a computer assisted thin section study of lake baikal sediments a tool for understanding sedimentary processes and deciphering their climatic signal a freeze drying technique for cutting thin sections of soft sediments without disturbance is used to study several lake baikal sedimentary microstructures image analysis methodology is applied to selected thin sections this new technique provides quantification of the size shape orientation and packing of the objects forming the sedimentary structures sedimentary processes which were previously poorly documented have been identified and others are better understood spheroidal lens like pure aggregates of the diatom genus synedra are found in hemipelagic sediments providing a new insight into their traditional paleoecological interpretation they are possibly related to a transportation mechanism from the littoral zone or to lacustrine snow laminae of aulacoseira have also been recorded evidence of rapid sedimentation suggests they are due to massive algal blooms the depositional mechanism that was suggested by other studies for explaining the laminations at the buguldeika uplift is confirmed the hemipelagic sedimentation is interrupted by terrigenous pulses due to discharge events the sedimentation rate appears to be increasing during these pulses preliminary results from the academician ridge show stronger microbioturbation during cold periods this observation strengthens the hypothesis of intense water circulation during colder times thin section image analysis provides crucial information for deciphering lacustrine records and their regional and palaeoclimatic significance

influence of grain fabric and lamination on the anisotropy of hydraulic conductivity in unconsolidated dune sands in local scale groundwater flow problems like for instance in contaminated groundwater studies it becomes increasingly important for proper prediction of contaminant migration to incorporate small scale geological and associated parameter heterogeneity in groundwater flow models of the micro scale geological heterogeneities the effect of grain fabric and lamination in unconsolidated sediments on the vertical anisotropy of effective hydraulic conductivity has received relatively little attention this is mainly due to the low conductivity contrast between laminae in combination with the friable nature of unconsolidated sediment which makes it sensitive to disturbances during experimental procedures as an alternative digital image analysis of sediment thin sections was applied to separate and quantify both causes of anisotropy the effective value of vertical anisotropy ratio of unconsolidated eolian dune sand as determined experimentally on distributed orientated core plugs ranges between 1 10 and 1 50 this wide range is partly caused by artificial noise introduced by distributed sampling in a heterogeneous medium and assuming thereby that the sampled material is homogeneous by applying digital image analysis of thin sections high resolution logs of hydraulic conductivity were generated simple upscaling of these values to effective conductivity parallel and perpendicular to sedimentary laminae provided quantitative estimates of the vertical anisotropy caused by lamination anisotropy values range between 1 0 and 1 075 the anisotropy ratio due to grain fabric ranges in value between 1 05 and 1 45 assuming that both anisotropy due to grain fabric and lamination are orientated identically if this is not the case the effective anisotropy is the weighted mean of anisotropies of the constituent layer types this study shows that for eolian sands the anisotropy owing to grain fabric dominates the effective value of anisotropy if conductivity contrast between laminae increases the contribution of anisotropy caused by grain fabric to the effective value of anisotropy decreases

assessing the potential for developing internal diatom based transfer functions for lake baikal we explore possible quantitative relationships between diatom species and environmental data for lake baikal using multivariate techniques our approach differs from published studies in other regions on training sets and transfer functions because 1 although only one lake is examined we use the internal lake gradients rather than gradients among lakes and 2 the majority of the dominant diatom taxa are endemic canonical correspondence analysis on 93 surface sediment diatom assemblages reveals that major taxa show distinct relationships with measured environmental variables five significant variables were identified snow thickness on ice which accumulates on the frozen lake surface between january and april may water depth suspended matter annual solar radiation and mean july temperature of surface waters the strongest relationship is with snow thickness which influences light levels in the water below the ice a diatom based inference model has been developed to predict snow thickness on the ice using weighted averaging wa and wa with tolerance down weighting wa tol models results suggest that lake baikal diatom assemblages in surface sediments can be used to develop a robust model for estimating snow thickness across frozen lake baikal r 2 jack 0 607 rmsep 0 138 log cm this model has potential applications for recent paleoclimate studies in this region of continental eurasia

assessing textural variation in laminated sands using digital image analysis of thin sections although between laminae parameter variations in sediments have been studied in the past measured parameters were generally limited to grain size distribution and total porosity the magnitude and directional characteristics of physical properties of laminated sediments also depend on the shape and orientation of particles packing pore size characteristics and properties of the pore network leaving out a complete characterization of granular sediment in models of physical properties could result in a systematic mismatch between modeled and measured values however tools for high resolution quantification of these spatial variable parameters are not readily available in order to provide such a tool an image analysis procedure is presented based on digital images of thin sections the procedure defines a sequence of rectangular measurement windows with their long sides oriented parallel to stratification and measures the sediment characteristics for each window logs of parameters values oriented perpendicular to stratification are thus created after verification of the image analysis procedure using comparative laboratory measurements the procedure is applied to two thin section images of unconsolidated fine grained laminated sands the quantitative variations observed in the logs of grain and pore characteristics correlate well with bedding observed on the original images overall the image analysis procedure proved to be a useful and versatile tool for quantifying variations of textural characteristics on sub lamina scale

asynchronous little ice age glacier fluctuations in iceland and european alps linked to shifts in subpolar north atlantic circulation abstract records of past glacier fluctuations are an important source of paleoclimate data and provide context for future changes in global ice volume in the north atlantic region glacier chronologies can be used to track the response of terrestrial environments to variations in marine conditions including circulation patterns and sea ice cover however the majority of glacier records are discontinuous and temporally restricted owing in part to the extensive advance of northern hemisphere glaciers during the little ice age lia the most recent and severe climate anomaly of the neoglacial period here we combine an absolutely dated and continuous record of langjokull ice marginal fluctuations with new reconstructions of sediment flux through the past 1 2 ka using varved sediments from hvitarvatn a proglacial lake in iceland s central highlands large spatial and temporal variations in sediment flux related to changing ice cap dimensions are reconstructed from six sediment cores and seismic reflection profiles sediment data reveal two discrete phases of ice expansion occurring ca 1400 to 1550 ad and ca 1680 to 1890 ad these advances are separated by a persistent interval of ice retreat suggesting that a substantial period of warming interrupted lia cold the pattern of icelandic glacier activity contrasts with that of european glaciers but shows strong similarities to reconstructed changes in north atlantic oceanographic conditions indicating differing regional responses to coupled ocean atmosphere sea ice variations our data suggest that subpolar north atlantic circulation dynamics may have led to coherent asynchronous glacier fluctuations during the mid lia and highlight the importance of circulation variability in triggering and transmitting multidecadal scale climate changes to nearby terrestrial environments

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

the paleoclimatology of lake baikal a diatom synthesis and prospectus abstract the paleoclimatic archive held in lake baikal sediments is of significant importance given the lake s position in one of the world s most continental regions where there are few continuous high quality records spanning the quaternary here i review diatom and associated biogenic silica records from lake baikal sediments and provide a paleoclimatic synthesis of changes at various timescales over the quaternary i initially highlight major climatic and hydrological aspects of lake baikal as understanding the contemporary system both regionally and within the lake are fundamental to understanding past change interpreted from the sedimentary archive in this respect special attention is given to factors that can affect the integrity of the diatom record most notably dissolution processes these mechanisms are likely to have had a relatively greater impact on the preservation of diatom valves during glacial periods because of overall lower diatom productivity lower diatom numbers and relative increased dissolution during cold periods explains the lack of diatoms and low biogenic silica concentrations found in the lake sediments during glacial periods the biogenic record highlights the nature of the 100 ka cycle especially during the last 800 ka although there is also a strong precessional component further work is needed to reassess biological responses in lake baikal with respect to different orbital forcing mechanisms together with their impacts on evolution and speciation of diatoms the biological record from lake baikal confirms that the last interglacial in central asia lasted approximately 10 5 ka productivity in the lake as inferred from diatom biovolume accumulation rates exhibits millennial scale variability with the occurrence of centennial scale reductions in diatom biomass throughout the last interglacial period the most severe reduction in diatom biomass at c 120 ka bp is concurrent with millennial scale cooling in the north atlantic region links to changes in north atlantic ocean thermohaline circulation via teleconnections are also evident in the nature of the abrupt ecological changes in the lake throughout the last 60 ka linked to ice rafting into the north atlantic otherwise known as heinrich events new robust radiocarbon chronologies for sediments deposited during the late glacial and holocene in lake baikal allow detailed multi decadal records to be constructed for the last 14 000 years cooling events associated with millennial scale cycles are also apparent in the lake baikal record and both the diatom record and oxygen isotope record of the diatom silica highlight that biological responses to these abrupt events are almost simultaneous comparisons made between lake baikal records with others worldwide highlights that many of the holocene cooling events are associated with melt water outburst from the laurentide ice sheet and changes in solar insolation during the last 1000 years snow cover on lake baikal has been inferred from past diatom assemblages and is closely linked to weakening of the north atlantic oscillation allowing increasing intensity of the siberian high to develop and during the 17th and 18th centuries in the last 150 years diatom species have been shown to be sensitive indicators of recent warming however impacts from future global warming will be complex and are likely to impact not only on the balance between endemic and cosmopolitan diatoms throughout the lake but on the balance between siliceous and non siliceous algae and sources of primary productivity

a new approach for reconstructing holocene temperatures from a multi species long chain alkenone record from lake qinghai on the northeastern tibetan plateau abstract the extent of unsaturation in long chain alkenones lcks in lakes has potential for quantitatively indicating paleotemperature in terrigenous environments however the traditional temperature proxies derived from marine lcks may not be able to address the problem related to the prevalent species effect which restricts the application of lcks in lacustrine studies in our lck record from the northeastern tibetan plateau c 37 c 38 differences revealed that the lck producer species in lake qinghai may have changed during the holocene this possible species effect may have caused inconsistency between the u k 37 and u k 37 records therefore we formulated a new proxy u ks 37 with a parameter s to indicate the different exponential response in lck unsaturation to temperature change in multiple species our u ks 37 derived temperature time series resembles the general temperature trends of the northern hemisphere on a millennial scale while exhibiting several apparent cold events especially at ca 9 ka the result shows that the holocene optimum in lake qinghai was interrupted by cold events in the early holocene this could be a result of a weak asia summer monsoon and cold air transmission in the north atlantic

quantitative and qualitative relationships between planktonic diatom communities and diatom assemblages in sedimenting material and surface sediments in lake baikal siberia endemic planktonic diatoms are a major component of lake baikal sediments during interglacial periods to investigate how these diatom assemblages are altered during sediment formation quantitative plankton monitoring 1995 1998 was integrated with sediment trapping over 2 yr 1996 1997 in baikal s southern basin depth 1 400 m the traps consisted of both open 6 monthly and sequential 2 weekly collectors deployed throughout the water column sedimentation was seasonal with diatom species composition valve abundance and total dry mass reflecting changes in the planktonic communities sedimented assemblages were transmitted largely intact to the deepest traps 1 300 1 390 m some compositional blurring occurred from differential sinking rates and dissolution of diatom valves a rapid mass flux event of aulacoseira skvortzowii and a baicalensis was recorded in summer 1997 with particle sinking rates between 60 and 100 m d 21 and dry mass fluxes 5gm 22 d 21 although dissolution was evident for all species more delicate taxa were preferentially affected e g a skvortzowii vegetative cells and finesynedra species whereas nitzschia acicularis valves were almost entirely dissolved within the water column comparing trap and plankton diatom assemblages with those in nearby core tops demonstrated that a fundamental taphonomic change occurs in the surface sediment with sedimentary diatom accumulation rates being only about 1 of trap deposition and plankton production rates dissolution was significant in explaining 5 30 of species variance between all taphonomic levels plankton trap samples and surface sediments results indicate that diatom based paleoclimatic records in lake baikal sediments could be improved and refined by taking taphonomic considerations into account

freshwater outburst from lake superior as a trigger for the cold event 9300 years ago paleoclimate proxy records reveal a pervasive cooling event with a northern hemispheric extent approximately 9300 years ago coeval changes in the oceanic circulation of the north atlantic imply freshwater forcing however the source magnitude and routing of meltwater have remained unknown located in central north america lake superior is a key site for regulating the outflow of glacial meltwater to the oceans here we show evidence for an approximately 45 meter rapid lake level fall in this basin centered on 9300 calibrated years before the present due to the failure of a glacial drift dam on the southeast corner of the lake we ascribe the widespread climate anomaly approximately 9300 years ago to this freshwater outburst delivered to the north atlantic ocean through the lake huron north bay ottawa river st lawrence river valleys

microsedimentological characterization using image analysis and μ xrf as indicators of sedimentary processes and climate changes during lateglacial at laguna potrok aike santa cruz argentina palaeoclimatic and paleoenvironmental high latitude records in the southern hemisphere are scarce compared to the northern counterpart however understanding global evolution of environmental systems during sudden climate changes is inseparable from an equivalent knowledge of both hemispheres in this context a high resolution study of lacustrine sediments from laguna potrok aike santa cruz province patagonia argentina was conducted for the lateglacial period using concurrent x ray fluorescence xrf and scanning electron microscope analyses peaks of ca si and mn and occurrences of the green alga phacotus lenticularis have been interpreted as variations in ventilation of the water column from 13 6 to 11 1 ka cal bp during this interval mild climate conditions during the younger dryas are characterized by relatively weak westerlies favouring the formation of a stratified water body as indicated by preserved manganese and ca si peaks and high total organic carbon toc values in this environment water in the epilimnion can reach sufficiently high temperature to allow p lenticularis to grow colder conditions are marked by peaks in ca without p lenticularis and occur during the antarctic cold reversal acr in this lateglacial interval micropumices were also detected in large amount image analysis of thin sections allowed the counting and size measurement of detrital particles and micropumices separately micropumices significantly influence the iron and titanium content hence preventing to use them as proxies of detrital input in this interval

abrupt holocene climate change as an important factor for human migration in west greenland west greenland has had multiple episodes of human colonization and cultural transitions over the past 4 500 y however the explanations for these large scale human migrations are varied including climatic factors resistance to adaptation economic marginalization mercantile exploration and hostile neighborhood interactions evaluating the potential role of climate change is complicated by the lack of quantitative paleoclimate reconstructions near settlement areas and by the relative stability of holocene temperature derived from ice cores atop the greenland ice sheet here we present high resolution records of temperature over the past 5 600 y based on alkenone unsaturation in sediments of two lakes in west greenland we find that major temperature changes in the past 4 500 y occurred abruptly within decades and were coeval in timing with the archaeological records of settlement and abandonment of the saqqaq dorset and norse cultures which suggests that abrupt temperature changes profoundly impacted human civilization in the region temperature variations in west greenland display an antiphased relationship to temperature changes in ireland over centennial to millennial timescales resembling the interannual to multidecadal temperature seesaw associated with the north atlantic oscillation

extensional fault propagation folding and base level change as controls on growth strata geometries abstract outcrop and analogue modelling studies indicate that upward widening zones of distributed deformation often monoclinal folds form above blind normal faults and are particularly common features at the depositional surface during the early stages of rifting with increasing displacement strain such folds are cut by faults as they propagate upwards into the cover we use a kinematic model of fault propagation folding above a blind extensional fault together with a sedimentary model of coarse grained clastic deposition to investigate growth strata geometries associated with fault tip monoclines in particular we consider coarse grained deltaic deposition where sedimentary geometries are markedly different from the simple sub horizontal fill to the top sedimentation used in most growth strata models for a given fault dip and slip rate growth strata geometries are strongly influenced by the fault propagation to slip ratio p s and the width of the zone of distributed deformation however base level changes also act as fundamental controls on sequence development the results of a number of experiments compare favourably to well documented examples of growth strata this study highlights the importance of integrating structural and stratigraphic studies in interpreting both fault fold kinematics and the controls on stratigraphy kinematic studies need to address the depositional geometry of stratal surfaces whereas sequence stratigraphic interpretation of stratal patterns must deconvolve tectonic rotation and translation from depositional architecture

quantification of bioturbation in hemipelagic sediments via thin section image analysis traditional ichnofabric descriptive semiquantitative l schemes rely upon subjective estimates of the degree to which original sedimentary fabrics have been disrupted this paper presents an objective method of quantifying bioturbation in hemipelagic sediments based on a thin section image analysis technique in order to perform these analyses optical or backscattered electron micrographs are processed in order to obtain black and white images in these images black pixels are silt size larger grains and the clay size sedimentary matrix are white pixels once the initial processing has been accomplished an index h is defined to quantify the horizontal orientation of the larger grain size fraction of the sediment h is low for bioturbated fabric and high for laminated sediments in hemipelagic suspension deposits h can he used to quantify bioturbation assuming that no other sedimentary processes have disrupted the original depositional fabric the quantitive bioturbation scheme described here is consistent with existing semiquantitative bioturbation schemes in addition it is objective and provides higher resolution descriptions of biological processes that disrupted the sediment after deposition applying this quantitative scheme should refine future paleoecological reconstruction derived from lacustrine and marine successions

holocene sea subsurface and surface water masses in the fram strait comparisons of temperature and sea ice reconstructions highlights holocene sea subsurface temperatures after husum hald 2012 estimated from planktic foraminifer fauna in e fram strait biomarkers and ip25 derived indices including dip25 indicate surface water variability delayed onset of early holocene conditions in subsurface 10 6 ka compared to surface 11 7 ka water conditions warm atlantic layer likely occupied uppermost 200 m in eastern fram strait between 10 and 9 ka diverging late holocene trends in surface and subsurface conditions linked to presence of strong pycnocline stratification abstract two high resolution sediment cores from eastern fram strait have been investigated for sea subsurface and surface temperature variability during the holocene the past ca 12 000 years the transfer function developed by husum and hald 2012 has been applied to sediment cores in order to reconstruct fluctuations of sea subsurface temperatures throughout the period additional biomarker and foraminiferal proxy data are used to elucidate variability between surface and subsurface water mass conditions and to conclude on the holocene climate and oceanographic variability on the west spitsbergen continental margin results consistently reveal warm sea surface to subsurface temperatures of up to 6 c until ca 5 cal ka bp with maximum seawater temperatures around 10 cal ka bp likely related to maximum july insolation occurring at that time maximum atlantic water aw advection occurred at surface and subsurface between 10 6 and 8 5 cal ka bp based on both foraminiferal and dinocyst temperature reconstructions probably a less stratified ice free nutrient rich surface ocean with strong aw advection prevailed in the eastern fram strait between 10 and 9 cal ka bp weakened aw contribution is found after ca 5 cal ka bp when subsurface temperatures strongly decrease with minimum values between ca 4 and 3 cal ka bp cold late holocene conditions are furthermore supported by high planktic foraminifer shell fragmentation and high 18o values of the subpolar planktic foraminifer species turborotalita quinqueloba while ip25 associated indices as well as dinocyst data suggest a sustained cooling due to a decrease in early summer insolation and consequently sea ice increase since about 7 cal ka bp in surface waters planktic foraminiferal data including stable isotopes indicate a slight return of stronger subsurface aw influx since ca 3 cal ka bp the observed decoupling of surface and subsurface waters during the later holocene is most likely attributed to a strong pycnocline layer separating cold sea ice fed surface waters from enhanced subsurface aw advection this may be related to changes in north atlantic subpolar versus subtropical gyre activity

climatic influence of the latest antarctic isotope maximum of the last glacial period aim4 on southern patagonia abstract this paper presents the first detailed paleoclimate reconstruction of the latest antarctic isotope maximum aim4 33 29 ka cal bp at 52 s in continental southeastern argentine patagonia high resolution sedimentological and geochemical analyses of sediments from the maar lake potrok aike pta reveal a decrease in the thickness of flood induced turbidites and a series of wind burst deposits during aim4 both pointing to increasingly drier conditions this interpretation is also supported by a significant amount of runoff driven micropumices incorporated within the sediments that suggests a lower lake level with canyons incising thick tephra deposits around the lake increased gustiness and or dust availability in southeast patagonia together with intensified antarctic circumpolar circulation in the drake passage dust deposition in the scotia sea and in antarctica ice shelf are consistent with a southward shift of the southern westerly winds sww during the aim4 in contrast to other warmer aims the sww during the aim4 did not migrate far enough south to generate upwelling in the southern ocean and they did not reach 52 s in se patagonia as revealed by unchanged values of the rock magnetic proxy of wind intensity obtained from the same pta core nevertheless the sww displacement during aim4 imposed drier conditions at 52 s in southeast patagonia likely by blocking precipitation from the atlantic ocean in a way similar to modern seasonal variations and the other antarctic warm events

north atlantic holocene climate evolution recorded by high resolution terrestrial and marine biomarker records abstract holocene climatic change is driven by a plethora of forcing mechanisms acting on different time scales including insolation internal ocean e g atlantic meridional overturning circulation amoc and atmospheric e g north atlantic oscillation nao variability however it is unclear how these driving mechanisms interact with each other here we present five biomarker based paleoclimate records air sea surface temperature and precipitation from a fjordic sediment core revealing north atlantic terrestrial and marine climate in unprecedented detail the early holocene 10 7 7 8 kyrs bp is characterised by relatively high air temperatures while ssts are dampened by melt water events and relatively low precipitation the middle holocene 7 8 3 2 kyrs bp is characterised by peak ssts declining air temperatures and high precipitation a pronounced marine thermal maximum occurs between 7 5 5 kyrs bp 3000 years after the terrestrial thermal maximum driven by melt water cessation and an accelerating amoc the neoglacial cooling between 5 8 and 3 2 kyrs bp leads into the late holocene we demonstrate that an observed modern link between icelandic precipitation variability during different nao phases may have existed from 7 5 kyrs bp a simultaneous decoupling of both air and sea surface temperature records from declining insolation at 3 2 kyrs bp may indicate a threshold after which internal feedback mechanisms namely the nao evolved to be the primary drivers of icelandic climate on centennial time scales

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

distributions of uk37 and uk37 in the surface waters and sediments of the nordic seas implications for paleoceanography in this paper we revise the application of the u and u indices as sea surface temperature sst proxies in the nordic seas in the summer of 1999 and 2000 we obtained samples of filtered particulate organic matter pom from surface waters 6 m depth of the nordic seas a number of samples were collected from polar waters with up to 80 of sea ice cover alkenones were detected in all of the major water masses of the nordic seas across a spectrum of sst values from 0 5 to 13 c and sss values from 29 6 to 35 6 psu concentrations of alkenones were similar in magnitude to those reported previously for the north atlantic and the southern ocean values of u from the new nordic seas pom data show no correlation with sst below 8 c in contrast below this temperature a linear correlation exists between u and regional sst supporting previous suggestions that overall u may be a more appropriate sst index for the region it must be noted however that u is calculated using the tetraunsaturated alkenone and the dominant control on this compound is not yet fully understood the new data highlight major differences between distributions of u and u in the water column pom and surficial sediments of the nordic seas we also examine the geographical dependence of the u versus sst relationship in the region s surficial sediments some areas are associated with unreliable sst estimates whereas in others the u versus sst relationship falls within the range of a global core top calibration it is suggested that the breakdown of the u sst relationship in some regions is due to ecological and sedimentological factors the latter relates to the extension of the habitats of alkenone producers in polar waters the former to the resuspension of sediments and laterally transported alkenone inputs this suggests that accurate alkenone derived sst estimates in the nordic seas are geographically constrained

atlantic water advection versus sea ice advances in the eastern fram strait during the last 9 ka multiproxy evidence for a two phase holocene a sediment core from the west spitsbergen continental margin was studied to reconstruct climate and paleoceanographic variability during the last 9 ka in the eastern fram strait our multiproxy evidence suggests that the establishment of the modern oceanographic configuration in the eastern fram strait occurred stepwise in response to the postglacial sea level rise and the related onset of modern sea ice production on the shallow siberian shelves the late early and mid holocene interval 9 to 5 ka was generally characterized by relatively unstable conditions high abundance of the subpolar planktic foraminifer species turborotalita quinqueloba implies strong intensity of atlantic water aw inflow with high productivity and or high aw temperatures resulting in a strong heat flux to the arctic a series of short lived cooling events 8 2 6 9 and 6 1 ka occurred superimposed on the warm late early and mid holocene conditions our proxy data imply that simultaneous to the complete postglacial flooding of arctic shallow shelves and the initiation of modern sea ice production strong advance of polar waters initiated modern oceanographic conditions in the eastern fram strait at 5 2 ka the late holocene was marked by the dominance of the polar planktic foraminifer species neogloboquadrina pachyderma a significant expansion of sea ice icebergs and strong stratification of the water column although planktic foraminiferal assemblages as well as sea surface and subsurface temperatures suggest a return of slightly strengthened advection of subsurface atlantic water after 3 ka a relatively stable cold water layer prevailed at the sea surface and the study site was probably located within the seasonally fluctuating marginal ice zone during the neoglacial period

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

palaeoclimatic signals recognized by chemometric treatment of molecular stratigraphic data abstract the high resolution stratigraphy of various marker compounds has been studied using gc hplc and gc ms in a 13 m gravity core recovered from the kane gap region eastern equatorial atlantic which provides a record of the glacial interglacial episodes over the last million years downhole variations in many presumed source specific components are observed e g in n alkanes from terrigenous land plants and dinosterol from dinoflagellates which may be due to perturbations or cyclicities resulting from climatic change fluctuations in the unsaturation of alkenones attributable to variations in water temperatures show correlations with the glacial interglacial cycles recorded in the 18 o values for planktonic foraminifera thereby providing a potential organic geochemical measure of past climates these molecular abundance data can be linked to the palaeotemperature record following computer treatments using principal component and spectral analyses molecular stratigraphy shows promise as a new chemostratigraphical tool where other means of stratigraphy fail for example through calcium carbonate dissolution

holocene multidecadal to millennial scale variations in iceland scotland overflow and their relationship to climate the nordic seas overflows are an important part of the atlantic thermohaline circulation while there is growing evidence that the overflow of dense water changed on orbital time scales during the holocene less is known about the variability on shorter time scales beyond the instrumental record here we reconstruct the relative changes in flow strength of iceland scotland overflow water isow the eastern branch of the overflows on multidecadal millennial time scales the reconstruction is based on mean sortable silt ss from a sediment core on the gardar drift 60 19 n 23 58 w 2081 m our ss record reveals that the main variance in isow vigor occurred on millennial time scales 1 2 kyr with particularly prominent fluctuations after 8 kyr superimposed on the millennial variability there were multidecadal centennial flow speed fluctuations during the early holocene 10 9 kyr and one prominent minimum at 0 9 kyr we find a broad agreement between reconstructed isow and regional north atlantic climate where a strong weak isow is generally associated with warm cold climate we further identify the possible contribution of anomalous heat and freshwater forcing respectively related to reconstructed overflow variability we infer that ocean poleward heat transport can explain the relationship between regional climate and isow during the middle to late holocene whereas freshwater input provides a possible explanation for the reduced overflow during early holocene 8 10 kyr

recent distribution and accumulation of organic carbon on the continental margin west off spitsbergen the study compiles the controlling factors for organic matter sedimentation patterns from a suite of organogeochemical parameters in surface sediments off spitsbergen and direct seabed observations using a remotely operated vehicle rov in addition we assess its storage rates as well as the potential of carbon sinks on the northwestern margin of the barents sea with short sediment cores from a selected fjord environment storfjord while sedimentation in the fjords is mainly controlled by river meltwater discharge and coastal erosion by sea ice glaciers resulting in high supply of terrigenous organic matter atlantic water inflow and thus enhanced marine organic matter supply characterizes the environment on the outer shelf and slope local deviations from this pattern particularly on the shelf are due to erosion and out washing of fine grained material by bottom currents spots dominated by marine productivity close to the island have been found at the outer isfjord and west off prins karls forland as well as off the kongsfjord krossfjord area and probably reflect local upwelling of nutrient rich atlantic water derived water masses accumulation rates of marine organic carbon as well as reconstructed primary productivities decreased since the middle of the last century negative correlation of the isfjord temperature record with reconstructed productivities in the storfjord could be explained by a reduced annual duration of the marginal ice zone in the area due to global warming extremely high accumulation rates of marine organic carbon between 5 4 and 17 2 g m 2 yr 1 mark the storfjord area and probably high latitude fjord environments in general as a sink for carbon dioxide

the micromorphology of unconsolidated sediments this paper aims to describe the use of thin sections micromorphology in the sedimentology of unconsolidated sediments it provides examples of the use of thin sections in a variety of sedimentary environments from fault gouge through caves and volcanics to aeolian fluviatile marine periglacial and glacial it demonstrates that in the latter three fields the use of micromorphology is relatively widespread and that in glacial sedimentology it has revolutionised our way of thinking about subglacial sediments although micromorphology has been mainly descriptive so far methods of quantification observations are demonstrated some of the important aspects of micromorphology are its use for microstratigraphy and the possibility of relating observations to documented processes thereby allowing a more robust sedimentological interpretation of modern and ancient sediments

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