an evaluation of lohmann s foraminifera weight dissolution index down water column traverses of core top weights for three planktonic species confirm lohmann s 1995 relationship between foraminifera shell weight loss and bottom water carbonate ion content however they also suggest that the initial shell thickness varies with growth habitat and that the offset between bottom water and pore water carbonate ion concentration varies even on small space scales

mis 3 to mis 1 temporal and lgm spatial variability in arctic ocean sea ice cover reconstruction from biomarkers using the sea ice proxy ip25 and phytoplankton derived biomarkers brassicasterol and dinosterol arctic sea ice conditions were reconstructed for marine isotope stage mis 3 to 1 with special emphasis on the last glacial maximum lgm in sediment cores from the northern barents sea continental margin across the central arctic ocean to the southern mendeleev ridge our results suggest more extensive sea ice cover than present day during latter part of mis 3 increasing sea ice growth during mis 2 and decreased sea ice cover during the last deglacial the summer ice edge remained north of the barents sea even during extremely cold i e last glacial maximum lgm as well as warm periods i e bolling allerod during the lgm the western svalbard margin and the northern barents sea margin areas were characterized by high concentrations of both ip25 and phytoplankton biomarkers interpreted as a productive ice edge situation caused by the inflow of warm atlantic water in contrast the lgm central arctic ocean north of 84 n was covered by thick permanent sea ice throughout the year with rare break up indicated by zero or near zero biomarker concentrations the spring summer sea ice margin significantly extended southwards to the laptev sea shelf southern lomonosov ridge and southern mendeleev ridge during the lgm our proxy reconstructions are very consistent with published model results based on the north atlantic arctic ocean sea ice model naosim

climate and oceanographic variability in the sw barents sea during the holocene the holocene section of the marine sediment core psh 5159n located in the sw barents sea has been studied at high resolution with a multiproxy approach a well stratified water column occurred at the site 11 9 8 ka bp the stratification was probably a result of a winter sea ice cover and or fresh warm surface waters during summer stratification and resultant reduction in air sea interaction allowed for warmer bottom water temperatures the general situation 11 9 8 ka bp could have been associated with an anomalous high pressure system over the nordic seas and the arctic ocean during the 11 10 5 ka bp interval the polar front was located close to the barents sea margin the polar front moved towards the site from 10 5 ka bp and from 9 8 to 7 5 ka bp it was probably located close to the site at 7 5 ka bp the polar front retreated eastwards as the present day oceanographic pattern established the mid holocene was in general characterized by rather stable conditions in contrast highly variable cond

paleoceanography of the barents sea during the holocene 1 we measured the oxygen isotopic composition of planktonic and benthic foraminifera in three cores collected at key positions to reconstruct the paleoceanography of the barents sea core asv 880 on the path of the northern branch of atlantic water inflowing from the arctic ocean core asv 1200 in the central basin near the polar front and core asv 1157 in the main area of brine formation modern seawater 18o measurements show that far from the coast 18o variations are linearly linked to the salinity changes associated with sea ice melting the foraminifer 18o records are dated by 14c measurements performed on mollusk shells and they provide a detailed reconstruction of the paleoceanographic evolution of the barents sea during the holocene four main steps were recognized the terminal phase of the deglaciation with melting of the main glaciers which were located on the surrounding continent and islands the short thermal optimum from 7 8 ka b p to 6 8 ka b p a cold mid holocene phase with a large reduction of the inflow of atlantic water and the inception of the modern hydrological pattern by 4 7 ka b p brine water formation was active during the whole holocene the paleoclimatic evolution of the barents sea was driven by both high latitude summer insolation and the intensity of the atlantic water inflow

evaluation of the sea ice proxy ip25 against observational and diatom proxy data in the sw labrador sea the recent rapid decline in arctic sea ice cover has increased the need to improve the accuracy of the sea ice component in climate models and to provide detailed long term sea ice concentration records which are only available via proxy data recently the highly branched isoprenoid ip25 identified in marine sediments underlying seasonal sea ice has emerged as a potential sea ice specific proxy for past sea ice cover we tested the reliability of this biomarker as a sea ice proxy against observational sea ice data sea ice concentrations from the global hadisst1 database and against a more established sea ice proxy sea ice diatom abundance in sediments in the south west sw labrador sea furthermore our study location at the southern margin of arctic sea ice drift provided a new environmental setting in which to further test the novel pip25 index our two study sites are located north east ne and south east se of newfoundland where box cores covering the last ca 100 150 years were collected ip25 concentrations are nearly an order of magnitude higher and sea ice diatoms more abundant in sediments from ne of newfoundland where sea ice prevails 2 4 months per year compared to the sediments se of newfoundland where conditions are generally ice free year round the ip25 fluxes ne of newfoundland agree well with multi decadal north atlantic oscillation nao trends in the study area which in previous studies have been shown to affect the climatic and sea ice conditions in the region when assessed against observational sea ice data ip25 appears to be a more sensitive indicator of sea ice variability in this setting compared to sea ice diatoms and proved to be a robust and reliable proxy for reconstructing low frequency variability in past sea ice concentrations the pip25 index results clearly differ from the observed sea ice data underlining that caution needs to be exercised when using the index in different environmental settings

tree ring based mass balance estimates for the past 300 years at peyto glacier alberta canada tree rings were used to reconstruct mass balance for peyto glacier in the canadian rocky mountains from a d 1673 to 1994 summer balance was reconstructed from tree ring estimates of summer temperature and precipitation in the canadian rockies winter balance was derived from tree ring data from sites bordering the gulf of alaska and in western british columbia the models for winter and summer balance each explain over 40 of the variance in the appropriate mass balance series over the period 1966 1994 the correlation between the reconstructed and measured net balances is 0 71 strong positive mass balances are reconstructed for 1695 1720 and 1810 1825 when higher winter precipitation coincided with reduced ablation periods of reconstructed positive mass balance precede construction of terminal moraines throughout the canadian rockies ca 1700 1725 and 1825 1850 positive mass balances in the period 1845 1880 also correspond to intervals of glacier readvance mass balances were generally negative between 1760 and 1805 from 1673 to 1883 the mean annual net balance was 70 mm water equivalent per year w e yr but it averaged 317 mm w e yr from 1884 to 1994 this reconstructed mass balance history provides a continuous record of glacier change that appears regionally representative and consistent with moraine and other proxy climate records

late quaternary paleochemistry of high latitude surface waters recent studies have stressed the role of high latitude nutrient levels and productivity in controlling the carbon isotopic composition of the deep sea and the co2 content of the atmosphere we undertook a study of the chemical composition of the polar planktonic foraminifer neogloboquadrina pachyderma s sinistral coiling from 30 late holocene samples and 49 down core records from the high latitude north and south atlantic oceans to evaluate the history of sea surface chemical change from glacial to interglacial time stable isotopic analysis of coretop samples from the atlantic pacific and southern oceans shows no significant correlation between the 13c of n pachyderma and either 13c or po4 in seawater conversely cd ca ratios in planktonic foraminifera are consistent with the po4 content of surface waters the level of maximum glaciation 18 000 yr b p identified by climap and 18o was chosen for mapping isopleths of 18o on n pachyderma s in the north atlantic reveal a pattern largely influenced by sea surface temperature s s t and generally support the s s t reconstruction of climap differences between the two suggest significantly lower salinity in north atlantic surface waters at high latitudes than in lower latitudes down core 13c records of n pachyderma confirm that low 13c values occurred in the northeast atlantic during the latest glacial maximum labeyrie and duplessy 1985 however a map of 13c for the 18 000 yr b p level for a much larger region in the north atlantic shows that minimum n pachyderma 13c occurred in temperate waters n pachyderma 13c decreased toward the southwest reaching a minimum of 1 at 37 n despite the variability seen in 13c records of n pachyderma none of our cores show significant temporal variability in cd ca from the combined cd ca and 13c data we can see no evidence for an upwelling gyre in the eastern north atlantic during the latest glacial maximum nor evidence that the southern and northern oceans had significantly different levels of preformed nutrients than today

oxygen isotope composition of living neogloboquadrina pachyderma sin in the arctic ocean data from the nansen basin of the arctic ocean are used to investigate the habitat and conditions under which the polar planktic foraminifer neogloboquadrina pachyderma sin calcifies the vertical distribution of 18o values of net sampled speciments together with their abundances and proportion of calcification are compared with 18o values from both water samples and foraminiferal tests from core top sediments within the nansen basin the average depth of habitat of n pachyderma sin changes from about 150 m in the southern part to about 80 m in the northern the average depth of calcification however in both regimes varies between 100 and 200 m water depth 18o data from net sampled n pachyderma sin are directly reflected in the core top sediment data but compared to equilibrium calcite 18o values derived from measurements of the ambient water a consistent offset of about 1 over all depth intervals is observed while in the southern part of the nansen basin advection through fram strait of planktic foraminifers from further south may play a role the data from the northern part of the nansen basin give clear evidence that the observed offset in 18o values is caused by a vital effect of n pachyderma sin

carbonate preservation records of the past 3 myr in the norwegian greenland sea and the northern north atlantic implications for the history of nadw production carbonate preservation records from a number of drill sites in the north atlantic and adjacent norwegian greenland sea ngs are used to reconstruct variations in north atlantic deep water nadw production over the past 3 myr before the initiation of major northern hemisphere glaciation good carbonate preservation was recorded in the north atlantic and the ngs supporting the superconveyor model of accelerated nadw formation in the late pliocene after the inception of main northern hemisphere glaciation nadw formation in the ngs was blocked off during the period 2 8 1 9 ma carbonate was only badly preserved due to 1 low production of carbonate shells in surface waters 2 sluggish renewal of deep waters induced by a rather stable sea ice cover and or 3 production of carbonate corrosive dense brines during sea ice formation e g sea ice dissolution mode in contrast contemporaneous good preservation in the adjacent north atlantic indicates efficient nadw production during the middle matuyama 1 9 1 4 ma the first intrusions of the proto norwegian current into a narrow corridor in the southeastern ngs are evidenced by much better carbonate preservation a decrease both in carbonate content and preservation towards the north and west of this corridor indicates the proximity of the polar front and gives evidence that nadw production was efficiently triggered by the atlantic water entrainment mode during the past 1 2 myr carbonate preservation patterns in the ngs clearly reflect major global events like the mid pleistocene transition and the mid brunhes dissolution event the onset of the mid pleistocene transition at 1 2 ma is characterized by a complete shift to higher carbonate contents in the southeastern ngs and labrador sea overall good preservation during both interglacials and glacials is only interrupted by high frequency short term dissolution spikes which were induced by ice sheet collapse and development of extensive meltwater lids as a consequence nadw was produced nearly continuously during glacials in the nordic seas however due to its lower density it was entrained into intermediate water levels in the north atlantic and thus enforced the intermediate water circulation loop whereas a decrease in lower nadw production is observed contemporaneously

identification of contrasting seasonal sea ice conditions during the younger dryas abstract a palaeo sea ice reconstruction for northern norway for the interval ca 13 8 7 2 cal ka bp has been performed using a combined organic geochemical proxy based study of a marine sediment core jm99 1200 obtained from andfjorden 69 15 95 n 16 25 09 e and the outcomes compared with a series of other palaeoclimate studies carried out previously within this study particular emphasis has been placed on the identification of the sea ice conditions during the younger dryas and the application of different biomarker based proxies to both identify and quantify seasonal sea ice conditions firstly the appearance of the specific sea ice diatom proxy ip 25 at ca 12 9 cal ka bp in the sedimentary record has provided an unambiguous but qualitative measure of seasonal sea ice and thus the onset of the younger dryas stadial the near continuous occurrence of ip 25 for the next ca 1400 yr demonstrates seasonal sea ice during this interval although variable abundances suggest that the recurrent conditions in the early mid younger dryas ca 12 9 11 9 cal ka bp changed significantly from stable to highly variable sea ice conditions at ca 11 9 cal ka bp and this instability in sea ice prevailed for the subsequent ca 400 yr during which an extremely short interval of permanent or near permanent sea ice was observed at ca 11 75 cal ka bp at ca 11 5 cal ka bp ip 25 disappeared from the record indicating ice free conditions that signified the beginning of the holocene the ip 25 concentrations were also combined with those of the open water phytoplankton biomarker brassicasterol to generate p b ip 25 data from which more quantitative measurements of sea ice were determined p b ip 25 data were consistent with consecutively seasonal then infrequent sea ice cover for the early mid and late younger dryas while further comparisons of the p b ip 25 data with the outcomes of previous correlations with modelled sea ice concentrations suggested that these intervals were characterised by ca 60 90 and ca 0 60 sea ice cover respectively both qualitative and quantitative sea ice records were also consistent with sea surface temperature and other palaeoclimate estimates derived previously from various other proxy studies the contrasting seasonal sea ice conditions during the younger dryas were further verified through a comparison of the concentrations of ip 25 with those of another highly branched isoprenoid hbi alkene that is di unsaturated and believed to also be produced by sea ice diatoms the ratio of the hbi diene to ip 25 termed dip 25 is believed to provide a useful indicator of stability or variability in sea ice conditions and complements the outcomes from the ip 25 and p b ip 25 index data the identification of contrasting seasonal sea ice conditions during the younger dryas will likely contribute to the debate regarding the climatic impacts that took place during this intriguing interval

dynamics of the wind driven sea level variation around antarctica coastal sea level variation around antarctica is characterized by a coherent circumpolarly in phase fluctuation correlated with the antarctic oscillation aao this study addresses the dynamics of the winddriven sea level variation around antarctica a realistic barotropic numerical model reproduced well the observed sea level around antarctica from numerical model experiments the authors demonstrate that the forcing responsible for the coastal sea level is the wind stress at the coastal boundary both the dominant coherent signal and westward propagating signals are identified in the model and these signals are trapped over the shelf and slope around antarctica as a mechanism of these trapped signals the authors consider analytical solutions of the oceanic response to alongshore wind stress over the shelf and slope in the circumpolar domain in these solutions besides the shelf wave mode a wavenumber zero mode appears and characterizes the coastal dynamics around antarctica at periods from 10 to 200 days the coherent sea level can be explained quantitatively by the solution of this wavenumber zero mode with a 5 10 day damping time scale the spectral peaks of the westward propagating signals can be explained by the resonance of the shelf wave mode the wavenumber zero mode can respond to the wavenumber zero forcing at any frequency and the degree of response increases with decreasing frequency in addition the wavenumber zero component of wind stress corresponding to the aao variation is a dominant forcing therefore the coherent sea level variation around antarctica is preferably generated and becomes a dominant feature in the circumpolar domain particularly at lower frequencies

a high resolution reconstruction of storglaciaren mass balance back to 1780 81 using tree ring data and circulation indices storglaciaren in northernmost sweden has the world s longest ongoing continuous mass balance record starting in 1946 to extend this massbalance record we have reconstructed summer bs and winter bw mass balances separately back to the mass balance year 1780 81 with annual resolution we used tree ring data for bs and a set of circulation indices based on the sea level pressure for bw both proxies have correlation coefficients with respective mass balance components of ca 0 7 the reconstructed net balance bn of storglaciaren was well correlated to the observations during 1946 1980 r 0 8 p 0 05 our reconstruction agrees well with previously obtained results of northern sweden glacier variability where the predominantly positive bn years between 1890 and 1910 correspond to the well documented post little ice age advance of storglaciaren furthermore the results suggest that bs as a function of summer temperatures is more important than bw in determining the bn which is contrary to glaciers in the maritime parts of western scandinavia in general bn has been negative over the last 220 yr suggesting a predomination of continental conditions over northern sweden however the influence of bw increased in the late twentieth century indicating a shift to a more oceanic climate regime

improving a tree ring reconstruction from west central scandinavia 900 years of warm season temperatures dendroclimatological sampling of scots pine pinus sylvestris l has been made in the province of jamtland in the west central scandinavian mountains since the 1970s the tree ring width trw chronology spans several thousand years and has been used to reconstruct june august temperatures back to 1632 bc a maximum latewood density mxd dataset covering the period ad 1107 1827 with gap 1292 1315 was presented in the 1980s by fritz schweingruber here we combine these historical mxd data with recently collected mxd data covering ad 1292 2006 into a single reconstruction of april september temperatures for the period ad 1107 2006 regional curve standardization rcs provides more low frequency variability than non rcs and stronger correlation with local seasonal temperatures 51 variance explained the mxd chronology shows a stronger relationship with temperatures than the trw data but the two chronologies show similar multi decadal variations back to ad 1500 according to the mxd chronology the period since ad 1930 and around ad 1150 1200 were the warmest during the last 900 years due to large uncertainties in the early part of the combined mxd chronology it is not possible to conclude which period was the warmest more sampling of trees growing near the tree line is needed to further improve the mxd chronology

sea ice variations in the central canadian arctic archipelago during the holocene abstract a sea ice record for barrow strait in the canadian arctic archipelago caa is presented for the interval 10 0 0 4 cal kyr bp this holocene record is based primarily on the occurrence of a sea ice biomarker chemical ip25 isolated from a marine sediment core obtained from barrow strait in 2005 a core chronology is based on 14c ams dating of mollusc shells obtained from ten horizons within the core the primary ip25 data are compared with complementary proxy data obtained from analysis of other organic biomarkers stable isotope composition of bulk organic matter benthic foraminifera particle size distributions and ratios of inorganic elements the combined proxy data show that the palaeo sea ice record can be grouped according to four intervals and these can be contextualised further with respect to the holocene thermal maximum htm spring sea ice occurrence was lowest during the early mid holocene 10 0 6 0 cal kyr bp and this was followed by a second phase 6 0 4 0 cal kyr bp where spring sea ice occurrence showed a small increase between 4 0 and 3 0 cal kyr bp spring sea ice occurrence increased abruptly to above the median and we associate this interval with the termination of the htm elevated spring sea ice occurrences continued from 3 0 to 0 4 cal kyr bp although they were more variable on shorter timescales within this fourth interval we also provide evidence for slightly lower and subsequently higher spring sea ice occurrence during the mediaeval warm period and the little ice age respectively comparisons are made between our proxy data with those obtained from other palaeo climate and sea ice studies for the caa

semi quantitative reconstruction of early to late holocene spring and summer sea ice conditions in the northern barents sea semi quantitative estimates of early to late holocene spring sea ice concentration spsic and occurrence of summer sea ice for the northern barents sea have been obtained by analysing the biomarkers ip25 brassicasterol and a tri unsaturated highly branched isoprenoid lipid in a holocene marine sediment core sub surface water mass variations were derived from planktic foraminiferal assemblages and stable isotopes 18o 13c the record indicates paleoceanographic changes over three intervals during period i ca 9500 5900 cal a bp the study location experienced the lowest recorded spsic ca 25 with short spring seasons and long productive summers resulting partly from increased atlantic water inflow that caused a stronger ocean atmosphere heat exchange throughout period ii ca 5900 2700 cal a bp the winter sea ice margin migrated southwards and an overall cooling trend resulted in higher spsic ca 60 and increased delivery of cold arctic water during period iii ca 2700 cal a bp to present spsic increased further ca 75 and some sea ice remained during summer months a sub surface warming probably indicates a decoupling of heat exchange between the ocean and the atmosphere longer springs and shorter summers were accompanied by the most southerly location of the winter sea ice margin

weakening climatic signal since mid 20th century in european larch tree ring chronologies at different altitudes from the adamello presanella massif italian alps abstract tree rings from temperature limited environments are highly sensitive climate proxies widely used to reconstruct past climate parameters for periods prior to the availability of instrumental data and to analyse the effect of recent global warming on tree growth an analysis of the climatic signal in five high elevation tree ring width chronologies of european larch larix decidua mill from the tops of five different glacial valleys in the italian central alps revealed that they contain a strong summer temperature signal and that tree ring growth is especially influenced by june temperatures however a moving correlation function analysis revealed a recent loss of the june temperature signal in the tree ring chronologies this signal reduction primarily involves the two lowest altitude chronologies it is probable that the observed increasing importance of late summer temperature for tree ring growth over the past 50 yr is an effect of the lengthening growing season and of the variations in the climate tree ring relationship over time all the chronologies considered especially those at the highest altitudes show an increasing negative influence of june precipitation on tree ring growth the climatic signal recorded in tree ring chronologies from the italian central alps varies over time and is also differentially influenced by climatic parameters according to site elevation

marine 14c reservoir ages for 19th century whales and molluscs from the north atlantic abstract in order to compare radiocarbon dates on marine and terrestrial samples the former have to be corrected for a reservoir age we present reservoir ages from dating 21 whales collected 1860 1901 and recalculating dates of 23 molluscs collected 1857 1926 most of the whales were caught along the coast of norway but one is from france and one from iceland we assume the former mainly lived in the north and equatorial atlantic and in the norwegian sea whales feed only on pelagic organisms and will provide the reservoir age for the open ocean surface water however they travel long distances and will integrate the reservoir ages of the different water masses along their way molluscs dated from norway spitsbergen and arctic canada are stationary and monitor the sea water passing their dwelling site but some also take up carbon from particulate food or sediment pore water coastal water also often contains some continental carbon we present two different views on how to analyze and interpret the data mangerud recommends to use reservoir ages based on a combination of the whale and mollusc dates i e 380 30 and 360 30 yr relative to intcal04 and british oak respectively and a r value of 20 30 for the surface water in the n atlantic and norwegian sea bondevik and gulliksen maintain that the reservoir age and r along the norwegian coast is latitude dependant with r values increasing from 3 22 in the south to 105 24 at spitsbergen whales reflecting north atlantic open ocean surface water have lower r 7 11 than most molluscs

carbon isotope composition of tropical surface water during the past 22 000 years carbon isotope values of many species of planktonic foraminifera are size dependant values of 13c of individual size fractions are therefore an integration of low 13c values of calcite precipitated in the juvenile growth stage and high values precipitated in later stages in general the selection of a particular size fraction for downcore studies has been subjective analysis of different size fractions of planktonic foraminifera however yields different time series in downcore studies by measuring the 13c of many size fractions the 13c precipitated throughout the growth of the foraminifera can be calculated time series of the 13c of calcite precipitated in the late growth stages of planktonic foraminifera from two nearby cores from the caribbean sea result in a better correlation than time series of constant size fractions these 13c records indicate similar 13c values during the last glaciation and the late holocene and a broad deglacial minimum approximately synchronous with a minimum in the 13c records of benthic foraminifera from intermediate depth atlantic cores the deglacial minimum may be a reflection of the isotopic composition of the underlying intermediate water which may be affected by circulation changes or changes in preformed 13c values and or of the flux of water upwelled into the surface layer the small 0 2 to 0 0 glacial interglacial 13c difference in tropical surface water is also believed to be affected by the chemistry of the underlying source water

branching of atlantic water within the greenland spitsbergen passage an estimate of recirculation atlantic water aw supplies the largest source of heat mass and salt to the arctic ocean via fram strait greenland spitsbergen passage yet it represents only a fraction of the atlantic water that resides in the greenland iceland norwegian and barents seas this is a result of both the branching of the central core of aw along its northward flow and the modification of its t s signature through air sea ice interactions and internal mixing this paper addresses the quantitative analysis of the three dominant atlantic water cores within fram strait and north of 76 n using an 11 year 1977 to 1987 hydrographic database spatial variations of heat volume and salt along its flow path of some 600 km showed that the major core of atlantic water that directly enters the arctic ocean svalbard branch did not extend past 20 e of the 9719 km3 of atlantic water existing within the region one third resided within the svalbard branch the remainder 22 and 45 were held within the return atlantic current and the yermak branches respectively restricting the analysis to a southern limit of 79 n effectively removed the return atlantic current and showed a nearly equal split between the two remaining branches work completed by bourke et al 1988 indicated that the yermak branch is largely recirculated to the south if true this analysis supports rudels 1987 model estimate of a 50 recirculation of aw within this region

the gin sea a synthesis of its physical oceanography and literature review 1972 1985 abstract a synthesis and review of the physical oceanography of the gin sea greenland iceland and norwegian seas is presented an accompanying bibliography is included from 1972 through 1985 some 1986 works are also noted emphasis is placed on describing the gin sea as a major semi enclosed basin that plays a role unique among the world s oceans by providing a strong two way advective exchange between the ice covered polar sea and the north atlantic ocean and at the same time acting as the primary site for northern hemisphere bottom water formation the water masses for the gin sea are defined in a manner as consistent as possible with the literature the large scale oceanographic and meteorological factors influencing the water mass formation and circulation are described a sample calculation of the various horizontal and vertical thermohaline driven exchanges is given

the arctic sea ice biomarker ip25 a review of current understanding recommendations for future research and applications in palaeo sea ice reconstructions in recent years a novel proxy for the past occurrence of arctic sea ice has been proposed that is based on the variable marine sedimentary abundance of an organic geochemical lipid derived from sea ice diatoms in the spring this lipid termed ip25 ice proxy with 25 carbon atoms is a highly branched isoprenoid mono unsaturated alkene that appears to be sufficiently stable in sediments to permit meaningful palaeo sea ice reconstructions to be carried out over short to long term timescales since the first proposed use of ip25 as a proxy for palaeo sea ice by belt et al 2007 a number of laboratories have measured this biomarker in arctic sediments and it is anticipated that research activity in this area will increase further in the future the content of this review is divided into a number of sections firstly we describe the scientific basis for the ip25 proxy and its initial discovery in arctic sea ice sedimenting particles and sediments secondly we summarise the relatively few studies that have to date concentrated on examining the factors that influence the production and fate of ip25 and we identify some areas of future research that need to be addressed in order to improve our understanding of ip25 data obtained from sedimentary analyses what is clear at this stage however it that the presence of ip25 in arctic marine sediments appears to represent a proxy measure of past seasonal sea ice rather than permanent or multi year ice conditions thirdly we highlight the importance of rigorous analytical identification and quantification of ip25 especially if measurements of this biomarker are going to be used for quantitative sea ice reconstructions rather than qualitative analyses alone presence absence fourthly we review some recent attempts to make the interpretations of ip25 biomarker data more detailed and quantitative by combining sedimentary abundances with those of phytoplankton and other sea ice derived biomarkers thus the bases for the so called pip25 and dip25 indices are described together with an overview of potential limitations concluding that investigations into the use of these indices needs further research before their full potential can be realised in the final section we provide a summary of ip25 based palaeo sea ice reconstruction case studies performed to date these case studies cover different arctic regions and timescales spanning decades to tens of thousands of years

stable oxygen and carbon isotopes in planktic foraminifers from arctic ocean surface sediments reflection of the low salinity surface water layer planktic foraminifers neogloboquadrina pachyderma sin from 87 eastern and central arctic ocean surface sediment samples were analyzed for stable oxygen and carbon isotope composition additional results from 52 stations were taken from the literature the lateral distribution of 18o full size image 33 atlantic waters entering the arctic ocean through the fram strait 18o values decrease both to the barents shelf and to the north pole in accordance with the decreasing salinities of the halocline waters in the nansen basin a strong n s 18o gradient is in contrast with a relatively low salinity change and suggests contributions from different freshwater sources i e salinity reduction from sea ice meltwater in the south and from light isotope waters meteoric precipitation and river runoff in the northern part of the basin north of the gakkel ridge 18o and salinity gradients are in good accordance and suggest less influence of sea ice melting processes the 13c full size image 1 k values of n pachyderma sin from arctic ocean surface sediment samples are generally high 0 75 0 95 lower values in the southern eurasian basin appear to be related to the intrusion of atlantic waters the high 13c values are evidence for well ventilated surface waters because the perennial arctic sea ice cover largely prevents atmosphere ocean gas exchange ventilation on the seasonally open shelves must be of major importance lack of 13c gradients along the main routes of the ice drift from the siberian shelves to the fram strait suggests that primary production i e co2 consumption does probably not change the co2 budget of the arctic ocean significantly

paleoceanography of the last interglacial glacial cycle in the polar north atlantic abstract using to its position close to the sites of waxing and waning of the major northern hemisphere ice sheets during the late quaternary climatic cycles the polar north atlantic plays a key role in driving global change therefore analyzing the present day sedimentation processes and reconstructing the late quaternary paleoceanography in this region has been a focus of major scientific interest through the last fifteen years this paper aims to combine the vast amount of new results about modern sediment fluxes surface sediment distribution and the paleoceanographic record and to present a comprehensive overview of the paleoceanography in the polar north atlantic through the last 200 000 years which is based on the basinwide analysis of carbonate and ice rafted detritus records during the last fifteen years the climap paleoceanographic view of the glacial polar north atlantic as an almost permanently isolated sea covered by heavy sea ice throughout the year has been shifted to a much more dynamic view of the environmental conditions a meridional current system similar to the present day conditions secured the exchange of water ice and heat between the polar north atlantic and the alantic and arctic oceans although affected by variations in strength and intensity this meridional current pattern resulted in an almost permanent presence of at least some seasonally ice free areas with all the consequences for e g marine life and deep water formation in addition the development of the continental ice sheets namely the fennoscandian and the barents sea ice sheets is closely related to this dynamic circulation pattern during the so called nordway events the pronounced inflow of temperate waters from the south provided moisture for the growth of the ice sheets the most prominent of these events stage 6 stage 4 and substage 3 1 2 ended in major glaciations reflected in the terrestrial sequences and in the deep sea ird records

marine calcium carbonate preservation vs climate change over the last two millennia in the fram strait implications for planktic foraminiferal paleostudies abstract we present a high resolution study of planktic foraminiferal distribution patterns in a deep sea core from the eastern fram strait position 78 55 n 06 46 e water depth 1497 m the sediment core is located below atlantic water masses flowing into the arctic ocean and spans the last 2400 years the investigation is based on planktic foraminiferal species distribution stable isotopes and sedimentological data the mean shell weight of neogloboquadrina pachyderma fragmentation organic and inorganic carbon content and the presence of benthic organic linings were also investigated as an indication of preservation changes the results indicate that the planktic foraminifera are affected by dissolution and point to five periods of especially poor preservation at 200 bce 300 650 ce 700 850 ce 1400 1500 ce and from 1800 ce to present in the last century small and fragile subpolar species turborotalita quinqueloba and globigerinita uvula are preserved the increased percentage of these subpolar species together with increases in the caco 3 toc and total foraminiferal flux would point to surface water warming however our data suggest that these fragile species may not have been preserved in sediments older than 1900 ce due to selective dissolution consequently the magnitude of the previously recorded recent surface water warming in the fram strait may be overestimated

recent calcium carbonate dissolution in the barents sea paleoceanographic applications abstract studies of benthic foraminifera in surface sediments of the arctic epicontinental barents sea show several indications of calcium carbonate dissolution low values of calcium carbonate correspond to low ratios of calcareous agglutinating foraminifera planktic benthic foraminifera high ratios of living dead foraminifera corroded calcareous foraminifera and high numbers of exposed organic linings of foraminifera dissolution increases eastwards and northwards in the study area we suggest that the dissolution is caused by the presence of dense cold saline and co 2 rich bottom water which is linked to sea ice production and the position of the oceanic polar front we also think calcium carbonate dissolution in this area indicates a sink for atmospheric co 2

paired δ18o signals of neogloboquadrina pachyderma s and turborotalita quinqueloba show thermal stratification structure in nordic seas abstract the vertical density gradients in the nordic seas are crucial for the preconditioning of the surface water to thermohaline sinking in winter these gradients can be reconstructed from paired oxygen isotope data in tests of different species of planktonic foraminifera the isotopic signatures of which represent different calcification depths in the water column comparison of 18 o values from foraminiferal tests in plankton hauls sediment traps and nearby core top samples with the calculated 18 o calcite profile of the water column revealed species specific 18 o vital effects and the role of bioturbational admixture of subfossil specimens into the surface sediment on the basis of core top samples obtained along a west east transect across various hydrographic regions of the nordic seas 18 o values of turborotalita quinqueloba document apparent calcification depths within the pycnocline at 25 75 m water depth the isotopic signatures of neogloboquadrina pachyderma s reflect water masses near and well below the pycnocline between 70 and 250 m off norway where the atlantic inflow leads to thermal stratification here temperatures in the calcification depth of n pachyderma s differ from sea surface temperature by approximately 2 5 c in contrast n pachyderma s calcifies very close to the sea surface 20 50 m in the arctic domain of the western nordic seas however further west n pachyderma s prefers somewhat deeper more saline water at 70 130 m well below the halocline that confines the low saline east greenland current this implies that the 18 o values of n pachyderma s do not fully reflect the freshwater proportion in surface water and that any reconstruction of past meltwater plumes based on 18 o is too conservative because it overestimates sea surface salinity minimum 18 o differences n pachyderma s and t quinqueloba may serve as proxy for sea regions with dominant haline and absent thermal stratification whereas thermal stratification leads to 18 o differences of 0 4 to 1 5

quantifying carbonate dissolution and calibration of foraminiferal dissolution indices in the somali basin two sediment traps moored off somalia in 1992 1993 collected similar settling fluxes of carbonate and siliceous shells formed by various plankton groups planktic foraminifera showed large seasonal variations with more than 74 of the total planktic foraminifera flux collected during the sw monsoon summer upwelling when globigerina bulloides was dominating along with globigerinita glutinata and neogloboquadrina dutertrei the intermonsoon and ne monsoon assemblages were dominated by globigerinoides ruber we used the trap records as our no dissolution reference for comparison with three boxcore recorders in order to quantify the carbonate dissolution along a depth transect dissolution increases downslope from station 905 to 907 and 915 at depths of 1567 m 2807 m and 4035 m respectively the carbonate fraction of the sediment at station 915 which is located near the ccd is the most affected by dissolution with more than 97 of the planktic foraminifera dissolved here the planktic foraminifera assemblage is strongly modified with thick walled species such as n dutertrei globorotalia tumida and pulleniatina obliquiloculata as the most resistant it is not representative of the settling assemblage the planktic foraminiferal assemblages of the sediment surface at stations 905 and 907 remain similar to the trap assemblages and the foraminifera are well preserved although only 25 of foraminifera are apparently preserved at station 905 and 8 at station 907 those numbers are surprisingly low and infer that only a small fraction of the foraminiferal carbonate production is buried and removed from the carbon cycle this discrepancy between the export and buried flux is partly be due to bio mechanical destruction by benthic processes and to supralysoclinal dissolution due to metabolic co2 generated by the benthic organisms another important factor is the interannual variability of the productivity well known in the arabian sea the calibration of commonly used foraminiferal dissolution indices percentage of foraminiferal fragments percentage of resistant species foraminiferal dissolution index fdx to our data only shows reliable results for high dissolution levels 97 off somalia the most accurate of the proxies is the percentage of foraminiferal fragments compared to the other methods tested i e fdx planktic foraminiferal loss l percentage of radiolarians and diatoms percentage of benthic foraminifera the species assemblage appears to be not significantly modified by dissolution unless the estimated shell loss is high 92 of the arriving shells in our samples this level is expressed in the percentage of fragmentation the percentage of radiolarians and diatoms the percentage of resistant foraminifera species and fdx as 80 35 25 and 1 8 respectively the relative abundance of globigerina bulloides is a valid sw monsoon upwelling proxy only when dissolution is moderate 92 globigerina bulloides and globigerinoides ruber have similar burial efficiencies and susceptibilities to dissolution thus the ratio g bulloides g ruber is a valid proxy for past changes in the intensity of the sw monsoon even in the strongly dissolved samples in our sediment record the ratio g bulloides g ruber indicates that the sw monsoon was stronger in the recent past than in 1992 93

distribution of planktic foraminifera at the ice margin in the arctic fram strait planktic foraminifera were collected in net tows 63 m along two east west transects at 78 and 80 n in the fram strait northern nordic seas at five concurrent depth intervals in the upper 200 m of the water column in the ice free zone absolute abundances in the upper 200 m of the water column up to 500 individuals m3 were obtained along the ice margin the absolute abundances reached up to 1250 ind m3 while in the ice covered areas not more than 50 ind m3 have been found surprisingly these strong variations in abundance are not accompanied by significant changes in faunal assemblages between the ice free and the ice covered regions neogloboquadrina pachyderma is the dominant species in most samples making up to 60 of the total faunal assemblage globigerina quinqueloba contributes 38 and all other species combined make up only 2 of the total fauna both absolute and relative abundances of the collected foraminifera are strongly dependent on the mesh size used using smaller mesh sizes provides a wider species spectrum which is of special interest for paleoceanographic reconstructions in the nordic seas where fossil assemblages 150 m often consist of only one species the specific hydrographic conditions in the fram strait with warm atlantic waters underlying cold polar surface waters result in a rather atypical depth distribution of the planktic foraminifera all species seem to prefer the temperate atlantic waters between 50 m and 200 m thus the species composition as well as geochemical tracers do not reflect the surface ocean conditions which again has potentially interesting implications for paleoceanographic reconstructions

new long term mass balance series for the swiss alps in this study we present 19 new or re analysed series of glacier wide seasonal mass balance for the swiss alps based on direct measurements the records partly start around 1920 and continue until today previously unpublished and unevaluated observations of point winter and annual balance are compiled from various sources and archives these highly valuable datasets have not yet been consistently evaluated and were thus unavailable to the scientific community using distributed modelling for spatial interpolation and extrapolation and homogenization of the point measurements we infer continuous series of area averaged mass balance the results are validated against independent decadal ice volume changes from photogrammetric surveys six of the new seasonal series cover 60 years and more and add a substantial amount of information on the variations of regional glacier mass change this will strengthen the worldwide collection of glacier monitoring data especially for the data sparse period before the 1980s we compare our results to existing long term series and present an updated assessment of mass balance variability and glacier sensitivity throughout the european alps

identification of paleo arctic winter sea ice limits and the marginal ice zone optimised biomarker based reconstructions of late quaternary arctic sea ice abstract analysis of 100 surface sediments from across the barents sea has shown that the relative abundances of the mono unsaturated sea ice diatom derived biomarker ip 25 and a tri unsaturated highly branched isoprenoid hbi lipid hbi iii are characteristic of the overlying surface oceanographic conditions most notably the location of the seasonal sea ice edge thus while ip 25 is generally limited to locations experiencing seasonal sea ice with higher abundances found for locations with longer periods of ice cover hbi iii is found in sediments from all sampling locations but is significantly enhanced in sediments within the vicinity of the retreating sea ice edge or marginal ice zone miz the response of hbi iii to this well defined sea ice scenario also appears to be more selective than that of the more generic phytoplankton biomarker brassicasterol the potential for the combined analysis of ip 25 and hbi iii to provide more detailed assessments of past sea ice conditions than ip 25 alone has been investigated by quantifying both biomarkers in three marine downcore records from locations with contrasting modern sea ice settings for sediment cores from the western barents sea intermittent seasonal sea ice and the northern norwegian sea ice free high ip 25 and low hbi iii during the younger dryas ca 12 9 11 9 cal kyr bp is consistent with extensive sea cover with relatively short periods of ice free conditions resulting from late summer retreat towards the end of the yd ca 11 9 11 5 cal kyr bp a general amelioration of conditions resulted in a near winter maximum ice edge scenario for both locations although this was somewhat variable and the eventual transition to predominantly ice free conditions was later for the western barents sea site ca 9 9 cal kyr bp compared to nw norway ca 11 5 cal kyr bp for both locations coeval elevated hbi iii but absent ip 25 potentially provides further evidence for increased atlantic water inflow during the early holocene but this interpretation requires further investigation in contrast ip 25 and hbi iii data obtained from a core from the northern barents sea demonstrate that seasonal sea ice prevailed throughout the holocene but with a gradual shift from winter ice edge conditions during the early holocene to more sustained ice cover in the neoglacial a directional shift that has undergone a reverse in the last ca 150 yr according to observational records our combined surface and downcore datasets suggest that combined analysis of ip 25 and hbi iii can provide information on temporal variations in the position of the maximum winter arctic sea ice extent together with insights into sea ice seasonality by characterisation of the miz combining ip 25 with hbi iii in the form of the previously proposed pip 25 index yields similar outcomes to those obtained using brassicasterol as the phytoplankton marker importantly however some problems associated with use of a variable balance factor employed in the pip 25 calculation are potentially alleviated using hbi iii

on large outflows of arctic sea ice into the barents sea 1 winter outflows of arctic sea ice into the barents sea are estimated using a 10 year record of satellite ice motion and thickness the mean winter volume export through the svalbard franz josef land passage is 40 km3 and ranges from 280 km3 to 340 km3 a large outflow in 2003 is preconditioned by an unusually high concentration of thick perennial ice over the nansen basin at the end of the 2002 summer with a deep atmospheric low situated over the eastern barents sea in winter the result is an increased export of arctic ice the oct mar ice area flux at 110 103 km2 is not only unusual in magnitude but also remarkable in that 70 of the area is multiyear ice the ice volume flux at 340 km3 is almost one fifth of the ice flux through the fram strait another large outflow of arctic sea ice through this passage comparable to that in 2003 is found in 1996 this southward flux of sea ice represents one of two major sources of freshwater in the barents sea the other is the eastward flux of water via the norwegian coastal current the possible consequences of variable freshwater input on the barents sea hydrography and its impact on transformation of atlantic water en route to the arctic ocean are examined with a 25 year coupled ice ocean model

last millennium northern hemisphere summer temperatures from tree rings part i the long term context abstract large scale millennial length northern hemisphere nh temperature reconstructions have been progressively improved over the last 20 years as new datasets have been developed this paper and its companion part ii anchukaitis et al in prep details the latest tree ring tr based nh land air temperature reconstruction from a temporal and spatial perspective this work is the first product of a consortium called n trend n orthern hemisphere tre e ring n etwork d evelopment which brings together dendroclimatologists to identify a collective strategy for improving large scale summer temperature reconstructions the new reconstruction n trend2015 utilises 54 records a significant expansion compared with previous tr studies and yields an improved reconstruction with stronger statistical calibration metrics n trend2015 is relatively insensitive to the compositing method and spatial weighting used and validation metrics indicate that the new record portrays reasonable coherence with large scale summer temperatures and is robust at all time scales from 918 to 2004 where at least 3 tr records exist from each major continental mass n trend2015 indicates a longer and warmer medieval period 900 1170 than portrayed by previous tr nh reconstructions and by the cmip5 model ensemble but with better overall agreement between records for the last 600 years future dendroclimatic projects should focus on developing new long records from data sparse regions such as north america and eastern eurasia as well as ensuring the measurement of parameters related to latewood density to complement ring width records which can improve local based calibration substantially

mapping recent sea ice conditions in the barents sea using the proxy biomarker ip25 implications for palaeo sea ice reconstructions abstract an analysis of the sea ice proxy ip 25 and the open water phytoplankton indicator brassicasterol has been carried out for 93 surface sediments collected from the barents sea and some additional data from previous studies have been included to augment the analysis further consistent with a specific and selective sea ice diatom origin for ip 25 this biomarker was identified in virtually all sediments from seasonally ice covered locations but was absent from the majority of sites beyond the maximum sea ice extent msie for the period 1983 2002 in contrast brassicasterol was detected in virtually all sediments from the region and concentrations were not at all associated with the msie instead more localised regions of brassicasterol concentrations were identified and these likely reflect different influences on production and deposition when the ip 25 and brassicasterol concentrations were combined together in the form of the previously proposed p b ip 25 index the aforementioned association between ip 25 occurrence and the msie was clarified further and in addition provided more detailed descriptions of sea ice cover in particular p b ip 25 data indicated seasonal sea ice or marginal ice zone conditions for the region of the barents sea within the msie according to previously defined p b ip 25 ranges we also amalgamated the biomarker data from the current study with those derived previously by muller et al 2011 and compared these larger datasets with satellite derived mean spring sea ice concentrations significantly although the correlation between the combined ip 25 concentration dataset with the satellite data was very similar to that reported previously by muller et al 2011 the corresponding correlation using the p b ip 25 values was poorer with the larger dataset and some possible reasons for this are discussed finally in a small number of cases ip 25 was identified in sediments somewhat distal from the msie and it is hypothesised that the occurrence of ip 25 in these sediments results from allochthonous input following sediment advection between shelf and trough environments this is the first reported example that provides evidence for the allochthonous input of ip 25 into marine sediments and it is recommended that this should be considered carefully when carrying out palaeo sea ice reconstructions based on the occurrence of this biomarker in the future

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

latest pleistocene and holocene glacier variations in the european alps in the alps climatic conditions reflected in glacier and rock glacier activity in the earliest holocene show a strong affinity to conditions in the latest pleistocene younger dryas glacier advances in the alps related to younger dryas cooling led to the deposition of egesen stadial moraines egesen stadial moraines can be divided into three or in some cases even more phases sub stadials moraines of the earliest and most extended advance the egesen maximum stabilized at 12 2 1 0 ka based on 10be exposure dating at the schonferwall tyrol austria and the julier pass outer moraine switzerland final stabilization of moraines at the end of the egesen stadial was at 11 3 0 9 ka as shown by 10be data from four sites across the alps from west to east the sites are piano del praiet northwestern italy grosser aletschgletscher central switzerland julier pass inner moraine eastern switzerland and val viola northeastern italy there is excellent agreement of the 10be ages from the four sites in the earliest holocene glaciers in the northernmost mountain ranges advanced at around 10 8 1 1 ka as shown by 10be data from the kartell site northern tyrol austria in more sheltered drier regions rock glacier activity dominated as shown for example at julier pass and larstig valley tyrol austria new 10be dates presented here for two rock glaciers in larstig valley indicate final stabilization no later than 10 5 0 8 ka based on this data we conclude the earliest holocene between 11 6 and about 10 5 ka was still strongly affected by the cold climatic conditions of the younger dryas and the preboreal oscillation with the intervening warming phase having had the effect of rapid downwasting of egesen glaciers at or slightly before 10 5 ka rapid shrinkage of glaciers to a size smaller than their late 20th century size reflects markedly warmer and possibly also drier climate between about 10 5 ka and 3 3 ka conditions in the alps were not conducive to significant glacier expansion except possibly during rare brief intervals past tree line data from kaunertal tyrol austria in concert with radiocarbon and dendrochronologically dated wood fragments found recently in the glacier forefields in both the swiss and austrian alps points to long periods during the holocene when glaciers were smaller than they were during the late 20th century equilibrium line altitudes ela were about 200 m higher than they are today and about 300 m higher in comparison to little ice age lia elas the larstig rock glacier site we dated with 10be is the type area for a postulated mid holocene cold period called the larstig oscillation presumed age about 7 0 ka our data point to final stabilization of those rock glaciers in the earliest holocene and not in the middle holocene the combined data indicate there was no time window in the middle holocene long enough for rock glaciers of the size and at the elevation of the larstig site to have formed during the short infrequent cold oscillations between 10 5 and 3 3 ka small glaciers less than several km2 may have advanced to close to their lia dimensions overall the cold periods were just too short for large glaciers to advance after 3 3 ka climate conditions became generally colder and warm periods were brief and less frequent large glaciers for example grosser aletschgletscher advanced markedly at 3 0 2 6 ka around 600 ad and during the lia glaciers in the alps attained their lia maximum extents in the 14th 17th and 19th centuries with most reaching their greatest lia extent in the final 1850 1860 ad advance

little ice age proxy glacier mass balance records reconstructed from tree rings in the mt waddington area british columbia coast mountains canada the intention of this research was to explore whether dendroclimatological relationships could be used to reconstruct long term proxy records of little ice age glacier mass balance changes in the southern coast mountains of british columbia tree ring width chronologies from the mt waddington area were used in concert with historical glacier records to construct models spanning the past 450 years the approach was to build models that were based on derived relationships between tree ring growth and glacier mass balance 1 warmer temperatures in the summer positively influence tree growth but are detrimental to glacier health 2 colder temperatures during the winter and deeper snowpack have a negative impact on tree growth whereas they are related to greater accumulation on the glacier during the winter season stepwise regression analyses were applied to tree ring chronologies to predict glacier mass balance at local and regional scales the models of net annual balance for the region regional data set show that periods of positive mass balance occurred in the ad 1750s 1820s to 1830s and 1970s peaks of winter balance correspond closely to these periods showing a sharp drop in winter mass balance towards the end of the nineteenth century wavelet analyses suggest that glacial mass balance regimes in the region respond synchronously to pacific ocean circulation systems such as the el nino southern oscillation and the pacific decadal oscillation

circulation and transformation of atlantic water in the eurasian basin and the contribution of the fram strait inflow branch to the arctic ocean heat budget abstract the inflows of atlantic water from the nordic seas to the arctic ocean through fram strait and over the barents sea are examined and their pathways and transformations in the eurasian basin are described based primarily on hydrographic observations from two cruises with rv polarstern in 2007 and 2011 the contrast between the high salinity atlantic water core in the nansen basin and the lower atlantic water salinity in the amundsen basin combined with a salinity minimum below the atlantic layer suggest that the fram strait branch mainly remains in the nansen basin while the barents sea branch continues along the continental slope enters the amundsen basin and provides most of the atlantic water in the makarov and canada basins to examine the consequences of such a circulation pattern recently published estimates of the in and outflows of volume and liquid freshwater through the barents sea bering strait and the canadian arctic archipelago as well as river runoff net precipitation and ice export are reviewed and added together to achieve volume and freshwater balances net outflows through fram strait of 2 3 sv and 100 msv respectively are required this is reasonably close to the recently reported fram strait transport estimates the net outflows are separated into two parts upper layer transports less dense than the entering atlantic water and lower layer transports as dense as or denser than the atlantic water the largest net volume outflow occurs in the lower layer 1 65 sv while the liquid freshwater is almost exclusively exported in the 0 64 sv net outflow in upper layer leading to unrealistically low salinities in the upper layer compared with observations atlantic water is north of svalbard transformed into less saline surface water through melting of sea ice which can supply the necessary higher salinity halocline water to the upper layer 1 23 sv of halocline water of salinity 34 2 must be added to obtain a more realistic salinity of 33 1 leading to a total export of 1 84 sv upper layer water in the east greenland current existing observations of the net transports into and out of the arctic ocean through fram strait in different temperature classes are used to estimate the heat loss of the atlantic water entering the arctic ocean through fram strait about 10 tw are supplied to the atmosphere in addition to the loss of 24 tw occurring in connection with the formation of the halocline water if the hypothesis that the fram strait branch remains in the nansen basin is true it implies a heat loss between 5 and 15 w m 2 in the nansen basin depending upon how much heat is temporarily stored in the water column this is high compared to the 2 w m 2 commonly cited as the ocean heat flux to the atmosphere in the arctic ocean

neogloboquadrina pachyderma sinistral coiling as paleoceanographic tracers in polar oceans evidence from northeast water polynya plankton tows sediment traps and surface sediments the abundance and chemistry of the planktonic foraminifera neogloboquadrina pachyderma sinistral coiling have long been used as tools for monitoring polar surface ocean changes and for correlating these changes to atmospheric and thermohaline circulation fluctuations however due to its remote habitat very little is known about how modern n pachyderma s respond to changing environmental conditions in the polar seas modern samples of n pachyderma s from the northeast water polynya provide a means for studying how environmental conditions affect the vertical distribution and chemistry of this species highest abundances of n pachyderma s were associated with the chlorophyll maximum in the surface 20 80 m where they are exploiting their primary food source evidence suggests that the addition of a calcite crust modifies the calcite tests of some n pachyderma s between 50 and 200 m increasing shell density and modifying shell chemistry the shell mass of encrusted forms is 3 4 times greater than the nonencrusted forms between 50 and 200 m the oxygen isotope composition of n pachyderma s shells increase by 1 5 in response to local water column gradients the 13c values of n pachyderma s are basically invariant with depth in this region are consistently 1 0 depleted in comparison with the 13c for equilibrium calcite and remain basically constant during the shell thickening process mass balance calculations suggest that encrustation occurs at all depths but abundance counts suggest that the process occurs mostly at the depth of the main pycnocline sediment fluxes of n pachyderma s occur during a 2 week bloom event and decrease to almost zero below complete ice cover the decoupling of the processes controlling abundances and shell chemistry explain the discrepancies between transfer function and isotopically derived paleotemperature estimates of surface conditions in some oceanic settings the ability of 18o to record surface ocean conditions will depend on vertical water column gradients as evidenced by the differences in core top calibrations between the north and south atlantic

progress in isotope dendroclimatology numerous studies have demonstrated the potential of stableisotopes in tree rings for quantitative terrestrial palaeoclimaticreconstruction ramesh et al 1986 heaton 1999 switsur andwaterhouse 1998 mccarroll and loader 2004 2005 but the earlywidespread application of isotope dendroclimatology has been hin dered by laborious technical procedures that have until recently prevented wider application of this technique and severely con strained progress developments in mass spectrometry preston andowens 1985 barrie et al 1995 filot et al 2006 leuenberger andfilot 2007 and sample preparation techniques leavitt and danzer 1993 loader et al 1997 brendel et al 2000 schulze et al 2004 rinneet al 2005 gaudinskiet al 2005 haverevolutionisedthe eldand enabled development of stable isotope chronologies with aheightened degree of replication gagen et al 2007 and temporalrange treydteetal 2006 thatwaspreviouslynotpracticalandrarelyobserved in any other proxy record outside of dendroclimatology these and associated advances are re ected in the dramatic increasein the number and diversity of isotope tree ring papers presented atrecent international conferences the thirty isotope tree ring paperspresented at the recent 7th international conference on dendrochro nology beijing 11 17june2006 aretrulyinstarkcontrasttothetwodelivered at the 2nd international workshop on global dendroclima tology 1980 long 1982 wigley 1982 in this volume the progressand advances in isotope dendroclimatology are critically reviewed inthe context of the initial work and aspirations of the early pioneers inthis eld and new directions and methodologies are explored dendroclimatology is an established eld of palaeoclimatologyused in its scienti c form since the early 20th century however theapplication of stable isotope techniques to dendroclimatology is morerecent conceptually the seed was planted when urey 1947 statedthat it seems probable that plant carbon compounds synthesised atdifferent temperatures may contain varying amounts of c

synchronisation of palaeoenvironmental events in the north atlantic region during the last termination a revised protocol recommended by the intimate group abstract the north atlantic intimate group of the inqua palaeoclimate commission has previously recommended an event stratigraphy approach for the synchronisation of records of the last termination using the greenland grip isotopic record as the regional stratotype and intcal98 for the calibration of radiocarbon dates lowe j j hoek w intimate group 2001 inter regional correlation of palaeoclimatic records for the last glacial interglacial transition a protocol for improved precision recommended by the intimate project group quaternary science reviews 20 1175 1187 here we present a revised protocol for time stratigraphic correlation in the north atlantic region over a more extended time period 30 8 ka this employs the new ngrip isotopic record and associated greenland ice core chronology 2005 gicc05 as the regional stratotype intcal04 for the calibration of radiocarbon dates bayesian based statistical procedures for the construction of age models and tephrochronology to validate correlations between regional site records

paleoceanographic evolution of the sw svalbard margin 76 n since 20 000 14c yr bp abstract two cores from the southwestern shelf and slope of storfjorden svalbard taken at 389 m and 1485 m water depth have been analyzed for benthic and planktic foraminifera oxygen isotopes and ice rafted debris the results show that over the last 20 000 yr atlantic water has been continuously present on the southwestern svalbard shelf however from 15 000 to 10 000 14c yr bp comprising the heinrich event h1 interval the bolling allerod interstades and the younger dryas stade it flowed as a subsurface water mass below a layer of polar surface water in the benthic environment the shift to interglacial conditions occurred at 10 000 14c yr bp due to the presence of a thin upper layer of polar water surface conditions remained cold until ca 9000 14c yr bp when the warm atlantic water finally appeared at the surface neither extensive sea ice cover nor large inputs of meltwater stopped the inflow of atlantic water its warm core was merely submerged below the cold polar surface water

effect of scaling and regression on reconstructed temperature amplitude for the past millennium 1 examination of large scale millennial long temperature reconstructions reveals a wide range of datasets and methods used for calibration proxy time series are commonly calibrated against overlapping instrumental records representing different seasons northern hemisphere latitudinal bands and including or excluding sea surface temperature data methodological differences include using scaling or regression the calibration time period and smoothing data before calibration we find that these various approaches alone can result in differences in the reconstructed temperature amplitude of about 0 5 c this magnitude is equivalent to the mean annual temperature change for the northern hemisphere reported in the last ipcc report for the 1000 1998 period a more precise assessment of absolute reconstructed temperature amplitudes is necessary to help quantify the relative influences of forcing mechanisms in climate models

a 1052 year tree ring proxy for alpine summer temperatures a june august alpine temperature proxy series is developed back to ad 951 using 1 527 ring width measurements from living trees and relict wood the reconstruction is composed of larch data from four alpine valleys in switzerland and pine data from the western austrian alps these regions are situated in high elevation alpine environments where a spatially homogenous summer temperature signal exists in an attempt to capture the full frequency range of summer temperatures over the past millennium from inter annual to multi centennial scales the regional curve standardization technique is applied to the ring width measurements correlations of 0 65 and 0 86 after decadal smoothing with high elevation meteorological stations since 1864 indicate an optimal response of the rcs chronology to june august mean temperatures the proxy record reveals warm conditions from before ad 1000 into the thirteenth century followed by a prolonged cool period reaching minimum values in the 1820s and a warming trend into the twentieth century this latter trend and the higher frequency variations compare well with the actual high elevation temperature record the new central alpine proxy suggests that summer temperatures during the last decade are unprecedented over the past millennium it also reveals significant similarities at inter decadal to multi centennial frequencies with large scale temperature reconstructions however deviating during certain periods from h h lamb s european north atlantic temperature history

summer temperature variations in the european alps a d 755 2004 abstract annually resolved summer temperatures for the european alps are described the reconstruction covers the a d 755 2004 period and is based on 180 recent and historic larch larix decidua mill density series the regional curve standardization method was applied to preserve interannual to multicentennial variations in this high elevation proxy dataset instrumental measurements from high low elevation grid boxes back to 1818 1760 reveal strongest growth response to current year june september mean temperatures the reconstruction correlates at 0 7 with high elevation temperatures back to 1818 with a greater signal in the higher frequency domain r 0 8 low elevation instrumental data back to 1760 agree with the reconstruction s interannual variation although a decoupling between warmer instrumental and cooler proxy data before 1840 is noted this offset is larger than during any period of overlap with more recent high elevation instrumental data even though the proxy time series

integrated monitoring of mountain glaciers as key indicators of global climate change the european alps the internationally recommended multi level strategy for monitoring mountain glaciers is illustrated using the example of the european alps where especially dense information has been available through historical times this strategy combines in situ measurements mass balance length change with remote sensing inventories and numerical modelling it helps to bridge the gap between detailed local process oriented studies and global coverage since the 1980s mass balances have become increasingly negative with values close to 1 m w e a 1 during the first 5 years of the 21st century the hot dry summer of 2003 alone caused a record mean loss of 2 45 m w e roughly 50 above the previous record loss in 1998 more than three times the average between 1980 and 2000 and an order of magnitude more than characteristic long term averages since the end of the little ice age and other extended periods of glacier shrinkage during the past 2000 years it can be estimated that glaciers in the european alps lost about half their total volume roughly 0 5 a 1 between 1850 and around 1975 another 25 or 1 a 1 of the remaining amount between 1975 and 2000 and an additional 10 15 or 2 3 a 1 in the first 5 years of this century

historically unprecedented global glacier decline in the early 21st century observations show that glaciers around the world are in retreat and losing mass internationally coordinated for over a century glacier monitoring activities provide an unprecedented dataset of glacier observations from ground air and space glacier studies generally select specific parts of these datasets to obtain optimal assessments of the mass balance data relating to the impact that glaciers exercise on global sea level fluctuations or on regional runoff in this study we provide an overview and analysis of the main observational datasets compiled by the world glacier monitoring service wgms the dataset on glacier front variations 42000 since 1600 delivers clear evidence that centennial glacier retreat is a global phenomenon intermittent readvance periods at regional and decadal scale are normally restricted to a subsample of glaciers and have not come close to achieving the maximum positions of the little ice age or holocene glaciological and geodetic observations 5200since 1850 show that the rates of early 21st century mass loss are without precedent on a global scale at least for the time period observed and probably also for recorded history as indicated also in reconstructions from written and illustrated documents this strong imbalance implies that glaciers in many regions will very likely suffer further ice loss even if climate remains stable

stable isotopes in planktonic and benthic foraminifera from arctic ocean surface sediments oxygen and carbon isotopic analyses have been performed on the tests of planulina wuellerstorfi and three size fractions of sinistral neogloboquadrina pachyderma recovered from 33 arctic ocean surface sediment samples stable isotopic compositions of n pachyderma are found to be dependent on the test size larger specimens show considerable enrichment in both 18o and 18c the difference between the isotopic compositions of the 63 125 and 125 250 m size fractions in n pachyderma can be explained by biogenic fractionation effects during foraminiferal test growth larger 250 500 m n pachyderma displayed accretions of secondary calcite i e the outermost shell contained significant amounts of inorganically precipitated magnesium calcite thus larger foraminifera may not be suited for down core stable isotopic studies there is a difference of 2 between 18o values of surface samples from the eastern and western arctic ocean reflecting large differences between surface water salinity in these re

striking similarities in temporal changes to spring sea ice occurrence across the central canadian arctic archipelago over the last 7000 years abstract a 7000 year spring sea ice record for victoria strait arc 4 and dease strait arc 5 in the canadian arctic archipelago caa has been determined by quantification of the sea ice diatom derived biomarker ip 25 in two marine sediment piston cores obtained in 2005 the chronologies of the arc 4 and arc 5 cores were determined using a combination of 14 c ams dates obtained from macrobenthic fossils and magnetic susceptibility measurements the ages of the tops of the piston cores were estimated by matching chemical and physical parameters with those obtained from corresponding box cores these analyses revealed that while the top of the arc 4 piston core was estimated to be essentially modern ca 60 cal yr bp a few hundred years of sediment appeared to be absent from the arc 5 piston core downcore changes to ip 25 fluxes for both cores were interpreted in terms of variations in spring sea ice occurrence and correlations between the individual ip 25 flux profiles for victoria strait dease strait and barrow strait reported previously were shown to be statistically significant at both 50 and 100 year resolutions the ip 25 data indicate lower spring sea ice occurrences during the early part of the record ca 7 0 3 0 cal kyr bp and for parts of the late holocene ca 1 5 0 8 cal kyr bp especially for the two lower latitude study locations in contrast higher spring sea ice occurrences existed during ca 3 0 1 5 cal kyr bp and after ca 800 cal yr bp the observation of consecutively lower and higher spring sea ice occurrence during two periods of the late holocene coincides broadly with the medieval warm period and little ice age epochs respectively the ip 25 data are complemented by particle size and mineralogical data although these may alternatively reflect changes in sea level at the study sites the ip 25 data are also compared to previous proxy based determinations of palaeo sea ice and palaeoclimate for the caa including those based on bowhead whale remains and dinocyst assemblages the spatial consistency in the proxy data which most notably indicates an increase in spring sea ice occurrence around 3 cal kyr bp provides a potentially useful benchmark for the termination of the holocene thermal maximum for the central caa

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

paleoceanographic reconstructions of surface ocean conditions in the greenland iceland and norwegian seas through the last 14 ka based on diatoms prior reconstructions of the last glacial maximum and the holocene did not include detailed paleoclimate data from the greenland iceland and norwegian gin seas which cover sensitive areas for oceanographic boundaries sea ice distribution and deep water formation in order to fill this gap we studied nine well dated sediment cores from this area and reconstructed the paleoceanographic conditions of the surface gin seas at 2000 year intervals since 13 400 bp based on the diatom record results show that a n s extending sea ice free corridor had opened along norway already at 13 400 bp indicating a northward flow of a branch of the north atlantic drift possibly caused by a change in the jet stream flow due to the decreased height of the north american ice sheet a major change of climatic conditions occurred over the gin seas as the insolation anomaly reached its maximum around 9000 bp when the sea ice cover and the oceanic fronts retreated to a northwesterly position along greenland and the ocean temperatures rose the first half of the holocene is recorded as the warmest period during the last 13 400 bp in the gin seas the duration of this climatic optimum decreased both toward the north and toward the margins of the area the second half of the holocene is characterized by a cooling trend in step with the decreasing insolation these results support the proposal of imbrie et al 1992 that the gin seas region acts as an initial responder to insolation changes

fennoscandia revisited a spatially improved tree ring reconstruction of summer temperatures for the last 900 years despite the spatially homogenous summer temperature pattern in fennoscandia there are large spreads among the many existing reconstructions resulting in an uncertainty in the timing and amplitude of past changes also there has been a general bias towards northernmost fennoscandia in an attempt to provide a more spatially coherent view of summer june august jja temperature variability within the last millennium we utilized seven density and three blue intensity scots pine pinus sylvestris l chronologies collected from the altitudinal scandinavian mountains and latitudinal northernmost part treeline to attain a jja temperature signal as strong as possible as well as preserving multicentury scale variability we used a new tree ring parameter where the earlywood information is removed from the maximum density and blue intensity and a modified signal free standardization method two skilful reconstructions for the period 1100 2006 ce were made one regional reconstruction based on an average of the chronologies and one field gridded reconstruction the new reconstructions were shown to have much improved spatial representations compared to those based on data from only northern sites thus making it more valid for the whole region an examination of some of the forcings of jja mean temperatures in the region shows an association with sea surface temperature over the eastern north atlantic but also the subpolar and subtropical gyres moreover using superposed epoch analysis a significant cooling in the year following a volcanic eruption was noted and for the largest explosive eruptions the effect could remain for up to 4 years this new improved reconstruction provides a mean to reinforce our understanding of forcings on summer temperatures in the north european sector