fertilizing potential of volcanic ash in ocean surface water the fertilization potential of newly erupted and well preserved ash from the 2000 hekla eruption in iceland was measured for the first time by flow through experiments as previously shown 1 the north atlantic ocean including the subarctic seas surrounding iceland is the largest net sink of the world s oceans for atmospheric co 2 owing to biological drawdown during summer 2 almost complete consumption of phosphate in chlorophyll rich areas of the north atlantic ocean might limit primary production and 3 in the southern pacific ocean and parts of the equatorial pacific ocean iron might limit primary production we found through laboratory experiments that volcanic ash exposed to seawater initially releases large amounts of adsorbed phosphate 1 7 mmol g 21 h 21 iron 37 0 mmol g 21 h 21 silica 49 5 mmol g 21 h 21 and manganese 1 7 mmol g 21 h 21 dissolution of acid aerosols adsorbed to the surface of the ash caused the high initial release of major and trace elements because of the instantaneous dissolution of adsorbed components when newly erupted volcanic ash comes in contact with the ocean surface water macronutrients and bioactive trace metals are released fast enough to become available to support primary production

seasonal variation of counterclockwise eddies downstream of the tsushima islands abstract the seasonal variation of counterclockwise eddies downstream of the tsushima islands in the tsushima straits was investigated from 2004 to 2008 using long term acoustic doppler current profiler adcp data eddy activity was high from summer to autumn july november the eddies were formed in short term intervals of 5 8 days almost corresponding to the formation cycle of karman vortices the eddy activity varied on a longer time period about 13 days the mean kinetic energy mke converted to eddy kinetic energy eke at current shears between the eastern and western channels of the tsushima straits the counterclockwise eddies that formed downstream of the tsushima islands were intensified and maintained by energy conversion from mke to eke at the northern shear of the current core in the eastern channel the countercurrent east of the tsushima islands from summer to autumn was intensified by energy conversion from eke to mke

short term flow and water temperature fluctuations in sagami bay japan associated with variations of the kuroshio during the non large meander path abstract short term flow and water temperature fluctuations in sagami bay were examined using mooring and hydrographic data observed during the non large meander path nlm of the kuroshio in the surface layer 1 in the central part of the bay this flow is a part of an intrusion of kuroshio water via the oshima west channel into the bay and or a cyclonic circulation in the northern part of the bay the cyclonic circulation which is approximately balanced under the geostrophic flow relationship is mainly generated or enhanced by the intrusion which is accompanied by eastward propagation of the small meander of the kuroshio south of japan during the transition from the nearshore non large meander path nnlm to the offshore non large meander path onlm regardless of season the water temperature fluctuation in the subsurface layer 150 m is caused by upwelling of cold deeper water and is closely related to the eastward flow fluctuations in the surface layer in the central part of the bay our analysis leads us the conclusion that the upwelling occurs as the response of the subsurface density field to the surface flow field under the earth s rotation additionally the intrusion of kuroshio water via the oshima west channel tends to cause not only cyclonic circulation and upwelling in the northern part of the bay but also the kyucho which is the coastal density current under the earth s rotation in the bay s coastal area during the non large meander path nlm

a simulation of temperature influence on echolocation click beams of the indo pacific humpback dolphin sousa chinensis a finite element method was used to investigate the temperature influence on sound beams of the indo pacific humpback dolphin the numerical models of a dolphin which originated from previous computed tomography ct scanning and physical measurement results were used to investigate sound beam patterns of the dolphin in temperatures from 21 c to 39 c in increments of 2 c the 3 db beam widths across the temperatures ranged from 9 3 to 12 6 and main beam angle ranged from 4 7 to 7 2 for these temperatures the subsequent simulation suggested that the dolphin s sound beam patterns side lobes in particular were influenced by temperature

a comparison between the world ocean atlas and hydrobase climatology the gridded 1 4 world ocean atlas woa boyer and levitus 1998 is compared with the 1 woa levitus et al 1994 over the north atlantic ocean the temperature and salinity fields from both the 1 4 and 1 woa are projected on two isopycnal surfaces and compared with the hydrobase climatology lozier et al 1995 geostrophic current maps diagnosed from hydrographic temperature and salinity are also presented results show that the 1 4 woa with a smaller smoothing radius greatly improves the 1 woa in several important aspects in particular sharp frontal features associated with the western boundary current which are absent in the 1 woa are apparent in the 1 4 woa the 1 4 woa describes similar small scale mid depth recirculation gyres reported by lozier 1997 based on hydrobase however artifacts in the property fields created by the isobaric averaging are still evident in the 1 4 woa

provenance and transport of terrigenous sediment in the south atlantic ocean and their relations to glacial and interglacial cycles nd and sr isotopic evidence sr and nd isotopic compositions of late quaternary surface sediment and sediment cores from the south atlantic and southeast pacific sectors of the southern ocean are used to constrain the provenance and transport mechanisms of their terrigenous component we report isotopic and mineralogical data for core samples from three localities the mid atlantic ridge at 41 s and the northern and southern scotia sea in addition data for surface sediment samples from the south atlantic and southeast pacific sectors of the southern ocean are presented the variations of sr and nd isotopic compositions of the bulk sediment samples in all cores were correlated with the magnetic susceptibility of the sediment and with the inferred glacial interglacial stages the isotopic data indicate that during glacial periods sediment was delivered from continental crust with a shorter residence time than that supplying material during interglacial periods at the core site near the mid atlantic ridge nd isotopic combined with mineralogical evidence indicates interglacial period deposition of a relatively high amount of kaolinite and silt with low nd values 4 5 probably derived from southern south america was indicated the glacial interglacial shift in sources may be due to either a decreasing influence of north atlantic deep water during glacial times or by a larger contribution of glaciogenic detritus from southern south america at the core site in the northern scotia sea sediment of interglacial periods is dominated by smectite with nd 4 we suggest that smectite was derived from the falkland shelf and silt was derived from the argentinian shelf during glacial periods the argentinian shelf was an important source for silt and chlorite with nd 4 the contribution from the falkland shelf seems to have remained similar during glacial and interglacial periods hydrographic transport by bottom currents and turbidites could account for the high glacial detrital flux an evaluation of the significance of an aeolian contribution to deep sea sediment suggests that it plays only a minor role in the southern scotia sea the antarctic peninsula is considered an important source for young material with nd 4 in particular during glacial periods during interglacial periods sediment supply from the antarctic peninsula was lower than during glacial times resulting in a relatively high contribution of old material nd 8 from east antarctica deep water currents and icebergs could account for the transport of the old component to the southern scotia sea the accumulation rates of material from the various source regions for glacial times are in agreement with an increase in the strength of the antarctic circumpolar current the production rate and the circulation pattern of bottom water in the weddell sea appear to have remained similar over most of the last 150 kyr

an ice core indicator of antarctic sea ice production 1 the sea ice surface not open water is the dominant source of sea salt to aerosol and ice cores in coastal antarctica here we show that it may also form the dominant source for central antarctica we can then explain higher concentrations in the winter and last glacial maximum lgm as being due to increased sea ice production this suggests that ice core sea salt can indicate at least the timing of changes in antarctic sea ice production the pattern of sea salt in ice cores is consistent with marine evidence about sea ice changes in the holocene and lgm sea salt shows no change at the initial co2 increase out of the last glacial making it unlikely this was primarily due to changing sea ice cover the sea salt record should not be treated as an indicator of meridional transport

patagonian and southern south atlantic view of holocene climate abstract we present a comprehensive 10be chronology for holocene moraines in the lago argentino basin on the east side of the south patagonian icefield we focus on three different areas where prior studies show ample glacier moraine records exist because they were formed by outlet glaciers sensitive to climate change the 10be dated records are from the lago pearson herminita peninsula brazo upsala and lago frias areas which span a distance of almost 100 km adjacent to the modern icefield new 10be ages show that expanded glaciers and moraine building events occurred at least at 6120 390 n 13 4450 220 n 7 1450 or 1410 110 n 18 360 30 n 5 and 240 20 n 8 years ago furthermore other less well dated glacier expansions of the upsala glacier occurred between 1400 and 1000 and 2300 and 2000 years ago the most extensive glaciers occurred over the interval from 6100 to 4500 years ago and their margins over the last 600 years were well within and lower than those in the middle holocene the 10be ages agree with 14c limiting data for the glacier histories in this area we then link southern south american adjacent south atlantic and other southern hemisphere records to elucidate broader regional patterns of climate and their possible causes in the early holocene a far southward position of the westerly winds fostered warmth small patagonian glaciers and reduced sea ice coverage over the south atlantic although we infer a pronounced southward displacement of the westerlies during the early holocene these conditions did not occur throughout the southern mid high latitudes an important exception being over the southwest pacific sector subsequently a northward locus and or expansion of the winds over the patagonia south atlantic sector promoted the largest glaciers between 6100 and 4500 years ago and greatest sea ice coverage over the last few millennia the south patagonian icefield has experienced successive century scale advances superimposed on a long term net decrease in size our findings indicate that glaciers and sea ice in the patagonian south atlantic sector of the southern hemisphere did not achieve their largest holocene extents over the last millennium we conclude that a pattern of more extensive holocene ice prior to the last millennium is characteristic of the southern hemisphere middle latitudes which differs from the glacier history traditionally thought for the northern hemisphere

reduced north atlantic deep water flux to the glacial southern ocean inferred from neodymium isotope ratios the global circulation of the oceans and the atmosphere transports heat around the earth broecker and denton1 suggested that changes in the global ocean circulation might have triggered or enhanced the glacial interglacial cycles but proxy data for past circulation taken from sediment cores in the south atlantic ocean have yielded conflicting interpretations of ocean circulation in glacial times 13c variations in benthic foraminifera2 3 4 5 6 support the idea of a glacial weakening or shutdown of north atlantic deep water production whereas other proxies such as cd ca ba ca and 231pa 230th ratios show little change from the last glacial maximum to the holocene epoch7 8 9 here we report neodymium isotope ratios from the dispersed fe mn oxide component of two southeast atlantic sediment cores both cores show variations that tend towards north atlantic signatures during the warm marine isotope stages 1 and 3 whereas for the full glacial stages 2 and 4 they are closer to pacific ocean signatures we conclude that the export of north atlantic deep water to the southern ocean has resembled present day conditions during the warm climate intervals but was reduced during the cold stages an increase in biological productivity may explain the various proxy data during the times of reduced north atlantic deep water export

millennial scale variability in antarctic ice sheet discharge during the last deglaciation two well dated high resolution records of iceberg rafted debris are presented that document variability in antarctic ice sheet discharge during the last deglaciation global sea levels have risen by more than 100 metres since the last glacial maximum around 20 000 years ago with several meltwater pulses of several metres or more in the most dramatic of these meltwater pulse 1a sea level rose by about 16 metres at 14 600 years ago this magnitude of sea level rise strongly suggests major antarctica contributions but to date there has been no firm physical evidence now michael weber and colleagues present a record of iceberg rafted debris from the scotia sea and show clear signals of pulsed iceberg release from antarctica as early as 19 000 years ago the largest iceberg release occurred during meltwater pulse 1a providing the long sought confirmation of antarctic contributions to this major jump in sea level rise our understanding of the deglacial evolution of the antarctic ice sheet ais following the last glacial maximum 26 000 19 000 years ago 1 is based largely on a few well dated but temporally and geographically restricted terrestrial and shallow marine sequences2 3 4 this sparseness limits our understanding of the dominant feedbacks between the ais southern hemisphere climate and global sea level marine records of iceberg rafted debris ibrd provide a nearly continuous signal of ice sheet dynamics and variability ibrd records from the north atlantic ocean have been widely used to reconstruct variability in northern hemisphere ice sheets5 but comparable records from the southern ocean of the ais are lacking because of the low resolution and large dating uncertainties in existing sediment cores here we present two well dated high resolution ibrd records that capture a spatially integrated signal of ais variability during the last deglaciation we document eight events of increased iceberg flux from various parts of the ais between 20 000 and 9 000 years ago in marked contrast to previous scenarios which identified the main ais retreat as occurring after meltwater pulse 1a3 6 7 8 and continuing into the late holocene epoch the highest ibrd flux occurred 14 600 years ago providing the first direct evidence for an antarctic contribution to meltwater pulse 1a climate model simulations with ais freshwater forcing identify a positive feedback between poleward transport of circumpolar deep water subsurface warming and ais melt suggesting that small perturbations to the ice sheet can be substantially enhanced providing a possible mechanism for rapid sea level rise

the impact of icebergs of sub antarctic origin on southern ocean ice rafted debris distributions abstract the presence of widespread terrigenous material of an ice rafted origin in quaternary sediments of the southern ocean has been recognized for almost 150 years normally this material has been ascribed to deposits from icebergs of continental antarctic origin however during quaternary glaciations there have been periods of extensive land ice across the sub antarctic on both islands scattered around most of the circumpolar extent of the southern ocean as well as in patagonia so providing alternative sources for debris carrying icebergs here a relatively high resolution ocean and iceberg model is used to study the potential distribution of ice rafted debris ird from the range of past ice sources around the southern ocean it is shown that ird found in marine cores of the southern ocean is most likely to have derived from the antarctic continent in some regions particularly of the south atlantic but that for extensive regions of the southern ocean sub antarctic sources of ird rather than the continent itself are more likely this is particularly true equatorward of 55os away from the core continental iceberg outflow from the weddell gyre it is argued that the glaciated sub antarctic cannot be neglected in explaining past ird records in the southern ocean this has implications not just for reconstructing the history of glaciation in the sub antarctic but also for understanding past variation in the upper ocean circulation within the quaternary southern ocean

greater supply of patagonian sourced detritus and transport by the acc to the atlantic sector of the southern ocean during the last glacial period reconstructing past detrital flux and provenance in the southernocean provides information about changes in source regions associated with climate variations and transport pathways we present a lastglacial maximum lgm to holocene comparison of 230th normalised fluxes combined with sediment provenance data pb nd and sr isotopes from a latitudinal core transect in the eastern atlanticsector of the southernocean odp leg 177 cores we compare the radiogenic isotopic composition ic of detritus in these cores to that of cores proximal to potential source areas we observe a well defined latitudinal holocene gradient in both detrital flux and provenance of sediment high detrital fluxes in the north are associated with terrigenous material derived from southern africa while low detrital fluxes in the south are associated with supply from southern south america west antarctica and the south sandwich islands the data suggest that this well defined holocene gradient in detrital flux and sediment provenance is controlled by the flow of the antarctic circumpolar current acc and the position of its frontal zones the lgm is characterised by 2 to 6 times higher than modern detrital fluxes at most odp leg 177 sites the lgm detrital fluxes do not show a latitudinal trend and suggest a greatersupply of glaciogenic detritussourced from southern south america glacialpatagonian outwash sediments 5 m fraction were analysed and compared to the bulk compositions of the marine sediments the pb ic of the patagonian sediments is very similar to the glacial ic of sediments in the scotia sea and at 49 s latitude in the eastern atlanticsector we propose that the glacial ic of sediments is controlled by increased delivery of patagoniandetritus initially supplied by glaciers and then transported at depth via the acc

dust transport from patagonia to antarctica a new stratigraphic approach from the scotia sea and its implications for the last glacial cycle abstract we studied two deep sea cores from the scotia sea to reconstruct past atmospheric circulation in the southern hemisphere and to resolve a long standing debate on the interpretation of magnetic susceptibility ms records in southern ocean so sediment high sedimentation sites md07 3134 0 2 1 2 m kyr and md07 3133 0 3 2 1 m kyr cover the last 92 5 kyr and 36 kyr respectively both exhibit a one to one coupling of the ms and ca2 signal to the non sea salt nss ca2 signal of the edml ice core clearly identifying atmospheric circulation as means of distribution comparison of additional proxies also excludes major influence by volcanic sources sea ice icebergs or oceanic current transport the close resemblance of the dust proxies over the last glacial cycle in turn allows for the establishment of an age model of unprecedented resolution and precision for so deep sea sediment because atmospheric transport involves no major leads or lags this is of particular importance because ms is routinely measured on deep sea cores in the so but the sediments usually lack biogenic carbonate and therefore had only limited stratigraphic control so far southern south america ssa is the likely source of eolian material because site md07 3133 located closer to the continent has slightly higher ms values than site md07 3134 and also the ms record of patagonian site salsa shows comparable variability patagonia was the dust source for both the scotia sea and east antarctica dust fluxes were several times higher during glacial times when atmospheric circulation was either stronger or shifted in latitude sea level was lowered shelf surfaces were exposed and environmental conditions in ssa were dominated by glaciers and extended outwash plains hence ms records of so deep sea sediment are reliable tracers of atmospheric circulation allowing for chronologically constrained reconstructions of the circum antarctic paleoclimate history

volcanic layers in antarctic vostok ice cores source identification and atmospheric implications fifteen visible volcanic ash layers tephra from vostok ice cores have been analyzed for major elements trace elements and sr and nd isotope composition comparison of their geochemical signatures to lava composition from the inventory of antarctic and subantarctic volcanoes which have been active over the last 0 5 million years indicates that nine layers originate from activity of the south sandwich volcanic arc three from southern south america one from the antarctic peninsula bransfield strait and one from west antarctica marie byrd land province the large size of the tephra up to 50 m requires rapid atmospheric transfer from the volcanic centers to east antarctica rapid tropospheric transport from the southwestern atlantic penetrating east antarctica therefore predominates during the period studied whether in glacial or interglacial climatic mode in spite of the low frequency of occurrence of visible tephra layers in vostok core one event every 20 kyr the overall atmospheric pathway of these ash events appears consistent with the almost continuous advection of continental dust from south america

echolocation transmitting beam of the atlantic bottlenose dolphin the transmitting beam patterns of echolocation signals emitted by an atlantic bottlenose dolphin tursiops truncatus were measured in the vertical and horizontal planes with an array of seven hydrophones particular emphasis was placed on accurately verifying the animal s position on a bite plate tail rest stationing device using underwater video monitoring equipment the major axis of the vertical beam was directed at an angle of 5 above the plane defined by the animal s lips this angle was 15 lower than previously measured the vertical beam measurements indicate that the major axis of the transmitting beam is aligned with the major axis of the receiving beam the horizontal beam was directed forward the directivity index of 26 5 db calculated from the beam pattern measured in both planes agreed well with previous calculation of 25 4 db

off axis sonar beam pattern of free ranging finless porpoises measured by a stereo pulse event data logger the off axis sonar beam patterns of eight free ranging finless porpoises were measured using attached data logger systems the transmitted sound pressure level at each beam angle was calculated from the animal s body angle the water surface echo level and the swimming depth the beam pattern of the off axis signals between 45 degrees and 115 degrees where 0 degrees corresponds to the on axis direction was nearly constant the sound pressure level of the off axis signals reached 162 db re 1 micropa peak to peak the surface echo level received at the animal was over 140 db much higher than the auditory threshold level of small odontocetes finless porpoises are estimated to be able to receive the surface echoes of off axis signals even at 50 m depth shallow water systems less than 50 m depth are the dominant habitat of both oceanic and freshwater populations of this species surface echoes may provide porpoises not only with diving depth information but also with information about surface direction and location of obstacles including prey items outside the on axis sector of the sonar beam

spatial variation of strontium isotopes 87sr 86sr in the maya region a tool for tracking ancient human migration strontium isotope ratios 87sr 86sr in human bones and teeth have become a useful tool to study migration and sedentism of individuals from archaeological contexts here we analyzed 87sr 86sr of water bedrock soils and plants across a broad geographic region to test the potential of this method in the ancient maya area our aims were two fold first to test if the sources of dietary strontium i e plants and water in humans reflect the 87sr 86sr ratio of exposed bedrock and second to determine whether the ranges of 87sr 86sr values were sufficiently distinct among the principal maya geocultural areas to infer past migration we identified five distinct subregions on the basis of geologic maps and evaluated the variability of 87sr 86sr values values given as mean 87sr 86sr 2 standard deviations number of samples 1 northern lowlands 0 70888 0 00066 n 16 2 southern lowlands 0 70770 0 00052 n 86 3 volcanic highlands and pacific coast 0 70415 0 00023 n 34 4 metamorphic province 0 70743 0 00572 n 50 and 5 the maya mountains of belize 0 71327 0 00167 n 3 although the sample size is small and overlap exists in 87sr 86sr values among some subregions most areas can be readily distinguished from one another on the basis of strontium isotopes these subregional 87sr 86sr differences provide archaeologists with a powerful tool to recognize geographic outliers in ancient maya burials and thereby test hypotheses concerning the origin of specific individuals inferred population migration patterns and the possibility of outside cultural influences in the maya region

determination of antarctic ice sheet stability over the last 500 ka through a study of iceberg rafted debris we have analyzed ice rafted debris ird from the south atlantic ocean 43 s 9 e in order to investigate antarctic ice sheet history during the late pleistocene the cores examined for this study include piston core tn057 6 pc4 and ocean drilling program leg 177 drill core site 1090 177 1090 over the last 500 ka at this distal location ird arrived during both glacials and interglacials ird is present even during warmer intervals is greatest during colder intervals and is absent only during terminations and a few other brief intervals four different methods are used to normalize the ird counts which are then compared to support our interpretation several other high quality climate proxies from this location also aid our interpretations we conclude that sea surface temperatures are the primary control on the delivery of ird to this site during cold times more icebergs survived to reach this distal location during warm times only a few of the largest icebergs could travel this far garnets found in these sediments suggest a likely east antarctic origin for the ird the presence of garnets even during warm intervals further strongly supports that the iceberg source must be the east antarctic ice sheet eais therefore the eais must have continued to reach the ocean at least in some part of its margin throughout the last 500 ka on the other hand we cannot specifically trace any ird to the west antarctic ice sheet wais so wais persistence cannot be tested a particular radiolarian identified as dictyocoryne profunda ehrenberg sensu boltovskoy 1998 shows up in the examined size fraction generally only during warm phases we suggest that d profunda is a sensitive indicator of warm water temperatures and that it deserves further study

the presence of polynyas in the weddell sea during the last glacial period with implications for the reconstruction of sea ice limits and ice sheet history cores from a contourite drift on the continental slope in the nw weddell sea antarctica contain up to four sandy foraminifer rich layers wa1 4 with dispersed ice rafted debris ird interbedded with silty clayey sands and sandy muds accelerator mass spectrometry ams 14c dating on neogloboquadrina pachyderma from the foraminifer rich layers wa2 and wa3 yielded ages spanning the last glacial maximum lgm and marine isotope stage mis 2 20 319 28 543 cal yr bp and the middle part of mis 3 41 349 43 242 cal yr bp respectively we attribute the high abundances of planktonic and benthic foraminifera to deposition in a seasonally open marine environment given that the nw weddell sea shelf was covered by grounded ice at the lgm and probably during mis 2 and mis 3 and that diatom based reconstructions place the northern limit of winter and summer sea ice coverage to the north of the core sites during the last glacial period our results document the presence of a seasonal or perennial polynya in the nw weddell sea the polynya may have been formed by katabatic winds blowing off the antarctic peninsula ice sheet apis when it was grounded at the continental shelf break although polynya formation through upwelling of deep water cannot be ruled out in addition we argue that previously published data from the southern southeastern and southwestern weddell sea as well as the ross sea may indicate the widespread occurrence of polynyas along the antarctic continental margin during the last glacial period the widespread occurrence of polynyas could help explain how i aabw formation through brine rejection continued throughout the lgm and ii antarctic shelf benthos survived glacial periods the presence of polynyas through glacial periods also has implications for sea ice reconstructions from ice core records possibly biasing the signal towards a reduced sea ice cover finally we propose that the fringes of the apis which probably influence the presence or absence of polynyas in the nw weddell sea are sensitive to changes in antarctic temperature that may be related to a reduction in oceanic heat transport from the north atlantic

inter annual and decadal sea level variations in the north western pacific marginal seas abstract long term sea level changes in the okhotsk japan east east china and yellow seas have been explored based on mean monthly values of sea level from tide gauge and altimetry measurements the analysis of low frequency sea level variability reveals clearly differentiated areas the okhotsk sea and the northern sector of the japan east sea display lower sea level variances and no sea level rise the southern japan east sea presents larger sea level variability associated with the circulation regime of the warm current entering through the tsushima strait and inter annual sea level variations that are driven by steric and atmospheric changes the largest sea level variances are found in the yellow sea due to the effect of atmospheric forcing over the continental shelf inter annual variability is spatially varying within the yellow sea and the east china sea and is mainly related to the steric sea level changes regional mean sea level indices have been synthesized for each area using the longest tide gauge records and have revealed correlations between the southern japan east and yellow seas with pdo and np climatic indices linear trends at coastal sites in the japan east east china and yellow seas show a rather heterogeneous pattern with values between 1 5 and 5 5 mm yr for the period 1960 2000 during the period 1993 2008 linear trends derived from coastal tide gauges and from altimetry observations are coherent and reveal a southwards increasing pattern with maximum averaged values reached at the yellow sea 4 9 1 9 mm yr followed by the japan east sea 3 8 0 9 mm yr decadal rates of sea level change show distinct behaviour among basins as well as with the global average the southern japan east sea the east china sea and the yellow sea display decadal variability which is out of phase with respect to the global values

abrupt cooling of antarctic surface waters and sea ice expansion in the south atlantic sector of the southern ocean at 5000 cal yr b p antarctic surface waters were warm and ice free between 10 000 and 5000 cal yr b p as judged from ice rafted debris and microfossils in a piston core at 53 s in the south atlantic this evidence shows that about 5000 cal yr b p sea surface temperatures cooled sea ice advanced and the delivery of ice rafted detritus ird to the subantarctic south atlantic increased abruptly these changes mark the end of the hypsithermal and onset of neoglacial conditions they coincide with an early neoglacial advance of mountain glaciers in south america and new zealand between 5400 and 4900 cal yr b p rapid middle holocene climate changes inferred from the taylor dome ice core antarctica cooling and increased ird in the north atlantic and the end of the african humid period the near synchrony and abruptness of all these climate changes suggest links among the tropics and both poles that involved nonlinear response to gradual changes in northern hemisphere insolation sea ice expansion in the southern ocean may have provided positive feedback that hastened the end of the hypsithermal and african humid periods in the middle holocene

interpreting iceberg deposits in the deep sea in their report millennial scale instability of the antarctic ice sheet during the last glaciation 9 june p 1815 s l kanfoush et al suggest that increases in ice rafted detritus ird observed in deep sea sediment records from the south atlantic ocean identify times of instability of

high precision pb isotope measurements reveal magma recharge as a mechanism for ore deposit formation examples from lihir island and conical seamount papua new guinea abstract lihir island part of the tabar lihir tanga feni island chain in the sw pacific hosts the giant ladolam gold deposit polymetallic gold mineralization also was discovered offshore at conical seamount in 1998 during rv sonne cruise so 133 the seamount and the island are composed mainly of trachybasalts and basaltic trachyandesites although some monzonites are found on lihir sr isotopic analyses of mineralized samples from the island and the seamount suggest that most of the sr is derived from the local alkaline lavas elevated 87sr 86sr ratios in some of the samples suggest that during the waning stages of the hydrothermal system part of the sr was contributed either from seawater or the thick sequence of marine sediments underlying the island high precision pb isotopic analyses conducted with mc icp ms show that the ores and volcanic rocks share similar pb isotopic compositions suggesting that the pb in the mineralized zones was ultimately derived from local magmatic sources the pb isotopic data however reveal small but significant differences between the mineralized zones and the associated host lavas mineralized samples from lihir have slightly less radiogenic lead isotopic ratios than their host lavas these lead isotopic compositions are similar however to some of the fresh lavas recovered from conical seamount and to a monzonite intrusion underlying the ladolam deposit lead isotopic ratios in mineralized samples from conical seamount are slightly more radiogenic than their host lavas and similar to those of fresh lavas recovered from nearby tubaf and edison seamounts petrographic observations and microprobe elemental analyses reveal a complex magmatic history for the magma chamber inferred beneath conical seamount based on zoning patterns in the conical seamount clinopyroxenes it appears that a sub seamount magma chamber was recharged with a mafic magma similar to the most primitive volatile rich and xenolith bearing lavas recovered from tubaf and edison seamounts rapid cooling of this mafic magma accompanied by exsolution of metal bearing fluids in the relatively shallow magma chamber is proposed as the mechanism that ultimately led to the formation of the gold mineralization similarity of the lead isotopic ratios between the ores and the mafic magmas in the area indicate that the ore metals were primarily derived from the recharging magma not by hydrothermal leaching of the host lavas suggesting that ore deposit genesis can be related to a single volatile rich magmatic pulse within otherwise barren polyphased volcano magmatic complex

glacial interglacial terrigenous provenance in the southeastern atlantic ocean the importance of deep water sources and surface currents identifying terrigenous sources in deep sea sediments may re veal temporal trends in paleocirculation and the relative role of eolian upwelled and hemipelagic fe sources to surface waters bulk elemental and isotopic geochemistry of deep sea sediments recovered during ocean drilling program leg 177 in the south eastern atlantic sector of the southern ocean reveal several im portant aspects of paleocirculation and terrigenous provenance the sites studied span 43 53 s and represent different oceano graphic settings relative to regional hydrography and sediment type bulk sediment geochemistry indicates that terrigenous prov enance varied over the past 600 k y site 1089 the northernmost site exhibits clear glacial interglacial variability in provenance while provenance appears to vary regardless of climate state at the more southerly sites site 1093 and 1094 nd and sr isotopes and sm nd ratios of the terrigenous fraction indicate that study sites have geochemically distinguishable provenance nd and sr isotopes further suggest that sites 1089 and 1094 both contain detrital com ponents that originated in south america over the past 30 k y however site 1089 is also influenced by southern african sources and the strength of the agulhas current the nd data support a more hemipelagic source for the terrigenous material rather than an eolian source based on comparisons with antarctic ice core data and known sea ice extent

location and dynamics of the antarctic polar front from satellite sea surface temperature data the location of the antarctic polar front pf was mapped over a 7 year period 1987 1993 within images of satellite derived sea surface temperature the mean path of the pf is strongly steered by the topographic features of the southern ocean the topography places vorticity constraints on the dynamics of the pf that strongly affect spatial and temporal variability over the deep ocean basins the surface expression of the pf is weakened and the pf meanders over a wide latitudinal range near large topographic features width and temperature change across the front increase and large scale meandering is inhibited elevated mesoscale variability is seen within and downstream of these areas and may be the result of baroclinic instabilities initiated where the pf encounters large topographic features the strong correlations between topography and pf dynamics can be understood in the context of the planetary potential vorticity ppv or f h field mean ppv at the pf varies by more than a factor of 2 along its circumpolar path however at the mesoscale the pf remains within a relatively narrow range of ppv values around the local mean away from large topographic features the pf returns to a preferred ppv value of 25 10 9 m 1 s 1 despite large latitudinal shifts the mean paths of the surface and subsurface expressions of the pf are closely coupled over much of the southern ocean

the acoustic field on the forehead of echolocating atlantic bottlenose dolphins tursiops truncatus arrays of up to six broadband suction cup hydrophones were placed on the forehead of two bottlenose dolphins to determine the location where the beam axis emerges and to examine how signals in the acoustic near field relate to signals in the far field four different array geometries were used a linear one with hydrophones arranged along the midline of the forehead and two around the front of the melon at 1 4 and 4 2 cm above the rostrum insertion and one across the melon in certain locations not measured by other configurations the beam axis was found to be close to the midline of the melon approximately 5 4 cm above the rostrum insert for both animals the signal path coincided with the low density low velocity core of the melon however the data suggest that the signals are focused mainly by the air sacs slight asymmetry in the signals were found with higher amplitudes on the right side of the forehead although the signal waveform measured on the melon appeared distorted when they are mathematically summed in the far field taking into account the relative time of arrival of the signals the resultant waveform matched that measured by the hydrophone located at 1 m

relationship between magnetic susceptibility and sediment grain size since the last glacial period in the southern ocean off the northern antarctic peninsula linkages between the cryosphere and atmospheric circulation abstract magnetic susceptibility ms values in scotia sea sediments showed strong correlations to ice core non sea salt ca2 concentration dust input which emphasizes the role of atmospheric circulation in the southern ocean as a result the correlation between these values was suggested as a powerful tool for age reconstruction of marine sediments in the southern ocean however controls on ms variation in scotia sea sediments are not clear in this study we documented records of grain size ms values 10 6 cgs g of bulk sediments and ms values of sand sized 63 m coarse silt sized 16 63 m and fine sediment fractions

ice rafted volcanic ash in the south atlantic sector of the southern ocean during the last 100 000 years abstract eucampia antarctica castr mangin abundance curves for two piston cores from the western agulhas basin southeast atlantic sector of the southern ocean were used to place volcanic glass shard and ice rafted debris abundance curves into a stratigraphic framework for the last 100 000 years a direct correlation is shown between increased abundance of e antarctica tephra and ice rafted debris low abundances are often characterized by calcareous sediment in the northern core peaks in abundance of e antarctica have been interpreted as an indication of glacial periods and the increased ice rafted debris and tephra during glacial periods is evidence for an ice rafted origin for the tephra microprobe geochemical analysis of volcanic glass shards provides no single distinct source for the ash the geochemical data is consistent but not definitive with a primary source in the scotia arc and a minor source from bouvet island between core correlations of geochemically fingerprinted dispersed tephra zones were not successful due to variability of glass shard geochemistry and limited sample size

assessing the link between coastal morphology wave energy and sea ice throughout the holocene from antarctic raised beaches post glacial rebound has preserved beaches across many ice free parts of the antarctic coastline these beaches typically contain gravel to boulder sized deposits and are built by high magnitude waves five new ages from the western antarctic peninsula were added to a compilation of 282 published ages from antarctic beaches a reduced compilation based solely on those ages that date beach formation is used to assess variations in beach formation throughout the holocene around antarctica we suggest the clustering of beach ages centered at 0 8 and 2 4 ka in the antarctic peninsula 1 5 3 6 and 6 0 ka in the ross sea and a broad peak from 2 7 to 6 3 ka in east antarctica indicates periods of heightened wave exposure leading to increased beach formation measurements of clast roundness from raised beaches show more rounded material is coincident with periods of heightened beach formation providing an independent means of assessing wave climate a comparison of periods of increased beach formation with available sea ice proxies suggests beach formation is synchronous with reduced sea ice conditions and thus higher wave climate as the presence or absence of sea ice determines open water conditions the factors that control sea ice directly influence antarctic coastal evolution

why are there upwellings on the northern shelf of taiwan under northeasterly winds upwellings are observed on the northern shelf of taiwan during northeasterly winds analytical and realistic numerical models are used to explain how vertical motions are created by divergence and convergence produced by wind acting on the vorticity field of two strong jets the kuroshio and the taiwan warm current the seaward increase in cyclonic vorticity near the kuroshio s western edge favors a stronger ekman transport away from the jet producing upwelling at the shelfbreak under a northeasterly wind a similar mechanism for generating vertical motions is found across the taiwan warm current the numerical model results indicate that the vorticity effects can account for up to 30 50 of the total variation in the surface ekman transport except during summer s weak southwesterlies northeasterly wind is dominant over the east china sea suggesting that the vorticity effects may be prominent in the observed shelfbreak upwelling in nonsummer months

presence of large pumice blocks on tierra del fuego and south shetland islands shorelines from 1962 south sandwich islands eruption abstract we report on the source of pumice found on beaches of tierra del fuego argentina and the south shetland islands antarctica north and south of the drake passage petrological studies chemical analyses and experiments on this pumice indicate it is most likely from a 1962 submarine eruption in the south sandwich islands previous work stated that clockwise marine currents carried such pumice as far as tasmania our findings show that the currents continued to transport the pumice to drake passage nearly completing a circuit around antarctica and up to southern argentina showing that this material can follow complex pathways for more than 20 000 km

southern ocean sea ice extent productivity and iron flux over the past eight glacial cycles sea ice and dust flux increased greatly in the southern ocean during the last glacial period palaeorecords provide contradictory evidence about marine productivity in this region but beyond one glacial cycle data were sparse here we present continuous chemical proxy data spanning the last eight glacial cycles 740 000 years from the dome c antarctic ice core these data constrain winter sea ice extent in the indian ocean southern ocean biogenic productivity and patagonian climatic conditions we found that maximum sea ice extent is closely tied to antarctic temperature on multi millennial timescales but less so on shorter timescales biological dimethylsulphide emissions south of the polar front seem to have changed little with climate suggesting that sulphur compounds were not active in climate regulation we observe large glacial interglacial contrasts in iron deposition which we infer reflects strongly changing patagonian conditions during glacial terminations changes in patagonia apparently preceded sea ice reduction indicating that multiple mechanisms may be responsible for different phases of co2 increase during glacial terminations we observe no changes in internal climatic feedbacks that could have caused the change in amplitude of antarctic temperature variations observed 440 000 years ago

the biosonar field around an atlantic bottlenose dolphin tursiops truncatus the use of remote autonomous passive acoustic recorders par to determine the distribution of dolphins at a given locations has become very popular some investigators are using echolocation clicks to gather information on the presence of dolphins and to identify species however in all of these cases the par probably recorded mainly off axis clicks even some from behind the animals yet there is a very poor understanding of the beam pattern and the click waveform and spectrum from different azimuths around the animal s body the beam pattern completely around an echo locating dolphin was measured at 16 different but equally spaced angles in the horizontal plane using an 8 hydrophone array in sequence eight channels of data were digitized simultaneously at a sampling rate of 500 khz the resulting beam patterns in both planes showed a continuous drop off in sound pressure with azimuth around the animal and reached levels below 50 db relative to the signal recorded on the beam axis the signals began

melting history of antarctica during the past 60 000 years marked changes in the surface water hydrology of the southern ocean during the past 60 kyr are revealed by a detailed comparison of the oxygen isotopic composition of planktonic and benthic foraminifera from sediment cores and the surface water temperature estimated by a transfer function derived from the distribution of diatoms in the same sediments from 35 to 17 kyr bp the southern ocean polar front was covered by a melt water lid containing a significant contribution from melting icebergs calved from antarctic ice shelves these icebergs may have originated from a succession of surges of the ice shelves

millennial scale instability of the antarctic ice sheet during the last glaciation records of ice rafted detritus ird concentration in deep sea cores from the southeast atlantic ocean reveal millennial scale pulses of ird delivery between 20 000 and 74 000 years ago prominent ird layers correlate across the polar frontal zone suggesting episodes of antarctic ice sheet instability carbon isotopes 13 c of benthic foraminifers a proxy of deepwater circulation reveal that south atlantic ird events coincided with strong increases in north atlantic deep water nadw production and inferred warming interstadials in the high latitude north atlantic sea level rise or increased nadw production associated with strong interstadials may have resulted in destabilization of grounded ice shelves and possible surging in the weddell sea region of west antarctica

southern ocean bioproductivity during the last glacial cycle new detection method and decadal scale insight from the scotia sea we present biogenic opal flux records from two deep sea sites in the scotia sea md07 3133 and md07 3134 at decadal scale resolution covering the last glacial cycle in addition to conventional and time consuming biogenic opal measuring methods we introduce new biogenic opal estimation methods derived from sediment colour b wet bulk density si ti count ratio and fourier transform infrared spectroscopy ftirs all methods capture the biogenic opal amplitude however ftirs a novel method for marine sediment yields the most reliable results 230th normalization data show strong differences in sediment focusing with intensified sediment focusing during glacial times at md07 3134 230th normalized biogenic opal fluxes vary between 0 2 and 2 5 g cm22 kyr21 our biogenic opal flux records indicate bioproductivity changes in the southern ocean strongly influenced by sea ice distribution and also summer sea surface temperature changes south of the antarctic polar front lowest bioproductivity occurred during the last glacial maximum when upwelling of mid depth water was reduced and sea ice cover intensified around 17 ka bioproductivity increased abruptly corresponding to rising atmospheric co2 and decreasing seasonal sea ice coverage

origin and significance of ice rafted detritus in the atlantic sector of the southern ocean piston core tn057 14 from the eastern atlantic sector of the southern ocean contains several layers rich in volcanic tephra that were deposited during the last glacial period comparison with nearby cores tn057 13pc4 odp site 1094 indicates that these tephra layers are correlative with the south atlantic sa ice rafted detritus ird layers identified by kanfoush et al 2000 2002 we analyzed the tephra for major and trace elements as well as isotopic ratios of strontium neodymium and lead the elemental and isotopic composition of all tephra layers examined indicates the south sandwich island volcanic arc ssi as their dominant source with minor input from bouvet island similar analyses of clear mineral grains mainly feldspars quartz and olivine also point to the ssi as the main source we conclude that tephra erupted from the ssi was first deposited as air fall on sea ice and multiyear ice and then secondarily rafted to the studied sites deposition of the tephra rich ird layers was controlled by changes in sea surface temperature and sea ice conditions in the polar frontal zone of the south atlantic rather than antarctic ice sheet dynamics

subduction zone volcanic ash can fertilize the surface ocean and stimulate phytoplankton growth evidence from biogeochemical experiments and satellite data volcanoes confront earth scientists with new fundamental questions can airborne volcanic ash release nutrients on contact with seawater thereby excite the marine primary productivity mpp and most notably can volcanoes through oceanic fertilization affect the global climate in a way that is so far poorly understood here we present results from biogeochemical experiments showing that 1 volcanic ash from subduction zone volcanoes rapidly release an array of nutrients co limiting algal growth in vast oceanic areas 2 at a speed much faster minute scale than hitherto known and that marine phytoplankton from low iron oceanic areas can swiftly within days utilize iron from volcanic sources we further present satellite data possibly indicating an increase of the mpp due to the seaward deposition of volcanic particulate matter our study supports the hypothesis that oceanic iron fertilization with volcanic ash may play a vital role for the development of the global climate

the southern ocean at the last glacial maximum a strong sink for atmospheric carbon dioxide analysis of satellite ocean color sea surface temperature and sea ice cover data reveals consistent patterns between biological production iron availability and physical forcings in the southern ocean the consistency of these patterns in conjunction with information on physical conditions during the last glacial maximum lgm enables estimates of export production at the lgm the lgm southern ocean experienced increased wind speeds colder sea surface and atmospheric temperatures increased deposition of atmospheric dust and a greatly expanded winter sea ice cover these variations had strong effects on southern ocean ecology and on air sea fluxes of co2 the seasonal ice zone siz was much larger at the lgm 30 million km2 than at present 19 million km2 the antarctic polar front pf likely marked the northern boundary of this expanded siz throughout the southern ocean as it does today in the drake passage region a large northward shift in the position of the pf during glacial times is unlikely due to topographic constraints north of the pf the increased flux of aeolian dust during glacial times altered phytoplankton species composition and increased export production and as a result this region was a stronger sink for atmospheric co2 than in the modern ocean south of the pf interactions between the biota and sea ice strongly influence air sea gas exchange over seasonal timescales the combined influence of melting sea ice and increased aeolian dust flux with its associated iron increased both primary and export production by phytoplankton over daily monthly timescales during austral spring summer resulting in a strong flux of co2 into the ocean heavy ice cover would have minimized air sea gas exchange over much of the rest of the year thus an increased net flux of co2 into the ocean is likely during glacial times even in areas where annual primary production declined we estimate that export production in the southern ocean as a whole was increased by 2 9 3 6 gt c yr 1 at the lgm relative to the modern era altered seasonal sea ice dynamics would further increase the net flux of co2 into the ocean thus the southern ocean was a strong sink for atmospheric co2 and contributed substantially to the lowering of atmospheric co2 levels during the last ice age

the mis 11 paradox and ocean circulation role of millennial scale events the role of millennial scale climate variability in supplementing the astronomical forcing of glacial interglacial transitions remains a major unresolved question here we compare the occurrence and character of terminal ice rafting events in both the north and south atlantic during the last deglaciation termination i ti and during the transition between marine isotope stages mis 12 and 11 or termination v tv we show that tv experienced a massive terminal ice rafting event in the north atlantic that was more intense and longer lasting than heinrich event 1 h1 of the last deglaciation this massive ice rafting event was linked to cold stadial conditions and reduced deep water formation in the north atlantic in parallel with warming at high southern latitudes similar to the bipolar seesaw pattern exhibited during h1 over the last deglaciation we propose that the particular intensity and duration of the tv ice rafting event resulted from the especially large volume of northern hemisphere ice sheets during mis12 in turn the unusually long duration and large amplitude of tv likely resulted from the exceptionally prolonged collapse of the amoc during the tv heinrich stadia and from a subsequent transient amoc overshoot with respect to later mis11 interglacial circulation furthermore we suggest that the intense heinrich stadial of tv contributed to the deglaciation primarily via meridional heat transport anomalies that would have enhanced the incipient warming arising from relatively weak insolation forcing and only secondarily via co2 release

climate mediated size variability of diatom fragilariopsis kerguelensis in the southern ocean abstract fragilariopsis kerguelensis o meara hustedt is the most abundant open ocean diatom species in southern ocean sediments and its average valve area has recently been used to infer glacial interglacial paleoceanographic conditions studies from the atlantic sector of the southern ocean demonstrated how larger average valve area of f kerguelensis during the last glacial compared to the interglacial possibly relate to greater availability of iron through wider sea ice coverage and higher eolian dust input we present here data on average valve area of f kerguelensis from three sediment cores covering the last 42 cal ka bp from different zones of the southern ocean our records confirm previous results from the atlantic sector but highlight a different pattern from the indian sector where the largest valves of f kerguelensis are encountered during the holocene fragilariopsis kerguelensis average valve area variations in the antarctic polar front apf of the atlantic sector and subantarctic front of the indian sector are in phase with records of opal burial while this correlation does not hold for the apf of the indian sector variations in circum polar upwelling were suggested as the main controlling factor of opal production during the last 20 000 years we here hypothesize that high nutrient input from the antarctic peninsula during the last deglaciation may have exerted a stronger control on f kerguelensis average valve area and opal export in the atlantic sector of the southern ocean than inferred changes in circum polar upwelling

acoustic property reconstruction of a pygmy sperm whale kogia breviceps forehead based on computed tomography imaging computed tomography ct imaging and sound experimental measurements were used to reconstruct the acoustic properties density velocity and impedance of the forehead tissues of a deceased pygmy sperm whale kogia breviceps the forehead was segmented along the body axis and sectioned into cross section slices which were further cut into sample pieces for measurements hounsfield units hus of the corresponding measured pieces were obtained from ct scans and regression analyses were conducted to investigate the linear relationships between the tissues hus and velocity and hus and density the distributions of the acoustic properties of the head at axial coronal and sagittal cross sections were reconstructed revealing that the nasal passage system was asymmetric and the cornucopia shaped spermaceti organ was in the right nasal passage surrounded by tissues and airsacs a distinct dense theca was discovered in the posterior dorsal area of the melon which was characterized by low velocity in the inner core and high velocity in the outer region statistical analyses revealed significant differences in density velocity and acoustic impedance between all four structures melon spermaceti organ muscle and connective tissue p 0 001 the obtained acoustic properties of the forehead tissues provide important information for understanding the species bioacoustic characteristics

dynamics of biosonar signals in free swimming and stationary dolphins the role of source levels on the characteristics of the signals the biosonar signals of two free swimming atlantic bottlenose dolphins performing a complex sonar search for a bottom target in san diego bay were compared with the biosonar signals of a dolphin performing a target discrimination task in a net pen in the same bay a bite plate device carried by the free swimming dolphins supported a hydrophone that extended directly in front of the dolphin a biosonar measuring tool attached to the bite plate measured the outgoing biosonar signals while the dolphins conducted sonar searches each of the free swimming dolphins used different biosonar search strategy in solving the problem and the dolphins biosonar signals reflect the difference in strategy the dolphin in the pen stationed in a hoop while echolocating on a target 6 m away and reported if the indentation on a spherical target was directed toward it the signals were parameterized by determining the peak to peak source levels source energy flux density peak frequency center frequency root mean square rms bandwidth rms duration and the q of the signals some parameters were similar for the free swimming and stationary dolphins while some were significantly different suggesting biosonar signals used by free swimming animals may be different than signals used by dolphins in a pen

vertical gradient correction for the oceanographic atlas of the east asian seas regional climatology around the east asian seas has been developed by an international collaboration between the national oceanic data center and the korea oceanic data center it provides reliable information on temperature and salinity climatological fields with high resolution 0 1 0 1 by 137 levels however there is a problem around near bottom areas where topographic change is steep and observations are not available near the bottom this study resolves this problem using a vertical gradient correction method when the profile is statically unstable the stability is determined based on the brunt vaisala frequency with individual temperature and salinity profiles topographic following mapping technique employing the potential vorticity constraint term is used to construct a vertical gradient database for the temperature and salinity at every grid point the results show that the correction is effective for eliminating large erroneous vertical gradients around near bottom areas in addition we show the importance of the optimal length scale to construct a precise vertical gradient database in a particular area such as the northern shelf of taiwan we expect that our revised high resolution climatological mean fields will serve as important data for relevant studies around the east asian seas

comparison of ice rafted debris and physical properties in odp site 1094 south atlantic with the vostok ice core over the last four climatic cycles abstract visual counts of ice rafted debris ird foraminifera and radiolaria were made for 1500 samples in site 1094 spanning the last four climatic cycles marine isotope stages 1 11 most but not all of the ird variability is captured by whole core physical properties including magnetic susceptibility and ray attenuation bulk density glacial periods are marked by high ird abundance and millennial scale variability which may reflect instability of ice shelves in the weddell sea region each interglacial period exhibits low ird and high foraminiferal abundance during the early part of the interglacial indicating relatively warm sea surface temperatures and reduced influence of sea ice ird increases and foraminiferal abundances decrease during the latter part of each interglacial indicating a return to more glacial like conditions glacial terminations i and v are each characterized by a step wise reduction in ice rafting punctuated by a brief pulse in ird delivery and reversal in 18o the coarse fraction of the sediment is dominated by ash and radiolaria and the relative abundance of these components is remarkably similar to the concentration of na in vostok each of these variables is believed to be controlled mainly by sea ice cover thereby providing a means for sediment ice core correlation

computer modeling of acoustic beam formation in delphinus delphis it has been established that some dolphins possess well developed acoustic orientation echolocation and information gathering abilities though substantially less is known about the system of sound generation and beam formation dolphins use a narrowly focused sound beam that emanates from the forehead and rostrum during echolocation the primary objectives of this study were to simulate the effects of anatomical structure on beam formation and to test the viability of various hypothetical sound source locations outlines from parasagittal x ray ct scans were used to construct a 2 d model of the head of the common dolphin delphinus delphis finite difference techniques were used to simulate sound propagation through tissues modeled as inhomogeneous fluids preliminary simulations confirm that beam formation results primarily from reflection off of the skull and the skull supported air sac surfaces for the frequencies tested beam angles best approximate those measured by experimental methods for a so

characteristics and sources of tephra layers in the epica dome c ice record east antarctica implications for past atmospheric circulation and ice core stratigraphic correlations thirteen discrete air fall tephra layers were identified in the last 200 000 yr section of the epica dome c ice record drilled in the east antarctic plateau 75 06 s 123 21 e quantitative grain size glass particle morphology and the grain discrete major element composition of the glass fraction of these layers were investigated through comparison with literature data on the rock composition of quaternary volcanic centres located within and around antarctica five tephra layers were attributed to south sandwich volcanoes in the south atlantic ocean two to south shetland volcanoes northern antarctic peninsula two to andean volcanoes and four to antarctic marie byrd land and melbourne provinces the abundance of layers originating in the southern part of the atlantic confirms that westerly atmospheric circulation spiralling towards east antarctica prevailed over the last 200 ka moreover the record of events from antarctic centres suggests that atmospheric trajectories from west to east antarctica can also be significant a few ash layers are geochemically distinct and appear equivalent to levels from vostok and dome fuji deep ice records located ca 600 km and ca 2000 km respectively from dome c on the antarctic plateau these layers provide unambiguous markers for future correlation with other antarctic ice cores and circumpolar marine climatic records they also provide reliable constraints to get a common timescale by glaciological modelling and represent a first step towards absolute ice core dating

sequence of events during the last deglaciation in southern ocean sediments and antarctic ice cores variation depends on the age model as 14 c determinations cannot be obtained for the time interval of 29 5 14 5 ka assuming a constant sedimentation rate for this interval our data suggest that sea ice and nutrient changes at about 19 ka b p lead the increase in atmospheric pco2 by approximately 2000 years our diatom based sea ice record is in phase with the sodium record of the vostok ice core which is related to sea ice cover and similarly leads the increase in atmospheric co2 if gas exchange played a major role in determining glacial to interglacial co2 variations then a delay mechanism of a few thousand years is needed to explain the observed sequence of events otherwise the main cause of atmospheric pco2 change must be sought elsewhere rather than in the southern ocean index terms 3344 meteorology and atmospheric dynamics paleoclimatology 4267 oceanography general paleoceanography 4845 oceanography biological and chemical nutrients and nutrient cycling 4870 oceanography biological and chemical stable isotopes 9325 information related to geographic region atlantic ocean keywords biogenic opal stable isotopes diatoms ird last glacial southern ocean

application of modern analog technique to marine antarctic diatoms reconstruction of maximum sea ice extent at the last glacial maximum modern analog technique mat applied to antarctic diatoms is a new approach for quantitative sea ice paleoreconstructions in the southern ocean in a first step we show that mat is a better approach than the imbrie and kipp method to reconstruct the modern sea ice pattern we then use this approach to reconstruct sea ice presence in number of months per year during the last glacial maximum lgm at this time sea ice presence was greater than today leading to a shorter diatom growing season the maximum sea ice extent inferred from quantitative values of sea ice presence was located 5 8 north of its actual position leading to double the surface of modern winter sea ice this greater sea ice extent may have played a significant role on atmospheric and surface oceanic circulations and therefore on southern mid latitude and high latitude climates it may also have reduced the amount of heat moisture and co2 from the ocean to the atmosphere thus participating in the lowering of atmospheric co2 during the lgm

south pole glacial climate reconstruction from multi borehole laser particulate stratigraphy the icecube neutrino observatory and its prototype amanda were built in south pole ice using powerful hot water drills to cleanly bore 100 holes to depths up to 2500 m the construction of these particle physics detectors provided a unique opportunity to examine the deep ice sheet using a variety of novel techniques we made high resolution particulate profiles with a laser dust logger in eight of the boreholes during detector commissioning between 2004 and 2010 the south pole laser logs are among the most clearly resolved measurements of antarctic dust strata during the last glacial period and can be used to reconstruct paleoclimate records in exceptional detail here we use manual and algorithmic matching to synthesize our south pole measurements with ice core and logging data from dome c east antarctica we derive impurity concentration precision chronology annual layer thickness local spatial variability and identify several widespread volcanic ash depositions useful for dating we also examine the interval around similar to 74 ka recently isolated with radiometric dating to bracket the toba sumatra supereruption

extensive phytoplankton blooms in the atlantic sector of the glacial southern ocean 1 the sources and sinks of atmospheric carbon dioxide over glacial interglacial cycles are under debate variation in productivity of the antarctic circumpolar current acc could potentially play a significant role but current interpretations of sedimentary geochemical proxies suggest that glacial productivity was not higher than today we present areal and down core distribution patterns of previously overlooked diatom resting spores that indicate the occurrence of extensive phytoplankton blooms across the entire atlantic sector of the acc particularly in the seasonal ice zone siz linked to higher iron input during the last glacial sea ice acts as an effective transporter of iron and enhances its bioavailability the dominance of the deep living radiolarian cyladophora davisiana in glacial siz sediments indicates that organic carbon export to mesopelagic depths was at least tenfold higher than today

comparing the epica and vostok dust records during the last 220 000 years stratigraphical correlation and provenance in glacial periods a new aeolian dust record from the first 2200 m of the epica dome c ice core 75 06 s 123 21 e covering about 220 000 years of climatic history is compared to the vostok 78 28 s 106 48 e ice core nature 399 1999 429 the two dust profiles are very similar and several common dust events allow to establish stratigraphical links the late quaternary period is characterized at both sites and likely overall east antarctic plateau by high dust input during glacial periods in the epica dome c ice core the dust flux rises by a factor of 25 20 and 12 in glacial stages 2 4 and 6 with respect to interglacial periods holocene and stage 5 5 the magnitude and pattern of changes are comparable in the vostok ice core in this study the geographical origin of ice core dust icd in cold periods has been investigated at both sites through 87sr 86sr versus 143nd 144nd isotopic tracers following the previous studies of grousset et al earth planet sci lett 111 1992 175 and basile et al earth planet sci lett 146 1997 573 the new data and the existing ones allow to define the isotopic fields for dust at the two antarctic sites that are almost identical and restricted into the 0 708 87sr 86sr 0 711 and 5 end 0 5 ranges this suggests a common geographical provenance for dust at vostok and dome c and for all the glacial periods of the late pleistocene to decipher the icd provenance more than 50 samples of loess and aeolian deposits sands and fluvioglacial sediments from the potential source areas psas of the southern hemisphere have been collected however the methodology has been refined with respect to former studies first the isotopic fractionation that can occur in function of grain size has been taken into account and the psa s signature has been defined in the 5 m size range within which fine grained dust reaching antarctica is found moreover a possible contribution from carbonates on the samples from psas has also been also considered south africa and australia can be excluded as dominant sources but a partial overlap arises among southern south america new zealand and the antarctic dry valleys isotopic fields these latter two documented for the first time a possible contribution from all these three sources cannot be excluded but complementary arguments suggest the dominant contribution to east antarctic dust in glacial times deriving from the southern south american region of patagonia and the pampas this study shows a first order uniformity in the dust flux and geographical provenance to the east antarctica plateau during glacial periods

radiocarbon calibration curve spanning 0 to 50 000 years bp based on paired 230 th 234 u 238 u and 14 c dates on pristine corals abstract radiocarbon dating is the most widely used dating technique in the world recent advances in accelerator mass spectrometry ams and sample preparation techniques have reduced the sample size requirements by a factor of 1000 and decreased the measurement time from weeks to minutes today it is estimated that more than 90 percent of all measurements made on accelerator mass spectrometers are for radiocarbon age dates the production of 14 c in the atmosphere varies through time due to changes in the earth s geomagnetic field intensity and in its concentration which is regulated by the carbon cycle as a result of these two variables a radiocarbon age is not equivalent to a calendar age four decades of joint research by the dendrochronology and radiocarbon communities have produced a radiocarbon calibration data set of remarkable precision and accuracy extending from the present to approximately 12 000 calendar years before present this paper presents high precision paired 230 th 234 u 238 u and 14 c age determinations on pristine coral samples that enable us to extend the radiocarbon calibration curve from 12 000 to 50 000 years before present we developed a statistical model to properly estimate sample age conversion from radiocarbon years to calendar years taking full account of combined errors in input ages and calibration uncertainties our radiocarbon calibration program is publicly accessible at http www radiocarbon ldeo columbia edu along with full documentation of the samples data and our statistical calibration model

glacial interglacial size variability in the diatom fragilariopsis kerguelensis possible iron dust controls 1 the valve area of fragilariopsis kerguelensis the most abundant diatom species in the southern ocean strongly changes in size in response to varying conditions in the surface ocean we examined the link both in two iron fertilization experiments and in sediment samples covering several glacial terminations between size variability in this species and environmental conditions across the antarctic polar front including sea ice extent sea surface temperature and the input of eolian dust the iron fertilization experiments show valve area to be positively correlated with iron concentrations in ambient waters which suggests the possibility of a causal relation between valve size of fragilariopsis kerguelensis and ambient surface water iron concentration larger valves are usually found during glacial times and thus seem to be related to lower sea surface temperature and wider sea ice coverage moreover our results indicate that there usually is a strong correlation between larger valve size and increased input of eolian dust to the southern ocean however this correlation obvious for the fertilization experiments and for glacial terminations i ii iii and v does not seem to be valid for termination vi where size appears to be inversely correlated to dust input citation cortese g r gersonde k maschner and p medley 2012 glacial interglacial size variability in the diatom fragilariopsis kerguelensis possible iron dust controls paleoceanography 27 pa1208 doi 10 1029 2011pa002187

metalliferous sediments from the h m s challenger voyage 1872 1876 abstract the legendary cruise of h m s challenger 1872 1876 around the globe must always occupy an eminent place in the annals of oceanography as being the first systematic attempt made on a global scale to explore the ocean this expedition made fundamental discoveries in biology and geology which have not been surpassed by any later scientific cruise sediment with high content of metals later called metalliferous was among the enigmatic findings taken onboard although the nature of metalliferous sediments is well known today the very first sampled sediments of this type have not been studied to date motivated by the historical value of challenger s metalliferous sediment collection we undertook an investigation addressing two questions 1 the composition of sediments from seafloor for which we have very limited data 2 sr nd pb fe zn isotope signature of these sediments collected before the substantial human impact on the ocean during the 20th century the se pacific metalliferous sediments sampled by the challenger s explorers are of 2 types 1 metalliferous oozes blanketing ridge crests and flanks down to the calcite compensation depth ccd and 2 stripped of caco 3 metalliferous sediments located beneath the ccd in the deeps near the mid ocean ridges the abiogenic part of these sediments is composed mainly of poorly crystalline to x ray amorphous fe mn oxyhydroxides and an amorphous silicate phase these sediments have geochemical features similar to those of all the other metalliferous sediments very high fe and mn content on abiogenic basis very low al al fe mn and high content on abiogenic basis of as ba be bi cd co cu mo ni pb sb th tl u v w y zn and zr their ree distribution patterns are similar to that of deep seawater and show weak signs of hydrothermal imprint weak positive or no eu anomaly seawater and or terrigenous input from south america control the sr nd pb isotope signature of the challenger metalliferous sediments and have almost completely obliterated any original morb derived hydrothermal signal zn isotopes are mainly contributed from seawater although other zn sources hydrothermal fluid and detrital aluminosilicates barite and volcanic glass are necessary to fully explain zn isotope ratios fe isotopes indicate relatively slow fe 2 to fe 3 oxidation in the non buoyant plume thus producing relatively lighter fe isotope signature of the feooh particles that formed the studied metalliferous sediments