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

spectral characterization of periglacial surfaces and geomorphological units in the arctic lena delta using field spectrometry and remote sensing abstract important environmental parameters in arctic periglacial landscapes i e permafrost temperature active layer depth soil moisture precipitation vegetation cover will very likely change in a warming climate the thawing of permafrost especially might cause massive landscape changes due to thermokarst and an enhanced release of greenhouse gasses from the large amounts of carbon stored in frozen deposits resulting in positive climate warming feedback for the identification mapping and quantification of such changes on various scales up to the entire circum arctic remote sensing and spatial data analysis are essential tools in this study an extensive field work dataset including spectral surface properties vegetation soils and geomorphology was acquired in the largest arctic delta formed by a single river the siberian lena river delta a portable field spectrometer asd fieldspec pro fr was used for spectral surveys of terrain surfaces and optical satellite data landsat enhanced thematic mapper etm chris proba were used for the characterization manual mapping and automatic classification of typical periglacial land cover units in the lena delta qualitative data from soils vegetation soil moisture and relief units were correlated with the field spectral data and catalogued for a wide variety of surface types the wide range of micro and meso scale variations of periglacial surface features in the delta results in distinctive spectral characteristics for different land cover units the three main delta terraces could also be spectrally separated and characterized the present dataset provides a basis for further spectral data acquisitions in the lena delta and for comparisons with periglacial surfaces from other regions

cruising an archive on the palaeoclimatic value of the lena delta today there are only a handful of millennial long and annually resolved tree ring chronologies in existence explicit gaps in the global distribution of these regional chronologies together with an overall declining sample size back in time compel a community wide challenge to discover new tree ring based climate proxy records here we present evidence for a yet unexplored palaeoenvironmental archive define allied research tasks and emphasize probable hurdles within and beyond academia in pursuit of answering this challenge

evolution of thermokarst in east siberian ice rich permafrost a case study thermokarst lakes and basins are major components of ice rich permafrost landscapes in east siberian coastal lowlands and are regarded as indicators of regional climatic changes we investigate the temporal and spatial dynamics of a 7 5 km2 partly drained thermokarst basin alas using field investigations remote sensing geographic information systems gis and sediment analyses the evolution of the thermokarst basin proceeded in two phases the first phase started at the pleistocene holocene transition 13 to 12 ka bp with the initiation of a primary thermokarst lake on the ice complex surface the lake expanded and persisted throughout the early holocene before it drained abruptly about 5 7 ka bp thereby creating a 20 m deep alas with residual lakes the second phase 5 7 ka bp to present is characterized by alternating stages of lower and higher thermokarst intensity within the alas that were mainly controlled by local hydrological and relief conditions and accompanied by permafrost aggradation and degradation it included diverse concurrent processes like lake expansion and stepwise drainage polygonal ice wedge growth and the formation of drainage channels and a pingo which occurred in different parts of the alas this more dynamic thermokarst evolution resulted in a complex modern thermokarst landscape however on the regional scale the changes during the second evolutionary phase after drainage of the initial thermokarst lakes were less intense than the early holocene extensive thermokarst development in east siberian coastal lowlands as a result of a significant regional change to warmer and wetter climate conditions

methane oxidation following submarine permafrost degradation measurements from a central laptev sea shelf borehole submarine permafrost degradation has been invoked as a cause for recent observations of methane emissions from the seabed to the water column and atmosphere of the east siberian shelf sediment drilled 52 m down from the sea ice in buor khaya bay central laptev sea revealed unfrozen sediment overlying ice bonded permafrost methane concentrations in the overlying unfrozen sediment were low mean 20 m but higher in the underlying ice bonded submarine permafrost mean 380 m in contrast sulfate concentrations were substantially higher in the unfrozen sediment mean 2 5 mm than in the underlying submarine permafrost mean 0 1 mm using deduced permafrost degradation rates we calculate potential mean methane efflux from degrading permafrost of 120 mg m 2 yr 1 at this site however a drop of methane concentrations from 190 m to 19 m and a concomitant increase of methane 13c from 63 to 35 directly above the ice bonded permafrost suggest that methane is effectively oxidized within the overlying unfrozen sediment before it reaches the water column high rates of methane ebullition into the water column observed elsewhere are thus unlikely to have ice bonded permafrost as their source

ice complex permafrost of mis5 age in the dmitry laptev strait coastal region east siberian arctic ice complex deposits locally known as the buchchagy ice complex are exposed at both coasts of the east siberian dmitry laptev strait and preserved below the yedoma ice complex that formed during mis3 and mis2 marine isotope stage and lateglacial holocene thermokarst deposits mis1 radioisotope disequilibria 230th u of peaty horizons date the buchchagy ice complex deposition to 126 16 13 kyr and 117 19 14 kyr until 98 5 kyr and 89 5 kyr the deposit is characterised by poorlysorted medium to coarse silts with cryogenic structures of horizontal ice bands lens like and lenslike reticulated segregation ice two peaty horizons within the buchchagy ice complex and syngenetic ice wedges 2e4 m wide up to 10 m high are striking the isotopic composition d18o dd of buchchagy ice wedge ice indicates winter conditions colder than during the mis3 interstadial and warmer than during mis2 stadial and similar atmospheric winter moisture sources as during the mis2 stadial buchchagy ice complex pollen spectra reveal tundra steppe vegetation and harsher summer conditions than during the mis3 interstadial and rather similar vegetation as during the mis2 stadial short term climatic variability during mis5 is reflected in the record even though the regional chronostratigraphic relationship of the buchchagy ice complex to the last interglacial remains unclear because numerical dating is widely lacking the present study indicates permafrost ice complex formation during mis5 sensu lato and its preservation afterwards palaeoenvironmental insights into past climate and the periglacial landscape dynamics of arctic lowlands in eastern siberia are deduced from the record

late weichselian ice sheets in arctic and pacific siberia abstract interpretation of space images coupled with field data on glacial geomorphology and glacial geology of northern eurasia have provided compelling evidence for a continuous late weichselian ice sheet covering the entire arctic margin of the continent in addition to the scandinavian ice sheet three ice sheets of the same order the karan east siberian and beringian are identified within the major eurasian ice sheet also there is evidence and other considerations suggesting a former ice sheet in the sea of okhotsk ice spreading centers of the ice sheets were situated on the continental shelves off the siberian coasts thus we can term the ice sheets siberian so far the conventional stratigraphic approach to the problem of siberian glaciation has proven fruitless and yielded nothing but uncertainty while geomorphological studies have discovered a wealth of glacial landforms in arctic siberia it was these landforms and their spacing that made the existence of former siberian ice sheets evident the east siberian ice sheet rested on the shelves of the eastern laptev and east siberian seas and its flow was directed radially including up the yana and indigirka rivers the beringian ice sheet was grounded on the chukchi bering and beaufort sea shelves overriding the chukchi and seward peninsulas from the north and flowing through the bering strait it was continued by a thick floating ice shelf buttressed by the submarine aleutian commander ridge the okhotsk ice sheet was grounded on the okhotsk shelf specific gemorphic signatures of marine ice sheets the glacially cut corners have been identified on all promontories jutting out into the bering and okhotsk seas the beringian and okhotsk ice sheets are consistent with the results of deep sea drilling in the adjacent north pacific during leg 145 of d v joides resolution

late quaternary ice sheet history of northern eurasia the maximum limits of the eurasian ice sheets during four glaciations have been reconstructed 1 the late saalian 140 ka 2 the early weichselian 100 80 ka 3 the middle weichselian 60 50 ka and 4 the late weichselian 25 15 ka the reconstructed ice limits are based on satellite data and aerial photographs combined with geological field investigations in russia and siberia and with marine seismic and sediment core data the barents kara ice sheet got progressively smaller during each glaciation whereas the dimensions of the scandinavian ice sheet increased during the last ice age the barents kara ice sheet attained its maximum size as early as 90 80 000 years ago when the ice front reached far onto the continent a regrowth of the ice sheets occurred during the early middle weichselian culminating about 60 50 000 years ago during the late weichselian the barents kara ice sheet did not reach the mainland east of the kanin peninsula with the exception of the nw fringe of taimyr a numerical ice sheet model forced by global sea level and solar changes was run through the full weichselian glacial cycle the modeling results are roughly compatible with the geological record of ice growth but the model underpredicts the glaciations in the eurasian arctic during the early and middle weichselian one reason for this is that the climate in the eurasian arctic was not as dry then as during the late weichselian glacial maximum

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

environmental variability in northeastern siberia during the last 13 300 yr inferred from lake diatoms and sediment geochemical parameters abstract in northeastern siberia russia a 1 2 m sediment core was retrieved and radiocarbon dated from a small and shallow lake located at the western side of the lower lena river n 69 24 e 123 50 81 m a s l the objective of this paper is to reconstruct the palaeoenvironmental variability and to infer major palaeoclimate trends that have occurred since 13 3 cal kyr bp we analysed the diatom assemblages sedimentology grain size total organic carbon toc total nitrogen tn and the elemental and mineralogical composition using x ray fluorescence xrf and x ray diffractometry xrd of the sediment core our results show parallel changes in the diatom species composition and sediment characteristics enhanced minerogenic sediment input and the occurrence of pyrite is indicative of a cold period between 12 7 and 11 6 cal kyr bp the diatom data enable a qualitative inference about the local ecological conditions to be made and reveal an oligotrophic lake system with alkaline and cold conditions during the earliest holocene moderately warmer climates are inferred for the period from 9 1 to 5 7 cal kyr bp the major shift in the diatom assemblage from dominance of small benthic fragilarioid taxa to a more complex diatom flora with an influx of several achnanthoid and naviculoid diatom species occurred after a transitional period of about 1400 yr 7 1 to 5 7 cal kyr bp at 5 7 cal kyr bp indicating a circumneutral and warmer hydrological regime during the holocene thermal maximum htm diatom valve concentrations declined starting 2 8 cal kyr bp but have been rising again since 600 cal yr bp this has occurred in parallel to the increased presence of acidophilous diatom taxa e g eunotia spp and decreased presence of small benthic fragilarioid species in the most recent sediments which is interpreted as the result of neoglacial cooling and subsequent recent climate warming our findings are compared to other lake inferred climate reconstructions along the lena river we conclude that the timing and spatial variability of the htm in the lower lena river area reveal a temporal delay from north to south

a holocene palynological record from the northeastern laptev sea and its implications for palaeoenvironmental research a 844 cm long core ps51 118 3 77 53 54 n 132 11 92 e recovered from the upper slope 122 m water depth of the laptev sea russian arctic has been studied for pollen spores and aquatic palynomorphs including freshwater green algae and cysts of marine dinoflagellates the age model was established on the basis of radiocarbon dates obtained on marine bivalve mollusk shells the available dates suggest that the analyzed sediment was accumulated during the last ca 10 8 cal ka and reveal two intervals with markedly different sedimentation rates reflecting the sedimentary regime changes of the laptev sea shelf during postglacial sea level rise very high sedimentation rates ca 4 7 mm per year in the lower part of the core 120 866 cm between ca 9 2 and 10 8 cal ka bp reflect lower than present sea levels high erosion activity and much closer position of the palaeo shoreline with the lena and yana river mouths to the core site dramatic decrease in sedimentation rates ca 0 1 mm per year during the middle and late holocene interval reflects high sea level and decreased amount of suspended material transported to the outer shelf by rivers despite the location of the core site at the continental slope and far away from the modern coastline pollen spores and fresh water algae constitute a major part of the microfossils throughout the whole record indicating great impact of the lena and yana rivers and possibly prevalent wind regime on the pollen and non pollen palynomorph npp assemblages although a number of short term decadal to multi century oscillations deviate from the mean holocene values pollen taxa percentages and pollen based numerical biome reconstructions do not show very clear trends the latter is likely a result of the mixed environmental signal and complex pollen contribution of several large environmental regions and vegetation zones of siberia drained by the lena and yana rivers the greater pollen contribution of the forested regions to the ps51 118 3 record reflects higher pollen production of the boreal trees and shrubs over the low productive arctic vegetation the intervals of the relative increase in the tundra biome scores in the ps51 118 3 record reflect decreased arboreal pollen production or and increased landscape openness within the pollen source area and can be correlated within the uncertainty of the age models with the cold episodes observed in the greenland ice and north atlantic sediment records

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

transient eddy formation around headlands eddies with length scales of 1 10 km are commonly observed in coastal waters and play an important role in the dispersion of water borne materials the generation and evolution of these eddies by oscillatory tidal flow around coastal headlands is investigated with analytical and numerical models using shallow water depth averaged vorticity dynamics eddies are shown to form when flow separation occurs near the tip of the headland causing intense vorticity generated along the headland to be injected into the interior an analytic boundary layer model demonstrates that flow separation occurs when the pressure gradient along the boundary switches from favoring accelerating to adverse decelerating and its occurrence depends principally on three parameters the aspect ratio b a where b and a are characteristic width and length scales of the headland h cda where h is the water depth cd is the depth averaged drag coefficient and uo a where uo and are the magnitude and frequency of the far field tidal flow simulations with a depth averaged numerical model show a wide range of responses to changes in these parameters including cases where no separation occurs cases where only one eddy exists at a given time and cases where bottom friction is weak enough that eddies produced during successive tidal cycles coexist interacting strongly with each other these simulations also demonstrate that in unsteady flow a strong start up vortex forms after the flow separates leading to a much more intense patch of vorticity and stronger recirculation than found in steady flow

water masses and circulation in the western alboran sea and in the straits of gibraltar abstract some new elements of alboran sea circulation and water masses in close connection with flows through the straits of gibraltar are presented a general description is given of water masses found in 1981 during mediprod iv cruise from the gulf of cadiz to the gulf of lions followed by a brief review of the conditions found in the straits of gibraltar based on 1981 and 1961 observations the hydrological structure vertical and horizontal and surface and bottom currents typical of the western alboran sea are analysed we present some detailed observations about vertical currents in the deep waters near the straits and finally we analyse the characteristics of the mediterranean overflow through the straits our conclusions in part confirm those of bryden and stommel 1982 and in part shed light on the general pattern of the mediterranean currents entering the alboran sea from the east however considering the suggestion of stommel bryden and mangelsdorf 1973 that the deep currents in the interior of the western mediterranean basin are basically controlled by a bernoulli flow induced by the intense currents in the straits and the weak vertical stratification in the mediterranean we suggest that an interaction of a large scale circulation pattern and the topography of the alboran basin which is much shallower than the western mediterranean basin may play a major role in controlling hydraulically the deep mediterranean waters overflow a detailed water mass analysis of 1981 data and comparison with previous data revealed a time and space variability in the mediterranean waters the scales of this variability are unknown but the s variations make it difficult to make assumptions as to the depth of origin of the deep waters found in the alboran sea which flow into the atlantic ocean over the gibraltar sill

holocene climate conditions in central yakutia eastern siberia inferred from sediment composition and fossil chironomids of lake temje abstract a 380 cm long sediment core from lake temje central yakutia eastern siberia was studied to infer holocene palaeoenvironmental change in the extreme periglacial setting of eastern siberia during the last 10 000 years data on sediment composition were used to characterize changes in the depositional environment during the ontogenetic development of the lake temje the analysis of fossil chironomid remains and statistical treatment of chironomid data by the application of a newly developed regional russian transfer functions provided inferences of mean july air temperatures tjuly and water depths wd reconstructed wds show minor changes throughout the core and range between 80 and 120 cm all the fluctuations in reconstructed water depth lie within the mean error of prediction of the inference model rmsep 0 35 so it is not possible to draw conclusions from the reconstructions a qualitative and quantitative reconstruction of holocene climate in central yakutia recognized three stages of palaeoenvironmental changes the early holocene between 10 and 8 ka bp was characterized by colder than today and moist summer conditions cryotextures in the lake sediments document full freezing of the lake water during the winter time a general warming trend started around 8 0 ka bp in concert with enhanced biological productivity reconstructed mean tjuly were equal or up to 1 5 c higher than today between 6 0 ka and 5 0 ka bp during the entire late holocene after 4 8 ka bp reconstructed mean tjuly remained below modern value limnological conditions did not change significantly the inference of a mid holocene climate optimum supports scenarios of holocene climatic changes in the subpolar part of eastern siberia and indicates climate teleconnections to the north atlantic realm

characterisation of bacterial populations in arctic permafrost soils using bacteriohopanepolyols bacteriohopanepolyols bhps are biomarkers providing taxonomically and environmentally diagnostic information bhps may help to unravel the composition of bacterial communities residing in recent as well as ancient permafrost soils and sediments and also provide information on associated environmental conditions however detailed data on their distribution in the heterogeneous arctic environment are scarce the distribution and structural diversity of bhps were studied in the annually thawing active layer of three different sites in the polygonal tundra of the lena delta in the siberian arctic variations between permafrost structures and soil horizons caused by differences in the physical and chemical soil properties were observed c and n content is significantly correlated with the bhp composition so that the highest bhp concentrations and greatest structural diversity occur in the uppermost organic soil horizons which consist mainly of fresh or little degraded plant material furthermore statistical analyses reveal that higher abundances of adenosylhopane type soil marker bhps are linked to higher soil ph values small scale environmental controls on bhp distributions are reflected by amine functionalised bhps from methanotrophic bacteria only occurring in the water saturated oxygen depleted polygon centres and by soil marker bhps which are significantly more abundant in the well aerated polygon rims than in the centres in contrast c 2 methylated bhps putative indicators of plant bacterial interactions are present in all soil horizons and permafrost structures and their relative distribution is not systematically linked to soil properties overall lipid based results agree with published 16s rrna based community structure assessments highlighting the usefulness of bhps to represent bacterial populations in recent and ancient permafrost soils

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

kame deltas provide evidence for a new glacial lake and suggest early glacial retreat from central lower michigan usa abstract in association with an undergraduate honors seminar at michigan state university we studied two small kame deltas in north central lower michigan these recently identified deltas provide clear evidence for a previously unknown proglacial lake glacial lake roscommon in this large basin located in an interlobate upland our first goal was to document and characterize the geomorphology of these deltas because both deltas are tied to ice contact ridges that mark the former position of the retreating ice margin within the lake our second goal was to establish the age of one of the deltas thereby constraining the timing of ice retreat in this part of michigan for which little information currently exists both deltas are composed of well sorted fine and medium sands with little gravel and have broad nearly flat surfaces and comparatively steep fronts samples taken from the upper 1 5 m of the deltas show little spatial variation in texture aside from a general fining toward their outer margins gullies on the outer margins of both deltas probably postdate the formation of the deltas proper we suggest that they formed by runoff during a permafrost period subsequent to lake drawdown we named the ice lobe that once covered this area the mackinac lobe because it had likely advanced into the region across the mackinac straits area five of six optically stimulated luminescence osl ages from one of the deltas had minimal scatter and were within 1000 years of one another with a mean age of 23 1 0 4 ka these ages suggest that the mackinac lobe had started to retreat from the region considerably earlier than previously thought even while ice was near its maximum extent in illinois and indiana and the remainder of michigan was ice covered this early retreat which appears to coincide with a short lived warm period indicated from the greenland ice core formed an opening that was at least occasionally flooded thick and deep fine textured deposits which underlie much of the region probably date to this time our work provides the first evidence of this extremely early ice retreat from central lower michigan occurring almost 4000 years before the southern margin of the ice saginaw lobe had started its retreat from the state

quaternary glaciations in the verkhoyansk mountains northeast siberia geomorphological mapping revealed five terminal moraines in the central verkhoyansk mountains the youngest terminal moraine i was formed at least 50 ka ago according to new irsl infrared optically stimulated luminescence dates older terminal moraines in the western foreland of the mountains are much more extensive in size although the smallest of these older moraines moraine ii has not been dated moraine iii is 80 to 90 ka moraine iv is 100 to 120 ka and the outermost moraine v was deposited around 135 ka this glaciation history is comparable to that of the barents and kara ice sheet and partly to that of the polar ural mountains regarding the timing of the glaciations however no glaciation occurred during the global last glacial maximum mis 2 based on cirque orientation and different glacier extent on the eastern and western flanks of the verkhoyansk mountains local glaciations are mainly controlled by moisture transport from the west across the eurasian continent thus glaciations in the verkhoyansk mountains not only express local climate changes but also are strongly influenced by the extent of the eurasian ice sheets

detection of landscape dynamics in the arctic lena delta with temporally dense landsat time series stacks abstract arctic permafrost landscapes are among the most vulnerable and dynamic landscapes globally but due to their extent and remoteness most of the landscape changes remain unnoticed in order to detect disturbances in these areas we developed an automated processing chain for the calculation and analysis of robust trends of key land surface indicators based on the full record of available landsat tm etm and oli data the methodology was applied to the 29 000 km2 lena delta in northeast siberia where robust trend parameters slope confidence intervals of the slope and intercept were calculated for tasseled cap greenness wetness and brightness ndvi and ndwi and ndmi based on 204 landsat scenes for the observation period between 1999 and 2014 the resulting datasets revealed regional greening trends within the lena delta with several localized hot spots of change particularly in the vicinity of the main river channels with a 30 m spatial resolution various permafrost thaw related processes and disturbances such as thermokarst lake expansion and drainage fluvial erosion and coastal changes were detected within the lena delta region many of which have not been noticed or described before such hotspots of permafrost change exhibit significantly different trend parameters compared to non disturbed areas the processed dataset which is made freely available through the data archive pangaea will be a useful resource for further process specific analysis by researchers and land managers with the high level of automation and the use of the freely available landsat archive data the workflow is scalable and transferrable to other regions which should enable the comparison of land surface changes in different permafrost affected regions and help to understand and quantify permafrost landscape dynamics

crustal emplacement of exhuming ultra high pressure rocks will that be pro or retro side ultra high pressure u hp rocks form and exhume from deep within subduction channels but subsequent horizontal transport in the shallower orogenic crust makes it difficult to reconstruct their tectonic histories we use a conceptual framework and numerical models to show that buoyant exhumation from within a subduction conduit formed during one sided subduction may lead to emplacement of u hp rocks into either the lower plate prowedge or upper plate retrowedge of an orogen depending on whether the upper plate crust deforms or acts as a backstop during exhumation both modes may operate at different positions or different times within an orogen leading to emplacement of u hp rocks into both plates without changing subduction geometry we propose that retrotransport during exhumation may explain some u hp rocks e g liverpool land situated in the upper plate of the greenland norwegian caledonides

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

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

testate amoebae protozoa testacealobosea and testaceafilosea as bioindicators in the late quaternary deposits of the bykovsky peninsula laptev sea russia testate amoebae protozoa testacea were studied in the late quaternary permafrost deposits in the siberian arctic bykovsky peninsula of the laptev sea coast 71 40 71 80 n and 129 129 30 e the testacea associations studied reflect specific environmental conditions in paleocryosols which were controlled by the local micro relief as well as by regional climate conditions in total 86 species varieties and forms of testate amoebae were found in 38 pleistocene and holocene samples the rhizopods indicate that soil conditions at ca 53 000 14c years bp were probably rather similar to the modern cold and wet arctic tundra environment more moisture and warmer soil conditions were relatively favorable for rhizopods ca 45 300 43 000 14c years bp but it was significantly drier at about 42 000 14c years bp drier and colder environmental conditions were also present about 39 300 35 000 14c years bp the late pleistocene samples radiocarbon dated to 33 000 12 000 years bp are characterized by a low species diversity and density indicating that this period may have been extremely cold and dry this conjecture is also supported by the polymorphism of some species hydrophilic difflugia species mostly obligate hydrobiotes are broadly represented in the studied holocene samples the species composition and density of rhizopods in the majority of holocene samples suggest wet and relatively warm conditions changes in rhizopod assemblages during the last 53 000 years were not very dramatic mostly consisting of rare species and changes in the dominant species complexes during the pleistocene and holocene however these changes were more drastic during the pleistocene they were probably at least partly responsible for the disappearance of some rare testacean species such as argynnia sp

repeated megafloods from glacial lake vitim siberia to the arctic ocean over the past 60 000 years abstract cataclysmic outburst floods transformed landscapes and caused abrupt climate change during the last deglaciation whether such events have also characterized previous deglaciations is not known arctic marine cores hint at megafloods prior to oxygen isotope stage ois 2 but the overprint of successive glaciations means that geomorphological traces of ancient floods remain scarce in eurasia and north america here we present the first well constrained terrestrial megaflood record to be linked with arctic archives based on cosmogenic nuclide exposure dating and optically stimulated luminescence dating applied to glacial lake sediments a 300 m deep bedrock spillway and giant eddy bars 200 m high we reconstruct a history of cataclysmic outburst floods from glacial lake vitim siberia to the arctic ocean over the past 60 000 years three megafloods have reflected the rhythm of eurasian glaciations leaving traces that stretch more than 3500 km to the lena delta the first flood was coincident with deglaciation from ois 4 and the largest meltwater spike in arctic marine cores within the past 100 000 years isotope event 3 31 at 55 5 ka the second flood marked the lead up to the local last glacial maximum and the third flood occurred during the last deglaciation this final 3000 km3 megaflood stands as one of the largest freshwater floods ever documented with peak discharge of 4 0 6 5 million m3s 1 mean flow depths of 120 150 m and average flow velocities up to 21 m s 1

short term measurements of surface currents associated with the alboran sea gyre during donde va abstract during the period 6 18 october 1982 six flights by a u s navy research aircraft were made over the alboran sea gyre as part of the donde va experiment during five of these flights sonobuoys were dropped in a linear pattern designed to show the temporal and spatial variability of the currents that constitute the gyre a normal development consisted of approximately 15 sonobuoys dropped along the longitudinal line 4 45 w from the spanish coast to within 30 km of the moroccan coast during the following 4 hours the sonobuoys were relocated twice their positions noted and their individual drift speeds and directions derived aircraft precision radiation temperature and aircraft expendable bathythermograph data were collected concurrently with the sonobuoy drops to determine the thermal structure of the water during the drift period inertial navigation winds at the 300 m altitude of the aircraft as well as other meteorological data were also collected analysis of these data shows that at

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

circulation in the alboran see as determined by quasi synoptic hydrographic observations part ii mesoscale ageostrophic motion diagnosed through density dynamical assimilation abstract the 3d velocity field in the alboran sea western mediterranean is diagnosed through density dynamical assimilation in a primitive equation pe model with mesoscale resolution the ageostrophic motion is computed from fields produced by short term backward and forward integrations of the pe model initialized with quasi synoptic ctd data a weight function based on a low pass digital filter digital filter initialization method is applied to the resulting time series of model variables to obtain the final dynamically balanced density and 3d velocity fields the diagnosed ageostrophic motion is interpreted by comparing the vertical velocity field with that obtained from the quasigeostrophic qg equation the two methods produce very similar results with maximum vertical motions in the range of 10 20 md 1 associated with the differential advection of relative vorticity in small scale jet meanders upward downward motion upstream downstream of the ridges small local differences between

holocene paleoenvironmental records from nikolay lake lena river delta arctic russia radiocarbon dated pollen rhizopod chironomid and total organic carbon toc records from nikolay lake 73 20 n 124 12 e and a pollen record from a nearby peat sequence are used for a detailed environmental reconstruction of the holocene in the lena delta area shrubby alnus fruticosa and betula exilis tundra existed during 10 300 4800 cal yr bp and gradually disappeared after that time climate reconstructions based on the pollen and chironomid records suggest that the climate during ca 10 300 9200 cal yr bp was up to 2 3 c warmer than the present day pollen based reconstructions show that the climate was relatively warm during 9200 6000 cal yr bp and rather unstable between ca 5800 3700 cal yr bp both the qualitative interpretation of pollen data and the results of quantitative reconstruction indicate that climate and vegetation became similar to modern day conditions after ca 3600 cal yr bp the chironomid based temperature reconstruction suggests a relatively warm period between ca 2300 and 1400 cal yr bp which corresponds to the slightly warmer climate conditions reconstructed from the pollen modern chironomid and rhizopod assemblages were established after ca 1400 cal yr bp

late quaternary glaciations in northeastern russia a summary of the extent and chronology of quaternary glaciations in ne russia is presented in this paper the complex timing and style of glaciations include asynchronous development of alpine glaciers in the western and eastern part of the area while in the eastern part of ne russia well preserved moraines have been dated to the global last glacial maximum 18 24 ka in the westernmost part of the area no glacial advance took place at this time in general glacial advances were more extensive earlier rather than later in the last glacial cycle although only a handful of studies with reliable absolute ages in the vast area of ne russia exist it is clear that the number of advances throughout the region varies variable glacial response to global climate patterns is attributable to contrasting sources of precipitation an atlantic moisture source dominates in the western part of ne russia while a pacific source influences the eastern part of the region the glacial advances in the interior of ne russia are largely unexplored and further research is needed in order to understand quaternary climate change in the region copyright 2008 john wiley sons ltd

the deflection and division of an oceanic baroclinic jet by a coastal boundary a case study in the alboran sea abstract an oceanic baroclinic jet impinging on a coastal boundary represents a particular type of ocean coast interaction this specific oceanographic phenomenon is an example of the stagnation in line flows occurring in fluid dynamics with three additional features rotation stratification and a sloping boundary in this study the authors describe the density vorticity and deformation characteristics of an oceanic jet impinging on a sloping boundary the case study corresponds to the impinging process of the atlantic jet at the african coast alboran sea in the impinging region the acceleration field is divergent related to the fact that the magnitude of the deformation is larger than the magnitude of the rotation it is also found that the stagnation streamsurface does not lie in a vertical plane but tilts in the opposite direction to the tilt of the isopycnals the flow upstream of the stagnation point is characterized by backing speed convergence diffluence and negative streamwise vorticity

the lateglacial and postglacial vegetation history of the northwestern limits of beringia based on pollen stomate and tree stump evidence abstract in order to reconstruct the late and postglacial vegetation history of the northwestern edge of beringia a sediment core was collected from a lake north of the present treeline along the lower lena river of northeastern siberia and analysed for fossil pollen and stomates in addition fossil tree stumps were collected in the vicinity of the lake eight radiocarbon dates indicate that the lake sediment record spans at least the past 12 300 yr bp the early vegetation at this site was dominated by herb and shrub tundra possible evidence of younger dryas cooling consisting of a decrease in shrub birch and increases in grass and herbaceous plants occurs between 11 000 and 10 000 yr bp forests dominated by larix dahurica and including picea obovata extended northward to the site between 8500 and 3500 yr bp there is an agreement between the pollen stomate and tree stump evidence for this advance the modern vegetation of shrub tundra was established after 3500 yr bp

variations in the structure of the anticyclonic gyres found in the alboran sea historical satellite aircraft and in situ data have shown that two anticyclonic gyres the western and eastern alboran gyres are major ocean features of the alboran sea an examination of several years of satellite imagery indicates that large variations in the surface expression of these two gyres occur and that on occasion one or the other gyre disappears the disappearance of both gyres at the same time was not seen the initial disappearance of either gyre occurs on a time scale of a week to 2 weeks whereas the return may take from 3 weeks to 2 months various forcing mechanisms i e winds mass flux inflow through the straits of gibraltar and sicily and or density have been used in numerical ocean circulation models to study the dynamics of the western mediterranean sea various model results show relationships similar to those shown by the satellite imagery however no single forcing mechanism has been positively identified as the source of the disappearances and the events may be a result of a combination of forcing mechanisms

an example of meteorological effects on the alboran sea gyre following a period of weak winds an air dropped expendable bathythermograph axbt survey on july 4 1980 showed the alboran sea gyre clearly present at 100 m depth but not at the surface winds on july 5 and 6 were from the west at 12 m s and both axbt temperature distributions and satellite images then showed the gyre clearly dominating the temperature structure both at 100 m and at the surface the disparity between the surface and 100 m temperature patterns on july 4 demonstrates that caution must be used when interpreting satellite imagery in the alboran sea which has been used by several investigators as representing the gyre s structure the change in the shallow temperature distribution from july 4 to 6 is opposite to what some investigators have proposed as the normal response of the gyre to atmospheric forcing

insect faunal response to environmental changes during the last interglacial in western beringia abstract reconstruction of the last interglacial li environment could help us understand the mammoth faunal extinction and facilitate predictions of the effects of future on ecosystems this work applied the fossil insect method to a number of interglacial sites in the siberian arctic west beringia the main problem of the li in western beringia is uncertain age determinations many interesting sites are undated interpretation of warming signals is also problematic because of the special character of regional pleistocene interglacial insect communities these faunas are different from the modern ones investigation can clearly recognize interglacial faunas and with additional stratigraphic evidence correlate some units to the li insect study helps shed light on the survival of large grazing mammals in western beringia during li 1 steppe tundra areas remained in the forested regions 2 climate change provided sufficient warmth to support the steppe tundra environment in the north early holocene climate change in combination with marine transgression progressively reduced suitable habitats for large mammals until a critical point was reached insect populations were also affected but due to their small size many steppe tundra insect species remained as relicts in isolated patches of steppe tundra