seasonal variability of the long chain alkenone flux and the effect on the u37k index in the norwegian sea a seasonally varying sedimentation pattern was observed for the alkenone flux measured with sediment traps in the northern north atlantic in the norwegian sea traps were set at 500 1000 and 3000 m the alkenone flux varied between 0 1 and 7 1 g m 2 d 1 and followed the seasonal pattern of the bulk parameters maximum fluxes occurred from mid october until mid november and were also high in may a surprising result was that considerably higher particle fluxes were observed at 3000 m for the alkenone flux the highest additional input of 250 was observed during the period when sediment resuspension was greatest in summer at the barents sea continental margin traps at 1840 and 1950 m the alkenone fluxes follow the sedimentation pattern of the bulk parameters with a less visible signal of distinct seasonality observed in the 1950 m trap the sedimentation of total alkenones varied between 0 8 and 144 g m 2 d 1 at 1840 m and between 0 5 and 31 0 g m 2 d 1 at 1950 m resuspension and lateral advection contributed significantly to measured fluxes in the two near bottom traps alkenone concentrations were determined in faecal pellets of appendicularia ostracods and euphausids from selected samples at the barents sea site the alkenone flux in pellets 4 to 24 of total was 5 to 6 times higher at 1950 m depth than at 1840 m and the major part 77 78 of the total flux of c37 3 reaching the near bottom trap at 1950 m was associated with faecal pellets of the meso zooplankton spatial and temporal variations of the u37k signals were observed indicating that the imprint in the alkenone signal depends on the origin and transport pathway of the organic material strong deviations occur in areas where nepheloid layers contribute particles of long residence times to the primary flux

depth ranges of alkenone production in the central pacific ocean we report analytical results of long chain c 37 c 39 alkenones in the surface sediments taken along a latitudinal transect at 175 e from 48 n to 15 s unsaturation degree of c 37 alkenones u k 37 indicated that alkenone temperature is the highest about 28 3 c in the tropical pacific and decreases toward 48 n about 10 1 c although the latitudinal trend of the alkenone temperature is generally similar to that of the observed sea surface temperature of the surface mixed layer the former exhibits markedly lower values than the latter does in the midlatitude 35 19 n on the basis of the comparisons between water column temperatures and alkenone temperatures in the surface sediments we estimated that in the midlatitudes alkenones are produced in the thermocline waters whereas in the high 48 40 n and low 10 n 2 s latitudes they are produced in the surface mixed layer this result is supported by the depth distribution of emiliania huxleyi and gephyrocapsa oceanica along a 155 w transect in the central pacific the latitudinal distribution of the alkenone production layers estimated from u k 37 is found to be consistent with that of the nitrate suggesting that the depth of alkenone production is mainly controlled by the nutrient supply from deeper waters alkenones in the sediments exhibited relatively large abundances in 43 27 n with a maximum at 30 n which may be explained by high productivity of haptophyte algae in kuroshio extension

the upper end of the uk 37 temperature calibration revisited 1 being able to decipher paleo sea surface temperatures for warm oceanic waters is of the utmost importance to further evaluate the role of the tropics in global climate change the uk 37 index is one of such paleothermometers although the warm range of temperatures often poses serious analytical challenges this paper discusses and reviews several important aspects of the uk 37 index calibration for waters warmer than 26 27 c amongst them insights into the possible existence of a limit above which the uk 37 index is not able to accurately record temperature variations are presented some warnings are also given on the misleading practice and expected consequences of reporting uk 37 index values of unity in the cases when abundances of the minor triunsaturated alkenone below detection limit are encountered future directions toward an improved knowledge of the behaviour of the uk 37 calibration for warm waters are suggested

long chain alkenones and alkyl alkenoates as palaeotemperature indicators their production flux and early sedimentary diagenesis in the eastern north atlantic the production and fate of long chain alkenones and alkenoates was examined with regard to their use as palaeotemperature indicators alkenoate abundances were higher than previously reported for other regions and more strongly correlated with temperature than was alkenone unsaturation u37k suggesting biogeographical variability in alkenone and alkenoate production in surface waters we define the aa36 ratio to parameterize alkenoate abundance and present an empirical temperature calibration derived from our euphotic zone samples for use in the north atlantic t 17 35 25 12 u37k 26 73 aa36 93 90 u37k aa36 significant diagenetic losses of alkenones and alkenoates were found within the water column and near surface sediments in spite of diagenetic losses the temperature signal recorded by these compounds in the sediments remains largely unaltered and corresponds to the euphotic zone water temperature during the springtime period of maximum coccolithophorid production and flux rather than the average annual sea surface temperature

particulate organic carbon fluxes to the ocean interior and factors controlling the biological pump a synthesis of global sediment trap programs since 1983 particulate organic carbon poc is vertically transported to the oceanic interior by aggregates and their ballasts mainly caco3 and biogenic opal with a smaller role for lithogenic aerosols through the mesopelagic zone diel migrating zooplankton communities effect vertical transport and remineralization of poc in the upper layers of the ocean below 1 5 km the presence of zooplankton is reduced and thus the aggregates travel mainly by gravitational transport we normalized the fluxes of poc caco3 and biogenic opal from data published on samples collected at 134 globally distributed bottom tethered time series sediment trap ts trap stations to annual mole fluxes at the mesopelagic bathypelagic boundary m b at 2 km and defined them as fm bcorg fm bcinorg and fm bsibio using this global data set we investigated 1 the geographic contrasts of poc export at m b and 2 the supply rate of co2 to the world mesopelagic water column fm bcorg varies from 25 pacific warm pool to 605 divergent arabian sea mmolc m 2 yr 1 fm bcinorg varies from 8 high latitude polar oceans or 15 pacific warm pool to 459 divergent arabian sea mmolc m 2 yr 1 and fm bsibio the most spatially temporally variable flux ranges from 6 north atlantic drift to 1118 pacific subarctic gyre mmolsi m 2 yr 1 the oceanic region exhibiting the highest poc flux over a significantly large region is the area of the north pacific boreal gyres where the average fm bcorg 213 fm bcinorg 126 and fm bsibio 578 mmol m 2 yr 1 fm bcorg and fm bcinorg are particularly high in large upwelling margins including the divergent arabian sea and off cape verde one of the data sets showing the lowest flux over a significant region basin is fm bcorg 39 fm bcinorg 69 and fm bsibio 22 mmol m 2 yr 1 in the north pacific subtropical tropical gyres pan atlantic average fluxes are similar except fm bsibio fluxes are even lower where corg cinorg and sibio cinorg are 1 defines the carbonate ocean and where these ratios are 1 defines the silica ocean the carbonate ocean occupies about 80 of the present world pelagic ocean between the two major oceanographic fronts the north pacific polar front and the antarctic polar front and the silica ocean is found on the polar sides of these fronts the total global annual fluxes of fm bcorg fm bcinorg and fm bsibio at m b calculated by parameterizations of the export flux data from 134 stations are surprisingly similar 36 2 33 8 and 34 6 teramol yr 1 120 112 and 114 mmol m 2 yr 1 respectively resulting in a near uniform binary ratio between the above three elements of about one the global ternary ratios estimated from 152 ts trap samples of the three elements are 35 32 33 from our global fm bcorg and a published model estimate of the global export production we estimate the regeneration rate of co2 through the mesopelagic zone by the biological pump is 441 teramolc yr 1 based on our global fm bcinorg and recently estimated global primary production of pic 36 86 teramolc yr 1 of pic is assumed to be dissolved within the upper 2 km of the water column

links between iron supply marine productivity sea surface temperature and co2 over the last 1 1 ma received 3 july 2008 revised 9 october 2008 accepted 27 october 2008 published 14 february 2009 1 paleoclimatic reconstructions have provided a unique data set to test the sensitivity of climate system to changes in atmospheric co2 concentrations however the mechanisms behind glacial interglacial g ig variations in atmospheric co2 concentrations observed in the antarctic ice cores are still not fully understood here we present a new multiproxy data set of sea surface temperatures sst dust and iron supply and marine export productivity from the marine sediment core ps2489 2 odp site 1090 located in the subantarctic atlantic that allow us to evaluate various hypotheses on the role of the southern ocean so in modulating atmospheric co2 concentrations back to 1 1 ma we show that antarctic atmospheric temperatures are closely linked to changes in so surface temperatures over the last 800 ka and use this to synchronize the timescales of our marine and the european project for ice coring in antarctica epica dome c edc records the close correlation observed between iron inputs and marine export production over the entire interval implies that the process of iron fertilization of marine biota has been a recurrent process operating in the subantarctic region over the g ig cycles of the last 1 1 ma however our data suggest that marine productivity can only explain a fraction of atmospheric co2 changes up to around 40 50 ppmv occurring at glacial maxima in each glacial stage in this sense the good correlation of our sst record to the edc temperature reconstruction suggests that the initial glacial co2 decrease as well as the change in the amplitude of the co2 cycles observed around 400 ka was most likely driven by physical processes possibly related to changes in antarctic sea ice extent surface water stratification and westerly winds position

biomarker temperature estimates for modern and last glacial surface waters of the california current system between 33 and 42 n sea surface temperature sst estimates were made using data for c37 39 alkenones analyzed in modern and glacial age intervals of sediment cores collected along an east west 42 n from 125 to 132 w and a north south 41 33 n transect of the california current system ccs the prymnesiophyte biomarker results suggest that surface waters warmed significantly throughout this region since the last glacial maximum lgm but the magnitude of warming varied spatially stratigraphic profiles from four sediment cores along the north south transect indicate the warming period was confined to the glacial interglacial transition 15 10 ka with sst reaching a maximum value at 10 ka and maintaining a uniformly high value throughout the holocene comparison of estimates derived from analysis of modern and lgm sediment intervals indicates the magnitude of the sst change was minimal for locations south of about 36 n 1 2 c and increased significantly 3 5 c north of this latitude using a simple heat balance model we calculate from the latitudinal gradient in sst that southward flow in the california current system during the lgm was about 60 of that measured today at 36 n our findings support the conclusion of others based on pollen data that coastal upwelling in the region of the northeast pacific off northern california was significantly reduced or even completely shutdown during the lgm

comparison of alkenone estimates with other paleotemperature proxies 1 to a certain degree all sea surface temperature sst proxies suffer from uncertainty due to signal preservation problems and to perturbations by other environmental variables however a multiproxy reconstruction is justified because most biases should in principle cancel out as they are specific to the biological groups and or to the analyzed chemical species such a multiproxy strategy has proven crucial for calibrating these proxies and is also useful in assessing downcore profiles until now there have been only a dozen deep sea cores where it is possible to compare directly alkenone based ssts with other paleotemperature records from this still limited data set the broad picture is of general agreement for the amplitude of changes at low and middle latitudes the few observed discrepancies suggest that alkenone based temperatures are more comparable to those based on mg ca ratios than those obtained through statistical analysis of the foraminiferal distribution more systematic differences are noted at higher latitudes where alkenones indicate warmer temperatures during the glacial period than transfer functions based on foraminifera or diatoms several reasons have been invoked to resolve the mismatch but more ground truthing work is needed before deciding which temperature changes are the most accurate

disentangling seasonal signals in holocene climate trends by satellite model proxy integration past sea surface temperatures ssts are routinely estimated from organic and inorganic remains of fossil phytoplankton or zooplankton organisms recovered from sea floor sediments potential seasonal biases of paleo proxies were intensely studied in the past however even for the two most commonly used paleo proxies for sst uk0 37 and mg ca ratios a clear global picture does not yet exist in the present study we combine holocene sst trends derived from uk0 37 and mg ca ratios with results from idealized climate model simulations forced by changes in the orbital conguration which represents the major climate driver over the last 10 kyrs such changes cause a spatio temporal redistribution of incoming solar radiation resulting in a modulation of amplitude and phasing of the seasonal cycle considering that the climate signal recorded by a plankton based paleo proxy may be aected by the seasonal productivity cycle of the respective organism we use the modern relationship between sst and marine net primary production npp both obtained from satellite observations to calculate a seasonality index si as an independent constraint to link modeled sst trends with proxy data although the climate model systematically underestimates holocene sst trends we find that seasonal productivity peaks of the phytoplankton based uk0 37 result in a preferential registering of the warm cold season in high low latitudes as it was expected from the si distribution the overall smoother trends from the zooplankton derived mg ca ssts suggest a more integrated signal over longer time averages which may also carry a seasonal bias but the spatial pattern is less clear based on our ndings careful multi proxy approaches can actually go beyond the reconstruction of average climate trends specifically allowing to resolve the evolution of seasonality

sulfur and oxygen isotope studies of melt country rock interaction babbitt cu ni deposit duluth complex minnesota the babbitt cu ni deposit formerly known as minnamax occurs within troctolitic and gabbroic rocks of the precambrian duluth complex both massive and disseminated mineralizations are found in the deposit pyrrhotite cubanite chalcopyrite and minor pentlandite mineralization occurs near the basal contact with pelitic metasedimentary rocks of the virginia formation or higher in the igneous sequence associated with abundant country rock xenoliths cloud zones sulfur and oxygen isotope studies have been carried out to evaluate the importance of melt country rock interaction in localizing sulfide mineralization the delta 34 s values of pyrrhotite plus pyrite from the virginia formation located outside the contact aureole range from 5 6 to 13 7 per mil pyrrhotite from footwall virginia formation hornfels or inclusions in the basal zone exhibits delta 34 s values ranging from 1 5 to 6 2 per mil whereas delta 34 s values of pyrrhotite from xenoliths in cloud zones range from 2 6 to 21 4 per mil isotopic values of basal zone cu ni sulfides range from 6 0 to 13 0 per mil with a mode at 8 to 9 per mil two features highlight basal zone delta 34 s values first delta 34 s values of sulfide mineralization are higher than those of pyrrhotite in immediately adjacent virginia formation hornfels second higher grade ore areas 1 cu show 34 s enrichment with delta 34 s values in the range of 9 to 13 per mil sulfides in cloud zones show a wide range in delta 34 s values from 0 7 to 19 7 per mil sulfur isotope data suggest that most of the sulfur found in the deposit has been derived from sedimentary country rocks however an in situ process of sulfur derivation is not indicated sulfur in basal mineralized zones must have been derived at depth within an auxiliary magma chamber or during magma ascent and emplacement isotopic homogenization was not achieved during the sulfide forming process as evidenced by the spatial variability of delta 34 s values oxygen isotope values of both mildly metamorphosed virginia formation and footwall hornfels range from 8 2 to 14 0 per mil inclusions of virginia formation show pronounced isotopic effects due to interaction with melt xenolith margins may have values as low as 7 to 8 per mil and are depleted in 18 o with respect to xenolith interiors the delta 18 o values of igneous rocks from the babbitt deposit range from 3 9 to 12 2 per mil zones of 18 o depletion are rare and suggest that exchange with a low 18 o fluid phase was spatially restricted anomalous delta 18 o values in excess of 7 to 7 5 per mil are common throughout the deposit but are limited to within 3 m of virginia formation xenoliths a model of diffusion controlled 18 exchange between igneous material and xenoliths best describes the delta 18 o distribution devolatilization and desilicification of the xenoliths occurred early in their history when physical mixing in the host magma was possible addition of high 18 o material from these processes into a large volume of melt affected delta 18 o distributions only slightly continued exchange of oxygen after major cation transfer produced the observed delta 18 o profiles in the case of basal zone cu ni mineralization at babbitt isotopic evidence indicates that sulfide saturation was not caused by in situ addition of sulfur silica or oxygen sulfide saturation is thought to have been achieved at depth triggered by assimilation of large quantities of sulfide liberated through devolatilization reactions occurring in country rocks

oceanographic considerations for the application of the alkenone based paleotemperature u37k index in the gulf of california abstract alkenone concentrations were determined in sediment trap samples and surficial sediments collected from guaymas basin gulf of california to investigate the factors that control the relationship between the u37k index and sst the results from the sediment trap study reveal a positive correlation r2 0 5 between alkenone fluxes and satellite avhrr sea surface temperature sst and a strong correlation r2 0 9 between u37k and sst over an annual temperature range of 20 c although sst and u37k are tightly coupled throughout two upwelling seasons the relationship deviates from the expression developed by prahl et al 1988 at temperatures higher than 26 c the possible reasons for this deviation are varied but include the observed changes in the coccolithophore species assemblage and the evolution of the thermocline during periods of high sst the seasonal pattern of alkenone fluxes higher fluxes during warm periods observed throughout the 1996 to 1997 study period causes a bias in the annually averaged u37k record resulting in temperature estimates that are 1 c higher than the annual avhrr sst average furthermore the u37k ratios obtained from core top sediments indicate an additional 2 c warm bias in the sedimentary record that may be related to the lateral inputs of alkenones from other regions of the gulf these results highlight the importance of oceanographic processes in determining the alkenone temperature signal that is preserved in sediments after accounting for such effects u37k ratios from a box core were used to reconstruct a sst record extending back to the 18th century for the guaymas basin these results indicate a steady 2 c warming of the surface waters of the gulf from early 1700s to the 1950s followed by a rapid apparent 1 c cooling between the 1950s and the 1980s

north pacific seasonality and the glaciation of north america 2 7 million years ago in the context of gradual cenozoic cooling the timing of the onset of significant northern hemisphere glaciation 2 7 million years ago is consistent with milankovitch s orbital theory which posited that ice sheets grow when polar summertime insolation and temperature are low however the role of moisture supply in the initiation of large northern hemisphere ice sheets has remained unclear the subarctic pacific ocean represents a significant source of water vapour to boreal north america but it has been largely overlooked in efforts to explain northern hemisphere glaciation here we present alkenone unsaturation ratios and diatom oxygen isotope ratios from a sediment core in the western subarctic pacific ocean indicating that 2 7 million years ago late summer sea surface temperatures in this ocean region rose in response to an increase in stratification at the same time winter sea surface temperatures cooled winter floating ice became more abundant and global climate descended into glacial conditions we suggest that the observed summer warming extended into the autumn providing water vapour to northern north america where it precipitated and accumulated as snow and thus allowed the initiation of northern hemisphere glaciation

atlantic core top calibration of the u37k index as a sea surface palaeotemperature indicator abstract a field calibration of the uk index with sea surface temperature is discussed through analysis of an extensive suite of surface sediments n 109 from the northeastern atlantic 2 s 75 n values of u 37 k are compared with sea surface temperatures for overlying waters measured at different depths and seasons to obtain a correlation suitable for palaeotemperature reconstructions the best fit is obtained using surface 0 m temperatures corresponding to caloric winter and autumn months however the annual average spring and summer surface temperature equations also have high correlation coefficients and are also appropriate for climatic studies the results further validate the general applicability of the u 37 k as a climatic proxy because the calibration equations are valid over a wide range of surface water temperatures 0 28 c for different algal populations and are representative of the average contribution of alkenones to sediments as found in sediment cores

depth and seasonality of alkenone production along the california margin inferred from a core top transect alkenone unsaturation indices uk 37 of marine sediment could prove particularly useful on organic rich continental margins where carbonate dissolution hampers the use of other paleoclimatic proxies mccaffrey et al 1990 kennedy and brassell 1992 forty core top samples of recent sediment from a latitudinal transect 23 40 n along the california margin yield uk 37 values that correlate linearly with modern mean annual sea surface temperatures ssts in the range of 12 23 c reproducibility of the unsaturation value in closely spaced cores is near analytical error uk 37 data define a relationship to temperature nearly identical to the prahl et al 1988 laboratory cultures of emiliania huxleyi the close agreement is particularly significant in light of the nannofossil composition of the sediments where the abundance of the coccolith taxon gephyrocapsa oceanica known to synthesize alkenones equals or exceeds that of e huxleyi comparison with seasonal temperature variations at different depths indicates that little if any alkenone production occurs at depths 30 m along the continental margin water depths 2 km sediments in more pelagic locations exhibit small but consistent biases toward winter and or subsurface production similar to previously reported sediment trap and core top data from the oregon margin prahl et al 1993 doose et al 1997

faunal and alkenone reconstructions of subtropical north atlantic surface hydrography and paleotemperature over the last 28 kyr two techniques for estimating past variations in sea surface temperature sst have been used to investigate climatic change in biogeochemical oceanic flux study bofs core 31k 19 n 20 w from the eastern subtropical atlantic high resolution sst records for the last 28 kyr have been produced using planktonic foraminiferal assemblages based on the imbrie kipp transfer function technique and the uk 37 index derived from abundances of c37 alkenones biosynthesized by prymnesiophyte algae modern observations suggest that these indices reflect particular hydrographic conditions in the upper ocean the uk 37 index corresponds to the temperature at the time of maximum coccolith productivity typically late spring early summer in the study area today whereas the faunal transfer function is calibrated for seasonal maximum and minimum temperatures in general the faunal and biomarker paleotemperature records display comparable sst variations during the last glacial and deglacial but although the overall trends are similar differences exist in the magnitude and timing of these temperature changes most notably the faunal twarm and uk 37 sst estimates diverge by 3 c between 8 ka and 6 ka and this offset persists through the late holocene this difference cannot be adequately explained by uncertainties associated with either the calibration data sets or fluctuating preservation levels we therefore propose that the deviation in sst estimates is linked to a switch in the seasonal timing of maximum coccolith production from the summer in the glacial ocean to the late spring early summer in the modern ocean our results suggest that a dual approach to sst estimation based on faunal and biomarker proxies can provide a valuable means of evaluating mixed layer and productivity changes associated with the movement of oceanographic frontal zones during the late quaternary

seasonality of u k 37 temperature estimates as inferred from sediment trap data abstract the seasonality of sea surface temperatures sst estimated from the alkenone u k 37 index has been a debated issue since the development of the proxy using a compilation of sediment trap time series data from 34 sampling locations we show that the seasonality of maximum alkenone flux in sediment traps varies markedly across the oceans depending not only on latitude and light availability but also on local oceanographic conditions the seasonality of the alkenone flux to sediments may also be shaped by the complexity of sedimentation processes and a consistent globally applicable seasonal pattern is not apparent nevertheless u k 37 values display a world ocean scale correlation with mean annual ssts 0 m that closely resembles the standard calibration equation now established for modern surface sediment records thus with a few notable exceptions at oceanographic locations proximate to major hydrographic fronts it can be concluded that the integrated sedimentation patterns for u k 37 measured in sediment trap time series provide a measure of annual mean sst

glacial interglacial sea surface temperature changes across the subtropical front east of new zealand based on alkenone unsaturation ratios and foraminiferal assemblages 0 are compared to those derived from foraminiferal assemblages using the modern analog technique in two of these cores reconstructions of sst in core tops and holocene sediments agree well with modern average summer temperatures of 18 c in subtropical waters and 14 c in subpolar waters with a 4 5 c gradient across the front down core u37 k 0 sst estimates indicate that the regional summer sst was 4 5 c cooler during the last glaciation with an sst of 10 c in subpolar waters and an sst of 14 c in subtropical waters temperature reconstructions from foraminiferal assemblages agree with those derived from alkenones for the holocene in subtropical waters reconstructions also agree with a glacial cooling of 4 to 14 c in contrast reconstructions for subantarctic pre holocene waters indicate a cooling of 8 c with glacial age warm season water temperatures of 6 c thus the alkenones suggest the glacial temperature gradient across the front was the same or reduced slightly to 3 5 4 c whereas foraminiferal reconstructions suggest it doubled to 8 c our results support previous work indicating that the stf remained fixed over the chatham rise during the last glacial maximum however the differing results from the two techniques require additional explanation a change in euphotic zone temperature profiles seasonality of growth or preferred growth depth must have affected the temperatures recorded by these biologically based proxies regardless of the specific reason a differential response to the environmental changes between the two climate regimes by the organisms on which the estimates are based suggests increased upwelling associated with increased winds and or a shallowing of the thermocline associated with increased stratification of the surface layer in the last glaciation index terms 4267 oceanography general paleoceanography 4850 oceanography biological and chemical organic marine chemistry 1050 geochemistry marine geochemistry 4835 4850 1055 geochemistry organic geochemistry keywords paleoceanography sea surface temperature alkenones southern ocean last glacial maximum

holocene and eemian sea surface temperature trends as revealed by alkenone and mg ca paleothermometry in this study we review a global set of alkenone and foraminiferal mg ca derived sea surface temperatures sst records from the holocene and compare them with a suite of published eemian sst records based on the same approach for the holocene the alkenone sst records belong to the actualized ghost database kim j h schneider r r 2004 ghost global database for alkenone derived holocene sea surface temperature records available from http www pangaea de projects ghost while the mg ca derived sst database represents a new compilation the actualized ghost database not only confirms the sst changes previously described but also documents the holocene temperature evolution in new oceanic regions such as the northwestern atlantic the eastern equatorial pacific and the southern ocean a comparison of holocene sst records stemming front the two commonly applied paleothermometry methods reveals contrasting sometimes divergent sst evolution particularly at low latitudes where sst records are abundant enough to infer systematic discrepancies at a regional scale opposite sst trends at particular locations could be explained by out of phase trends in seasonal insolation during the holocene this hypothesis assumes that a strong contrast in the ecological responses of coccolithophores and planktonic foraminifera to winter and summer oceanographic conditions is the ultimate reason for seasonal differences in the origin of the temperature signal provided by these organisms as a simple test for this hypothesis eemian sst records are considered because the holocene and eemian time periods experienced comparable changes in orbital configurations but had a higher magnitude in insolation variance during the eemian for several regions sst changes during both interglacials were of a similar sign but with higher magnitudes during the eemian as compared to the holocene this observation suggests that the ecological mechanism shaping sst trends during the holocene was comparable during the penultimate interglacial period although this ecology hypothesis fails to explain all of the available results we argue that any other mechanism would fail to satisfactorily explain the observed sst discrepancies among proxies c 2010 elsevier ltd all rights reserved

distributions of uk37 and uk37 in the surface waters and sediments of the nordic seas implications for paleoceanography in this paper we revise the application of the u and u indices as sea surface temperature sst proxies in the nordic seas in the summer of 1999 and 2000 we obtained samples of filtered particulate organic matter pom from surface waters 6 m depth of the nordic seas a number of samples were collected from polar waters with up to 80 of sea ice cover alkenones were detected in all of the major water masses of the nordic seas across a spectrum of sst values from 0 5 to 13 c and sss values from 29 6 to 35 6 psu concentrations of alkenones were similar in magnitude to those reported previously for the north atlantic and the southern ocean values of u from the new nordic seas pom data show no correlation with sst below 8 c in contrast below this temperature a linear correlation exists between u and regional sst supporting previous suggestions that overall u may be a more appropriate sst index for the region it must be noted however that u is calculated using the tetraunsaturated alkenone and the dominant control on this compound is not yet fully understood the new data highlight major differences between distributions of u and u in the water column pom and surficial sediments of the nordic seas we also examine the geographical dependence of the u versus sst relationship in the region s surficial sediments some areas are associated with unreliable sst estimates whereas in others the u versus sst relationship falls within the range of a global core top calibration it is suggested that the breakdown of the u sst relationship in some regions is due to ecological and sedimentological factors the latter relates to the extension of the habitats of alkenone producers in polar waters the former to the resuspension of sediments and laterally transported alkenone inputs this suggests that accurate alkenone derived sst estimates in the nordic seas are geographically constrained

factors controlling the flux of organic carbon to the bathypelagic zone of the ocean 1 particle fluxes measured with time series sediment traps deployed below 2000 m at 68 sites in the world ocean are combined with satellite derived estimates of export production from the overlying water to assess the factors affecting the transfer of particulate organic matter from surface to deep water multiple linear regression is used to derive an algorithm suggesting that the transfer efficiency of organic carbon defined as the settling flux of organic carbon normalized to export production increases with the flux of carbonate and decreases with water depth and seasonality the algorithm predicts 80 of the organic carbon transfer efficiency variability in diverse oceanic regions the influence of the carbonate flux suggests that the ballasting effect of this biogenic mineral may be an important factor promoting export of organic carbon to the deep sea by increasing the density of settling particles however the lack of a similar effect for biogenic opal suggests that factors other than particle density also play a role the adverse effect of increasing seasonality on the transfer efficiency of carbon to the deep sea is tentatively attributed to greater biodegradability of organic matter exported during bloom events in high latitude opal dominated regions with high f ratios and seasonality while a higher fraction of net production is exported a higher fraction of the exported organic matter is remineralized before reaching bathypelagic depths on the other hand in warm low latitude carbonate dominated regions with low f ratios and seasonality a higher fraction of the exported organic matter sinks to the deep sea

global temperature calibration of the alkenone unsaturation index uk 37 in surface waters and comparison with surface sediments in this paper we compile the current surface seawater c37 alkenone unsaturation uk 37 measurements n 629 1 to 30 c temperature range to derive a global field based calibration of uk 37 with alkenone production temperature a single nonlinear global surface water calibration of uk 37 accurately predicts alkenone production temperatures over the diversity of modern day oceanic environments and alkenone synthesizing populations t 0 957 54 293 uk 37 52 894 uk 37 2 28 321 uk 37 3 r2 0 97 n 567 the mean standard error of estimation is 1 2 c with insignificant bias in estimated production temperature among the different ocean regions sampled an exception to these trends is regions characterized by strong lateral advection and extreme productivity and temperature gradients e g the brazil malvinas confluence in contrast to the surface water data the calibration of uk 37 in surface sediments with overlying annual mean sea surface temperature anno is best fit by a linear model anno 29 876 uk 37 1 334 r2 0 97 n 592 the standard error of estimation 1 1 c is similar to that of the surface water production calibration but a higher degree of bias is observed among the regional data sets the sediment calibration differs significantly from the surface water calibration uk 37 in surface sediments is consistently higher than that predicted from anno and the surface water production temperature calibration and the magnitude of the offset increases as the surface water anno decreases we apply the global production temperature calibration to the coretop uk 37 data to estimate the coretop alkenone integrated production temperature coretop ipt and compare this with the overlying annual mean sea surface temperature anno we use simple models to explore the possible causes of the deviation observed between the coretop temperature signal as estimated by uk 37 and anno our results indicate that the deviation can best be explained if seasonality in production and or thermocline production as well as differential degradation of 37 3 and 37 2 alkenones both affect the sedimentary alkenone signal

alkenone temperature anomalies in the brazil malvinas confluence area caused by lateral advection of suspended particulate material alkenone temperatures derived from suspended particulate organic material which was collected in austral summer 2001 from surface waters 5 m south of the brazil malvinas confluence deviate from measured temperatures by 4 to 7 c when uk 37 ratios are converted to temperature using the muller et al 1998 calibration and up to 3 c when using the calibration of conte et al 2006 in contrast alkenone temperatures determined from particulate material sampled north of the confluence reveal close correspondence to in situ temperatures or show slightly higher values we suggest that the southern samples are biased by suspended organic detritus originating from the cold subpolar waters of the northward flowing malvinas current whereas the northern samples carry an uk 37 signal of tropical subtropical origin transported southward with the brazil current on the basis of surface ocean transport pathways and velocities simulated with the large scale geostrophic lsg ocean general circulation model we identify areas of the world ocean where alkenone temperatures are potentially biased to higher or lower values due to long particle residence times and lateral advection by surface currents

the role of southern ocean processes in orbital and millennial co2 variations a synthesis abstract recent progress in the reconstruction of atmospheric co 2 records from antarctic ice cores has allowed for the documentation of natural co 2 variations on orbital time scales over the last up to 800 000 years and for the resolution of millennial co 2 variations during the last glacial cycle in unprecedented detail this has shown that atmospheric co 2 varied within natural bounds of approximately 170 300 ppmv but never reached recent co 2 concentrations caused by anthropogenic co 2 emissions in addition the natural atmospheric co 2 concentrations show an extraordinary correlation with southern ocean climate changes pointing to a significant direct or indirect influence of climatic and environmental changes in the southern ocean region on atmospheric co 2 concentrations here we compile recent ice core and marine sediment records of atmospheric co 2 temperature and environmental changes in the southern ocean region as well as carbon cycle model experiments in order to quantify the effect of potential southern ocean processes on atmospheric co 2 related to these orbital and millennial changes this shows that physical and biological changes in the so are able to explain substantial parts of the glacial interglacial co 2 change but that none of the single processes is able to explain this change by itself in particular changes in the southern ocean related to changes in the surface buoyancy flux which in return is controlled by the waxing and waning of sea ice may favorably explain the high correlation of co 2 and antarctic temperature on orbital and millennial time scales in contrast the changes of the position and strength of the westerly wind field were most likely too small to explain the observed changes in atmospheric co 2 or may even have increased atmospheric co 2 in the glacial also iron fertilization of the marine biota in the southern ocean contributes to a glacial drawdown of co 2 but turns out to be limited by other factors than the total dust input such as bioavailability of iron or macronutrient supply

molecular stratigraphy a new tool for climatic assessment variations in sea surface temperatures over the past 500 000 years are inferred from the relative abundance behaviour of two organic compounds c37 alkenones over the upper 8 metres of a sediment core from the eastern equatorial atlantic this molecular record ascribed to contributions from prymnesiophyte algae correlates well with the variations in the 18 signal for the calcareous skeletons of certain planktonic foraminifera thus providing the first demonstration of a new stratigraphical technique which may be especially valuable where methods based on carbonate 18 fail

comparison of settling particles and sediments at images coring site in the northwestern north pacific effect of resuspended particles on paleorecords abstract in order to understand settling process of particles in high sedimentation area one mooring of sediment trap was deployed right above the images coring site in the northwestern north pacific in spite of two large maxima of settling particle fluxes in june july 2002 and october early january 2003 organic matter om and carbonate showed higher peaks in june july while lithogenics showed a large peak in october early january with degraded om low aspartic acid beta alanine asp bala and glutamic acid gamma aminobutyric glu gaba ratios fresh om production peaked in june july 2002 and april may 2003 thus a large export production occurred in spring early summer april june alkenone production was enhanced mainly in june july the mean alkenone sst of the settling particles was rather consistent with the observed annual mean sst and alkenone sst determined from the surface sediments on the other hand the maximum lithogenic flux along with the degradation of om indicated that a significant amount of resuspended matter contaminated the bottom sediments based upon idealized model the current and settling speeds make fractionation by size and density of resuspended particles during the settling process accumulation rates of lithogenics were 5 times those in the sediment traps which indicate large contribution of resuspended particles to settling particles especially during october early january when the tsugaru current showed high current speed these observations call our attention to carefully reconstruct paleo environments based upon lithogenics and several other proxies such as biogenic silica which would be biased for example in the record of images core at site shimokita located on the gentle continental slope

systematic pattern in u37k temperature residuals for surface sediments from high latitude and other oceanographic settings abstract twenty seven multicores collected in late summer 2004 from coastal and inland marine sites throughout se alaska 55 to 61 n were analyzed for c 37 to c 39 alkenones of specific haptophyte origin this biomarker signal detected in core top sediments from 20 of the sites was quantitatively most significant in organic carbon and biogenic silica rich sediments deposited south of icy strait 58 n along the outer coastline of baranof and prince of wales islands u 37 k based water temperature estimates derived using a standard calibration equation u 37 k 0 034t 0 039 were uniform throughout the study area averaging 11 9 1 0 c a value 4 c warmer than mean annual sst masst for the region epoxides indicative of selective alkenone degradation by an aerobic bacterial process were also detected and quantified in all sediments containing alkenones semi quantitative accounting of the impact that compound selective degradation can impose on alkenone unsaturation patterns indicates the standard u 37 k based temperature estimates could be too warm by a variable amount 0 7 2 4 c depending upon the site with an overall average of 1 4 c even after adjustment for this potential diagenetic warming effect estimates still best match summer and not masst in this subarctic region re examination of alkenone signatures preserved in sediment from the north atlantic and on the continental margin located south of 45 s along the chilean coast indicates the apparent summer signal in u 37 k derived sst estimates is not unique to se alaskan sediments but rather a common finding when alkenone thermometry is applied to sediments from high latitude environments examination of model residuals from analysis of surface sediment samples collected at lower latitude settings along the west coast of the americas also identifies other sites where significant biogeographic patterns seem apparent and viable oceanographic explanations can be offered

characteristics of alkenone distributions in suspended and sinking particles in the northwestern north pacific abstract we investigated alkenones recorded in suspended particles and a settling particle time series collected at three stations 40n 40 n 165 e knot 44 n 155 e and 50n 50 n 165 e in the northwestern north pacific from december 1997 to may 1999 emiliania huxleyi the most abundant alkenone producer in this area is present in surface to subsurface to 50 m depth waters the alkenone concentrations recorded in the suspended particles indicated that the seasonal alkenone particle distribution differed significantly interannually alkenone export fluxes at the three sediment trap stations ranged from 0 16 to 49 3 g m 2 day 1 and the maximum export flux which occurred in summer to fall july november was associated with a high organic carbon export flux the amount of alkenone produced during the maximum export season accounted for 60 80 of the total annual amount of alkenone and the alkenones accumulated in the sediment below the traps had characteristics corresponding to subsurface waters during the summer autumn season alkenone derived temperatures recorded in suspended particles corresponded to the in situ temperature within 2 c although alkenone derived temperatures corresponded approximately to the temperatures observed in the stratified subsurface waters at the three trap stations during the high export season large differences were observed during the low export winter spring period for example the alkenone derived temperatures observed at stations knot and 50n were much higher than the in situ subsurface temperatures reported in the world ocean atlas 2001 relatively large differences between alkenone derived temperatures and in situ temperatures in the subarctic might be due to 1 a low light limitation or 2 contributions of allochthonous alkenones in particulate material transported from subtropical areas within a warm core ring