major pathways of atlantic water in the northern north atlantic and nordic seas toward arctic 1 the major pathways of near surface atlantic water in the northern north atlantic and nordic seas are identified as current speeds above 30 cm s using 1014 lagrangian drifters combined with previously published hydrography the inflow over the scotland greenland ridge and establishment of the two branch norwegian atlantic current nwac are described in light of the circulation in the northern north atlantic the western branch of the nwac appears as a jet in the polar front topographically guided from the iceland faroe front through the nordic seas toward fram strait the eastern branch starts as a shelf edge current above the irish scottish continental shelf and after passing through the faroe shetland channel it continues northward along the norwegian shelf edge toward the arctic with a branch bifurcating into the barents sea the nwac appears to maintain its two branch structure throughout the nordic seas with the atlantic water confined to a 200 600 km wide wedge

eemian early weichselian n s temperature gradients north atlantic nw europe abstract based on benthic marine organisms and or vegetation development at coastal sites in the eastern atlantic region temperature profiles of the last interglacial stage 5e and the early weichselian interstadial odderade stage 5a have been constructed from 40 to 80 degrees north the shape of the eemian summer temperature profile is very similar to the present but at all sites the eemian temperatures are a few degrees c warmer than present the odderade temperature conditions are very similar to the present both in the north on svalbard and in the south the nederlands france however in norway denmark and nw germany the odderade climate is much cooler than today sea surface temperature sst estimates inferred from planktonic foraminifera from the norwegian sea and the north atlantic show the same temperature trends as those inferred from the coastal sections these observations confirm the close relationship between western european climate and north atlantic surface conditions based on comparison between these temperature trends and insolation data we suggest that the development to an interstadial or interglacial type of climate in w europe is controlled by orbital forcing furthermore these results stress that quaternary stratigraphers working at high and low latitudes should be especially careful when using climatic inferences as a basis for correlation to interglacials or interstadials

spatial and temporal distribution of holocene temperature maxima in the northern nordic seas interplay of atlantic arctic and polar water masses abstract subsurface and bottom water temperatures on the western shelf of svalbard at 79 n are reconstructed in order to investigate the relative influence of warm atlantic water cold arctic polar water and meltwater during the holocene the study is based on sediment core np05 21gc which has been investigated for the distribution of planktic foraminiferal species oxygen and carbon isotopes measured in benthic and planktic foraminifera and subsurface and bottom water temperatures calculated from transfer functions the data are compared to several other records from the western margin of svalbard the results indicate that until 9600 years bp the water column west of svalbard was stratified by a pycnocline situated at a water depth of c 100 m on the shelf and at c 30 m on the slope the water mass above the pycnocline consisted of cold arctic polar water and meltwater whereas the water mass below the pycnocline consisted of warm atlantic water after 9600 the supply of arctic polar water and meltwater diminished weakening the pycnocline and from 9000 to 6000 years bp warm atlantic water occupied the entire water column the upper and deeper water masses experienced different holocene temperature maxima in the atlantic water the temperature maximum occurred during the early holocene 11 500 8200 years bp only interrupted by the cold pre boreal oscillation c 11 300 10 800 years bp the maximum was followed by a gradual temperature decrease until c 5000 years bp in the upper water masses the temperature maximum occurred from c 9000 6000 years bp the timing of the maximum here is influenced by the decreasing supply of cold arctic polar water versus the increasing dominance of atlantic water the temperatures of both the surface and bottom water decreased to a minimum from c 5000 2000 years bp during the last 2000 years conditions have been increasingly unstable although with slightly increasing subsurface temperatures

variability of the north atlantic current during the last 2000 years based on shelf bottom water and sea surface temperatures along an open ocean shallow marine transect in western europe marine localities on the west european shelf have been studied to reconstruct the nearshore palaeoceanography of the last two millennia the sites form a transect from the iberian margin northeastward via scotland to western norway and iceland proxies used for palaeoclimatic reconstructions include stable isotopes benthic and planktonic foraminfera diatoms dinoflagellates as well as geochemical and sedimentological parameters major changes as well as long term trends in oceanographic conditions are observed in the records including a general cooling trend through much of the last millennium there is a clear linkage between the atmospheric processes and the oceanic circulation and the ocean temperature variability in the records can be correlated with the so called mediaeval warm period and little ice age these oscillations are however by no means unique within the last two millennia as an example sea surface temperatures to the north of iceland and on the iberian margin were higher in the roman warm period than at any time during the mediaeval warm period however the palaeoceanographic record generally supports a distinct cooling at the transition between the mediaeval warm period and the little ice age while a number of records indicate a warming of coastal and shelf waters during the last 200 years the twentieth century does not appear to be unusual when the proxy records spanning the last two millennia are examined

benthonic foraminiferal distributions and quantitative transfer functions for the northwest european continental margin abstract a database of benthonic foraminiferal data from 298 sediment surface samples from the northwest european ireland to svalbard and iceland margin has been compiled samples deeper than 500 m on the continental slope and shallower than 30 m in coastal areas are not included bottom water temperatures at the sites range between 1 and 12 5 c and salinity between 33 5 and 35 5 detrended correspondence analyses of percentage values of 65 benthonic foraminifera taxa from 260 of the samples show a strong statistically significant relationship between modern foraminiferal assemblages and summer temperature and salinity utilising weighted averaging partial least square regression transfer functions for summer bottom water temperature ts and salinity ss have been developed the transfer functions have relatively low root mean square errors of prediction expressed as a percentage of the range of the modern environmental gradient sampled for ts 3 9 and for ss 9 02 compared to transfer functions developed for other proxies which commonly range from 8 to 20 the distributions of benthonic foraminifera species are dependent on other factors than salinity and temperature such as nutrients substrate turbidity current regime different biological factors different depth related factors etc the present analyses demonstrate that for this group as for most other groups there is an overall but not necessarily direct relationship with distribution and abundance and temperature and salinity conditions the transfer functions have been tested on a late glacial holocene data set and an eemian early weichselian data set from the eastern north sea region these experiments suggest that transfer functions on benthonic foraminifera can be a useful new tool in palaeoceanographic and palaeoenvironmental work along the european north atlantic seaboard

a climatic trigger for the giant troll pockmark field in the northern north sea abstract pockmarks are seafloor craters usually formed during methane release on continental margins however the mechanisms behind their formation and dynamics remain elusive here we report detailed investigations on one of the world s largest pockmark fields located in the troll region in the northern north sea seafloor investigations show that 7000 pockmarks are present in a 600 km2 area a similar density of pockmarks is likely present over a 15 000 km2 region outside our study area based on extensive monitoring coring geophysical and geochemical analyses no indications of active gas seepage were found still geochemical data from carbonate blocks collected from these pockmarks indicate a methanogenic origin linked to gas hydrate dissociation and past fluid venting at the seafloor we have dated the carbonates using the u th method in order to constrain the pockmark formation the carbonates gave an isochron age of 9 59 1 38 ka i e belonging to the initial holocene moreover radiocarbon dating of microfossils in the sediments inside the pockmarks is consistent with the ages derived from the carbonates based on pressure and temperature modelling we show that the last deglaciation could have triggered dissociation of gas hydrates present in the region of the northern part of the norwegian channel causing degassing of 0 26 mtch4 km2 at the seafloor our results stress the importance of external climatic forcing of the dynamics of the seafloor and the role of the rapid warming following the younger dryas in pacing the marine gas hydrate reservoir

late holocene ca 4 ka marine and terrestrial environmental change in reykjarfjordur north iceland climate and or settlement core b997 328pc is from the landward side of a 100 m deep basin in reykjarfjordur a small fjord on the north coast of the northwest peninsula of iceland this is an area that can be severely affected by incursions of polar sea ice but has not suffered marked land erosion during the settlement period the core is 422 cm in length and consists principally of fine grained muds with in situ molluscs eleven ams 14c dates on molluscs indicate a constant sediment accumulation rate of ca 1 cm 10 yr 1 for the last 4280 50 yr bp we measured and derived a variety of proxies for indications of changes in the nearshore environment these included physical properties and grain size mass accumulation rates micropalaeontology pollen and foraminifera multivariate analysis and constrained clustering were used to define major changes in the proxies in several parameters the major change in the fjord environment occurred close to 1000 14c yr ago thus approximately coincident with the onset of the settlement of iceland other changes are noted at around 1600 and 3400 14c yr ago betula pollen disappears from the record ca 1500 yr bp and there are peaks in marine productivity occurring ca 2 and 3 4 ka a major decline in carbonate accumulation and a sharp increase in the cold water benthic foraminifer elphidium excavatum forma clavata 400 yr ago represents the local marine signature of the little ice age none of the changes in our data can be explained adequately by a simple call to land use practices and an increase in land to sea transport but both the pollen and foraminiferal records indicate a decrease and even loss of warm elements in both flora and fauna over the past 4 kyr copyright 2001 john wiley sons ltd

research paperreprint of reconstruction of inflow of atlantic water to isfjorden svalbard during the holocene correlation to climate and seasonality the distribution patterns of benthic foraminifera faunas stable isotopes and ice rafted debris ird have been studied in piston core jm98 845 pc from isfjorden western svalbard to reconstruct changes in the flow of atlantic water during the holocene interglacial the paleoenvironmental conditions in isfjorden and the inflow of the atlantic water followed closely the changes in insolation with strong seasonality in the early holocene and weaker seasonality in the middle to late holocene a summer temperature maximum of the bottom water occurred in the early holocene 10 500 c 8200 years bp cooling began at 9000 years bp with stepwise coolings at c 8200 7400 and 4000 years bp the cooling correlated with an increase in ice rafting and increased influence of polar water and seasonal sea ice cover between 4000 and 2000 years bp bottom water temperatures reached a minimum after 2000 years bp episodic inflow of warmer atlantic water at the bottom of the fjord occurred and conditions became more unstable the data indicate close interaction of the flow of atlantic water with the development of the terrestrial climate and the amount of polar meltwater and sea ice

initiation of fennoscandian ice sheet retreat during the last deglaciation although the retreat history of the southern margin of the laurentide ice sheet during the last deglaciation has been well known for several decades1 3 and recently supported by evidence from accelerator mass spectrometer ams radiocarbon dating of meltwater in the gulf of mexico4 and the north atlantic subtropical gyre5 the retreat history of the fennoscandian ice sheet before 13kyr ago is still poorly documented from ams 14c dating and isotopic analysis of a rapidly deposited series of supra till sediments in the norwegian channel north sea we find that the southern margin of the fennoscandian ice sheet was in retreat by 15 kyr bp before present approximately 2 000 yr earlier than previously supposed oxygen isotope analyses in the channel sediments confirm earlier evidence from deep norwegian sea sediment cores for low salinity due to ice sheet discharge beginning 15 14 5 kyr bp ref 6 recent recalibration of the 14c timescale indicates that the onset of deglaciation within the norwegian sea occurred during an interval of rapidly increasing summer insolation beginning 18 000 calendar yr bp ref 7 suggesting that ice sheet retreat may have been caused by increasing insolation acting on a particularly climate sensitive ice sheet configuration fresh water and icebergs discharged into the norwegian sea at this time reached the north atlantic and may have contributed to a brief interval of extreme oceanic cooling8 and reduced production of north atlantic deep water9 10 these factors may also have helped to briefly reverse the deglaciation trend erie interstade already underway in north america

palaeoceanographic and environmental changes in the eastern fram strait during the last 14 000 years based on benthic and planktonic foraminifera abstract benthic and planktonic foraminifera stable isotopes and other geochemical and sedimentological parameters have been investigated in a sediment core from vestnesa ridge 79 n nw svalbard margin 1300 m water depth in order to reconstruct the palaeoceanographic and palaeoenvironmental evolution of the eastern fram strait during the last 14 000 years our multiproxy data and in particular our high resolution benthic foraminiferal record allow a detailed reconstruction of the intermediate water flow in the eastern fram strait during the bolling allerod warm interstadials the high proportion of the benthic atlantic species cassidulina neoteretis suggests the presence of chilled atlantic derived water at the bottom of the vestnesa ridge while the dominance of the polar planktonic species neogloboquadrina pachyderma s indicates cold polar surface conditions during the younger dryas cold stadial the inflow of atlantic derived water was weakened and of lower temperature compared to the previous interval as suggested by the increase in the glacio marine indicator cassidulina reniforme and the lower percentages of c neoteretis after 11 000 cal yr bp the abrupt increase in relative abundance of the benthic species cibicides wuellerstorfi and oridorsalis umbonatus indicates a shift to interglacial conditions with deep convection and generation of cold intermediate water warm surface water conditions were finally established at about 10 300 cal yr bp when turborotalita quinqueloba became the dominant planktonic species generally warmer conditions than today were recorded in the middle holocene with a mild cooling at about 8200 cal yr bp and a more pronounced cool interval with an abrupt decrease in t quinqueloba between 7000 and 6200 cal yr bp cold climatic conditions were established around 4100 cal yr bp when n pachyderma s became again the dominant species and the polar benthic species cribroelphidium excavatum appeared

editorial late holocene oceanographic and climate change from the western european margin the results of the holsmeer project the underlying aim of the holsmeer project has been to improve our understanding of natural climate variability through the search for interpretation and quantification of climatic variability in very high resolution shallow marine records from atlantic europe covering the last 2000 years this has been achieved through detailed analyses of a series of coastal and shallow marine sites spanning the atlantic seaboard from iberia to western norway and extending across to iceland holsmeer partners have documented pronounced instability in the thermohaline circulation thc during the period immediately prior to the recent significant anthropogenic impact on the environment for the first time we have been able to document that these changes in the coastal ocean are correlated with significant changes in terrestrial palaeoclimate proxies notably during the last 1000 years the notable changes are the significance of warm sea surface temperatures sst associated with active thc between ad 700 and 1000 a

recent coastal evolution and sea level rise setiu wetland peninsular malaysia abstract sea level reconstructions based on foraminiferal assemblage data are common for temperate salt marsh settings in comparison the widespread mangrove swamps of equatorial to subtropical settings have received considerably less attention due to enhanced taphonomic loss of specimens extensive bioturbation abundant infaunal foraminifera and irregular intertidal topography the tropics however provide the best possible estimate of eustatic function and thus are important for testing earth ice models in this paper we use foraminiferal data in a chronologic framework provided by optically stimulated luminescence radiocarbon and pb 210 age estimates to determine coastal evolution and rates of sea level rise in the setiu wetland of northeastern peninsular malaysia on the western margin of the southern south china sea over the past ca 200 years foraminiferal data from three surface transects across fringing mangrove swamps were used to interpret four cores from mid to high mangrove swamp settings patterns of foraminiferal distribution were determined by correspondence analysis canonical correspondence analysis and detrended canonical correspondence analysis of dead assemblage data we used weighted averaging as the transfer function model to reconstruct sea level curves for the cores and to provide a composite reconstruction for the last ca 200 years based on one c 14 estimate sea level rose during the 19th century at 1 26 mm yr 1 the rate increased to 3 2 0 6 mm yr 1 around 1900 ce roughly coincident with rate increases recorded globally however the 20th century rate in the setiu wetland is considerably greater than that of global estimates ca 1 8 mm yr 1 for this period rates of sea level rise in the gulf of thailand immediately to the north of the setiu wetland determined from gps corrected tide gauge data and multi satellite altimetry are geographically variable but also greater than the global rate the data from the setiu wetland provide the first foraminifera based sea level reconstruction of the past few hundred years from the southeastern south china sea scs and they represent the first time the early 20th century increase in rate of sea level rise has been identified using proxy foraminiferal data in an equatorial setting

palynological evidence of climatic and oceanographic changes in the north sea during the last deglaciation abstract palynological analyses performed on cores from the norwegian channel troll 8903 led to reconstruction of the late glacial variations in sea surface conditions using dinoflagellate cyst data and permitted direct correlation with the vegetation history of northwestern europe derived from pollen assemblages by 15 000 yr b p ice rapidly receded from the norwegian shelf and relatively warm summer conditions prevailed in surface waters a first late glacial cooling marked by extensive seasonal sea ice cover is dated at ca 13 600 13 00014c yr b p which coincides with the oldest dryas interval during the bolling allerod interval a rise in sea surface temperature both in february up to 3 c and august up to 15 c led to the establishment of ice free conditions in the northern north sea while pollen data reveal a densification of the vegetation cover the beginning of the younger dryas interval is marked by an increase in nonarboreal pollen input indicative of the opening of the forest vegetation cover concomitant with a cooling of surface waters during winter and development of sea ice cover however sea surface conditions remained relatively warm in summer until about 10 300 yr b p when extremely cold conditions and extensive sea ice cover developed up to 7 months yr improving conditions are recorded in surface waters by 10 100 yr b p a few hundred years before the development of forest cover onshore as shown by the pollen record such a discrepancy between marine and terrestrial indicators at the end of younger dryas time suggests a delayed response of the vegetation to regional climate warming

north atlantic nordic seas exchanges abstract the northeastern part of the north atlantic is unique in the sense that it is much warmer in the surface than other ocean areas at similar latitudes the main reason for this is the large northward transport of heat that extends to high latitudes and crosses the greenland scotland ridge to enter the nordic seas and the arctic there the warm atlantic water is converted to colder water masses that return southwards over the ridge partly as surface outflows and partly as overflows through the deep passages across the ridge in this paper the state of knowledge on the exchanges especially across the eastern part of the greenland scotland ridge is reviewed based on results from the ices nansen north atlantic norwegian sea exchanges project from the nordic woce project and from other sources the accumulated evidence allows us to describe the exchanges in fair detail the origins of the waters the patterns of their flow towards and over the ridge and their ultimate fate there is also increasing information on temporal variations of the exchanges although dynamical changes are still not well understood quantitative estimates for the volume transport of most of the overflow branches seem reasonably well established and transport measurements of the atlantic inflows to the nordic seas are approaching acceptable levels of confidence which allows preliminary budgets to be presented the deep overflows are driven by pressure gradients set up by the formation of deep and intermediate water the dominance of deep overflows over surface outflows in the water budget argues that this thermohaline forcing also dominates over direct wind stress and estuarine forcing in driving the atlantic water inflow across the greenland scotland ridge while wind stress seems to influence the characteristics and distribution of the atlantic water north of the ridge

centennial scale benthic foraminiferal record of late holocene oceanographic variability in disko bugt west greenland a new centennial scale benthic foraminiferal record of late holocene climate variability and oceanographic changes off west greenland disko bugt highlights substantial subsurface water mass changes e g temperature and salinity of the west greenland current wgc over the past 3 6 ka bp benthic foraminifera reveal a long term late holocene cooling trend which may be attributed to increased advection of cold low salinity water masses derived from the east greenland current egc cooling becomes most pronounced from c 1 7 ka bp onwards at this point the calcareous atlantic benthic foraminiferal fauna decrease significantly and is replaced by an agglutinated arctic fauna superimposed on this cooling trend centennial scale variability in the wgc reveals a marked cold phase at c 2 5 ka bp which may correspond to the 2 7 ka bp cooling event recorded in marine and terrestrial archives elsewhere in the north atlantic region a warm phase recognized at c 1 8 ka bp is likely to correspond to the roman warm period and represents the warmest bottom water conditions during the time period of the medieval climate anomaly we observe only a slight warming of the wgc a progressively more dominant cold water contribution from the egc on the wgc is documented by the prominent rise in abundance of agglutinated arctic water species from 0 9 ka bp onwards this cooling event culminates at c 0 3 ka bp and represents the coldest episode of the little ice age gradually increased influence of cold low salinity water masses derived from the egc may be linked to enhanced advection of polar and arctic water by the egc these changes are possibly associated with a reported shift in the large scale north atlantic oscillation atmospheric circulation pattern towards a more frequent negative north atlantic oscillation mode during the late holocene

holocene temperature and salinity variability of the atlantic water inflow to the nordic seas piston core link14 from 346 m water depth on the eastern shelf of the faroe islands in the faroe shetland channel has been investigated in order to reconstruct temperature and salinity changes of the atlantic surface water during the holocene we have analyzed the distribution of benthic and planktic foraminifera stable isotopes and calculated by transfer functions absolute surface subsurface and bottom water temperatures and salinities the summer sea surface temperature sst shows a stepwise decrease from an early holocene warm phase 10 300 8300 yr bp with temperatures around 12 c over a mid holocene cooler phase 8300 4000 yr bp to a late holocene relatively cool phase with sst around or slightly below 11 c bottom water temperatures at 346 m water depth show much less variation than the sst the late holocene sea surface cooling was probably caused by increase in the influence of the polar east icelandic current a distinct decrease in the subsurface salinity from about 8300 to 6800 yr bp is proba

comment on relationships between melt induced rheological transitions and finite strain observations from host rock pendants of the tuolumne intrusive suite sierra nevada california by markus albertz

simmax a modern analog technique to deduce atlantic sea surface temperatures from planktonic foraminifera in deep sea sediments we present a data set of 738 planktonic foraminiferal species counts from sediment surface samples of the eastern north atlantic and the south atlantic between 87 n and 40 s 35 e and 60 w including published climate long range investigation mapping and prediction climap data these species counts are linked to levitus s 1982 modern water temperature data for the four caloric seasons four depth ranges 0 30 50 and 75 m and the combined means of those depth ranges the relation between planktonic foraminiferal assemblages and sea surface temperature sst data is estimated using the newly developed simmax technique which is an acronym for a modern analog technique mat with a similarity index based on 1 the scalar product of the normalized faunal percentages and 2 a weighting procedure of the modern analog s ssts according to the inverse geographical distances of the most similar samples compared to the classical climap transfer technique and conventional mat techniques simmax provides a more confident reconstruction of paleo ssts correlation coefficient is 0 994 for the caloric winter and 0 993 for caloric summer the standard deviation of the residuals is 0 90 c for caloric winter and 0 96 c for caloric summer at 0 m water depth the sst estimates reach optimum stability standard deviation of the residuals is 0 88 c at the average 0 to 75 m water depth our extensive database provides sst estimates over a range of 1 4 to 27 2 c for caloric winter and 0 4 to 28 6 c for caloric summer allowing sst estimates which are especially valuable for the high latitude atlantic during glacial times an electronic supplement of this material may be obtained on adiskette or anonymous ftp from kosmos agu org login toagu s ftp account using anonymous as the username and guestas the password go to the right directory by typing cd append typels to see what files are available type get and the name of the file toget it finally type exit to leave the system paper 95pa01743 simmax a modern analog technique to deduce atlantic sea surfacetemperatures from planktonic foraminifera in deep sea sediments uwepflaumann josette duprat claude pujol and laurent d labeyrie diskette may be ordered from american geophysical union 2000florida avenue n w washington dc 20009 payment mustaccompany order

water mass exchange between the nordic seas and the arctic ocean on millennial timescale during mis 4 mis 2 1 the climate of the last glaciation circa 65 000 25 000 years ago was interrupted by about 15 abrupt temperature fluctuations the so called dansgaard oeschger events consisting of warm interstadials and cold stadials recorded in greenland ice cores the largest fluctuations occur in the north atlantic region but they have been registered over the most of the world the events are linked to changes in deep water formation in the nordic seas and north atlantic disrupting the thermohaline circulation yet dansgaard oeschger events have so far not been recorded north of the convection areas in the central nordic seas and it is not known if they affected the water exchange between the nordic seas and the arctic ocean in this study we analyze core jm05 31gc from the northern fram strait at the very entrance to the arctic ocean the core contains sediments from marine isotope stages miss 4 2 the results show millennial timescale shifts in all the investigated proxies including the distribution of planktonic and benthic foraminifera planktonic and benthic oxygen and carbon isotopes and several sedimentological parameters in jm05 31gc the interstadials are characterized by relatively high surface and low bottom water temperatures low content of ice rafted debris and well ventilated bottom water stadials are characterized by the presence of icebergs and decreasing surface water and increasing bottom water temperatures due to increased inflow of atlantic subsurface water ventilation decreased during heinrich events and most stadials the results show that the dansgaard oeschger events strongly affected the water exchange between the nordic seas and the arctic ocean

quaternary glaciations in southern fennoscandia evidence from southwestern norway and the northern north sea region abstract based on records from the northern north sea and southern norway quaternary fennoscandian glaciations are described and discussed maximum glaciation defined as the presence of shelf edge glaciation an ice stream flowing out of the norwegian channel and most likely an ice divide over the central part of fennoscandia sweden gulf of bothnia occurred for the first time in the late cenozoic at ca 1 1 myr the fedje glaciation this glaciation was followed by a ca 600 kyr period with at least two glaciations with ice extension somewhat larger than the younger dryas event in the region the first maximum glaciation of the bruhnes chron was during isotope stage 12 and was followed by repeated maximum glaciations within each of the light isotopic stages until stage 2 during the weichselian the southwestern part of the fennoscandian ice sheet reached maximum position three times sometime between 22 and 28 37 and 50 and 60 and 80 ka limited glaciations probably occurred during stadials between the early and middle weichselian interstadials between 500 ka and 1 1 myr and most likely also prior to 1 1 myr deep norwegian sea ice rafted detritus ird records reflecting contributions from several different ice sheets fennoscandian barents sea iceland and greenland each with large variations in history of ice extent to their respective margins yet to some degree they reflect the glaciation of the northern north sea region with an increasing ird input around 1 1 myr and a relatively low input of north sea components during some cycles around the b m boundary maximum glaciations occurred during insolation minima in the earlier part of the middle pleistocene however not all such minima are reflected by maximum glaciation in southern parts of fennoscandia the relatively poor chronological control and non continuous character of the data on weichselian interstadials stadials precludes a clear relationship to atmospheric changes recorded in greenland ice cores as well as to precession and or obliquity cycles in insolation

the last 18 kyr fluctuations in norwegian sea surface conditions and implications for the magnitude of climatic change evidence from the north sea a combined record of three cores spanning the last 18 kyr from the northern north sea is investigated for content of benthic and planktonic foraminifera and stable oxygen isotopes the paleoenvironmental development through this time period shows an early deglaciation 18 14 4 ka and the younger dryas 12 7 11 5 ka characterized by arctic polar conditions and increased ice rafting in the norwegian channel during the bolling allerod period warm sea surface temperature 9 c conditions similar to present conditions are inferred while bottom waters stayed cold 0 1 c with normal salinity the bolling allerod period is interrupted twice at 13 9 13 6 ka older dryas and at 13 0 12 8 ka inter allerod cooling period by reductions in sea surface temperatures and increased sea ice cover the beginning of the holocene period is marked by increases in surface and bottom water temperature superimposed on the broad climatic changes through the holocene a series of short lived oscillations in the ocean circulation are recorded the amplitude of these holocene events appears larger in the early holocene prior to 8 ka than compared with the remaining part of the holocene this amplification can possibly be attributed to a general increased freshwater budget in the north atlantic at this time during the final stages of the deglaciation of the laurentide and scandinavian ice sheets

mid to late holocene strengthening of the east greenland current linked to warm subsurface atlantic water the relatively fresh and cold east greenland current egc connects the arctic with the subpolar north atlantic ocean its strength and influence on the freshwater balance in the north atlantic affects both the subpolar gyre dynamics and deep convection in the labrador sea enhanced freshwater and sea ice expansion in the subpolar north atlantic is suggested to modify the northward heat transport within the north atlantic current high resolution palaeoceanographic reconstructions based on planktic and benthic foraminifera assemblage data from the central east greenland shelf foster bugt reveal distinct centennial to millennial scale oceanographic variability that relates to climatic changes during the mid to late holocene the last c 6 3 ka bp our data highlight intervals of cooling and freshening of the polar surface egc waters that accompany warming in the subsurface atlantic waters which are a combination of chilled atlantic intermediate water aiw from the arctic ocean and of the return atlantic current rac from the west spitsbergen current wsc mid holocene thermal optimum conditions prevailed until c 4 5 ka bp a thin absent surface polar water layer low drift sea ice occurrence and strong contribution of recirculating warm atlantic waters at the subsurface suggest a relatively weak egc during this period subsequently between 1 4 and 4 5 ka bp the water column became well stratified as the surface polar water layer thickened and cooled indicating a strong egc this egc strengthening parallelled enhanced subsurface chilled aiw contribution from the arctic ocean after c 4 5 ka bp which culminated from 1 4 to 2 3 ka bp this coincides with warming identified in earlier work of the north atlantic current the irminger current and the west greenland current we link the enhanced contribution of chilled atlantic water during this period to the time of the roman warm period the observed warming offshore east greenland centred at c 1 8 ka bp likely occurred in response to changes in the interactions of i a weakened subpolar gyre ii increased northward heat advection in the north atlantic current and iii a predominant positive north atlantic and arctic oscillation mode prevailing during the time of the roman warm period

holocene variability of the north atlantic irminger current on the south and northwest shelf of iceland abstract the irminger current ic transports heat and nutrients to the icelandic shelf and its fluctuations are strongly linked to variations in the strength of the north atlantic surface flow from the south by using benthic foraminiferal assemblages and their stable isotopic composition in two marine sediment cores located in the pathway of the ic on the west iceland shelf we were able to derive bottom water temperature estimates at a 100 year resolution and define the temperature difference between the core sites throughout the holocene these are the first transfer function bottom water temperatures presented from the icelandic shelf based on benthic foraminiferal assemblages our findings demonstrate a delayed holocene thermal maximum in the marine current system around iceland compared to the northern hemisphere summer insolation receipts the maximum heat transport in the ic occurred between 8 and 4 ka years later than some previous records report a reconstruction of the ambient seawater 18o based on paired samples of c2 transfer function temperature estimates and oxygen isotopic composition indicates repeated freshwater input to the n atlantic inflow in the early holocene impacting the current system before 8 ka two fundamental regime shifts are evident in the paleoceanography and foraminiferal properties during the holocene occurring around 8 ka towards more stable conditions and again around 4 ka towards more unstable conditions increasing fluctuation with similarities to the great salinity anomaly in the 1970s occur after 4 ka

long term stability in the production of a nw mediterranean posidonia oceanica l delile meadow abstract long term changes in leaf net production of the seagrass posidonia oceanica l delile and in the irradiance arriving at the meadow canopy were investigated in a nw mediterranean meadow using a palaeoecological approach we conducted in situ shade experiments to find the relationships between the carbon stable isotope ratio 13c of plant tissues leaf net production and ambient irradiance the relationships were highly significant and fitted the michaelis menten equation and power functions these functions were used to reconstruct light and net production using the 13c of p oceanica detritus as a palaeoecological proxy along a 150 cm core of p oceanica matte a peat like deposit formed by this endemic seagrass species the 13c values of sheath detritus along the core i e the net leaf production showed a weak but significant decrease towards the present time r 0 308 p 0 02 probably as a result of 1 an increase in dic availability and or 2 a progressive change in the carbon isotopic signature of dic both of which are consistent with a rise in anthropogenic atmospheric co2 the canopy irradiance reconstructed for the last 1200 years showed a mean value of 128 e m 2 s 1 with a range of 12 5 280 e m 2 s 1 the reconstruction of the net leaf production for the same period yielded a mean value of 2 5 mg dw day 1 shoot 1 with a range of 2 0 2 7 mg dw day 1 shoot 1 both ranges are within the values reported in the literature for present day studies the absence of significant fluctuations or sudden changes through time suggests remarkable ecosystem stability during the last millennium

surface and sub surface multi proxy reconstruction of middle to late holocene palaeoceanographic changes in disko bugt west greenland we present new surface water proxy records of meltwater production alkenone derived relative sea surface temperature diatom alkenones and sea ice diatoms changes from the disko bugt area off central west greenland we combine these new surface water reconstructions with published proxy records benthic foraminifera bottom water proxy dinocyst assemblages surface water proxy along with atmospheric temperature from greenland ice core and greenland lake records this multi proxy approach allows us to reconstruct centennial scale middle to late holocene palaeoenvironmental evolution of disko bugt and the western greenland coastal region with more detail than previously available combining surface and bottom water proxies identifies the coupling between ocean circulation west greenland current conditions the atmosphere and the greenland ice sheet centennial to millennial scale changes in the wider north atlantic region were accompanied by variations in the west greenland current wgc during periods of relatively warm wgc increased surface air temperature over western greenland led to ice sheet retreat and significant meltwater flux in contrast during periods of cold wgc atmospheric cooling resulted in glacier advances we also identify potential linkages between the palaeoceanography of the disko bugt region and key changes in the history of human occupation cooler oceanographic conditions at 3 5 ka bp support the view that the saqqaq culture left disko bugt due to deteriorating climatic conditions the cause of the disappearance of the dorset culture is unclear but the new data presented here indicate that it may be linked to a significant increase in meltwater flux which caused cold and unstable coastal conditions at ca 2 ka bp the subsequent settlement of the norse occurred at the same time as climatic amelioration during the medieval climate anomaly and their disappearance may be related to harsher conditions at the beginning of the little ice age

arctic planktic foraminiferal assemblages implications for subsurface temperature reconstructions abstract earlier reconstructions of the inflow of atlantic water to arctic and subarctic oceans based on foraminiferal proxy data have been obstructed by uncertain quantitative reconstructions of sea surface and subsurface temperatures in this study surface sediment samples with undisturbed sediment water interface from polar north atlantic and barents sea were retrieved and prepared at the size fractions from 100 m to 1000 m the foraminiferal analyses show that neogloboquadrina pachyderma constitutes 96 99 of the fauna in arctic and polar surface water masses the same result is obtained when investigating the 150 m size fraction however in arctic areas influenced by atlantic water additional faunal information is obtained when using the smaller 100 m size fraction in these areas n pachyderma is reduced to about 50 and the relatively small species turborotalita quinqueloba becomes very frequent this also applies to the coastal water masses which are dominated by neogloboquadrina incompta and globigerinita uvula transfer functions using the current dataset based on the 100 m size fraction were developed and assessed different statistical models were tested using both seasonal and annual temperature data from 0 m 10 m 50 m and 100 m water depth the most precise reconstructions of subsurface temperatures were found when using summer temperatures from the 100 m depth level the transfer function was tested on holocene foraminiferal records and compared to previous reconstructions the results show that our new transfer function based on the 100 m fraction generally yields lower temperatures at both 10 and 100 m water depth than earlier reconstructions e g hald et al 2007 this could be due to the increased number of samples containing both small species and or the presence of more small specimens representing cold conditions

the n and w iceland shelf insights into last glacial maximum ice extent and deglaciation based on acoustic stratigraphy and basal radiocarbon ams dates abstract we present 32 ams radiocarbon dates collected from sediments obtained during cruises of css hudson 1993 rv jan mayen 1996 and bjarni saemundsson 1997 the radiocarbon dates were obtained on samples from the basal part of sediment cores collected across an area between 64 and 67 n and 18 29 w core sites were based on 3 5 khz acoustic subbottom surveys the 3 5 khz subbottom profiles indicate that several of the troughs contain 30 m of quaternary sediment at many sites the acoustic surveys suggest the presence of one or more strong reflectors which can be traced over extended areas 100 km of the seafloor these may represent large scale volcanic ash falls such as the vedde ash and its correlatives as well as other regionally significant tephras we report dates from seven areas 1 northern troughs eyjafjardarall hunafloadjup and reykjafjardarall 2 hunafloi area and inner shelf and fjords 3 djupall area 4 isafjardardjup area 5 kolluall 6 western shelf break and slope and 7 jokuldjup the dates range in age from marine isotope stages 3 1 five cores have basal dates 16 ka and thus provide information on the timing and environments during the deglaciation several dates of 12 ka indicate that the inner shelf may have been largely ice free by that time estimates of average sediment accumulation rates vary between 4 and 90 cm kyr with modal estimates of 30 40 cm kyr

variability in surface and deep water conditions in the nordic seas during the last interglacial period abstract stable isotope foraminifera and ice rafted detritus ird records covering the last interglacial the eemian from 7 sediment cores in a transect from the norwegian to the greenland sea are presented the percentages of neogloboquadrina pachyderma s and globigerina quinqueloba foraminiferal content and to some extent planktonic stable isotope records demonstrate marked regional changes in surface water conditions importantly the variability in the abundances of subpolar foraminifera and foraminiferal content are not coherent implying that these two types of proxies fluctuated independently of each other and most likely reflect changes in sea surface temperature and surface water carbonate productivity respectively paleoceanographic reconstructions demonstrate significant movements of the oceanographic fronts at the warmest periods the arctic front was located far west of the present day location at least within the iceland sea region at 126 125 ka this was most probably due to a stronger or more westerly located norwegian current within the later warm intervals higher heat flux to the western part of the basin reflects a combination of a stronger irminger current and or a weaker east greenland current during the main cold spell at 124 ka a diffuse arctic front had a more southeasterly location than today and intrusion of atlantic surface waters was probably limited to a narrow corridor in the eastern norwegian sea a general correspondence between minima in sea surface temperatures and light benthic 18o may indicate enhanced influx of freshwater to the basin within the cold events at least in the norwegian sea we find some evidence that the changes in surface water conditions are associated with changes in deep water ventilation the majority of the fluctuations may be related to occasional breakdown or reduction of the thermohaline circulation within the nordic seas in the earliest eemian this could result from meltwater forcing during the remaining part of the last interglacial the fine balance between temperature and salinity which the deep water formation is depending on may have been disturbed by periodic increases in fresh water supply or variable influx of warm atlantic surface waters

the distribution of living benthic foraminifera on the continental slope and rise off southwest norway abstract surface sediment samples taken by corer from 45 stations on the norwegian continental margin and in the norway basin have been investigated for their benthic foraminiferal content unlike previous studies the living benthic foraminiferal fauna was differentiated from empty tests comprising the foraminiferal death assemblage factor analysis of both the living and dead faunal data reveals six living species assemblages and five corresponding dead assemblages the additional living assemblage is characterized by the arenaceous speciescribrostomoides subglobosum that dominates between 1400 and 2000 m water depth but is rare in the dead faunal data trifarina angulosa and to a lesser extent cibicides lobatulus characterize the shallowest foraminiferal assemblage from 200 to 600 m water depth where it is associated with strong bottom currents and warm saline atlantic water of the north atlantic drift on the slope between 600 and 1200 m water depth themelonis zaandami species assemblage dominates particularly in areas characterized today by rapid sedimentation of terrigeneous material between 1000 and 1400 m depth where the slope is covered by fine grained organic rich terrigeneous mud the living foraminiferal assemblage is characterized bycassidulina teretis andpullenia bulloides below 1400 m three foraminiferal assemblages are found c subglobosum is found from 1400 to 2000 m cibicidoides wuellerstorfi andepistominella exigua predominantly live from 2000 to 3000 m water depth and below 3000 m oridorsalis umbonatus andtriloculina frigida dominate the fauna all of theelphidium excavatum tests found in this study and thecassidulina reniforme tests found above 500 m water depth were found to be reworked analysis of the sediment grain size distribution and the organic carbon content in surface samples from the deepest stations suggest that the abundance ofc wuellerstorfi ande exigua is positively correlated to relatively coarse caused by planktic foraminifera and organic rich sediments whereas high frequencies ofo umbonatus andt frigida coincide with low organic carbon content we suggest thatc wuellerstorfi is adapted to deep sea environments with relatively high food supply tolerating relatively low interstitial water oxygen content whereaso umbonatus may tolerate lower food supply prefering well oxygenated interstitial waters

maximum extent and dynamic behaviour of the last british irish ice sheet west of ireland a complete reconstruction of the last british irish ice sheet biis is hindered by uncertainty surrounding its offshore extent and dynamic behaviour this study addresses this problem by reconstructing the depositional history of four sediment cores taken from a series of sinuous glacigenic sediment ridges on the continental shelf west of ireland we present new geomorphic sedimentary and micropaleontological data that record a maximum westward biis extent that was at least 80 km farther offshore from any previous estimates the data suggests that a large ice shelf formed over parts of the shelf prior to retreat this new data increases the areal extent of grounded biis ice by 6700 km2 from previous estimates which represents a 3 increase in the irish sector of the ice sheet three new ams radiocarbon dates demonstrate for the first time that the biis advanced to the shelf edge during last glaciation late midlandian late devensian with ice advance onto the porcupine bank occurring after 24 720 260 yr cal bp deglaciation was complete by 19 182 155 yr cal bp thus constraining biis occupation over the porcupine bank to less than 5500 years estimated retreat rates of marine terminating ice across the shelf range from 70 to 180 myr 1

benthic foraminifera as indicators of habitat in a mediterranean delta implications for ecological and palaeoenvironmental studies abstract the ecology and modern distribution of benthic foraminiferal assemblages were analysed in the ebro delta nw mediterranean sea foraminiferal distributions were from 191 sediment surface samples covering a wide range of deltaic habitats and adjacent open sea areas according to similarity in species composition cluster analysis identified four habitat types 1 offshore habitat 2 nearshore and outer bays 3 salt and brackish marshes and 4 coastal lagoons and inner bays canonical correspondence analysis identified water depth salinity and sand content as the main environmental factors structuring living foraminiferal assemblages partial canonical correspondence analysis revealed water depth as the most statistically significant associated with the distribution of modern foraminifera in the ebro delta thus a transfer function for water depth using weighted average partial least squares regression was successfully developed although depth per se is unlikely to affect the foraminifera directly but will exert its effects via various environmental variables that co vary with depth in the deltaic habitats e g hydrodynamics oxygen food availability etc the resulting model r 2 0 89 rmsep 0 32 log 10 m suggested a strong correlation between observed and foraminifera predicted water depths and therefore provided a potentially useful tool for water depth reconstructions in the ebro delta this work indicated the potential role of modern foraminifera as quantitative indicators of water depth and habitat types in the ebro delta this complementary approach transfer function and indicator species will allow reconstruction of the palaeoenvironmental changes that have occurred in the ebro delta based on the benthic foraminiferal record

atlantic surface water inflow to the nordic seas during the pleistocene holocene transition mid late younger dryas and pre boreal periods 12 450 10 000 a bp the inflow of atlantic water to the nordic seas from mid late younger dryas to earliest holocene 12 450 10 000 a bp is reconstructed on the basis of a high resolution core link14 from 346 m water depth on the east faroe shelf we have analysed the distribution of planktic and benthic foraminifera stable isotopes and ice rafted debris ird and calculated absolute temperatures and salinities by transfer functions during the investigated time period there was almost continuous inflow of atlantic water to the nordic seas deposition of ird during the mid late younger dryas and pre boreal coolings indicates the presence of melting icebergs and that summer sea surface temperatures were low the east west temperature gradient across the faroe shetland channel was much steeper than today the cold conditions around the faroe islands are attributed to stronger east greenland and east icelandic currents than at present the near continuous inflow of atlantic water is consistent with published evidence suggesting that deep convection took place in the nordic seas although the convection sites probably had shifted to a more easterly position than at present around the time of deposition of the saksunarvatn tephra c 10 350 a bp sea surface temperatures increased to the present level

ocean warming and gas hydrate stability on the mid norwegian margin at the storegga slide abstract the sensitivity of oceanic gas hydrates and submarine slope stability to the combined forcing of sea level changes and bottom water perturbation is a critical issue for risk assessment in the storegga slide area on the mid norwegian margin evidence for the existence of gas hydrates both inside and outside the storegga slide complex comes from reflection seismic profiles where a bottom simulating reflection marks today s base of the gas hydrate stability zone paleo bottom water temperatures show a relatively fast increase at approximately 12 5 10 ka calendar years following the younger dryas while stable warm water conditions have prevailed since then despite sea level rise this warm water inflow caused a major reduction in the thickness of the gas hydrate stability zone along the upper slope of the mid norwegian margin modelling results indicate that critical hydrate stability conditions and consequently the maximal potential pore pressure build up occur at the location of the storegga slide headwall although the major phase of hydrate melting predates the storegga slide event dated at 8 2 ka calendar years reduced hydrate stability conditions could have facilitated or contributed to sub marine slope failure additionally the bottom simulating reflections within the slide complex seem to have nearly adjusted to new equilibrium conditions highlighting the dynamics of hydrate stability in continental margin sediments under environmental changes climate change geohazards

holocene palaeoceanographic evolution off west greenland benthic foraminiferal assemblages from a core southwest of disko bugt provide a holocene perspective last 7 ka bp on ice sheet ocean interactions between the west greenland current wgc and the west greenland ice sheet changes in the fauna reveal significant variations in the water mass properties temperature and salinity of the wgc through time from 7 3 to 6 2 ka bp a relatively warm strong wgc influences ice sheet melt in disko bugt and causes enhanced meltwater production resulting in low surface water productivity the most favourable oceanographic conditions occur from 5 5 to 3 5 ka bp associated with thermal optimum like conditions encompassing minimum ice sheet extent in the disko bugt area these conditions are attributed to 1 reduced meltwater influence as the ice sheet is land based and 2 enhanced contribution of warm saline water masses from the irminger current to the wgc the transition into the late holocene last 3 5 ka bp is characterized by a cooling of oceanographic conditions caused by increased advection of cold low salinity water masses from the east greenland current a longer term late holocene cooling trend within the wgc is attributed to the onset of neoglacial cooling within the north atlantic region superimposed on this cooling trend multicentennial scale variability within the wgc matches reconstructions from a nearby coring site in disko bugt as follows 1 cooling at 2 5 ka bp linked to the 2 7 ka bp cooling event 2 a warm phase centred at 1 8 ka bp associated with the roman warm period 3 slight warming between 1 4 and 0 9 ka bp linked to the medieval climate anomaly 4 severe cooling of the wgc after 0 9 ka bp culminating at 0 3 ka bp during the little ice age we show that multicentennial scale palaeoceanography variability along the west greenland margin is driven by ocean forcing i e variations in the relative contribution of atlantic irminger current and polar east greenland current water masses to the wgc during the last 7 ka bp influencing ice sheet dynamics

last interglacial arctic warmth confirms polar amplification of climate change the warmest millennia of at least the past 250 000 years occurred during the last interglaciation when global ice volumes were similar to or smaller than today and systematic variations in earth s orbital parameters aligned to produce a strong positive summer insolation anomaly throughout the northern hemisphere the average insolation during the key summer months m j j was ca 11 above present across the northern hemisphere between 130 000 and 127 000 years ago with a slightly greater anomaly 13 over the arctic greater summer insolation early penultimate deglaciation and intensification of the north atlantic drift combined to reduce arctic ocean sea ice allow expansion of boreal forest to the arctic ocean shore across vast regions reduce permafrost and melt almost all glaciers in the northern hemisphere insolation amplified by key boundary condition feedbacks collectively produced last interglacial summer temperature anomalies 4 5 c above present over most arctic lands significantly above the average northern hemisphere anomaly the last interglaciation demonstrates the strength of positive feedbacks on arctic warming and provides a potentially conservative analogue for anticipated future greenhouse warming

stable isotope evidence for glacial lake drainage through the st lawrence estuary eastern canada 13 1 12 9 ka abstract postglacial varved and rhythmically laminated clays deposited during the transition from glacial lake vermont lv to the champlain sea cs record hydrological changes in the champlain st lawrence valley cslv at the onset of the younger dryas 13 1 12 9 ka linked to glacial lake drainage events oxygen isotope 18o records of three species of benthic foraminifera cassidulina reniforme haynesina orbiculare islandiella helenae from six sediment cores and the freshwater ostracode candona from one core were studied results show six large isotope excursions 0 5 to 2 in c reniforme 18o values five excursions in h orbiculare

late glacial to recent distribution pattern of deep water uvigerina species in the north eastern atlantic phases with massive abundances of uvigerina species recorded in north atlantic deep sea cores were previously attributed to water mass properties or to extended high productivity during the last glacial we investigated the uvigerina distribution in 53 sediment cores and 555 surface samples from the north eastern atlantic ranging from 308 to 708n and 1 to 4410 m water depth our results showed that uvigerina pigmea dominated in late pleistocene assemblages whereas uvigerina peregrina and uvigerina peregrina parva were common during the holocene uvigerina pigmea lives today in the gulf of guinea and south atlantic only 98n to 178s but was present up to 548n during the last glacial maximum the species retreated north and southwards during termination i and disappeared in the north eastern atlantic off northern portugal 6100 years ago uvigerina peregrina and u peregrina parva spread out from isolated occurrences along the continental slope off western iberia at the onset of termination i uvigerina peregrina exhibited recent abundance maxima at goban spur plateau des landes and the iberian margin these areas are subjected to strong lateral advection by downslope transport and sediment focusing the actual flux rate of particulate organic matter is locally raised by a factor of 4 to 5 comparable flux rates were otherwise recorded at u peregrina maxima under the nw african coastal upwelling regime the recent distribution of u pigmea and evidence from sediment cores show an organic carbon flux of 3 5 g c m 2 yr 1 as minimum for a sustainable population of this species alkenone pigment and planktonic foraminiferal records from cores md952039 and md952040 revealed that a spring bloom dominated productivity dynamics and a balanced food particle composition of haptophyteae algae and diatoms were limiting environmental factors for u pigmea during the pleistocene a widespread change from glacial to modern productivity characteristics during the last deglaciation may have triggered the early holocene disappearance of u pigmea from the north eastern atlantic

north atlantic fennoscandian holocene climate trends and mechanisms abstract to investigate the mechanisms behind holocene regional climate trends from north of 58 n in the north atlantic fennoscandian region principal component analysis pca was performed and a temperature anomaly stack produced from 81 proxy derived summer temperature time series from 74 sites the pc results show distinctly different trends for near surface versus surface temperatures demonstrating the importance of handling these separately the first pc of weighted sea surface summer temperature time series and continental time series explains 45 8 of the variance where the uncertainty is the standard deviation of the distribution of variance explained across the 1000 age uncertain ensemble members pc1 has a relatively uniform expression over the whole region closely following the summer insolation at 65 n the second pc explains 22 4 of the variance and shows a non uniform expression with loadings in opposite directions in the northern and southeastern parts of the region comparing the pc time series with model runs and with the timing of the demise of the laurentide ice sheet lis suggest that this pattern reflects both topographic and albedo effects of the lis as well as release of meltwater into the north atlantic and arctic oceans comparing the stack of gridded records with published global stacks reveals an unusual holocene temperature development in the north atlantic fennoscandian region most likely resulting from the location relative to the decaying lis

coupled response of the late glacial climatic shifts of northwest europe reflected in greenland ice cores evidence from the northern north sea the climatic regimes of the land areas adjacent to the north sea are controlled by the influx of atlantic water north of the british isles and into the north sea a high resolution record from the norwegian channel off western norway covering the past 15 ka 14 c shows that prior to the younger dryas there were three periods of sea surface conditions there similar to those of the present interspersed with arctic conditions these changes corresponding to an increase of approx 5 c in summer sea surface temperatures took place on the scale of

eight hundred year temperature variability from the norwegian continental margin and the north atlantic thermohaline circulation 1 four cores raised from the eastern norwegian sea and adjacent norwegian fjords at sites influenced by atlantic water have been investigated oxygen isotope analyses in benthic and planktonic foraminifera are used as a proxy for the paleotemperature development spanning the last 800 years the cores have been dated using a combination of 210pb and radiocarbon dates yielding time resolutions of 2 5 years for the last century and 9 25 years beyond this the proxy records have been compared with instrumental time series covering the last 100 years in order to validate the oxygen isotope measurements as a proxy for paleotemperature the comparison shows that the paleotemperature variability derived from the oxygen isotope analyses is generally similar to the amplitudes and trends seen in the instrumental time series in particular a cooling around 1905 1925 followed by a warming until 1955 is evident in all proxy records as well as in the instrumental time series beyond the last century the proxy records show two periods from 1225 1450 and 1650 1905 25 when temperatures were 1 3 1 6 c lower than present separated by a period of temperatures periodically comparable to present the last 80 years represent the modern warming and appear to be the warmest period of the last 800 years we find that that the ocean temperature variability is comparable to terrestrial reconstructions from the region implying a strong link in the ocean atmosphere climate system this suggests that the climate variability in this region beyond the period covered by instrumental time series was also associated with changes in the thermohaline circulation

holocene climatic development in skagerrak eastern north atlantic foraminiferal and stable isotopic evidence a high resolution multiproxy study of core md99 2286 reveals a highly variable hydrographic environment in the skagerrak from 9300 cal yr bp to the present the study includes foraminiferal faunas stable isotopes and sedimentary parameters as well as temperature and salinity reconstructions of a c 29 m long radiocarbon dated core record the multivariate technique fuzzy c means was applied to the foraminiferal counts and it was extremely valuable in defining subtle heterogeneities in the foraminiferal faunal data corresponding to hydrographic changes the major early mid holocene littorina transgression led to flooding of large former land areas in the north sea the opening of the english channel and danish straits and initiation of the modern circulation system this is reflected by fluctuating c n values and an explosive bloom of hyalinea balthica a slight indication of ameliorated conditions between 8000 and 5750 cal yr bp is related to the holocene thermal maximum a subsequent increase in

paleoenvironments of the last interglacial in northwest north atlantic region and adjacent mainland canada abstract the paleoenvironmental conditions that prevailed in the northwest north atlantic regions and adjacent mainland canada during the last interglacial are documented through lithostratigraphical and paleontological data in terrestrial sections and marine cores with special reference to the deep sea records that allow global correlations based on their isotopic stratigraphy the onshore paleovegetational data and the offshore planktonic faunal and algal records demonstrate much warmer than present terrestrial and marine environments during the climate optimum of the last interglacial sensu stricto isotopic substage 5e optimal conditions persisted in surface water of the labrador sea during the early glacial inception isotopic substage 5e 5d transition when extensive ice masses developed over arctic canada a deterioration of sea surface temperature in labrador sea followed the maximum 18 o peak of isotopic substage 5d during the later part of stage 5 climatic conditions similar to the present prevailed over southeastern canada and a recurrent warming is recorded in south central labrador sea fluctuating ice volumes in the canadian arctic led to episodic dilution of surface water masses in baffin bay and the eastern labrador sea and subarctic conditions apparently prevailed in nearshore environments of baffin island despite an ice marginal context

reconstruction of inflow of atlantic water to isfjorden svalbard during the holocene correlation to climate and seasonality abstract the distribution patterns of benthic foraminifera faunas stable isotopes and ice rafted debris ird have been studied in piston core jm98 845 pc from isfjorden western svalbard to reconstruct changes in the flow of atlantic water during the holocene interglacial the paleoenvironmental conditions in isfjorden and the inflow of the atlantic water followed closely the changes in insolation with strong seasonality in the early holocene and weaker seasonality in the middle to late holocene a summer temperature maximum of the bottom water occurred in the early holocene 10 500 c 8200 years bp cooling began at 9000 years bp with stepwise coolings at c 8200 7400 and 4000 years bp the cooling correlated with an increase in ice rafting and increased influence of polar water and seasonal sea ice cover between 4000 and 2000 years bp bottom water temperatures reached a minimum after 2000 years bp episodic inflow of warmer atlantic water at the bottom of the fjord occurred and conditions became more unstable the data indicate close interaction of the flow of atlantic water with the development of the terrestrial climate and the amount of polar meltwater and sea ice

assessing the performance of a foraminifera based transfer function to estimate sea level changes in northern portugal a b s t r a c t a r t i c l e i n f o article history received 14 april 2010 available online 15 december 2010 we assessed the performance of a transfer function model for sea level studies using salt marsh foraminifera from two estuaries of northern portugal an independent data set of 12 samples and 13 sub fossil samples from a core were used to evaluate if reconstructions and errors derived from current models are adequate initial transfer function models provided very strong results as indicated by cross validation component 2 r 2 0 80 0 82 rmsep ranged from 10 7 to 12 3 cm and improved its performance by ca 10 when sample size reached ca 50 results derived using an independent test data set indicate that cross validation is a very effective approach and produces conservative errors when compared to observed errors we additionally explored the possible effect of transforming the concentration data into percent in the error estimations by comparing the results obtained based on the use of both concentration and compositional data results indicate that this type of transformation does not affect the performance of the transfer function results derived from a reconstruction of sub fossil samples from a core indicate that high resolution sea level reconstructions are possible but show that depositional environments have to be selected carefully in order to minimize the impact of possible taphonomical loss

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

reprint of arctic planktic foraminiferal assemblages implications for subsurface temperature reconstructions abstract earlier reconstructions of the inflow of atlantic water to arctic and subarctic oceans based on foraminiferal proxy data have been obstructed by uncertain quantitative reconstructions of sea surface and subsurface temperatures in this study surface sediment samples with undisturbed sediment water interface from polar north atlantic and barents sea were retrieved and prepared at the size fractions from 100 m to 1000 m the foraminiferal analyses show that neogloboquadrina pachyderma constitutes 96 99 of the fauna in arctic and polar surface water masses the same result is obtained when investigating the 150 m size fraction however in arctic areas influenced by atlantic water additional faunal information is obtained when using the smaller 100 m size fraction in these areas n pachyderma is reduced to about 50 and the relatively small species turborotalita quinqueloba becomes very frequent this also applies to the coastal water masses which are dominated by neogloboquadrina incompta and globigerinita uvula transfer functions using the current dataset based on the 100 m size fraction were developed and assessed different statistical models were tested using both seasonal and annual temperature data from 0 m 10 m 50 m and 100 m water depth the most precise reconstructions of subsurface temperatures were found when using summer temperatures from the 100 m depth level the transfer function was tested on holocene foraminiferal records and compared to previous reconstructions the results show that our new transfer function based on the 100 m fraction generally yields lower temperatures at both 10 and 100 m water depth than earlier reconstructions e g hald et al 2007 this could be due to the increased number of samples containing both small species and or the presence of more small specimens representing cold conditions

ecology of deep sea benthic foraminifera in the north atlantic during the last glaciation food or temperature control abstract in this study we explore the paleoecology of nineteen species and two species groups of deep sea benthic foraminifera in relation to bottom water temperature and food supply in the central north atlantic during the last glaciation 60 000 28 000 years bp the study is based on core so82 02ggc taken from 1730 m water depth on the western flank of reykjanes ridge the climate of the investigated period was extremely unstable interrupted by thirteen warmings and coolings the so called dansgaard oeschger events at so82 02ggc surface and bottom water temperatures varied with up to 5 c between the warm interstadials and the cold stadials surface productivity as indicated by the flux of planktic foraminifera varied with a factor of up to ten the dansgaard oeschger events had a significant impact on the benthic foraminiferal faunas which experienced up to 70 replacement between the interstadials and stadials multivariate analysis reveals that the investigated species can be separated into two groups group 1 including bulimina costata brizalina subspinescens epistominella decorata and trifarina angulosa was attracted to higher temperatures and high food supply group 2 including pullenia bulloides valvulineria laevigata and melonis barleeanus was attracted to colder water and low food supply three species belonging to the cold group cibicidoides wuellerstorfi oridorsalis umbonatus and eponides tumidulus are almost exclusively confined to sediments rich in ice rafted detritus a few species including nonionella iridea and epistominella vitrea show opportunistic behaviour most species are epifaunal to shallow infaunal and live today in oligotrophic to mesotrophic habitats our investigations indicate that temperature was the primary factor responsible for the relative abundance and main grouping of species however four species show little influence by temperature and several perhaps most were clearly also affected by food supply

high resolution stratigraphy of the faeroe shetland channel and its relation to north atlantic paleoceanography the last 87 kyr abstract two piston cores from the faeroe shetland channel have been investigated for stratigraphic and paleoceanographic correlation with atlantic ocean and norwegian sea records the high resolution cores have been analyzed for the downcore distribution of planktic and benthic foraminifera and oxygen isotopes ams 14 c dates and the position of ash layers i and ii form the basis for the correlation core na81 10 covers the period from isotope stage 3 to recent stage 1 while core na81 04 covers isotope stages 5a to 1 the holocene is well represented in core na81 10 by 2 m of sediment whereas it is only 50 cm in core na81 04 which is situated directly under the main core of the norwegian sea deep water outflow the transition of isotope stage 2 to stage 1 is affected by dissolution and thus is less clearly represented ams 14 c dates show that termination ia begins at 16 ka and ends at about the 13 ka level the last glacial maximum lgm defined at 19 16 ka is characterized by an ird peak faunal planktic foraminifera maxima dated at 17 3 and 18 25 ka and a high percentage of globigerina quinqueloba apparently open water conditions and circulation within the norwegian sea prevailed at least from 22 5 to 14 8 ka during the greatest part of stage 2 including the lgm and well onto termination ia a preservation maximum is observed throughout stage 2 isotope stage 3 with a nearly complete record of isotope substages is well represented in both cores oxygen isotope depletion peaks correlate with fauna minima and in time to north atlantic heinrich events h5 h1 faunal data indicate that deep water is generated within the norwegian greenland sea repeatedly since 26 ka with stops prior to 26 ka 22 5 20 8 20 5 ka and between 14 9 and 13 ka h3 h2 and h1 all isotope depletion peaks since ca 50 ka are anticorrelated with fauna and are mainly controlled by surface salinity changes isotope stages and substages are directly correlated to fauna peaks and temperature between 87 and ca 50 ka the faeroe shetland channel record shows that repeated presences of atlantic surface water and deep convection alternating with convection shutdowns have occurred within the norwegian sea greenland sea from the beginning of stages 5a to 1

late glacial to holocene environmental changes and climate variability evidence from voldafjorden western norway sedimentological micropalaeontological benthic foraminifers and dinoflagellate cysts stable isotope data and ams 14c datings on cores and surface samples in addition to acoustic data have been obtained from voldafjorden western norway based on these data the late glacial and holocene sedimentological processes and variability in circulation and fjord environments are outlined glacial marine sedimentation prevailed in the voldafjorden between 11 0 kyr and 9 2 kyr bp radiocarbon years in the later part of the allerod period and for the rest of the holocene there was deposition of fine grained normal marine sediments in the fjord basin turbidite layers recorded in core material and on acoustic profiles dated to ca 2 1 6 9 7 6 ca 9 6 and ca 11 0 kyr bp interrupted the marine sedimentation the event dated to between 6 9 and 7 6 kyr bp probably corresponds to a tsunami resulting from large scale sliding on the continental margin off norway the storegga tsunami during the later part of the allerod period voldafjorden had a strongly stratified water column with cold bottom water and warm surface water reaching interglacial temperatures during the summer seasons during the younger dryas cold event there was a return to arctic sea surface summer temperatures possibly with year round sea ice cover the entire benthic fauna being composed of arctic species the first strong holocene warming observed simultaneously in bottom and sea surface temperature proxies occurred at ca 10 1 kyr bp bottom water proxies indicate two cold periods possibly with 2 c lowering of temperatures at ca 10 0 pbo 1 and at 9 8 kyr bp pbo 2 these events may both result from catastrophic outbursts of baltic glacial lake water the remainder of the holocene experienced variability in basin water temperature indicated by oxygen isotope measurements with an amplitude of ca 2 c with cooler periods at ca 8 4 9 0 5 6 5 2 4 6 4 2 3 5 2 2 1 2 and 0 4 0 8 kyr bp changes in the fjord hydrology through the past 11 3 kyr show a close correspondence both in amplitude and timing of events recorded in cores from the norwegian sea region and the north atlantic these data suggest a close relationship between fjord environments and variability in large scale oceanic circulation copyright 2001 john wiley sons ltd

late weichselian environmental change in norway including svalbard a synthesis of the principal environmental changes that are inferred to have occurred in norway and svalbard fig 1 during the late glacial period 14 9 ka bp is presented the paper has three sections dealing separately with i western norway ii northern norway and iii spitsbergen svalbard the main conditions described include glacial events sea level changes vegetation history and climatic variations a summary chart of environmental reconstructions is presented for each of the three areas each including a curve of temperature reconstructions for the late glacial period these indicate some significant regional variations in contemporaneous thermal conditions during the late glacial

oceanographic changes through the last millennium off north iceland temperature and salinity reconstructions based on foraminifera and stable isotopes abstract temperature and salinity reconstructions for two 1000 year high resolution sedimentary records located at the boundary between atlantic and arctic surface waters on the north icelandic shelf are based on transfer functions and oxygen isotopes for planktonic and benthic foraminifera there is a general increase of arctic water indicator species at the transition from the medieval warm period into the little ice age lia and a subsequent return of atlantic water indicator species towards the end of the lia and in the 20th century the timing of the reconstructed temperature changes both at the beginning and at the end of the lia appears to be slightly different for the different water masses the earliest temperature change is seen in the bottom and subsurface waters where a cooling is reconstructed as early as ad 1150 1200 at both locations whereas previously published diatom based and alkenone based sea surface temperature reconstructions show a change at ad 1300 coinciding with the air temperature shift in the area our results show the need of a thorough understanding of the oceanography in the study area as well as the different living habitat for the biological proxies used for the temperature estimates

multi proxy analysis for reconstructing the late holocene evolution of a mediterranean coastal lagoon environmental variables within foraminiferal assemblages abstract this study reconstructs the evolution of foraminiferal assemblages and the environmental variables type of substrate content in calcium carbonate and content in organic matter in the valencia lagoon western mediterranean in response to changes in the late holocene in this area of low tidal range several multiproxy analyses were carried out to determine which environmental variables influence the distribution of the fossil assemblage and its association with global regional or local climatic phenomena the statistical results show that in environments with higher exposure to marine conditions the calcium carbonate content is the dominant factor whereas in more restricted environments the type of substrate grain size is determinant the micropaleontological content reveals the evolution from a saline paleoenvironment with a clear marine influence towards the hyposaline or freshwater conditions recorded at the top three phases were identified in the evolution of this area from 2800 cal yr bp to the present a brackish lagoon with marine connection at the base followed by a deposit of brackish lagoon 1232 74 cal yr bp 791 104 cal yr bp culminating in a brackish marsh 791 104 cal yr bp to present interpreted as the definitive closure process of the lagoon favored by the coastal progradation processes related with an extraordinary input of sediments these findings reflect the climatic variability of the medieval climate optimum mco 1 05 and 0 65 kcal bp and the migration of the river turia mouth which favored the coastal progradation processes the flood events registered at this phase may have coincided with changes in the landscape and greater anthropic influence at the end of the lia 150 cal yr bp coastal processes are mainly responsible for the evolution of this area during phase i while the influence of fluvial processes is significant towards the top especially in phase iii

mid to late holocene oxygen isotopes from voldafjorden western norway basin water in deep silled norwegian fjords is primarily influenced by inflowing atlantic water originating from the norwegian atlantic current nwac previous studies suggest that benthic foraminiferal oxygen isotope records from such fjords are strongly influenced by variability in this current the present paper presents a mid to late holocene record 6 2 2 ka with 17 yr time resolution from a western norwegian deep silled fjord voldafjorden an age model based on ten ams radiocarbon dates on marine carbonates and on one plant macrofossil has been established the study focuses on the oxygen isotope results obtained from two species of benthic foraminifera cassidulina laevigata and uvigerina mediterranea the 18o c laevigata record has systematically larger amplitudes than the 18o u mediterranea record which most likely is related to different life cycles periods of calcification the oxygen isotope results show a clear shift towards higher values between 5 and 4 ka interpreted to reflect

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