late holocene surface ocean conditions of the norwegian sea voring plateau 1 late holocene sea surface ocean conditions of the eastern norwegian sea voring plateau are inferred from planktic stable isotopes and planktic foraminiferal assemblage changes in cores jm97 948 2a and md952011 66 97 n 7 64 e strong covariance between the planktic stable oxygen isotopic record and abundance changes of n pachyderma sin show that major changes in surface ocean conditions are reflected both in the geochemical composition of the foraminiferal tests as well as in the composition of the foraminiferal fauna surface ocean conditions warmer than present were common during the past 3000 years during the so called medieval warm period surface conditions were highly variable with marked changes in sea surface temperature the warmest sea surface temperatures during this period occurred between 800 and 550 years bp 0 bp ad 2000 climatic deterioration recorded as decreases in sea surface temperature occurred at about 2750 1550 400 and 100 years bp the cooling events at about 2750 and 1550 years bp appear to correlate with increases in ice rafted debris in the north atlantic based on the results from jm97 948 2a and md952011 the onset of the little ice age cooling trend seems to have occurred around 700 600 years bp faunal changes indicate two cooling events during the little ice age at 400 and 100 years bp that correspond to decreases in fennoscandian summer temperatures and increases in ice rafted debris in the eastern north atlantic index terms 3030 marine geology and geophysics micropaleontology 4267 oceanography general paleoceanography 4870 oceanography biological and chemical stable isotopes keywords paleoceanography stable isotope holocene micropaleontology citation andersson c b risebrobakken e jansen and s o dahl late holocene surface ocean conditions of the norwegian sea voring plateau paleoceanography 18 2 1044 doi 10 1029 2001pa000654 2003

diatom response to the holocene climatic optimum on the north icelandic shelf abstract a diatom record from core md992275 on the north icelandic shelf reveals palaeoclimatic and palaeoceanographic changes during the time interval 9000 to 5600 cal year bp the study period includes the holocene climate optimum hco as widely known in the north atlantic region a comparison with data for the last 2000 years and with the present day surface sediment diatom assemblages shows that there was considerably stronger influence of atlantic water masses in the area during the hco than in the late holocene and today the results of cluster analysis and principal component analysis divide the studied period into three intervals each characterised by a specific diatom assemblage the assemblages indicate changes in the interaction of the relatively warm irminger current ic and the cold east greenland current egc and east icelandic current eic the north icelandic shelf was strongly affected by the ic during the interval 8000 6800 cal year bp which may be the warmest period of the holocene during the intervals 9000 8000 and 6800 5600 cal year bp the influence of the ic was relatively weak and that of the egc and eic increased correspondingly the well known 8200 cal year bp cooling event shown in many records from the north atlantic is reflected by a relatively strong influence of the egc and eic between about 8300 and 8100 cal year bp in our record however the diatom assemblages show that the inferred circulation change did not bring the strength of the ic down to the levels seen at present and during the last two millennia

multicentury scale records of carbonate hydrographic variability on the northern iceland margin over the last 5000 years the waters off northern iceland are subjected to extreme hydrographic variability on annual to decadal timescales in years when cold low salinity water moves coastward and sea ice is prevalent i e the late 1960s marine productivity of surface waters is low because the water column is well stratified in the opposite oceanographic mode warm salty atlantic water dominates the shelf and vertical mixing results in high productivity we track these two contrasting modes by measuring the carbonate content of marine sediments a proxy for productivity in three cores from northern iceland the fjord record b997 328pc is anchored by eleven 14c ams dates and has a resolution of one sample every 50 yr thirteen oscillations occurred over the last 4800 cal yr with an average length of 370 yr these are superimposed on a long term decrease in net carbonate accumulation the little ice age is marked by the largest decrease in carbonate content and in flux with smaller minima at 2300 and 3000 cal yr b p marked peaks in carbonate optima occurred at 2000 and 3800 cal yr b p the carbonate record from b997 328pc can be correlated with records on the inner shelf b997 330pc and midshelf b997 327pc indicating that significant regional changes in oceanography occurred at the southern margin of the norwegian greenland sea the marine carbonate fluctuations closely track temperature reconstructions from the greenland summit site for the last 2000 cal yr and show similar but slightly offset oscillations between 2000 and ca 4800 cal yr b p

arctic sea ice variability in the context of recent atmospheric circulation trends abstract forty years 1958 97 of reanalysis products and corresponding sea ice concentration data are used to document arctic sea ice variability and its association with surface air temperature sat and sea level pressure slp throughout the northern hemisphere extratropics the dominant mode of winter january march sea ice variability exhibits out of phase fluctuations between the western and eastern north atlantic together with a weaker dipole in the north pacific the time series of this mode has a high winter to winter autocorrelation 0 69 and is dominated by decadal scale variations and a longer term trend of diminishing ice cover east of greenland and increasing ice cover west of greenland associated with the dominant pattern of winter sea ice variability are large scale changes in sat and slp that closely resemble the north atlantic oscillation the associated sat and surface sensible and latent heat flux anomalies are largest over the portions of the marginal sea ice zone in which the tr

arctic palaeo river discharge and environmental change evidence from the holocene kara sea sedimentary record abstract in this paper we summarize data on terrigenous sediment supply in the kara sea and its accumulation and spatial and temporal variability during holocene times sedimentological organic geochemical and micropaleontological proxies determined in surface sediments allow to characterize the modern riverine terrigenous sediment input ams 14c dated sediment cores from the ob and yenisei estuaries and the adjacent inner kara sea were investigated to determine the terrigenous sediment fluxes and their relationship to paleoenvironmental changes the variability of sediment fluxes during holocene times is related to the post glacial sea level rise and changes in river discharge and coastal erosion input whereas during the late middle holocene most of the terrigenous sediments were deposited in the estuaries and the areas directly off the estuaries huge amounts of sediments accumulated on the kara sea shelf farther north during the early holocene before about 9 cal kyr bp the maximum accumulation at that time is related to the lowered sea level increased coastal erosion and increased river discharge based on sediment thickness charts echograph profiles and sediment core data we estimate an average holocene 0 11 cal kyr bp annual accumulation of 194 106 t yr 1 of total sediment for the whole kara sea based on late holocene modern sediment accumulation in the estuaries probably 12 106 t yr 1 of riverine suspended matter i e about 30 of the input may escape the marginal filter on a geological time scale and is transported onto the open kara sea shelf the high resolution magnetic susceptibility record of a yenisei core suggests a short term variability in siberian climate and river discharge on a frequency of 300 700 yr this variability may reflect natural cyclic climate variations to be seen in context with the interannual and interdecadal environmental changes recorded in the high northern latitudes over the last decades such as the nao ao pattern a major decrease in ms values starting near 2 5 cal kyr bp being more pronounced during the last about 2 cal kyr bp correlates with a cooling trend over greenland as indicated in the gisp 2 ice core extended sea ice cover in the north atlantic and advances of glaciers in western norway our still preliminary interpretation of the ms variability has to be proven by further ms records from additional cores as well as other high resolution multi proxy arctic climate records

flux of ice rafted detritus from sea ice in the fram strait abstract a three year particle flux record from the eastern fram strait between greenland and svalbard revealed a rather untypical seasonal flux pattern compared to other particle flux studies from the nordic seas in the eastern fram strait this pattern is characterised by a sudden four to six fold increase of the particle flux in january when no daylight is available to support any biological productivity comparison with sea ice distribution maps led to the conclusion that the sudden increase in the flux is due to ice rafted detritus released from sea ice which originated from the svalbard archipelago and from the northern barents sea detailed grain size analyses of the silt fraction indicated the 10 m fraction of the lithogenic matter to be clearly enriched due to ird input even more important is the observation that lithogenic material 40 m occurs exclusively during the ice rafting event and therefore appears to be a suitable indicator for ird transported on sea ice thus in addition to coarse ird e g 500 m which is mainly derived from icebergs the analysis of fine ird 40 m in deep sea sediments can be used to reconstruct paleo sea ice extensions

effects of ice coverage and ice rafted material on sedimentation in the fram strait as little is known about pelagic sedimentation processes in arctic environments1 the interpretation of biological and chemical processes as well as the reconstruction of ancient conditions including those in the glacial north atlantic is difficult here we provide sediment trap results which show that the position of the sea ice boundary significantly influences the particle flux the seasonal variability of the particle flux differed markedly in the various sediment trap sites in fram strait depending on the behaviour of the sea ice under complete ice cover sedimentation is very low whereas maximum sedimentation is found at the ice margin the highest particle flux observed showing a large lithogenic component was observed at the ice edge where the water was warmer 2 c we find that high biogenic opal fluxes are characteristic of the summer ice margin indicating that the sedimentary record of opal fluxes may allow the position of ice margins in the past to be reconstructed

nonuniform response of the major surface currents in the nordic seas to insolation forcing implications for the holocene climate variability 1 high resolution sediment cores from the voring plateau the north iceland shelf and the east greenland shelf have been studied to investigate the stability of major surface currents in the nordic seas during the holocene results from diatom assemblages and reconstructed sea surface temperatures ssts indicate a division of the holocene into three periods the holocene climate optimum 9500 6500 calendar cal years bp the holocene transition period 6500 3000 cal years bp and the cool late holocene period 3000 0 cal years bp the overall climate development is in step with the decreasing insolation on the northern hemisphere but regional differences occur regarding both timing and magnitude of sst changes sites under the direct influence of the norwegian atlantic current and the irminger current indicate sst cooling of 4 5 c from early holocene to present compared to 2 c recorded under the east greenland current superimposed on the general holocene cooling trend there is a high frequency sst variability which is in the order of 1 1 5 c for the voring plateau and the east greenland shelf and 2 5 3 c on the north iceland shelf

orbitally driven insolation forcing on holocene climate trends evidence from alkenone data and climate modeling a global spatial pattern of long term sea surface temperature sst trends over the last 7000 years is explored using a comparison of alkenone derived sst records with transient ensemble climate simulations with a coupled atmosphere ocean circulation model under orbitally driven insolation forcing the spatial trend pattern both in paleo sst data and in model results shows pronounced global heterogeneity generally the extratropics cooled while the tropics experienced a warming during the middle to late holocene we attribute these divergent holocene climate trends to seasonally opposing insolation changes furthermore climate mode changes similar to the arctic north atlantic oscillation are superimposed on the prevalent pattern it is concluded that nonlinear changes in the entire seasonal cycle of insolation played a dominant role for the temporal evolution of holocene surface temperatures for understanding of marine proxy data apart from the dominance of summer insolation in high latitudes a notable shift in the maximum insolation of the year in low latitudes has to be taken into account which may influence timing of phytoplankton production and thus alters the seasonal origin of temperature signals recorded in the proxies

a diatom based transfer function for reconstructing sea ice concentrations in the north atlantic abstract a diatom based sea ice transfer function is developed using 99 surface sediment samples from the north atlantic and the associated modern sea ice concentrations canonical correspondence analysis cca is applied to the species assemblages of the surface sediment samples and the association of the species with two environmental parameters august sea surface temperature and may sea ice concentration is assessed the results of this analysis indicate negative correlation between sea ice and sea surface temperature and that a group of diatom species is strongly associated with sea ice especially may sea ice concentration the results of the cca legitimate the development of a diatom based sea ice transfer function the maximum likelihood method has been applied as the transfer function method as it has been proven most suitable with this particular data set the newly developed transfer function is then used to reconstruct may sea ice concentration in three cases each focusing on a different time period the last glacial maximum the younger dryas and the holocene in all three cases the transfer function produces reasonable results when compared to other paleoclimatic proxy results this suggests that the sea ice concentration reconstructed by the diatom based sea ice transfer function is a valid and reliable method which can be applied as a valid proxy for may sea ice concentration

a new late weichselian and holocene marine chronology for the western svalbard slope 30 000 0 cal years bp abstract data have been compiled from eleven sediment cores from 76 to 80 n on the western svalbard slope the cores are from water depths between 630 and 1880 m and show clear similarities in lithology and magnetic susceptibility all cores penetrated into mass transported sediments from glacigenic debris flow events and turbidity flow events the mass transport probably occurred when the ice reached the shelf edge the deposits date between 24 080 150 and 23 550 185 calibrated cal years bp the records also include laminated fine grained sediments interpreted as deposits from sediment laden meltwater plumes dated between 14 780 220 and 14 300 260 cal years bp in holocene sediments a diatom rich fine grained layer dates 10 100 150 to 9840 200 cal years bp the eleven cores have been stacked into one record with absolute age control from 35 ams14c dates together with oxygen isotope stratigraphy and contents of ice rafted detritus the stacked record provides a useful chronology tool for cores on the western svalbard slope our study improves the age control of earlier well documented glacial events and shows that the maximum glacial state and the onset of the deglaciation both occurred 2500 3000 years earlier than previously reconstructed for the western svalbard margin the results indicate that during the last 30 000 years advance and retreat of the svalbard barents sea ice sheet was closely linked to the flow of atlantic water and polar water over the margin

dynamics of atlantic water advection to the norwegian greenland sea a time slice record of carbonate distribution in the last 300 ky abstract short term variability in volume and configuration of atlantic water advection to the norwegian greenland sea ngs has recently been identified as a new and significant element for northern hemisphere glacial interglacial climatic fluctuations the amount of salt heat and moisture transferred by atlantic waters to the high arctic effectively influences northern hemisphere climates and is critical for the overall oceanic turnover rate in particular determining the extent and duration of atlantic water intrusions in the ngs is essential because of 1 its effect on the climate of the nordic continents and 2 its trigger function on the stability of the ice sheets with a weak inflows of atlantic water during glacials promoting an increase in ice volume by moisture supply to polar areas and b positive feed back mechanisms of atlantic water intrusions during ice sheet decay in this study the dynamics of surface water mass regimes in the ngs have been reconstructed for the past 300 ky by means of time slice compilations of calcium carbonate distribution and micropaleontologic proxies in addition carbonate preservation records are used to quantify deep water ventilation and production rates in contrast to the climap scenario but in accordance with many recent publications results of this study indicate that atlantic water advection was also a common feature during most glacial periods but varied strongly in volume and configuration significant modes recognized are 1 the full interglacial mode with a wide inflow of warm atlantic waters covering a broad area in the eastern sector of the ngs and extending far north combined with excellent carbonate preservation and very efficient deep water formation stages 1 and 5 5 1 2 the moderate interglacial mode with a rather small extension of atlantic waters along a narrow corridor in the southeastern sector of the ngs but still very efficient deep water exchange stages 9 isotopic events 7 5 7 3 7 1 5 3 and 5 1 3 pronounced cool phases during interglacials with only a very narrow inflow of atlantic waters into the southeastern ngs while the coastal areas off norway were still affected by iceberg drift substages 7 4 and 5 2 carbonate preservation records indicate ongoing deep water formation in the ngs 4 the normal glacial mode characterized by a variable but persistent inflow of cool temperate atlantic water lower stage 8 repetitively during stages 6 4 3 1 and 2 carbonate preservation records indicate ongoing deep water formation in the ngs 5 short glacial and deglacial periods characterized by episodic high inputs of ird evidenced by a wide coverage of diamicton deposition and strong carbonate dissolution e g episodically within stages 10 6 and 2 the 6 5 4 3 and 2 1 transitions some of these ngs diamicton layers correlate with heinrich layers in the north atlantic but generally ngs diamicton layers occur more frequently than heinrich layers the role of atlantic water influence during these events remains enigmatic but atlantic water influence is frequently found just above and below these sections a scenario with rapid ice sheet disintegration induced by atlantic water advection via increase of the thermal regime along the ice margin possibly triggered by small scale sea level rise might be envisaged more obviously the short term cessation of deep water formation in the ngs as evidenced by the dissolution spikes may be correlated with contemporaneous ventilation minima in the north atlantic

holocene glacial and climatic variations on spitsbergen svalbard holocene glacial and climatic variations have been inferred from investigations of sediment cores from the proglacial lake linnevatnet western spitsbergen a low content of glacially derived coal absence of regular laminations and a slow sedimentation rate in the lower part of the lacustrine sediments indicate that the former glaciers that existed within the catchment area during the last ice age melted quickly away as a result of the younger dryas holocene warming and during the next 6000 years there were no glaciers in the valley increasing coal content incipient laminations and rising sedimentation rates indicate that the glacier linnebreen started to form 4000 5000 years ago probably as a response to the late holocene cooling the holocene maximum extent of the glacier occurred during the little ice age starting with a pronounced ice advance in the thirteenth or fourteenth century a well dated core from billefjorden which is assumed to reflect glacial fluctuations in the inner part of the i

the holocene thermal maximum and late holocene cooling in the tundra of ne european russia abstract to investigate the holocene climate and treeline dynamics in the european russian arctic we analysed sediment pollen conifer stomata and plant macrofossils from lake kharinei a tundra lake near the treeline in the pechora area we present quantitative summer temperature reconstructions from lake kharinei and lake tumbulovaty a previously studied lake in the same region using a pollen climate transfer function based on a new calibration set from northern european russia our records suggest that the early holocene summer temperatures from 11 500 cal yr bp onwards were already slightly higher than at present followed by a stable holocene thermal maximum htm at 8000 3500 cal yr bp when summer temperatures in the tundra were ca 3 c above present day values a picea forest surrounded lake kharinei during the htm reaching 150 km north of the present taiga limit the htm ended with a temperature drop at 3500 2500 cal yr bp associated with permafrost initiation in the region mixed spruce forest began to disappear around lake kharinei at ca 3500 cal yr bp with the last tree macrofossils recorded at ca 2500 cal yr bp suggesting that the present wide tundra zone in the pechora region formed during the last ca 3500 yr

active tectonics along the wadi araba jordan valley transform fault a geological study has been carried out along the 200 km long wadi araba following the transform fault that separates the arabian and sinai african plates recent movements along this structure affect upper pleistocene holocene deposits and archaeological sites kinematic indicators show sinistral strike slip and oblique movements in agreement with the relative motion between the two plates other evidence of recent horizontal displacement exists along the jordan valley fault both on the dead sea lake tiberias segment and on the segment north of lake tiberias a minimum horizontal slip rate of 1 cm yr 1 has been estimated for both the southern segment of the wadi araba fault and for the southern jordan river fault the two faults can be roughly subdivided into at least four segments two in the wadi araba 80 km long each one from the dead sea to lake tiberias 130 km and one from lake tiberias to the hula graben 30 km faulting may also occur along shorter subsegments as shown by bends in the wadi araba jordan river fault and by the growth of local compression and extension features instrument recorded seismicity appears to be mainly concentrated along some of these subsegments a comparison between the observed seismic and field determined slip rates across the fault indicates possible strain accumulation during the last 2000 years

variability of sea surface temperature and sea ice cover in the fram strait over the last two millennia abstract a sediment core located on the west spitzbergen margin in the fram strait 78 54 931 n 6 46 005 e water depth 1497 m was analyzed for its dinocyst content in order to reconstruct hydroclimatic variations of the last 2500 years the relative abundance of dinocyst taxa and principal component analysis show a major transition at about 300 cal years bp it is characterized by the disappearance of thermophilic taxa spiniferites mirabilis hyperacanthus and impagidinium sphaericum and the increase of polar subpolar taxa impagidinium pallidum and pentapharsodinium dalei sea surface temperature sst estimates suggest warmer conditions than present anomaly 2 c averaging at 7 c in summer until 300 cal years bp although cooling pulses are recorded around 1700 1500 1200 and 800 cal years bp the last 300 years were marked by a cooling from 7 6 to 3 5 c and sea ice cover increasing up to 7 months yr the results demonstrate that the fram strait area is sensitive to hydroclimatic variations notably with respect to sea ice and ssts which are linked to the relative strength of northward flow of north atlantic waters to the east and southward outflow of cold and fresh waters from the arctic ocean based on our data the warmest part of our record around 1320 cal years bp is the only interval of the last 2500 years that provides a possible analogue for the modern post ad 2000 interval which is characterized by sea ice free conditions

late quaternary sedimentation in kejser franz joseph fjord and the continental margin of east greenland the marine sedimentary record in kejser franz joseph fjord and on the east greenland continental margin contains a history of late quaternary glaciation and sedimentation evidence suggests that a middle shelf moraine represents the maximum shelfward extent of the greenland ice sheet during the last glacial maximum on the upper slope coarse grained sediments are derived from the release of significant quantities of iceberg rafted debris ird and subsequent remobilization by subaqueous mass flows the middle lower slope is characterized by hemipelagic sedimentation with lower quantities of ird dropstone mud and sandy mud punctuated episodically by deposition of diamicton and graded sand gravel facies by subaqueous debris flows and turbidity currents derived from the mass failure of upper slope sediments the downslope decrease of ird reflects either the action of the east greenland current egc confining icebergs to the upper slope or to the more ice proximal setting of the upper slope relative to the lgm ice margin sediment gravity flows on the slope are likely to have fed into the east greenland channel system contributing to its formation in conjunction with the cascade of dense brines down the slope following sea ice formation across the shelf deglaciation commenced after 15 300 14c years as indicated by meltwater derived light oxygen isotope ratios an abrupt decrease in both ird deposition and delivery of coarse grained debris to the slope at this time supports ice recession with icebergs confined to the shelf by the egc glacier ice had abandoned the middle shelf before 13 000 14c years with ice loss through iceberg calving and deposition of diamicton continued retreat of glacier ice from the inner shelf and through the fjord is marked by a transition from subglacial till bedrock in acoustic records to ice proximal meltwater derived laminated mud to ice distal bioturbated mud ice abandoned the inner shelf before 9100 14c years and probably stabilized in fosters bugt at 10 000 14c years distinct oxygen isotope minima on the inner shelf indicate meltwater production during ice retreat the outer fjord was free of ice before 7440 14c years glacier retreat through the mid outer fjord was punctuated by topographically controlled stillstands where ice proximal sediment was fed into fjord basins the dominance of fine grained commonly laminated facies during deglaciation supports ablation controlled ice mass loss glacimarine sedimentation within the holocene middle outer fjord system is dominated by sediment gravity flow and suspension settling from meltwater plumes suspension sediments comprise mainly mud facies indicating significant meltwater deposition that overwhelms debris release from icebergs in this east greenland fjord system the relatively widespread occurrence of fine grained lithofacies in east greenland fjords suggests that meltwater sedimentation can be significant in polar glacimarine environments the ice distal continental margin is characterized by meltwater sedimentation in the inner shelf deep iceberg scouring over shallow shelf regions winnowing and erosion by the east greenland current on the middle outer shelf and hemipelagic sedimentation on the continental slope

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

late holocene summer sea surface temperatures based on a diatom record from the north icelandic shelf diatom assemblages from a high resolution core on the north icelandic shelf reveal a general late holocene cooling trend which is interrupted by three relatively warm periods diatom data from sur

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

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

was a change in thermohaline circulation responsible for the little ice age long term 800 year and short term 20 year estimates of the rate of deep water formation in the southern ocean are in serious disagreement this disagreement suggests to me that the rate of deep water formation may have been larger during the little ice age lia than it is now

holocene climatic instability a prominent widespread event 8200 yr ago the most prominent holocene climatic event in greenland ice core proxies with approximately half the amplitude of the younger dryas occurred 8000 to 8400 yr ago this holocene event affected regions well beyond the north atlantic basin as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane widespread proxy records from the tropics to the north polar regions show a short lived cool dry or windy event of similar age the spatial pattern of terrestrial and marine changes is similar to that of the younger dryas event suggesting a role for north atlantic thermohaline circulation possible forcings identified thus far for this holocene event are small consistent with recent model results indicating high sensitivity and strong linkages in the climatic system

persistent positive north atlantic oscillation mode dominated the medieval climate anomaly the medieval climate anomaly mca was the most recent pre industrial era warm interval of european climate yet its driving mechanisms remain uncertain we present here a 947 year long multidecadal north atlantic oscillation nao reconstruction and find a persistent positive nao during the mca supplementary reconstructions based on climate model results and proxy data indicate a clear shift to weaker nao conditions into the little ice age lia globally distributed proxy data suggest that this nao shift is one aspect of a global mca lia climate transition that probably was coupled to prevailing la nina like conditions amplified by an intensified atlantic meridional overturning circulation during the mca

recent changes in arctic ocean sea ice motion associated with the north atlantic oscillation examination of a new ice motion dataset of the arctic ocean over a recent eighteen year period 1978 1996 reveals patterns of variability that can be linked directly to the north atlantic oscillation the intensity of the icelandic low one of its centers of action modulates the sea level pressure distribution over a broad region of the arctic ocean and the greenland iceland norwegian and barents seas over the winters of 1988 through 1995 the oscillation has remained in its positive phase contributing to coherent large scale changes in the intensity and character of ice transport in the arctic ocean the significant changes include the weakening of the beaufort gyre the increase in ice export through the fram strait the increase in ice import from the barents kara seas the enhanced eastward transport of sea ice from the laptev sea the weakening of the transpolar drift stream and the reduction in ice extent in the nordic seas all of these changes affect the regional and total sea ice mass balance of the arctic ocean

on the mechanisms behind salinity anomaly signals of the northern north atlantic abstract hydrographic time series from the northern north atlantic throughout the 20th century show oscillations in temperature and salinity at more or less regular intervals the great salinity anomalies described during the 1970s dickson r r meincke j malmberg s a lee a j 1988 the great salinity anomaly in the north atlantic 1968 1982 progress in oceanography 20 103 151 during the 1980s belkin i m levitus s antonov j malmberg s a 1998 great salinity anomalies in the north atlantic progress in oceanography 41 1 68 and during the 1990s belkin i m 2004 propagation of the great salinity anomaly of the 1990s around the northern north atlantic geophysical research letters 31 8 l08306 doi 10 1029 2003gl019334 have distinct amplitudes and all three of them were interpreted as low salinity anomalies propagating downstream through the anti clockwise circulation system of the northern north atlantic ocean further inspection of time series from the northeast atlantic and the northwest atlantic over the past century shows however several other distinct negative anomalies of lesser amplitudes additionally a number of high salinity anomalies can be identified the present paper analyses further the propagation of the negative and positive anomalies and links them together it is shown that they have varying speeds of propagation and that the varying speeds are correlated across the north atlantic we propose that varying volume fluxes in and out of the arctic basin is the causal mechanism behind the anomaly signals and that the north atlantic oscillation nao partly has influence on the flux variations described periods of large decadal scale amplitudes of the nao coincide with periods of large decadal scale oscillation in the marine climate

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

a hemispheric mechanism for the atlantic multidecadal oscillation abstract the physical processes associated with the 70 yr period climate mode known as the atlantic multidecadal oscillation amo are examined based on analyses of observational data a deterministic mechanism relying on atmosphere ocean sea ice interactions is proposed for the amo variations in the thermohaline circulation are reflected as uniform sea surface temperature anomalies in the north atlantic these anomalies are associated with a hemispheric wavenumber 1 sea level pressure slp structure in the atmosphere that is amplified through atmosphere ocean interactions in the north pacific the slp pattern and its associated wind field affect the sea ice export through fram strait the freshwater balance in the northern north atlantic and consequently the strength of the large scale ocean circulation it generates sea surface temperature anomalies with opposite signs in the north atlantic and completes a negative feedback the authors find that the time scale of the cycle is associated with the

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

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

gulf stream density structure and transport during the past millennium the gulf stream transports approximately 31 sv 1 sv 10 6 m 3 s 1 of water and 1 3 10 15 w of heat into the north atlantic ocean the possibility of abrupt changes in gulf stream heat transport is one of the key uncertainties in predictions of climate change for the coming centuries given the limited length of the instrumental record our knowledge of gulf stream behaviour on long timescales must rely heavily on information from geologic archives here we use foraminifera from a suite of high resolution sediment cores in the florida straits to show that the cross current density gradient and vertical current shear of the gulf stream were systematically lower during the little ice age ad 1200 to 1850 we also estimate that little ice age volume transport was ten per cent weaker than today s the timing of reduced flow is consistent with temperature minima in several palaeoclimate records implying that diminished oceanic heat transport may have contributed to little ice age cooling in the north atlantic the interval of low flow also coincides with anomalously high gulf stream surface salinity suggesting a tight linkage between the atlantic ocean circulation and hydrologic cycle during the past millennium

apparent long term cooling of the sea surface in the northeast atlantic and mediterranean during the holocene reconstructions of upper ocean temperature t during the holocene 10 0 ka b p were established using the alkenone method from seven high accumulation sediment cores raised from the northeast atlantic and the mediterranean sea 361n 751n all these paleo t records document an apparent long term cooling during the last 10 kyr in records with indication of a constant trend the apparent cooling ranges from 0 27 to 0 151c kyr 1 records with indication of time variable trend show peak to peak amplitudes in apparent temperatures of 1 2 2 91c a principal component analysis shows that there is one factor which accounts for a very large fraction 67 of the total variance in the biomarker paleo t records and which dominates these records over other potential secondary influences two possible contributions are 1 a widespread surface cooling which may be associated with the transition fromthe hypsithermal interval b9 5 7 ka b p to the neoglaciation b5 7 0 ka b p and 2 a change in the seasonal timing and or duration of the growth period of alkenone producers prymnesiophyte algae the first contribution is consistent with many climate proxy records from the northeast atlantic area and with climate model simulations including milankovitch forcing the second contribution is consistent with the divergence between biomarker and summer faunal paleo t fromearly to late holocene observed in two cores further work is necessary and in particular the apparent discordance between biomarker and faunal t records for the relative stable holocene period must be understood to better constrain the climatic and ecological contributions to the apparent cooling observed in the former records r 2002 elsevier science ltd all rights reserved

a mid holocene shift in arctic sea ice variability on the east greenland shelf records of iceberg rafting and palaeohydrography from two east greenland shelf cores jm96 1206 1 gc and jm96 1207 1 gc are reported benthic foraminifera stable isotopes and ird e uxes indicate a shift toward colder lower salinity polar conditions c 5 cal ka a new proxy of iceberg rafting on the east greenland shelf is the e ux of calcium carbonate tic thought to be derived from glacial erosion of cretaceous calcareous mudstones a change in the regularity and spacing of carbonate e ux peaks at c 4 7 cal ka in jm96 1207 coincides with the onset of neoglacial cooling in the renland ice core d 18 o record we propose that the carbonate e ux peaks between 4 7 and 0 4 cal ka are related to sea surface coolings associated with increased e ux of polar water and sea ice in the east greenland current these peaks are synchronous with sea surface coolings interpreted from north atlantic deep sea cores but additional peaks centred around 2 4 and 3 8 cal ka in jm96 1207 suggest that the shelf site captures higher frequency events the data indicate that severe arctic sea ice events began in the neoglacial interval and that earlier holocene cool events in deep sea records are associated with other processes such as release of meltwater from residual glacier ice and glacial lakes

variability of fram strait ice flux and north atlantic oscillation we estimate the winter sea ice export through the fram strait using ice motion from satellite passive microwave data sea ice motion october may is obtained by tracking the displacement of common features in sequential 85 and 37 ghz brightness temperature fields the average winter area flux over the 18 year record 1978 1996 is 670 000 km2 7 of the area of the arctic ocean the winter area flux ranges from a minimum of 450 000 km2 in 1984 to a maximum of 906 000 km2 in 1995 the daily monthly and interannual variabilities of the ice area flux are high there is an upward trend in the ice area flux over the 18 year record the average winter volume flux over the winters of october 1990 through may 1995 is 1745 km3 ranging from a low of 1375 km3 in the 1990 flux to a high of 2791 km3 in 1994 the sea level pressure gradient across the fram strait explains more than 80 of the variance in the ice flux over the 18 year record we use the coefficients from the regression of the time series of area flux versus pressure gradient across the fram strait and ice thickness data to estimate the summer area and volume flux the average 12 month area flux and volume flux are 919 000 km2 and 2366 km3 we find a significant correlation r 0 86 between the area flux and positive phases of the north atlantic oscillation nao index over the months of december march correlation between our 5 years of volume flux estimates and the nao index gives r 0 56 during the high nao years a more intense icelandic low increases the gradient in the sea level pressure by almost 1 mbar across the fram strait thus increasing the atmospheric forcing on ice transport correlation is reduced during the negative nao years because of decreased dominance of this large scale atmospheric pattern on the sea level pressure gradient across the fram strait

atlantic water advection to the eastern fram strait multiproxy evidence for late holocene variability a multiproxy data set of an ams radiocarbon dated 46 cm long sediment core from the continental margin off western svalbard reveals multidecadal climatic variability during the past two millennia investigation of planktic and benthic stable isotopes planktic foraminiferal fauna and lithogenic parameters aims to unveil the atlantic water advection to the eastern fram strait by intensity temperatures and salinities atlantic water has been continuously present at the site over the last 2 000 years superimposed on the increase in sea ice icebergs a strengthened intensity of atlantic water inflow and seasonal ice free conditions were detected at 1000 to 1200 ad during the well known medieval climate anomaly mca however temperatures of the mca never exceeded those of the 20th century since 1400 ad significantly higher portions of ice rafted debris and high planktic foraminifer fluxes suggest that the site was located in the region of a seasonal highly fluctuating sea ice margin a sharp reduction in planktic foraminifer fluxes around 800 ad and after 1730 ad indicates cool summer conditions with major influence of sea ice icebergs high amounts of the subpolar planktic foraminifer species turborotalia quinqueloba in size fraction 150 250 m indicate strengthened atlantic water inflow to the eastern fram strait already after 1860 ad nevertheless surface conditions stayed cold well into the 20th century indicated by low planktic foraminiferal fluxes most likely at the beginning of the 20th century cold conditions of the terminating little ice age period persisted at the surface whereas warm and saline atlantic water already strengthened hereby subsiding below the cold upper mixed layer surface sediments with high abundances of subpolar planktic foraminifers indicate a strong inflow of atlantic water providing seasonal ice free conditions in the eastern fram strait during the last few decades

paleohydraulics of the last outburst flood from glacial lake agassiz and the 8200 bp cold event abstract during the last deglaciation of north america huge proglacial lakes formed along the southern margin of the laurentide ice sheet the largest of these was glacial lake agassiz which formed about 11 7 14 c kyr and drained into hudson bay about 7 7 14 c kyr 8 45 cal kyr overflow from these lakes was variably directed to the mississippi st lawrence and mackenzie drainage systems and it is thought that switches in routing were accompanied by a response in ocean circulation that produced abrupt climate events when the ice dam across hudson bay finally was breached a massive flood drained lake agassiz which was routed through hudson strait to the labrador sea in terms of stored water volume the largest reservoir was associated with the kinojevis level of lake agassiz for this maximum filling the impounded water volume available to produce floods is estimated as 40 000 151 000 km 3 depending on the location of the ice margin and route used the timing of this rapid release of stored freshwater just precedes the early holocene cooling event at 8 2 cal kyr bp we use the spring hutter theory to simulate flood hydrographs for floods that originate in subglacial drainage conduits and find that flood magnitude and duration are 5 sv and 0 5 yr multiple fillings and floods are possible as are single floods having a complex multipulse structure modelling results suggest that the outburst flood from lake agassiz may have terminated before the lake surface elevation dropped to sea level and that the flood ended when a stable drainage channel was established connecting lake agassiz to the tyrrell sea

decadal variability of sea surface temperatures off north iceland over the last 2000 years abstract ocean variability at decadal time scales remains poorly described partly because of the scarcity of high temporal resolution marine records here we present a reconstruction of sea surface temperatures ssts over the past two millennia at unprecedented temporal resolution 2 to 5 years from a marine core located off north iceland alkenone paleothermometry was used to infer sst variability and tephrochronology to build the age model spectral analyses of the sst signal indicate intermittent 20 25 year oscillations with periods of strong and weak power that are likely reflecting the ocean response to wind forcing presumably the north atlantic oscillation nao warmer ssts and paleo magnetic proxy data between 1000 and 1350 year a d overlapping the medieval warm period mwp suggest enhanced heat transport across the denmark strait by the north icelandic irminger current niic this is in contrast with the subsequent period which includes the little ice age lia showing continuous cooling towards the 20th century reduced niic flow through the denmark strait likely resulting from higher freshwater and sea ice export from the arctic would account for the observed colder conditions

variability of sea ice conditions in the fram strait over the past 30 000 years sea ice is a critical component of the climate and oceanographic system in the north atlantic ocean a biomarker record reveals millennial scale and glacial interglacial fluctuations in sea ice coverage in the northernmost atlantic ocean over the past 30 000 years

holocene history of drift ice in the northern north atlantic evidence for different spatial and temporal modes 1 we present new high resolution proxy data for the holocene history of drift ice off iceland based on the mineralogy of the 2 mm sediment fraction using quantitative x ray diffraction these new data bolstered by a comparison with published proxy records point to a long term increasing trend in drift ice input into the north atlantic from 6 to 5 ka toward the present day at sites influenced by the cold east greenland current this feature reflects the late holocene neoglacial or cooling period recorded in ice cores and further terrestrial archives on greenland in contrast a decrease in drift ice during the same period is recorded at sites underlying the north atlantic drift which may reflect a warming of this region the results document that holocene changes in iceberg rafting and sea ice advection did not occur uniformly across the north atlantic centennial scale climate variability in the north atlantic region over the last 4 kyr is linked to the observed changes in drift ice input increased drift ice may have played a role in the increase of cold intervals during the late holocene e g the little ice age cooling

mixing and convection in the greenland sea from a tracer release experiment convective vertical mixing in restricted areas of the subpolar oceans such as the greenland sea is thought to be the process responsible for forming much of the dense water of the ocean interior1 2 deep water formation varies substantially on annual and decadal timescales3 4 5 and responds to regional climate signals such as the north atlantic oscillation6 7 its variations may therefore give early warning of changes in the thermohaline circulation that may accompany climate change8 here we report direct measurements of vertical mixing by convection and by turbulence from a sulphur hexafluoride tracer release experiment in the central greenland sea gyre in summer we found rapid turbulent vertical mixing of about 1 1 cm2 s 1 in the following late winter part of the water column was mixed more vigorously by convection indicated by the rising and vertical redistribution of the tracer patch in the centre of the gyre at the same time mixing outside the gyre centre was only slightly greater than in summer the results suggest that about 10 of the water in the gyre centre was vertically transported in convective plumes which reached from the surface to at their deepest 1 200 1 400 m convection was limited to a very restricted area however and smaller volumes of water were transported to depth than previously estimated9 our results imply that it may be the rapid year round turbulent mixing rather than convection that dominates vertical mixing in the region as a whole

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

the westward turning branch of the west spitsbergen current a salinity temperature survey of fram strait in september 1985 extending to north of 81 n demonstrated the western branch of the west spitsbergen current flowing northwest and then west mainly south of 81 n there also was a southwestward recirculation from the eastern branch of the west spitsbergen current baroclinic flow of warm water northward through 81 n was negligible or zero some doubt is cast on past flow diagrams based on core analysis which show the western branch of the west spitsbergen current coursing northward to 83 n one of a probable line of mesoscale eddies is described in some detail

a novel chemical fossil of palaeo sea ice ip25 a unique and novel organic compound has been detected in sea ice samples from three locations in the canadian arctic thousands of kilometers apart it is likely that this biomarker is produced by diatoms living in the sea ice and we provide evidence which suggests that the compound a c25 monounsaturated hydrocarbon ip25 may be a specific sensitive and stable proxy for sea ice in sediments over at least the holocene since it has not been reported before we confirmed its identity by synthesis and used the synthesized compound as a reference for quantifying ip25 in a range of sediments from an east west transect in the canadian arctic the recent sediments are either seasonally covered with ice or have permanent ice cover older sediments containing ip25 have been dated using radiocarbon methods to at least 9000 yr if the concept proves generally applicable monitoring ip25 in further sediment cores along with other accepted proxies should allow movements in the position of the ice edge throughout the holocene at least to be better determined which is essential for accurate calibration of climate prediction models a similar approach for antarctic samples of ice and sediments would also seem worthwhile

a biomarker based reconstruction of sea ice conditions for the barents sea in recent centuries variations in sea ice occurrence for the barents sea since c ad 1700 have been determined by analysis of the abundance of the sea ice biomarker ip25 in three marine sediment box cores obtained from locations in the north southeast and southwest parts of the region depth age models for each core were established using excess 210pb activity profiles comparisons between these depth age models with those reported previously for the barents sea suggest that the proxy sea ice record may alternatively extend back to c ad 1500 1600 sedimentation accumulation rates and bulk densities were combined with ip 25 concentrations resulting in temporal changes to ip25 fluxes which have been interpreted in terms of sea ice variability the ip25 sea ice proxy data are also compared with other bulk organic geochemical parameters total organic carbon and c n ratios and with sediment particle size distributions the data indicate ice free conditions for the southwest barents sea for the past c 300 yr consistent

arctic north atlantic oscillation signature in holocene sea surface temperature trends as obtained from alkenone data 1 the variability in alkenone derived sea surface temperatures ssts in the north atlantic realm shows that a continuous sst decrease in the northeast atlantic from the early to the late holocene was accompanied by a persistent warming over the western subtropical atlantic the eastern mediterranean sea and the northern red sea based on the analysis of the instrumental data and of atmospheric general circulation model experiments we show that this variation in ssts during the holocene can be attributed to a continuous weakening of a northern hemisphere atmospheric circulation pattern similar to that of the arctic north atlantic oscillation

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

great salinity anomalies in the north atlantic abstract we revisited the great salinity anomaly of the 1970s gsa 70s dickson et al 1988 and documented the newly identified great salinity anomaly of the 1980s hence termed gsa 80s both propagated around the north atlantic in a similar fashion the advective mechanism initially proposed to explain the observed sequence of low salinity low temperature events during the gsa 70s apparently holds also for the gsa 80s the latter was successively observed in the west greenland current 1982 the labrador current 1983 the flemish pass 1984 near the charlie gibbs fracture zone 1984 1985 in the rockall channel 1985 south of iceland 1985 1988 in the north sea 1986 1987 norwegian sea 1987 1988 barents sea 1988 1989 and iceland sea 1989 1990 the advection speed of the gsa 80s seems to be greater than the one of the gsa 70s the 1980s anomaly reached the barents sea 6 to 7 years after peaking in the west greenland current while the 1970s anomaly traveled the same route in 8 to 10 years these anomalies however seem to be of different origin the gsa 70s was apparently boosted remotely by a freshwater sea ice pulse from the arctic via fram strait consequently the gsa 70s was accompanied by a large sea ice extent anomaly in the greenland and iceland seas which propagated into the labrador sea in contrast the gsa 80s was likely formed locally in the labrador sea baffin bay mainly because of the extremely severe winters of the early 1980s but supplemented with a possible contribution of the arctic freshwater outflow via the canadian archipelago facilitated by strong northerly winds which would have enhanced stability and ice formation this anomaly was also associated with a positive sea ice extent anomaly in the labrador sea baffin bay which however had no upstream precursor in the greenland sea thus the gsas are not necessarily caused solely by an increased export of freshwater and sea ice from the arctic via fram strait these results are corroborated by the early 1990s data when a new fresh cold anomaly was formed in the labrador sea and accompanied by a large positive sea ice extent anomaly the harsh winters of the early 1990s were however confined to the labrador sea baffin bay area while the atmospheric and oceanic conditions in the greenland iceland and irminger seas were normal the labrador sea baffin bay area appears therefore to play a key role in formation of gsas as well as in propagation of the gsas formed upstream a likely contribution of the enhanced canadian archipelago freshwater outflow to the gsa formation also seems to be significant two major modes of the gsa origin are thus identified remote generated by an enhanced arctic ocean freshwater export via either fram strait or the canadian archipelago and local resulting from severe winters in the labrador sea baffin bay both modes should be taken into account to model decadal variability of the coupled ocean ice atmosphere system in the north atlantic arctic basin

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

oxygen 18 16 variability in greenland snow and ice with 10 3 to 105 year time resolution the 3 km long greenland ice sheet project 2 gisp2 ice core presents a 100 000 year detailed oxygen isotope profile covering almost a full glacial interglacial cycle measuranents of isotopic fluctuations in snow frost and atmospheric water vapor samples collected during summer field seasons up to 20 0 are compatible with the large and abrupt 80 160 changes observed in accumulated tim snow pit 15 80 profiles from the gisp2 summit area however show rapid smoothing of the 180 160 signal near the surface beyond about 2 m depth the smoothedi5180 signal is fairly well preserved and can be interpreted in terms of average local weather conditions and climate the longer climate fluctuations also have regional and often global significance in the older part of the record corresponding to marine isotope stages mis 5a to 5d the effect of orbital climate forcing via the 19 and 23 kyr precession cycles and the 41 kyr obliquity cycle is obvious from the end ofmis 5a at about 75 000 years b p till the end of the glacial at the younger dryas preboreal transition at 11 650 years b p the o180 160 record shows frequent rapid switches between intermediate interstadial and low stadial values fourier spectra of the oscillations that are superimposed on the orbitally induced changes contain a strong periodicity at 1 5 kyr a broad peak at 4 0 kyr and additional shorter periods detailed comparison of the gisp2 180 160 record with the vostok antarctica 15d record pacific ocean foraminiferal 180 160 grande pile france tree pollen and insolation indicates that a counterpart to many of the rapid 180 160 fluctuations of gisp2 can be found in the other records and that the gisp2 isotopic changes clearly are the local expression of climate changes of worldwide extent correlation of events on the independent gisp2 and specmap time scales for the interval 10 000 50 000 years b p shows excellent chronometric agreement except possibly for the event labeled 3 1 the glacial to interglacial transition evidently started simultaneously in the arctic and the antarctic but its development and its expression in greenland isotopes was later suppressed by the influence of meltwater especially from the barents sea ice sheet on deep water formation and ocean circulation meltwaters from different ice sheets bordering the north atlantic also influenced ocean circulation during the bolling allerod interstadial complex and the younger dryas and led to a distinct development of european climate and greenland 180 160 values the holocene interval with long term stable mean isotopic values contains several fluauations with periods from years to millennia dominant is a 6 3 year oscillation with amplitude up to 3 to 4 0 periodicities of 11 and 210 years also found in the solar modulated records of the cosmogenic isotopes 1obe and 14c suggest solar processes as the cause of these cycles depression of180 160 values cooling by volcanic eruptions is observed in stacked gisp215 80 records but the effect is small and not likely to trigger major climate changes

the great salinity anomaly in the northern north atlantic 1968 1982 the widespread freshening of the upper 500 800m layer of the northern north atlantic which this paper describes represents one of the most persistent and extreme variations in global ocean climate yet observed in this century though a range of explanations have been advanced to explain this event including in situ changes in the surface moisture flux this paper describes the great salinity anomaly as largely though not entirely an advective event traceable around the atlantic subpolar gyre for over 14 years from its origins north of iceland in the mid to late 1960s until its return to the greenland sea in 1981 1982 the overall propagation speed around this subpolar gyre is estimated at about 3cm s 1 of the total salt deficit associated with the anomaly as it passed south along the labrador coast in 1971 1973 about 72 109 tonnes a deficit equivalent to about two thirds of this figure 47 109 tonnes ultimately passed through the faroe shetland channel to the barents sea arctic ocean and greenland sea during the mid 1970s possible effects on deep water formation and on the representativeness of historical section data are discussed

millennial scale variability in atlantic water advection to the nordic seas derived from holocene coccolith concentration records abstract abundance patterns of coccolith species in two holocene marine cores retrieved off norway and northern iceland are indicative of millennial scale modulations in the flow of the main norwegian atlantic current and secondary north iceland irminger current branches of the north atlantic drift to the nordic seas long term trends in coccolith abundance changes reflect major holocene steps in atlantic water transfer to the nordic seas at orbital scale with important constraints on the convective activity of the nordic seas that leads to the formation of the precursor water mass of north atlantic deep water millennial scale holocene episodes of increased advection of atlantic waters off norway are associated with enhanced winter precipitation over scandinavia increased sea salt fluxes over greenland and strengthened wind over iceland thereby suggesting a common atmospheric forcing the location and intensity of the westerlies and the associated changes in mid to high latitude pressure gradients our biotic data indicate an opposite pattern of atlantic water inflow at suborbital scale between the western denmark and eastern iceland scotland straits of the northern atlantic throughout the holocene this as supported by present observational and simulated data further highlights the role of atmospheric oscillations in the recent history of the north atlantic nordic seas water mass exchanges across the greenland scotland ridge such atmospheric processes are thought to explain the observed coupling between periods of excess export of arctic sea ice to the nordic seas and intervals of maximum inflow of atlantic water to the norwegian sea throughout the last 11 000 years

a multiproxy reconstruction of the evolution of deep and surface waters in the subarctic nordic seas over the last 30 000yr on the basis of various lithological mircopaleontological and isotopic proxy records covering the last 30 000 calendar years cal kyr the paleoenvironmental evolution of the deep and surface water circulation in the subarctic nordic seas was reconstructed for a climate interval characterized by intensive ice sheet growth and subsequent decay on the surrounding land masses the data reveal considerable temporal changes in the type of thermohaline circulation open water convection prevailed in the early record providing moisture for the fennoscandian barents ice sheets to grow until they reached the shelf break at 26 cal kyr and started to deliver high amounts of ice rafted debris ird into the ocean via melting icebergs low epibenthic 18o values and small sized subpolar foraminifera observed after 26 cal kyr may implicate that advection of atlantic water into the nordic seas occurred at the subsurface until 15 cal kyr although modern like surface and deep water conditions first developed at 13 5 cal kyr thermohaline circulation remained unstable switching between a subsurface and surface advection of atlantic water until 10 cal kyr when ird deposition and major input of meltwater ceased during this time two depletions in epibenthic 13c are recognized just before and after the younger dryas indicating a notable reduction in convectional processes despite an intermittent cooling at 8 cal kyr warmest surface conditions existed in the central nordic seas between 10 and 6 cal kyr however already after 7 cal kyr the present day situation gradually evolved verified by a strong water mass exchange with the arctic ocean and an intensifying deep convection as well as surface temperature decrease in the central nordic seas this process led to the development of the modern distribution of water masses and associated oceanographic fronts after 5 cal kyr and eventually to today s steep east west surface temperature gradient the time discrepancy between intensive vertical convection after 5 cal kyr but warmest surface temperatures already between 10 and 6 cal kyr strongly implicates that widespread postglacial surface warming in the nordic seas was not directly linked to the rates in deep water formation

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

diatom flux and species composition in the greenland sea and the norwegian sea in 1991 1992 abstract vertical diatom fluxes were investigated in sediment trap material from june 1991 to july 1992 from the greenland sea at 72 n 007 w and the norwegian sea at 70 n 000 e in order to determine seasonal species compositions and alterations that affect settling assemblages different hydrographical conditions including seasonal ice coverage are reflected in seasonal variations of total diatom flux and species composition the purpose of this study is to achieve a better understanding of pelagic and sedimentary processes the quantification of the annual diatom fluxes with respect to accumulation rates of underlying sediments is a suitable approach in reconstructing palaeoceanographic changes and their effects on the productivity of the oceans the influx of laterally advected material and the alteration of sedimenting assemblages due to silica dissolution are also considered in this approach a strong pulse like sedimentation pattern was observed in the greenland sea highest values of up to 7 7 10 6 valves m 2 d 1 were recorded during the summer second half of july 1991 allochthonous diatoms such as benthic and subtropical boreal as well as enriched autochthonous species found in the deep water trap indicate the sporadic occurrence of lateral advection and resuspension processes in the greenland sea in the norwegian sea low diatom flux was observed and three distinct sedimentation events could be differentiated at 500 m water depth at this site zooplankton grazing pressure during spring is known to have more influence on the phytoplankton stock than in the greenland sea which causes a delay in diatom accumulation this is evident from maximum values of 0 3 10 6 valves m 2 d 1 during november december 1991 significant enrichment of arctic diatom species suggests a transport from the greenland sea into the norwegian sea via deep currents the assemblages of diatom species that are preserved in underlying surface sediments reflect the local oceanographic conditions and are quite similar to the assemblages found in deep water traps from both regions however they do not necessarily reflect the composition of the main sedimentation event but rather the typical post bloom species composition with stronger silicified diatoms despite the absence of weakly silicified species due to silica dissolution diatom assemblages were useful in reconstructing modern and ancient oceanographic conditions

sea ice impact on long term particle flux in the greenland sea s is odden nordbukta region 1985 1996 five sediment traps deployed in the greenland sea at a depth of 500 m between 72 n and 75 n by the sonderforschungsbereich 313 kiel germany provide the necessary data to compare particle flux with ambient ice regimes sedimentation in this seasonally ice covered region is dependent upon the following three basic parameters 1 ice concentration 2 duration of ice cover and 3 distance from the ice edge these factors vary significantly with time and space we develop algorithms that provide annual sedimentation amounts for the area contained by 71 n to 76 n the greenland coast and 10 e for a severe ice year the area of seasonal ice cover and an 80 km wide band extending along the maximum extent of the ice edge the biological marginal ice zone bmiz combine to provide 92 of the total sedimentation for particulate organic carbon and silica this zone accounts for 89 each of the total sedimentation in a light ice year the respective percentages are 84 for dry weight 87 for particulate organic carbon and 81 for biogenic particulate silica these figures are slightly less than sedimentation for a severe ice year if the is odden nordbukta region is replaced by open ocean for purposes of comparison the bmiz out produces the open ocean for poc by a factor of 3 2 projecting the algorithms for the is odden nordbukta region to the rest of the greenland sea we conclude that the is odden nordbukta region is a substantial producer of sedimentation

a high resolution study of holocene paleoclimatic and paleoceanographic changes in the nordic seas 1 high resolution records from images core md95 2011 in the eastern norwegian sea provide evidence for relatively large and small scale high latitude climate variability throughout the holocene during the early and mid holocene a situation possibly driven by consistent stronger westerlies increased the eastward influence of arctic intermediate and near surface waters for the late holocene a relaxation of the atmospheric forcing resulted in increased influence of atlantic water the main changes in holocene climate show no obvious connection to changing solar irradiance and spectral analysis reveals no consistent signature for any periodic behavior of holocene climate at millennial or centennial timescales there are however indications of consistent multidecadal variability

recent and pleistocene carbonate dissolution in sediments of the norwegian greenland sea surface sediment samples from the norwegian greenland sea were investigated to reconstruct the spatial distribution of recent carbonate dissolution on the seafloor additionally carbonate dissolution records of ocean drilling program sites 985 and 987 are presented to outline the development of pleistocene carbonate preservation today well preserved carbonate tests can be observed along the inflow of warm atlantic surface water extending as far as into the northernmost norwegian greenland sea increased dissolution is indicated along the continental margins and in the deepest parts of the greenland basin factors favoring carbonate preservation were found to be supersaturation of the water column with respect to calcium carbonate high carbonate rain and probably excess alkalinity of bottom waters supplied by the arctic river discharge supralysoklinal dissolution is most important for recent carbonate dissolution in the norwegian greenland sea whereas the deepest parts of the greenland basin reaches the calcite saturation horizon pleistocene dissolution records show some prominent peaks of extreme carbonate dissolution during the brunhes chron carbonate dissolution maxima can be related to meltwater pulses which probably inhibited deep water formation in the norwegian greenland sea during deglaciation events long term severe carbonate dissolution is evident during the late matuyama chron this can be probably related to low carbonate rain due to a more eastwards located east greenland current and the nearly absence of the not yet polar adapted neogloboquadrina pachyderma sin during that period extreme dissolution events during the late matuyama indicate strongly reduced deep water formation

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

abrupt climate changes for iceland during the last millennium evidence from high resolution sea ice reconstructions a high resolution account of icelandic sea ice over the last millennium has been constructed using a novel proxy based on the presence in sediments of a biomarker ip25 produced by sea ice algae comparison with historical sea ice records demonstrates a strong correlation between documented sea ice occurrences and the ip25 proxy an excellent agreement is also observed between the ip25 record and a diatom based sea surface temperature reconstruction obtained from the same core and the crowley and lowery northern hemisphere temperature reconstruction using this approach we provide new historical sea ice data for periods where records are scarce or absent and evidence for abrupt changes to sea ice and or climate conditions around iceland during the little ice age

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

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

holocene climate variability as derived from alkenone sea surface temperature and coupled ocean atmosphere model experiments holocene climate modes are identified by the statistical analysis of reconstructed sea surface temperatures ssts from the tropical and north atlantic regions the leading mode of holocene sst variability in the tropical region indicates a rapid warming from the early to mid holocene followed by a relatively weak warming during the late holocene the dominant mode of the north atlantic region sst captures the transition from relatively warm cold conditions in the eastern north atlantic and the western mediterranean sea the northern red sea to relatively cold warm conditions in these regions from the early to late holocene this pattern of holocene sst variability resembles the signature of the arctic oscillation north atlantic oscillation ao nao the second mode of both tropical and north atlantic regions captures a warming towards the mid holocene and a subsequent cooling the dominant modes of holocene sst variability emphasize enhanced variability around 2300 and 1000 years the leading mode of the coupled tropical north atlantic holocene sst variability shows that an increase of tropical sst is accompanied by a decrease of sst in the eastern north atlantic an analogy with the instrumental period as well as the analysis of a long term integration of a coupled ocean atmosphere general circulation model suggest that the ao nao is one dominant mode of climate variability at millennial time scales

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

the arctic circumpolar boundary current abstract the main water transformations in the arctic mediterranean take place in the boundary current of atlantic water which crosses the greenland scotland ridge from the north atlantic into the eastern norwegian sea it enters and flows around the arctic ocean before it exits the arctic mediterranean as the east greenland current primarily through denmark strait on route it experiences numerous branchings and mergings by examining how the properties of this circumpolar boundary current evolve it is possible to identify and describe the processes causing the water mass transformations in the arctic mediterranean it is also possible to follow the arctic ocean deep waters as they spread into the nordic seas and eventually provide 40 of the overflow water supplying the north atlantic deep water

exotic pollen as an indicator of variable atmospheric circulation over the labrador sea region during the mid to late holocene variability in the abundance of exotic non native pollen in sediment cores has long been considered as a potential proxy for changing atmospheric circulation but the difficulty of gaining sufficient total exotic pollen and the incomplete under standing of atmospheric pollen transport patterns has hindered its application in light of recent advances in the study of pollen transport we present an exotic pollen record from two fjord sediment cores taken from the west placentia bay newfoundland and east narsaq sund greenland labrador sea as a basis for studying variations in regional atmospheric circulation the two cores cover the last ca 5500 years and indicate a shift in dominant spring summer air masses at ca 2000 southern greenland and 3000 cal a bp newfoundland transporting reduced concentrations of pollen from southerly and south westerly vegetation zones this may suggest a shift away from more dominantly zonal atmospheric circulation a feature of positive north atlantic oscillation years to more frequent meridional circulation these results support sea ice sea surface temperature proxy reconstructions from newfoundland investigated as part of the same project which also suggest increased winter atmospheric circulation during the early part of the time period studied in this region more positive north atlantic oscillation years and therefore more zonal atmospheric circulation are associated with increased atmospheric circulation in both the winter and the summer seasons copyright 2011 john wiley sons ltd