a planktic foraminiferal transfer function for the southern south atlantic ocean abstract quantitative analysis of planktic foraminiferal assemblages in 81 surface sediment samples from 20 s subtropical gyre to 55 s antarctic zone in the south atlantic ocean documents a close relationship between species distribution and austral summer surface water temperature a data set including the abundance pattern of 25 taxa and morphotypes was used to establish a transfer function based on the definition of five factors altogether these factors account for 97 of the total variance of the original data and their geographic distribution is closely linked to sea surface temperatures the transfer function f81 25 5 allows reconstruction of late quaternary summer surface water temperatures in the boundary region between the antarctic cold and subtropical warm water realm 0 5 to 26 0 c the statistical error for modern data is 1 3 c

modern distribution patterns of planktonic foraminifera in the south china sea and western pacific a new transfer technique to estimate regional sea surface temperatures abstract we present 30 new planktonic foraminiferal census data of surface sediment samples from the south china sea recovered between 630 and 2883 m water depth these new data together with the 131 earlier published data sets from the western pacific are used for calibrating the simmax 28 transfer function to estimate past sea surface temperatures this regional simmax method offers a slightly better understanding of the marginal sea conditions of the south china sea than the linear transfer function fp 12e which is based only on open ocean data however both methods are biased toward the tropical temperature regime because of the very limited data from temperate to subpolar regions the simmax formula was applied to sediment core 17940 from the northeastern south china sea with sedimentation rates of 20 80 cm ka results revealed nearly unchanged summer temperatures around 28 c for the last 30 ky while winter temperatures varied between 19 5 c in the last glacial maximum and 26 c during the holocene during termination 1a the winter estimates show a younger dryas cooling by 3 c subsequent to a temperature optimum of 24 c during the bolling allerod estimates of winter temperature differences between 0 and 100 m water depth document the seasonal variations in the thickness of the mixed layer and provide a new proxy for estimating past changes in the strength of the winter monsoon

size distribution of holocene planktic foraminifer assemblages biogeography ecology and adaptation the size of any organism is influenced by the surrounding ecological conditions in this study we investigate the effects of such factors on the size spectra of planktic foraminiferal assemblages from holocene surface sediments we analyzed assemblages from 69 holocene samples which cover the major physical and chemical gradients of the oceans on a global scale the range of sizes in assemblages triples from the poles to the tropics this general temperature related size increase is interrupted by smaller sizes at temperatures characteristic of the polar and subtropical fronts at 2 c and 17 c respectively as well as in upwelling areas on a regional scale surface water stratification seasonality and primary productivity are highly correlated with the size patterns such environmentally controlled size changes are not only characteristic for entire assemblage but also for the dominant single species

the linkage between the eastern pacific teleconnection pattern and convective heating over the tropical western pacific abstractthe eastern pacific ep pattern is a recently detected atmospheric teleconnection pattern that frequently occurs during late winter through analysis of daily era interim data and outgoing longwave radiation data for the period of 1979 2011 it is shown here that the formation of the ep is preceded by an anomalous tropical convection dipole with one extremum located over the eastern indian ocean maritime continent and the other over the central pacific this is followed by the excitation of two quasi stationary rossby wave trains departing from the subtropics north of the region of anomalous convection one rossby wave train propagates eastward along the east asian jet from southern china toward the eastern pacific the second wave train propagates northward from east of japan toward eastern siberia and then turns southeastward to the gulf of alaska both wave trains are associated with wave activity flux convergence where the ep pattern develops the results from an examination of the e vecto

patterns of deglacial warming in the pacific ocean a review with emphasis on the time interval of heinrich event 1 abstract based on a compilation of currently available records of past sea surface temperature sst variability estimated from a variety of different proxies the regional scale deglacial sst development in the pacific ocean is tentatively classified into four endmember types the subtropical and tropical pacific is characterized by a continuous deglacial warming without marked interruption during the time interval of heinrich event 1 h1 whereas the subarctic north pacific exhibits centennial scale warm cold oscillations during this time interval sst records from marginal seas of the pacific show a deglacial warming interrupted by a cooling event coeval with h1 followed by a marked bolling sst increase a single sst record from the southwestern subantarctic pacific displays a continuous deglacial warming across h1 followed by an antarctic cold reversal type cooling during the allerod thus in contrast to the deglacial sst development in the atlantic which has been inferred to be overwhelmingly driven by the redistribution of heat through changes in the meridional overturning circulation moc none of the open oceanic pacific sst records reviewed here displays any obvious and or dominant response to the reduction of the moc and or the reorganization of atmospheric circulation during h1 within the limits of absolute chronologies all tropical and subtropical pacific sst records show an onset of deglacial warming at 19 1 ka coeval with the onset of the deglacial rise in sea level

palaeoceanographic implications of genetic variation in living north atlantic neogloboquadrina pachyderma the shells of the planktonic foraminifer neogloboquadrina pachyderma have become a classical tool for reconstructing glacial interglacial climate conditions in the north atlantic ocean1 2 3 palaeoceanographers utilize its left and right coiling variants which exhibit a distinctive reciprocal temperature and water mass related shift in faunal abundance both at present and in late quaternary sediments1 2 4 5 recently discovered cryptic genetic diversity in planktonic foraminifers6 7 8 now poses significant questions for these studies here we report genetic evidence demonstrating that the apparent single species shell based records of right coiling n pachyderma used in palaeoceanographic reconstructions contain an alternation in species as environmental factors change this is reflected in a species dependent incremental shift in right coiling n pachyderma shell calcite 18o between the last glacial maximum and full holocene conditions guided by the percentage dextral coiling ratio our findings enhance the use of 18o records of right coiling n pachyderma for future study they also highlight the need to genetically investigate other important morphospecies to refine their accuracy and reliability as palaeoceanographic proxies

tropical climates at the last glacial maximum a new synthesis of terrestrial palaeoclimate data i vegetation lake levels and geochemistry palaeodata in synthesis form are needed as benchmarks for the palaeoclimate modelling intercomparison project pmip advances since the last synthesis of terrestrial palaeodata from the last glacial maximum lgm call for a new evaluation especially of data from the tropics here pollen plant macrofossil lake level noble gas from groundwater and delta 18 o from speleothems data are compiled for 18 2 ka c 14 32 degrees n 33 degrees s the reliability of the data was evaluated using explicit criteria and some types of data were re analysed using consistent methods in order to derive a set of mutually consistent palaeoclimate estimates of mean temperature of the coldest month mtco mean annual temperature mat plant available moisture pam and runoff p e cold month temperature mat anomalies from plant data range from 1 to 2 k near sea level in indonesia and the s pacific through 6 to 8 k at many high elevation sites to 8 to 15k in s china and the se usa mat anomalies from groundwater or speleothems seem more uniform 4 to 6 k but the data are as yet sparse a clear divergence between mat and cold month estimates from the same region is seen only in the se usa where cold air advection is expected to have enhanced cooling in winter regression of all cold month anomalies against site elevation yielded an estimated average cooling of 2 5 to 3 k at modern sea level increasing to approximate to 6 k by 3000m how ever neotropical sites showed larger than the average sea level cooling 5 to 6 k and a non significant elevation effect whereas w and s pacific sites showed much less sea level cooling 1 k and a stronger elevation effect these findings support the inference that tropical sea surface temperatures ssts were lower than the climap estimates but they limit the plausible average tropical sea surface cooling and they support the existence of climap like geographic patterns in sst anomalies trends of pam and lake levels indicate wet lgm conditions in the w usa and at the highest elevations with generally dry conditions elsewhere these results suggest a colder than present ocean surface producing a weaker hydrological cycle more arid continents and arguably steeper than present terrestrial lapse rates such linkages are supported by recent observations on freezing level height and tropical ssts moreover simulations of greenhouse and lgm climates point to several possible feedback processes by which low level temperature anomalies might be amplified aloft

improving past sea surface temperature estimates based on planktonic fossil faunas a new method of past sea surface temperature sst reconstruction based on the modern analog technique prell 1985 and on the indirect approach bartlein et al 1986 has been developed the revised analog method ram applied to planktonic foraminifera this technique leads to significant improvements in modern sst reconstruction with respect to former methods our estimates are characterized by much lower residuals and a better coverage of the observed sst range moreover the error of ram estimates of past ssts is lower than that associated with former reconstructions particularly at middle and high latitudes in low latitudes cold season ssts reconstructed by ram during glacials are 1 3 c lower than previously estimated our results tend thus to reconcile paleoestimates of glacial temperatures based on planktonic microfossils and on continental data in the tropics

reconstruction of sea surface conditions at middle to high latitudes of the northern hemisphere during the last glacial maximum lgm based on dinoflagellate cyst assemblages abstract a new calibration database of census counts of organic walled dinoflagellate cyst dinocyst assemblages has been developed from the analyses of surface sediment samples collected at middle to high latitudes of the northern hemisphere after standardisation of taxonomy and laboratory procedures the database comprises 940 reference data points from the north atlantic arctic and north pacific oceans and their adjacent seas including the mediterranean sea as well as epicontinental environments such as the estuary and gulf of st lawrence the bering sea and the hudson bay the relative abundance of taxa was analysed to describe the distribution of assemblages the best analogue technique was used for the reconstruction of last glacial maximum lgm sea surface temperature and salinity during summer and winter in addition to sea ice cover extent at sites from the north atlantic n 63 mediterranean sea n 1 and eastern north pacific n 1 three of the north atlantic cores from the continental margin of eastern canada revealed a barren lgm interval probably because of quasi permanent sea ice six other cores from the greenland and norwegian seas were excluded from the compilation because of too sparse assemblages and poor analogue situation at the remaining sites n 54 relatively close modern analogues were found for most lgm samples which allowed reconstructions the new lgm results are consistent with previous reconstructions based on dinocyst data which show much cooler conditions than at present along the continental margins of canada and europe but sharp gradients of increasing temperature offshore the results also suggest low salinity and larger than present contrasts in seasonal temperatures with colder winters and more extensive sea ice cover whereas relatively warm conditions may have prevailed offshore in summer from these data we hypothesise low thermal inertia in a shallow and low density surface water layer

multiproxy approach for the reconstruction of the glacial ocean surface margo michal kucera antoni rosell mele ralph schneider claire waelbroeck mara weinelt department of geology royal holloway university of london egham tw20 0ex uk icrea and institute of environmental science and technology universitat autonoma de barcelona 08193 bellaterra catalonia spain departement de geologie et oceanographie umr5805 epoc cnrs universite de bordeaux1 33405 talence cedex france laboratoire des sciences du climat et de l environnement laboratoire mixte cnrs cea f 91198 gif sur yvette france institute for geosciences university of kiel olshausen strasse 40 d 24098 kiel germany

variability of the path of the kuroshio ocean current over the past 25 000 years the kuroshio current is the strong northwestern component of the subtropical north pacific ocean gyre and advects a large amount of heat from the tropics to northern mid latitudes the kuroshio has bimodal stationary flow patterns with small and large meander paths east of central japan1 2 which switch on annual and decadal timescales3 4 these switches seem to be caused by changes in current velocity and volume transport of the north equatorial current that are associated with variations in the trade wind intensity in the eastern equatorial north pacific ocean5 6 here we present alkenone derived sea surface temperature records at multicentennial resolution from sediment cores from the nishishichitou ridge off central japan these 25 000 year records show that the kuroshio path has also fluctuated on millennial timescales this variability resembles that of the subtropical high pressure of the north pacific reconstructed from terrestrial pollen distributions water levels in north american lakes and marine micropalaeontological records7 together these data indicate that climate variability off central japan over the past 25 000 years may be part of a circum pacific phenomenon reflecting the rate of subtropical surface circulation in the north pacific ocean

an anomalous late season change in the regional sea ice regime in the vicinity of the mertz glacier polynya east antarctica 1 this paper examines a major late season shift in atmospheric circulation over the east antarctic sea ice zone that occurred in october 1999 the mean wind direction at 65 s 145 e changed from south southeasterly to west southwesterly resulting in almost a complete reversal of the climatological east wind drift pattern in large scale sea ice advection over the southern ocean sector 135 170 e by comparison with national centers for environmental prediction national center for atmospheric research reanalysis time series from 1980 to 2000 this shift is shown to be unusual in terms of both its persistence and impact although similar though less prolonged patterns occurred in 1984 and 1985 lasting from october 1999 to february 2000 it had a profound impact on sea ice concentration and extent over a vast area by coinciding with the period of maximum ice extent and persisting through to the springtime melt phase it also contributed to the rapid annual meltback of sea ice it also had a large and complex effect on the behavior of the globally important mertz glacier polynya and on the areal extent of thick perennial sea ice to the east while a midlatitude blocking high pattern provided the initial impetus for the shift in 1999 the persistence of west southwesterly winds through february 2000 appears to relate to an unusually persistent southward migration of the antarctic circumpolar trough act in addition to the prolonged 1999 episode a strong seasonal signal is apparent throughout the mean wind speed and direction time series related to the act migration although less persistent than in 1999 this annual shift has implications for the observed dramatic annual meltback of east antarctic sea ice

climate connections between the hemisphere revealed by deep sea sediment core ice core correlations abstract correlation of southern ocean deep sea sediment core records with ice core records of polar climate delineates with unprecedented detail the relationship between high latitude climate and the ocean s thermohaline circulation over the last 80 000 years our observations suggest that while north atlantic deep water variability manifests itself clearly in southern ocean nutrient proxy records over periods as short as 500 yr this deep water variability did not promote a direct link between climate variability in the high latitudes of the two hemispheres on millennial timescales in particular the proxy records indicate that on average northern hemisphere climate fluctuations lagged those of the southern hemisphere by 1500 yr

sea surface temperatures around the australian margin and indian ocean during the last glacial maximum abstract we present new last glacial maximum lgm sea surface temperature sst maps for the oceans around australia based on planktonic foraminifera assemblages to provide the most reliable sst estimates we use the modern analog technique the revised analog method and artificial neural networks in conjunction with an expanded modern core top database all three methods produce similar quality predictions and the root mean squared error of the consensus prediction the average of the three under cross validation is only 0 77 c we determine lgm sst using data from 165 cores most of which have good age control from oxygen isotope stratigraphy and radiocarbon dates the coldest sst occurred at 20 500 1400 cal yr bp predating the maximum in oxygen isotope records at 18 200 1500 cal yr bp during the lgm interval we observe cooling within the tropics of up to 4 c in the eastern indian ocean and mostly between 0 and 3 c elsewhere along the equator the high latitudes cooled by the greatest degree a maximum of 7 9 c in the southwest pacific ocean our maps improve substantially on previous attempts by making higher quality temperature estimates using more cores and improving age control

constraints on sst estimates for the northern north atlantic nordic seas during the lgm abstract a map of estimated calcification temperatures of the planktic foraminifer neogloboquadrina pachyderma sinistral tnps for the nordic seas and the northern north atlantic for the last glacial maximum was produced from oxygen isotopes with support of mg ca ratios to arrive at the reconstruction several constraints concerning the plausible salinity and 18 o fields were employed the reconstruction indicates inflow of temperate waters in a wedge along the eastern border of the nordic seas and at least seasonally ice free waters the reconstruction from oxygen isotopes shows similarities with mg ca based paleotemperatures in the southern and southeastern sector while unrealistically high mg ca values in the central nordic seas prevent the application of the method in this area the oxygen isotope based reconstruction shows some agreement with temperature reconstructions based on the modern analogue technique but with somewhat lower temperatures and a stronger internal gradient inside the nordic seas all told our results suggest a much more ice free and dynamic high latitude ocean than the climap reconstruction

past extent of sea ice in the northern north atlantic inferred from foraminiferal paleotemperature estimates 1 using 150 core top samples we developed a conservative but fairly robust new measure to reconstruct past changes in maximum seasonal sea ice distribution in the northern north atlantic hitherto a major unknown the proxy is based on similarity maximum modern analog technique simmax estimates of threshold temperatures near the sea surface sst today almost 100 of all sites with sst 2 5 c during summer 0 4 for winters 1978 1987 and 0 75 c for little ice age winters lie seaward of the sea ice margin when applied to 60 sediment records of the last glacial maximum this proxy shows that peak glacial sea ice was far more restricted than in the classic climap project members 1981 reconstruction during glacial summer sea ice only covered the arctic ocean and western fram strait the northern north atlantic and nordic seas were largely ice free and thus formed a high latitude moisture source for the continued buildup of continental ice sheets in contrast sea ice spread far south across the iceland faeroe ridge during glacial winter with an inferred patch of sea ice also in the central east atlantic near the center of the azores high a broad ice free channel extended from 50 to 60 n forming an ideal site for large scale convection of glacial upper north atlantic deep water the extreme seasonality in glacial sea ice formation and melt in the nordic seas implies a major consumption of the regional energy income

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

global calibration of gephyrocapsa coccolith abundance in holocene sediments for paleotemperature assessment 1 a global sea surface temperature calibration based on the relative abundance of different morphotypes within the coccolithophore genus gephyrocapsa in holocene deep sea sediments is presented there is evidence suggesting that absolute sea surface temperature for a given location can be calculated from the relative abundance of gephyrocapsa morphotypes in sediment samples with a standard error comparable to temperature estimates derived from other temperature proxies such as planktic foraminifera transfer functions a total of 110 holocene sediment samples were selected from the pacific indian and atlantic oceans covering a mean sea surface temperature gradient from 13 6 to 29 3 c standard multiple linear regression analyses were applied to this data set linking the relative abundance of gephyrocapsa morphotypes to sea surface temperature the best model revealed an r2 of 0 83 with a standard residual error of 1 78 c for the estimation of mean sea surface temperature this new proxy provides a unique opportunity for the reconstruction of paleotemperatures with a very small amount of sample material due to the minute size of coccoliths permitting examination of thinly laminated sediments e g a pinhead of material from laminated sediments for the reconstruction of annual sea surface temperature variations such fine scale resolution is currently not possible with any other proxy application of this new paleotemperature proxy may allow new paleoenvironmental interpretations in the late quaternary period and discrepancies between the different currently used paleotemperature proxies might be resolved

application of artificial neural networks to paleoceanographic data abstract artificial neural networks are computer systems that have the ability to learn a set of output or target vectors from a set of input vectors learning is achieved by self adjustment of a set of parameters to minimize the error between a desired output and the actual network output we have explored the potential of this approach in paleoceanography by application of a neural network algorithm to a problem involving prediction of sea surface water temperatures from relative abundances of planktonic foraminifer species in the southern indian ocean we employed a backpropagation bp network to assess how well it was able to predict the actual summer and winter surface water temperatures we compared the results with those obtained from statistical methods previously used for temperature predictions imbrie kipp transfer functions the modern analog technique and soft independent modelling of class analogy the efficiency of predictions was tested using the leaving one out technique in which each of the observations in the data set is left out one at a time while the remaining observations are used to generate a predictor the accuracy of the predictor is then tested on the observation left out by comparison with its actual value a set of tests using 1 2 3 4 5 and 10 neurons processing elements in a 3 layer bp network showed that a network with 3 neurons gave the smallest errors of prediction for both summer and winter temperatures 0 71 and 0 76 respectively corresponding errors for the statistical pattern recognition techniques ranged between 1 01 and 1 26 for summer temperatures and 1 05 1 13 for winter temperatures hence predictions of paleotemperatures from new data on planktonic foraminifer relative abundances in the southern indian ocean may be made with a precision of 0 7 0 8 c using the bp network and 1 0 1 3 c using the statistical pattern recognition procedures the bp network was thus the most successful among the methods employed here for temperature predictions artificial neural networks may therefore be seen as a viable alternative to more conventional approaches to data analysis in paleoceanography

response of planktic foraminiferal size to late quaternary climate change 1 geographical size distribution within entire holocene foraminiferal assemblages is related to global environmental gradients such as temperature primary productivity and environmental variability this study demonstrates that these correlations are also recognizable in late quaternary assemblages from three locations in the south atlantic on temporal and latitudinal scales the size response to temporal paleoenvironmental changes during glacial interglacial cycles mimics the geographic holocene size variability the amplitude of size variability is directly related to the amplitude of the climatic fluctuations as shown by the stable size temperature relationship over time the documented changes in the assemblage size are caused by species replacement and intraspecific size variability the relative importance of these processes depends on the environmental setting species have been shown to reach their maximum size and abundance under certain optimum conditions and decrease in size if environmental conditions differ from these optima we confirm that late quaternary species sizes were largest at paleotemperatures identical to holocene ones

variability of north atlantic heat transfer during mis 2 1 short term changes in sea surface conditions controlling the thermohaline circulation in the northern north atlantic are expected to be especially efficient in perturbing global climate stability here we assess past variability of sea surface temperature sst in the northeast atlantic and norwegian sea during marine isotope stage mis 2 and in particular during the last glacial maximum lgm five high resolution sst records were established on a meridional transect 53 n 72 n to trace centennial scale oscillations in sst and sea ice cover we used three independent computational techniques simmax modern analogue technique artificial neural networks ann and revised analog method ram to reconstruct sst from planktonic foraminifer census counts simmax and ann reproduced short term sst oscillations of similar magnitude and absolute levels while ram owing to a restrictive analog selection appears less suitable for reconstructing cold end sst the simmax and ann sst reconstructions support the existence of a weak paleo norwegian current during dansgaard oeschger do interstadials number 4 3 2 and 1 during the lgm two warm incursions of 7 c water to occurred in the northern north atlantic but ended north of the iceland faroe ridge a rough numerical estimate shows that the near surface poleward heat transfer from 53 across the iceland faroe ridge up to to 72 n dropped to less than 60 of the modern value during do interstadials and to almost zero during do stadials summer sea ice was generally confined to the area north of 70 n and only rarely expanded southward along the margins of continental ice sheets internal lgm variability of north atlantic 40 n sst in the glamap 2000 compilation sarnthein et al 2003b pflaumann et al 2003 indicates maximum instability in the glacial subpolar gyre and at the iberian margin while in the nordic seas sst was continuously low

sea surface temperature anomalies in the oceans at the lgm estimated from the alkenone u37k index comparison with gcms 1 u k 37 sea surface temperature sst estimates for the last glacial maximum lgm are discussed and compared to coupled general circulation model gcm results we conclude that u k 37 estimates and most numerical models agree in the magnitude of the large scale sst cooling features of the glacial ocean there was a larger cooling in the northern than in the southern hemisphere the eastern boundary currents and equatorial regions were also colder there is a consensus between models and alkenone data for a tropical cooling of about 2 c which is in disagreement with both a smaller cooling as suggested by the climap project reconstruction or a more pronounced cooling as suggested from coral proxy records the comprehensive hadcm3 simulation examined reproduces a puzzling feature of the u k 37 sst reconstruction i e the warming of the glacial north atlantic which needs further investigation using numerical modelling and proxy data reconstruction

cool surface waters of the subtropical north pacific ocean during the last glacial one of the most controversial results of the climap12 project s reconstruction of past sea surface temperature sst is that large areas of the subtropical pacific ocean were warmer during the last glacial period than they are today this finding has important implications because sst patterns at low to subtropical latitudes strongly influence climate and sst changes are closely linked with climate fluctuations3 4 5 until now a lack of well preserved high resolution marine sediment cores from the region has hindered efforts to confirm these unexpectedly high ice age sst estimates here we use both the oxygen isotope compositions and species assemblages of planktonic foraminifera in a shallow water core with high deposition rates near hawaii to estimate glacial sst of the subtropical north pacific ocean contrary to the climap results2 our data indicate that the annual average sst in this region was 2 c cooler during the last glaciation than it is today these results help to reconcile the marine sst record with inferences drawn from snowline depressions on hawaii during the last glacial3 6 and should ultimately yield improved estimates of global climate sensitivity by providing important new constraints on climate model simulations of ice age cycles

climate impact of late quaternary equatorial pacific sea surface temperature variations magnesium calcium data from planktonic foraminifera in equatorial pacific sediment cores demonstrate that tropical pacific sea surface temperatures ssts were 2 8 0 7 c colder than the present at the last glacial maximum glacial interglacial temperature differences as great as 5 c are observed over the last 450 thousand years changes in sst coincide with changes in antarctic air temperature and precede changes in continental ice volume by about 3 thousand years suggesting that tropical cooling played a major role in driving ice age climate comparison of sst estimates from eastern and western sites indicates that the equatorial pacific zonal sst gradient was similar or somewhat larger during glacial episodes extraction of a salinity proxy from the magnesium calcium and oxygen isotope data indicates that transport of water vapor into the western pacific was enhanced during glacial episodes

the amplitude and phasing of climate change during the last deglaciation in the sulu sea western equatorial pacific 1 variations in tropical sea surface temperature patterns and the phasing relative to climate change in higher latitudes provide insight into the mechanisms of climate change on both orbital and shorter time scales here we present well dated high resolution records of planktonic foraminiferal 18o and mg ca based sst spanning the last deglaciation from the sulu sea located in the western equatorial pacific the results indicate that the last glacial maximum was 2 3 0 5 c cooler than present in the sulu sea with a concomitant decrease in sea surface salinity the similarity between variations in surface salinity in the sulu sea the western and eastern equatorial pacific and the greenland ice core record suggests that the observed changes in salinity reflect large scale rearrangement of atmospheric patterns which were coherent and synchronous throughout the northern hemisphere the results suggest that the glacial equatorial pacific climate was strongly influenced by both tropical and extra tropical forcing although it is not clear whether interannual enso variability is a good analogue of glacial interglacial climate change

a 370 ka paleoceanographic record from the hess rise central north pacific ocean and an indistinct kuroshio extension abstract a 5 m long core np36 collected from the hess rise in the central north pacific ocean 34 11 7 n 179 15 4 e water depth 2664 m was analyzed for benthic and planktonic foraminifera this core yields a continuous record for the last ca 370 000 years according to the oxygen isotope stratigraphy cross spectral analysis of down core variations in planktonic 18o values correlates well with the specmap reference scale allowing recognition of marine isotope stages mis down to mis 10 and the 18o variations coincide well with the changes in sea surface temperature derived using the modern analogue technique time series analyses of mass accumulation rates mar of planktonic and benthic foraminifera were also performed along with analysis of variations in faunal composition mar of planktonic foraminifera display maxima during glacial periods which together with coincident changes in lightness l of sediment measured with the spectrophotometer strongly suggests increasing flux of eolian dust to the hess rise due to strengthened westerly winds however mar of benthic foraminifera including epistominella exigua a common typical phytodetritus feeder also display highest increases during some interglacial periods i e mis 5 and 7 the benthic mar maxima are thought to reflect variations in consumption patterns between benthic and planktonic species a proposed hypothesis that vigorous grazing of phytoplanktons occurred during glacial periods reducing the flux of phytodetritus to the sea floor in turn impacting and limiting production of benthic foraminifera with the opposite effect prevailing during interglacial periods down core variations in right coiling neogloboquadrina pachyderma abundance and the composition of planktonic foraminiferal faunas indicate the subarctic front did not shift southward over the study site during the past 370 000 years alternatively variations in faunal composition indicate that subtropical water prevailed in the study area throughout this period no clear faunal evidence of the presence of the kuroshio extension was found in core np36 reflecting the loss of heat and tropical faunal elements from this water mass as it flowed eastward during late quaternary climatic maxima and minima

sea surface temperatures in the equatorial and south atlantic ocean during the last glacial maximum 23 19 ka 1 we used planktic foraminiferal assemblages in 70 sediment cores from the tropical and subtropical south atlantic ocean 10 n 37 s to estimate annual mean sea surface temperatures ssts and seasonality for the last glacial maximum with a modified version of the imbrie kipp transfer function method iktf that takes into account the abundance of rare but temperature sensitive species in contrast to climap project members 1981 the reconstructed ssts indicate cooler glacial ssts in the entire tropical subtropical south atlantic with strongest cooling in the upwelling region off namibia 7 10 c and smallest cooling 1 2 c in the western subtropical gyre in the western atlantic our data support recent temperature estimates from other proxies in the upwelling regions in the eastern atlantic our data conflict with sst reconstructions from alkenones which may be due to an environmental preference of the alkenone producing algae or to an underestimation of foraminiferal ssts due to anomalous high abundances of n pachyderma sinistral

testing the effects of tropical temperature productivity and mixed layer depth on foraminiferal transfer functions statistical transfer functions relate living planktonic foraminiferal species of the central equatorial pacific to measured sea surface temperature integrated primary productivity and mixed layer depth the faunal estimates successfully reconstruct latitudinal patterns observed in both warm el nino february march 1992 and cool la nina august september 1992 seasonal settings predictions of mixed layer depth appear to be unbiased by temperature or productivity in our data set but tend to underestimate deep mixed layers interactions between productivity and temperature perhaps through their common influence on respiration and growth rates bias foraminiferal transfer functions for both properties paleoceanographic estimates may be improved by accounting for such biological processes that translate the environment into a faunal response preserved in the geologic record

reconstruction of sea surface temperatures from assemblages of planktonic foraminifera multi technique approach based on geographically constrained calibration data sets and its application to glacial atlantic and pacific oceans abstract we present a conceptual framework for a new approach to environmental calibration of planktonic foraminifer census counts this approach is based on simultaneous application of a variety of transfer function techniques which are trained on geographically constrained calibration data sets it serves to minimise bias associated with the presence of cryptic species of planktonic foraminifera and provides an objective tool for assessing reliability of environmental estimates in fossil samples allowing identification of adverse effects of no analog faunas and technique specific bias we have compiled new calibration data sets for the north n 862 and south n 321 atlantic and the pacific ocean n 1111 we show evidence that these data sets offer adequate coverage of the sea surface temperature sst and faunal variation range and that they are not affected by the presence of pre holocene samples and or calcite dissolution we have applied four transfer function techniques including artificial neural networks revised analog method and simmax with and without distance weighting on faunal counts in a last glacial maximum lgm data set for the atlantic ocean 748 samples in 167 cores based on the glamap 2000 compilation and a new data set for the pacific ocean 265 samples in 82 cores and show that three of these techniques provide adequate degree of independence for the advantage of a multi technique approach to be realised the application of our new approach to the glacial pacific lends support to the contraction and perhaps even a cooling of the western pacific warm pool and a substantial 3 c cooling of the eastern equatorial pacific and the eastern boundary currents our results do not provide conclusive evidence for lgm warming anywhere in the pacific the atlantic reconstruction shows a number of robust patterns including substantial cooling of eastern boundary currents with considerable advection of subpolar waters into the benguela current a cooling of the equatorial atlantic by 5 c and steep sst gradients in the mid latitude north atlantic the transfer function techniques generally agree that subtropical gyre areas in both hemispheres did not change significantly since the lgm although the ann technique produced glacial sst in the southern gyre 1 2 c warmer than today we have revisited the issue of sea ice occurrence in the nordic seas and using the distribution of subpolar species of planktonic foraminifera in glacial samples we conclude that the norwegian sea must have been ice free during the summer

el nino like pattern in ice age tropical pacific sea surface temperature sea surface temperatures ssts in the cold tongue of the eastern equatorial pacific exert powerful controls on global atmospheric circulation patterns we examined climate variability in this region from the last glacial maximum lgm to the present using a sst record reconstructed from magnesium calcium ratios in foraminifera from sea floor sediments near the galapagos islands cold tongue sst varied coherently with precession induced changes in seasonality during the past 30 000 years observed lgm cooling of just 1 2 c implies a relaxation of tropical temperature gradients weakened hadley and walker circulation southward shift of the intertropical convergence zone and a persistent el nino like pattern in the tropical pacific this is contrasted with mid holocene cooling suggestive of a la nina like pattern with enhanced sst gradients and strengthened trade winds our results support a potent role for altered tropical pacific sst gradients in global climate variations

oceanic surface conditions recorded on the sea floor of the southwest pacific ocean through the distribution of foraminifers and biogenic silica over 180 surface sediment samples from the southwest pacific ocean were investigated for their planktonic foraminiferal 149 m opaline and terrigenous sediment content with the aim to determine the oceanic conditions at the sea surface above the sampling sites high concentrations of biogenic opal are related to high productivity levels recognised in tropical surface waters the abundance of this biogenic opal found within the sediments on the ocean floor shows a slight decrease as one approaches the australian landmass and also poleward from the equatorial belt the distribution of major species of planktonic formainifers reflects different surface water masses q mode factor analysis of planktonic foraminiferal percentage data from 63 core tops permits identification of several characteristic formainiferal assemblages for the southwest pacific ocean four factors explain up to 95 5 of the total variance factor 1 66 is dominated by the tropical subtropical species globigerinoides sacculifer and globigerinoides ruber the transitional to subpolar species globorotalia inflata is important in factor 2 12 the temperate cool factor 3 13 is characterised by turborotalia quinqueloba and globigerinita glutinata factor 4 which explains 3 of the total variance and which is represented by several species is assigned to the high productive equatorial and coastal waters off the australian continental margin palaeoecological equations permitting an estimate of sea surface temperatures and salinities are presented the correlation coefficients between modern data adapted from literature and estimated by transfer function fp 4 transfer function for planktonic formainifers are 0 95 for temperature and 0 77 for salinity

glacial sea surface temperatures in the subtropical north pacific a comparison of u37 k δ18o and foraminiferal assemblage temperature estimates we have investigated glacial interglacial differences in sea surface temperature sst near hawaii using two relatively high deposition rate shallow water piston cores collected near oahu hawaii modern hydrographic data show that local surface water temperatures are broadly consistent with the regional pattern of ssts in the southern subtropical north pacific past ssts were estimated on the basis of three independently measured parameters 1 u37k values of alkenones 2 18o of globigerinoides ruber and 3 assemblages of planktonic foraminifera using the modern analog technique mat the two cores yield similar sst records and if differences in the ecology of foraminifera and coccolithophores are considered the three different approaches to estimating ssts yield consistent results u37k based temperatures which may represent winter values at this location were 2 5 c colder during the last glacial maximum than today which is consistent with the february mat estimates the 18o based temperature estimates likely biased toward summer temperatures indicate that the glacial ssts were at least 1 c cooler than today which is comparable to the results of mat august estimates

simulated influence of carbon dioxide orbital forcing and ice sheets on the climate of the last glacial maximum a coupled atmosphere ocean sea ice model is used to investigate the climate of the last glacial maximum 21 000 years ago and the relative climate forcing effects of atmosphere co2 the earth s orbital parameters and ice sheet albedo tropical temperatures are found to be 2 2 c less than today s slightly colder than indicated by the climap palaeoclimate reconstruction this result is consistent with a low to medium climate sensitivity to radiative perturbations temperatures are colder still in the northern north atlantic region owing to a weakening and shallowing of the thermohaline circulation a sensitivity analysis suggests that changes in ocean circulation since the last glacial maximum have not contributed directly to the global mean temperature change since that time

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

small latitudinal shift in the kuroshio extension central pacific during glacial times evidence from pollen transport the mid latitude area of the central pacific is sensitive to ocean environmental change because latitudinal fluctuation in a transition zone between subtropical and subarctic waters has played an important role in climatic change in east asia the north pacific and north america higher amounts of pollen and spores were found in core h3571 on the hess rise during the glacials than during the interglacials pollen originating from broadleaf deciduous forest in warm and humid environments as well as from boreal conifers and tundra park tundra in cold and wet environments occurred during the glacials the boreal conifer pollen such as tsuga picea and haploxylon could originate from the central japanese archipelago that ephedra was supplied from the asian continent and that the main source regions for the rest of the pollen and spores were from the southern japanese archipelago to the area around the east china sea therefore ocean current transportation was important for the transportation of pollen and spores to the hess rise this evidence demonstrates a small southward shift in the kuroshio extension during the glacials it also suggests that terrestrial organic matter om deposited in the open sea may also be transported by ocean currents reflecting coastal terrestrial environments although it is widely believed that terrestrial om in open sea sediments is of aerosol origin