precipitation regime of dronning maud land antarctica derived from antarctic mesoscale prediction system amps archive data 1 the precipitation regime of dronning maud land dml antarctica was studied using antarctic mesoscale prediction system amps archive data precipitation is the most important component of the mass balance of the antarctic ice sheet precipitation studies of dml are particularly important because two deep ice core drilling sites kohnen station and dome fuji are located in this region for the correct interpretation of the ice core properties a thorough understanding of the precipitation regime is necessary we used the high resolution amps archive data for the years 2001 2006 to investigate the temporal and spatial distribution of precipitation the results were compared to a recently published mass balance map derived from glaciological data of western dml the mass balance map and the amps mean annual precipitation field show fairly similar patterns which are mostly related to topography and prevailing wind systems precipitation is found to generally decrease from the coast to the inland plateau along the escarpment between the low altitude coastal areas and the interior plateau local minima and maxima in precipitation correspond to the leeward and windward sides of topographical ridges interannual variability of monthly sums of precipitation is fairly high owing to the influence of cyclone activity on precipitation which affects not only the coastal regions but also the interior of the continent more than previously thought

a seismic event on august 20 1983 double explosion or a single earthquake abstract an interesting weak seismic event occurred on august 20 1983 in the caspian sea region in southwestern u s s r which produced at gauribidanur array two distinct seismic signals viz the leading p signal and a similar signal after an interval of nearly 12 s preliminary data corresponding to these two signals led to an initial assumption that the event was a double underground nuclear explosion however the focal depth of this event from p arrival time data of 21 stations was found to be 45 km further processing of the gauribidanur array seismograms confirmed that the second signal detected exactly 11 85 s after the first arrival was none other than the surface reflected p pulse which lent excellent support to the source depth estimate by using three discriminants viz signal complexity third moment of frequency and relative efficiency of generation of core reflected p the event was objectively compared with 10 small presumed underground nuclear explosions in southwestern u s s r to conclude that the august 20 1983 event was a shallow focus small earthquake in the caspian sea area

warming trends in the continental shelf of malaga bay alboran sea 1 temperature time series from 1992 to 2001 ecomalaga project show an intense warming trend in deep layers 200m depth of malaga bay 0 02 c yr data from medatlas show that this trend is 0 005 c yr throughout the whole century another striking change in malaga bay is the disappearance of the cold western intermediate water wiw after 1992 this could be the responsible of temperature changes in the malaga continental shelf

the advection of submesoscale thermal features in the alboran sea gyre abstract noaa 7 infrared and nimbus 7 multi spectral visible imagery of the alboran sea collected as part of the donde va experiment during the period 6 20 october show the advection of submesoscale cold water features about the alboran sea gyre continuous monitoring of thew cold water features using satellite imagery is possible because of the twice daily every 12 h spacing of the noaa 7 coverage of the area after registration to a mercator projection and atmospheric correction analysis of the displacement of the cold water features in successive images shows their apparent origin to be just east of gibraltar their movement at average speeds of 0 4 m s 1 around the gyre and their apparent re entrainment into the incoming atlantic water east of gibraltar the nimbus 7 czcs imagery supplements the analysis by adding details of the movement and the theory on where the cold water features originate during the 15 day period nine cold water features were thermally distinct enough to be tracked for

the sapropel record of the eastern mediterranean sea results of ocean drilling program leg 160 research on sediments recovered during ocean drilling leg 160 has concentrated on two issues the first concerned the stratigraphy of sapropel formation the second was oriented to clarify specific processes that explain sapropel origin progress has been made in the construction of stratigraphic composites out of sedimentary sequences from individual holes at each of the palaeoceanographic sites on the composites initial work has resulted in the establishment of high resolution and intermediate resolution stratigraphies for three sites 963 964 967 correlation of sedimentary cycles to astronomical insolation cycles extends the stratigraphies to sites 969 and 966 the sapropel occurrences in the marine and land sequences over the entire eastern mediterranean are correlated with the resolution that can be obtained from isotope studies groups of sapropels occurred simultaneously over the entire basin in detail however the temporal and facies patterns of sapropel sequences differ between individual sites and depositional basins the differences may be related to effects of water depth diagenesis and post depositional tectonic attenuation of sequences studies on the geochemistry and facies of sapropels agree that anoxic conditions favoured preservation of organic matter in sapropels caused the enrichment of trace metals associated with sapropels and helped to preserve primary sedimentary structures besides all evidence is consistent with elevated fluxes of organic matter and associated elements during sapropel events

a new surface accumulation map for western dronning maud land antarctica from interpolation of point measurements as a result of intensive field activities carried out by several nations over the past 15 years a set of accumulation measurements for western dronning maud land antarctica was collected based on firn core drilling and snow pit sampling this new information was supplemented by earlier data taken from the literature resulting in 111 accumulation values using geographical information systems software a first region wide mean annual snow accumulation field was derived in order to define suitable interpolation criteria the accumulation records were analyzed with respect to their spatial autocorrelation and statistical properties the resulting accumulation pattern resembles well known characteristics such as a relatively wet coastal area with a sharp transition to the dry interior but also reveals complex topographic effects furthermore this work identifies new high return shallow drilling sites by uncovering areas of insufficient sampling density

marine isotope stage 11 palaeoclimates palaeoenvironments and its role as an analogue for the current interglacial abstract interglacials of the quaternary period are currently the focus of a great deal of attention within the scientific community this is primarily because they play a vital role in distinguishing between natural and human climate change in the current interglacial and in understanding how the holocene would evolve in the absence of anthropogenic greenhouse warming in this respect marine isotope stage 11 mis 11 ca 410 000 yr bp is one of the key interglacial stages of the past 450 000 yr the pattern of insolation variability that occurs during mis 11 matches that which occurs in the holocene more closely than in any other warm stage of the past half a million years in addition there is now an extensive range of evidence for mis 11 palaeoclimates and palaeoenvironments from marine ice core lacustrine and terrestrial sequences the aim of this paper is to provide a comprehensive review of the current state of our understanding of mis 11 this is the first paper to provide a detailed review of mis 11 that incorporates the wide range of marine ice core long lacustrine and terrestrial records that have been generated over the last ten years since the last major overview crucially it is the first review of mis 11 that incorporates a detailed synthesis of the high resolution terrestrial sequences of western and central europe this paper therefore provides a holistic integration of a diverse range of proxies and archives to provide a detailed understanding of the expression of mis 11 in the earth system in particular the review focuses on 1 the climatic background of mis 11 2 the robustness of the identification of mis 11 in a diverse range of sequences 3 the climatic structure of mis 11 4 the magnitude of warmth that occurred in this warm stage 5 mis 11 sea level magnitude and variability 6 the duration of mis 11 7 evidence for abrupt climatic events within the interglacial of mis 11 and 8 precipitation patterns and trends during this interglacial the paper concludes by considering how useful mis 11 is as an analogue for holocene climates and compares it with other proposed analogues such as mis 19 with particular reference to the early anthropogenic hypothesis

four climate cycles of recurring deep and surface water destabilizations on the iberian margin centennial climate variability over the last ice age exhibits clear bipolar behavior high resolution analyses of marine sediment cores from the iberian margin trace a number of associated changes simultaneously proxies of sea surface temperature and water mass distribution as well as relative biomarker content demonstrate that this typical north south coupling was pervasive for the cold phases of climate during the past 420 000 years cold episodes after relatively warm and largely ice free periods occurred when the predominance of deep water formation changed from northern to southern sources these results reinforce the connection between rapid climate changes at mediterranean latitudes and century to millennial variability in northern and southern polar regions

the role of seasonality of mineral dust concentration and size on glacial interglacial dust changes in the epica dronning maud land ice core we present a record of particulate dust concentration and size distribution in subannual resolution measured on the european project for ice coring in antarctica epica dronning maud land edml ice core drilled in the atlantic sector of the east antarctic plateau the record reaches from present day back to the penultimate glacial until 145 000 years b p with subannual resolution from 60 000 years b p to the present mean dust concentrations are a factor of 46 higher during the glacial 850 4600 ng ml compared to the holocene 16 112 ng ml with slightly smaller dust particles during the glacial compared to the holocene and with an absolute minimum in the dust size at 16 000 years b p the changes in dust concentration are mainly attributed to changes in source conditions in southern south america an increase in the modal value of the dust size suggests that at 16 000 years b p a major change in atmospheric circulation apparently allowed more direct transport of dust particles to the edml drill site we find a clear in phase relation of the seasonal variation in dust mass concentration and dust size during the glacial r conc size 0 8 but no clear phase relationship during the holocene 0 r conc size 0 4 with a simple conceptual 1 d model describing the transport of the dust to the ice sheet using the size as an indicator for transport intensity we find that the effect of the changes in the seasonality of the source emission strength and the transport intensity on the dust decrease over transition 1 can significantly contribute to the large decrease of dust concentration from the glacial to the holocene

sea surface temperatures did not control the first occurrence of hudson strait heinrich events during mis 16 1 hudson strait hs heinrich events ice rafting events in the north atlantic originating from the laurentide ice sheet lis are among the most dramatic examples of millennial scale climate variability and have a large influence on global climate however it is debated as to whether the occurrence of hs heinrich events in the eastern north atlantic in the geological record depends on greater ice discharge or simply from the longer survival of icebergs in cold waters using sediments from integrated ocean drilling program iodp site u1313 in the north atlantic spanning the period between 960 and 320 ka we show that sea surface temperatures ssts did not control the first occurrence of hs heinrich like events in the sedimentary record using mineralogy and organic geochemistry to determine the characteristics of ice rafting debris ird we detect the first hs heinrich like event in our record around 643 ka marine isotope stage mis 16 which is similar as previously reported for site u1308 however the accompanying high resolution alkenone based sst record demonstrates that the first hs heinrich like event did not coincide with low ssts thus the hs heinrich like events do indicate enhanced ice discharge from the lis at the end of the mid pleistocene transition not simply the survivability of icebergs due to cold conditions in the north atlantic

influence of large scale atmospheric circulation on marine air intrusion toward the east antarctic coast marine air intrusions into antarctica play a key role in high precipitation events here we use shipboard observations of water vapor isotopologues between australia and syowa on the east antarctic coast to elucidate the mechanism by which large scale circulation influences marine air intrusions the temporal isotopic variations at syowa reflect the meridional movement of a marine air front they are also associated with atmospheric circulation anomalies that enhance the southward movement of cyclones over the southern ocean the relationship between large scale circulation and the movement of the front is explained by northerly winds which in association with cyclones move toward the antarctic coast and push marine air with isotopically enriched moisture into the inland covered by glacial air with depleted isotopic values future changes in large scale circulation may have a significant impact on the frequency and intensity of marine air intrusion into antarctica

phase relationship and surface water mass change in the northeast atlantic during marine isotope stage 11 mis 11 planktic foraminiferal census data faunal sea surface temperatures ssts and oxygen isotopic and lithic records from a site in the northeast atlantic were analyzed to study the interglacial dynamics of marine isotope stage mis 11 a period thought to closely resemble the holocene on the basis of orbital forcing interglacial conditions during mis 11 persisted for approximately 26 ka after the main deglacial meltwater processes ceased a 10 to 12 ka long transitional period marked by significant water mass circulation changes occurred before surface waters finally reached their thermal maximum this sst peak occurred between 400 and 397 ka inferred from the abundance of the most thermophilic foraminiferal species and was coincident with lowest sea level according to benthic isotope values the ensuing stepwise sst decrease characterizes the overall climate deterioration preceding the increase in global ice volume by 3 ka this cooling trend was followed by a more pronounced cold event that began at 388 ka and that terminated in the recurrence of icebergs at the site around 382 ka because the water mass configuration of early mis 11 evolved quite differently from that of the early holocene there is little evidence that mis 11 can serve as an appropriate analogue for a future holocene climate despite the similarity in some orbital parameters

a 20 m middle pleistocene sea level highstand bermuda and the bahamas due to partial collapse of antarctic ice marine deposits at 20 3 m on the tectonically stable coastlines of bermuda and the bahamas support the hypothesis of a partial collapse of the antarctic ice sheet during the middle pleistocene beach sediments fill a sea cave at 22 m in bermuda and horizontal fenestrae filled beds crop out on platforms at two sites as high as 21 m in eleuthera bahamas carbonate beach sands are bound by an early generation of isopachous fibrous cement that is characteristic of a phreatic marine environment amino acid racemization and tims thermal ionization mass spectrometry dates constrain the age of the deposits to between 390 and 550 ka while proxy evidence supports a correlation with oxygen isotope stage 11 this direct geologic evidence of a 20 decrease in polar ice during the middle pleistocene has important implications for the stability of ice sheets during warm interglaciations

planktonic foraminiferal assemblages in surface sediments from the southwest african continental margin abstract the relative abundance and distribution of planktonic foraminifera species on the southwest african continental margin have been determined from 152 surface sediment samples of the 23 recorded taxa only 8 make a significant contribution to the foraminiferal assemblages individual species proportions are closely related to the surface water hydrography of the benguela system and the associated upwelling phenomena three foraminiferal assemblages can be distinguished by correlation analysis on the abundances of the major taxa species composition of these assemblages range from polar taxa in the upwelling area left coiling neogloboquadrina pachyderma and globigerina quinqueloba to transitional taxa in the offshore oligotrophic environment globorotalia inflata and globorotalia truncatulinoides globigerina bulloides and right coiling neogloboquadrina pachyderma are preferentially distributed in the highly productive intermediate zone of the benguela system where upwelled and oligotrophic offshore waters mix variability of the hydrological processes upwelling intensity strength of the frontal features may be inferred from frequency variations of individual species and diversity patterns

late holocene climate variability in the adriatic sea central mediterranean planktic and benthic foraminifera assemblages from a set of sediment cores collected on the adriatic shelf and the southern adriatic deep basin provide compelling evidence of submillennial scale environmental changes during the last 6000 years repeated peaks in globigerinoides sacculifer represent warm dry intervals including the mediaeval warm period the roman age the late bronze age and the copper age the last occurrence lo of g sacculifer 550 years bp approximates the base of the little ice age lia significant turnovers in the structure of the water column reflect changes in the rate of formation and depth of flow of the north adriatic dense water naddw and the levantine intermediate water liw about 7500 years bp the benthic oxygen isotope records mark the timing when the naddw formation intensified on the slope and shifted to its modern route about 5500 years bp when sea level reached its modern high stand oxygen isotope records of intermediate planktic dwellers indicate a northward intrusion of the liw on the slope the oscillating isotope trends during the last five millennia document a discontinuous invasion of liw into the central adriatic possibly reflecting short term climate changes with weakened liw production during colder and wetter intervals

on the upper layer circulation in the alboran sea we present new experimental results and assemble them with previous results in order to develop an improved picture of the upper layer circulation in the alboran sea it is suggested that the key idea to understanding this upper layer circulation is the tendency of the atlantic jet aj to have negative curvature local interactions with the western alboran gyre wag or the african coast can however counterbalance this tendency and modify the anticyclonic path of the aj it is also proposed that the density gradients in the wag can be maintained in part by means of an intermittent surface cross gyre current which results in an input mixing and renewal of atlantic water the static stability at the bottom of the gyre increases because of the mixing of atlantic water with western mediterranean deep water which is uplifted close to the african coast this mixing process thereby acts as a local source of potential vorticity we also report the existence in the alboran sea of subsurface anticyclonic eddies located between 100 and 400 m of relatively cold water that appear to be detached from the iberian shelf regarding the large scale variability of the aj wag system we present evidence of an eastward migration of the wag and the subsequent formation of a new anticyclonic gyre in the western alboran basin on a timescale of 1 month this eastward gyre migration process temporarily allows the simultaneous presence of three anticyclonic gyres in the alboran sea

millennial scale ice rafting events and hudson strait heinrich like events during the late pliocene and pleistocene a review abstract various types of abrupt millennial scale climate variability such as dansgaard oeschger and heinrich events characterized the last glacial period over the last decade a number of studies demonstrated that such millennial scale climate variability was not limited to the last glacial but inherent to quaternary climate here we review the occurrence and origin of millennial ice rafting events in the north atlantic during the late pliocene and pleistocene last 3 4 ma with a special focus on north atlantic hudson strait hs heinrich like events we show that heinrich layers 5 4 2 and 1 in marine sediment cores from across the north atlantic all bear the organic geochemical fingerprint of the hudson area using this framework and combining previously published results detailed investigations into the organic and inorganic chemistry of ice rafted debris ird found across the north atlantic demonstrate that prior to mis 16 650 ka ird in the north atlantic did not originate from the hudson area of northern canada the signature of this early ird is distinctly different compared to that of hs heinrich layers rather ice rafting events during the late pliocene and early pleistocene predominantly emanated from the calving of the greenland and fennoscandian ice sheets and possibly minor contributions from local ice streams from the north american and british ice sheets compared to north atlantic hs heinrich events these early pleistocene ird events had a limited impact on surface water characteristics in the north atlantic north atlantic hs heinrich like events first occurred during mis 16 at the same time the dominant frequency in silicate rich ird accumulation shifted from the obliquity 41 ka to a 100 ka frequency across the north atlantic iceberg survivability or a change in iceberg trajectory likely did not control this change in ird regime these results lend further support for the existing hypothesis that an increase in size thickness of the laurentide ice sheet controls the occurrence of north atlantic hs heinrich events favoring an internal dynamic mechanism for their occurrence

ocean surface water response to short term climate changes revealed by coccolithophores from the gulf of cadiz ne atlantic and alboran sea w mediterranean the response of coccolithophore assemblages to short term millennial and centennial climatic changes over the last 50 kyr is studied in core m39029 7 from the gulf of cadiz atlantic ocean and core md95 2043 from the alboran sea western mediterranean sea the nannoplankton data are compared with oxygen isotopes u37k sst and other biogeochemical and sedimentological proxies to obtain a new perspective of the paleoceanography and paleoecology of the area during these short term climatic changes coccolithophores indicate that heinrich events he were characterised by the presence of cold low salinity and turbid water masses on both sides of the strait of gibraltar high abundances of the lower photic zone lpz species florisphaera profunda in the gulf of cadiz synchronous with he are interpreted as being an evidence of upper water column stratification on the atlantic side these episodes coincided with input of terrigenous material especially during h2 surface waters during dansgaard oeschger do stadials were also cold and turbid while most of do interstadials were characterised by warm water flora the increase in small placoliths small gephyrocapsa and emiliania huxleyi 4 m which is considered here as a cold water indicator the sharp decrease in large specimens of e huxleyi related to the warming trend in the last deglaciation can be used as a biostratigraphic reference level that marks at least approximately the deglaciation and the beginning of the holocene peaks of f profunda are observed during termination 1 t1 in the alboran sea they are isochronous with the organic rich layer 1 recognised in the western mediterranean in this interval the water column of the region was stratified as a consequence of the global increase in the sea level following the deglaciation quantitative analyses of the coccolithophore assemblage allow us to interpret that coccolithophore production has been higher in the alboran sea than in the gulf of cadiz during the holocene

arctic front shifts in the subpolar north atlantic during the mid pleistocene 800 400ka and their implications for ocean circulation abstract surface water conditions at the integrated ocean drilling program iodp site u1314 southern gardar drift 56 21 8 n 27 53 3 w 2820 m depth were inferred using planktic foraminifer assemblages between marine isotope stage mis 19 and 11 ca 800 400 ka factor analysis of the planktic foraminifer assemblages suggests that the assemblage was controlled by three factors the first factor which explained 49 of the variance is dominated by transitional and subpolar species and points to warm and salty surface water conditions atlantic water the second factor 37 is dominated by neogloboquadrina pachyderma sin and has been associated with the presence of cold and low saline surface waters arctic water finally the third factor 9 linked to a significant presence of turborotalita quinqueloba reflects the closeness of the arctic front the boundary between atlantic and arctic water the position of the arctic and polar fronts has been estimated across the glacial interglacial cycles studied according to planktic foraminifer abundances from site u1314 and their factor analysis combined with a synthesis of planktic foraminifer and diatom data from other north atlantic sites regarding at the migrations of the arctic front and the surface water masses distribution across each climatic cycle we determined five phases of development furthermore deep ocean circulation changes observed in glacial interglacial cycles have been associated with each phase the high abundance of transitional subpolar foraminifers above 65 at site u1314 during the early interglacial phase indicated that the arctic front position and surface water masses distribution were similar to present conditions during the late interglacial phase n pachyderma sin and t quinqueloba slightly increased indicating that winter sea ice slightly expanded southwestwards whereas the ice volume remained stable or was still decreasing n pachyderma sin increased rapidly above 65 at site u1314 at the first phase of glacial periods indicating the expansion of the arctic waters in the western subpolar north atlantic during the second phase of glacial periods the transitional subpolar assemblage throve again in the central subpolar north atlantic associated with strong warming events that followed ice rafting events the third phase of glacial periods corresponds to full glacial conditions in which n pachyderma sin dominated the assemblage for the whole subpolar north atlantic this division in phases may be applied to the last four climatic cycles

surface cyclones in the era 40 dataset 1958 2001 part i novel identification method and global climatology abstract a novel method is introduced to generate climatological frequency distributions of meteorological features from gridded datasets the method is used here to derive a climatology of extratropical cyclones from sea level pressure slp fields a simple and classical conception of cyclones is adopted where a cyclone is identified as the finite area that surrounds a local slp minimum and is enclosed by the outermost closed slp contour this cyclone identification procedure can be applied to individual time instants and climatologies of cyclone frequency fc are obtained by simple time averaging therefore unlike most other climatologies the method is not based on the application of a tracking algorithm and considers the size of cyclones in combination with a conventional cyclone center tracking algorithm that allows the determination of cyclone life times and the location of cyclogenesis and cyclolysis additional frequency fields can be obtained for special categories of cyclones that are gener

variability of surface water characteristics and heinrich like events in the pleistocene midlatitude north atlantic ocean biomarker and xrd records from iodp site u1313 mis 16 9 1 a reconstruction of milankovitch to millennial scale variability of sea surface temperature sst and sea surface productivity in the pleistocene midlatitude north atlantic ocean marine isotope stage mis 16 9 and its relationship to ice sheet instability was carried out on sediments from integrated ocean drilling program iodp site u1313 this reconstruction is based on alkenone and n alkane concentrations u37k index total organic carbon toc and carbonate contents x ray diffraction data magnetic susceptibility and accumulation rates increased input of ice rafted debris occurred during mis 16 12 and 10 characterized by high concentrations of dolomite quartz and feldspars and elevated accumulation rates of terrigenous matter minimum input values of terrigenous matter on the other hand were determined for mis 13 and 11 peak values of dolomite coinciding with quartz plagioclase and kalifeldspar peaks and maxima in long chain n alkanes indicative for land plants are interpreted as heinrich like events related to sudden instability of the laurentide ice sheet during early and late deglacial phases of the glacials the coincidence of increased toc values with elevated absolute concentrations of alkenones suggests increased glacial productivity probably due to a more southern position of the polar front alkenone based sst reached absolute maxima of about 19 c during mis 11 3 and absolute minima of 10 c during mis 12 and 10 within mis 11 prominent cooling events mis 11 22 and 11 24 occurred the absolute sst minima recorded directly before and after the glacial maxima mis 10 2 and 12 2 are related to heinrich like event meltwater pulses as supported by the coincidence of sst minima and maxima in c37 4 alkenones and dolomite these sudden meltwater pulses especially during terminations iv and v probably caused a collapse of phytoplankton productivity as indicated by the distinct drop in alkenone concentrations ice sheet disintegration and subsequent surges and outbursts of icebergs and meltwater discharge may have been triggered by increased insolation in the northern high latitudes

winter warming over dome fuji east antarctica and semiannual oscillation in the atmospheric circulation an abrupt warming was observed in the winter around dome fuji 3810 m above sea level asl in east antarctica the air temperature increased from 73 c to 36 c in two days from june 13 to 14 1994 warming occurred first in the coastal region near the lambert glacier east antarctica then progressed inland to dome fuji during the warming a blocking high was observed in the middle troposphere and it persisted for several weeks this circulation pattern brought warm air inland a blocking high over east antarctica also appeared in the upper troposphere this high pressure area corresponded to a ridge of stratospheric circulation this condition occurred after a displacement of the polar vortex from east antarctica to west antarctica warming at the surface of the ice sheet occurred suddenly however in the stratosphere the circulation pattern began to change on a seasonal scale prior to the warming as part of the first phase of the semiannual oscillation

atmospheric meridional moisture flux over the southern ocean a story of the amundsen sea abstractthe antarctic ice sheet constitutes the largest reservoir of freshwater on earth representing tens of meters of sea level rise if it were to melt completely however because of the remote location of the continent and the concomitant sparse data coverage much remains unknown regarding the climate variability in antarctica and the surrounding southern ocean this study uses the high resolution ecmwf interim re analysis era interim data during 1979 2010 to calculate the meridional moisture transport associated with the mean circulation planetary waves and synoptic scale systems the resulting moisture flux which is dominated by the synoptic scales is largely consistent with results from theoretical assumptions and previous studies here high interannual and regional variability in the total meridional moisture flux is found with no significant trend over the last 30 years further the variability of the meridional moisture flux cannot be explained by the southern annular mode or el nino

changes in planktic and benthic foraminifer assemblages in the gulf of lions off south france response to climate and sea level change from mis 6 to mis 11 1 a multidisciplinary study involving micropaleontological and geochemical tools was carried out in borehole prgl1 promess 1 with the aim of reconstructing the impact of climate change and sea level variation between 133 ka and 406 ka in the upper slope of the gulf of lions we used factor analysis to obtain three main benthic assemblages related to eutrophic mesotrophic and oxygenated environments planktic foraminifers were grouped as warm water and cold turbulent species these results were compared with records of caco3 and major and trace elements al ca k sr as well as the c n ratio of organic matter power and cross spectral analysis showed a straightforward relationship between precession minima and thermal stratification of the water column as well as the occurrence of eutrophic bottom conditions during lowstand periods and mesotrophic environments at times of highstand these eutrophic mesotrophic oscillations usually driven by global eustatic change also involved regional variations in caco3 source to this environment during periods of precession maxima enhancement of northwesterly winds increased primary productivity by mixing enhancing the percentage of cold turbulent species in the water column and the proportion of oxygenated benthic species on the bottom during interglacial stages these events were recorded by lower biogenic carbonate at the expense of higher silicate related components most likely due to a higher supply from pyrenees rivers the record of oxygenated benthic species can be a good proxy to monitor past changes in winter intermediate water dynamics driven by northwesterly winds

western mediterranean planktonic foraminifera events and millennial climatic variability during the last 70 kyr abstract detailed study of associations of planktonic foraminifera in cores md95 2043 and odp 977 located in the alboran sea mediterranean sea has allowed the identification of 29 new faunal events defined by abrupt changes in the abundances of neogloboquadrina pachyderma right and left coiling turborotalita quinqueloba globorotalia scitula globorotalia inflata globigerina bulloides and globigerinoides ruber white and pink varieties the age model for odp 977 was based on that of md95 2043 cacho et al 1999 paleoceanogr 14 698 705 on the isotopic stratigraphy and on two ams 14c measurements sea surface temperatures ssts were estimated for the last 54 kyr using the modern analog technique mat and were compared with the ssts provided by the uk 37 method the uk 37 record is very similar to the mat annual mean temperature record for the last 8 kyr however for older times alkenone derived temperatures are consistently higher than the annual mat temperatures this offset may be due to an underestimation of the sst provided by the planktonic foraminiferal method for glacial times to an overestimation of the uk 37 record or to changes in the seasonal production of alkenones most of the variability in the fauna is related to the millennial variability of heinrich and dansgaard oeschger d o events during heinrich events hes and most of the other d o stadials g bulloides t quinqueloba and g scitula increased while n pachyderma right coiling g inflata and g ruber decreased by contrast n pachyderma left coiling was only abundant in the hes the main component of the associations n pachyderma right coiling follows a general trend similar to that of sea level and 18o this species reached its highest abundance during the last glacial maximum when sea level was at a lower position the occurrence of a shallower nutricline owing to a shallowing of the interface between atlantic inflowing and mediterranean outflowing waters could have favoured the development of neogloboquadrinids in the vicinity of the strait of gibraltar

calcareous nannofossil changes during the mid pleistocene revolution paleoecologic and paleoceanographic evidence from north atlantic site 980 981 abstract new quantitative data on calcareous nannofossil assemblages through 583 1138 thousand years ago kyr have been acquired in high sample resolution 2 3 ky at northern atlantic odp ocean drilling program site 980 981 assemblage composition reflects a temperate paleobioprovince suggesting significant influx of warm north atlantic current at the site location during the mid pleistocene transition between marine isotope stage mis 35 and 15 three intervals have been described based on changes in nannofossil composition and abundance fluctuations of taxa reticulofenestrids are abundant just in the first interval mis 35 22 which is also characterised by the absence of gephyrocapsa 4 m and c pelagicus s l the latter occurring in upper mis 24 only the second interval corresponds to the expanded warm mis 21 that is accompanied by high carbonate content absence of both nannofossil reworking and ice rafted debris ird higher abundance of c leptoporus 5 8 m and h carteri and absence of c pelagicus s l and medium gephyrocapsids the third interval mis 20 15 records the occurrence of c pelagicus s l and medium gephyrocapsa generally higher abundance and higher amplitude fluctuations of helicoliths and absence of reticulofenestrids the major changes in nannofossil assemblages seem to be the result of combined paleoenvironmental factors related to sea surface water features temperature and nutrient availability sea ice cover and possibly to deep and intermediate water production of both northern and southern hemisphere origin during glacial and interglacial phases complex inter relationships between environmental parameters and evolutionary ecological factors are inferred to explain the patterns of coccolithus pelagicus subspecies whose distribution and abundance fluctuations are compared with the available patterns of turborotalia quinqueloba and neogloboquadrina pachyderma left coiled at site 980 and with the c pelagicus subspecies patterns from north atlantic dsdp deep sea drilling project site 607 and south atlantic odp site 1090 data collected provide additional information on stratigraphic distribution of selected taxa the first occurrence fo of gephyrocapsa omega is confirmed as a diachronous event even in the atlantic ocean while the first and last common occurrence fco lco of r asanoi appear as diachronous and synchronous events respectively on a global scale

synchroneity between marine and terrestrial responses to millennial scale climatic variability during the last glacial period in the mediterranean region land sea climatic proxies have been obtained from the last glacial section of images core md95 2043 western mediterranean sea vegetation and alkenone derived sst curves indicate rapid 150 years and synchronous terrestrial and marine climatic changes paralleling the dansgaard oeschger d o climatic variability over greenland this frequency of climate change can be related to shifts between the two modes of operation of the north atlantic oscillation nao transfer functions applied to the pollen data indicate that there was an amplification of the climatic signal during heinrich events hes in comparison with other d o stadials the development and persistence of both scandinavian and atlantic mobile polar highs over southwestern europe may explain the extreme cooling 10 c and dryness 400 mm during heinrich events 5 and 4 in the mediterranean region comparison of the results of core md95 2043 with similar climatic data from images core md95 2042 located off portugal indicates that thermal and precipitation gradients occurred between the mediterranean and the atlantic sides of iberia within hes hes 4 and 5 are associated with more humid conditions in the atlantic by 200 mm than in the mediterranean site as is the case at the present time this comparison also illustrates the different behaviour of these areas during the d o stadials in contrast with the mediterranean site the atlantic site shows similar precipitation and temperature drops for all the d o stadials including those related to the hes here we propose the operation of different mobile polar highs mph as the driving mechanism for this difference in behaviour between the atlantic and mediterranean sides of iberia hes are related to a stronger influence of the scandinavian mph forcing a severe aridification and cooling of the full iberian peninsula the atlantic mph may have been dominant during the other stadials which would preferentially affect southwestern iberia

a middle pleistocene northeast atlantic coccolithophore record paleoclimatology and paleoproductivity aspects abstract changes in paleoclimate and paleoproductivity patterns have been identified by analysing in conjunction with other available proxy data the coccolithophore assemblages from core md03 2699 located in the portuguese margin in the time interval from the marine isotope stage mis 13 14 boundary to mis 9 535 to 300 ka during the mid brunhes event the assemblages associated with the eccentricity minima are characterised by higher nannoplankton accumulation rate nar values and by the blooming of the opportunistic genus gephyrocapsa changes in coccolithophore abundance are also related to glacial interglacial cycles higher nar and numbers of coccoliths g mainly occurred during the interglacial periods while these values decreased during the glacial periods superimposed on the glacial interglacial cycles climatic and paleoceanographic variability has been observed on precessional timescales the structure of the assemblages highlights the prevailing long term influence of the portugal pc and iberian poleward ipc currents following half and full precession harmonics related to the migration of the azores high ah pressure system small gephyrocapsa and coccolithus pelagicus braarudii are regarded as good indicators for periods of prevailing pc influence gephyrocapsa caribbeanica syracosphaera spp rhabdosphaera spp and umbilicosphaera sibogae denote periods of ipc influence our data also highlights the increased percentages of coccolithus pelagicus pelagicus during the occurrence of episodes of very cold and low salinity surface water probably related to abrupt climatic events and millennial scale oscillations of the ah icelandic low il system

rossby wave packets on the midlatitude waveguide a review abstractrossby wave packets rwps are rossby waves for which the amplitude has a local maximum and decays to smaller values at larger distances this review focuses on upper tropospheric transient rwps along the midlatitude jet stream their central characteristic is the propagation in the zonal direction as well as the transfer of wave energy from one individual trough or ridge to its downstream neighbor a process called downstream development these rwps sometimes act as long range precursors to extreme weather and presumably have an influence on the predictability of midlatitude weather systems the paper reviews research progress in this area with an emphasis on developments during the last 15 years the current state of knowledge is summarized including a discussion of the rwp life cycle as well as rossby waveguides recent progress in the dynamical understanding of rwps has been based in part on the development of diagnostic methods these methods include algorithms to identify and track rwps

clues from mis 11 to predict the future climate a modelling point of view simulations performed with the lln two dimensional northern hemisphere climate model have confirmed that climate is largely triggered by changes in insolation forcing although atmospheric co concentration also plays an important role in particular in the amplitude of the simulated variations marine isotope stage 11 mis 11 some 400 kyr ago and the future share a common feature related to climate forcing i e the insolation at these times displays small similar variations mis 11 can be considered an analogue for future natural climate changes different simulations were performed to identify the conditions constraining the length of the mis 11 simulated interglacial clearly its length strongly depends on the phase relationship between insolation and co2 variations it is only when insolation and co act together towards a cooling i e they both decrease together that the climate enters quickly into glaciation and that the interglacial may be short otherwise each forcing alone is not able to drive the system into glaciation and the climate remains in an interglacial state the same situation applies for the future however we already know that co2 and insolation do not play together indeed insolation has been decreasing since 11 kyr bp and co2 concentration remains above 260 ppmv with a general increasing trend over the last 8000 yr therefore we conclude that the long interglacial simulated for the future is a robust feature and the earth will not enter naturally into glaciation before 50 kyr ap c 2003 elsevier science b v all rights reserved

planktonic response to main oceanographic changes in the alboran sea western mediterranean as documented in sediment traps and surface sediments abstract in order to determine the influence of seasonal oceanographic changes to the export of particulates and the flux of organisms as well as its corresponding integrated signal left in the bottom sediments of the alboran sea western mediterranean two mooring lines alb 1f and alb 1d were deployed from july 1997 to may 1998 on the continental slope south of malaga at 36 01 n 04 16 w and 36 14 n 04 28 w and a water depth of 1004 and 958 m respectively the mooring locations are under the influence of the incoming atlantic surface water asw at the northern and productive edge of the western alboran gyre wag and of the wind induced upwelling offshore the spanish coast additionally a total of five core tops located in the same area were studied the results are compared to information based on seawifs images of chlorophyll a concentration sst meteorological data on wind direction and intensity and fluvial discharges from the main rivers of the alboran basin the temporal oceanographic evolution of the alboran sea during the studied period was divided into five episodes e1 july 1997 e2 august october 1997 e3 november to mid december 1997 e4 december march 1998 and e5 april may 1998 the episodes represent different oceanographic conditions in the alboran sea during the studied period detailed analyses of the recorded pattern of bulk components calcareous nannoplankton planktonic foraminifera diatoms and phytoliths reflect seasonal changes in the main hydrographic regimes in the western alboran sea all biogenic bulk components as well as the annual evolution of the floral and faunal assemblages follow a tri modal pattern with maximum fluxes recorded during e1 e3 and e5 representing periods of higher productivity and wind induced upwelling during these periods species such as the small gephyrocapsa group gephyrocapsa muellerae and calcidiscus leptoporus the foraminifer globigerina bulloides and the diatom chaetoceros resting spores rs were dominant gephirocapsa oceanica and globorotalia inflata were coupled to the evolution of the atlantic surface water asw or related to surface water stability e2 and e4 the diatom leptocylindrus danicus responded to upwelling relaxation and water stratification e1 e2 and e4 and benthic diatoms were related to eddy intensity at bottom phytolith fluxes were directly related to wind intensities and the prevailing westerly winds e3 and e5 the distribution of microfossils in surface sediments differs from the biogenic assemblages recorded in the sediment traps in this sense during 1997 1998 the strongest el nino event in the last century took place which could have forced an unusual seasonality in the alboran sea reflecting an exceptional micropaleontological signal not observed in the surface sediments

calcareous plankton response to orbital and millennial scale climate changes across the middle pleistocene in the western mediterranean abstract the paleoenvironmental conditions through mis 15 9 at the mediterranean ocean drilling program odp site 975 were interpreted by high resolution study of calcareous plankton assemblages compared with available 18o and 13c records and high resolution paleoclimate proxies from the atlantic ocean sea surface temperatures ssts have been estimated from planktonic foraminiferal assemblages using the artificial neural networks method calcareous plankton varied dominantly on a glacial interglacial scale as testified by the sst record foraminiferal diversity total coccolith abundance and changes in warm water calcareous nannofossil taxa a general increase in foraminiferal diversity and of total coccolith abundance is observed during interglacials warmest ssts are reached during mis 11 while mis 12 and mis 10 represent the coldest intervals of the studied record during mis 12 one of the most extreme glacials of the last million years occurrence of globorotalia inflata and of neogloboquadrinids indicates a shoaling of the interface between atlantic inflowing and mediterranean outflowing waters among calcareous nannofossils the distribution of gephyrocapsa margereli gephyrocapsa muellerae 4 m also supports a reduced atlantic mediterranean exchange during mis 12 superimposed on glacial interglacial variability six short term coolings are recognized during mis 12 and 10 which appear comparable in their distribution and amplitude to the heinrich type events documented in the atlantic ocean in the same interval during these h type events neogloboquadrina pachyderma s and g margereli g muellerae 4 m increase as a response to the enhanced inflow of cold atlantic water into the mediterranean via the strait of gibraltar mediterranean surface water hydrography appears to have been most severely affected at termination v during the h type event ht4 possibly as a response to a large volume of atlantic meltwater inflow via the strait of gibraltar and or to freshwater terrigenous input deriving from local mountain glaciers three additional sst coolings are recorded through mis 14 16 but these are not well correlated with heinrich type events documented in the atlantic ocean in the same interval during these cooling episodes only the subpolar turborotalita quinqueloba increases these results highlight the sensitive response of the mediterranean basin to millennial scale climate variations related to northern hemisphere ice sheet instability and support the hypothesis that the tight connection between high latitude climate dynamics and mediterranean sea surface water features can be traced through the middle pleistocene

calcareous plankton and the mid brunhes climate variability in the alboran sea odp site 977 abstract quantitative calcareous plankton analyses have been performed at the ocean drilling program site 977 in the alboran sea through the mid brunhes interval 300 540 ka the results evidence orbital suborbital and millennial scale climate variability which primary reflects temperature change the patterns of increase decrease of coccolithophore and planktonic foraminifera warm water taxa reproduce the stage and substage climate variability in the planktonic 18o in good agreement with other planktonic isotope records from mediterranean sea and atlantic ocean variable conditions characterized by alternating cool nutrient rich or warm and stable sea surface waters occurred during interglacial marine isotope stage mis 13 in response to high amplitude oscillations of insolation during obliquity maximum and to north africa monsoon strength influencing distribution of taxa mis 13a resulted warmer than mis 13c based on the higher abundances of warm water taxa they increase just after insolation maxima suggesting a primary response of calcareous plankton to precessional orbital control following short term warm mis 11e and more humid mis 11d phases a climate optimum lasting about 16 kyr is recognized during mis 11c when major tropical subtropical water arrival into the alboran sea occurred as evidenced by the presence of trilobatus sacculifer mis 11c records unstable climate condition that persisted up to the late mis 11 indicating multiple pulses of southward migrations of subpolar front following the full interglacial mis 11c warm and oligotrophic conditions occurred during mis 9 as during mis 11 especially in mis 9e although without a climate optimum reduced abundance of warm water taxa and decrease of globorotalia inflata highlight colder surface water conditions and decreased atlantic mediterranean water exchange during glacials especially during the prominent sea level low stand of mis 12 short term prominent peaks of the polar subpolar neogloboquadrina pachyderma and coccolithus pelagicus ssp pelagicus and additional key taxa preferring fresher and turbid water together with minima in total nannofossil accumulation rate and enhanced coccolith reworking sustain a correlation with the north atlantic heinrich type ht events ht1 ht1a ht3 ht4 6 thus documenting the sensitiveness of the alboran sea in recording european and laurentide ice sheet dynamics the comparable chronology of most of these cold spells in the available balearic and ionian calcareous plankton records highlights that atlantic melt water entering alboran basin through gibraltar strait may have reached the central mediterranean preserving some of its original polar signature

interaction between antarctic sea ice and synoptic activity in the circumpolar trough implications for ice core interpretation interactions between antarctic sea ice and synoptic activity in the circumpolar trough have been investigated using meteorological data from european centre for medium range weather forecasts ecmwf interim re analysis and sea ice data from passive microwave measurements total antarctic sea ice extent does not show large interannual variations however large differences are observed on a regional monthly scale depending on prevailing winds and currents and thus on the prevailing synoptic situations the sea ice edge is also a preferred region for cyclogenesis due to the strong meridional temperature gradient high baroclinicity in that area the motivation for this study was to gain a better understanding of the interaction between sea ice extent and the general atmospheric flow particularly the frequency of warm air intrusions into the interior of the antarctic continent since this influences precipitation seasonality and must be taken into account for a correct climatic interpretation of ice cores two case studies of extraordinary sea ice concentration anomalies in relation to the prevailing atmospheric conditions are presented however both strong positive and negative anomalies can be related to warm biases in ice cores indicated by stable isotope ratios especially in connection with the negative phase of the southern annular mode

enhanced seasonality of precipitation in the mediterranean during the early part of the last interglacial the deposition of sapropels in the eastern mediterranean sea is thought to occur during intervals of intensified african monsoon and increased precipitation in the mediterranean borderlands speleothem and pollen records however reveal conflicting evidence for a mediterranean wide precipitation increase suggesting that seasonal changes in the hydrological regime may be important using a multiproxy record we present the first independent evidence for seasonality of precipitation during the early last interglacial ca 130 119 ka from the tenaghi philippon peatland in northeast greece during the early part of the interglacial mineralogical macrofossil and pollen records from the same core show a shift from mire to lacustrine conditions simultaneous with an expansion of sclerophyllous vegetation and the presence of acicular aragonite indicating the onset of highly evaporative summer conditions this indicates enhanced seasonality of precipitation and reconciles the apparent incongruity between mediterranean pollen and speleothem records it also provides evidence for significantly increased winter precipitation coeval with the deposition of sapropel s5 one of the most prominent sapropels of the pleistocene we suggest that in addition to the summer african monsoon component increased winter precipitation from the northern mediterranean borderlands may have contributed to maintaining reduced surface water salinities in the mediterranean sea over the entire year

late quaternary nannofossil indicators of climate change in two deep sea cores associated with the leeuwin current off western australia the stratigraphic variations in nannoflora observed in the two deep sea cores recovered from the offshore western australia revealed a sequence of paleoceanographic changes for the last 250 kyr the dominance of small placolith taxa in the upper photic flora indicates continuous mild upwelling for the isotope stages 7 5 in this region the most important controlling factor for the abundance variation of florisphaera profunda in this region is considered to be the lower photic temperature rather than the stability of water column or the water turbidity the significant reduction in the abundance of f profunda combined with the stable in the northern core rs96gc21 and reduced in the southern core rs9 150 abundance of the small taxa suggest an intensified upwelling for the penultimate glaciation the sharp increase in f profunda abundance indicates a weakening of upwelling at the last interglacial climax lic offshore western australia after isotope stage 5 the existence of upwelling is not clear except in stage 2 when it was not strong enough to produce blooms of emiliania huxleyi among the subordinate taxa calcidiscus leptoporus calciosolenia murrayi neosphaera coccolithomorpha and oolithotus fragilis provide meaningful paleoceanographic signals supporting the conclusions of previous studies a weakening or cessation of leeuwin current for the glacial periods the shift of dominance from small gephyrocapsa mostly g ericsonii to small reticulofenestra mostly r parvula can be an useful datum event offshore western australia the reduced diversity of nannoflora during the interglacial periods can be explained by a lessened competition within nannoplankton community caused by particularly favorable conditions for the opportunists such as e huxleyi f profunda and small placoliths the variations in nannofossil abundance suggests an increased aeolian flux at the stages 6 and 2 offshore north west cape as well as at stage 6 offshore southwestern australia

a climatological analysis of high precipitation events in dronning maud land antarctica and associated large scale atmospheric conditions the link between high precipitation in dronning maud land dml antarctica and the large scale atmospheric circulation is investigated using era interim data for 1979 2009 high precipitation events are analyzed at halvfarryggen situated in the coastal region of dml and at kohnen station located in its interior this study further includes a comprehensive comparison of high precipitation in era interim with precipitation data from the antarctic mesoscale prediction system amps and snow accumulation measurements from automatic weather stations awss with the limitations of such a comparison being discussed the era interim and amps precipitation data agree very well however the correspondence between high precipitation in era interim and high snow accumulation at the awss is relatively weak high precipitation events at both halvfarryggen and kohnen are typically associated with amplified upper level waves this large scale atmospheric flow pattern is preceded by the downstream development of a rossby wave train from the eastern south pacific several days before the precipitation event at the surface a cyclone located over the weddell sea is the main synoptic ingredient for high precipitation both at halvfarryggen and at kohnen a blocking anticyclone downstream is not a requirement for high precipitation per se but a larger share of blocking occurrences during the highest precipitation days in dml suggests that these blocks strengthen the vertically integrated water vapor transport ivt into dml a strong link between high precipitation and the ivt perpendicular to the local orography suggests that ivt could be used as a proxy for high precipitation in particular over dml s interior

recent snowfall anomalies in dronning maud land east antarctica in a historical and future climate perspective 1 enhanced snowfall on the east antarctic ice sheet is projected to significantly mitigate 21st century global sea level rise in recent years 2009 and 2011 regionally extreme snowfall anomalies in dronning maud land in the atlantic sector of east antarctica have been observed it has been unclear however whether these anomalies can be ascribed to natural decadal variability or whether they could signal the beginning of a long term increase of snowfall here we use output of a regional atmospheric climate model evaluated with available firn core records and gravimetry observations and show that such episodes had not been seen previously in the satellite climate data era 1979 comparisons with historical data that originate from firn cores one with records extending back to the 18th century confirm that accumulation anomalies of this scale have not occurred in the past 60 years although comparable anomalies are found further back in time we examined several regional climate model projections describing various warming scenarios into the 21st century anomalies with magnitudes similar to the recently observed ones were not present in the model output for the current climate but were found increasingly probable toward the end of the 21st century

review and new aspects concerning the formation of eastern mediterranean sapropels abstract in this paper it is proposed that the formation of eastern mediterranean sapropels occurred in an anti estuarine type of circulation which was to some degree weakened relative to the present in response to reduction of the eastern mediterranean excess of evaporation over freshwater input this reduction of excess evaporation would have been imposed by intensifications of 1 the indian ocean summer sw monsoon influencing the eastern mediterranean via increased nile discharge and 2 the system of mediterranean depressions an element of the westerly atlantic system causing increased precipitation and decreased evaporation both the indian ocean summer monsoon and the westerly atlantic system would be intensified in response to the occurrence of distinct minima in the cycle of precession it is demonstrated that reduced excess evaporation whether or not coinciding with global phases of deglaciation would lead to reduction of surface water salinities in the eastern mediterranean causing isolation of previously formed high salinity cooler deep water thus mixing was severely reduced possibly even restricted to eddy diffusion with only occasional convective events that because of the existing density gradient hardly ever would reach the deepest parts of the basin the consequently diminished oxygen advection down from a few hundred meters in the water column favoured preservation of the sinking organic matter this would however suffice only to enable the formation of sapropels with low organic carbon contents the high organic carbon contents observed in various sapropels are argued to reflect superimposed increases of export production the described scenario accounts for previously reported 1 increases of organic carbon content with increasing depth of deposition within individual sapropels and 2 asymmetrical sequences of sapropel deposition characterized by gradual build up and rather abrupt ending it is furthermore in agreement with 3 isotopic and faunal reconstructions of the history of exchange transports through both the strait of sicily and the strait of gibraltar and 4 faunal and floral reflections of the presence or absence of a distinct deep chlorophyll maximum with its associated increases in export production indicating the presence or absence of a shallow pycnocline within the euphotic layer moreover the described scenario 5 is in no way conflicting with the reports of sapropels in the western mediterranean and 6 seems to be endorsed by occasionally intercalated intervals suggestive of somewhat improved oxygenation amidst anoxic benthic desert levels a situation that has been observed in a few quaternary and pliocene sapropels

north atlantic intermediate to deep water circulation and chemical stratification during the past 1 myr benthic foraminiferal carbon isotope records from a suite of drill sites in the north atlantic are used to trace variations in the relative strengths of lower north atlantic deep water lnadw upper north atlantic deep water unadw and southern ocean water sow over the past 1 myr during glacial intervals significant increases in intermediate to deep 13c gradients commonly reaching 1 2 are consistent with changes in deep water circulation and associated chemical stratification bathymetric 13c gradients covary with benthic foraminiferal 18o and covary inversely with vostok co2 in agreement with chemical stratification as a driver of atmospheric co2 changes three deep circulation indices based on 13c show a phasing similar to north atlantic sea surface temperatures consistent with a northern hemisphere control of nadw sow variations however lags in the precession band indicate that factors other than deep water circulation control ice volume variations at least in this band

abrupt temperature changes in the western mediterranean over the past 250 000 years a continuous high resolution western mediterranean sea surface temperature sst alkenone record spanning the past 250 000 years shows that abrupt changes were more common at warming than at cooling during marine isotope stage mis 6 sst oscillated following a stadial interstadial pattern but at lower intensities and rates of change than in the dansgaard oeschger events of mis 3 some of the most prominent events occurred over miss 5 and 7 after prolonged warm periods of high stability climate during the whole period was predominantly maintained in interglacial interstadial conditions whereas the duration of stadials was much shorter

millennial scale coccolithophore paleoproductivity and surface water changes between 445 and 360 ka marine isotope stages 12 11 in the northeast atlantic abstract a high resolution coccolithophore study was carried out in order to improve the understanding of the paleoceanographic evolution and changes in paleoproductivity occurring off the iberian margin im between 445 and 360 ka i e during late marine isotope stage 12 to 11 coccolithophore assemblages allowed reconstructing surface water changes characterized by millennial scale oscillations 1 5 kyr cycles involving portugal or iberian poleward currents pc and ipc prevalence changes in paleoproductivity possibly related to the upwelling of eastern north atlantic central waters enacw of sub tropical enacwst or sub polar origin enacwsp were also recognized this study also permitted detecting abrupt events stadial interstadial type oscillations and revealed that changes in paleoproductivity are related to opposite dynamics during glacial and interglacial stages with the reversed setting being established during the deglaciation furthermore a possible control of half and fourth precessional cycle components on the occurrence of abrupt changes within the assemblages structure during the deglaciation is proposed on the basis of wavelet analysis results applied to selected taxa

perspicacious indicators of atmospheric blocking 1 a novel dynamically based approach is introduced to identify describe and diagnose atmospheric blocking events the approach is based upon the potential vorticity perspective and takes into account the three dimensional structure of the phenomenon it is argued that the essence of a blocking anomaly is located in the upper troposphere just below the tropopause the associated novel blocking indicators are derived from two dimensional fields at 6 hourly temporal resolution and provide information on the spatial scale shape amplitude and movement of blocks a northern hemisphere winter djf climatology for the era15 period 1979 1993 is presented and comments are made on the relationship between the indicators and previous blocking indices

a sustained 21 m sea level highstand during mis 11 400 ka direct fossil and sedimentary evidence from bermuda abstract a small protected karstic feature exposed in a limestone quarry in bermuda preserved abundant sedimentary and biogenic materials documenting a transgressive phase still stand and regressive phase of a sea level in excess of 21 3 m above present during marine isotope stage mis 11 400 ka as determined by u th dating and amino acid racemization cobbles and marine sediments deposited during the high energy transgressive phase exhibit rim cements indicating a subsequent phreatic environment this was succeeded stratigraphically by a still stand deposition of fine calcareous lagoonal sediments containing bioclasts of red algae and benthic and planktonic foraminifera that was intensely burrowed by marine invertebrates probably upogebiid shrimp that could not be produced under any condition other than sustained marine submergence overlying this were pure carbonate beach sands of a low energy regressive phase containing abundant remains of terrestrial and marine vertebrates and invertebrates the considerable diversity of this fauna along with taphonomic evidence from seabird remains indicates deposition by high run up waves over a minimum duration of months if not years the maximum duration has yet to be determined but probably did not exceed one or two thousand years the most abundant snails in this fauna are two species indicative of brackish water and high tide line showing that a ghyben herzberg lens must have existed at 20 m the nature of these sediments and fossil accumulation is incompatible with tsunami deposition and given the absence of evidence for tectonic uplift of the bermuda pedestal or platform provide proof that sea level during mis 11 exceeded 20 m a fact that has widespread ramifications for geologists biogeographers and human demographics along the world s coastlines

microplankton response to environmental conditions in the alboran sea western mediterranean one year sediment trap record abstract the present work analyses the seasonal evolution of planktonic assemblages and particle fluxes through the water column in the eastern alboran sea western mediterranean at 35o55 47 n 01o30 77 w a sediment trap was deployed below the influence of the almeria oran front aof a semi permanent geostrophic front during july 1997 to june 1998 overall the temporal variability of coccolithophore planktonic foraminifer diatom benthic and wind carried biogenic particle fluxes is linked to the seasonal evolution of sea surface hydrological structures maximum planktonic fluxes were found during high productivity periods and wind induced upwelling following a trimodal pattern with maximum fluxes in july 1997 november december 1997 and april may 1998 these periods were characterized by vertical mixing and the full development of anticyclonic gyres in the alboran sea the annual flux of coccolithophores was dominated by the small gephyrocapsa group and emiliania huxleyi whereas turborotalita quinqueloba and globigerina bulloides dominated the foraminiferal fluxes and chaetoceros resting spores rs were predominant in the diatom assemblage benthic specimens were also collected with the sediment trap suggesting a variable influence of bottom water activity wind driven particles phytoliths and fresh water diatoms were collected along the year but their fluxes followed the local wind regime the high sea surface temperature sst during fall due to weaker than usual westerly winds and the pressure anomaly prevailing in the alboran sea during early winter were reflected in the planktonic assemblages by the proliferation of warm lower photic layer inhabitants and or oligotrophic taxa of coccolithophores florisphaera profunda planktonic foraminifers globigerinoides ruber and globorotalia inflata and diatoms leptocylindrus danicus these unusual climatic conditions in the eastern alboran sea must have been caused by the 1997 1998 enso event

coccolithophores in the equatorial atlantic ocean response to seasonal and late quaternary surface water variability abstract the present study was initiated to ascertain the significance of coccolithophores as a proxy for paleoceanographic and paleoproductivity studies in the equatorial atlantic data from a range of different samples from the plankton surface sediments as well as sediment cores are shown and compared with each other in general the living coccolithophores in the surface and subsurface waters show considerable variation in cell numbers and distribution patterns cell densities reached a maximum of up to 300 103 coccospheres l in the upwelling area of the equatorial atlantic here emiliania huxleyi is the dominant species with relatively high cell numbers whereas umbellosphaera irregularis and umbellosphaera tenuis are characteristic for oligotrophic surface waters although they are observed in high relative abundances these species only occur in low absolute numbers the lower photic zone is dominated by high abundances and considerable cell numbers of florisphaera profunda the geographical distribution pattern of coccoliths in surface sediments reflects the conditions of the overlying surface water masses however abundances of the oligotrophic species umbellosphaera irregularis and umbellosphaera tenuis are strongly diminished causing an increase in relative abundance of the lower photic zone taxa florisphaera profunda and gladiolithus flabellatus during the past 140 000 years the surface water circulation of the equatorial atlantic has changed drastically as can be seen from changes in the coccolithophore species composition absolute coccolith numbers as well as coccolith accumulation rates significant increases in coccolith numbers and accumulation rates is observed in the southern equatorial atlantic during the last glacial interval oxygen isotope stages 2 4 which we attribute to enhanced upwelling intensities and advection of cool nutrient rich waters at this site in the western equatorial atlantic we observe an opposite trend with decreasing numbers of coccoliths during glacial periods which probably is caused by a deepening of the thermocline

focal mechanism of the 20 august 1983 caspian sea earthquake abstract the short period array seismogram at gba india of a central caspian sea seismic event on 20 august 1983 was described by some workers as explosion like though they finally favoured an earthquake source on focal depth and p wave complexity spectral criteria we subject gba and other array records to a quantitative test for compatibility with a double couple source the p pp sp relative amplitude method applied in conjunction with a moving depth window process to test separately a wide range of p pp sp times the only sections of coda consistent with being pp and or sp are large amplitude arrivals 12 15 s behind p they indicate a normal fault striking wnw ese and downthrown to the north at a depth of some 30 km in good agreement with the trend of mapped faults and local seismicity and focal depth derived from p onset times

snowfall driven mass change on the east antarctic ice sheet 1 an improved understanding of processes dominating the sensitive balance between mass loss primarily due to glacial discharge and mass gain through precipitation is essential for determining the future behavior of the antarctic ice sheet and its contribution to sea level rise while satellite observations of antarctica indicate that west antarctica experiences dramatic mass loss along the antarctic peninsula and pine island glacier east antarctica has remained comparably stable in this study we describe the causes and magnitude of recent extreme precipitation events along the east antarctic coast that led to significant regional mass accumulations that partially compensate for some of the recent global ice mass losses that contribute to global sea level rise the gain of almost 350 gt from 2009 to 2011 is equivalent to a decrease in global mean sea level at a rate of 0 32 mm yr over this three year period

a paleoecological and paleobiogeographic evaluation of helicosphaera inversa gartner theodoridis and the diachrony of its first occurrence abstract the distribution pattern of helicosphaera inversa gartner theodoridis is examined from a mid latitude north atlantic core md01 2446 and two mediterranean cores ocean drilling program odp site 975 and core kc01b through marine isotope stage mis 13 to 9 the earliest rare occurrences are observed from the uppermost part of mis 12 while common and continuous abundances characterize mis 11 the paleoenvironmental framework of the study cores suggests that the taxon thrived in warm surface waters correlation with new data from planktonic foraminifera also suggests that h inversa may have only flourished within a limited salinity range comparison with previous findings highlights major diachrony in the fo of the taxon between low and mid latitude records it first occurred at lower latitude in the pacific as early as 0 8 ma while in the mid latitude north atlantic regions it is not recorded before 0 51 ma the distribution of the taxon in the north atlantic ocean also apparently varies in relation with surface water masses and hydrographic fronts the results suggest that the fo of h inversa is ecologically controlled and needs to be used with caution in worldwide stratigraphic correlation nevertheless the distribution of the species within the mediterranean basin can produce an invaluable ecostratigraphical signal

abrupt climate events 500 000 to 340 000 years ago evidence from subpolar north atlantic sediments subpolar north atlantic proxy records document millennial scale climate variations 500 000 to 340 000 years ago the cycles have an approximately constant pacing that is similar to that documented for the last glacial cycle these findings suggest that such climate variations are inherent to the late pleistocene regardless of glacial state sea surface temperature during the warm peak of marine isotope stage 11 mis 11 varied by 0 5 to 1 c less than the 4 to 4 5 c estimated during times of ice growth and the 3 c estimated for glacial maxima coherent deep ocean circulation changes were associated with glacial oscillations in sea surface temperature

seasonality of airmass pathways to coastal antarctica ramifications for interpreting high resolution ice core records abstractunderstanding airmass pathways is critical for ice core interpretation and the ability to determine the broadscale characteristics and seasonality of synoptic scale flow using paleoclimate records offers great potential to improve the understanding of past atmospheric circulation the dominant airmass pathways to a coastal antarctic ice core site at the whitehall glacier in the ross sea are modeled using snowfall and high resolution stable isotope data between 1979 and 2006 combined with back trajectories produced from both ncep ncar and ecmwf interim re analysis era interim data back trajectories generated from both datasets produce comparable results they show that high snowfall is associated with cyclonic airflow in the ross sea with a strong meridional component along the western ross sea coast over a 28 yr time frame trajectories also reveal a clear distinction between flow paths associated with above and below average annual temperatures high and low d in the ice core record in

snow accumulation and its moisture origin over dome argus antarctica the spatial and temporal variability of snow accumulation near dome argus antarctica is assessed using new snow pit and stake measurement data together with existing snow pit ice core and automatic weather station records snow accumulation rate shows large inter annual variations but stable multi decadal levels over the last seven centuries spatial variations in snow accumulation within the space of 50 km of dome argus are relatively small probably thanks to the smooth topography a comparison of theses accumulation observations with ecmwf reanalyses era 40 and era interim suggests ecmwf reanalysis captures the seasonal variations but underestimates the overall snow accumulation at dome argus by 50 the moisture sources for precipitation over dome argus are examined by means of a lagrangian moisture source diagnostic based on the tracing of specific humidity changes along air parcel trajectories for the period 2000 2004 using operational ecmwf analysis data dome argus mainly receives moisture from the mid latitude 46 4 s south indian ocean with a seasonal latitudinal shift of about 6 compared to other central east antarctic deep ice core sites such as dome f dome c vostok and epica dronning maud land dome argus has a more southerly moisture origin probably due to topographic influences on the moisture transport paths these results have important implications for the interpretation of future ice cores at dome argus

revised tuning of ocean drilling program site 964 and kc01b mediterranean and implications for the δ18o tephra calcareous nannofossil and geomagnetic reversal chronologies of the past 1 1 myr 1 high resolution color reflectance records of kc01 and kc01b calabrian ridge ionian sea are presented and compared with a modified spliced high resolution color reflectance record of ocean drilling program odp site 964 this comparison revealed that kc01b is characterized by intensive deformation between 27 and 28 5 m piston depth and that some sapropels are tectonically reduced in thickness moreover the piston coring has caused considerable stretching in the top of kc01 and kc01b using a new splice of odp site 964 as guide previous astronomical tuned timescales of kc01b and odp site 964 were evaluated this evaluation resulted in a new sapropel based astronomical timescale for the last 1 1 myr the new timescale implies a much more uniform change in sedimentation rate for the ionian sea cores two prominent excursions to lighter values in the 18o record of the planktonic foraminiferal species globigerinoides ruber occur during marine isotopic stages 12 and 16 applying the new timescale these shifts correspond with maxima in obliquity and are punctuated by minima in the precession cycle they are absent in global ice volume records and are interpreted as reflecting a summer low salinity surface water lens that floats on top of extremely saline intermediate and deep waters at times of the very low sea levels during these glacial periods all biostratigraphic and magnetostratigraphic events found in kc01b and odp site 964 were re dated according to the new timescale and the ages of 33 tephra layers were reviewed the new ages for the calabrian ridge 2 and 3 magnetic events in the brunhes are concordant with minima in the global sint800 composite record derived from worldwide deep sea records of relative paleointensity and have been attributed to the big lost and la palma excursions respectively

a study of an intense density front in the eastern alboran sea the almeria oran front abstract studies of satellite imagery and space shuttle photographs of the western mediterranean have indicated that the main path of inflowing atlantic water is around two large anticyclonic gyres in the alboran sea and along the algerian coast these studies have also shown that a strong ocean front is present between almeria spain and oran algeria which is part of the easternmost segment of the eastern alboran gyre based on these satellite studies the first in situ investigation of the front called here the almeria oran front was conducted in march 1986 as part of the winter campaign of the western mediterranean circulation experiment wmce analyses of the resulting data show that the almeria oran front is a large scale density front formed by the convergence of two distinct water masses and controlled by the geographic position and strength of the eastern alboran gyre physical and biochemical data indicate that the front is limited to the upper 300 m with a strong southward baroclinic jet

foraminiferal faunal estimates of paleotemperature circumventing the no analog problem yields cool ice age tropics the sensitivity of the tropics to climate change particularly the amplitude of glacial to interglacial changes in sea surface temperature sst is one of the great controversies in paleoclimatology here we reassess faunal estimates of ice age ssts focusing on the problem of no analog planktonic foraminiferal assemblages in the equatorial oceans that confounds both classical transfer function and modern analog methods a new calibration strategy developed here which uses past variability of species to define robust faunal assemblages solves the no analog problem and reveals ice age cooling of 5 o to 6oc in the equatorial current systems of the atlantic and eastern pacific oceans classical transfer functions underestimated temperature changes in some areas of the tropical oceans because core top assemblages misrepresented the ice age faunal assemblages our finding is consistent with some geochemical estimates and model predictions of greater ice age cooling in the tropics than was inferred by climate long range investigation mapping and prediction climap 1981 and thus may help to resolve a long standing controversy our new foraminiferal transfer function suggests that such cooling was limited to the equatorial current systems however and supports climap s inference of stability of the subtropical gyre centers

detrital input productivity fluctuations and water mass circulation in the westernmost mediterranean sea since the last glacial maximum 1 by presenting sea surface temperatures planktonic oxygen isotope profiles and bulk geochemical composition of core sediments we offer a multiparameter reconstruction of western mediterranean oceanography from the last glacial maximum until the middle holocene 20 000 5000 cal years b p sediments from ocean drilling program site 975 in the algero balearic basin have been compared with three alboran basin cores ttr 300g ttr 302g and ttr 304g all of them investigated at high resolution this multiproxy approach has allowed two different modes of circulation to be recognized 1 during the lgm and from 8 0 cal ka b p onward no surface gradient in 18og bulloides is found associated with low productivity in close analogy to modern conditions 2 during the bolling allerod and early holocene significant surface isotopic gradients are found with periods probably indicating an unstable water column associated with enhanced productivity and low bottom oxygen conditions the close synchrony between the occurrence of the surface isotopic offset and organic rich layer formation implicates that the origin of these features is linked probably via shoaling of the regional thermohaline circulation paleo ssts derived from planktonic foraminifer assemblages indicate abrupt changes in surface conditions during the analyzed time interval fluctuations in marine productivity based on ba and total organic carbon are related to water column stability and atmospheric conditions a sharp warming and 18og bulloides excursion at the end of the younger dryas is probably linked to glacial meltwater influence the riverine input has been reconstructed using the mg al ratio and mg al peaks during arid periods greenland stadial 2a and younger dryas related to bypass margin processes

abrupt changes in meteorological conditions observed at an inland antarctic station in association with wintertime blocking time evolution of a prominent wintertime blocking event over east antarctica and the associated drastic changes in weather conditions observed at an inland station are documented a strong blocking ridge was formed at the leading edge of a quasi stationary rossby wavetrain where a wave activity flux emanating from the subtropics was convergent the ridge pumped up heat and moisture from lower latitudes into inland antarctica with a strong poleward flow along its upstream flank the station was situated under this flow just for two days during which the normal condition with cold and clear weather was markedly disturbed the flow climbing up the continental slope led to cloud formation above the inland station enhanced downward longwave radiation from the clouds and enhanced vertical mixing associated with the record setting wind speeds resulted in a sudden drastic increase in surface air temperature and the breakdown of the developed surface inversion layer

time and space variability in the eastern alboran sea from march to may 1990 an intensive field experiment was carried out from march 6 to april 30 1990 in the eastern alboran sea to understand the relationship between the large scale circulation and the location of the transition zone between new and longer resident modified atlantic water maw the detection of a strong jet 80 cm s 1 of new maw with anticyclonic curvature near the morocco coast suggests that the eastern alboran gyre eag was not fully developed a new state of the circulation in the eastern alboran basin intermediate between the eag viudez et al 1995 and the lanoix 1974 state is presented also important is that the almeria oran front was not present in the upper layer that small scale instabilities were detected in the northern region and that significant nongeostrophic flows were observed all these features are clearly indicative of the high spatial and temporal variability of a region where complex adjustments among density velocity and topography occur

the role of synoptic scale features and advection in prolonged warming and generation of different forms of precipitation at dome fuji station antarctica following a prominent blocking event 1 a blocking event over the east antarctic ice sheet during june 1997 generated the highest surface air temperature which increased from around 70 c to around 30 c and pressure of that year at the dome fuji station 77 5 s 40 e following the blocking event the anomalously high air temperature around 50 c to 60 c and pressure were maintained at the surface for about 1 week this study investigates how these warm conditions were maintained and documents the sequential occurrence of two forms of synoptic scale high pressure systems with conditions that produced precipitation by different processes in each case in the first half of the warm period a solitary high pressure system the solitary high formed over the dome fuji station and traveled west over east antarctica after being cut off from the tip of the preceding blocking ridge during this phase tropospheric temperatures were higher and surface based temperature inversions were more intense than during the following period while a dry out developed in the troposphere below about 300 hpa the precipitation of ice crystals in the surface based temperature inversion layer was generated by deposition of moisture that had become trapped in the boundary layer after being transported onto the continent by the previous blocking ridge this mechanism has not been previously reported elsewhere during the second half of the warm period a ridge of high pressure the transcontinental ridge traversed east antarctica almost completely and its western section was amplified by the merging of the solitary high with a preceding quasi stationary rossby wave train propagating along the southern ocean this ridge allowed an intrusion of warm moist air from the weddell sea toward the station which generated precipitation throughout the whole troposphere by orographic uplift once again and ended the dry out this represents the typical mechanism of both moisture transportation and the generation of precipitation and this mechanism was the same as that associated with the preceding blocking ridge