deposition models for chronological records abstract long term sedimentary sequences provide a wealth of useful information for research into the palaeo environment especially in relation to past climate change shorter records provide similar information in many archaeological contexts however if such records are to be used to provide precise timing of events and more critically the relative timing between different records methods are needed to provide accurate and precise age depth models for these sequences given the imprecision of individual calibrated radiocarbon determinations it is necessary to use the information we have about the deposition process to refine our chronologies and also to provide interpolation between dated levels in any sequence even with layer counted chronologies the uncertainties are sometimes hard to quantify this paper outlines a range of bayesian models for deposition which have been implemented in the computer programme oxcal these models can be used to combine information from the sediments themselves with radiocarbon or other direct dating information such models have the potential to integrate information between different records and provide a coherent chronology on which to base environmental or archaeological research

temperature calibration and phylogenetically distinct distributions for freshwater alkenones evidence from northern alaskan lakes abstract alkenones are a class of unsaturated long chain ketone biomarkers that have been used to reconstruct sea surface temperature and more recently continental temperature by way of alkenone unsaturation indices e g u 37 k and u 37 k alkenones are frequently found in brackish and saline lakes however species effects confound temperature reconstructions when multiple alkenone producing species with different temperature responses are present interestingly available genetic data indicate that numerous freshwater lakes host a distinct phylotype of alkenone producing haptophyte algae the group i or greenland phylotype providing evidence that species effects may be diminished in freshwater lakes these findings encourage further investigation of alkenone paleotemperature proxies in freshwater systems here we investigated lakes from northern alaska n 35 and show that alkenones commonly occurred in freshwater lakes where they featured distinct distributions characterized by dominant c37 4 alkenones and a series of tri unsaturated alkenone isomers the distributions were characteristic of group i type alkenone distributions previously identified in greenland and north america our analysis of suspended particulate matter from toolik lake 68 38 n 149 36 w yielded the first in situ freshwater u 37 k calibration u 37 k 0 021 t 0 68 r2 0 85 n 52 rmse 1 37 c we explored the environmental significance of the tri unsaturated isomers using our northern alaskan lakes dataset in conjunction with new data from haptophyte cultures and canadian surface sediments our results show that these temperature sensitive isomers are biomarkers for the group i phylotype and indicators of multiple species effects together these findings highlight freshwater lakes as valuable targets for continental alkenone based paleotemperature reconstructions and demonstrate the significance of the recently discovered tri unsaturated isomers

increased aridity during the early holocene in west greenland inferred from stable isotopes in laminated lake sediments abstract palaeoclimatic inferences from the greenland ice cores suggest that holocene climate was relatively uniform the ice core records primarily reflect hemispheric temperature related climate processes whereas lakes tend to reflect regional scale climatic variability stable isotopes in closed basin lakes are sensitive to changes in effective precipitation here we report stable isotope evidence 18 o and 13 c records from authigenic calcite in laminated lake sediments from two oligosaline closed basin lakes in southern west greenland sondre stromfjord the stable isotope profiles indicate a dynamic early to mid holocene climate as a strongly negative precipitation evaporation balance from 7000 to 5600 cal yr bp lowered lake levels throughout the region this interpretation of the stable isotope data is supported by a survey of modern lake water isotopic composition and fossil shorelines around many closed basin saline lakes which indicate higher lake levels in the past the increased aridity during the early holocene resulted from a shift in regional circulation patterns in the davis straits baffin bay area enhanced stability of the west greenland depression and the situation of a regional trough over the sondre stromfjord area caused weakened westerly airflow and strengthened outflow i e winds blowing off the ice sheet resulting in reduced precipitation in the region decreased precipitation coupled with higher insolation probably caused the negative precipitation evaporation balance

normalizing xrf scanner data a cautionary note on the interpretation of high resolution records from organic rich lakes x ray fluorescence xrf scanning of unlithified untreated sediment cores is becoming an increasingly common method used to obtain paleoproxy data from lake records xrf scanning is fast and delivers high resolution records of relative variations in the elemental composition of the sediment however lake sediments display extreme variations in their organic matter content which can vary from just a few percent to well over 50 as xrf scanners are largely insensitive to organic material in the sediment increasing levels of organic material effectively dilute those components that can be measured such as the lithogenic material the closed sum effect consequently in sediments with large variations in organic material the measured variations in an element will to a large extent mirror the changes in organic material it is therefore necessary to normalize the elements in the lithogenic component of the sediment against a conservative element to allow changes in the input of the elements to be addressed in this study we show that al which is the lightest element that can be measured using the itrax xrf scanner can be used to effectively normalize the elements of the lithogenic fraction of the sediment against variations in organic content we also show that care must be taken when choosing resolution and exposure time to ensure optimal output from the measurements

8000 year marine record of climate variability and fjord dynamics from southern greenland abstract holocene sediment records of glacio marine environmental and climatic changes from ikersuaq fjord and narsaq sound in southern greenland have been studied the ikersuaq fjord record representing the last c 500 years is dominated by turbidite sedimentation and very high sedimentations rates of up to 1 cm yr the adjacent narsaq sound site on the other hand represents a continuous and more slowly accumulating sedimentation record of the last c 8000 years the narsaq record reveals changes in position and melting rates of glacier termini of the nearby greenland ice sheet from the holocene thermal optimum period terminating at about 5 0 ka to the neoglaciation period during the late holocene from 8 0 ka to 4 8 ka ice rafted debris ird influx progressively became reduced supporting a landward retraction of glacier termini neoglaciation of the region appears to have been initiated at about 4 8 ka with a culmination of ird rain at about 4 6 ka 3 6 ka 2 2 ka 1 0 ka 0 7 ka and 0 5 ka and onward some of these ird events appear to be associated with enhanced melting and glacier instability during warming episodes however at the transition to the little ice age at about 1450 years ad a marked increase in ird influx took place the bottom water of narsaq sound appears to have been dominated by modified irminger water atlantic during most of the holocene bottom current flow was quite sluggish before 3 2 ka whereas the late holocene period appears to have been characterised by three pronounced episodes of increased bottom current velocity and increased calcareous benthic foraminifera productivity the long term climate pattern in the narsaq sound record follows climate changes consistent with patterns of east greenland current variability which is partly related to dominant north atlantic oscillation forcing of wind and ice drift patterns

mid to late holocene hydrological and climatic variability in disko bugt central west greenland diatom and lithological analyses were carried out on two sediment cores from disko bugt and the adjacent kangersuneq fjord west greenland in order to investigate mid to late holocene 6 9 0 7 kyr bp hydrographic and climatic variability while the disko bugt record is found to reflect mainly west greenland current wgc fluctuations that can be linked to north atlantic circulation variability the fjord record appears to be more representative of local climate conditions the records demonstrate that the period of investigation was marked by a late holocene thermal maximum beginning at c 4 8 kyr and ending between 3 5 and 3 1 kyr bp encompassing a colder period between c 4 0 and 3 8 kyr bp an episode of higher surface water temperature is also indicated in disko bugt between 2 2 and 1 5 kyr bp in contrast the record from kangersuneq fjord suggests persisting cooler summer surface waters for this interval interpreted to be attributable to increased meltwater outflow the warming episode recogni

itrax description and evaluation of a new multi function x ray core scanner a new automated multi function core scanning instrument named itrax has been developed that records optical radiographic and elemental variations from sediment half cores up to 1 8 m long at a resolution as fine as 200 m an intense micro x ray beam focused through a flat capillary waveguide is used to irradiate samples to enable both x radiography and x ray fluorescence xrf analysis data are acquired incrementally by advancing a split core via a programmable stepped motor drive through the flat rectangular section x ray beam traditional xrf determination of element composition in sediments provides high quality data but it takes a considerable time and normally consumes gram quantities of material that is often only available in limited quantities the itrax core scanner non destructively collects optical and x radiographic images and provides high resolution elemental profiles that are invaluable for guiding sample selection for further destructive detailed sampling this paper presents a description of the construction characteristics and capabilities of the itrax system high resolution itrax data obtained from sediment cores are also presented and compared with results from traditional wavelength dispersive xrf analysis at lower resolution finally some recent technical developments linked to the second generation itrax are presented

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

foraminiferal reconstruction of mid to late holocene ocean circulation and climate variability in disko bugt west greenland benthic foraminifera from two cores collected from disko bugt a large marine embayment in west greenland are used to investigate hydrographic changes during the mid to late holocene the records document fluctuations in the west greenland current wgc linked to large scale changes in north atlantic circulation and for one core impacts of local climate changes in particular changes in the cold east greenland current egc and the warm more saline irminger current ic influence the wgc and propagate into disko bugt the cores record subsurface warming associated with the holocene thermal maximum htm from c 6 to 5 ka cal bp gradual cooling of wgc from 5 ka cal bp was interrupted by an abrupt warm interval from 3 9 to 3 5 ka cal bp before cooling became more prominent from 3 5 to 2 ka cal bp this cold period corresponds to the well documented northern hemisphere cooling of the neoglacial and we interpret it as reflecting enhanced flux from the egc and reduced ic flux to the wgc in disko b

holocene thinning of the greenland ice sheet the nature of the response of the greenland ice sheet gis to climate change is a fundamental question in climate science but the details remain unclear during the holocene climate optimum 6 000 to 9 000 years ago for example many locations in the northern hemisphere showed unusual warmth yet changes in greenland appeared inconsistent vinther et al now standardize the previously disparate seeming ice core records of climate history on the gis during the holocene and find consistent evidence for a stronger climate optimum than was previously recognized together with elevation reduction and marginal ice sheet thinning the response of the greenland ice sheet gis to changes in climate remains uncertain during the holocene climatic optimum an unusually warm period from about 9 000 to 6 000 years ago changes in greenland appear inconsistent with the rest of the northern hemisphere here the greenland holocene temperature history and the evolution of gis surface elevation are extracted from four gis locations the results may resolve this disparity on entering an era of global warming the stability of the greenland ice sheet gis is an important concern1 especially in the light of new evidence of rapidly changing flow and melt conditions at the gis margins2 studying the response of the gis to past climatic change may help to advance our understanding of gis dynamics the previous interpretation of evidence from stable isotopes 18o in water from gis ice cores was that holocene climate variability on the gis differed spatially3 and that a consistent holocene climate optimum the unusually warm period from about 9 000 to 6 000 years ago found in many northern latitude palaeoclimate records4 did not exist here we extract both the greenland holocene temperature history and the evolution of gis surface elevation at four gis locations we achieve this by comparing 18o from gis ice cores3 5 with 18o from ice cores from small marginal icecaps contrary to the earlier interpretation of 18o evidence from ice cores3 6 our new temperature history reveals a pronounced holocene climatic optimum in greenland coinciding with maximum thinning near the gis margins our 18o based results are corroborated by the air content of ice cores a proxy for surface elevation7 state of the art ice sheet models are generally found to be underestimating the extent and changes in gis elevation and area our findings may help to improve the ability of models to reproduce the gis response to holocene climate

foraminiferal distribution on the continental margin off nova scotia abstract q mode factor analysis of total foraminiferal abundance data living plus dead from 250 grab samples taken from the continental margin off nova scotia allows the determination of eight factor assemblages on the northeastern shelf an exclusively agglutinated assemblage dominated byadercotryma glomerata occupies both banks and basins central shelf basins contain a predominantly calcareous assemblage dominated byglobobulimina auriculata andnonionellina labradorica transitional between these two factor assemblages is an agglutinated assemblage dominated bysaccammina atlantica consistently present along the shelf edge is atrifarina angulosa assemblage in northeastern bays and a few samples near sable island an agglutinatedeggerella advena assemblage is found a relict and transport affected assemblage dominated byelphidium excavatum occurs in the southwestern approaches to emerald basin sandy gravelly areas of the inner shelf and outer bank regions are characterized by acibicides lobatulus assemblage the statistical relationships of these defined assemblages to various aspects of the marine environment depth temperature salinity percent gravel sand and mud were investigated through multiple regression techniques results indicate that the present foraminiferal distribution patterns off nova scotia are influenced by the prevailing watermass characters and substrate theadercotryma glomerata assemblage is influenced by the presence of cold 0 4 c low salinity waters 32 33 of arctic labrador current origin the central basin assemblage g auriculata is related to warmer 8 12 c more saline waters 35 of slope origin the transition between these two bottom waters is marked by the opportunisticsaccammina atlantica assemblage preferred substrate character possibly determines the occurrence of thecibicides lobatulus islandiella islandica andeggerella advena assemblages trifarina angulosa shows a significant relationship to salinity and depth although the surficial sediments on the nova scotian shelf are largely the product of reworking of glacial deposits during late glacial and early holocene times all but thee excavatum factor assemblage appear to be in equilibrium with the modern oceanographic regime

late holocene atlantic bottom water variability in igaliku fjord south greenland reconstructed from foraminifera faunas a high resolution record of late holocene subsurface water mass characteristics in outer igaliku fjord south greenland is presented based on benthic foraminifera faunas from core po 243 451 collected from a water depth of 304 m strati cation with atlantic water masses present in the lower part of the water column is suggested to have prevailed during the last 3200 cal years except for a period referred to as the mediaeval warm period mwp during the mwp c ad 885 1235 the outer part of igaliku fjord experienced enhanced vertical mixing and a high hydrodynamic energy level which we ascribe to increasing wind stress through this period corresponding to the period of the norse settlement the transition from the mwp to the little ice age lia shows a two step pattern with a short climatic amelioration around ad 1520 before maximum cooling occurred the intensified wind stress and the overall environmental change are suggested to have contributed to the loss of the norse settlement in greenland periods with strong stratification and marked in uence of atlantic subsurface water masses around 2 6 1 3 ka bp and during the lia are correlated to north atlantic holocene ice rafting events reported by bond et al 1997

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

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

holocene records of effective precipitation in west greenland holocene changes in effective precipitation precipitation evaporation p e were reconstructed for the sondre stromfjord region of southwest greenland using the sediment records of two neighbourin

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

magnetic susceptibility patterns and provenance of ice rafted material at feni drift rockall trough implications for the history of the british irish ice sheet abstract piston core enam 97 09 from feni drift atlantic margin west of ireland provides a record of ird input variability and provenance during the last 250 000 yrs the ird patterns can be related to late devensian detrital carbonate and meta sedimentary rock fragments represent two major ird types which were dominantly derived from irish inland ice and the irish sea ice stream respectively additional evidence for the latter source is based on heavy mineral data input from other circum north atlantic ice sheets notably the laurentide ice sheet is minor compared to british irish ird at least during periods of maximum expansion of the biis this is consistent with the marginal location of the core site with reference to the main north atlantic ird belt on the other hand laurentide ird presumably accounts for minor ird peaks at times of reduced ice volume in the british isles the main magnetic susceptibility peak during late isotope stage 2 termination i can be related to ird input from the laurentide ice sheet following early decay of the biis a similar pattern is observed during oxygen isotope stage 6 these observations are consistent with recent provenance studies indicating that only laurentide ird carries a strong magnetic susceptibility signal

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

paleoceanographical development off sisimiut west greenland during the mid and late holocene a multiproxy study abstract a multiproxy study of paleoceanographic and climatic changes in holsteinsborg dyb on the west greenland shelf shows that the area is sensitive to variations in the mixing between the two components of the west greenland current i e the atlantic water of the irminger current and the polar water from the east greenland current a seismic profile illustrates the general development in the area since the deglaciation and analyses of benthic foraminifera stable isotopes 18 o and 13 c and x ray fluorescence elemental counts in two cores covering ca 6650 and 1100 years respectively provide details on the oceanographic changes during the mid and late holocene the chronology is based on 210 pb and ams 14 c age determinations during the time interval of 6650 1600 cal yr bp the bottom waters are characterized by the presence of modified atlantic water with some influence of meltwater either local or regional depleted 18 o values and relatively high si fe ratio suggest warmer conditions from 6650 to 3800 cal yr bp corresponding in time to part of the holocene thermal maximum followed by a general slight cooling with some fluctuation after 3800 cal yr bp at 1600 cal yr bp there is an abrupt change in almost all investigated proxies the foraminiferal assemblage and the 18 o values suggest cold low salinity bottom water conditions and there is indication of seasonal sea ice cover between 1400 and 1200 cal yr bp corresponding in time to the dark ages cold period and to a minimum in solar irradiance from ca 1150 to 580 cal yr bp a time interval equivalent to the historical medieval warm period mwp the foraminiferal fauna remains indicative of cold low salinity bottom waters but without any indication of sea ice cover the influence of polar water meltwater at the sea floor during the mwp is thought to be a result of enhanced mixing of the two components of the west greenland current caused by an increase in wind activity during generally positive north atlantic oscillation conditions maybe combined with a displacement of the irminger current pathway to the outer shelf during the little ice age lia there is a strong influence of modified atlantic water at the sea floor related to sea ice formation and stratification of the water column after ad 1900 the benthic foraminiferal assemblage suggests a slight increase in polar water influence and thereby mixing even though the environment is not much different from that during the lia

hydrography and climate of the last 4400 years in a sw greenland fjord implications for labrador sea palaeoceanography a multiproxy record including benthic foraminifera diatoms and xrf data of a marine sedi ment core from a sw greenland fjord provides a detailed reconstruction of the oceanographic and cli matic variations of the region during the last 4400 cal years the lower part of our record represents the final termination of the holocene thermal maximum after the onset of the neoglaciation at approxi mately 3 2 ka cal bp the fjord system was subject to a number of marked hydrographical changes that were closely linked to the general climatic and oceanographic development of the labrador sea and the north atlantic region our data show that increased advection of atlantic water irminger sea water from the west greenland current into the labrador sea was a typical feature of northeast atlantic cool ing episodes such as the little ice age and the european dark ages while the advection of irminger sea water decreased significantly during warm episodes such as the mediaeval warm period and the roman warm period whereas the mediaeval warm period was characterized by relatively cool climate as suggested by low meltwater production the preceding dark ages display higher meltwater runoff and consequently warmer climate when compared with european climate these regional climate anomalies indicate persisting patterns of advection of colder respectively warmer air masses in the study region dur ing these periods and thus a long term seesaw climate pattern between west greenland and europe

the triassic palaeogeographic transition between the alpujarride and malaguide complexes betic rif internal zone s spain n morocco abstract various tectonic units situated between the malaguide and alpujarride complexes in the betic rif internal zone s spain and n morocco present triassic successions sharing features of both complexes the presence of which indicates a transitional domain these units which we term intermediate units are situated preferentially near the external limit of the betic rif internal zone generally adapted to the shape of the arc of gibraltar the palaeogeography of this area is reconstructed on the basis of the general geometric position of these units and their relationships with equivalent domains in the western mediterranean the scarce existing palaeomagnetic data and the directions of tectonic displacement the most problematic reconstructions concern those units on the n border of the betic rif zone as they have significant clockwise rotations up to 200 s and se tectonic displacements and a different geometric distribution from the rest of the units we conclude that in general the transition between the malaguide and alpujarride complexes was gradual the malaguide domain located s of the alpujarride with the intermediate units lying evidently between the two complexes

palynofacies analysis and organic walled dinoflagellate cysts in late holocene sediments from igaliku fjord south greenland this study characterizes late holocene past 3300 years variations in organic matter deposition in the outer part of igaliku fjord south greenland and uses this information to assess palaeohydrographic conditions except for two all residues were characterized by abundant organic matter with amorphous material dominating the late holocene sediments in the deeper parts of the outer igaliku fjord have generally been deposited under anoxic to suboxic conditions with relatively low terrestrial freshwater influx the organic walled dinoflagellate cyst assemblages suggest the continuous presence of water masses derived from the east greenland current while changes in sea surface temperature during the last 3300 years have also been interpreted terrestrial influx was reflected by the continuous occurrence of leaf tissue which increased in abundance in sediments younger than ad 960 pseudo amorphous phytoclasts occurred in sediments older than ad 770 and sporomorphs were rare throughout acritarchs and o

late holocene environment and climatic changes in ameralik fjord southwest greenland evidence from the sedimentary record sedimentological and geochemical xrf data together with information from diatom and benthic foraminiferal records of a 3 5 m long gravity core from ameralik fjord southern west greenland is used for reconstructing late holocene environmental changes in this area the changes are linked to large scale north atlantic ocean and climate variability ams 14c dating of benthic foraminifera indicates that the sediment core records the last 4400 years and covers the termination of the holocene thermal maximum htm the late htm 4 4 3 2 ka bp is characterized by high accumulation rates of fine silty sediments related to strong meltwater discharge from the inland ice the htm benthic foraminiferal fauna demonstrates the presence of well ventilated saline bottom water originating from inflow of subsurface west greenland current water of atlantic irminger sea origin the hydrographic conditions were further characterized by limited sea ice probably related to a mild and relatively windy winter climate af

variable north atlantic climate seesaw patterns documented by a late holocene marine record from disko bugt west greenland abstract the reconstruction of past sea surface conditions in the labrador sea is essential for understanding climate fluctuations in the north atlantic region we here study late holocene sea surface conditions off west greenland in order to elucidate the possible relationship between a north atlantic seesaw and centennial to millennial scale climate fluctuations in the labrador sea region for that purpose we have studied the particulate organic matter especially dinoflagellate cysts and acritarchs from two marine sediment cores from disko bugt central west greenland our data show significant variations in sea surface temperature and sea ice cover during the last ca 3200 years after a cooling at ca 2 9 ka cal bp presumably related to the neoglacial cooling seen in large parts of the northern hemisphere the area was subjected to significant variability both in the entrainment of atlantic water west greenland current water and in atmospheric temperatures from 2 0 1 5 ka cal bp corresponding to the later part of the roman warm period the area experienced a return to a stronger influx of atlantic water and an increased fresh water influx from land probably related to increased precipitation or to melt water outflow from the nearby inland ice the dark ages 1 5 1 3 ka cal bp were characterised by an only minor cooling of the surface waters however as seen in other records from the labrador sea region the beginning of the medieval warm period 1 3 0 9 ka cal bp signified a severe cooling presumably due to a significant reduction in atlantic water entrainment the cold conditions continued through the little ice age after 0 9 ka cal bp although the area seems to have experienced a minor decrease in sea ice cover until 0 5 ka cal b p after which sea ice cover may again have increased the period of modern warming is not represented in our data our study shows that a north atlantic oscillation type pattern played a significant role in the late holocene centennial to millennial scale climate fluctuations in the labrador sea region however this cannot explain the full complexity of the climate signal the fact that a simple pattern of cold versus warm climate scenario does not exist demonstrates that it will hardly be feasible to select the correct baseline data set when modelling future climate development

diatom evidence of hydrographic changes and ice conditions in igaliku fjord south greenland during the past 1500 years biostratigraphic diatom analyses were carried out on two sediment cores from igaliku fjord south greenland in order to reconstruct hydrographic and climatic fluctuations during the late holocene ad 550 to present pronounced differences in hydrographic setting of the coring sites provide palaeoenvironmental information of both local and more regional character five diatom zones were identified from the subfossil diatom records each describing a hydrographic setting two major climate periods the mediaeval warm period ad 800 1250 and the little ice age ad 1580 1850 that were separated by a variable transitional period were recognized prior to these periods a cold and presumably moist climate regime prevailed between ad 500 and 700 cooling events were identified during the mediaeval warm period in the period ad 960 to 1140 the diatom data demonstrate that marked hydrographic changes occurred in the course of a relatively short timespan beginning at about ad 1300 and culminating around

a diatom based reconstruction of early holocene hydrographic and climatic change in a southwest greenland fjord abstract a diatom based reconstruction of surface water paleoclimatic and paleoceanographic changes in ameralik fjord southwest greenland is presented for the holocene interval 8800 to 3600 cal yrs b p a minor episode of cold surface water conditions is found at ca 8000 7800 cal yrs b p this may be due to the local conditions in the fjord and linked to the culmination of a strong melt water outflow rather than reflecting the widespread north atlantic 8 2 ka cooling event warming of surface water condition from 7800 to 7100 cal yrs b p probably corresponding to the early and warmest part of the holocene thermal maximum htm in this region is reflected in the diatom assemblages and supported by other proxies the west greenland current wgc influences the fjord strongly during this interval indicating enhanced advection of atlantic water masses derived from the irminger current ic a major sedimentary change with a hiatus between 6800 and 4400 cal yrs b p prevents a reconstruction of mid holocene paleoceanograpy the final and less prominent part of the htm is found after 4400 cal yrs b p previous studies from the same site have shown this final stage of the htm to end at 3200 cal yrs b p with the onset of the neoglaciation our study provides further evidence that the marine sedimentary record from west greenland fjords yields paleoenvironmental information reflecting a significant link between local and large scale north atlantic oceanographic and climatic changes

marine reservoir age variability and water mass distribution in the iceland sea abstract lateglacial and holocene tephra markers from icelandic source volcanoes have been identified in five sediment cores from the north icelandic shelf and correlated with tephra layers in reference soil sections in north iceland and the grip ice core land sea correlation of tephra markers that have been radiocarbon dated with terrestrial material or dated by documentary evidence provides a tool for monitoring reservoir age variability in the region age models developed for the shelf sediments north of iceland based on offshore tephrochronology on one hand and on calibrated ams 14c datings of marine molluscs on the other display major deviations during the last 4500 years the inferred temporal variability in the reservoir age of the regional water masses exceeds by far the variability expected from the marine model calculations the observed reservoir ages are generally considerably higher by up to 450 years than the standard model ocean it is postulated that the intervals with increased and variable marine reservoir age reflect incursions of arctic water masses derived from the east greenland current to the iceland sea and the north icelandic shelf

warming and freshening of baffin bay 1916 2003 1 regression analysis of historical hydrographic data is used to determine changes in temperature and salinity in baffin bay for the time period from 1916 to 2003 we find two distinct sets of changes in the baffin first areas affected by the atlantic inflow to baffin bay show substantial and statistically significant warming trends in the more than 2000 m deep basin the warming peaks at 0 11 0 06 c decade at 700 m depth below the 640 m sill depth of davis strait connecting baffin bay to the north atlantic ocean a vertical heat flux divergence of 0 25 w m2 is required to warm baffin bay below 900 m by the amount observed the required heat appears to be advected from the shelf and slope regions of the eastern labrador sea via davis strait along the west greenland shelf break and diffuses vertically and horizontally into the deep central basin the north atlantic oscillation index accounts for about 30 of the interannual variance of temperature fluctuations below the davis strait sill depth second areas affected by arctic inflow to baffin bay show a marginally significant freshening of up to about 0 086 0 039 psu decade this freshening trend extends along the western margin of baffin island to davis strait and into the labrador sea the freshening in the northern reaches of baffin bay is similar in size to that at its southern reaches temporal variability of annual composites between these locations appears to be in phase suggesting a swift transition of arctic waters at 76 n to labrador sea waters at 62 n

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

reconstructing holocene palaeoclimate and palaeoceanography in isafjarðardjup northwest iceland from two fjord records overprinted by relative sea level and local hydrographic changes we reconstruct palaeoclimate and palaeoceanography of the isafjar ardjup fjord system from two cores one from the inner fjord and one near the fjord mouth while separating the potential overprinting of relative sea level rsl and local fjord hydrographic changes on these records the inner fjord core b997 339 reflects local fjord hydrography the outer fjord core md99 2266 reflects the regional oceanic signal glacial marine conditions ended at ca 10 200 cal a bp indicated by both ice rafted debris records the other proxy records show spatial and temporal variability within the fjord system at the inner fjord site b997 339 foraminiferal assemblages and the 18o record indicate lowered rsl between ca 10 600 and 8900 cal a bp and document the onset of fjord water overturning at ca 8900 cal a bp which obscured the climate record at the fjord mouth md99 2266 mass accumulation rates suggest lowered rsl between ca 10 200 and 5500 cal a bp and local freshwater and or reduced salinities of the irminger current water masses affected the 18o signal between ca 10 200 and 7900 cal a bp at md99 2266 foraminiferal fauna record the holocene thermal maximum between ca 8000 and 5700 cal a bp and the onset of modern oceanic circulation at ca 7000 cal a bp copyright 2010 john wiley sons ltd

the 8200 cal yr bp event reflected in the arctic fjord van mijenfjorden svalbard detailed stratigraphic investigations of a high resolution sediment core from the arctic fjord van mijenfjorden svalbard reveal significant reductions in benthic foraminiferal 18o of 0 4 and 0 2 0 3 dated to c 8200 and 8450 cal yr bp respectively these reductions combined with changes in the benthic foraminiferal fauna and ird indicate substantial changes in the hydrography of the fjord such as freshening of the bottom water enhanced sea ice distribution and reduced biogenic production the age and duration 100 years of the youngest event is directly in phase with the 8200 cal yr anomaly in the 18o record gisp2 and ngrip of the greenland ice sheet the changes around 8450 cal yr bp compare well to the timing of the initial freshwater drainage of the proglacial lake agassiz therefore the proxy record of van mijenfjorden lends support to the theory explaining the 8200 cal yr bp event as a cumulative response to a freshwater forced reduction in the meridional overturning circulation in

interaction between subsurface ocean waters and calving of the jakobshavn isbrae during the late holocene a marine sediment core from vaigat in disko bugt west greenland has been analysed in terms of lithology dinoflagellate cysts and foraminifera in order to evaluate the influence of oceanographic variability on west greenland glacier stability the data show that during the past 5200 years the atlantic foraminiferal abundance in the subsurface waters of the west greenland current wgc episodically increased indicating periods of increases in the inflow of subsurface warm atlantic water at 2000 1500 cal yr bp and 1300 cal yr bp as well as periods of less pronounced increased bottom water temperatures around 4700 4000 cal yr bp 3100 2800 2600 1000 800 500 400 and at 200 cal yr the sedimentological and dinoflagellate cyst data indicate that these episodes with enhanced advection of irminger sea derived waters are accompanied by increased iceberg rafting which we link to increased iceberg calving in relation to destabilization of the jakobshavn isbrae the long term trend in the data documents the end of a late holocene thermal maximum between 5200 and 4300 cal yr bp and a final onset of the neoglaciation at 3500 cal yr bp increased responses of the iceberg rafting after 3500 cal yr bp reflects a westward seaward advance of the glacier margin in relation to onset of neoglaciation and a development of the glacier into a floating tongue after 2000 cal yr bp a comparison of our record with a record from the eastern north atlantic indicates that a nao like anomaly pattern between subsurface waters in west greenland and atmospheric temperature in the eastern north atlantic may have been operating during most of the late holocene however during the past 1000 years the nao signal may have weakened as some other mode of climate variability overprints the anti phase climate signal in this region