late weichselian and holocene sedimentary palaeoenvironment and glacial activity in the high arctic van keulenfjorden spitsbergen high arctic fjords for example van keulenfjorden on spitsbergen provide valuable palaeoenvironmental archives as they typically contain landforms and sediment sequences that document past changes in glacial activity with high temporal resolution van keulenfjorden was covered with a grounded glacier during the last glacial and it was deglaciated between c 11 8 and 11 3 cal ka bp the retreat of the ice front accelerated from approximately 80 to 190 m a during the deglaciation the maximum late holocene glacier extent occurred after surge like advances of the glacier nathorstbreen between 2790 and 2610 cal yr bp i e during a period with the coldest climatic conditions on svalbard this maximum extent was reached approximately 2600 years earlier than inferred for most fjords on svalbard suggesting that surge like glacier advances on svalbard can occur under variable climatic conditions the time interval between the advances of nathorstbreen around 2 7 ka bp was approximately 100 150 years this is comparable to the last and only historically known quiescent phase of nathorstbreen of c 120 years between the late 19th century and the most recent surge from 2003 to 2012

the role of oceanic forcing in mid holocene northern hemisphere climatic change previous model investigations suggested that changes in orbital forcing and feedbacks associated with northward expansion of the boreal forest were both required to explain the full magnitude of enhanced high latitude northern hemisphere summer warming at 6 ka thus implying that biospheric feedbacks decreased planetary albedo associated with forest expansion may be large in the future foley et al 1994 tempo testing earth system models with paleo observations 1996 before the magnitude of past biospheric and other feedbacks can be estimated with confidence however the role of realistic high latitude oceanic forcing i e sea surface temperature sst increases and sea ice reductions should also be considered here we review existing paleoceanographic observations that suggest portions of the north atlantic were up to 4 c warmer than today at 6 ka we then combine our estimates of mid holocene north atlantic sst and sea ice conditions with new climate model simulations to suggest that a significant portion of high latitude summer warming at 6 ka in the northern hemisphere can be accounted for by altered orbital forcing ssts and sea ice relative to today our results underscore the importance of incorporating realistic boundary conditions when using paleoenvironmental data to evaluate the climate system s sensitivity to altered forcing and suggest that high latitude oceanic feedbacks were major contributors to enhanced high latitude summer warming in the northern hemisphere at 6 ka

the seasonal water temperature cycle in the arctic dicksonfjord svalbard during the holocene climate optimum derived from subfossil arctica islandica shells future climate change will have significant effects on ecosystems worldwide and on polar regions in particular hence palaeo environmental studies focussing on the last warmer than today phase i

permafrost and climate in europe monitoring and modelling thermal geomorphological and geotechnical responses we present a review of the changing state of european permafrost within a spatial zone that includes the continuous high latitude arctic permafrost of svalbard and the discontinuous high altitude mountain permafrost of iceland fennoscandia and the alps the paper focuses on methodological developments and data collection over the last decade or so including research associated with the continent scale network of instrumented permafrost boreholes established between 1998 and 2001 under the european union pace project data indicate recent warming trends with greatest warming at higher latitudes equally important are the impacts of shorter term extreme climatic events most immediately reflected in changes in active layer thickness a large number of complex variables including altitude topography insolation and snow distribution determine permafrost temperatures the development of regionally calibrated empirical statistical models and physically based process oriented models is described and it is shown that though more complex and data dependent process oriented approaches are better suited to estimating transient effects of climate change in complex mountain topography mapping and characterisation of permafrost depth and distribution requires integrated multiple geophysical approaches and recent advances are discussed we report on recent research into ground ice formation including ice segregation within bedrock and vein ice formation within ice wedge systems the potential impacts of climate change on rock weathering permafrost creep landslides rock falls debris flows and slow mass movements are also discussed recent engineering responses to the potentially damaging effects of climate warming are outlined and risk assessment strategies to minimise geological hazards are described we conclude that forecasting changes in hazard occurrence magnitude and frequency is likely to depend on process based modelling demanding improved understanding of geomorphological process response systems and their impacts on human activity

a 5500 year oxygen isotope record of high arctic environmental change from southern spitsbergen the oxygen isotope composition of chironomid head capsules in a sediment core spanning the past 5500 years from lake svartvatnet in southern spitsbergen was used to reconstruct the oxygen isotope composition of lake water 18olw and local precipitation the 18olw values display shifts from the baseline variability consistent with the timing of recognized historical climatic episodes such as the roman warm period the dark ages cold period and the little ice age the highest values of the record ca 3 above modern 18olw values occur at ca 1900 1800 cal yr bp three negative excursions increasing in intensity toward the present at 3400 3200 1250 1100 and 350 50 cal yr bp are tentatively linked to roughly synchronous episodes of increased glacier activity and general cold spells around the northern north atlantic their manifestation in the svartvatnet 18olw record not only testify to the sensitivity and potential of high arctic lacustrine 18ochir records in tracking terrestrial climate ev

the holocene occurrence of reindeer on franz josef land russia reindeer are absent historically on the high arctic islands of franz josef land russia however shed antlers are common on unglaciated forelands on hooker scot keltie and alexandra land islands in the archipelago radiocarbon dating of 19 new antler remains combined with seven ages reported previously demonstrate the presence of reindeer between c 6400 and 1300 cal bp reindeer probably occupied franz josef land for much of the holocene reflecting sufficient forage associated with summer air temperatures 1 c warmer than today and retracted glaciers and snowfields a prominent neoglacial advance at c 1000 cal bp is coincident with inferred extinction of reindeer late twentieth century warming and associated glacier retraction may provide environmental conditions for the immigration of reindeer to franz josef land and other high arctic areas similar to earlier in the holocene

the influence of changing orbital parameters and surface boundary conditions on climate simulations for the past 18 000 years abstract general circulation model experiments at 3000 year intervals for the past 18 000 years were made to estimate the magnitude timing and pattern of the climatic response to prescribed changes of orbital parameters date of perihelion axial tilt eccentricity and glacial age lower boundary conditions ice sheets land albedo sea ice and sea surface temperature the experiments used the community climate model ccm of the national center for atmospheric research ncar the response of monsoon circulations and tropical precipitation to the orbitally produced solar radiation changes was much larger than the response to changes of glacial age boundary conditions the continental interior of eurasia was 2 4 k warmer in summer and summer monsoon precipitation of north africa south asia was increased by 10 20 between 12 000 and 6000 yr bp before present when perihelion occurred during northern summer rather than in winter as now and the earth s axial tilt was larger than now southern hemisphe

holocene paleoclimatology of the queen elizabeth islands canadian high arctic abstract a wide variety of evidence reflecting in different ways the changing climate of the queen elizabeth islands during the holocene is reviewed all proxies pertain to summer conditions many sources of information provide weak or equivocal paleoclimatic signals but a general pattern of events can be discerned temperatures in the early to mid holocene were highest comparable with or higher than temperatures prevailing for much of this century although much evidence points to a mid holocene thermal maximum there is also considerable evidence that conditions were warmer in the early holocene possibly related to orbitally induced radiation anomalies the apparent mid holocene thermal maximum may reflect lags in the response of the environment and of some proxies in recording paleoclimatic conditions more direct indices point to warmest conditions in the early holocene before 7500 bp temperatures declined from 3000 bp culminating in exceptionally low temperatures from 100 400 bp this may have been the coldest period of the entire holocene resulting in glacier advances to post glacial maximum positions the period since 1925 has witnessed a pronounced increase in temperature leading to negative mass balances on glaciers and ice sheets throughout the archipelago this period is the warmest for at least 1000 years and perhaps for several thousand years modern climate in the queen elizabeth islands may thus be characteristic of the early to mid holocene and atypical of conditions which prevailed for much of the last few thousand years

research paperreprint of reconstruction of inflow of atlantic water to isfjorden svalbard during the holocene correlation to climate and seasonality the distribution patterns of benthic foraminifera faunas stable isotopes and ice rafted debris ird have been studied in piston core jm98 845 pc from isfjorden western svalbard to reconstruct changes in the flow of atlantic water during the holocene interglacial the paleoenvironmental conditions in isfjorden and the inflow of the atlantic water followed closely the changes in insolation with strong seasonality in the early holocene and weaker seasonality in the middle to late holocene a summer temperature maximum of the bottom water occurred in the early holocene 10 500 c 8200 years bp cooling began at 9000 years bp with stepwise coolings at c 8200 7400 and 4000 years bp the cooling correlated with an increase in ice rafting and increased influence of polar water and seasonal sea ice cover between 4000 and 2000 years bp bottom water temperatures reached a minimum after 2000 years bp episodic inflow of warmer atlantic water at the bottom of the fjord occurred and conditions became more unstable the data indicate close interaction of the flow of atlantic water with the development of the terrestrial climate and the amount of polar meltwater and sea ice

archaeological silence and ecorefuges arid events in the puna of atacama during the middle holocene this paper briefly summarizes presearch concerning the mid holocene in the western slope of the puna de atacama 20 25 s proxy data and dates from palynological limnological geomorphological archives were compared with data recovered from the archaeological sites in high altitude basins intermediate ravines and piemontane paleowetlands due to exceptionally favorable conditions numerous early holocene archaeological sites were found in contrast the lack of occupations in previously populated areas suggests a decline in human activity during the arid mid holocene in this context two key concepts are introduced ecorefuge or ecological refuge and archaeological silence silencio arqueologico the first refers to the particular favorable locations occupied by human groups during the mid holocene the second provides a better understanding about the impact of the arid interval during this period on human adaptations in the most barren territories of the new world

late weichselian and holocene sedimentary environments and ice rafting in isfjorden spitsbergen abstract multi proxy analyses of two sediment cores from central isfjorden were used to reconstruct the glacial history in central spitsbergen during the late weichselian and the holocene and to relate iceberg rafting and sea ice rafting to climatic and oceanographic changes in the north atlantic region a basal till was deposited beneath an ice stream prior to 12 700 cal years bp calendar years before the present several tidewater glaciers influenced the sedimentary environment during the younger dryas and probably already during the allerod the younger dryas cooling might be reflected by enhanced sea ice formation and suspension settling as well as reduced iceberg rafting the final deglaciation was dominated by intense iceberg rafting it terminated around 11 200 cal years bp optimum holocene climatic and oceanographic conditions with significantly reduced ice rafting occurred between c 11 200 and 9000 cal years bp ice rafting occurred almost exclusively from icebergs after 10 200 cal years bp the icebergs most probably originated from tidewater glaciers on east spitsbergen indicating the presence of a strong east west temperature gradient at this time an increase of iceberg rafting around 9000 cal years bp followed by enhanced sea ice rafting reflects the onset of a general cooling in the western barents sea svalbard region comparatively intense rafting from icebergs and sea ice between 9000 and 4000 cal years bp is related to this cooling a general reduction in ice rafting after 4000 cal years bp is most probably the result of the enhanced formation of shore fast and or more permanent sea ice cover reducing the drift of icebergs and sea ice in the fjord the results indicate that the palaeoenvironmental conditions on central spitsbergen to a large degree depended on the oceanographic conditions in the western barents sea and west off spitsbergen however climatic trends affecting greenland and the entire north atlantic region can also be identified

the recession of the inland ice margin during the holocene climatic optimum in the jakobshavn isfjord area of west greenland recent subsurface mapping of parts of the greenland inland ice margin in the region of jakobshavn isbrae indicates that the fjord system in the period of at least 2700 4700 calendar yr b p was more ice free than at present and that the front of the glacier was at least 15 km behind the present position the 14c datings of subfossils brought to the present ice margin fit with the climatic records from ice cores and confirm the favourable conditions for greenland s first settlers the sarqaq people who arrived in the region about 4000 yr ago to find hunting grounds 10 20 larger than the present

time slice reconstructions of ocean circulation changes on the continental shelf in the nordic and barents seas during the last 16 000 cal yr b p abstract ocean circulation changes along the continental shelf of the nordic and barents seas have been investigated in order to reconstruct regional changes in the inflow of atlantic water aw through the last 16 000 calibrated cal years yr b p we have selected five time slices representing the late glacial 16 000 15 000 cal yr b p the bolling allerod warm interstadials 14 500 13 500 cal yr b p the younger dryas cold stadial 12 500 11 500 cal yr b p the early holocene 9500 7500 cal yr b p and the late holocene 4000 2000 cal yr b p twelve previously published records of the distribution of benthic foraminifera faunas and ice rafted debris have been compiled the earliest sign of atlantic water inflow was recorded at the northern iceland shelf at 16 000 15 000 cal yr b p the inflow of warm aw to the nordic seas shelf has been persistent since but with variable strength and geographic pattern an apparent zonal seesaw pattern in the strength of the norwegian atlantic current nwac and the irminger current ic during the late glacial bolling allerod and younger dryas periods was found during the holocene no zonal differences in the inflows of nwac and ic were found a strong meridional gradient with warmer conditions at lower latitudes and relatively cold conditions at high northern latitudes existed

debris flow recurrence periods and multi temporal observations of colluvial fan evolution in central spitsbergen svalbard abstract fan shaped accumulations of debris flow deposits are common landforms in polar regions such as svalbard although depositional processes in these environments are of high interest to climate as well as mars analog research several parameters e g debris flow recurrence periods remain poorly constrained here we present an investigation based on remote sensing as well as in situ data of a 0 4 km2 large colluvial fan in hanaskogdalen central spitsbergen we analyzed high resolution satellite and aerial images covering five decades from 1961 to 2014 and correlated them with lichenometric dating as well as meteorological data image analyses and lichenometry deliver consistent results and show that the recurrence period of large debris flows 400 m3 is about 5 to 10 years with smaller flows averaging at two per year in the period from 2008 to 2013 while this is up to two orders of magnitude shorter than previous estimates for svalbard 80 to 500 years we found the average volume of 220 m3 per individual flow to be similar to previous estimates for the region image data also reveal that an avulsion took place between 1961 and 1976 when the active part of the fan moved from its eastern to its western portion a case study of the effects of a light rain event 5 mm day in the rainy summer of 2013 which triggered a large debris flow further shows that even light precipitation can trigger major flows this is made possible by multiple light rain events or gradual snow melt pre saturating the permafrost ground and has to be taken into account when predicting the likelihood of potentially hazardous mass wasting in polar regions furthermore our findings imply a current net deposition rate on the colluvial fan of 480 m3 year which is slightly less than the integrated net deposition rate of 576 to 720 m3 year resulting from the current fan volume divided by the 12 500 to 10 000 years since the onset of fan build up after the area s deglaciation however the actual deposition rate which should increase in a warmer climate including more rain cannot be constrained due to effects like ongoing toe cutting of the debris fan and some flows only causing internal redistributions

the island of amsterdamoya a key site for studying past climate in the arctic archipelago of svalbard abstract this paper introduces a series of articles assembled in a special issue that explore holocene climate evolution as recorded in lakes on the island of amsterdamoya on the westernmost fringe of the arctic svalbard archipelago due to its location near the interface of oceanic and atmospheric systems sourced from arctic and atlantic regions amsterdamoya is a key site for recording the terrestrial response to marine and atmospheric changes we employed multi proxy approaches on lake sediments integrating physical biogeochemical and isotopic analyses to infer past changes in temperature precipitation and glacier activity the results comprise a series of quantitative holocene length paleoclimate reconstructions that reveal different aspects of past climate change each of the four papers addresses various facets of the holocene climate history of north western svalbard including a reconstruction of the annabreen glacier based on the sedimentology of the distal glacier fed lake gjoavatnet a reconstruction of changing hydrologic conditions based on sedimentology and stratigraphy in lake hakluytvatnet reconstruction of summer temperature based on alkenone paleothermometry from lakes hakluytvatnet and hajeren and a hydrogen isotope based hydrological reconstruction from lake hakluytvatnet we also present high resolution paleomagnetic secular variation data from the same lake which document important regional magnetic field variations and demonstrate the potential for use in synchronizing holocene sedimentary records in the arctic the paleoclimate picture that emerges is one of early holocene warmth from ca 10 5 ka bp interrupted by transient cooling ca 10 8ka bp and followed by cooling that mostly manifested as two stepwise events ca 7 and 4 ka bp the past 4ka were characterized by dynamic glaciers and summer temperature fluctuations decoupled from the declining summer insolation

freshwater and atlantic water inflows to the deep northern barents and kara seas since ca 13 14 c ka foraminifera and stable isotopes foraminiferal stable isotopes and assemblages from franz victoria and st anna troughs provide a valuable record of freshwater and atlantic water flows to the northern barents and kara seas from deglaciation to present the d 18 o and d 13 c of planktonic neogloboquadrina pachyderma s and benthic elphidium excavatum were up to1 4 lower than present at ca 13 11 5 and 10 14 c ka global sea level corrected mostly reflecting substantial freshwater inputs coincident with glacial marine sediment deposition cassidulina teretis exceeded 40 of benthic foraminifera ca 13 and 10 14 c ka indicating subsurface penetrations of atlantic water the transition to postglacial marine conditions is marked by a 1 rise in foraminiferal d 18 o and a sharp fall in c teretis soon after 10 14 c ka these changes imply reduced inputs of freshwater and atlantic water subsequent isotopic and foraminiferal assemblage variations reflect changing atlantic water conditions upstream in the nordic seas and shifts between the warm fram strait and cold barents sea branches of atlantic water we hypothesize that glacial isostatically induced deepening by up to 150 m influenced atlantic water inflows to the northern barents sea during deglaciation and the holocene thus effects of isostatic recovery have to be factored into paleoceanographic reconstructions 2001 elsevier science ltd all rights reserved

denudation rates in the arctic estimated from lake sediments on spitsbergen svalbard a mean holocene denudation rate of 15 mm 1000 yr is calculated for the high arctic valley linnedalen western svalbard based on estimates of the total volume of lacustrine sediments deposited in lake linnevatnet thirty six sub bottom sediment profiles and 16 sediment cores have been used to map the postglacial sediments stored in the lake these reveal a lower marine unit overlain by lacustrine sediments the base and top of the marine sediments were radiocarbon dated to around 12 300 and 9600 yr b p respectively from isopach maps of the lacustrine unit and the total sediment thickness we calculated 0 9 10 2 km3 of holocene lacustrine sediments and 20 1 10 2 km3 of marine sediments a denudation rate of 15 mm 1000 yr is calculated from the volume of the lacustrine sediments this demonstrates that fluvial erosion does not contribute significantly to the lowering of the landscape in the present climate in contrast glacial erosion rates in nearby areas on svalbard are much higher indicating that glacial erosion by warm based valley glaciers is the most important geomorphic process in the present climate three km of tertiary sediments are postulated to have been removed from central parts of svalbard our denudation rates suggest that this could not have occurred in the present interglacial type of climate we suggest that most of that was removed either in a warmer climate or by glaciers

a multi disciplinary macrofossil study of middle weichselian sediments at kobbelgard mon denmark abstract multi proxy studies of radiocarbon and luminescence dated middle weichselian sediments and allochthonous plant and animal macrofossils from kobbelgaard mon point to a lacustrine environment with shallow mesotrophic fresh water the lake was surrounded by mires rich in mosses and carex while the vegetation on the uplands was tree less and herb dominated but with scattered shrubs the climate was considerably colder than at the present day with average july temperatures around 11 c about 6 c below those for the region today probably normal for the later part of the middle weichselian the sediments contain the first remains of lemmings dicrostonyx torquatus and lemmus lemmus found in denmark

holocene millennial scale summer temperature variability inferred from sediment parameters in a non glacial mountain lake danntjorn jotunheimen central southern norway holocene changes in summer temperature in the jotunheimen area have been inferred from variations in several sediment parameters from a composite combined from two overlapping sediment cores lake core record mean time resolution of 15 years from lake danntjorn a small mountain lake located close to the modern pine tree limit in jotunheimen central southern norway loss on ignition analysis at contiguous 0 5 cm intervals throughout the cores revealed that the variations in residue after ignition of the sediments at 5501c in the upper 260 cm 8500 calendar years were not associated with variations in magnetic susceptibility in the basal deglacial and early holocene sequence of the lake sediments however the two sediment parameters fluctuated mainly in phase in addition the biogenic silica bsi concentration is relatively high thus in the early part of the holocene the variations in the residue were probably primarily driven by input of minerogenic detrital material inwash and or windblown and biological productivity including bsi from diatoms in the lake itself and in the lake surroundings from approximately 8500 calendar years bp variations in the residue probably primarily reflect variations in low minerogenic low magnetic susceptibility with little variations and diatom bsi productivity as demonstrated with analysis of bsi concentration between 260 and 233 cm 8500 7760 calendar years bp the highest residue values probably mainly reflecting high diatom productivity occurred at 7800 7200 7000 6700 6200 5400 5050 4300 2500 1800 1550 900 700 and o100 calendar years bp the most significant o8000 calendar years bp residue minima mainly low diatom productivity were recorded at 7100 6800 6600 6000 5700 5000 4400 4200 3800 3600 3200 3000 2750 2300 1900 1700 1070 740 600 380 and 80 calendar years bp bp ad 2000 the lake record from jotunheimen is discussed in the context of holocene terrestrial and marine records from the north atlantic region and possible natural climate forcing factors r 2004 elsevier ltd all rights reserved

last glacial maximum environmental conditions at andoya northern norway evidence for a northern ice edge ecological hotspot abstract andoya on the nw coast of norway is a key site for understanding the last glacial maximum lgm in northern europe controversy has arisen concerning the local conditions especially about the timing and extent of local glacial cover maximum july temperatures and whether pine and or spruce could have grown there we reviewed all existing data and add newly analysed ancient sedimentary dna sedadna pollen macrofossils geochemistry and stable isotopes from three lake sediment cores from ovre aerasvatnet a total of 23 new dates and age depth modelling suggests the lake has been ice free since gi2 14 7 cal ka bp data recorded 94 vascular plant taxa of which 38 have a northern limit in shrub tundra or more southern vegetation zones this unusual assemblage likely stems from a combination of proximity to ice free water in summer geographical isolation linked with stochastic long distance dispersal events and the presence of bird fertilized habitats the environmental reconstruction based on all records from the area does not preclude local growth of tree species as the local climate combined with high nutrient input may have led to periodically suitable environmental hotspot conditions

late quaternary hydrological and ecological changes in the hyperarid core of the northern atacama desert 21 s abstract the hyperarid core of the atacama desert possesses important reserves of fossil or ancient groundwater yet the extent and timing of past hydrologic change during the late quaternary is largely unknown in situ and or short distance transported leaf litter deposits abound along relict fluvial terraces inserted within four dry and unvegetated valleys that drain into the endorheic basin of pampa del tamarugal pdt 21 s 900 1000 m one of the largest and economically important aquifers in northern chile our exceptional archive offers the opportunity to evaluate the response of low elevation desert ecological and hydrological systems to late quaternary climate variability three repeated expansions of riparian wetland ecosystems and perennial rivers occurred along the southernmost pdt basin between 17 6 14 2 ka 12 1 11 4 ka and from 1 01 0 71 ka both early and late archaic archaeological artefact are present in clear association with our fossil riparian wetland assemblages which suggests that these palaeoenvironmental changes facilitated past human occupations in the hyperarid core of the atacama desert using modern analogues we estimate that these ecological and hydrological changes were triggered by a threefold increase in rainfall along the headwaters of what are presently inactive canyons comparisons with other regional palaeoclimatic records from the central andes indicate that these changes were synchronous with the widespread pluvial stages now termed the central andean pluvial event cape 17 5 14 2 ka and 13 8 9 7 ka in addition we summarize new evidence for perennial runoff riparian ecosystems and a major human settlement during the latest holocene our findings clearly show that local hydrological changes in the pdt were coupled with precipitation variability in the adjacent eastern highlands during the late quaternary the long term dynamics of low elevation desert ecological and hydrological systems are likely driven by changes in moisture sources with one source tied to the amazon region n ne mode and the other to the gran chaco region se mode we conclude by linking enso like variability and moisture variations over the gran chaco to the three major regional scale recharge events over the last 18 ka in the pdt basin we conclude by asserting that an important portion of the groundwater resources in the pdt is indeed fossil inherited from past pluvial events we recommend that the relationship between ancient recharge together with palaeoclimate records of past headwater rainfall fluctuations should be incorporated into future water balance models and evaluation of groundwater potential in northern chile

the holocene thermal maximum around svalbard arctic north atlantic molluscs show early and exceptional warmth shallow marine molluscs that are today extinct close to svalbard because of the cold climate are found in deposits there dating to the early holocene the most warmth demanding species found zirfaea crispata currently has a northern limit 1000 km farther south indicating that august temperatures on svalbard were 6 c warmer at around 10 2 9 2 cal ka bp when this species lived there the blue mussel mytilus edulis returned to svalbard in 2004 following recent warming and after almost 4000 years of absence excluding a short re appearance during the medieval warm period 900 years ago mytilus first arrived in svalbard at 11 cal ka bp indicating that the climate was then as least as warm as present this first warm period lasted from 11 to 9 cal ka bp and was followed by a period of lower temperatures 9 8 2 cal ka bp after 8 2 cal ka the climate around svalbard warmed again and although it did not reach the same peak in temperatures as prior to 9 ka it was nevertheless some 4 c warmer than

holocene paleoceanography and glacial history of the west spitsbergen area euro arctic margin two sediment cores from the west spitsbergen area euro arctic margin md99 2304 and md99 2305 have been investigated for paleoceanographic proxies including benthic and planktonic foraminifera benthic foraminiferal stable isotopes and ice rafted debris core md99 2304 is located on the upper continental margin reflecting variations in the influx of atlantic water in the west spitsbergen current core md99 2305 is located in van mijenfjord picturing variations in tidewater glacier activity as well as fjordocean circulation changes surface water warmer than today was present on the margin as soon as the van mijenfjord was deglaciated by 11 200 cal years bp relatively warm water invaded the fjord bottom almost immediately after the deglaciation a relatively warm early holocene was followedby an abrupt cooling at 8800 cal years bp on the continental margin another cooling in the fjord record 8000 4000 cal years bp is documented by an increase in ice rafted debris and an increase in benthic foraminiferal d 18 o the ird record indicates that central spitsbergen never was completely deglaciated during the holocene relatively cool andstable cond itions similar to the present were establishedabout 4000 cal years bp

ams radiocarbon dating of organic poor lake sediment an example from linnevatnet spitsbergen svalbard ams radiocarbon dating of specific organic fractions is used to evaluate sources of errors in dating of organic poor lake sediment from linnevatnet a proglacial arctic lake dates on un differentiated bulk organic matter are much too old because of contamination from detrital coal attempts to remove coal from other organic matter were only partially successful a consequence of the wide grain size distribution of the coal even if coal contamination is fully removed the bulk of the remaining organic matter is of aquatic origin and is unsuitable for 14c dating because the lake waters are depleted in 14 c due to dissolution of carbonate minerals terrestrial plant macrofossils provide the only reliable material to date the lake sediment however this material is present in sufficient quantity for ams radiocarbon dating only in cores proximal to the main inlet streams paired dates on terrestrial plants and aquatic insects from the same core level and paired dates on modern aquatic and terrestrial vege

model characterization of the south american low level flow during the 1997 1998 spring summer season a relevant feature of the south american low level circulation during the wet season is a poleward warm and moist current immediately to the east of the andes often referred to as a low level jet because of its resemblance to the great plains low level jet provided that the lack of observational data causes a great deal of uncertainty on the ability of analyses to describe diurnal fluctuations of sub synoptic features like a low level jet this description has been carried out using the eta regional model special emphasis has been given to the detection and characterization of a low level jet llj east of the andes as a feature best developed at night and mesoscale cross stream dimensions this study describes the modeled northerly current east of the andes during the 1997 1998 warm season and progress on its mean characterization including diurnal fluctuations and horizontal and vertical structure from moisture budget calculations a net convergence of moisture flux is found over an area that includes the del plata basin with a maximum southward flux through the northern boundary at low levels while there are evidences to suggest that this model provides a realistic description of the local circulation it is emphasized that observational data are needed to gain further understanding of the behavior of the south american low level jet and its role upon the regional climate

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

lake highstands on the altiplano tropical andes contemporaneous with heinrich 1 and the younger dryas new insights from 14 c u th dating and δ 18 o of carbonates this study provides new geochronological and stable isotope constraints on late pleistocene fluctuations in lake level that occurred in the closed watershed of the central altiplano between 25 and 12 ka u series isochrons and 14 c ages from carbonates are used to confirm and refine the previous chronology published placzek et al 2006b our new data support three successive lake highstands during the late pleistocene i the lake sajsi cycle from 25 to 19 ka that culminated at 3670 m at about 22 ka almost synchronously with the global last glacial maximum ii the lake tauca cycle that lasted from 18 to 14 5 ka and was characterized by the highest water level reached at least 3770 m from 16 5 to 15 ka iii the lake coipasa cycle from 12 5 to 11 9 ka that reached an elevation of 3700 m 42 m above the elevation of the salar de uyuni 3658 m these high amplitude lake level fluctuations are in phase with the cold warm oscillations that occurred in the north atlantic and greenland during the late pleistocene heinrich 1 bolling allerod younger dryas such temporal coincidence supports the hypothesis that wet events recorded in the central altiplano are controlled by the northesouth displacement of the inter tropical convergence zone resulting from changes in the meridional temperature gradient finally the oxygen isotope ratios measured in these lacustrine carbonates allows for calculation of the 18 o value of paleolake waters estimates of water 18 o v smow are 2 8 0 7 for lake tauca and 1 6 0 9 for lake coipasa these data are used to constrain changes in lake hydrology and can be interpreted to indicate that the proportion of precipitation arising from local water recycling was less than 50

stratigraphic expressions of the holocene anthropocene transition revealed in sediments from remote lakes stratigraphic boundaries are ideally defined by distinct lithological geochemical and palaeobiological signatures to which a chronological framework can be applied we present a range of observations that illustrate how the holocene anthropocene transition meets these criteria in its expression in sediments from remote arctic and alpine lakes removed from direct catchment scale anthropogenic influences in glaciated lake basins the retreat of glaciers commonly leads to lithological successions from proglacial clastic sedimentation to non glacial organic deposition sediments from the majority of lakes record marked depletions in the nitrogen stable isotopic composition of sediment organic matter reflecting anthropogenic influences on the global nitrogen cycle in all cases siliceous microfossil assemblages diatoms and chrysophytes change markedly and directionally with regional nuances these stratigraphic fingerprints begin to appear in the sediment record after ad 1850 but accelerate in pulses between ad 1950 and 1970 and again after ad 1980 our review indicates that recent environmental changes associated with humankind s dominance of key global biogeochemical cycles are sufficiently pervasive to be imprinted on the sediment record of remote lakes moreover these changes are of sufficient magnitude to conclude that the holocene has effectively ended and that the concept of anthropocene more aptly describes current planetary dynamics the synthesis of these observations pertains directly to ongoing discussions concerning the eventual formalization of a new stratigraphic boundary

holocene multi proxy environmental reconstruction from lake hakluytvatnet amsterdamoya island svalbard 79 5 n high resolution proxy records of past climate are sparse in the arctic due to low organic production that restricts the use of radiocarbon dating and challenging logistics that make data collection difficult here we present a new lake record from lake hakluytvatnet at amsterdamoya island 79 5 n the northwesternmost island on svalbard multi proxy analyses of lake sediments in combination with geomorphological mapping reveal large environmental shifts that have taken place at amsterdamoya during the holocene a robust chronology has been established for the lake sediment core through 28 ams radiocarbon ages and this gives an exceptionally well constrained age control for a lake at this latitude the holocene was a period with large changes in the hakluytvatnet catchment and the onset of the neoglacial ca 5 ka marks the start of modern day conditions in the catchment the neoglacial is characterized by fluctuations in the minerogenic input to the lake as well as internal productivity and we suggest that these fluctuations are driven by atmospherically forced precipitation changes as well as sea ice extent modulating the amount of moisture that can reach hakluytvatnet

stratified interglacial lacustrine sediments from baffin island arctic canada chronology and paleoenvironmental implications abstract thirteen of 18 piston cores recovered from robinson lake in the mid arctic vegetation zone of baffin island arctic canada penetrated stratified lacustrine sediment beneath a thin over consolidated diamict till and postglacial lacustrine sediment the sub till lacustrine units are up to 120 cm thick of which the upper several decimeters frequently contain thick layered mats of aquatic moss pollen and diatoms are common throughout both lacustrine units a series of 23 ams 14c dates defines the chronology of the postglacial sequence which records a succession from a pioneer grass and oxyria dominated tundra between 10 4 and 8 ka bp to a sedge dominated tundra after 8 ka bp limiting 14c dates place the sub till lacustrine sediments more than 40 ka bp 10 luminescence dates centered on 85 ka indicate they were deposited late in oxygen isotope stage ois 5 the dominance of shrub and tree pollen especially shrub birch and alder in sub till lacustrine samples indicates low arctic tundra farther north than at any time during the holocene pollen concentrations are comparable to or higher than in the holocene units cooling late in the interglacial is indicated by declining birch and alder pollen percentages in the upper part of the section diatom floras in both the sub till and postglacial lacustrine sequences indicate similar development of lake water chemistry but input of silica and weathering products was greater in the older lake cycle suggesting more vigorous catchment processes macrofossils in the sub till units are characteristic of lakes ice free in summer based on pollen assemblages indicating local and regional vegetation diagnostic of summer temperatures higher than the holocene we interpret the sub till lacustrine units to be of interglacial character by analogy with holocene plant succession in central and eastern canada all of keewatin and labrador ungava must have been ice free throughout this interval suggesting essentially complete deglaciation of the laurentide ice sheet at the time

high latitude holocene paleosecular variation and magneto stratigraphic correlation between two lakes on spitsbergen 78 n abstract paleomagnetic signals in cores from two nearby lakes linnevatn and skardtjonn on spitsbergen 78 n record high latitude geomagnetic field variations for the last 10000 years although the paleomagnetic signal in the lake linnevatn core has probably been modified by subsampling effects application of a latitude invariant transformation procedure yields logs with directional amplitudes similar to the transformed holocene paleosecular variation master curve from the uk stratigraphic correlations based on pattern recognition suggest maximum ages of the lacustrine sediments in agreement with 14c age determinations age depth curves based on more than six magnetic datum horizons from each core reveal an abrupt increase in sedimentation rate in linnevatn from about 0 4 mm year 1 to about 0 8 mm year 1 around 2500 b p vertical inclinations in both cores between about 3500 and 6000 b p are interpreted to reflect a stationary magnetic pole in the region of the sampling sites this adds further arguments for the proposed sudden dipole shift recognized around 3500 b p in paleomagnetic records from high latitude 63 n lacustrine sediments in alaska

flora fauna and climate of scotland during the weichselian middle pleniglacial palynological macrofossil and coleopteran investigations thin lenses of organic rich material on the upper surface of a layer of glacio fluvial deposits have been studied in an open cast coal mine near sourlie western scotland radiocarbon dates on antler fragments plant debris and bulk organic matter from silt showed that the sediments accumulated between ca 33 500 and 29 000 14c yr bp during a period when this part of western scotland was free of glaciers the organic rich sediments yielded a very rich flora and fauna and in total about 160 plant taxa and 61 coleopteran taxa were recorded together with other invertebrates the sourlie flora is one of the richest late middle weichselian floras yet studied within the british isles leg bones of coelodonta antiquitatis woolly rhinoceros and rangifer tarandus reindeer were also found at the site during this period the landscape was treeless and the vegetation could be characterised as an intermediate between a low shrub tundra and sedge grass moss tundra both the flora and arthropod fauna suggest that during formation of the organic rich layers at sourlie mean july temperatures were 9 10 c the flora suggests also that at the beginning of formation of these layers minimum mean july temperatures increased from 7 to 9 10 c but later dropped again to 7 8 c a possible time correlation with one of the warmer periods of the dansgaard oeschger cycles in the stable oxygen isotope record of the greenland ice cores during this period is proposed the arthropod fauna suggests that mean january temperatures were somewhere between 34 and 11 c mean annual temperatures lay probably between 1 and 10 c which implies the possible presence of discontinuous or continuous permafrost in the area during winter a protective snow cover of varying thickness probably enabled perennial plants especially shrubs to survive

late pleistocene paleohydrology near the boundary of the sonoran and chihuahuan deserts southeastern arizona usa abstract ground water discharge gwd deposits form in arid environments as water tables rise and approach or breach the ground surface during periods of enhanced effective precipitation where preserved these deposits contain information on the timing and elevation of past ground water fluctuations here we report on the investigation of a series of gwd deposits that are exposed in discontinuous outcrops along a 150 km stretch of the san pedro valley in southeastern arizona near the boundary of the sonoran and chihuahuan deserts chronologic isotopic geochemical faunal assemblage ostracodes and gastropods and sedimentological evidence collectively suggest that the elevation of the regional water table in the valley rose in response to a change in climate 50 ka ago and remained relatively high for the next 35 ka before falling during the bolling allerod warm period rebounding briefly during the younger dryas cold event and falling again at the onset of the holocene the timing of these hydrologic changes coincides closely with variations in 18o values of calcite from a nearby speleothem to the west and changes in lake levels at pluvial lake cochise to the east thus in southeastern arizona the assumption that changes in climate are reflected in all aspects of the hydrologic cycle of a region simultaneously is validated the timing of these changes also broadly coincides with variations in the gisp2 18o record which supports the hypothesis that atmospheric teleconnections existed between the north atlantic and the deserts of the american southwest during the late pleistocene

holocene glacial history of svalbard status perspectives and challenges abstract we synthesize the current understanding of glacier activity on svalbard from the end of the late pleistocene 12 000 yrs before present to the end of the little ice age c 1920 ad our glacier history is derived from the svalhola database the first compilation of holocene geochronology for svalbard and the surrounding waters including over 1 800 radiocarbon terrestrial cosmogenic nuclide and optically stimulated luminescence ages data have been categorized by geological setting uniformly re calibrated quality assessed and ultimately used to constrain glacier fluctuations deglaciation ice free conditions glacier re advances and ice marginal positions we advance existing knowledge by mapping the extent and distribution of ice cover during the holocene glacial maximum and the glacial minimum as well as present retreat rates and percentages within early holocene fjord systems throughout the holocene svalbard glaciers have responded to a varying combination of climatic environmental and dynamic driving factors which influence both the extent and behavior of ice margins we discuss the complexities of glacier systems and their dynamics in response to changes in climate this review provides a holistic state of the art of holocene glaciers on svalbard suitable for orienting future works which address gaps in our current knowledge

alkenone based reconstructions reveal four phase holocene temperature evolution for high arctic svalbard abstract situated at the crossroads of major oceanic and atmospheric circulation patterns the arctic is a key component of earth s climate system compounded by sea ice feedbacks even modest shifts in the region s heat budget drive large climate responses this is highlighted by the observed amplified response of the arctic to global warming assessing the imprint and signature of underlying forcing mechanisms require paleoclimate records allowing us to expand our knowledge beyond the short instrumental period and contextualize ongoing warming however such datasets are scarce and sparse in the arctic limiting our ability to address these issues here we present two quantitative holocene length paleotemperature records from the high arctic svalbard archipelago situated in the climatically sensitive arctic north atlantic temperature estimates are based on u 37 k unsaturation ratios from sediment cores of two lakes our data reveal a dynamic holocene temperature evolution with reconstructed summer lake water temperatures spanning a range of 6 8 c and characterized by four phases the early holocene was marked by an early onset 10 5 ka cal bp of insolation driven hypsithermal conditions likely compounded by strengthening oceanic heat transport this warm interval was interrupted by cooling between 10 5 8 3 ka cal bp that we attribute to cooling effects from the melting northern hemisphere ice sheets temperatures declined throughout the middle holocene following a gradual trend that was accentuated by two cooling steps between 7 8 7 ka cal bp and around 4 4 4 3 ka cal bp these transitions coincide with a strengthening influence of arctic water and sea ice in the adjacent fram strait during the late holocene past 4 ka temperature change decoupled from the still declining insolation and fluctuated around comparatively cold mean conditions by showing that holocene svalbard temperatures were governed by an alternation of forcings this study improves our understanding of arctic climate dynamics

hydroclimate variability of high arctic svalbard during the holocene inferred from hydrogen isotopes of leaf waxes abstract the response of the arctic hydrologic cycle to global warming includes changes in precipitation patterns and moisture availability associated with variable sea ice extent and modes of atmospheric circulation reconstructions of past hydroclimate changes help constrain the natural range of these systems identify the manners in which they respond to different forcing mechanisms and reveal their connections to other components of the climate system all of which lead to a better understanding of present and future changes here we examine hydroclimate changes during the holocene in the high arctic archipelago of svalbard by reconstructing the isotopic composition of precipitation we measured the hydrogen isotopic composition d values of leaf wax compounds n alkanes c 25 c 31 in a sediment core from lake hakluytvatnet on the island of amsterdamoya northwest spitsbergen we interpret d values of mid chain c 25 and long chain c 29 c 31 length n alkanes to represent changes in the isotopic composition of lake water and precipitation over the last 12 9 ka after deglaciation of the catchment water supply became restricted and the lake experienced significant evaporative isotopic enrichment indicating warmer conditions from 12 8 to 7 5 ka the isotope values suggest an increase in the delivery of moisture from warmer sub polar air masses between 12 8 and 9 5 ka followed by generally warm but unstable conditions between 9 5 and 7 5 ka possibly indicating a response to meltwater forcing sedimentary evidence indicates a hiatus in deposition c 7 5 5 0 ka likely as a result of desiccation of the lake at c 5 0 ka lacustrine sedimentation resumed and over the last 5 ka there was a progressive increase in the influence of polar air masses and colder conditions which culminated in an abrupt shift to colder conditions at c 1 8 ka this late holocene cooling ended c 0 18 ka when isotopic data indicate warmer conditions and greater influence of moisture derived from lower latitudes

paleoclimatic inferences from glacial fluctuations on svalbard during the last 20 000 years the climate history of western spitsbergen svalbard is deduced from variations of glaciers during the last 20 000 years a major depression of the regional equilibrium line altitude ela occurred during the late weichselian glacial maximum 18000 13000y ago when low summer temperatures may have caused year round snow accumulation on the ground this rapid expansion of the glaciers also indicates nearby moisture sources suggesting partly open conditions in the norwegian sea during the summers a rapid glacial retreat around 13 000 12 500 y bp was caused by a sudden warming during the younger dryas the ela along the extreme western coast of spitsbergen was not significantly lower than at present in contrast to fennoscandia the british isles and the alps there is no evidence for readvance of local glaciers during younger dryas on western spitsbergen this difference is attributed to a much dryer climate on spitsbergen and probably only slight changes in sea surface temperatures in addition summer melting in this high arctic area is more sensitive to orbitally increased insolation around 10 000 y bp another rapid warming occurred and during early and mid holocene the summer temperatures were significantly higher than at present a temperature decline during the late holocene caused regrowth of the glaciers which reached their maximum holocene position during the last century

holocene cooling culminates in sea ice oscillations in fram strait a reconstruction of holocene sea ice conditions in the fram strait provides insight into the palaeoenvironmental and palaeoceanographic development of this climate sensitive area during the past 8500 years bp organic geochemical analyses of sediment cores from eastern and western fram strait enable the identification of variations in the ice coverage that can be linked to changes in the oceanic and atmospheric circulation system by means of the sea ice proxy ip25 phytoplankton derived biomarkers and ice rafted detritus ird increasing sea ice occurrences are traced along the western continental margin of spitsbergen throughout the holocene which supports previous palaeoenvironmental reconstructions that document a general cooling a further significant ice advance during the neoglacial is accompanied by distinct sea ice fluctuations which point to short term perturbations in either the atlantic water advection or arctic water outflow at this site at the continental shelf of east greenland the general holocene cooling however seems to be less pronounced and sea ice conditions remained rather stable here a major neoglacial increase in sea ice coverage did not occur before 1000 years bp phytoplankton ip25 indices pip25 index are used for more explicit sea ice estimates and display a mid holocene shift from a minor sea ice coverage to stable ice margin conditions in eastern fram strait while the inner east greenland shelf experienced less severe to marginal sea ice occurrences throughout the entire holocene highlights biomarker and ird data give insight into holocene sea ice conditions in fram strait we find increasing sea ice coverage off west spitsbergen throughout the holocene oceanic atmospheric variability caused neoglacial sea ice fluctuations ice conditions along east greenland shelf remain rather stable until 1000 years bp

holocene vegetational history and climatic change in west spitsbergen plant macrofossils from skardtjorna an arctic lake macrofossil analyses of a 335 cm long core from skardtjorna a small lake on the west coast of spitsbergen svalbard are presented the known processes of deposition of plant remains to arctic lake sediments are summarised and used in the interpretation of the vegetation history at skardtjorna the basal sediment is ams dated to 8110 110 bp the rest of the profile is dated by palaeomagnetic correlation the lowest sediments have the greatest macrofossil concentration and numbers of taxa per sample the occurrences of cassiope hypnoides and salix cf glauca before 4000 bp indicate a mean july temperature for the early holocene about 2 c higher than today comparable to the cassiope tetragona vegetation zone of the mid arctic region of the inner fjords increasing climatic severity resulted in the threshold from the cassiope to the dryas vegetation zone being passed at about 2500 bp the inferred climatic history at skardtjorna is compatible with other evidence from svalbard and elsewhere in the arctic

minimizing the edge effect in environmental reconstructions by trimming the calibration set chironomid inferred temperatures from spitsbergen a core from lake skardtjorna on western spitsbergen was analysed for subfossil chironomids with the aim of inferring past temperatures the core spans the last 1760 years and has a low concentration and low diversity of chironomids three taxa dominate the record oliveridia tricornis micropsectra radialistype and m insignilobus type the latter not previously recorded on svalbard compared with the full norwegian modern climate chironomid calibration data set skardtjorna is at the coldest end of the modern temperature gradient in an attempt to decrease potential bias caused by the numerical edge effect and to improve the taxon response functions the training set was trimmed by excluding lakes dissimilar to the study site two trimming approaches are tested in the first lakes at the warm end of the gradient are excluded in the second the calibration data set lakes are partitioned by twinspan on the basis of their modern chironomid assemblages and lakes most dissimilar to skardtjorna are exclude

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 glacier variability from lake sediments reveals dynamic holocene climate in svalbard abstract the arctic is warming faster than anywhere else on earth holocene proxy time series are increasingly used to put this amplified response in perspective by understanding arctic climate processes beyond the instrumental period however available datasets are scarce unevenly distributed and often of coarse resolution glaciers are sensitive recorders of climate shifts and variations in rock flour production transfer this signal to the lacustrine sediment archives of downstream lakes here we present the first full holocene record of continuous glacier variability on svalbard from glacier fed lake hajeren this reconstruction is based on an undisturbed lake sediment core that covers the entire holocene and resolves variability on centennial scales owing to 26 dating points a toolbox of physical geochemical xrf and magnetic proxies in combination with multivariate statistics has allowed us to fingerprint glacier activity in addition to other processes affecting the sediment record evidence from variations in sediment density validated by changes in ti concentrations reveal glaciers remained present in the catchment following deglaciation prior to 11 300 cal bp culminating in a holocene maximum between 9 6 and 9 5 ka cal bp correspondence with freshwater pulses from hudson strait suggests that early holocene glacier advances were driven by the melting laurentide ice sheet lis we find that glaciers disappeared from the catchment between 7 4 and 6 7 ka cal bp following a late hypsithermal glacier reformation around 4250 cal bp marks the onset of the neoglacial supporting previous findings between 3380 and 3230 cal bp we find evidence for a previously unreported centennial scale glacier advance both events are concurrent with well documented episodes of north atlantic cooling we argue that this brief forcing created suitable conditions for glaciers to reform in the catchment against a background of gradual orbital cooling these findings highlight the climate sensitivity of the small glaciers studied which rapidly responded to climate shifts the start of prolonged neoglacial glacier activity commenced during the little ice age lia around 700 cal bp in agreement with reported advances from other glaciers on svalbard in conclusion this study proposes a three stage holocene climate history of svalbard successively driven by lis meltwater pulses episodic atlantic cooling and declining summer insolation

the southwest indian monsoon over the last 18 000 years previously published results suggest that the strength of the sw indian monsoon can vary significantly on century to millenium time scales an observation that has important implications for assessments of future climate and hydrologic change over densely populated portions of asia we present new well dated multi proxy records of past monsoon variation from three separate arabian sea sediment cores that span the last glacial maximum to late holocene to a large extent these records confirm earlier published suggestions that the monsoon strengthened in a series of abrupt events over the last deglaciation however our data provide a somewhat refined picture of when these events took place and suggest the primacy of two abrupt increases in monsoon intensity one between 13 and 12 5 ka and the other between 10 and 9 5 ka this conclusion is supported by the comparisons between our new marine data and published paleoclimatic records throughout the african asian monsoon region the comparison of data sets further supports the assertion that maximum monsoon intensity lagged peak insolation forcing by about 3000 years and extended from about 9 5 to 5 5 ka the episodes of rapid monsoon intensification coincided with major shifts in north atlantic european surface temperatures and ice sheet extent this coincidence coupled with new climate model experiments suggests that the large land sea thermal gradient needed to drive strong monsoons developed only after glacial conditions upstream of and on the tibetan plateau receded cold north atlantic sea surface temperatures european ice sheets and extensive asian snow cover it is likely that abrupt changes in seasonal soil hydrology were as important to past monsoon forcing as were abrupt snow related changes in regional albedo our analysis suggests that the monsoon responded more linearly to insolation forcing after the disappearance of glacial boundary conditions decreasing gradually after about 6 ka our data also support the possibility that significant century scale decreases in monsoon intensity took place during the early to mid holocene period of enhanced monsoon strength further highlighting the need to understand paleomonsoon dynamics before accurate assessments of future monsoon strength can be made

variations in temperature and extent of atlantic water in the northern north atlantic during the holocene we compare six high resolution holocene sediment cores along a s n transect on the norwegian svalbard continental margin from ca 601n to 77 41n northern north atlantic planktonic foraminifera in the cores were investigated to show the changes in upper surface and subsurface water mass distribution and properties including summer sea surface temperatures sst the cores are located below the axis of the norwegian current and the west spitsbergen current which today transport warm atlantic water to the arctic sediment accumulation rates are generally high at all the core sites allowing for a temporal resolution of 10 10 2 years sst is reconstructed using different types of transfer functions resulting in very similar sst trends with deviations of no more than 71 0 1 51c a transfer function based on the maximum likelihood statistical approach is found to be most relevant the reconstruction documents an abrupt change in planktonic foraminiferal faunal composition and an associated warming at the younger dryas preboreal transition the earliest part of the holocene was characterized by large temperature variability including the preboreal oscillations and the 8 2 k event in general the early holocene was characterized by ssts similar to those of today in the south and warmer than today in the north and a smaller s n temperature gradient 0 231c 1n compared to the present temperature gradient 0 461c 1n the southern proxy records 60 691n were more strongly influenced by slightly cooler subsurface water probably due to the seasonality of the orbital forcing and increased stratification due to freshening the northern records 72 77 41n display a millennial scale change associated with reduced insolation and a gradual weakening of the north atlantic thermohaline circulation thc the observed northwards amplification of the early holocene warming is comparable to the pattern of recent global warming and future climate modelling which predicts greater warming at higher latitudes the overall trend during mid and late holocene was a cooling in the north stable or weak warming in the south and a maximum s n sst gradient of ca 0 71c 1n at 5000 cal years bp superimposed on this trend were several abrupt temperature shifts four of these shifts dated to 9000 8000 5500 3000 and 1000 and 400 cal years bp appear to be global as they correlate with periods of global climate change in general there is a good correlation between the northern north atlantic temperature records and climate records from norway and svalbard r 2007 elsevier ltd all rights reserved

vegetation and climate during the weichselian early glacial and pleniglacial in the niederlausitz eastern germany macrofossil and pollen evidence cryoturbated organic beds and channel fills intercalated with sandy and gravelly fluvial units have been studied in an opencast brown coal mine near nochten niederlausitz eastern germany the fluvial aeolian sequence covers parts of the early pleni and late glacial the detailed chronology is based on 11 radiocarbon and 12 osl dates covering the period between ca 100 kyr and 11 kyr bp basal peat deposits are correlated with an early weichselian interstadial during this period boreal forests were present and minimum mean summer temperatures were 13 c early pleniglacial deposits are absent the middle and late pleniglacial environments were treeless and different types of tundra vegetation can be recognised minimum mean summer temperatures varied between 10 and 15 c vegetation and climate is reconstructed in detail for the periods around 34 38 kyr bp and 24 25 kyr bp around 34 38 ka a mixture between a low shrub tundra and a cottongrass tussock subshrub tundra was present the botanical and sedimentological data suggest that from the middle to the late pleniglacial the climate became more continental aridity and wind strength increased and the role of a protecting winter snow cover decreased a sedge grass moss tundra dominated around 24 and 25 kyr bp copyright 2001 john wiley sons ltd

ice age vegetation and climate of subtropical chile abstract vegetation and climate of subtropical chile over the past 50 000 yr are reconstructed from pollen spores and other microfossils contained in a 10 7 m section of lacustrine deposits of laguna de tagua tagua 34 30 s 71 10 w controlled by 14 radiocarbon age determinations five pollen assemblages covering stratigraphic zones in the section represent plants on the upland and species inhabiting the lake basin surface pollen spectra from 58 stations approximately 30 40 s form an adjunct for interpreting past vegetation and climate from the fossil record temperature semi humid woodland of southern beech nothofagus dombeyi type and podocarp prumnopitys andina was apparently established about laguna de tagua tagua during the pleistocene contrasting existing semi arid broad sclerophyllous vegetation the woodland was extensive about the lake at the time of the last glacial maximum 25 000 14 000 yr b p and earlier 43 000 34 000 yr b p pollen from the families chenopodiaceae and amaranthaceae which characterize intervals of the pleistocene centered around 33 000 and 43 000 yr b p and the holocene suggests intervening episodes of relative aridity lake level fluctuations appear to follow the late quaternary climatic pattern implied by pollen assemblage data water in the lake was relatively high during development of southern beech podocarp woodland whereas during intervals of chenopod amaranth dominance lake levels were comparatively low excess precipitation over evaporation which during the pleistocene favored development of woodland of beech and podocarp is attributed to greater storm frequency conditions were apparently governed by strengthening of atmospheric circulation in the belt of southern westerly winds in the late glacial the temperate and more humid ice age climate with limited seasonality underwent transition to a subtropical semi arid mediterranean type that identifies the postglacial fluctuations in intensity of the southern westerlies marked by latitudinal movement of the polar front can account for past vegetation changes at laguna de tagua tagua

evidence from north west canada for an early holocene milankovitch thermal maximum according to the milankovitch theory of global climatic change maximum summer solar radiation at high latitudes of the northern hemisphere occurred at 10 000 yr bp refs 1 2 in particular it predicts summer solstice radiation greater by 9 10 preliminary climate simulation experiments with these increased values of radiation confirm that high latitude land surfaces received maximal insolation at 10 000 yr refs 3 4 paradoxically however the large volume of fossil pollen and other evidence from north america indicates a maximum of holocene warmth at 7 000 6 000 yr ref 5 and a recent review of the evidence from new england suggests that the warming began at 9 000 and ended at 5 000 yr but also stresses the difficulties of interpretation in terms of climate change6 we summarize here data from sites in the north west corner of mainland canada fig 1 that directly support the milankovitch hypothesis

coast formation in an arctic area due to glacier surge and retreat the hornbreen hambergbreen case from spistbergen glacierized coasts undergo faster geomorphic processes than unglaciated ones we have studied changes of the coastal area in southern svalbard with the glacier bridge between torell land and sorkapp land since the beginning of the 20th century the existence of a continuous subglacial depression beneath the hornbreen hambergbreen system has been debated since the 1960s with inconclusive results in this study we assess both the subglacial topography and the bathymetry of hornsund fjord and hambergbukta bay this included 40 km of radar surveys over the glacial system and sea depth sounding the extent of the glaciers from maps and satellite images together with digital terrain models and surface elevation data based on gps profiling were used to analyse geometry changes of the glacier surfaces the results confirm the existence a continuous subglacial depression below sea level c 40 m deep between hornsund and the barents sea the hornbreen hambergbreen system has changed in shape over the past century reflecting its dynamic origin and activity also exemplified by the sequential surges identified since 1899 there was a pre surge build up event of flatbreen causing a surge and subsequent lowering of the hornbreen hambergbreen terminus by the 1960s after the entire surface lowered albeit with a delay in the hornbreen terminal zone since the year 2000 hornbreen terminus has retreated at an average rate of 106 m a 1 50 faster than that of hambergbreen if the retreat continues at the 2000 2015 average rate the ice bridge between hornsund and hambergbukta will be broken sometime between 2055 and 2065 and the hornsund strait will separate sorkapp land from the spitsbergen island the processes and events described in this study particularly the effects of the glacier surge may provide a model for changes likely to occur in other coastal glaciated regions experiencing rapid change

temperature and precipitation history of the arctic as the planet cooled from peak warmth in the early cenozoic extensive northern hemisphere ice sheets developed by 2 6 ma ago leading to changes in the circulation of both the atmosphere and oceans from not vert similar2 6 to not vert similar1 0 ma ago ice sheets came and went about every 41 ka in pace with cycles in the tilt of earth s axis but for the past 700 ka glacial cycles have been longer lasting not vert similar100 ka separated by brief warm interglaciations when sea level and ice volumes were close to present the cause of the shift from 41 ka to 100 ka glacial cycles is still debated during the penultimate interglaciation not vert similar130 to not vert similar120 ka ago solar energy in summer in the arctic was greater than at any time subsequently as a consequence arctic summers were not vert similar5 c warmer than at present and almost all glaciers melted completely except for the greenland ice sheet and even it was reduced in size substantially from its present extent with the loss of land ice sea level was about 5 m higher than present with the extra melt coming from both greenland and antarctica as well as small glaciers the last glacial maximum lgm peaked not vert similar21 ka ago when mean annual temperatures over parts of the arctic were as much as 20 c lower than at present ice recession was well underway 16 ka ago and most of the northern hemisphere ice sheets had melted by 6 ka ago solar energy reached a summer maximum 9 higher than at present not vert similar11 ka ago and has been decreasing since then primarily in response to the precession of the equinoxes the extra energy elevated early holocene summer temperatures throughout the arctic 1 3 c above 20th century averages enough to completely melt many small glaciers throughout the arctic although the greenland ice sheet was only slightly smaller than at present early holocene summer sea ice limits were substantially smaller than their 20th century average and the flow of atlantic water into the arctic ocean was substantially greater as summer solar energy decreased in the second half of the holocene glaciers re established or advanced sea ice expanded and the flow of warm atlantic water into the arctic ocean diminished late holocene cooling reached its nadir during the little ice age about 1250 1850 ad when sun blocking volcanic eruptions and perhaps other causes added to the orbital cooling allowing most arctic glaciers to reach their maximum holocene extent during the warming of the past century glaciers have receded throughout the arctic terrestrial ecosystems have advanced northward and perennial arctic ocean sea ice has diminished here we review the proxies that allow reconstruction of quaternary climates and the feedbacks that amplify climate change across the arctic we provide an overview of the evolution of climate from the hot house of the early cenozoic through its transition to the ice house of the quaternary with special emphasis on the anomalous warmth of the middle pliocene early quaternary warm times the mid pleistocene transition warm interglaciations of marine isotope stages 11 5e and 1 the stage 3 interstadial and the peak cold of the last glacial maximum

early to mid holocene aridity in central chile and the southern westerlies the laguna aculeo record 34 s abstract central chile 32 35 s lies at the northern border of strong westerly influence and thus exhibits a steep precipitation gradient therefore the palaeoclimatic archives in the region are suitable for detecting past moisture changes the study of laguna aculeo 33 50 s 70 54 w presents a multiproxy holocene lake record including sedimentology geochemistry mineralogy pollen diatoms and radiocarbon dating 17 dates results indicate an arid early to mid holocene period about 9500 5700 cal yr b p after 5700 cal yr b p effective moisture increased progressively and around 3200 cal yr b p modern humid conditions were established numerous intercalated clastic layers reflect flood deposition during rainy winters a fluvial unit was deposited shortly before 9000 cal yr b p subsequently flood events were absent until 5700 but have become frequent since 3200 cal yr b p the frequency of flood layers possibly points to weak or no el nino activity during the early and mid holocene with a subsequent increase during the late holocene during the early and mid holocene the westerlies were probably blocked and hence deflected southward by the subtropical high pressure cell higher precipitation during the last 3200 yr seems strongly related to a weakened subtropical high pressure cell with intensified westerlies and possibly increased el nino activity

mid holocene paleoenvironments in northwestern argentina main patterns and discrepancies abstract this paper summarizes the available paleoenvironmental information for the mid holocene in northwestern argentina in order to systematize a multi scale scenario for human adaptation in the area the main results of the studies carried out by several research teams that have studied the conditions during this period in the tropical andean region are described and compared taking into account their geographical setting the proxies involved and their particular space time resolution the paleoenvironmental situation prior to the onset of mid holocene conditions i e starting at the late glacial maximum is summarized to estimate the nature and extent of the changes occurred during this period paleoenvironmental results their characteristics and interpretation are also considered a general trend towards an aridization process that fostered a hydrologic stress process is traceable along the mid holocene in northwestern argentina and the tropical andes however several localities seem to have retained wetter conditions increasing the contrast between highly productive environments and the generally dry landscape this paper is only a first step towards a full understanding of the diversity and complexity of the mid holocene in different space time scales but a necessary one in order to start to model the resources structure available for human groups in the past in the andes

advection of atlantic water to the western and northern svalbard shelf since 17 500 cal yr bp abstract the changes in flow and character of the warm atlantic water through the last 17 500 cal yr are reconstructed from the distribution of benthic foraminifera species planktonic and benthic foraminifera abundances stable oxygen isotopes and lithology in two cores from the western and northern shelf of svalbard the results show almost continuous presence of atlantic water at the shelf areas since 14 500 cal yr bp the bolling and allerod intervals stand out as periods of highest bottom waters temperatures the strong inflow of saline but chilled atlantic water during the early holocene was followed by cooling and freshening of the bottom waters during the mid and late holocene the two records reveal synchronous oceanographic changes that are closely tied to changes in the flow of atlantic water recorded further south in the nordic seas the early holocene warming was not just an effect of higher solar insolation but was also due to increased heat flux from the stronger atlantic water inflow driven by wind force and or thermohaline circulation

carbonate and organic matter sedimentation and isotopic signatures in lake chungara chilean altiplano during the last 12 3 kyr abstract sediments in lakes in the andean volcanic setting are often made up of diatomaceous ooze together with volcaniclastics and small amounts of carbonates despite their scarcity carbonates along with organic matter provide significant paleoenvironmental information about lake systems this study focuses on the carbonates in lake chungara their morphologies distribution and origin deduced from the isotopic markers these markers reflected changes in the water and the biomass between the onset of the holocene and around 9 6 cal kyr bp these changes are marked by general increases in toc tn and tn 15nair and by fluctuating values of toc 13cvpdb in its sediments and are probably related to major shifts in the lake surface volume associated with rises in lake level an increase in salinity around 10 cal kyr bp is thought to be linked to a short dry period giving rise to the onset of carbonate production the mid holocene arid period between 7 3 and 3 5 cal ka bp with a maximum of aridity around 6 0 cal kyr bp was deduced from 18ovpdb values in the endogenic carbonates these results match the reconstructions in lake titicaca based on benthic diatoms and paleoshore levels offshore sediments mainly consist of a diatomaceous ooze laminated in the lower half unit 1 and banded massive with tephra layers in the upper half of the sequence unit 2 toc 13cvpdb and the c n ratio confirm that phytoplankton was the main source of organic matter in these sediments shallower sediments units 3 to 5 developed in platform and littoral settings providing evidence of subaqueous macrophytes and to a lesser extent land plants carbonate content ranges between 0 1 and 6 wt in offshore settings 30 to 40 m water depth and reaches the maximum values in the lower part of unit 2 carbonate minerals low magnesium calcite and minor amounts of high magnesium calcite and aragonite are scarce and are arranged in mm thick layers commonly forming cm thick levels or bioclasts carbonate layers are made up of euhedral to subhedral spindle shaped calcite crystals and to a lesser extent aragonite needles all in the m range aragonite spheroids coexist in littoral sediments with other carbonate shapes and charophyte remains where carbonate reaches locally up to 20 wt co2 photosynthetic depletions related to seasonal phytoplankton blooms were responsible for the high frequency deposition of mm thick carbonate layers the average values for 13cvpdb in lake water plankton and sediments of lake chungara as organic matter or as carbonate are around 15 higher than commonly reported values in other lakes this 13c enrichment is attributed to carbon assimilation from a dic affected by methanogenesis in which hco3 is the dominant species the 13cvpdb and 18ovpdb variations and their covariation in endogenic carbonates suggest that lake water volume and lake level increased along the holocene

reconstruction of inflow of atlantic water to isfjorden svalbard during the holocene correlation to climate and seasonality abstract the distribution patterns of benthic foraminifera faunas stable isotopes and ice rafted debris ird have been studied in piston core jm98 845 pc from isfjorden western svalbard to reconstruct changes in the flow of atlantic water during the holocene interglacial the paleoenvironmental conditions in isfjorden and the inflow of the atlantic water followed closely the changes in insolation with strong seasonality in the early holocene and weaker seasonality in the middle to late holocene a summer temperature maximum of the bottom water occurred in the early holocene 10 500 c 8200 years bp cooling began at 9000 years bp with stepwise coolings at c 8200 7400 and 4000 years bp the cooling correlated with an increase in ice rafting and increased influence of polar water and seasonal sea ice cover between 4000 and 2000 years bp bottom water temperatures reached a minimum after 2000 years bp episodic inflow of warmer atlantic water at the bottom of the fjord occurred and conditions became more unstable the data indicate close interaction of the flow of atlantic water with the development of the terrestrial climate and the amount of polar meltwater and sea ice

from proxy data to paleoclimate interpretation the mid holocene paradox of the atacama desert northern chile abstract the question whether the mid holocene climate between ca 9 and 4 cal kyr b p in the atacama desert and the central andes in general was humid or dry has wide implications with regard to the understanding of long term climate variability in south america paleosols regional groundwater tables abiotic proxy data and pollen of aquatic plants in lake sediments show a marked and rapid shift from very humid late glacial early holocene climatic conditions between ca 14 and 9 5 kyr b p to extremely dry mid holocene conditions more arid than today between ca 9 and 4 kyr b p an exception during this hyperarid period is a century scale more humid interval around ca 5 5 6 kyr b p that appears systematically in lake sediment archives in contrast pollen for most terrestrial plants preserved in lake sediments do not show major changes during the holocene whereas more humid mid holocene conditions compared with late holocene conditions were inferred from plant macrofossils in rodent middens is the reason for this disagreement to be attributed to misinterpretation of the paleoenvironments or of the proxy records themselves or to incomplete paleoclimatic interpretation of the paleoenvironments we argue that these different paleoclimate archives record different aspects and facets of climate while paleosols and groundwater in the atacama desert record low frequency climate variability at century to millennium scales lake sediments on the altiplano record decade to century scale variability terrestrial vegetation responds to shorter high frequency climate variability at seasonal to inter annual scales and preferably to humid years vegetation remains in hibernation or does not germinate during arid years thus information from these three types of archives is not a priori comparable and requires careful site specific archive specific and time scale specific evaluation what is natural in modern climatology is also true for paleoclimatology a comprehensive assessment must account for the complex daily and seasonal cycles for the range of climate variability and trends at different scales in space and time for impacts of short term extreme events and for specific often non linear responses of individual bio geo physical archives to any of the numerous aspects of climate

meanders and detached eddies of a strong eastward flowing jet using a two layer quasi geostrophic model abstract the process of meander growth on and eddy detachment from an eastward flowing oceanic jet which is modeled after the gulf stream east of cape hatteras is studied using numerical solutions of nonlinear equations the equations express potential vorticity conservation in a two layer quasi geostrophic model with a weak planetary effect solutions are restricted to a spatially periodic temporally growing case initially small amplitude meanders are given being superimposed on the jet the solutions describe a process in which the meanders grow increasingly larger the larger meanders are cut off and cyclonic and anticyclonic eddies are detached southward and northward respectively concurrent with the eddy detachment an eastward flow is restored in the upper layer and the lower layer develops an eastward flow under the restored jet and two westward flows north and south of it a baroclinic instability is very effective in meander growth while a weak effect is necessary for eddy detachme

9 400 yr b p the mortality of mollusk shell mya truncata at high arctic is associated with a sudden cooling event an 118 cm long well preserved sediment profile was collected from a paleo notch formed by ocean wave action before rising to the terrace on ny alesund svalbard norway a large number of mollusk shell fragments predominantly mya truncata were found in the sediment profile ams 14c dating and stable oxygen and carbon isotope analyses were performed on the shell fragments samples the reservoir corrected radiocarbon ages averaged 9 400 yr b p which accurately dates the raised terrace and the upper marine limit after kongsfjorden was completely deglaciated the calibrated aragonite isotopic temperature equation was established for ny alesund by comparing the 18o profiles of modern mollusks as follows t c 16 26 3 68 18oaragonite pdb 18owater vsmow the reconstructed paleotemperature range was 0 52 to 4 78 c warmer than today by about 1 c which was further confirmed by reconstructed sea surface temperature sst in west svalbard moreover the mortality of mollusks was very likely caused by an abrupt cooling event at about 9 400 yr b p which was triggered by reduced insolation weakened thermohaline circulation and abruptly decreased sst more evidences for this distinct but short cooling event centered at about 9 400 yr b p were found in northern siberia north atlantic alps and eastern europe

synchronized proxy based temperature reconstructions reveal mid to late holocene climate oscillations in high arctic svalbard existing paleoclimate data are exceedingly sparse from southern spitsbergen a high arctic region predicted to experience significant environmental changes because of amplified warming we analyzed biotic and isotopic paleolimnological proxies to reconstruct past climate from a lacustrine sediment core with a basal age of 5500 a bp in southern spitsbergen 77 n we used fossil chironomidae assemblages to quantitatively reconstruct past mean july air temperatures and stable oxygen isotope values 18o of these fossils to estimate changes in mean annual air temperature these proxy records are strikingly similar and show that the coldest anomaly since the mid holocene occurred between 350 and 50 cal a bp during the little ice age whereas the warmest period in the summer temperature record occurred between 5500 5000 and 2000 cal a bp our findings indicate that the natural long term air temperature dynamics in our study area are most likely connected to solar minima and positive feedback mechanisms from sea surface temperature maxima the results also highlight that the recent temperature increase is unprecedented in its rate with a 2 c increase in the summer temperatures during the past 50 years

arctic holocene glacier fluctuations reconstructed from lake sediments at mitrahalvoya spitsbergen the arctic region has experienced a significantly larger warming during the last decades compared to the rest of the world and model simulations indicate a continued amplification of future global warming in the polar regions a better understanding of natural climate variability in the arctic is much needed to provide a better context for the observed warming trend by utilising proxy data it is possible to obtain palaeoclimatic records beyond the range of instrumental observations which increase our understanding of long term arctic climate change here a continuous record of past changes in equilibriumline altitude ela has been reconstructed for the alpine glacier karlbreen located on the northwest coast of spitsbergen 79 n based on sediment analyses from a distal glacier fed lake a multivariate statistical analysis suggests that the concentration of geochemical elements ti si and k in the lake sediments together with the physical parameter dry bulk density dbd reflect changes in the amount of inorganic detrital input to klosa which is closely linked to the size and ela of the upstream glacier karlbreen a linear regression model based on historically documented glacier extents was used to calculate continuous ela changes back to 3500 cal yr bp from about 9200 to 3500 cal yr bp the sedimentary record indicates that karlbreen was very small or had completely melted away karlbreen was probably close to its maximum holocene extent several times during the neoglacial first around 1700 cal yr bp then later at 225 and 135 cal yr bp an ice cored moraine system in front of karlbreen extends well into the main basin of klosa and it is difficult to explain how this moraine could have formed without disturbing the sedimentary record in the lake e g through slumping events the sedimentary record in klosa is continuous and undisturbed over the past 6700 years suggesting that the outermost moraine formed prior to this time and that it most likely survived the holocene thermal maximum on svalbard

late quaternary environmental dynamics in the atacama desert reconstructed from rodent midden pollen records in the past two decades much has been learned about the late quaternary climate history of the atacama desert with some details still unclear about the seasonality timing and extent of wet and dry phases modern climate studies reveal that far from exhibiting a unique pattern seasonal precipitation originates from many sources and mechanisms for the last 16 ka we attempt to sort out these complexities in pollen records from four fossil rodent midden series spanning 22 25 s in northern chile widespread wet conditions prevailed during the late pleistocene and early holocene particularly between 13 and 9 ka evidenced by 400 m lowering of pollen zones plant communities compared to today regional differences in the timing and magnitude of this displacement may be related to the prevailing source tropical extra tropical or mode nnw se of tropical precipitation through time wet conditions persisted well into the early holocene lasting 1 1 5 ka longer than previously suggested the pollen record suggests extreme drying 8 ka possibly associated with a northward shift of the inter tropical convergence zone tracking minimum insolation values at subtropical latitudes during the austral summer the establishment of conditions similar to today happened 4 ka copyright 2017 john wiley sons ltd

late weichselian environmental change in norway including svalbard a synthesis of the principal environmental changes that are inferred to have occurred in norway and svalbard fig 1 during the late glacial period 14 9 ka bp is presented the paper has three sections dealing separately with i western norway ii northern norway and iii spitsbergen svalbard the main conditions described include glacial events sea level changes vegetation history and climatic variations a summary chart of environmental reconstructions is presented for each of the three areas each including a curve of temperature reconstructions for the late glacial period these indicate some significant regional variations in contemporaneous thermal conditions during the late glacial

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

holocene climate and landscape evolution east of the pechora delta east european russian arctic this study presents a multiproxy record of holocene environmental change in the region east of the pechora delta a peat plateau profile ortino ii is analyzed for plant macrofossils sediment type loss on ignition and radiocarbon dating a paleosol profile ortino iii is described and radiocarbon dated a previously published peat plateau profile ortino i was analyzed for pollen and conifer stomata loss on ignition and radiocarbon dating the interpretation of the latter site is reassessed in view of new evidence spruce immigrated to the study area at about 8900 14c yr b p peatland development started at approximately the same time during the early holocene hypsithermal taiga forests occupied most of the present east european tundra and peatlands were permafrost free cooling started after 5000 14c yr b p resulting in a retreat of forests and permafrost aggradation remaining forests disappeared from the study area around 3000 14c yr b p coinciding with more permafrost aggradation the retreat of forests resulted in landscape instability and the redistribution of sand by eolian activity the displacement of the arctic forest line and permafrost zones indicates a warming of at least 2 3 c in mean july and annual temperatures during the early holocene at least two cooling periods can be recognized for the second half of the holocene starting at about 4800 and 3000 14c yr b p

early holocene temperature variability in the nordic seas the role of oceanic heat advection versus changes in orbital forcing received 7 january 2011 revised 15 july 2011 accepted 21 july 2011 published 22 october 2011 1 the separate roles of oceanic heat advection and orbital forcing on influencing early holocene temperature variability in the eastern nordic seas is investigated the effect of changing orbital forcing on the ocean temperatures is tested using the 1dice model and the 1dice results are compared with new and previously published temperature reconstructions from a transect of five cores located underneath the pathway of atlantic water from the faroe shetland channel in the south to the barents sea in the north the stronger early holocene summer insolation at high northern latitudes increased the summer mixed layer temperatures however ocean temperatures underneath the summer mixed layer did not increase significantly the absolute maximum in summer mixed layer temperatures occurred between 9 and 6 ka bp representing the holocene thermal maximum in the eastern nordic seas in contrast maximum in northward oceanic heat transport through the norwegian atlantic current occurred approximately 10 ka bp the maximum in oceanic heat transport at 10 ka bp occurred due to a major reorganization of the atlantic ocean circulation entailing strong and deep rejuvenation of the atlantic meridional overturning circulation combined with changes in the north atlantic gyre dynamic causing enhanced transport of heat and salt into the nordic seas

holocene climate reconstructions from the fennoscandian tree line area based on pollen data from toskaljavri due to its location on the eastern north atlantic seaboard the fennoscandian tree line area is an ideal area to use biological proxies to assess the relative roles of the scandinavian ice sheet and of oceanic atmospheric and astronomic forcings on regional climate history here we report pollen based july mean temperature tjul and annual precipitation pann reconstructions from a sediment core from a high altitude tree line lake in northwestern finland the reconstructions suggest that at 9600 8300 cal yr b p tjul values were low but steadily rising while pann was high the period of warmest summers with tjul values ca 1 8 1 6 c higher than at present occurred at ca 8000 6500 cal yr b p since then climate has become gradually cooler tjul values during the medieval warm period ca 1400 1000 cal yr b p were ca 0 8 c higher that at present but decreased rapidly to the low little ice age levels at 800 cal yr b p we compare these results with an earlier pollen based climate reconstruction from the same region the reconstructions indicate a similar general holocene tjul pattern with lower values in the reconstruction from the high altitude lake however most of the small scale variations are not synchronous suggesting that they may represent noise rather than signal in our data c 2002 university of washington

holocene treeline history and climate change across northern eurasia radiocarbon dated macrofossils are used to document holocene treeline history across northern russia including siberia boreal forest development in this region commenced by 10 000 yr b p over most of russia forest advanced to or near the current arctic coastline between 9000 and 7000 yr b p and retreated to its present position by between 4000 and 3000 yr b p forest establishment and retreat was roughly synchronous across most of northern russia treeline advance on the kola peninsula however appears to have occurred later than in other regions during the period of maximum forest extension the mean july temperatures along the northern coastline of russia may have been 2 5 to 7 0 c warmer than modern the development of forest and expansion of treeline likely reflects a number of complimentary environmental conditions including heightened summer insolation the demise of eurasian ice sheets reduced sea ice cover greater continentality with eustatically lower sea level and extreme arctic penetration of warm north atlantic waters the late holocene retreat of eurasian treeline coincides with declining summer insolation cooling arctic waters and neoglaciation