sedimentary characteristics and origin of the late pleistocene ice complex on north east siberian arctic coastal lowlands and islands a review abstract the origin of late pleistocene ice rich fine grained permafrost sequences ice complex deposits in arctic and subarctic siberia has been in dispute for a long time corresponding permafrost sequences are frequently exposed along seacoasts and river banks in yedoma hills which are considered to be erosional remnants of late pleistocene accumulation plains detailed cryolithological sedimentological geochronological and stratigraphical results from 14 study sites along the laptev and east siberian seacoasts were summarized for the first time in order to compare and correlate the local datasets on a large regional scale the sediments of the ice complex are characterized by poorly sorted silt to fine sand buried cryosols toc contents of 1 2 4 8 wt and very high ground ice content 40 60 wt absolute a second large constituent of the ice complex are large syngenetic ice wedges resulting in a total ice content of the ice complex of up to 80 vol ice complex deposits were mostly formed during the middle weichselian interstadial and or during the late weichselian stadial periods a conceptual model of nival lithogenesis of ice complex deposits was developed that integrates various other formation hypotheses a combination of various local and regional paleogeographical geological and paleoclimate conditions controlled the formation of ice complex sequences during the late pleistocene in northern east siberia they are chronologically and stratigraphically but not genetically equivalent to eurasian and alaskan loess deposits

applications of organic geochemistry to paleolimnological reconstructions a summary of examples from the laurentian great lakes the organic matter content of lake sediments contains information that helps to reconstruct past environmental conditions evaluate histories of climate change and assess impacts of humans on local ecosystems the elemental isotopic and molecular compositions of organic matter buried in sediment provide evidence of the biota that have lived in a lake and its catchment area and they serve as proxies of organic matter delivery and accumulation sedimentary records from the north american great lakes provide examples of applications of organic geochemistry to paleolimnological reconstructions the records of these lakes date from retreat of the laurentide ice sheet around 12 ka include the mid holocene hypsithermal and show consequences of recent human changes low corg ntotal ratios indicate that most of the sediment organic matter in the great lakes is from algal production yet changes in biomarker molecule compositions also show that varying amounts of land plant organic matter have been delivered to the lakes elevated algal productivity that accompanies nutrient enrichments of lake waters is recorded as excursions to less negative 13c values in the organic matter of sediments that were deposited in the 1960s and 1970s increased organic carbon mass accumulation rates mirror the isotopic excursions in most parts of the great lakes accumulations of petroleum residues and pyrogenic polycyclic aromatic hydrocarbons in sediments identify fluvial and eolian delivery of organic matter components to different parts of the great lakes emerging applications of multiple and novel organic geochemical proxies to paleolimnological reconstructions are promising yet some potentially important measurements remain underutilized

ba distribution in surface southern ocean sediments and export production estimates 1 we present excess ba baxs data i e total ba corrected for lithogenic ba for surface sediments from a north south transect between the polar front zone and the northern weddell gyre in the atlantic sector and between the polar front zone and the antarctic continent in the indian sector focus is on two different processes that affect excess ba accumulation in the sediments sediment redistribution and excess ba dissolution the effect of these processes needs to be corrected for in order to convert accumulation rate into vertical rain rate the flux component that can be linked to export production in the southern ocean a major process affecting ba accumulation rate is sediment focusing which is corrected for using excess 230 th this correction however may not always be straightforward because of boundary scavenging effects a further major process affecting excess ba accumulation is barite dissolution during exposure at the sediment water column interface export production estimates derived from excess 230 th and barite dissolution corrected baxs accumulation rates i e excess ba vertical rain rates are of the same magnitude but generally larger than export production estimates based on water column proxies 234 th deficit in the upper water column particulate excess ba enrichment in the mesopelagic water column we believe export production values based on excess ba vertical rain rate might be overestimated due to inaccurate assessment of the baxs preservation rate barite dissolution has in general been taken into account by relating it to exposure time before burial depending on the rate of sediment accumulation however the observed decrease of excess ba content with increasing water column depth or increasing hydrostatic pressure illustrates the dependence of barite preservation on degree of saturation in the deep water column in accordance with available thermodynamic data therefore correction for barite dissolution would not be appropriate by considering only exposure time of the barite to some uniformly undersaturated deep water but requires also that regional differences in degree of undersatuation be taken into account index terms 1050 geochemistry marine geochemistry 4835 4850 4835 oceanography biological and chemical inorganic marine chemistry keywords excess ba sediment southern ocean export production

new insights into the weichselian environment and climate of the east siberian arctic derived from fossil insects plants and mammals multidisciplinary study of a key section on the laptev sea coast bykovsky peninsula east lena delta in 1998 2001 provides the most complete record of middle and late weichselian environments in the east siberian arctic the 40 m high mamontovy khayata cliff is a typical ice complex section built of icy silts with a network of large syngenetic polygonal ice wedges and is richly fossiliferous in combination with pollen plant macrofossil and mammal fossils a sequence of ca 70 insect samples provides a new interpretation of the environment and climate of the area between ca 50 and 12 ka the large number of radiocarbon dates from the section together with an extensive 14c database on mammal bones allows chronological correlation of the various proxies the bykovsky record shows how climate change and the last glacial maximum in particular affected terrestrial organisms such as insects and large grazing mammals both during the presumed karginsky interstadial mis 3 and the sartanian glacial mis 2 the vegetation remained a mosaic arctic grassland with relatively high diversity of grasses and herbs and dominance of xeric habitats the tundra steppe type this biome was supported by a constantly very continental climate caused by low sea level and enormous extension of shelf land variations within the broad pattern were caused mainly by fluctuations in summer temperature related to global trends but overprinted by the effect of continentality no major changes in humidity were observed nor were advances of modern type forest or forest tundra recorded suggesting a major revision of the karginsky interstadial paradigm the changing subtypes of the tundra steppe environment were persistently favourable for mammalian grazers which inhabited the shelf lowlands throughout the studied period mammal population numbers were lowered during the lgm especially toward its end and then flourished in a short but impressive peak in the latest weichselian just before the collapse of the tundra steppe biome throughout mis 3 and mis 2 the climate remained very favourable for the aggradation of permafrost no events of regional permafrost degradation were observed in the continuous bykovsky sequence until the very end of the pleistocene

eemian and late glacial holocene palaeoenvironmental records from permafrost sequences at the dmitry laptev strait ne siberia russia abstract terrestrial permafrost sections from the southern and northern coasts of dmitry laptev strait have preserved records of landscape transition from glacial to interglacial periods they allow geomorphologic and environmental changes to be traced from pre eemian time to the eemian and from the late glacial to the holocene the transition from one period to another induced extensive thawing of permafrost thermokarst evolving thermokarst depressions transformed formerly frozen ground into taberal unfrozen deposits with accumulating overlying lacustrine deposits lacustrine horizons rich in palaeontological remains retain evidence of changes in environmental conditions the pollen records reflect changes from grass sedge dominated vegetation during the early eemian to shrub dominated spectra during the middle eemian thermal optimum followed by late eemian grass sedge dominated tundra vegetation abundant larix pollen have been found in middle eemian deposits from the south coast of the dmitry laptev strait oyogos yar but are absent in similar deposits from the north coast bol shoy lyakhovsky island likely indicating that the northern tree line was located near the oyogos yar region during the eemian thermal optimum grass sedge dominated tundra vegetation occurred during the late glacial holocene transition which was replaced by shrub tundra during the early holocene rich fossil ostracod records from eemian and late glacial holocene lacustrine deposits could be correlated with the eemian thermal optimum and the late glacial allerod warm period for both periods the stable oxygen isotope data from the fossil ostracods suggest an approximate mean summer water temperature range between about 10 and 19 c in the palaeo lakes

magnetostratigraphy and high resolution lithostratigraphy of the permian triassic boundary interval in central germany abstract a comprehensive lithostratigraphic and magnetostratigraphic study was carried out in order to provide a magnetic polarity scale for the lower buntsandstein of the classic germanic trias in its type area of central germany the 300 m thick lower buntsandstein consists of 20 small scale fining upward cycles they can be correlated over large parts of the central european basin using a combination of high resolution cyclic stratigraphy and gamma ray logging on the basis of this robust lithostratigraphic framework a very precise positioning and correlation of paleomagnetic results has been realized eight outcrops and one completely cored well were collected yielding a total of 900 paleomagnetic samples from about 80 of them a characteristic remanence was obtained the consistent correlation of lithostratigraphic units and magnetozones supports an early acquisition of the characteristic magnetizations in both the magnetite bearing gray lithologies as well as the hematite bearing red brown lithologies the inter section correlation of all investigated profiles allows the creation of a well defined composite magnetic polarity scale the uppermost zechstein comprises one normal znz and two reversed zry zrz magnetozones in the overlying lower buntsandstein are delineated three normal sn1 to sn3 and three reversed sr1 to sr3 well documented magnetozones which can be correlated with magnetic records from the boreal and tethyan realms the combination of magnetostratigraphic and biostratigraphic data suggests the base of the oolite alpha 2 within the beds of the so called graubankbereich lower buntsandstein as the position of the hindeodus parvus calibrated permian triassic boundary within the germanic trias it is situated within the lowermost part of a remarkable thick normal magnetozone sn1 which is a distinctive feature occurring in virtually all magnetic records across the permian triassic boundary

cryostratigraphy of late pleistocene syngenetic permafrost yedoma in northern alaska itkillik river exposure abstract extremely ice rich syngenetic permafrost or yedoma developed extensively under the cold climate of the pleistocene in unglaciated regions of eurasia and north america in alaska yedoma occurs in the arctic foothills the northern part of the seward peninsula and in interior alaska a remarkable 33 m high exposure along the lower itkillik river in northern alaska opened an opportunity to study the unmodified yedoma including stratigraphy particle size distribution soil carbon contents morphology and quantity of segregated wedge and thermokarst cave ice the exposed permafrost sequence comprised seven cryostratigraphic units which formed over a period from 48 000 to 5 000 14c yr bp including 1 active layer 2 intermediate layer of the upper permafrost 3 4 two yedoma silt units with different thicknesses of syngenetic ice wedges 5 buried peat layer 6 buried intermediate layer beneath the peat and 7 silt layer with short ice wedges this exposure is comparable to the well known mus khaya and duvanny yar yedoma exposures in russia based on our field observations literature sources and interpretation of satellite images and aerial photography we have developed a preliminary map of yedoma distribution in alaska

holocene ice wedge polygon development in northern yukon permafrost peatlands canada ice wedge polygon iwp peatlands in the arctic and subarctic are extremely vulnerable to climatic and environmental change we present the results of a multidisciplinary paleoenvironmental study on iwps in the northern yukon canada high resolution laboratory analyses were carried out on a permafrost core and the overlying seasonally thawed active layer from an iwp located in a drained lake basin on herschel island in relation to 14 accelerator mass spectrometry ams radiocarbon dates spanning the last 5000 years we report sedimentary data including grain size distribution and biogeochemical parameters organic carbon nitrogen c n ratio d13c stable water isotopes d18o dd as well as fossil pollen plant macrofossil and diatom assemblages three sediment units sus correspond to the main stages of deposition 1 in a thermokarst lake su1 4950 to 3950 cal yrs bp 2 during transition from lacustrine to palustrine conditions after lake drainage su2 3950 to 3120 cal yrs bp and 3 in palustrine conditions of the iwp field that developed after drainage su3 3120 cal yrs bp to 2012 ce the lacustrine phase pre 3950 cal yrs bp is characterized by planktonic benthic and pioneer diatom species indicating circumneutral waters and very few plant macrofossils the pollen record has captured a regional signal of relatively stable vegetation composition and climate for the lacustrine stage of the record until 3950 cal yrs bp palustrine conditions with benthic and acidophilic diatom species characterize the peaty shallow water environments of the low centered iwp the transition from lacustrine to palustrine conditions was accompanied by acidification and rapid revegetation of the lake bottom within about 100 years since the palustrine phase we consider the pollen record as a local vegetation proxy dominated by the plant communities growing in the iwp ice wedge cracking in water saturated sediments started immediately after lake drainage at about 3950 cal yrs bp and led to the formation of an iwp mire permafrost aggradation through downward closed system freezing of the lake talik is indicated by the stable water isotope record the originally submerged iwp center underwent gradual drying during the past 2000 years this study highlights the sensitivity of permafrost landscapes to climate and environmental change throughout the holocene

geological and geomorphological evolution of a sedimentary periglacial landscape in northeast siberia during the late quaternary a wide variety of environmental records is necessary for analysing and understanding the complex late quaternary dynamics of permafrost dominated arctic landscapes a ne siberian periglacial key region was studied in detail using sediment records remote sensing data and terrain modelling all incorporated in a geographical information system gis the study area consists of the bykovsky peninsula and the adjacent khorogor valley in the kharaulakh ridge situated a few kilometres southeast of the lena delta in this study a comprehensive cryolithological database containing information from 176 sites was compiled the information from these sites is based on the review of previously published borehole data outcrop profiles surface samples and our own field data these archives cover depositional records of three periods from pliocene to early pleistocene the late pleistocene and the holocene the main sediment sequences on the bykovsky peninsula consist of up to 50 m thick ice rich permafrost deposits ice complex that were accumulated during the late pleistocene they were formed as a result of nival processes around extensive snowfields in the kharaulakh ridge slope processes in these mountains such as in the khorogor valley and alluvial proluvial sedimentation in a flat accumulation plain dominated by polygonal tundra in the mountain foreland bykovsky peninsula during the early to middle holocene warming a general landscape transformation occurred from an extensive late pleistocene accumulation plain to a strongly thermokarst dominated relief dissected by numerous depressions thermokarst subsidence had an enormous influence on the periglacial hydrological patterns the sediment deposition and on the composition and distribution of habitats climate deterioration lake drainage and talik refreezing occurred during the middle to late holocene the investigated region was reached by the post glacial sea level rise during the middle holocene triggering thermo abrasion of ice rich coasts and the marine inundation of thermokarst depressions

late quaternary paleoenvironmental records from the western lena delta arctic siberia abstract the three main lena delta terraces were formed during different stages of the late quaternary while only the first floodplain terrace is connected with active deltaic processes the second and third terraces which dominate the western part of the delta are erosional remnants of arctic paleolandscapes affected by periglacial processes the landscape dynamics of the second and the third terraces and their relationship to each other are of particular importance in any effort to elucidate the late quaternary paleoenvironment of western beringia multidisciplinary studies of permafrost deposits on the second terrace were carried out at several sites of the arga complex named after the largest delta island arga muora sise the frozen sediments predominantly consist of fluvial sands several tens of meters thick radiocarbon dated from 52 to 16 kyr bp these sands were deposited under changing fluvial conditions in a dynamic system of shifting river channels and have been additionally modified by synsedimentary and postsedimentary cryogenesis later thermokarst processes affected this late pleistocene fluvial landscape during the lateglacial and the holocene in addition eolian activity reworked the fluvial sands on exposed surfaces at least since the lateglacial resulting in dune formation in some areas contrary to the arga complex the third terrace is mainly composed of polygenetic alluvial and proluvial ice rich permafrost sequences ice complex deposits radiocarbon dated from 50 to 17 kyr bp which cover older fluvial sand units luminescence dated to about 100 50 kyr bp paleoecological records reflect tundra steppe conditions that varied locally depending on landscape dynamics during the marine isotope stage mis 4 and 3 periods and a persistent change to shrub and arctic tundra during lateglacial and holocene periods the study results indicate a continuous fluvial sedimentation environment for the laptev sea shelf in the region of the second lena delta terrace during the late pleistocene and confirm the presence of a dynamic channel system of the paleo lena river that flowed at the same time as the nearby subaerial ice complex deposits were being formed

permafrost carbon stock and decomposability of a globally significant carbon pool 1 the magnitude of future co2 induced climate warming is difficult to predict because of uncertainties in the role of ecosystems and oceans as co2 sources and sinks siberia has extensive areas 1 106 km2 of deep up to 90 m deposits of organic rich frozen loess wind blown silt that accumulated during the pleistocene but have not been considered in most global carbon c inventories similar deposits occur less extensively in alaska recent warming at high latitudes causes this permafrost permanently frozen ground to thaw raising questions about the fate of c in thawing permafrost here we show that siberian loess permafrost contains a large organic c pool 450 gt more than half the quantity in the current atmosphere that decomposes quickly when thawed and could act as a positive feedback to climate warming

fossil organic matter characteristics in permafrost deposits of the northeast siberian arctic 1 permafrost deposits constitute a large organic carbon pool highly vulnerable to degradation and potential carbon release due to global warming permafrost sections along coastal and river bank exposures in ne siberia were studied for organic matter om characteristics and ice content om stored in quaternary permafrost grew accumulated froze partly decomposed and refroze under different periglacial environments reflected in specific biogeochemical and cryolithological features om in permafrost is represented by twigs leaves peat grass roots and plant detritus the vertical distribution of total organic carbon toc in exposures varies from 0 1 wt of the dry sediment in fluvial deposits to 45 wt in holocene peats variations in om parameters are related to changes in vegetation bioproductivity pedogenic processes decomposition and sedimentation rates during past climate variations high toc high c n and low 13c reflect less decomposed om accumulated under wet anaerobic soil conditions characteristic of interglacial and interstadial periods glacial and stadial periods are characterized by less variable low toc low c n and high 13c values indicating stable environments with reduced bioproductivity and stronger om decomposition under dryer aerobic soil conditions based on toc data and updated information on bulk densities we estimate average organic carbon inventories for ten different stratigraphic units in northeast siberia ranging from 7 2 kg c m 3 for early weichselian fluvial deposits to 33 2 kg c m 3 for middle weichselian ice complex deposits to 74 7 kg c m 3 for holocene peaty deposits the resulting landscape average is likely about 25 lower than previously published permafrost carbon inventories

late quaternary ice rich permafrost sequences as a paleoenvironmental archive for the laptev sea region in northern siberia ice rich permafrost sequences with large polygonal ice wedges represent excellent archives for paleoenvironmental reconstruction such deposits contain numerous well preserved records ground ice paleosols peat beds different types of fossils which permit characterization of environmental conditions during a clearly defined period of the past 60 ka based on field investigations carried out within framework of the german russian project laptev sea system 2000 on the bykovsky peninsula se of the lena delta results from cryolithological studies sedimentological analyses as well as new radiocarbon data are presented for the first time it is shown that the ice complex accumulated without significant interruptions from approximately 60 k y b p until the end of the pleistocene geochemical data total organic carbon c n 13corg and the mass specific magnetic susceptibility clearly show changing environmental conditions from stadial to interstadial times in the late pleistocene and during the transition to the holocene these results permit us to reconstruct the development of an arctic periglacial landscape in the coastal lowland during ice complex formation in the late quaternary this evolution coincided generally with the global environmental trend up to marine isotope stage 4

vegetation and climate history in the laptev sea region arctic siberia during late quaternary inferred from pollen records abstract paleoenvironmental records from a number of permafrost sections and lacustrine cores from the laptev sea region dated by several methods 14 c ams tl irsl osl and 230 th u were analyzed for pollen and palynomorphs the records reveal the environmental history for the last ca 200 kyr for interglacial pollen spectra quantitative temperature values were estimated using the best modern analogue method sparse grass sedge vegetation indicating arctic desert environmental conditions existed prior to 200 kyr ago dense wet grass sedge tundra habitats dominated during an interstadial ca 200 190 kyr ago reflecting warmer and wetter summers than before sparser vegetation communities point to much more severe stadial conditions ca 190 130 kyr ago open grass and artemisia communities with shrub stands alnus fruticosa salix betula nana in more protected and moister places characterized the beginning of the last interglacial indicate climate conditions similar to present shrub tundra alnus fruticosa and betula nana dominated during the middle eemian climatic optimum when summer temperatures were 4 5 c higher than today early weichselian sparse grass sedge dominated vegetation indicates climate conditions colder and dryer than in the previous interval middle weichselian interstadial records indicate moister and warmer climate conditions for example in the interval 40 32 kyr bp salix was present within dense grass sedge dominated vegetation sedge grass artemisia communities indicate that climate became cooler and drier after 30 kyr bp and cold dry conditions characterized the late weichselian ca 26 16 kyr bp when grass dominated communities with caryophyllaceae asteraceae cichoriaceae selaginella rupestris were present from 16 to 12 kyr bp grass sedge communities with caryophyllaceae asteraceae and cichoriaceae indicate climate was significantly warmer and moister than during the previous interval the presence of salix and betula reflect temperatures about 4 c higher than present at about 12 11 kyr bp during the allerod interval but shrubs were absent in the younger dryas interval pointing to a deterioration of climate conditions alnus fruticosa betula nana poaceae and cyperaceae dominate early holocene spectra reconstructed absolute temperature values were substantially warmer than present up to 12 c shrubs gradually disappeared from coastal areas after 7 6 kyr bp when vegetation cover became similar to modern a comparison of proxy based paleoenvironmental reconstructions with the simulations performed by an earth system model of intermediate complexity climber 2 show good accordance between the regional paleodata and model simulations especially for the warmer intervals

soil organic carbon pools in the northern circumpolar permafrost region of all soils in the northern permafrost region is approximately 18 782 10 3 km 2 o r approximately 16 of the global soil area in the northern permafrost region organic soils peatlands and cryoturbated permafrost affected mineral soils have the highest mean soil organic carbon contents 32 2 69 6 kg m 2 here we report a new estimate of the carbon pools in soils of the northern permafrost region including deeper layers and pools not accounted for in previous analyses carbon pools were estimated to be 191 29 pg for the 0 30 cm depth 495 80 pg for the 0 100 cm depth and 1024 00 pg for the 0 300 cm depth our estimate for the first meter of soil alone is about double that reported for this region in previous analyses carbon pools in layers deeper than 300 cm were estimated to be 407 pg in yedoma deposits and 241 pg in deltaic deposits in total the northern permafrost region contains approximately 1672 pg of organic carbon of which approximately 1466 pg or 88 occurs in perennially frozen soils and deposits this 1672 pg of organic carbon would account for approximately 50 of the estimated global belowground organic carbon pool

paleoenvironmental and paleoclimatic records from permafrost deposits in the arctic region of northern siberia ice complexes extremely ice rich permafrost deposits with large ice wedges are widely distributed in the arctic region of northeast siberia they present excellent archives for the reconstruction of late quaternary paleoenvironmental conditions in nonglaciated areas in 1998 1999 and 2000 russian and german scientists worked together on the bykovsky peninsula southeast of the lena delta in order to investigate the ice complex and its associated sediments intensive cryolithological and sedimentological studies radiocarbon age determinations paleobotanical studies micropaleontological investigations studies of mammal and insect fossils and stable isotope analyses of ground ice were performed radiocarbon data have been obtained from the entire exposed sequence coveringapproximately the last 60 000 years the results indicate that compared with modern time the investig ated ice complex sequence was formed duringtwo cooler and more arid stages of the late pleistocene with relatively uniform environmental conditions separated by a stage with environmental variations and more intensive soil formation caused by climate amelioration the late pleistocene environmental changes were not as strong as those occurring during the pleistocene holocene transition where a sharp break is evident r 2002 elsevier science ltd and inqua all rights reserved

recent increase in peatland carbon accumulation in a thermokarst lake basin in southwestern alaska abstract drained thermokarst lake basins cover large areas of northern high latitude lowlands however the importance of peat accumulated in these drained basins to carbon c cycling is poorly understood results are presented here from a permafrost sediment core aimed at investigating site history lake drainage apparent carbon accumulation and paleohydrology in a thermokarst basin on the yukon kuskokwim delta in southwestern alaska the results show that a thermokarst lake existed for about 2300 years before it drained and a peatland established in the early 1600s average apparent c accumulation rate car was 12 gc m 2 yr over the 2300 years before lake drainage but increased to 120 gc m 2 yr following peatland initiation after transitioning to a sphagnum dominated peatland at 1700 ad car reduced gradually before more than doubling from the mid 1970s to the early 1980s this abrupt increase in car was possibly in response to a pacific climate regime shift in the late 1970s a transition characterized by a nearly 1 5 c increase in regional average annual temperature even after considering the differential decay of recent peat there was an increase in c accumulation after 1977 reconstructed water table depths from subfossil testate amoebae show little change throughout the past three centuries but there was a pronounced shift in testate amoeba composition after the 1977 temperature change e g absence of phryganella acropodia type and increase in hyalosphenia elegans if the results from peatlands in other drained thermokarst lake basins are consistent with the results from this study then the c accumulated in these vegetated drained basins under current warming might help offset some of the c released from thawing permafrost and thermokarst features in northern regions

the mystery of bunge land new siberian archipelago implications for its formation based on palaeoenvironmental records geomorphology and remote sensing abstract multiproxy datasets geocryology geochronology sedimentology palaeo ecology from permafrost exposures were used together with land surface information based on satellite imagery and thematic maps in order to reconstruct the lateglacial to holocene landscape and environmental dynamics of bunge land zemlya bunge this area of little relief situated in the new siberian archipelago connects the geomorphologically well structured islands of kotel ny and fadeevsky a buried thermokarst landscape was found in the northwest region of the bunge land low terrace sand plain whereas the bunge land high terrace seems to be an exposed residue of a similar late quaternary thermokarst landscape that is confirmed especially by radiocarbon accelerator mass spectrometry and optically stimulated luminescence age determinations and by pollen analyses palaeogeographically the late pleistocene periglacial landscape and sedimentation of bunge land was closely connected to kotel ny and fadeevsky only later on seismotectonical block movements resulted in reshaping parts of bunge land the bunge land low terrace area first subsided and the original landscape there was destroyed by marine inundation followed by marine sedimentation subsequent block heave of the low terrace region exposed a vast sheet of marine sands which is continuously surficially reworked by aeolian processes while the original alluvial plain landscape in the high terrace area was preserved and started degrading only by early holocene thermokarst development the studied exposures contain one of the northernmost 74 88 n environmental records for the late pleistocene holocene transition in the eurasian arctic

coastal changes in the arctic the arctic s climate system is changing air temperatures major river discharges and open water season length have increased and storm intensities and tracks are changing thirteen quantitative studies of the rates of coastline position change throughout the arctic show that recently observed changes have not increased coastal erosion rates which currently range between 0 and 2 m yr when averaged for the arctic shelf seas current data is probably insufficient both spatially and temporally however to capture change at decadal to sub decadal time scales in this context we describe the current understanding of arctic coastal geomorphodynamics with an emphasis on erosional regimes of coasts with ice rich sedimentary deposits in the laptev east siberian and beaufort seas where local coastal erosion can reach 30 m yr we also examine coasts with lithified rocky substrates where geomorphodynamics are intensified by rapid glacial retreat coastlines of svalbard greenland and the canadian archipelago are less frequently studied than ice rich continental coasts of north america and siberia and studies often focus on coastal sections composed of unlithified material as air temperature and sea ice duration and extent change longer thaw and wave seasons will intensify coastal dynamics in the arctic

paleontological records indicate the occurrence of open woodlands in a dry inland climate at the present day arctic coast in western beringia during the last interglacial abstract permafrost records accessible at outcrops along the coast of oyogos yar at the dmitry laptev strait ne siberia provide unique insights into the environmental history of western beringia during the last interglacial the remains of terrestrial and freshwater organisms including plants coleopterans chironomids cladocerans ostracods and molluscs have been preserved in the frozen deposits of a shallow paleo lake and indicate a boreal climate at the present day arctic mainland coast during the last interglacial terrestrial beetle and plant remains suggest the former existence of open forest tundra with larch larix dahurica tree alder alnus incana birch and alder shrubs duschekia fruticosa betula fruticosa betula divaricata betula nana interspersed with patches of steppe and meadows consequently the tree line was shifted to at least 270 km north of its current position aquatic organisms such as chironomids cladocerans ostracods molluscs and hydrophytes indicate the formation of a shallow lake as the result of thermokarst processes steppe plants and beetles suggest low net precipitation littoral pioneer plants and chironomids indicate intense lake level fluctuations due to high evaporation many of the organisms are thermophilous indicating a mean air temperature of the warmest month that was greater than 13 c which is above the minimum requirements for tree growth these temperatures are in contrast to the modern values of less than 4 c in the study area the terrestrial and freshwater organism remains were found at a coastal exposure that was only 3 5 m above sea level and in a position where they should have been under sea during the last interglacial when the global sea level was 6 10 m higher than the current levels the results suggest that during the last warm stage the site was inland and its modern coastal situation is the result of tectonic subsidence

peat accumulation in drained thermokarst lake basins in continuous ice rich permafrost northern seward peninsula alaska thermokarst lakes and peat accumulating drained lake basins cover a substantial portion of arctic lowland landscapes yet the role of thermokarst lake drainage and ensuing peat formation in landscape scale carbon c budgets remains understudied here we use measurements of terrestrial peat thickness bulk density organic matter content and basal radiocarbon age from permafrost cores soil pits and exposures in vegetated drained lake basins to characterize regional lake drainage chronology c accumulation rates and the role of thermokarst lake cycling in carbon dynamics throughout the holocene on the northern seward peninsula alaska most detectable lake drainage events occurred within the last 4 000 years with the highest drainage frequency during the medieval climate anomaly peat accumulation rates were highest in young 50 500 years drained lake basins 35 2 g c m 2 yr 1 and decreased exponentially with time since drainage to 9 g c m 2 yr 1 in the oldest basins spatial analyses of terrestrial peat depth basal peat radiocarbon ages basin geomorphology and satellite derived land surface properties normalized difference vegetation index ndvi minimum noise fraction mnf from landsat satellite data revealed significant relationships between peat thickness and mean basin ndvi or mnf by upscaling observed relationships we infer that drained thermokarst lake basins covering 391 km2 76 of the 515 km2 study region store 6 4 6 6 tg organic c in drained lake basin terrestrial peat peat accumulation in drained lake basins likely serves to offset greenhouse gas release from thermokarst impacted landscapes and should be incorporated in landscape scale c budgets

holocene thermokarst dynamics in central yakutia a multi core and robust grain size endmember modeling approach abstract differentiating thermokarst basin sediments with respect to the involved processes and environmental conditions is an important tool to understand permafrost landscape dynamics and scenarios and future trajectories in a warming arctic and subarctic thermokarst basin deposits have complex sedimentary structures due to the variability of yedoma source sediments reworking during the late glacial to holocene climate changes and different stages of thermokarst history here we reconstruct the dynamic growth of thermokarst lakes and basins and related changes of depositional conditions preserved in sediment sequences using a combination of biogeochemical data and robust grain size endmember analysis remma this multi proxy approach is used on 10 sediment cores each 300 400 cm deep from two key thermokarst sites to distinguish four time slices that describe the holocene thermokarst lake basin evolution in central yakutia cy biogeochemical proxies and remma reveal fine grained sedimentation with rather high lake levels and or reducing conditions and coarse grained sedimentation with rather shallow lake levels and or oxidizing i e terrestrial conditions in relation to distal and proximal depositional and post sedimentary conditions statistical analysis suggests that the biogeochemical parameters are almost independent of thermokarst deposit sedimentology thus the biogeochemical parameters are considered as signals of secondary post sedimentary reworking the remma results are clearly reflecting grain size variations and depositional conditions this indicates small scale varying depositional environments frequently changing lake levels and predominantly lateral expansion at the edges of rapidly growing small thermokarst lakes and basins these small bodies finally coalesced forming the large thermokarst basins we see today in cy considering previous paleoenvironmental reconstructions in siberia we show the initiation of thaw and subsidence during the late glacial to holocene transition between about 11 and 9 cal kyrs bp intensive and extensive thermokarst activity for the holocene thermal maximum htm at about 7 to 5 cal kyrs bp severely fluctuating water levels and further lateral basin growth between 3 5 cal kyrs bp and 1 5 cal kyrs bp and the cessation of thermokarst activity and extensive frost induced processes i e permafrost aggradation after about 1 5 cal kyrs bp however gradual permafrost warming over recent decades in addition to human impacts has led to renewed high rates of subsidence and abrupt rapid cy thermokarst processes

on the nature and origin of muck deposits in the klondike area yukon territory organic rich muck deposits which blanket auriferous gravels in the klondike area yukon territory comprise two principal stratigraphic units i a silty late pleistocene deposit and ii holocene organics lying unconformably on the silt the deposits are found predominantly in valley bottoms and if undisturbed are normally perennially frozen field and laboratory investigations of particle size mineralogy and morphology as well as organic matter and sedimentary structures indicate that the silt is both primary massive and redeposited bedded loess by weight 87 medium and coarse silt and fine sand radiocarbon dates indicate that the loess was deposited during late wisconsinan mcconnell glaciation beginning after 27 000 14c years bp the loess was likely derived from the floodplain of the yukon river during periods of low flow turf in growth position and organic matter in the silt similar to that of loessal grasslands near kluane lake suggest a grassland environment for the area during

palaeoenvironmental dynamics inferred from late quaternary permafrost deposits on kurungnakh island lena delta northeast siberia russia abstract late quaternary palaeoenvironments of the siberian arctic were reconstructed by combining data from several fossil bioindicators pollen plant macro fossils ostracods insects and mammal bones with sedimentological and cryolithological data from permafrost deposits the record mirrors the environmental history of beringia and covers glacial interglacial and stadial interstadial climate variations with a focus on the middle weichselian interstadial 50 32 kyr bp the late pleistocene to holocene sequence on kurungnakh island reflects the development of periglacial landscapes under changing sedimentation regimes which were meandering fluvial during the early weichselian colluvial or proluvial on gently inclined plaines during the middle and late weichselian and thermokarst affected during the holocene palaeoecological records indicate the existence of tundra steppe vegetation under cold continental climate conditions during the middle weichselian interstadial due to sedimentation gaps in the sequence between 32 and 17 kyr bp and 17 and 8 kyr bp the late weichselian stadial is incompletely represented in the studied outcrops nevertheless by several palaeoecological indications arctic tundra steppe vegetation under extremely cold arid conditions prevailed during the late pleistocene the tundra steppe disappeared completely due to lasting paludification during the holocene initially subarctic shrub tundra formed which later retreated in course of the late holocene cooling

deep yedoma permafrost a synthesis of depositional characteristics and carbon vulnerability abstract permafrost is a distinct feature of the terrestrial arctic and is vulnerable to climate warming permafrost degrades in different ways including deepening of a seasonally unfrozen surface and localized but rapid development of deep thaw features pleistocene ice rich permafrost with syngenetic ice wedges termed yedoma deposits are widespread in siberia alaska and yukon canada and may be especially prone to rapid thaw processes freeze locked organic matter in such deposits can be re mobilized on short time scales and contribute to a carbon cycle climate feedback here we synthesize the characteristics and vulnerability of yedoma deposits by synthesizing studies on the yedoma origin and the associated organic carbon pool we suggest that yedoma deposits accumulated under periglacial weathering transport and deposition dynamics in non glaciated regions during the late pleistocene until the beginning of late glacial warming the deposits formed due to a combination of aeolian colluvial nival and alluvial deposition and simultaneous ground ice accumulation we found up to 130 gigatons organic carbon in yedoma parts of which are well preserved and available for fast decomposition after thaw based on incubation experiments up to 10 of the yedoma carbon is considered especially decomposable and may be released upon thaw the substantial amount of ground ice in yedoma makes it highly vulnerable to disturbances such as thermokarst and thermo erosion processes mobilization of permafrost carbon is expected to increase under future climate warming our synthesis results underline the need of accounting for yedoma carbon stocks in next generation earth system models for a more complete representation of the permafrost carbon feedback

late quaternary sedimentation history of the lena delta abstract core and outcrop analysis from lena mouth deposits have been used to reconstruct the late quaternary sedimentation history of the lena delta sediment properties heavy mineral composition grain size characteristics organic carbon content and age determinations 14c ams and ir osl are applied to discriminate the main sedimentary units of the three major geomorphic terraces which form the delta the development of the terraces is controlled by complex interactions among the following four factors 1 channel migration according to the distribution of 14c and ir osl age determinations of lena mouth sediments the major river runoff direction shifted from the west during marine isotope stages 5 3 third terrace deposits towards the northwest during marine isotope stage 2 and transition to stage 1 second terrace to the northeast and east during the holocene first terrace deposits 2 eustasy sea level rise from last glacial lowstand to the modern sea level position reached at 6 5 ka bp resulted in back filling and flooding of the palaeovalleys 3 neotectonics the extension of the arctic mid ocean ridge into the laptev sea shelf acted as a halfgraben showing dilatation movements with different subsidence rates from the continent side differential neotectonics with uplift and transpression in the siberian coast ridges are active both likely have influenced river behavior by providing sites for preservation with uplift in particular allowing accumulation of deposits in the second terrace in the western sector the actual delta setting comprises only the eastern sector of the lena delta 4 peat formation polygenetic formation of ice rich peaty sand ice complex was most extensive 7 11 m in thickness in the southern part of the delta area between 43 and 14 ka bp third terrace deposits in recent times alluvial peat 5 6 m in thickness is accumulated on top of the deltaic sequences in the eastern sector first terrace

palaeobotanical evidence for warm summers in the east siberian arctic during the last cold stage plant macrofossils from the mamontovy khayata permafrost sequence 71 60 n 129 25 e on the bykovsky peninsula reflect climate and plant biodiversity in west beringia during the last cold stage 70 ams and 20 conventional 14c dates suggest sediment accumulation between about 60 000 and 7500 14c yr b p the plant remains prove that during the last cold stage arctic species minuartia arctica draba spp kobresia myosuroides coexisted with aquatic potamogeton vaginatus callitriche hermaphroditica littoral ranunculus reptans rumex maritimus meadow hordeum brevisubulatum puccinellia tenuiflora and steppe taxa alyssum obovatum silene repens koeleria cristata linum perenne the reconstructed vegetation composition is similar to modern vegetation mosaics in central and northeast yakutian relict steppe areas thus productive meadow and steppe communities played an important role in the siberian arctic vegetation during the late pleistocene and could have served as food resource for large populations of herbivores the floristic composition reflects an extremely continental arid climate with winters colder and summers distinctly warmer than at present holocene macrofossil assemblages indicate a successive paludification possibly connected with marine transgression increased oceanic influence and atmospheric humidity although some steppe taxa were still present in the early holocene they disappeared completely before 2900 14c yr b p

the principles of cryostratigraphy abstract cryostratigraphy adopts concepts from both russian geocryology and modern sedimentology structures formed by the amount and distribution of ice within sediment and rock are termed cryostructures typically layered cryostructures are indicative of syngenetic permafrost while reticulate and irregular cryostructures are indicative of epigenetic permafrost cryofacies can be defined according to patterns of sediment characterized by distinct ice lenses and layers volumetric ice content and ice crystal size cryofacies can be subdivided according to cryostructure where a number of cryofacies form a distinctive cryostratigraphic unit these are termed a cryofacies assemblage the recognition if present of i thaw unconformities ii other ice bodies such as vein ice ice wedges aggradational ice and thermokarst cave pool ice and iii ice sand and gravelly pseudomorphs is also important in determining the nature of the freezing process the conditions under which frozen sediment accumulates and the history of permafrost

facies analysis of yedoma thermokarst lakes on the northern seward peninsula alaska thermokarst lakes develop as a result of the thaw and collapse of ice rich permanently frozen ground permafrost of particular sedimentological importance are thermokarst lakes forming in late pleistocene icy silt yedoma which dramatically alter the land surface by lowering surface elevation and redistributing upland sediment into lower basins our study provides the first description of yedoma thermokarst lake sedimentology based on the cross basin sampling of an existing lake we present lake sediment facies descriptions based on data from sediment cores from two thermokarst lakes of medium depth claudi and jaeger informal names which formed in previously non thermokarst affected upland yedoma on the northern seward peninsula alaska we identify four prominent facies using sedimentological biogeochemical and macrofossil indicators a massive silt lacking aquatic macrofossils and other aquatic indicators situated below a sub lacustrine unconformity facies 1 two basal deposits interbedded organic silt and chaotic silt facies 2 3 and a silt rich mud facies 4 facies 1 is interpreted as yedoma that has thawed during lake formation facies 3 formed adjacent to the margin due to thaw and collapse events from the lake shore material from facies 3 was reworked by wave action to form facies 2 in a medium energy margin environment facies 4 formed in a lower energy environment toward the lake basin center this facies classification and description should enhance our ability i to interpret the spatial and temporal development of lakes and ii to reconstruct long term patterns of landscape change