals of glacier activity around 6000 and 5800 14 c yr bp 6900 and 6700 cal bp prior to this periods of glacier expansion culminated at ca 8500 8400 8200 7750 7600 and 7400 cal bp the 8400 8200 cal bp advances are correlated with the widespread 8200 event finse event recorded in greenland ice cores lacustrine and proglacial sites and marine sediments during the early part of the holocene periods of glacier contraction culminated at ca 8450 8300 7900 7500 and 6250 cal bp of which the last represents climatic optimum conditions lowest supply of minerogenic sediments and or highest organic production the sedimentary record also shows that the ice cap has existed continuously since 5300 14 c yr bp 6150 cal bp neoglaciation involved three main phases 1 6150 4500 cal bp 2 4500 2700 cal bp 3 2700 cal bp to the present and a series of low amplitude glacier advances which occurred at 6000 5800 5700 5600 5500 5200 5100 4900 4800 4700 4550 4450 4300 4200 4150 4050 4000 3900 3800 3550 3300 2550 2450 2350 2250 2150 2000 1800 1700 1600 1400 1300 1150 1050 and the 1000 cal bp including the little ice age loss on ignition analyses indicate however that episodes of less glacier activity occurred during the mid and late holocene at around 5900 5800 5550 5450 5300 5050 4850 4750 4500 4400 4100 3950 3700 3450 3100 2650 2500 2400 2300 2200 1850 1700 1550 1350 1250 1050 1000 cal bp and during the twentieth century altogether the lacustrine record from sygneskardvatnet indicates that the holocene has been interrupted by 41 periods of increased glacier activity mean return period of ca 150 years and by 36 events of glacier contraction mean return period of 210 years spectral analysis of the loi data show peaks at periods of about 50 85 110 250 285 500 and 2000 calendar years the mean time resolution in core sygneskardvatnet 2 is ca 20 yr cm 1 while the mean sedimentation rate is 0 5 mm yr 1

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

a new present day temperature parameterization for greenland near surface air temperature 2 m over the greenland ice sheet gris is parameterized using data from automatic weather stations located on land and on the ice sheet the parameterization is expressed in terms of mean annual temperatures and mean july temperatures both depending linearly on altitude latitude and longitude the temperature parameterization is compared to a previous study and is shown to be in better agreement with observations the temperature parameterization is tested in a positive degree day model to simulate the present 1996 2006 mean melt area extent of the gris the model accounts for firn warming rainfall and refreezing of meltwater with different degree day factors for ice and snow under warm and cold climate conditions the simulated melt area extent is found to have reasonable agreement with satellite derived observations

holocene fluctuations of bregne ice cap scoresby sund east greenland a proxy for climate along the greenland ice sheet margin abstract the greenland ice sheet is a major component of the arctic cryosphere and the magnitude of its response to future climate changes remains uncertain longer term records of climate near the ice sheet margin provide information about natural climate variability and can be used to understand the causes of past changes in the greenland ice sheet as a proxy for holocene climate near the ice sheet margin we reconstruct the fluctuations of bregne ice cap in the scoresby sund region of central east greenland bregne is a small ice cap 2 5 km 2 in area and responds sensitively to summer temperatures we employ a multi proxy approach to reconstruct the ice cap fluctuations using geomorphic mapping 10 be ages of boulders and bedrock and lake sediment records past extents of bregne ice cap are marked by moraines and registered by sediments in downvalley lakes 10 be ages of bedrock and boulders outboard of the moraines indicate that bregne ice cap was within 250 m of its present day limit by at least 10 7 ka multi proxy data from sediments in two move lake located downvalley from bregne ice cap indicate that the ice cap likely completely disappeared during early and middle holocene time increasing magnetic susceptibility and percent clastic material from 6 5 to 1 9 cal ka bp in two move lake sediments suggest progressively colder conditions and increased snow accumulation on the highlands west of the lake laminated silt deposited at 2 6 cal ka bp and 1 9 cal ka bp to present registers the onset and persistence of bregne ice cap during the late holocene 10 be ages of boulders on an unweathered unvegetated moraine in the bregne ice cap forefield range from 0 74 to 9 60 ka the youngest 10 be age 0 74 ka likely represents the age of the moraine whereas older ages may be due to 10 be inherited from prior periods of exposure this late holocene moraine marks the second largest advance of the ice cap since deglaciation of the region at the end of the last ice age the oldest moraine in the forefield dates to 2 6 cal ka bp the fluctuations of bregne ice cap were likely influenced by northern hemisphere summer insolation throughout the holocene and abrupt late holocene cold events

the effect of nutrient rich effluents from shrimp farming on mangrove soil carbon storage and geochemistry under semi arid climate conditions in northern brazil a semi arid mangrove estuary system in the northeast brazilian coast ceara state was selected for this study to i evaluate the impact of shrimp farm nutrient rich wastewater effluents on the soil geochemistry and organic carbon oc storage and ii estimate the total amount of oc stored in mangrove soils 0 40 cm wastewater affected mangrove forests were referred to as wam and undisturbed areas as non wam redox conditions and oc content were statistically correlated p 400 mv in non wam soils and significantly higher from 66 to 411 mv in the dry season p 0 01 oc contents 0 40 cm soil depth were significantly higher p 0 01 in the wet season than the dry season and higher in non wam soils than in wam soils values of 8 1 and 6 7 kg m 2 in the wet and dry seasons respectively for non wam and values of 3 8 and 2 9 kg m 2 in the wet and dry seasons respectively for wam soils p 0 01 iron partitioning was significantly dependent p 0 05 on type of land use with a smaller degree of pyritization and lower fe pyrite presence in wam soils compared to non wam soils basal respiration of soil sediments was significantly influenced p 0 01 by type of land use with highest co2 flux rates measured in the wam soils mean values of 0 20 mg co2 h 1 g 1 c vs 0 04 mg co2 h 1 g 1 c the oc storage reduction in wam soils was potentially caused i by an increase in microbial activity induced by loading of nutrient rich effluents and ii by an increase of strong electron acceptors e g no3 that promote a decrease in pyrite concentration and hence a reduction in soil oc burial the current estimated oc stored in mangrove soils 0 40 cm in the state of ceara is approximately 1 million t

an aerial view of 80 years of climate related glacier fluctuations in southeast greenland both marine and land terminating glaciers in southeast greenland have experienced dramatic recent retreat an 80 year record of historical aerial photographs and satellite imagery shows that many land terminating glaciers in this region retreated more rapidly in the 1930s than today whereas marine terminating glaciers have retreated faster in the 2000s