southwest pacific deep water carbonate chemistry linked to high southern latitude climate and atmospheric co2 during the last glacial termination abstract a greater amount of co2 was stored in the deep sea during glacial periods likely via greater efficiency of the biologic pump and increased uptake by a more alkaline ocean reconstructing past variations in seawater carbonate ion concentration a major component of alkalinity enables quantification of the relative roles of different oceanic co2 storage mechanisms and also places constraints on the timing magnitude and location of subsequent deep ocean ventilation here we present a record of deep water inorganic carbon chemistry since the last glacial maximum lgm 19 23 ka bp derived from sediment core rr0503 83 raised from 1627 m in new zealand s bay of plenty the core site lies within the upper limit of southern sourced circumpolar deep water cdw just below the lower boundary of antarctic intermediate water aaiw we reconstruct past changes in bottom water inorganic carbon chemistry from the trace element and stable isotopic composition of calcite shells of the epibenthic foraminifer cibicidoides wuellerstorfi a record of co 3 2 co 3 2 co 3 2 i n s i t u co 3 2 saturation derived from the foraminiferal boron to calcium ratio b ca provides evidence for greater ice age storage of respired co2 and reveals abrupt deglacial shifts in co 3 2 i n s i t u of up to 30 mol kg 5 times larger than the difference between average lgm and holocene values the rapidity of these changes suggests the influence of changing water mass structure and atmospheric circulation in addition to a decrease in co2 content of interior waters

contribution of small glaciers to global sea level observed long term changes in glacier volume and hydrometeorological mass balance models yield data on the transfer of water from glaciers excluding those in greenland and antarctica to the oceans the average observed volume change for the period 1900 to 1961 is scaled to a global average by use of the seasonal amplitude of the mass balance these data are used to calibrate the models to estimate the changing contribution of glaciers to sea level for the period 1884 to 1975 although the error band is large these glaciers appear to account for a third to half of observed rise in sea level approximately that fraction not explained by thermal expansion of the ocean

diatom bound 15n 14n new support for enhanced nutrient consumption in the ice age subantarctic 1 diatom bound 15n 14n was used to reconstruct the glacial nutrient status of the subantarctic zone in the southern ocean down core records from both the pacific and indian sectors show 15n of 5 to 6 during the last glacial maximum and a decrease coincident with the glacial termination to values as low as 2 the effect of either diatom assemblage or physiological change on the diatom bound 15n 14n is unknown and cannot yet be ruled out as a possible explanation for the observed change however the consistency between indian and pacific sector records and with other paleoceanographic data suggests that the glacial interglacial difference in diatom bound 15n 14n was driven by higher consumption of nitrate in the subantarctic surface during the last ice age such a change in nutrient consumption may have resulted from atmospheric iron fertilization and or decreased glacial mixed layer depths associated with sea ice melting enhanced nutrient consumption in the glacial subantarctic would have worked to lower the concentration of co2 in the ice age atmosphere it also would have reduced the preformed nutrient content of the low latitude thermocline leading to decreases in low latitude productivity suboxia and denitrification

subantarctic mode water in the southeast pacific effect of exchange across the subantarctic front 1 this study considered cross frontal exchange as a possible mechanism for the observed along front freshening and cooling between the 27 0 and 27 3 kg m 3 isopycnals north of the subantarctic front saf in the southeast pacific ocean this isopycnal range which includes the densest subantarctic mode water samw formed in this region is mostly below the mixed layer and so experiences little direct air sea forcing data from two cruises in the southeast pacific were examined for evidence of cross frontal exchange numerous eddies and intrusions containing polar frontal zone pfz water were observed north of the saf as well as a fresh surface layer during the summer cruise that was likely due to ekman transport these features penetrated north of the saf even though the potential vorticity structure of the saf should have acted as a barrier to exchange an optimum multiparameter omp analysis incorporating a range of observed properties was used to estimate the cumulative cross frontal exchange the omp analysis revealed an along front increase in pfz water fractional content in the region north of the saf between the 27 1 and 27 3 kg m 3 isopycnals the increase was approximately 0 13 for every 15 of longitude between the 27 0 and 27 1 kg m 3 isopycnals the increase was approximately 0 15 for every 15 of longitude a simple bulk calculation revealed that this magnitude of cross frontal exchange could have caused the downstream evolution of samw temperature and salinity properties observed by argo profiling floats

diatom productivity in the equatorial pacific ocean from the last glacial period to the present a test of the silicic acid leakage hypothesis 1 the silicic acid leakage hypothesis salh suggests that during glacial periods unused silicic acid escaped the southern ocean into the equatorial oceans causing an ecological shift favoring diatoms relative to coccolithophorids and a drawdown of co2 the 230th normalized opal fluxes and 231pa 230th ratios were measured in eleven equatorial pacific cores to reconstruct diatom productivity over the past 30 kyr and to test the salh holocene spatial patterns of opal flux are strongly correlated with 231pa 230th ratios and with satellite estimates of primary productivity down core opal flux records do not support the salh but show holocene opal burial to exceed that of the late glacial period by 35 or 2 8 gt opal kyr across the equatorial pacific this suggests that the salh may not account for lower atmospheric co2 levels during the late glacial however the data do support results from previous studies that invoke increased el nino like conditions during this time

nitrogen isotopic evidence for deglacial changes in nutrient supply in the eastern equatorial pacific 1 the eastern equatorial pacific eep is a high nutrient low chlorophyll region of the ocean downcore nitrogen isotope records from the eep have been previously interpreted as a direct reflection of changes in nutrient consumption however the observed changes in sedimentary 15n since the last glacial maximum have no coherent relationship with export productivity or an inferred variation in the iron to nitrate ratio of the surface waters rather downcore n isotope records in the eep strongly resemble changes in the extent of water column denitrification as recorded in nearby sedimentary 15n records along the western margin of the americas this similarity is attributed to the overprinting of the n isotopic composition of nitrate in the eep through the advection of nitrate westward from the margins in the subsurface a local nitrogen isotope record of changes in the degree of nutrient consumption is extracted from the bulk sedimentary record by subtracting two different sedimentary 15n records of denitrification changes from two new eep 15n records tr163 22 and odp site 1240 the denitrification records used are from 1 the central american margin odp site 1242 and 2 the south american margin geob7139 2 the degree of consumption in the surface waters declines rapidly from elevated values during the last glacial maximum to a pair of minima around 15 and 11 13 ka and finally it increases into the holocene the derived eep nitrogen isotope record indicates that the regional peak in export productivity occurred when the supply of nutrients exceeded the apparently high demand the influx of nutrients during the deglaciation is attributed to the resumption of intense overturning in the southern ocean and the release of sequestered co2 and nutrient rich o2 poor waters from the deep ocean this has important implications for understanding the glacial interglacial scale variation in intermediate water suboxia and water column denitrification

western pacific coastal sources of iron manganese and aluminum to the equatorial undercurrent 1 we present results from the first zonal transect of iron aluminum and manganese conducted from the western source region of the equatorial undercurrent euc to the central equatorial pacific trace metals were elevated along the slope of papua new guinea and within the new guinea coastal undercurrent ngcu which is the primary southern hemisphere entry path of water to the euc subsurface maxima in total acid soluble iron aluminum and manganese were evident in the euc these maxima were generally greatest in the western equatorial pacific and decreased in magnitude eastward maxima in iron and aluminum persisted to 140 w maxima in manganese extended to 175 w iron and manganese maxima were deeper 25 75 m than aluminum maxima and located in the lower euc which undergoes less interior ocean mixing than shallower waters the depth of the aluminum subsurface maxima correlated strongly r 0 88 with the depth of the euc velocity maximum surface waters were enriched in aluminum and manganese offshore of papua new guinea surface metal concentrations decreased eastward throughout the western warm pool up to the longitude 180 w of the salinity front detrital sediment input from either direct riverine input or sediment resuspension appeared to be the primary mechanism of supplying metals to the ngcu we estimated eastward fluxes of metals in the euc and found greatest fluxes in the western equatorial pacific between 160 e and 165 e except for aluminum fluxes of aluminum and to a lesser extent manganese increased concurrently with water volume transport in the central equatorial pacific iron transport in the euc remained constant east of the dateline apparently due to the combined effects of dilution by meridional entrainment and scavenging iron was mobilized in a highly active western boundary current region and transported eastward in the lower euc

do geochemical estimates of sediment focusing pass the sediment test in the equatorial pacific 1 the paleoceanographic recording fidelity of pelagic sediments is limited by chemical diagenesis and physical mixing bioturbation and horizontal sediment transport diagenesis and bioturbation are relatively well studied but the effects of physical sedimentation have been largely ignored modeling u series isotopes e g 230th can potentially quantify horizontal sediment movement but model horizontal sediment focusing often equals or exceeds the vertical particle rain we find no evidence of this level of sediment focusing in the equatorial pacific from geophysical data or sediment core comparisons the overestimate of sediment focusing by 230th is probably caused by poor model assumptions that sediment does not fractionate does not sort according to size during transport and that 230th cannot leak from slowly accumulating sediments both assumptions are weak u series methods do hold promise to quantify sediment focusing if properly calibrated with calibration the trade offs between seeking high sedimentation rates for better time resolution and the blurring by horizontal sediment focusing can be better assessed

what do benthic δ13c and δ18o data tell us about atlantic circulation during heinrich stadial 1 approximately synchronous with the onset of heinrich stadial 1 hs1 13c decreased throughout most of the upper 1000 2500 m atlantic and at some deeper north atlantic sites this early deglacial 13c decrease has been alternatively attributed to a reduced fraction of high 13c north atlantic deep water nadw or to a decrease in the nadw 13c source value here we present new benthic 18o and 13c records from three relatively shallow 1450 1650 m subpolar northeast atlantic cores with published data from other cores these data form a depth transect 1200 3900 m in the subpolar northeast atlantic we compare last glacial maximum lgm and hs1 data from this transect with data from a depth transect of cores from the brazil margin the largest lgm to hs1 decreases in both benthic 13c and 18o occurred in upper waters containing the highest nadw fraction during the lgm we show that the 13c decrease can be explained entirely by a lower nadw 13c source value entirely by a decrease in the proportion of nadw relative to southern ocean water or by a combination of these mechanisms however building on insights from model simulations we hypothesize that reduced ventilation due to a weakened but still active atlantic meridional overturning circulation also contributed to the low 13c values in the upper north atlantic we suggest that the benthic 18o gradients above 2300 m at both core transects indicate the depth to which heat and north atlantic deglacial freshwater had mixed into the subsurface ocean by early hs1

holocene glacier and climate fluctuations of the maritime ice cap hogtuvbreen northern norway holocene fluctuations of a small outlet glacier from the ice cap hogtuvbreen at 65 n in coastal northern norway are reconstructed based on distal glacier fed lake sediments complemented by a moraine sequence dated by lichenometry glaciers respond to changes in accumulation season precipitation ablation season temperature and redistribution of snow by wind hence reconstructions of glacier fluctuations based on distal glacier fed lakes may give detailed information about past climate at a potentially high temporal resolution yet the importance of any of these climate components is often difficult to solve here we apply the liestol relationship which expresses the relationship between ablation season temperature and annual accumulation of snow at the equilibrium line altitude ela to the reconstructed local temperature precipitation wind ela tpw ela to infer the relative importance of winter balance and ablation season temperature as causes of reconstructed glacier variation the reconstruct

the response of the walker circulation to last glacial maximum forcing implications for detection in proxies 1 the response of the walker circulation to last glacial maximum lgm forcing is analyzed using an ensemble of six coordinated coupled climate model experiments the tropical atmospheric overturning circulation strengthens in all models in a manner that is dictated by the response of the hydrological cycle to tropical cooling this response arises from the same mechanism that has been found to explain the weakening of the tropical circulation in response to anthropogenic global warming but with opposite sign analysis of the model differences shows that the ascending branch of the walker circulation strengthens via this mechanism but vertical motion also weakens over areas of the maritime continent exposed due to lower sea level each model exhibits a different balance between these two mechanisms and the result is a pacific walker circulation response that is not robust further even those models that simulate a stronger walker circulation during the lgm do not simulate clear patterns of surface cooling such as la nina like cooling or enhanced equatorial cooling as proposed by previous studies in contrast the changes in the walker circulation have a robust and distinctive signature on the tilt of the equatorial thermocline as expected from zonal momentum balance the changes in the walker circulation also have a clear signature on the spatial pattern of the precipitation changes a reduction of the east west salinity contrast in the indian ocean is related to the precipitation changes resulting from a weakening of the indian walker circulation these results indicate that proxies of thermocline depth and sea surface salinity can be used to detect actual lgm changes in the pacific and indian walker circulations respectively and help to constrain the sensitivity of the walker circulation to tropical cooling

a new interpretation of the date of the little ice age glacier maximum at svartisen and okstindan northern norway new results concerning the dating of little ice age glacier variations at svartisen and okstindan northern norway are presented measurements of lichens of the rhizocarpon subgenus on gravestones are used to construct several local sets of lichenometric dating curves these are partly adjusted in relation to well established lichenometric dating curves from southern norway the little ice age maximum at svartisen and okstindan is thereby dated to the mid eighteenth century i e in agreement with southern norway pre viously suggested earlier little ice age advances are demonstrated to have resulted from an underestimation of the growth rates of the rhizocarpon subgenus synchroneity of little ice age maxima in southern norway and at svartisen and okstindan suggest that a north south migration of latitudinal depressional tracks can be excluded as the main forcing factor as an alternative an increased se nw trend of moist air ow in winter parallel to the coast of norway is suggested as the

el nino southern oscillation like variability during glacial terminations and interlatitudinal teleconnections interannual decadal variability in the equatorial pacific el nino southern oscillation enso induces climate changes at global scale but its potential influence during past global climate change is not yet well constrained new high resolution eastern equatorial pacific proxy records of thermocline conditions present new evidence of strong orbital control in enso like variability over the last 275 000 years recurrent intervals of saltier thermocline waters are associated with the dominance of la nina like conditions during glacial terminations coinciding with periods of low precession and high obliquity the parallel dominance of 13c depleted waters supports the advection of antarctic origin waters toward the tropical thermocline this oceanic tunneling is proposed to have reinforced orbitally induced changes in enso like variability composing a complex high and low latitude feedback during glacial terminations

sedimentary opal records in the eastern equatorial pacific it is not all about leakage 1 the clear predictions of the silicic acid leakage hypothesis salh resulted in a number of studies of downcore opal records from the tropical pacific the original salh predicts that unused silicic acid due to fe driven changes in si versus n limitation escaped from the glacial southern ocean to equatorial upwelling regimes where it enhanced diatom productivity thereby decreasing coccolith growth and lowering atmospheric co2 in contrast to salh predictions however sedimentary records from the eastern equatorial pacific eep do not show enhanced opal burial during the last glacial maximum lgm but higher rates of opal burial during the deglaciation and marine isotopic stage 3 mis3 the peak in opal productivity during the deglaciation has been attributed to increased supply of nutrient rich waters driven by stronger upwelling of deep water in the southern ocean at the end of last glacial period the large peak in opal burial observed in a number of eep cores during mis3 was interpreted as evidence for si leakage when southern ocean diatom productivity was limited by both low dust flux and extended sea ice on the other hand the paradoxical lgm decline in opal accumulation in the eep was explained by enhanced dust input that lowered the diatom si c uptake ratio here we use a combination of molecular fingerprints of algal productivity and radioisotope tracers of sedimentation to revisit opal burial in the eep in particular during the mis3 opal peak an increase in algal productivity is not supported by the sedimentary concentration of brassicasterol an organic molecule commonly found in diatoms or by the ratio of 231pa 230th xs 0 a proxy for opal export production we therefore conclude that the large peak in opal burial during mis3 reflects enhanced preservation of diatoms building on mechanisms invoked in previous studies we hypothesize that opal burial in the eep is controlled both by the physiological response of diatoms to low latitude fe inputs and by the high latitude processes leading to silicic acid leakage

progressive shoaling of the equatorial pacific thermocline over the last eight glacial periods the depth of equatorial pacific thermocline is diagnostic of the main modes of tropical climates past estimates of pacific thermocline dynamics have been reconstructed either for the last glacial maximum or on longer timescales at low resolution here we document a new high resolution set of reconstructed past sea surface and subsurface waters temperatures from the southwestern subequatorial pacific core md05 2930 in the gulf of papua over the last 800 ka we used two morphotypes of globigerinoides ruber known to live at different water depths to reconstruct past stratification we estimated calcification temperature of each morphotypes by mg ca paleothermometry our subequatorial pacific thermocline paleotemperature record indicates a response of the thermocline to both direct orbital forcing and glacial interglacial changes our stratification record shows a systematic shallower glacial thermocline whereas sea surface temperatures are characterized by precessional forcing the record is indicative of a progressive long term shoaling of the thermocline during the glacial stages during the late pleistocene the shoaling of the subequatorial pacific thermocline is consistent with regional estimates an enhanced south pacific shallow overturning wind driven circulation could have driven this progressive shoaling we speculate that this late pleistocene glacial shoaling of the thermocline could be related to an increase in the amplitude of the obliquity

the temporal significance of transitions from melting to calving termini at glaciers in the central southern alps of new zealand termini of valley glaciers in the central southern alps are undergoing a three phase sequence of retreat that began in the 1950s an initial phase of melting and slow downwasting under thickening supraglacial debris mantles is associated with stationary or slowly retreating termini this is followed by a transitional phase of disruption of insulating debris mantles allowing the rapid growth of shallow thermokarst lakes the shape and location of which vary according to glacier gradient and marginal topography a third phase of rapid calving retreat of ice cliffs into deepening proglacial lakes develops from the transitional phase at no stage are terminal responses simply related to climate present transitions to calving retreat are related to the morphology of glacier termini particularly to large outwash heads landform evidence indicates that similar calving phases do not appear to have occurred since late pleistocene deglaciation so that present changes to glacier termini are of great significance

lower export production during glacial periods in the equatorial pacific derived from 231pa 230th xs 0 measurements in deep sea sediments 1 the 231pa 230th xs 0 records obtained from two cores from the western md97 2138 1 25 s 146 24 e 1900 m and eastern ocean drilling program leg 138 site 849 0 11 59 n 110 31 18 w 3851 m equatorial pacific display similar variability over the last 85 000 years i e from isotopic stages 1 to 5a with systematically higher values during the holocene isotopic stage 3 and isotopic stage 5a and lower values approaching the production rate ratio of the two isotopes 0 093 during the colder periods corresponding to isotopic stages 2 and 4 we have also measured the 230th normalized biogenic preserved and terrigenous fluxes as well as major and trace elements concentrations in both cores the 231pa 230th xs 0 results combined with the changes in preserved carbonate and opal fluxes at the eastern site indicate lower productivity in the eastern equatorial pacific during glacial periods the 231pa 230th xs 0 variations in the western equatorial pacific also seem to be controlled by productivity carbonate and or opal the generally high 231pa 230th xs 0 ratios 0 093 of the profile could be due to opal and or mno2 in the sinking particles the profiles of 231pa 230th xs 0 and 230th normalized fluxes indicate a decrease in exported carbonate and possibly opal during isotopic stages 2 and 4 in md97 2138 using 230th normalized flux we also show that sediments from the two cores were strongly affected by sediment redistribution by bottom currents suggesting a control of mass accumulation rates by sediment focusing variability

long term variations of the seasonal snow cover in nordland norway the influence of the north atlantic oscillation temporal and spatial variations of the seasonal snow cover at 40 sites in nordland county norway which lies across the arctic circle are examined since the last decade of the 19th century annual maximum snow depths have varied reflecting the interaction of synoptic conditions temperature and terrain north south and coastal inland differences are evident but common temporal trends are identified maximum snow depths are strongly related to the winter north atlantic oscillation index early in the 20th century the index was positive and the associated stormy conditions resulted in a deep prolonged snow cover as the index declined in the 1920s snow depths decreased sharply through much of the second half of the 20th century they increased as the index tended to become more positive the start and duration of the period of continuous snow cover is influenced by the autumn nao index a decrease of duration around 1990 was particularly evident at low lying stations and those in the northern part of nordland the nao has varied considerably over the past 120 years because of its influence forecasting future trends of snow depth and snow cover duration is not a simple task

an inverse approach to the course of the little ice age glacier advance and the following deglaciation at austerdalsisen eastern svartisen northern norway the course of the little ice age lia in scandinavia is characterized by large glacier advances that started at about ad 1300 and culminated at about ad 1750 the end of the lia is marked as an unprecedented and ongoing glacier retreat that accelerated from the early 20th century the course of the lia is here presented based on fluctuations of austerdalsisen the largest valley outlet glacier draining the austre svartisen ostisen ice cap nordland northern norway during the lia glacierization austerdalsisen separated into two branches and relative to the present glacier terminus a western valley glacier advanced more than 4 km whereas a se valley glacier advanced about 3 km at present meltwater from austerdalsisen drains towards se if the glacier obtains a critical magnitude however most of the meltwater is drained westwards across a higher overflow gap based on radiocarbon dated lake sediments distal proglacial glaciolacustrine glaciofluvial sediments and historical observations the c

the lower marine to lower freshwater molasse transition in the northern alpine foreland basin oligocene central switzerland south germany age and geodynamic implications the wilhelmine alpe section near immenstadt allgau south germany which represents one of the best continuously exposed outcrops within the northern alpine foreland basin has been analyzed for magnetostratigraphic and palynostratigraphic signals the section comprises the marine to terrestrial transition from lower marine umm to lower freshwater molasse usm sediments based on the correlation of the local magnetic pattern with the geomagnetic polarity timescale gpts and palynostratigraphic data an age of about 31 ma is suggested for the umm usm transition in the wilhelmine alpe section a comparison with coeval magnetostratigraphic sections from central and eastern switzerland indicates that the regression of the umm sea along the southern margin of the molasse basin occurred strongly heterochronously between 31 5 and 30 ma the heterochroneity is attributed to the deposition of fan delta and alluvial fan sediments which document that the overall marine conditions during the umm were accompanied by strong clastic input derived from the rising alps this clastic contribution had a much stronger influence on the depositional pattern than previously thought

thorium 230 normalized particle flux and sediment focusing in the panama basin region during the last 30 000 years 1 application of the 230 th normalization method to estimate sediment burial fluxes in six cores from the eastern equatorial pacific eep reveals that bulk sediment and organic carbon fluxes display a coherent regional pattern during the holocene that is consistent with modern oceanographic conditions in contrast with estimates of bulk mass accumulation rates mars derived from core chronologies two nearby sites less than 10 km apart which have different mars show nearly identical 230 th normalized bulk fluxes focusing factors derived from the 230 th data at the foot of the carnegie ridge in the panama basin are 2 in the holocene implying that lateral sediment addition is significant in this part of the basin new geochemical data and existing literature provide evidence for a hydrothermal source of sediment in the southern part of the panama basin and for downslope transport from the top of the carnegie ridge the compilation of core records suggests that sediment focusing is spatially and temporally variable in the eep during oxygen isotope stage 2 ois 2 from 13 27 ka bp focusing appears even higher compared to the holocene at most sites similar to earlier findings in the eastern and central equatorial pacific the magnitude of the glacial increase in focusing factors however is strongly dependent on the accuracy of age models we offer two possible explanations for the increase in glacial focusing compared to the holocene the first one is that the apparent increase in lateral sediment redistribution is partly or even largely an artifact of insufficient age control in the eep while the second explanation which assumes that the observed increase is real involves enhanced deep sea tidal current flow during periods of low sea level stand

coupled nitrate nitrogen and oxygen isotopes and organic matter remineralization in the southern and pacific oceans 1 the difference between nitrate 15n and 18o or 15 18 is sensitive to organic matter remineralization and tracks the modification of nitrate as it passes from the deep pacific ocean through the southern ocean surface and into the intermediate depth pacific circumpolar deep water cdw is upwelled with a nitrate 15 18 of 3 0 and appears unaltered by nitrate assimilation in the antarctic surface however within subantarctic mode water samw the primary conduit of deep sea nutrients to the lower latitudes nitrate 15n and 18o are both higher than cdw while nitrate 15 18 is as low as 1 5 the lower samw nitrate 15 18 results from the production of low 15n organic matter during partial assimilation of the surface nitrate pool followed by its sinking and remineralization back to nitrate lowering the 15n of thermocline nitrate more than its 18o as samw flows toward the lower latitudes nitrate 15 18 is expected and observed to increase because complete surface ocean nitrate consumption produces sinking nitrogen with a 15n similar to that of the nitrate supplied from below such that remineralization lowers the 18o of nitrate but not its 15n nitrate 15 18 is also used to estimate a surprisingly high low latitude sinking nitrogen 15n of 9 0 suggesting a major effect of 14no3 loss by tropical denitrification on middepth nitrate basin wide the remineralization of this high sinking nitrogen 15n increases nitrate 15 18 as deep as the southward moving pacific deep water which supplies cdw this relatively high 15 18 is then lowered to the observed cdw value by the remineralization of southern ocean sinking nitrogen with a low 15n

productivity patterns in the equatorial pacific over the last 30 000 years the equatorial pacific traverses a number of productivity regimes from the highly productive coastal upwelling along peru to the near gyre like productivity lows along the international dateline making it an ideal target for investigating how biogeochemical systems respond to changing oceanographic conditions over time however conflicting reconstructions of productivity during periods of rapid climate change like the last deglaciation render the spatiotemporal response of equatorial pacific productivity ambiguous in this study surface productivity since the last glacial period 30 000 years ago is reconstructed from seven cores near the line islands central equatorial pacific and integrated with productivity records from across the equatorial pacific three coherent deglacial patterns in productivity are identified 1 a monotonic glacial holocene increase in productivity primarily along the equator associated with increasing nutrient concentrations over time 2 a deglacial peak in productivity 15 000 years ago due to transient entrainment of nutrient rich southern sourced deep waters and 3 possible precessional cycles in productivity in the eastern equatorial pacific that may be related to intertropical convergence zone migration and potential interactions with el nino southern oscillation dynamics these findings suggest that productivity was generally lower during the glacial period a trend observed zonally across the equatorial pacific while deglacial peaks in productivity may be prominent only in the east

environmental versus biological controls on mg ca variability in globigerinoides ruber white from core top and plankton tow samples in the southwest pacific ocean 1 laser ablation inductively coupled plasma mass spectrometry was used to analyze the individual chambers from tests of foraminiferal fossil and plankton tow globigerinoides ruber from the southwest pacific ocean from latitudes 3 s to 42 s the variability of mg ca between chambers of an individual intraindividual and individuals of the same population interindividual is such that when converted to temperature the extent of intra individual and interindividual variability appears to exceed that attributable to either calcification or seasonal temperature variability the pooled mean chamber mg ca from each core top and plankton tow site demonstrates a significant p 0 05 positive correlation with temperature we derive chamber specific calibrations where mg cach f 2 0 798 exp0 070 t mg cach f 1 0 891 exp0 067 t and mg cach f 0 590 exp0 072 t we do not observe any bias between the two morphotypes gs ruber ruber and gs ruber pyramidalis the chamber specific calibrations potentially offset mg ca based temperature reconstructions if used on bulk whole test mg ca or applied to misidentified chambers nevertheless these calibrations can be used to reliably estimate sea surface temperature although there is a general overriding temperature control on mg ca we show that removal of the effect of temperature at each site reveals a lognormal mg ca distribution this suggests that mg ca variability at each site is also affected by biological mechanism s that may control the distribution of interindividual mg ca in addition other te ca data al ca and mn ca from laser ablation trace element depth profiles can be used to identify detrital or diagenetic phases that may bias the trace element ca signal

an 1899 glacier inventory for nordland northern norway produced from historical maps glaciers depicted on old maps reveal their historical extents before the advent of aerial and satellite remote sensing digital glacier inventories produced from these maps can be employed in assessments of centennial scale glacier change this study reconstructs the 1899 covering the period 1882 1916 glacier extent in nordland northern norway from historical gradteigskart maps with an emphasis on examining the accuracy of the mapped glaciers glacier outlines were digitised from georectified scans of the analogue maps in a raster graphics editor and were subsequently inventoried in a gis the accuracy of the historical glacier extent was established from written descriptions and landscape photographs created during the original field surveys and further validated against independent glacier outlines of 1 the maximum little ice age extent derived from geomorphological evidence and 2 the 1945 extent derived from vertical aerial photographs an overall uncertainty of 17 is associated with our inventory nordland s glaciers covered an area of 1712 291 km2 in 1899 by 2000 total ice cover had decreased by 47 807 137 km2 at a rate of 6 10 a 1 80 14 km2 10 a 1 the approach presented here may serve as a blueprint for future studies intending to derive glacier inventories from historical maps