simulations of two last glacial maximum ocean states two stable thermohaline circulation states were produced in simulations of the last glacial maximum lgm ocean both forced by the same prescribed atmosphere direct application of this atmosphere led to an equilibrium state with strong north atlantic deep water formation northern sinking state nss upon applying a weak freshwater flux anomaly to the north atlantic for a short time a state was entered with little north atlantic but significant southern ocean deep water formation southern sinking state sss a fully dynamic and thermodynamic iceberg trajectory model was developed and icebergs were seeded into both states distinctly different pathways were found particularly in the eastern atlantic where the sss icebergs tend to move south along the european coast while they move north in the nss while neither ocean state is claimed to be a definitive model for the lgm ocean paleoclimate data are more consistent with the characteristics of the nss

increased productivity in the eastern equatorial pacific during the last glacial maximum 19 000 to 14 000 yr b p a widespread pronounced enrichment in the organic carbon content occurs at shallow depths in eastern equatorial pacific sediments the c org peak is shown by radiocarbon dating to be temporally coincident with the last stage 2 or wisconsin glacial maximum in contrast caco 3 profiles show less overall variation which appears to be partly a function of the location of the sediments relative to the lysocline consideration of the iodine c org ratio in the sediments rules out enhanced preservation as a cause of the stage 2 organic carbon enrichment the peak instead must have resulted from a significant increase in productivity during the glacial maximum

near inertial internal wave interactions with mesoscale fronts observations and models moored observations of near inertial currents and buoyancy fluctuations from the frontal air sea interaction experiment fasinex may be understood as nearinertial internal waves reflecting off sheared background currents the fasinex moored array measured upper ocean currents temperature and conductivity between january and june 1986 in a region of the sargasso sea heavily populated by strong upper ocean fronts the background jets associated with these features have typical cross front scales of 20km maximum currents of 0 5 m s 1 and relative vorticities of 0 3 in the vicinity of fronts observed near inertial currents have short horizontal scales show no clear horizontal phase structure and trace out elongated current ellipses with elevated across front over along front variance during these periods inertial band pass buoyancy fluctuations often correlate with major axis currents wkb ray tracing models of propagating monochromatic plane waves exhibit horizontal phase propagation and correlations between minor axis currents and buoyancy and thus cannot explain these results models of near inertial internal waves reflected or trapped by a barotropic frontal jet produce mode like structures with short horizontal scales little horizontal phase propagation and anisotropic current ellipses aligned primarily cross front model buoyancy may correlate with one or both current ellipse components depending on the incidence angle of the wave and the degree to which it reflects completely reflected waves with horizontal scales similar to those of the front and near normal incidence angle produce current ellipses and correlation patterns consistent with the observations

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

a 4 ma record of thermal evolution in the tropical western pacific and its implications on climate change article i nfo orbital resolution thermal histories over the last 4 ma at odp site 1143 in the tropical western pacific are reconstructed using alkenone paleothermometry the temperature profile is characterized by a steady state of 29 c with fluctuations b1 c before 2 7 ma and by a strong oscillating state from 2 7 ma largely due to cooling by up to 4 c from 29 c in interglacial to 26 c in glacial intervals this implies a relative warm and stable surface hydrography during the early and mid pliocene in this region influenced by the warm pool before temperature decreases in responding to global cooling and the formation of the distinct glacial stages since the late pliocene therefore the smaller sst gradient between tropical eastern and western pacific and between southern and northern south china sea before the late pliocene indicates a super sized pliocene pacific warm pool while the larger sst gradient since then marks progressively intensification of the zonal walker circulation and meridional hadley circulation representing the monsoon circulations in the region the intensification of the walker and hadley circulations over the tropical pacific may also have helped on the onset of glaciations and subsequent deglaciations during the late pliocene and pleistocene 2011 published by elsevier b v

the influence of changing orbital parameters and surface boundary conditions on climate simulations for the past 18 000 years abstract general circulation model experiments at 3000 year intervals for the past 18 000 years were made to estimate the magnitude timing and pattern of the climatic response to prescribed changes of orbital parameters date of perihelion axial tilt eccentricity and glacial age lower boundary conditions ice sheets land albedo sea ice and sea surface temperature the experiments used the community climate model ccm of the national center for atmospheric research ncar the response of monsoon circulations and tropical precipitation to the orbitally produced solar radiation changes was much larger than the response to changes of glacial age boundary conditions the continental interior of eurasia was 2 4 k warmer in summer and summer monsoon precipitation of north africa south asia was increased by 10 20 between 12 000 and 6000 yr bp before present when perihelion occurred during northern summer rather than in winter as now and the earth s axial tilt was larger than now southern hemisphe

bundled turbidite deposition in the central pandora trough gulf of papua since last glacial maximum linking sediment nature and accumulation to sea level fluctuations at millennial timescale since last glacial maximum 23 19 ka earth climate warming and deglaciation occurred in two major steps bolling allerod and preboreal interrupted by a short cooling interval referred to as the younger dryas 12 5 11 5 ka b p in this study three cores mv 33 mv 66 and md 40 collected in the central part of pandora trough gulf of papua have been analyzed and they reveal a detailed sedimentary pattern at millennial timescale siliciclastic turbidites disappeared during the bolling allerod and preboreal intervals to systematically reoccur during the younger dryas interval subsequent to the final disappearance of the siliciclastic turbidites a calciturbidite occurred during meltwater pulse 1b the holocene interval was characterized by a lack of siliciclastic turbidites relatively high carbonate content and fine bank derived aragonitic sediment the observed millennial timescale sedimentary variability can be explained by sea level fluctuations during the last glacial maximum siliciclastic turbidites were numerous when the lowstand coastal system was located along the modern shelf edge although they did not occur during the intervals of maximum flooding of the shelf during meltwater pulses 1a and 1b siliciclastic turbidites reappear briefly during the younger dryas an interval when sea level rise slowed stopped or perhaps even fell the timing of the calciturbidite coincides with the first reflooding of eastern fields reef an atoll that remained exposed for most of the glacial stages

monsoon fluctuations over the past 350 kyr high resolution evidence from northeast asia northwest pacific climate proxies marine pollen and radiolarians abstract high resolution analyses of pollen and radiolarians from northwest pacific cores v28 304 and rc14 99 provide continuous directly linked evidence of oceanic atmospheric climate processes through the past three pleistocene glacial interglacial cycles systematic fluctuations in marine pollen assemblages which reflect changes in the forest communities of japan are compatible with fluctuations in faunal assemblages and inferred oceanographic properties offshore each interglacial has distinguishable characteristics which imply that the sequence timing and magnitude of climatic change were not identical during the three most recent interglacial intervals most interglacials contain at least one 10 15 kyr period of exceptionally high percentages 20 of cryptomeria which we interpret as reflecting increased levels of precipitation in response to intensification of the summer monsoon with the exception of oxygen isotope substage 5e in rc14 99 interglacial summer sea surface temperatures were similar to or slightly warmer than today glacial environments in central japan and in the northern subtropical gyre were similar to those which now support cold temperate and boreal forests on northernmost japan and a dominant subpolar fauna and associated low sea surface temperatures offshore climatic change was apparently not as severe in southern japan where temperate vegetation largely replaced warm temperate flora or in the southern subtropical gyre where only winter ssts were cooler than present we attribute these changes in vegetation and surface water conditions to shifts in the atmospheric polar and oceanographic subarctic fronts in response to the seasonal variations in the siberian high maxima in cryptomeria systematically lag maxima in solar insolation at 30 n this correlation between our summer monsoon indicator and summer insolation substantiates the view that the strength of the asian monsoon is linked to variations in northern hemisphere solar radiation

south china sea surface water evolution over the last 12 myr a south north comparison from ocean drilling program sites 1143 and 1146 1 planktonic foraminifera pf from ocean drilling program odp sites 1143 and 1146 in the southern and northern south china sea scs respectively were quantitatively analyzed in order to reconstruct the sea surface environment over the last 12 myr the observed decrease in deep dwelling pf species after 10 ma at both sites is interpreted to reflect a depression of the upper water thermocline corresponding to the closure of the indonesian seaway around 11 9 ma this upper water column structure implies the intensification of equatorial pacific warm currents and the initial formation of the western pacific warm pool wpwp during the early late miocene the consistent pattern of south north thermocline evolution and the synchronous disappearance of globoquadrina dehiscens 9 8 ma at both sites 1143 and 1146 together imply that the entire scs was likely under the influence of the newly developed wpwp at 10 ma after 8 ma sea surface temperatures and thermocline variations evolved differently between the southern and northern scs the total deep dwelling pf fauna at site 1143 decreased gradually in abundance from 6 6 to 2 ma indicating a deepening of the thermocline in the southern scs in contrast deep dwelling pf species increased in abundance from 3 1 to 2 ma at site 1146 reflecting a shoaling of the thermocline in the northern scs this south north contrast reflects two major environmental regimes 1 the southern scs which has mainly been under the influence of the wpwp since the late late miocene and 2 the northern scs where effects of the east asian winter monsoon have prevailed especially since the late pliocene estimate of past sea surface temperatures ssts at site 1143 suggests a relatively stable and warm environment in the southern scs since about 2 5 ma with an increased influence of warm subsurface waters after the mid pleistocene transition 1 2 0 9 ma in the northern scs however a gradual decrease in winter sst recorded at site 1146 over the last 4 myr records east asian monsoon evolution especially the enhancement of the east asian winter monsoon between 3 1 and 2 ma

hydroclimatic interpretation of quaternary shorelines on south australian playas abstract the catchment of lake eyre is one of the world s largest internally drained basins the playas near its depocentre the driest region of australia contain a partial record of quaternary climatic and hydrologic events for the last full glacial cycle and probably beyond ancient beach ridges marginal to lakes eyre frome callabonna and blanche have been dated using thermoluminescence tl to provide evidence for major changes in the hydrological regime of the basin beach ridges around lake eyre provide evidence of high lake stands up to 27 m above the present lake floor during what probably corresponds to the middle to latter part of marine oxygen isotope stage 5 there is evidence also for even higher lake stands associated with earlier isotope stages three tl dates identify a period of aeolian activity during stage 4 and a further 5 tl dates from lakes eyre and frome indicate that high lake stands occurred between about 55 and 40 ka corresponding with stage 3 the stage 5 and stage 3 high stands both relate to periods of enhanced fluvial activity previously identified in the lake eyre basin and elsewhere in australia in contradiction with other work a few tl dates from some playas suggest a possible major episode of high lake levels immediately preceding or at the start of the last glacial maximum lgm 26 22 ka this may relate to a sharp temperature suppression and an increase in runoff by rivers fed from monsoons in the north while a set of relatively low elevation late holocene beaches have been dated on two of the playas a period of enhanced precipitation and stream flow in the early to mid holocene appears not to have formed higher beaches possibly due to high temperatures and evaporation rates at that time the filling of lake eyre during and since stage 5 appears to have been to no more than to a level of 12 m australian height datum ahd possibly due a spillway at about this elevation in the form of the warrawoocara channel connecting lake eyre with playas to the southeast lakes gregory blanche callabonna and frome such overflows from one large basin to another would have had a major impact on the hydrology of the region in addition to enhanced runoff essential for the maintenance of high lake levels must have been local temperatures and evaporation rates significantly reduced from present day levels

contrast in surface water δ18o distributions between the last glacial maximum and the holocene in the southern south china sea abstract published core data of planktonic foraminiferal 18o and alkenone sea surface temperature sst are used to investigate seawater 18o w distributions in the south china sea scs during the last glacial maximum lgm and the holocene the holocene w distributions show a pattern correlated to modern salinity distributions displaying an increasing trend from the south to the north however the lgm w distributions show a different pattern displaying increasing values from the central to the southern scs and the lgm holocene differences in w w corrected by ice volume effect though negative in values display decreasing amplitude toward the south both of which could suggest increasing salinity toward the south by conventional approach this is somewhat counter intuitive because enhanced freshening could be expected for the southern scs due to extra discharge from the river systems on the emerged sunda land during the lgm here we propose an alternative explanation to reconcile the lgm w and w distributions with the above expectation in the proposal changes in w salinity relationship i e lowering the w salinity slope due to significant runoff contributions to freshwater input and less 18o depleted precipitation during the lgm are deeply discussed to reasonably explain the abnormity in lgm w distributions

the record of late pleistocene biogenic sedimentation in the eastern tropical pacific ocean we have generated 300 kyr records of biogenic opal calcite and organic carbon corg for three cores in the eastern and central equatorial pacific ocean and have compared the records to determine whether common periods of biogenic sedimentation have occurred throughout the region we find that corg has been deposited in common pulses throughout the area while opal has a much more local pattern of variation calcite varies regionally but the record is shaped by superimposed dissolution and productivity processes the most intense corg peak occurs at 18 ka and can have greater than 2 times the holocene corg content other major corg peaks occur 150 ka and perhaps at 280 ka we have compared the corg record in one of the cores v19 28 to a model deepwater oxygen record developed from 13c data in the nearby v19 30 to test whether the corg record has been mostly shaped by degradation or by the rain of organic matter from the euphotic zone we found no coherence between the two records implying that the corg record is primarily a measure of productivity by comparing the opal calcite and corg records in v19 28 a core which is at or above the lysocline we found that both increased calcite and opal deposition matches high corg accumulation we also found however that the calcite and opal records were uncorrelated so that episodes of high opal deposition do not necessarily accumulate calcite rapidly we hypothesize that at least two different plankton communities have been dominant in the waters above this site one rich in opal secreting plankton and one more dominated by calcite producers the opal rich plankton community was dominant during the intervals 10 15 ka and 35 60 ka supplement data table 2 is available with entire articleon microfiche order from american geophysical union 2000 florida avenue n w washington dc 20009 document p88001 2 50 payment must accompany order

sea surface temperatures of the southwest pacific ocean during the last glacial maximum the southwest pacific ocean covers a broad range of surface water conditions ranging from warm salty water in the subtropical east australian current to fresher cold water in the circumpolar current using a new database of planktonic foraminifera assemblages ausmat f2 we demonstrate that the modern analog technique can be used to accurately reconstruct the magnitude of sea surfacetemperature sst in this region we apply this technique to data from 29 deep sea cores along a meridional transect of the southwest pacific ocean to estimate the magnitude of sst cooling during the last glacial maximum we find minimal cooling in the tropics 0 2 c moderate cooling in the subtropical midlatitudes 2 6 c and maximum cooling to the southeast of new zealand 6 10 c the magnitude of cooling at the sea surface from the tropics to the temperate latitudes is found to generally be less than cooling at the surface of adjacent land masses

response of western pacific marginal seas to glacial cycles paleoceanographic and sedimentological features abstract this paper reviews the recent progress in late quaternary studies in five northwestern pacific marginal seas especially the south china sea as an example a series of marginal seas separate asia from the pacific ocean and significantly modify the material and energy flux linkage between land and sea during glacial cycles the sea level induced environmental signal was amplified in the marginal seas giving rise to drastic changes in areas and configurations of these seas and to reorganization of sea water circulation in basins since most of the western pacific marginal seas are influenced by monsoon circulation and some of these are located within the western pacific warm pool the glacial geographic changes have produced a profound impact on regional and global climate for example the decrease of sea area and sea surface temperature sst in the marginal seas was one of the factors responsible for the enhanced aridity of inland china during the glaciation glacial intensification of the winter monsoon and increased seasonality of sst in marginal seas might explain at least partly the apparent discrepancy between the tropical paleotemperature estimations based on terrestrial and open ocean records in this region as the western pacific marginal seas trap terrigenous material supplied by east asia the deep water sedimentation rates there can be one to two orders of magnitude higher than in the open ocean down slope sediment transport is more active when the sea level changes particularly during the deglaciation at least four types of carbonate cycles have been recognized in the western pacific marginal seas and each of those contains environmental signals from the surface and deep sea water as well as from the drainage basin

seasonal variability in the δ18o and δ13c of planktonic foraminifera from an upwelling environment sediment trap results from the san pedro basin southern california bight stable isotopic analyses 18o and 13crpar on four species of planktonic foraminifera collected from high resolution time series sediment trap sampling indicate that rapid and significant seasonal variability occurred in response to rapid changes in both the hydrographic environment and the isotopic composition of ambient seawater specimens were collected at a depth of 500 m for 28 consecutive 1 week periods in the san pedro basin within the southern california bight a region seasonally influenced by upwelling hydrographic monitoring of the study area revealed a 6 week period late april to mid june during which pulses of upwelling occurred causing significant increases in the oxygen isotopic composition of surrounding waters while decreasing the carbon isotopic composition analyses of globigerina bulloides orbulina universa neogloboquadrina dutertrei and neogloboquadrina pachyderma right coiling indicate that during the upwelling period these species live respectively at the surface in the surface mixed layer within the thermocline and below the thermocline globigerina bulloides ascends from well below the thermocline to the surface at the onset of upwelling and increases production to its maximum simultaneously as its morphology changes to less calcified open forms both n dutertrei and n pachyderma follow isothermal ranges migrating to shallower waters during upwelling and subsequently descending after upwelling ceases neogloboquadrina dutertrei appears to inhabit the region associated with both the thermocline base and chlorophyll maximum when it is most abundant following upwelling orbulina universa increases its depth habitat as solar irradiance increases but this species decreases in abundance during upwelling the 18o signal of o universa appears to be a useful indicator of seasonal temperature variations above the thermocline whereas the 18o of g bulloides documents near surface temperatures during upwelling the 13c signal of both n dutertrei and n pachyderma appears to record the 13c of equilibrium calcite for the regions of the thermocline and just below the thermocline respectively due to the relative preservation potentials of the four species analyzed only n dutertrei and n pachyderma are likely to be preserved in the sedimentary record in regions of oxygenated bottom waters thus an actual record of hydrographic conditions during upwelling as would be found in tests of g bulloides is not preserved instead conditions before n pachyderma and just after n dutertrei are more likely recorded

oxygen isotope constraints on surface ocean temperatures published oxygen isotope results from benthic and planktonic foraminifera are used to constrain the extent to which surface ocean temperatures in the tropics changed between glacial and interglacial time the possible impacts of bioturbation and of the redistribution of 18o16o ratios within the sea putting aside the oxygen isotope results are consistent with the climap project conclusion that tropical ocean temperatures remained within 2 c of their present value

variations of the last glacial warm pool sea surface temperature contrasts between the open western pacific and south china sea 1 high resolution paleoceanographic records from the southern south china sea scs and the tropical open western pacific reveal multicentennial to millennial scale variations of the western pacific warm pool wpwp over the last 40 kyr during the last glacial maximum lgm in marine isotope stage mis 2 planktonic globigerinoides sacculifer do 18 in core ns93 5 from the southern scs and in core wp92 5 from the central wpwp registered a similar average value of about 1 5p however the average do 18 value was about 0 5p more negative in the scs than in the central wpwp as was their difference before and after the lgm in the later part of mis 3 and early portion of mis 1 these results indicate weaker monsoonal and fluvial effects on the southern scs during the last glacial than during pleniglacial and postglacial periods owing to different oceanic circulation modes and regional topography the calculated seasonal temperature differences of summer and winter sea surface temperatures ssts between the open wpwp and the southern scs were up to 3 4 5 d c during the lgm but only slightly over 3 d c in the southern scs and less than 2 d c in the open wpwp during other periods from about 29 to 25 ka the mis 2 3 transition was marked by a sudden sst increase in the southern scs but a decrease in the open wpwp over this 4 kyr period the average annual sst appeared to be only 28 d c in the central wpwp but more than 28 d c in the southern scs indicating a shift of the central wpwp toward the far west during that time furthermore our results imply a period of nearly 6 kyr from 22 5 to 16 5 ka without an apparent warm pool of 28 d c in the western pacific

sea surface temperature reconstruction for the middle okinawa trough during the last glacial interglacial cycle using c37 unsaturated alkenones c 37 unsaturated alkenones were analyzed on a core retrieved from the middle okinawa trough the calculated u 37 k displays a trend generally parallel with those of the oxygen isotopic compositions of two planktonic foraminiferal species neogloboquadrina dutertrei and globigerinoides sacculifer suggesting that in this region sst has varied in phase with global ice volume change since the last glacial interglacial cycle the u 37 k derived sst ranged from ca 24 0 to 27 5 degrees c with the highest value 27 5 degrees c occurring in marine isotope stage 5 and the lowest similar to 24 0 degrees c in marine isotope stage 2 this trend is consistent with the continental records from the east asian monsoon domain and the marine records from the equatorial pacific the deglacial increase of the u 37 k derived sst is similar to 2 4 degrees c from the last glacial maximum to the holocene c 2007 elsevier b v all rights reserved

planktonic foraminifera in the western north pacific during the past 150 000 years comparison of modern and fossil assemblages abstract planktonic foraminiferal abundance variations in 186 deep sea piston core tops from the western north pacific were used to create a calibration set to characterize the present day kuroshio gyre system q mode factor analysis helped identify six faunal assemblages 93 variance related to modern water masses two tropical assemblages differing in relative dissolution three assemblages representing subtropical subpolar and transitional conditions and a gyre margin assemblage lying between the kuroshio current and the mainland of asia multivariate regression produced transfer functions relating observed summer august and winter february sea surface temperatures sst to the assemblages with standard errors of estimate of 1 5 c and 2 5 c respectively data from 24 piston cores was used to interpret variations of the kuroshio gyre system during the past 150 000 yr stratigraphic control is based on oxygen isotopic measurements the extinction of pink pigmented globigerinoides ruber at 120 000 b p coiling direction changes in neogloboquadrina pachyderma north of 30 n and dissolution variations between resistant and fragile taxa major dynamic changes in the circulation of the kuroshio gyre occurred during the last two glacial maxima at 15 20 000 b p isotopic stage 2 and at 140 150 000 b p isotopic stage 6 these intervals are characterized by 1 lowered sea levels which reduced flow into the sea of japan and sea of okh okhotsk 2 advance of the polar front from its modern position at about 42 n to 35 38 n 3 southward penetration of the oyashio current along the pacific coast of japan to tokyo 4 2 3 c lowered sst in tropical areas little or no change in subtropical areas and a 4 6 c decrease in transitional areas and 5 an overall decrease in carbonate dissolution relative to interglacial stages the maximum interglacial at 120 000 b p isotopic substage 5e shows a retreat of the polar front north of its modern position and an overall relative increase in interglacial carbonate dissolution that does not become severe until substage 5d

tasman front shifts and associated paleoceanographic changes during the last 250 000 years foraminiferal evidence from the lord howe rise abstract the paleoceanography of the tasman sea over the past 250 000 years was studied using benthic 75 m size fraction and planktonic foraminifera 149 m size fraction from three cores collected along 162 e traverse between 25 s and 30 s on the lord howe rise planktonic foraminiferal oxygen isotope stratigraphy dates the cores between ois 1 and 11 r mode cluster and q mode factor analyses were carried out on benthic foraminiferal faunas and q mode factor analysis and the modern analog technique mat were used in analyzing planktonic foraminiferal faunas distinct benthic faunas across latitude from north 25 s to south 30 s and 35 s reflects the difference in primary productivity level in the overlying surface water the mat result is thought to express latitudinal shifts of the tasman front over the last 250 000 years with 1 the tasman front at 35 s during the oxygen isotope stage ois 1 post glacial period 2 migration of the front nearby 25 s during the last glacial period ois 2 ois 4 and slightly northward of its present position during the penultimate glacial period ois 6 and 3 a return of the front to near 35 s during ois 5 and ois 7 based on time series and spatial variations of benthic foraminiferal factor typified by pseudoparrella exigua and uvigerina peregrina and one variety southern winter mixing and convection along the tasman front may have strengthened during the interglacial ois 7 in particular

heinrich event imprints in the okinawa trough evidence from oxygen isotope and planktonic foraminifera planktonic foraminiferal faunas oxygen isotope and modern analog technique sea surface temperature records were obtained in piston core dgks9603 28degrees08 869 n 127degrees16 238 e water depth 1100 in collected from the middle okinawa trough during the last glaciation four cold events were identified and correlate heinrich events he h2 5 of the last 45 ka during the last deglaciation core dgks9603 has begun to be influenced by the kuroshio since about 16 cal ka bp three weakenings of this warm current occurred at about 2 8 5 3 11 4 and 15 5 cal ka bp respectively among the three fluctuations the oldest one is synchronous with he1 and could be a response to the strong cooling observed in the north atlantic ocean the fluctuation occurring at about 11 4 cal ka ago corresponds to the younger dryas within the age error bars our observations provide new evidence that the hes documented from greenland and the northern north atlantic had a global climatic impact changes in the intensity of the east asian monsoon could be the main mechanism responsible for the paleoccanographic variations observed in the okinawa trough c 2001 elsevier science b v all rights reserved

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

reconstructing organic matter sources and rain rates in the southern west pacific warm pool during the transition from the deglaciation period to early holocene abstract transient features in the organic carbon content of deep sea sediment cores resulting from changes in the flux and or quality of sedimentary organic matter are not uncommon we examined the geochemical characteristics of sediments retrieved with a gravity corer from the northwestern solomon sea 3908 m water depth southern west pacific warm pool wpwp 13c and 15n of sedimentary organic matter together with toc tn data suggest that the organic material is characterized by a mixture of marine and terrestrial origins with a higher contribution from marine algae the data were analyzed with an inverse non steady state reaction transport model to examine the variability and magnitude of particulate organic carbon poc flux to the seafloor during the transition between the deglaciation period and early holocene measured poc content and porewater no3 nh4 dic and so42 concentrations were used to constrain the model hindcast results revealed that poc flux decreased from 75 to 37 5 g cm 2 yr 1 during the deglaciation early holocene transition the rate of poc degradation in the present setting is slightly lower compared to that in the pre holocene setting the synchronous decline in the relative contribution of terrestrial organic matter input and rapid sea level rise during this transition suggest that sea level rather than surface productivity is the dominant factor controlling the poc deposition flux in the solomon sea this is conceivable because the sampling site is proximal to high relief islands with high rainfall a well developed submarine canyon system and narrow and steep continental margins consequently we suggest that deep water basins in proximity to similar high relief mountainous islands in the tropical pacific may represent important sinks for terrestrial organic material especially during sea level lowstands

tropical pacific ocean thermocline depth reconstructions for the last glacial maximum we evaluate the relationship between ten surface ocean 0 300 m hydrographic parameters and the spatial distribution of factor analyzed core top planktonic foraminiferal abundances in the tropical pacific ocean 24 n 24 s for core tops 3800 m the spatial distribution of the first three faunal factor loadings 88 of the variance are most highly correlated to subsurface variability mixed layer depth thermocline depth and resistant species percent rsp however rsp is not related to dissolution but is related to thermocline depth factor i mixed layer species g glutinata g ruber and factor iii g ruber can be distinguished from each other by low abundances of g glutinata in factor iii both assemblages spatially comprise the deep mixed layer region of the western tropical and equatorial pacific ocean but are associated with distinct water mass properties a combination of factor i and iii loadings shows a higher correlation to thermocline depth r 0 70 factor ii loadings dominated by thermocline dwelling species n dutertrei are most significantly correlated with the thermocline depth r 0 73 most factors show only marginally significant correlation to sea surface temperatures ssts indicating that sst is not the primary forcing factor on the planktonic foraminiferal species distributions in the tropical pacific a new transfer function was calculated to predict tropical pacific thermocline depth from planktonic foraminifera abundances using the imbrie kipp method ikm standard deviation of residuals 22 m 1 an additional 5 m error is attributed to low species counts in the core top database the modern analog technique mat was also used to predict thermocline depth standard deviation of residuals 21 m while last glacial maximum lgm thermocline depth changes by ikm and mat were generally within error estimated changes were geographically uniform suggesting an oceanographic response to climate forcing we estimate that the thermocline depth of the lgm was shallower than present by 20 m south of 8 s possibly due to a shift in the south pacific anticyclone to the northeast both the ikm and mat estimate a steeper east west thermocline slope along the equator suggesting that zonal wind stress walker circulation was intensified during the lgm collectively the thermocline estimates for the lgm suggest an equatorward compression of the climate zones in both hemispheres

toward establishing a maritime proxy record of the east asian summer monsoons for the late quaternary abstract an astronomically tuned late quaternary planktic foraminiferal 18o record of site md972142 12 41 33 n 119 27 90 e 1557 m water depth in the southeastern south china sea was established the difference in 18o between md972142 and odp792 of the sulu sea is regarded as a maritime proxy of the summer monsoon intensity over the south china sea and southeast asia the profile of this maritime proxy matches well with the summer monsoon index obtained from the terrestrial record of louchuan central chinese loess plateau the amplified planktic 18o signals of the south china sea relative to the sulu sea record are partly caused by the changing intensities of the east asian monsoons at the glacial interglacial time scale throughout the late quaternary

a millennial scale u37k sea surface temperature record from the south china sea 8 n over the last 150 kyr monsoon and sea level influence we report 150 kyr records of u37 sea surface temperature sst and carbonate content with 150 200 year sampling resolution from the southern south china sea scs in the northern margin of the western pacific warm pool wpwp using images core md972151 the glacial interglacial sst change is about 5 c for termination ii 23 5 to 28 5 c and 4 c for termination i 24 to 28 c the simultaneous rise of sea level and u37 sst during termination i suggests that sea level change has played an important role in the scs sst variability by influencing the exchange of tropical ocean warm surface water with the scs through the sunda shelf region sill depth 30 50 m when sea level drop was less than 30 m relative to today s md972151 sst was constantly above 27 c a situation which occurred during mis 5e part of mis5c and 5a and over the last 11 kyr sea level change was also the main control on carbonate content in the scs this was lower during low sea level stands due to the dilution effect of enhanced terrigenous inputs within the limitations of our age model millennial scale sst oscillations 1 5 c over a few hundred years occurred frequently during the entire glacial period correlating reasonably well with the hulu monsoon record from eastern china and the dansgaard oeschger d o cycles recorded for high latitude regions in the northern hemisphere such correlations suggest a possible teleconnection between higher latitude atmospheric forcing and low latitude climate oscillations in the western pacific tropical region via the asian monsoon system carbonate content also reveals millennial scale oscillations during the glacial period with higher content correlated with higher sst millennial scale fluctuations of sst and carbonate contents at this low latitude scs provide additional evidence that high frequency climate changes are global phenomena

oxygen isotope record of sea level and climate variations in the sulu sea over the past 150 000 years the sulu sea is located in the warm pool of the western pacific ocean where mean annual temperatures are the highest of anywhere on earth because this large heat source supplies the atmosphere with a significant portion of its water vapour and latent heat understanding the climate history of the region is important for reconstructing global palaeoclimate and for predicting future climate change changes in the oxygen isotope composition of planktonic foraminifera from sulu sea sediments have previously been shown to reflect changes in the planetary ice volume at glacial interglacial and millenial timeseales and such records have been obtained for the late pleistocene epoch and the last deglaciation1 3 here i present results that extend the millenial time resolution record back to 150 000 years before present on timescales of around 10 000 years the sulu sea oxygen isotope record matches changes in sea level deduced from coral terraces on the huon peninsula4 this is particularly the case during isotope stage 3 an interglacial period 23 000 to 58 000 years ago where the sulu sea oxygen isotope record deviates from the specmap deep ocean oxygen isotope record5 thus these results support the idea4 6 that there were higher sea levels and less continental ice during stage 3 than the specmap record implies and that sea level during this interglacial was just 40 50 metres below present levels the subsequent rate of increase in continental ice volume during the return to full glacial conditions was correspondingly faster than previously thought

a high resolution record of sea surface temperature in southern okinawa trough for the past 15 000 years abstract the study of long chain alkenones in the ocean drilling program odp core 1202b reveals a sub centennial resolution record of sea surface temperature sst in the southern okinawa trough for the past 15 thousand years kyr from the deglaciation to holocene sst varied from 21 1 to 26 5 c the presence of bolling 15 0 14 2 kyr bp and allerod 13 7 13 4 kyr bp warming phases older dryas 14 2 13 7 kyr bp and younger dryas 12 8 11 6 kyr bp cold periods reflects a tight teleconnection of climate between the okinawa trough and the north atlantic region in the last deglaciation after rapidly increased and reached the maximum at 7 4 kyr bp sst in the southern ot gradually decreased corresponding with the lowering of northern hemisphere summer solar insolation however a series of abrupt sst drops were identified at ca 8 6 8 1 5 8 4 8 4 1 3 9 3 0 2 5 1 6 1 3 and 0 6 0 5 kyr bp which cannot be explained by solar insolation changes alone and instead are mediated by a complex sun ocean atmosphere coupling

upwelling and productivity changes inferred from a temperature record in the central equatorial pacific a series of c37 39 alkenones synthesized by prymnesiophyte algae is commonly preserved in marine sediments and can be used for estimating past sea surface temperatures ssts 1 2 here we present an alkenone analysis of sediments taken from the central equatorial pacific ocean core w8402a 14gc 0 57 n 138 57 w which shows that sst varied slightly 2 c but coherently with milankovitch insolation cycles over the past 250 kyr the in phase response of the sst to the precessional component of insolation indicates that this part of the sst time series may be driven by changes in local trade wind strength and the longer 100 kyr eccentricity component indicates a response to basin wide south pacific winds using a simple heat balance model we use our palaeotemperature record to constrain the upwelling rates that have occurred in the past similar sst records from the eastern pacific could constrain the horizontal advection component of the sst record and allow for better estimates of upwelling upwelling and palaeoproductivity then could be compared to determine whether changes in equatorial nutrient levels actually cause equivalent changes in productivity

planktonic foraminiferal assemblages preserved in surface sediments correspond to multiple environment variables abstract here we investigate the relationships between modern planktonic foraminiferal species assemblages from atlantic and pacific core top sediment samples and 35 water column and preservation properties using canonical correspondence analysis cca cca finds two faunal dimensions axes that are most highly correlated to the environmental variables and describes each axis in terms of the best linear combination of environmental variables cca axis 1 30 4 of the faunal variance is related primarily to mean annual sea surface temperature sst r 0 96 cca axis 2 7 9 of the faunal variance is related to environmental variability associated with an inverse relationship between sst and surface salinity as well as pycnocline phosphate concentrations the seasonal range in nitrate concentrations water depth and chlorophyll concentrations at the sea surface based on this clustering of nutrient and chlorophyll on axis 2 we infer an ecological response to oceanic fertility no evidence is found for a unique dissolution influence suggesting that sea floor carbonate ion concentration cannot be estimated reliably from planktonic foraminiferal assemblages our results support the use of foraminiferal assemblages to estimate mean annual sst

a 30 000 year record of extreme floods in tropical australia from relict plunge pool deposits implications for future climate change relict plunge pool sedimentary sequences provide much longer paleoflood records than normally provided by slackwater deposits and other previously reported paleoflood sedimentary signatures the only two relict plunge pool sedimentary sequences so far reported lie 300 km apart in tropical northern australia and provide a record of extreme floods for the last 30 000 years each of these sequences identify the early to mid holocene and the period immediately prior to the last glacial maximum as the two periods of greatest flood magnitudes of the late quaternary flood discharges at these times were up to five times greater than any floods experienced over the last 4 000 years most climate models predict that the magnitude and frequency of storms and rainfall events will increase under a warmer greenhouse climate the plunge pool sedimentary sequences however show that periods of greatly enhanced discharge compared to present can be associated with both warm wet and cool wet phases of climate

timing of late quaternary productivity pulses in the panama basin and implications for atmospheric co2 high resolution percent corg and 18oforam records obtained from panama basin core atlantis ii 54 25pc and additional data from nearby core p7 show that enhanced burial of organic carbon has characterized every major glacial period for the last 500 kyr in that area both corg concentration and mass accumulation rate profiles exhibit a sawtooth pattern with maxima occurring typically in the later stages of glacial periods comparison with dust records suggests that the carbon accumulation rate profile reflects both the upwelling history and a variable rate of iron input during the late quaternary the sawtooth character may derive from increased wind velocities and rates of upwelling during glacials which are indirectly related to ice volume sarnthein et al 1988 the rapid decline in export production at the end of glacials in the equatorial pacific may be attributed to the retreat of ice sheets thus reduced wind velocities and upwelling coupled with a coincident decline in atmospheric dust load and or delivery rate the corg accumulation rate profiles do not correlate well with atmospheric co2 records for example atmospheric co2 was already at a minimum 40 kyr ago when production in the panama basin began increasing dramatically commensurate with an increase in global dust levels using the relationship between the degree of photosynthetic fractionation and the concentration of free co2 in the surface ocean postulated by popp et al 1989 13corg measurements made on core p7 show that panama basin surface waters have been supplying co2 to the atmosphere continually for at least the last 50 kyr there is no evidence for a flux of co2 into the surface ocean in this area at any time during this period despite the higher production if the panama basin cores are representative of the eastern and central equatorial pacific then these observations weaken the influence on co2 drawdown postulated for increased glacial productivity at low latitudes

environmental processes of the ice age land oceans glaciers epilog knowledge of the state of the earth at the last glacial maximum lgm an interval around 21 000 years ago is an important benchmark for understanding the sensitivity of global environmental systems to change much progress in understanding climates of the lgm has occurred in the 20 years since the end of the climap project of the 1970s climate long range investigation mapping and prediction here we review this progress based on presentations and discussion at a rst open science meeting of the epilog project environmental processes of the ice age land oceans glaciers held in delmenhorst germany may 1999 we outline key controversies and document protocols for epilog contributions so that a new synthesis of the lgm earth can emerge as an open project of the world s community of scientists 2001 elsevier science ltd all rights reserved

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

tropical vegetational change in the late pleistocene of new caledonia the south eastern plateau of new caledonia 22 s preserves remnants of a deep regolith of ultramafic soils which is extensively gullied or eroded to form large alluvial fans dated sediments from four closed basins on the plaine des lacs ca 220 m altitude show that organic muds were accumulating prior to 30 000 yr b p over the next 5000 14 000 years limonitic clays infilled two basins as a result of slope instability in their catchment resistant laterite and bog iron surfaces became exposed during the period 30 000 15 000 yr b p by erosional events that seem to have been of greater magnitude than any in the earlier pleistocene two sites lake emeric and lake suprin were chosen for pollen analysis during the phases of organic deposition of these lakes nothofagus forests collapsed several times and were replaced by gymnostoma maquis apparently as a result of fires these pleistocene fires were associated with some inorganic deposition presumably due to the substantial loss of primary forest cover regeneration of forest usually followed after an estimated gap of several centuries thus fire was able to cause forest retreats of the same order of magnitude as that caused by massive fires today the low nutritional status of the soils or lateritic crusts means that as now forest had difficulty reclaiming sites human activity is unknown prior to 3000 years ago so the major erosion is presumed to have had natural causes thus many of the wide ranging changes are the result of natural instability in the sub tropics and some may be much older than hitherto thought climate change towards periods of dry fire prone conditions may have been an underlying cause in the holocene some climatic factor possibly cyclonic storms seems to prevent organic sedimentation switching from cyclone free to cyclone prone at the end of the pleistocene may reflect temperature change in sea surfaces in the region

forward modelling of the sequence stratigraphic architecture of shelf cyclothems application to late pliocene sequences wanganui basin new zealand we demonstrate a procedure for forward modelling of the sequence stratigraphic architecture i e positions of systems tract boundaries of shelf cyclothems as observed at outcrop sites or in well logs the 1 d model is based on the fact that the deposition of facies within shelf sequences and those defining the key stratigraphic surfaces between systems tracts respond directly to changes in depth between the sea surface and seafloor this accommodation bathymetry model incorporates three reference surfaces sea surface seafloor and lower sequence boundary each of which varies independently as a result of changes in the rates of eustatic sea level sedimentation and subsidence the model input and boundary conditions are an eustatic sea level curve i e late cenozoic deep sea 18o record an independent chronology for the outcrop or well section and a subsidence curve the model outputs are changes in accommodation and palaeobathymetry throughout the sequence and the time missing at erosional sequence boundaries the main variable in the model i e sedimentation rate is established by comparison of a model output bathymetry with the model target palaeobathymetry established from the faunal and facies content of the sequence being modelled when the model output and target are compatible the model sedimentation rate curve is adopted and the theoretical positions of the systems tract boundaries can be read off the model in relation to the lower sequence boundary and compared with independent field based interpretations of their stratigraphic position the model is designed to predict the architecture of sequences as they appear at particular outcrop sites or in well sections its usefulness lies in establishing the timing of accumulation of systems tracts in relation to stages in a eustatic sea level cycle in particular distinguishing between units deposited during highstand versus regressive systems tracts the model is applied to 6th order 41 ka plio pleistocene cyclothems in wanganui basin new zealand where it distinguishes the boundary between highstand systems tracts hst and regressive systems tracts rst the modelling has implications for the definition of systems tracts especially in late cenozoic successions for which the record of eustatic sea level changes is known independently

a late quaternary pollen record from ka au crater o ahu hawai i abstract a pollen record from ka au crater o ahu hawai i contains evidence for changes in vegetation and climate since about 28 000 14c yr b p zone 1 ca 28 100 ca 22 800 14c yr b p has pollen of dry to mesic forest species including pipturus type dodonaea viscosa acacia koa chenopodium oahuense claoxylon sandwicense myrsine and metrosideros type in zone 2 ca 22 800 ca 16 200 14c yr b p myrsine and coprosma increase with herbs fern allies and grammitidaceae suggesting open canopies zone 3 ca 16 200 ca 9700 14c yr b p has pollen of wet forest species including freycinetia arborea abundant pritchardia and metrosideros type zone 4 ca 9700 ca 7000 14c yr b p is similar with less pritchardia and more metrosideros type climate reconstruction was based on modern climatic ranges of flowering plants and an index derived from abundance of pollen in surface samples both methods agree on a qualitative reconstruction although the ages are poorly constrained 28 000 25 000 14c yr b p cool and dry 25 000 23 000 14c yr b p dry and warmer 23 000 20 000 14c yr b p moderately dry with declining temperature 20 000 16 000 14c yr b p moderately dry and cool 16 000 9000 14c yr b p warm and wet 9000 7000 14c yr b p warm and possibly drier lower precipitation at ka au crater during the late glacial period and last glacial maximum is consistent with the interpretation that the north pacific subtropical anticyclone was south of its present position the pollen derived temperature index yields an estimate of 3 5 c temperature depression during the last glacial maximum

sea surface temperature estimates for the tropical western pacific during the last glaciation and their implications for the pacific warm pool twenty deep sea sediment cores from the western pacific between 30 n and 30 s provide evidence of sea surface temperature sst changes throughout the tropics and subtropics glacial ssts were estimated using the modern analog technique mat applied to planktonic foraminifers and planktonic foraminiferal 18o changes we used 18o to identify the last glacial maximum the mat method differs from the traditional transfer function approach in that it utilizes a global coretop database and estimates paleotemperature by finding analogs from the modern coretop samples in addition the mat approach appears to be less susceptible than the transfer function technique to biases introduced by carbonate dissolution our results indicate that tropical ssts differed by less than 2 c from present away from the tropics 30 n and 30 s ssts were at least 3 c cooler our results differ from those of previous studies in the western pacific by using a set of well preserved high sedimentation rate cores from shallow regions the results of this study clearly indicate that a western pacific warm pool existed during the last glacial maximum lgm providing a heat and moisture source for a walker circulation cell similar to that of today we propose that a steeper lapse rate existed during the last glacial maximum and that this can explain at least part of the discrepancy between marine and terrestrial temperature estimates adjacent to new guinea for the lgm

late pleistocene and early holocene glaciations in taiwanese mountains abstract the high mountain range of taiwan is unglaciated at present but numerous glacial landforms and sediments in three mountain massifs the nanhuta shan the hsueh shan and the yushan support the concept of repeated glaciations of these areas during the pleistocene and early holocene optically stimulated luminescence osl data derived from glacial and glacier related sediments suggests a glaciation about 8 9 0 5 ka called the nanhuta glacier advance which could be correlated either to the younger dryas or the global 8 2 ka cooling event alley et al 1997 holocene climatic instability a prominent widespread event 8200 yr ago geology 25 6 483 486 absolute data from pre holocene sediments are still rare although glacial evidence valley shape erratic boulders glacial trimlines and sediments indicates a larger extent of valley glaciers during the pleistocene

low latitude glacial cooling in the southern hemisphere from amino acid racemization in emu eggshells the record of natural climate variability over glacial interglacial timescales provides a framework from which a better mechanistic understanding of the climate system may be derived but this approach is limited by the number and distribution of well dated and reliable palaeoenvironmental archives particularly vexing is the conflicting evidence for low latitude cooling during the last glacial maximum and the apparent synchrony in glacial activity between the hemispheres despite out of phase insolation forcing1 4 here we utilize the temperature dependent amino acid racemization reaction in radiocarbon dated emu eggshell fragments from the continental interior of australia to reconstruct low altitude subtropical temperatures for the past 45 kyr racemization rate changes indicate that millennial scale average air temperatures were at least 9 c lower between 45 and 16 kyr bp than since 16 kyr bp a temperature change of this magnitude coupled with other low latitude palaeotemperature records that indicate substantial cooling3 4 must reflect global processes which we speculate involved glacial age reduction in atmospheric water vapour content

shallow water carbonates record marginal to open ocean quaternary paleoceanographic evolution 1 the oxygen and carbon isotopic composition of shallow water carbonates and their fossil components can be important tools for understanding quaternary paleoceanographic conditions of marginal seas including coral reef regions however most previous paleoceanographic studies using isotopes have been based on pelagic or hemipelagic sediments because the original 1 8 o and 1 3 c values of shallow water carbonates are normally altered by postdepositional diagenesis this study shows that marginal to open ocean isotopic signals can be preserved in carefully cleaned low mg calcitic planktic foraminifers of shallow water carbonates even when the isotopic values of the carbonate host rock have been altered by meteoric fluids and subaerial exposure the two studied core sections were collected from the mid quaternary ryukyu group southwestern japan which consists mainly of bioclastic grainstone packstone rhodolith floatstone rudstone and large foraminiferal floatstone corresponding to open shelf to shelf slope facies from the southwest ryukyu islands japan down core 1 8 o records of planktic foraminifers in the ryukyu group imply that sea surface temperatures sst in the northwestern pacific increased 2 0 c at the beginning of oxygen isotope stage 19 post mid pleistocene revolution mpr this warming may have triggered the expansion of reef complex deposits as large as those now in the ryukyu islands and was approximately coeval with the lower section of the australian great barrier reef sst warming due to the expansion of the western pacific warm pool wpwp toward the north and south subtropical regions is a possible mechanism for reef expansion and initiation of the coral reefs of the western pacific region

late quaternary palaeoecology palynology and palaeolimnology of a tropical lowland swamp rawa danau west java indonesia abstract sedimentological limnological and palynological analyses of a sediment core from a lowland site in west java indonesia provide a detailed palaeoenvironmental record for the late glacial and the holocene the record suggests open vegetation under inferred drier climatic conditions for the late glacial however there is no unequivocal evidence for cooler conditions at this time the onset of the holocene coincides with a change to more humid climatic conditions with the development of a fern rich closed forest vegetation type dramatic changes in diatom community composition provide a striking record of habitat change associated with lake shallowing but this process appears to be a result of basin in filling rather than variations in precipitation evaporation balance associated with climatic fluctuations evidence for human impact on the vegetation development is restricted to the last few hundred years

foraminiferal responses to major pleistocene paleoceanographic changes in the southern south china sea a detailed age model for core 17957 2 of the southern south china sea was developed based on delta 18 o coarse fraction magnetostratigraphy and biostratigraphy for the last 1500 kyr the delta 18 o record has clear similar to 100 kyr cycles after the mid pleistocene revolution mpr at the entrance of marine isotopic stage mis 22 planktonic foraminifera responded to the mpr immediately showing the increased sea surface temperature sst and dissolution after the mpr benthic foraminifera did not respond to it until the brunhes matuyama boundary since the mpr the depth of thermocline gradually became shallower until miss 6 5 this major change within miss 6 5 was also reflected in the decreased ssts and increased productivity and deep water mass thus two major pleistocene paleoceanographic changes were found one was around the mpr the other occurred within miss 6 5 which speculatively might be ascribed to the reorganization of surface and deep circulation possibly induced by tectonic forces

environmental change in the late pleistocene and later holocene at wanda site soroako south sulawesi indonesia abstract this paper reports the pollen analysis of an 8 m core from a mire at 445 m altitude and 2 s latitude on ultramafic soils near the western shore of lake matano south sulawesi the area is almost undisturbed by humans and the record is believed to cover about 50 75 000 yr b p with some breaks in the record a section from 17 000 to around 5500 yr b p and the last 1000 years of the record may be missing or disturbed the results show that montane forest grew around the site continuously through the late pleistocene with a maximum increase in higher altitude taxa from 35 000 to after 17 000 yr b p the time of glacial maxima elsewhere also in this period increases in grass and casuarina indicate possible drier conditions the holocene sections record lower altitude forest with increased taxonomic diversity including secondary species the results show that vegetation in the region has been sensitive to climatic change the pleistocene ecology being consistent with a temperature change of about 2 5 3 5 c with a phase up to 50 drier than present the site climate was possibly affected by shelf exposure in the gulf of bone due to lower sea levels however the tropical forest demonstrates overall long term stability in which changes in dominance may reflect minor shifts in disturbance and tree longevity a distinctive record of fine charcoal occurs throughout the deposit this shows that the forest has never been continuously fire free for a very long time the cause of the fires may be natural as no evidence for human occupation was discerned

high resolution windows into early holocene climate srca coral records from the huon peninsula high precision measurements of srca ratios are reported for porites corals from the uplifted holocene coral terraces at huon peninsula papua new guinea the early holocene porites have u th mass spectrometric ages of 8920 60 yr and 7370 50 yr and 234u t values of 145 2 similar to modern seawater the srca coral records provide 5 6 year high resolution near weekly time windows into early holocene sea surface temperatures seasonal temperature fluctuations are generally in the range of 1 c with occasional excursions of 2 c which may indicate the more frequent recurrence of very strong enso el nino southern oscillation events mean annual srca temperatures of 24 2 1 1 c and 22 9 0 8 c have been obtained which are 2 3 c cooler than that exhibited by a modern porites these results indicate that during the early holocene the equatorial western pacific ocean was at least several degrees cooler than present day temperatures this is consistent with late glacial coral records from the caribbean that indicate lower 6 c sea surface temperatures for the equatorial oceans the huon peninsula corals also indicate that ssts were several degrees cooler than those in the caribbean during the early holocene thus although the northern hemisphere summer radiation maximum occurred at 10 ka there appears to have been a significant lag in the response of the equatorial western pacific ocean to this warming cooler early holocene sea surface temperatures in the western pacific may have been due to changing patterns of ocean atmosphere circulation resulting from the exposure of large areas of continental shelf in the southeast asia region a consequence of lower glacial sea levels it is likely that ocean temperatures in the huon peninsula were influenced by the opening at 7 ka of the torres strait that now separates new guinea from the australian mainland

quantitative interpretation of fossil pollen spectra dissimilarity coefficients and the method of modern analogs abstract dissimilarity coefficients measure the difference between multivariate samples and provide a quantitative aid to the identification of modern analogs for fossil pollen samples how eight coefficients responded to differences among modern pollen samples from eastern north america was tested these coefficients represent three different classes 1 unweighted coefficients that are most strongly influenced by large valued pollen types 2 equal weight coefficients that weight all pollen types equally but can be too sensitive to variations among rare types and 3 signal0to noise coefficients that are intermediate in their weighting of pollen types the studies with modern pollen allowed definition of critical values for each coefficient which when not exceeded indicate that two pollen samples originate from the same vegetation region dissimilarity coefficients were used to compare modern and fossil pollen samples and modern samples so similar to fossil samples were found that most of three late quaternary pollen diagrams could be reconstructed by substituting modern samples for fossil samples when the coefficients indicated that the fossil spectra had no modern analogs then the reconstructed diagrams did not match all aspects of the originals no modern analogs existed for samples from before 9300 yr b p at kirchner marsh minnesota and from before 11 000 yr b p at wintergreen lake michigan but modern analogs existed for almost all holocene samples from these two sites and brandreth bog new york

pulleniatina obliquiloculata as a paleoceanographic indicator in the southern okinawa trough during the last 20 000 years abstract pulleniatina obliquiloculata a tropical species of planktonic foraminifera is indicative of the kuroshio current and sensitive to winter sea surface temperature for the late quaternary in the okinawa trough its relative abundance fluctuations are significant and correlatable between three gravity cores cores 255 170 253 raised from the southern okinawa trough four major changes in its abundances with paleoceanographic significance have been recognized during the last 20 000 years an abrupt increase at the pleistocene holocene boundary a short term decrease indicative of a younger dryas type climate reversal at about 11 4 9 6 ka b p the p obliquiloculata maximum zone around 7 6 ka b p corresponding to the mid holocene climate optimum and the p obliquiloculata minimum zone around 4 2 ka b p correlated probably to the neoglacial cooling the widespread occurrence of these events in the western pacific and the correlated variations of its abundance between sea areas suggest that p obliquiloculata is well promising as a paleoceanographic and climatic monitor for high resolution reconstruction and sea land correlation

tropical sea surface temperatures and the earth s orbital eccentricity cycles the tropical oceanic warm pools are climatologically important regions because their sea surface temperatures ssts are positively related to atmospheric greenhouse effect and the cumulonimbus cirrus cloud anvil such a warm pool is also present in the central tropical indian ocean paleo ssts estimated by the radiolarian transfer functions for the last 200 1400 kiloyears ka in a deep sea sediment core from this warm pool fluctuated within 2 75 c 26 14 28 89 c around the threshold temperature 27 c for the super greenhouse effect it is possible that this sst variation might have led to the corresponding fluctuation in the greenhouse effect and the cirrus cloud anvil in the geological past these paleo ssts also exhibited cyclicities at 100 and 400 ka corresponding to the earth s orbital eccentricity cycles results therefore imply that the tropical indian ocean warm pool persisted during the quaternary and the paleo ssts fluctuating at the orbital eccentricity frequencies might have modulated the intensity of greenhouse effect

constraints on the amplitude of mid pliocene 3 6 2 4 ma eustatic sea level fluctuations from the new zealand shallow marine sediment record ice volume calibrations of the deep ocean foraminiferal delta18o record imply orbitally influenced sea level fluctuations of up to 30m amplitude during the mid pliocene and up to 30 per cent loss of the present day mass of the east antarctic ice sheet eais assuming complete deglaciation of the west antarctic ice sheet wais and greenland these sea level oscillations have driven recurrent transgressions and regressions across the world s continental shelves wanganui basin new zealand contains the most complete shallow marine late neogene stratigraphic record in the form of a continuous cyclostratigraphy representing every 41 and 100ka sea level cycle since ca 3 6ma this paper presents a synthesis of faunally derived palaeobathymetric data for shallow marine sedimentary cycles corresponding to marine isotope stages m2 100 ca 3 4 2 4ma our approach estimates the eustatic sea level contribution to the palaeobathymetry curve by placing constraints on total subsidence and decompacted sediment accumulation the sea level estimates are consistent with those from delta18o curves and numerical ice sheet models and imply a significant sensitivity of the wais and the coastal margins of the eais to orbital oscillations in insolation during the mid pliocene period of relative global warmth sea level oscillations of 10 30m were paced by obliquity

palaeoenvironmental change in tropical australasia over the last 30 000 years a synthesis by the oz intimate group the tropics are the major source of heat and moisture for the australasian region determining the tropics response over time to changes in climate forcing mechanisms such as summer insolation and the effects of relative sea level on exposed continental shelves during the last glacial period is an ongoing process of re evaluation we present a synthesis of climate proxy data from tropical australasia spanning the last 30 000 years that incorporates deep sea core coral speleothem pollen charcoal and terrestrial sedimentary records today seasonal variability is governed largely by the annual migration of the inter tropical convergence zone itcz influencing this region most strongly during the austral summer however the position of the itcz has varied through time towards the end of marine isotope stage mis 3 conditions were far wetter throughout the region becoming drier first in the south universally cooler land and sea surface temperature sst were characteristic of the last glacial maximum with drier conditions than previously although episodic wet periods are noted in the fluvial records of northern australia the deglacial period saw warming first in the coral sea and then the indonesian seas with a pause in this trend around the time of the antarctic cold reversal c 14 5 ka coincident with the flooding of the sunda shelf wetter conditions occurred first in indonesia around 17 ka and northern australia after 14 ka the early holocene saw a peak in marine sst to the northwest and northeast of australia modern vegetation was first established on indonesia then progressively south and eastward to ne australia flores and the atherton tablelands show a dry period around 11 6 ka steadily becoming wetter through the early holocene the mid late holocene was punctuated by millennial scale variability associated with the el nino southern oscillation this is evident in the marine coral speleothem and pollen records of the region

paleobiogeographical implications of inner bay ostracoda during the late pleistocene shimosueyoshi transgression central japan with significance of its migration and disappearance in eastern asia abstract a total of 79 ostracode species were recognized from the embayment sediments deposited during the late pleistocene shimosueyoshi transgression in central japan the most dominant species was neomonoceratina delicata now abundant in tropical inner bays of the ryukyu islands the south china sea and southeastern asia bicornucythere bisanensis widely dominant species in enclosed middle muddy bays of temperate climatic zones in japan and northern china was also abundant in the middle and upper sequences most of the other main species were assigned to the japonic elements and are presently common in tropical or subtropical and temperate shallow seas near the japanese islands four ostracode biofacies were identified using the q mode cluster analysis a change in water depth was clearly revealed in the study sequence based on the vertical changes in the biofacies and the relative abundances of fossil ostracode species the single most dominant species n delicata does not currently exist in the japanese islands north of the tokara strait watase s line one of zoological lines of demarcation in southern japan based on a compilation of fossil and recent distribution records it is believed that n delicata migrated from the south of the tokara strait by the marine oxygen isotope stage mis 11 430 ka dominated other species in enclosed muddy bays and then spread to the northernmost areas during the mis 5 however almost all populations of this species probably disappeared north of the tokara strait during the last glacial maximum due to a decrease in water temperature this species could not survive colder water temperature and could not migrate north through the tokara strait during the postglacial transgression because the strait has been deep and wide since the early pleistocene we conclude that this species lived commonly during the glacial stages of mis 10 8 and 6 north of the tokara strait because of the favorable water temperature for reproduction

variation of foraminiferal sr ca over quaternary glacial interglacial cycles evidence for changes in mean ocean sr ca 1 records of sr ca changes in planktonic and benthic foraminifera from diverse hydrographic settings reveal coherent variability 5 1 between ocean basins and between surface and deep waters over the past 300 kyr there is a general increase in foraminiferal sr ca over the penultimate glaciation declining to minimum values during stage 5 and an increase in sr ca from stage 5 through stage 2 coincident changes in benthic foraminifera records from the atlantic and pacific basins imply that sr ca variations are not dominated by dissolution planktonic culturing data provide evidence that the downcore sr ca variations are not controlled by temperature changes and suggest only a small influence of salinity and ph variation common to the records is most readily explained by changes in mean ocean sr ca if fossil foraminifera reliably record higher glacial seawater sr ca coral sr paleothermometry would underestimate sea surface temperature during glacialepisodes

palaeoceanographic change in the northeastern south china sea during the last 15000 years the sedimentary succession of piston core rc26 16 dated by 14 c accelerator mass spectrometry provides a nearly continuous palaeoceanographic record of the northeastern south china sea for the last 15 000 yr planktic foraminiferal assemblages indicate that winter sea surface temperatures ssts rose from 18 c to about 24 c from the last glacial to the holocene a short lived cooling of 1 c in winter temperature centred at about 11 000 14 cy r ago may reflect the younger dryas cooling event in this area summer ssts have remained between 27 c and 29 c throughout the record the temperature difference between summer and winter was about ca 9 c during the last glacial much higher than the holocene value of ca 5 c during the late holocene a short lived cooling event occurred at about 4000 14 cy r ago oxygen and carbon isotopic gradients between surface 0 50 m and subsurface 50 100 m waters were smaller during the last glacial than those in the holocene the fluctuation in the isotopic gradients are caused most likely by changes in upwelling intensity smaller gradients indicate stronger upwelling during the glacial winter monsoon the fauna derived estimates of nutrient content of the surface waters indicate that the upwelling induced higher fertility and biological productivity during the glacial the winter monsoon became weaker during the holocene the carbonate compensation depth and foraminiferal lysocline were shallower during the holocene except for a short lived deepening at about 5000 14 c yr ago a preservation peak of planktic foraminifera and calcium carbonate occurred between 13400 and 12 000 14 c

fabric analysis in rocks of the gadag region southern india implications for time relationship between regional deformation and gold mineralization abstract in this paper the fabric in archaean age massive metabasalts and granite from the gadag region western dharwar craton southern india are identified using the anisotropy of magnetic susceptibility ams the magnetic foliation in the rocks is dominantly nw se striking this is inferred to have developed during regional d1 d2 deformation known to have affected the region which was on account of ne sw shortening the plunge of the magnetic lineation varies from nw to se this doubly plunging orientation is inferred to be a consequence of superimposition of nw se shortening d3 deformation over the earlier structure that is known to have resulted in dome basin geometry in the surrounding metapelitic rocks of the region thus it is concluded that the massive rocks preserve evidence of superposed deformation that affected the region which can be deciphered from the orientation of magnetic fabric data the gadag region comprises lode gold deposit 2500 ma in age and field investigations show that the quartz veins are dilational with dominantly nw se strike orientation the veins are inferred to have formed by dilation under nw se shortening during d3 it is envisaged that the nw se oriented fabric that formed in the metabasalt during d1 d2 channelized fluid flow thus leading to vein emplacement during d3 it is concluded that gold deposition in the veins took place during d3 which is related to the final stages of cratonization of the dharwar craton at 2500 ma

paleoceanography for the last 195 000 years in the solomon sea odp site 1109 by means of calcareous nannofossils abstract the paleoceanography of the solomon sea for the last 195 000 years was investigated based on the observations of 21 taxonomic groups of calcareous nannofossils in 144 samples taken from ocean drilling program odp cores 1109a 1h and 1109c 2h oxygen isotope ratios in tests of the planktonic foraminifer globigerinoides ruber allow us to assign the cores to oxygen isotope stages 7 1 past sea surface temperatures sst were estimated qualitatively using the composition of three gephyrocapsa coccolith morphotypes the high intermediate and low angle types that are classified based on the bridge angle of coccolith can be used as proxies for warm intermediate and cold temperatures respectively abundance of the high angle type coccoliths increased and decreased during the interglacial and glacial periods respectively this tendency is consistent with the expected change of the western pacific warm pool wpwp development however a large shift in the abundance of the high angle type coccolith recorded during early stage 3 did not correspond to the oxygen isotope record the ratio of small

terrestrial conditions at the last glacial maximum and climap sea surface temperature estimates are they consistent climap 1981 seasonal reconstruction of the earth s surface at the last glacial maximum geological society of america map and chart series mc 36 boundary conditions were used as inputs to the giss general circulation model and the last glacial maximum lgm climate was simulated for six model years the simulation was compared with snow line depression and pollen inferred temperature data at low latitudes specifically for hawaii colombia east africa and new guinea the model does not produced as much cooling at low latitudes as is implied by the terrestrial evidence an alternative experiment in which the climap sea surface temperatures were uniformly lowered by 2 c produces a better fit to the land data although in hawaii model temperatures are still too warm the relatively warm climap tropical sea surface temperatures also provide for only a slight decrease in the hydrologic cycle in the model in contrast to both evidence of lgm tropical aridity and the results of the experiment with colder ocean temperatures with the climap sea surface temperatures the lgm global annual mean surface air temperature is 3 6 c colder than at present if the ocean temperatures were allowed to cool in conformity with the model s radiation balance the lgm simulation would be 5 6 c colder than today and in better agreement with the tropical land evidence

late quaternary vegetation change in the tari basin papua new guinea the changes in late quaternary vegetation at two sites in the tari basin central highlands of new guinea are presented haeapugua basin 1650 m altitude and tugupugua basin 2300 m altitude lie within the lower montane forest belt where the climate is characterised by high relative humidity and low seasonality pollen analysis mineral magnetics carbonised particle analysis and dating by radiocarbon and thermoluminescence techniques are employed to reconstruct the vegetation and sediment history the sequences include fragmentary interglacial interstadial records from before 50 000 yr b p and a continuous record from at least 28 000 yr b p to the present the study shows that prior to 21 000 yr b p vegetation in the basin was dominated by fluctuating proportions of tree taxa indicative of a forested environment the montane forest taxon nothofagus is important throughout the record although other tree taxa including castanopsis myrtaceae dacrydium and pandanus attain dominance at different times under the influence of a range of environmental factors the creation of an open environment around 21 000 yr b p is considered to be a consequence of the arrival of humans in the region the late glacial transition between 14 500 and 8500 yr b p is a period of climatic instability with landscape and vegetation adjustments proceeding at different rates across the highlands vegetational adjustments match modern ranges by about 8500 yr b p when swamp forest developed across the sites at the lower altitude site there are indications of anthropogenic forest disturbance associated with swamp forest clearance commencing around 1700 yr b p and intensifying through to the present forest clearance is recorded only after 700 yr b p at the higher site where agriculture was probably only sustainable after the introduction of sweet potato ipomoea batatas

the age and origin of the younger dryas climate event in greenland ice cores 230th 234u and 14c dating of barbados corals has extended the calibration of 14c years b p to calendar years b p beyond the 9200 year tree ring series bard et al 1990 this now permits the conversion of 14c chronozones which delimit major climate shifts in western europe to calendar years the younger dryas chronozone defined as 11 000 to 10 000 14c years b p corresponds to 13 000 to 11 700 calendar years b p this calibration affects the interpretation of an intensely studied example of the younger dryas climate event the 18o anomaly between 1785 and 1793 m in dye 3 ice core the end of the 18o anomaly in dye 3 ice core has been dated by measurements of 14c in air bubbles andree et al 1984 1986 and by annual layer counting hammer et al 1986 the older 14c dates fall out of the range of the tree ring calibration series but can now be calibrated to calendar years using the barbados 230th 234u calibration the 14ccorrected age for the end of the 18o event is 10 300 400 calendar years b p compared to the annual layer counting age of 10 720 150 years b p thus the younger dryas event in the dye 3 ice core ends in the preboreal chronozone 11 700 to 10 000 calendar years b p and is not correlative with the end of the younger dryas event identified in pollen records marking european vegetation changes the end of the dye 3 18o event is however correlative with the end of meltwater pulse ib fairbanks 1989 marking a period of intense deglaciation with meltwater discharge rates exceeding 13 000 km yr

cooling of the south china sea by the toba eruption and correlation with other climate proxies 71 000 years ago the toba tephra layer has been identified in core md972151 in the southern south china sea scs northeast of the indonesia toba caldera this affords us an opportunity to directly determine a 1 c cooling for ca 1 kyr on the scs following the toba eruption 71 ka during the marine isotope stage 5a 4 transition using century scale sea surface temperature records this cooling event in the scs is well correlated with several coeval proxies such as increased east asia winter monsoon intensity increased ice rafted detritus in the north pacific ocean sediments and decreased 18 o in greenland ice core such correlation suggests a climate change where cold climate signals originated in the northern hemisphere ice sheets transferred southward by the winter monsoon and cooled the scs

asian summer monsoon instability during the past 60 000 years magnetic susceptibility and pedogenic evidence from the western chinese loess plateau abstract the 28 m high resolution shajinping loess section in lanzhou on the western chinese loess plateau records a 60 ka millennial summer monsoon variation the record shows that asian summer monsoons have rapid episodic pulse enhancements spanning only ca 1 2 ka in high frequency domain and having sub milankovitch cycles of progressive weakening in low frequency domain in the last glaciation soil formation seems to occur with a surprisingly fast response to these summer monsoon enhancements resulting in weakly or moderately developed paleosol sequences both the pattern and timing of the summer monsoon enhancements show that they can be correlated to most major warm dansgaard oeschger episodes and long term cooling bond cycles of the north atlantic climatic records indicating a possible teleconnection between tropic oceanic air masses and the north atlantic climatic system but differences exist for the transition of mis 2 3 and the holocene where extraordinarily heavy dust input events and fairly variable climatic fluctuations occur for the former and latter respectively a westerlies swing model is proposed to interpret this link

glacial paleoceanography off the mouth of the mekong river southern south china sea during the last 500 ka we have analyzed core md01 2392 similar to 360 km east of the mekong river mouth in the south china sea scs over the past 500 ka planktonic foraminiferal oxygen isotopic values are consistently lighter than northern scs and open ocean records by up to 0 5 parts per thousand indicating the influence of run off from the mekong river during both glacial and interglacial periods carbonate content is higher during interglacials sedimentation rates were higher during glacials increased sedimentation rates since 30 ka imply increased run off during the last glacial maximum and holocene period contrary to general experience in which it is classed as a warm species for temperature estimates the thermocline dwelling species pulleniatina obliquiloculata increased its numbers during glacial periods this implies an estuarine circulation and even brackish water caps during glacial periods reinforcing the sense of strong run off in an overall decline of warm water the thermocline shoaled stepwise with rapid rises across the glacial terminations we infer that the southern scs was opened to an influx of indian ocean waters through southern passages at those times of rising sea levels c 2010 university of washington published by elsevier inc all rights reserved

estimates of sea surface temperature in the coral sea at the last glacial maximum the climap 1981 reconstruction of the coral sea found relatively little cooling 2 c in the low latitudes 10 s but a warming off australia at about 25 s the small low latitude changes are of interest because terrestrial pollen and snowline data from the new guinea highlands imply that surface temperatures may have been 6 to 9 c colder at the last glacial maximum lgm the purpose of this paper is to evaluate these conclusions on the basis of additional core sites new oxygen isotope stratigraphy and new sea surface temperature sst estimates using the modern analog technique mat in the northern coral sea planktonic foraminifer assemblages consist of tropical subtropical species that show little change over the past 20 kyr quantitative estimates of sst using the modern analog technique mat confirm the climap 1981 conclusion that little or no temperature change occurred in this tropical region at the lgm thus reinforcing the conflict with terrestrial evidence in the southern region 25 s two cores indicate that foraminifer faunas became more subtropical at the lgm the mat estimates for the lgm are 3 to 4 c colder than modern producing a steeper thermal gradient in the southern coral sea these data remove the warm sst anomaly along the eastern coast of australia and indicate that during the lgm cool high latitude waters were displaced northward along the coast of australia into the southern coral sea

reconstruction of the east china sea palaeoenvironment at 16 ka by comparison of fossil and modern faviidae corals from the ryukyus southwestern japan we conducted paired measurements of the sr ca ratio and oxygen and carbon stable isotopes of a fossil faviidae coral specimen myk90 age 16 ka collected from near miyako island the ryukyus southwestern japan our study aimed to reconstruct the palaeoenvironment in the east china sea at 16 ka by comparing the fossil sample with modern faviidae corals our data with annual or longer time resolution may be very suitable for palaeoceanographic reconstruction although no general calibration method for faviidae corals has been reported our calibration showed that the annual mean sea surface temperature was approximately 5 c lower and sea surface salinity sss at the study site was locally higher at 16 ka than at present even though the mouths of the yellow and changjiang rivers were east of their present locations because sea level was much lower our results suggest that the influence of the terrestrial water discharge may not have extended to miyako island weak summer monsoon activity during the last glacial which decreased summer precipitation over the asian continent and an enhanced winter monsoon which may have led to more evaporation likely contributed to the inferred high sss at the study site copyright 2009 john wiley sons ltd

late quaternary atmospheric and oceanographic variations in the western pacific inferred from pollen and radiolarian analyses abstract pollen and radiolarian analyses of sediment from four piston cores located along a south north transect 28 44 n off the east coast of japan yield detailed records of variations in terrestrial and marine climate of this region for the last 140 ka the last interglacial climate of the southern half of japan was characterized by increased temperature and precipitation at least across central japan compared with today off southern japan surface were cooler during summer than at present off central japan both summer and winter sea surface temperatures were cooler than today early glacial 115 71 ka bp climate across central and southern japan alternated between wet and dry warm temperate with surface waters offshore warmer in summer and winter than during the penultimate interglacial temperatures and precipitation in japan reached low levels early during the full glacial phase and remained relatively low throughout much of the full glacial 71 14 ka bp cold sea surface temperatures at all our sites coincided with these cold conditions on land temperatures across much of japan began to increase steadily during the deglacial with surface waters offshore remaining at or near their glacial lows holocene vegetation patterns which continued to reflect an increase in temperature reached a maximum during early to mid holocene surface waters offshore however remained relatively cool during the early holocene with temperature maxima at most western pacific sites occurring in mid to late holocene we propose specific changes in the seasonal positions of atmospheric pressure cells to explain these climate variations that have occurred across the northeast asian northwest pacific region through the most recent interglacial glacial cycle results of this exercise show that there are no major discrepancies between climate reconstructions for mainland japan inferred from pollen and those for the western pacific derived from radiolarians

calcite dissolution and the modification of planktonic foraminiferal assemblages abstract the results of an in situ experiment in the panama basin allow us to determine the way in which planktonic foraminiferal assemblages are modified by calcite dissolution pre weighed planktonic foraminiferal samples of known species composition were attached to a deep sea mooring at various water depths between 665 m and 3791 m for a period of 123 days weight loss due to dissolution during this period ranged from less than 5 for the shallowest samples to slightly over 30 for the deepest samples in terms of change in foraminiferal number this is equivalent to decreases of between 1 and 26 only in the samples placed at the two deepest levels 3769 m and 3791 m was there a significant loss in the total number of foraminifera the magnitude of change in the abundance of individual species in early related to their different susceptibilities to dissolution species such as hastigerina pelagica globigerinella aequilateralis and candeina nitida which are very susceptible to dissolution exhibited the largest decreases in frequency percentage while the more resistent species sphaeroidinella dehiscens pulleniatina obliquiloculata and globorotalia truncatulinoides had minimal changes from these results a solution susceptibility ranking for planktonic foraminifera is established that is quite similar to those derived from previous laboratory experiments and sea floor studies

spatial and temporal variability of surface water in the kuroshio source region pacific ocean over the past 21 000 years evidence from planktonic foraminifera abstract the kuroshio current is the major western boundary current of the north pacific ocean and has had a large impact on surface water character and climate change in the northwestern pacific region the kuroshio current becomes a distinctive surface flow in the ryukyu arc region after diverging from the north equatorial current and passing through the okinawa trough therefore the ryukyu arc area can be called the kuroshio source region we reconstructed post 21 ka time space changes in surface water masses in the ryukyu arc region using 15 piston cores which were dated by planktonic 18 o stratigraphy and ams 14 c ages our analysis utilized spatial and temporal changes in planktonic foraminiferal assemblages which were classified into the kuroshio subtropical coastal and cold water groups on the basis of modern faunal distributions in the study region these results indicate that the kuroshio current and adjacent surface water masses experienced major changes during 1 the last glacial maximum lgm and 2 the so called pulleniatina minimum event pme from 4 500 to 3 000 yr bp the kuroshio lgm event corresponds to severe global cooling and is marked by decreases in planktonic 18 o values and estimated sea surface temperature sst with the dominance of the cold water group of planktonic foraminifera cooling within the kuroshio source region was enhanced during the lgm event because the kuroshio current was forced eastward due to the formation of a land bridge between taiwan and the southern ryukyu arc which prohibited its flow into the okinawa trough except for the severe reduction and disappearance of the pulleniatina group no clear cooling signal was identified during the pme based on 18 o values estimated sst values and variations in the composition of planktonic foraminiferal faunas the pme assemblages are marked by high abundances of neogloboquadrina dutertrei a distinctive kuroshio type species along with other species assigned to the coastal and central water groups subtle ecological differences exist between pulleniatina obliquiloculata and n dutertrei i e p obliquiloculata exhibits lower rates of reproduction under conditions of lower primary productivity in the central equatorial pacific ocean el nino like conditions in the equatorial pacific ocean result in lower rates of surface transport in the kuroshio current in turn this response triggers lower rates of primary productivity in central equatorial surface waters as well as in the upstream kuroshio source region ultimately resulting in a lower abundance of p obliquiloculata thus we interpret the pme as a possible proxy signal of el nino like conditions and enhancement of the el nino southern oscillation climate system after the pme in the tropical and sub tropical pacific ocean