climate instability during the last interglacial period recorded in the grip ice core isotope and chemical analyses of the grip ice core from summit central greenland reveal that climate in greenland during the last interglacial period was characterized by a series of severe cold periods which began extremely rapidly and lasted from decades to centuries as the last interglacial seems to have been slightly warmer than the present one its unstable climate raises questions about the effects of future global warming

u th ages obtained by mass spectrometry in corals from barbados sea level during the past 130 000 years the study of the sea level record during the last glacial cycle has primarily proceeded indirectly by means of oxygen isotope measurements on foraminifera from deep sea sediments1 2 the direct approach of dating sea level indicators stagnated during the past decade mainly because the samples required to complete our knowledge of the past glaciations are below the present day sea level3 7 using the 14c ages of acropora palmata samples collected by drilling offshore the island of barbados fairbanks8 presented the first detailed chronology for the last deglaciation this radiocarbon chronology is limited to the past 30 kyr because of the short half life of 14c 5 730 yr we must therefore rely on other dating methods to obtain information for the whole last glacial cycle during the past four years 230th 234u dating of corals by thermal ionization mass spectrometry has been shown to be significantly more precise and accurate than the classical counting method9 14 we have used this technique to measure u th ages in coral samples from the barbados collection and from subaerially exposed outcrops see also ref 15 here we present results bearing on the sea level record for the past 130 000 years we conclude that the last deglaciation started 3 000 years earlier than previously thought and confirm that there were two surges in melt water8 at about 11 kyr and 14 kyr bp before present

climate records covering the last deglaciation the oxygen 18 oxygen 16 ratio of molecular oxygen trapped in ice cores provides a time stratigraphic marker for transferring the absolute chronology for the greenland ice sheet project gisp ii ice core to the vostok and byrd ice cores in antarctica comparison of the climate records from these cores suggests that near the beginning of the last deglaciation warming in antarctica began approximately 3000 years before the onset of the warm bolling period in greenland atmospheric carbon dioxide and methane concentrations began to rise 2000 to 3000 years before the warming began in greenland and must have contributed to deglaciation and warming of temperate and boreal regions in the northern hemisphere

oxygen isotopes and sea level from the time that detailed oxygen isotope records derived from foraminifera living in the constant temperature environment of the abyssal ocean became available there has been a discrepancy between the ice volume record that these records imply and that derived from the altitude of dated coral terraces around the world here we re examine the data and conclude that the temperature of the abyssal ocean has been an actively varying component of the climate system

climate correlations between greenland and antarctica during the past 100 000 years the ice cores recovered from central greenland by the grip1 2 and gisp23 projects record 22 interstadial warm events during the part of the last glaciation spanning 20 105 kyr before present the ice core from vostok east antarctica records nine interstadials during this period4 5 here we explore links between greenland and antarctic climate during the last glaciation using a high resolution chronology derived by correlating oxygen isotope data for trapped o2 in the gisp2 and vostok cores we find that interstadials occurred in east antarctica whenever those in greenland lasted longer than 2 000 years our results suggest that partial deglaciation and changes in ocean circulation are partly responsible for the climate teleconnection between greenland and antarctica ice older than 115 kyr in the gisp2 core shows rapid variations in the 18o of o2 that have no counterpart in the vostok record the age depth relationship and thus the climate record in this part of the gisp2 core appears to be significantly disturbed

geomagnetic paleointensity dating of south china sea sediments for the last 130 kyr relative paleointensity records from the northern south china sea northwest pacific ocean were studied in two gravity piston cores continuous mineral magnetic and paleomagnetic measurements were made using discrete sediment samples detailed rock magnetic parameters such as thermomagnetic and high field hysteresis data indicate that pseudo single domain magnetite in a narrow range of grain size and concentration is the main contributor to the remanent magnetization the uniform magnetic mineralogy meets the commonly accepted criteria for establishing relative paleointensity records the relative paleointensity rpi curves were constructed by normalizing the natural remanent magnetization nrm with isothermal remanent magnetization irm both in the 20 60 mt demagnetization state dating constraints have been provided by radiocarbon ages in the upper 400 cm of both cores furthermore we have correlated our paleointensity records with napis 75 s atlantic 1089 sint 200 and nopapis 250 to determine the chronological rpi framework for the south china sea scs pis although some temporal offsets of paleointensity features between the different records have been recognized their similar shape suggests that relative paleointensity on the 10 3 10 4 year scale is globally coherent and can provide an age framework for sediments independent of delta 18 o ages c 2009 elsevier b v all rights reserved

reconciliation of late quaternary sea levels derived from coral terraces at huon peninsula with deep sea oxygen isotope records a major discrepancy between the late quaternary sea level changes derived from raised coral reef terraces at the huon peninsula in papua new guinea and from oxygen isotopes in deep sea cores is resolved the two methods agree closely from 120 ka to 80 ka and from 20 ka to 0 ka ka 1000 yr before present but between 70 and 30 ka the isotopic sea levels are 20 40 m lower than the huon peninsula sea levels derived in earlier studies new high precision u series age measurements and revised stratigraphic data for huon peninsula terraces aged between 30 and 70 ka now give similar sea levels to those based on deep sea oxygen isotope data planktonic and benthic 18o data using the sea level and deep sea isotopic data oxygen isotope ratios are calculated for the northern continental ice sheets through the last glacial cycle and are consistent with results from greenland ice cores the record of ice volume changes through the last glacial cycle now appears to be reasonably complete

evidence for a younger dryas like cooling event on the british columbia coast two independent paleoclimatic records from the pacific coast of canada indicate that a late glacial warming trend was interrupted by a return to colder conditions between about 11 000 and 10 200 radiocarbon yr b p correlative with the classical younger dryas chronozone of the north atlantic region fossil benthic foramnifera from three cores from the continental shelf dated by accelerator mass spectrometry show peak abundances of the cold water indicator species cassidulina reniforme at this time fossil pollen spectra from two sites on the queen charlotte islands record a shift from forest to open herb rich vegetation after 11 100 yr b p probably in response to colder and wetter conditions identified by pollen climate transfer functions these preliminary data for a cold oscillation between ca 11000 and 10000 yr ago in the northeast pacific argue that this deglacial phenomenon was not restricted to the north atlantic but was a hemispheric and possibly global event

the late pleistocene history of surface water δ13c in the sulu sea possible relationship to pacific deepwater δ13c changes a reconstruction of late pleistocene surface water carbon isotopic 13c variability is presented from ocean drilling program odp site 769 in the sulu sea in the western tropical pacific the sulu sea is a shallowly silled back arc basin with a maximum sill depth of 420 m site 769 was drilled on a bathymetric high in 3643 m of water and has average late pleistocene sedimentation rates of 8 5 cm kyr the oxygen isotope record 18o of globigerinoides ruber at site 769 shows a strong correlation with the specmap stacked 18o record attesting to the continuity of sediment archive at the site surface 13c displays consistent glacial interglacial variability which averages 0 9 and has varied from 0 75 to 1 1 over the last 800 kyr comparison to surface water 13c records in the south china sea and western tropical pacific suggests that the glacial interglacial surface 13c variability is regional in scale planktonic 13c data from odp site 677 in the eastern pacific is also coherent with the site 769 additionally we have found that the site 769 surface 13c record is coherent at periods of 100 and 41 kyr with deepwater 13c records from the pacific the highest correlation occurs with the deep eastern pacific where benthic 13c data from cores rc13 110 and odp site 677 closely match the sulu sea surface water record we evaluate several possible controls of surface water 13c in the sulu sea that may explain the coherent timing with pacific deepwater 13c records these include variations in terrestrial organic matter flux to the basin the upwelling of subsurface water and productivity changes and the influx of western pacific intermediate water to the sulu sea our preferred explanation involves a region of upper intermediate water upwelling in the far western pacific which has been shown to outgas co2 from subsurface waters into surface waters upwelling also occurs in the area of panama basin site 677 these equatorial upwelling zones could potentially provide a route by which pacific intermediate water can modulate the 13c composition of certain pacific surface water locations future reconstructions of late pleistocene surface water 13c variability in the western pacific and indonesian seas will be required to further evaluate the source of the glacial interglacial surface water 13c change

oxygen minimum expansion in the sulu sea western equatorial pacific during the last glacial low stand of sea level the sulu sea in the western equatorial pacific is presently a shallowly silled dysaerobic deep marine basin deep waters in the sulu sea are ventilated through a single sill at 420 m depth which connects it to the china sea benthic and planktonic foraminiferal oxygen and carbon isotope records benthic and planktonic foraminiferal census data and total organic carbon measurements have been used to evaluate changes in water mass conditions in the sulu sea between the last glacial maximum 18 000 yrs b p and the present day an increase in the abundance of the planktonic foraminiferaneogloboquadrina dutertrei and relatively light planktonic foraminiferal 18o values suggest that during the last glacial maximum surface water salinities were reduced in the sulu sea enhanced isolation of the basin due to glacio eustatic lowering of sea level and reduced surface salinities resulted in stagnation of deep water and an expansion of the mid water oxygen minimum layer increased organic carbon preservation at mid water depths occurs at this time benthic carbon isotope data and an increase in the abundance of benthic foraminiferal species considered to prefer low oxygen environments support the conclusion of an oxygen minimum expansion at mid water depths during the last glacial maximum at water depths greater than 4000 m bottom waters appear to have maintained some degree of oxygenation during the last glacial maximum stronger pacific ocean trade winds at this time may have caused the influx of denser celebes sea surface water into the southern part of the sulu sea the slow sinking of this water would have then ventilated bottom waters in this part of the basin at the transition from glacial to interglacial conditions rising sea level caused denser water to flow over the deepest sill into the sulu sea vertical circulation increased resulting in a greater downward flux of oxygen and a dissipation of the oxygen minimum continued post glacial sea level rise caused periodic ventilation of deep water until the present dysaerobic conditions were established

a coastal reservoir of terrestrial resources for neanderthal populations in north eastern iberia palaeoenvironmental data inferred from the small vertebrate assemblage of cova del gegant sitges barcelona coastal areas as reservoirs of resources for hominid groups have been widely studied in recent years these areas combine marine with terrestrial and wetland resources and would have been optimum sites for hominids including neanderthals this is the case with the cova del gegant a cave that today opens directly onto the mediterranean sea and is located in the north eastern iberian peninsula the geomorphological evolution of the massis del garraf has provided evidence that during the late pleistocene there was a littoral platform between 8 and 13 km wide in front of the cova del gegant within this framework the data derived from analysis of the small vertebrates and large mammals recovered from cova del gegant including taxa currently absent from the massis del garraf suggest that the landscape surrounding the cave provided a richer terrestrial ecosystem for neanderthals than is available in this zone today analysis of the small vertebrate association from the cave reveals that the landscape surrounding the cave was dominated by woodland edge and open environments and that the climate was mediterranean the results have been compared with the only iberian site with similar characteristics to the cova del gegant gorham s cave southern iberia gibraltar revealing differences and similarities in the landscape and climate on the basis of the small mammal assemblages as well as the differences in the accessibility to terrestrial mammalian resources for the neanderthal groups the landscape and the climate were reasonably similar at the two sites but the differences in the accessibility of resources for the neanderthals are directly related to the location of the sites and the coastal position whereas the cova del gegant was on a route of mammal migration between the ebro valley and france suited for securing terrestrial resources gorham s cave is located on a small peninsula with a lower abundance of terrestrial mammal resources this is probably why the neanderthal groups at gorham s cave exploited marine resources whereas there is no evidence of marine resources having been exploited at cova del gegant even though the seashore was nearby copyright 2011 john wiley sons ltd

climate variations in europe over the past 140 kyr deduced from rock magnetism rapid shifts in climate during the last glacial are now well documented particularly from the oxygen isotope records of the two greenland ice cores grip1 2 and gisp23 in the grip record1 2 these climate events are also seen during the preceding eemian interglacial which may be an analogue for the future climate warmed by the greenhouse effect but these shifts are not found in the eemian section of the gisp2 core3 casting doubt on whether the rapid shifts in the grip oxygen isotope record really do represent a climate signal here we present magnetic susceptibility pollen and organic carbon records from maar lake deposits in the massif central france these data provide an independent record of past climate and we find that they correlate well with the ice core records during the last glacial during the eemian two rapid cooling events seen in our record also correlate with those seen in the grip ice core supporting the idea that rapid climate change did occur in the eemian interglacial and demonstrating that it extended to continental europe

reply to comment by k pedoja et al on tectonic record of strain buildup and abrupt coseismic stress release across the northwestern peru coastal plain shelf and continental slope during the past 200 kyr citation bourgois j d bourles and r braucher 2011 reply to comment by k pedoja et al on tectonic record of strainbuildup and abrupt coseismic stress release across the northwestern peru coastal plain shelf and continental slope during the past200 kyr j geophys res 116 b09402 doi 10 1029 2011jb008582

western north atlantic evidence for millennial scale changes in ocean circulation and climate two late quaternary series of high resolution percent carbonate data from western north atlantic sediment drifts bermuda rise and bahama outer ridge show millennial scale oscillations superimposed on the familiar longer period oscillations of orbital origin the dominant high frequency oscillation in these records has a quasi period of about 4000 years these percent caco3 changes most likely result from the influence of climate change on the flux of terrigenous material from eastern canada the resuspension of continental margin sediment by deep eddy kinetic energy and carbonate dissolution sediment is transported to the bermuda rise by deep recirculating gyres and to the bahama outer ridge by the deep western boundary current system stable isotope results on foraminifera across several of these oscillations from interstadial climate conditions and from a glacial inception display variability similar to that of percent caco3 oxygen isotope ratios of planktonic foraminifera suggest large variations in near surface temperature and or salinity and carbon isotope ratios of benthic foraminifera indicate that there were significant oscillations in the flux of north atlantic deep water nadw these data support models which couple surface ocean conditions in the north atlantic production of nadw north atlantic heat flux and evidence for temperature oscillations in ice cores

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

dam break solution a closed form solution is obtained for a dam break problem in which the reservoir dam breach and downstream channel all have different widths the reservoir outflow is calculated by using a quasi steady flow approximation and downstream flood depths are calculated by using the kinematic wave approximation an investigation into the validity of these two approximations leads to constraints that must be placed upon applications of the solution a numerical example shows that maximum downstream flood depths decay relatively slowly because of storage contained within the upstream reservoir

the oxygen isotope composition of tropical ocean surface water during the last deglaciation evidence of abrupt climate change in each of the tropical oceans can be found in high deposition rate sediments from the continental margins new ams 14 c dated sediments from the arabian sea reveal a two step depletion of surface ocean 18 o 16 o during the last deglaciation with a return to more enriched values approximately 10 5 ka bp the two step depletion can be correlated among isotope records derived from foraminifer calcite in the arabian sea the gulf of mexico the sulu sea and gulf of california confirming the existence of the two step depletion and 18 o enriched event at 10 5 ka bp in at least three tropical sites outside the north atlantic to determine whether the isotopic enrichment at 10 5 ka bp was caused by local cooling of the surface ocean we estimated sea surface temperatures over this interval using quantitative paleo ecological techniques there is no evidence for cooling in the arabian sea sulu sea or gulf of mexico consistent with the hypothesis that the enrichment at 10 5 ka bp is related to a change in the isotopic composition of the tropical surface ocean and not change in the temperature of calcification we conclude that the cooling at higher latitudes that occurred at 10 5 ka bp did not extend southward to the tropical ocean more cores from high sedimentation rate sites in the tropics are needed to identify the cause and extent of the 18 o signal however these preliminary results are consistent with two meltwater pulses during the deglaciation that distributed isotopically depleted water into each of the tropical oceans with a slow down in meltwater flux at 10 5 ka bp the most likely transport route for the isotopically depleted water from the melting northern hemisphere ice sheets to these isolated tropical ocean basins is via the relatively fast circulation of the atmosphere although other pathways are possible

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 quaternary paleoceanography of the south china sea glacial interglacial contrasts in an enclosed basin the sea surface paleotemperature of the south china sea scs is estimated quantitatively based on the quantitative analysis of planktonic foraminiferal faunas recovered from piston cores v36 06 3 v36 06 5 and so49 kl8 on the northern continental slope the results lead to a reconstruction of the history of paleocirculation patterns during the last 200 000 years the postglacial and interglacial transbasinal circulation pattern was replaced by a semienclosed basin flow pattern during glacial episodes lowered sea level transformed the scs into a semienclosed basin with the only passageway to the open ocean in its northeastern corner the east asian monsoon which governs circulation patterns in the scs both today and during the late quaternary created both clockwise summer and counterclockwise winter surface gyres during glacials the inflow of tropical surface water masses from both the pacific and indian oceans decreased or was completely cut off from this marginal sea causing a greater decrease in glacial sea surface temperature than in the open ocean of the same latitude inferred increased influence of pacific temperate waters and decreased influence of tropical subtropical waters are confirmed by changes in the planktonic foraminiferal assemblages glacial interglacial fluctuation in sea surface temperature sst 6 8 9 3 c for winter and 2 3 c for summer as well as the seasonality 4 6 c for postglacial and interglacials and 9 10 c for glacials are much greater than the adjacent open western pacific reflecting the amplification of the climatic signal in the marginal sea

vostok ice core a continuous isotope temperature record over the last climatic cycle 160 000 years a continuous deuterium profile along the 160 000 year vostok ice core antarctica is interpreted in terms of atmospheric temperature changes this climatic record is the awaited terrestrial complement of the deep sea records supporting the existence of a relation between the pleistocene climate and orbital forcing

the timing of high sea levels over the past 200 000 years the 230 th ages and 234 u 238 u ratios were determined for barbados corals that grew during periods of high sea level within the last 200 000 years the similarity of the initial 234 u 238 u ratios of some of the corals to the modern marine value suggests that these samples are pristine and that the marine 234 u 238 u ratio 83 000 and 200 000 years ago was within 2 per mil of the modern value the accuracies of the 230 th ages are evaluated on the basis of the 234 u 238 u values and a model of the behavior of uranium and thorium isotopes during diagenesis for the last three interglacial and two intervening interstadial periods sea level peaked at or after peaks in summer insolation in the northern hemisphere this overall pattern supports the idea that glacial interglacial cycles are caused by changes in earth9s orbital geometry the sea level drop at the end of the penultimate interglacial the last interglacial and a subsequent interstadial period lagged behind the decrease in insolation by 5 000 to 10 000 years

sediment mixing and accumulation rates in the sulu and south china seas implications for organic carbon preservation in deep sea environments abstract recent rates of carbon burial in two deep sea basins the sulu and south china seas are contrasted to determine factors influencing organic carbon preservation in deep sea sediments the sulu sea is an oxygen deficient warm water basin whereas the adjacent south china sea is more typical of open ocean conditions high resolution sea bed profiles of 14c reveal that accumulation rates for the sulu sea are 2 3 times higher than the south china sea at any given water depth e g 1 3 g cm 2 kyr 1 versus 4 3 g cm 1 kyr 1 respectively at 3000 m higher accumulation rates for the sulu sea are attributed to higher terrigenous input and better carbonate preservation in the warmer bottom waters benthic mixing rates determined using 210pb geochronology generally are lower in the sulu sea 0 004 0 254 cm2 yr 1 as compared with the south china sea 0 17 1 57 cm2 yr 1 especially at the 3000 m and 4000 m sites in the sulu sea where benthic mixing is negligible despite the higher bottom water oxygen levels in the south china sea organic carbon concentration profiles are strikingly similar for the two basins at any given water depth with similar concentration profiles higher accumulation rates in the sulu sea result in equivalently higher carbon preservation rates as primary production is thought to be similar for both basins if anything slightly higher for the south china sea the production rate can not explain the observed differences in carbon preservation in addition benthic mixing rates apparently do not play a major role in carbon preservation as extremely low rates at the deeper sulu sea would predict relatively low carbon preservation contrary to our observations we conclude that sediment accumulation rate is the dominant control on carbon preservation in this area of the western equatorial pacific

millennial scale dynamics of the east asian winter monsoon during the last 200 000 years the primary productivity dynamics of the last 200 000 years in the sulu sea was reconstructed using the abundance of the coccolithophore florisphaera profunda in the images md97 2141 core we find that primary productivity was enhanced during glacial periods which we suggest is due to a stronger east asian winter monsoon during the last 80 kyr eight significant increases in primary productivity pp in the sulu sea are similar to east asian winter monsoon changes recorded in chinese loess the pp maxima are not linked with heinrich events he in the north atlantic although four pp peaks are synchronous with he the pp oscillations have frequencies near those of the dansgaard oeschger cycles in northern hemisphere ice records and indicate a teleconnection of the east asian winter monsoon with greenland climate in this sulu sea record the east asian winter monsoon oscillates with periodicities of6 4 2 3 4 2 3 and 1 5 kyr in particular the 1 5 kyr cycle exhibits a strong and pervasive signal from stage 6 to the holocene without any ice volume modulation this stationarity suggests that the 1 5 kyr cycle is not driven by some high latitude forcing

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

global nature of the younger dryas cooling event inferred from oxygen isotope data from sulu sea cores the younger dryas an approximately 1 000 year long return to near glacial conditions interrupted the glacial holocene climate transition during which most of the northern hemisphere ice sheets melted evidence for the younger dryas event has been found mainly in sediments from the north atlantic ocean and northwest europe and this has led to the idea that the event was caused by an injection of meltwater into the north atlantic ocean1 3 this model however has been recently questioned in the light of coral reef data on the rate of sea level changes during this transition4 here we present high resolution oxygen isotope records from benthic and planktonic foraminifera from two radiocarbon dated cores in the sulu sea showing that the younger dry as occurred synchronously in the surface and deep waters of the sulu sea and the northern atlantic ocean by combining our results with other palaeoclimate data we suggest that the younger dry as event was a global phenomenon and we believe it to have been caused by low atmospheric co2concentrations

eemian climate fluctuations observed in a european pollen record recent ice core data from greenland1 2 suggest that the climate during the last interglacial period the eemian was more unstable than that of the holocene about 10 000 years ago to the present being characterized in particular by a series of cold episodes each lasting about 70 to 750 years subsequent analysis of a second greenland ice core3 4 however failed to corroborate the details of these eemian climate fluctuations a result that may be attributable to the effects of ice flow4 to resolve this discrepancy it is imperative to seek alternative sources of information about the eemian climate here we present climate reconstructions from pollen data from the annually laminated eemian lake sediment record at bispingen5 and from the eemian and holocene peat records at la grande pile6 the former record indicates that an initially warm period of 2 900 yr was followed by cooling and a series of colder episodes one of which had winter temperatures comparable to those at the end of the preceding cold stage the latter records show greater climate instability during the eemian than the holocene these results are in broad agreement with those from the grip ice core but contrast both with the gisp2 core3 4 and with recent high resolution marine records from the north atlantic7 8

maximum sea levels for the last glacial period from u series ages of submerged speleothems pleistocene sea levels reflect changes in the surface distribution of land sea and ice which in turn significantly influence the earth s climate1 the most complete record of sea levels for the last glacial cycle has come from raised coral reef terraces of the huon peninsula papua new guinea2 4 but interpretation of this record is hampered by relatively large age uncertainties and the possibility of variation in the rate of tectonic uplift subaerial speleothems stalagmites stalactites and flowstones from submerged caves in tetonically stable areas provide an alternative source of data5 8 as their growth stops when rising sea levels flood the caves previous studies of speleothems have been limited by dating precision5 6 and sample availability5 7 here we present high precision thermal ionization mass spectrometric 230th ages9 11 for a comprehensive suite of speleothem samples from the bahamas our results provide a record of maximum elevation of sea levels for the period from 80 to 10 kyr before the present for much of which sea levels are poorly known we also find that regional palaeoclimatic change can be an important factor in the termination of speleothem growth

ground penetrating radar as a tool for probing the shallow subsurface of mars 1 design and testing of an impulse ground penetrating radar gpr for possible rover deployment on mars in 2009 is well underway the gpr has mass power volume and data rate targets of 0 5 kg 3 w peak 3400 cm3 and 0 3 mb d and will possess easily modified bistatic high frequency e g 500 600 mhz and monostatic rat tail e g 100 mhz antennas the gpr should be capable of measuring in situ radar properties on mars to depths of up to 10 20 m thereby helping to constrain near surface geology and structure initial gpr tests at the site of the 2001 fido rover field trials near cronese lake california confirm the value of the instrument in defining local geologic setting and in providing context for data collected using other rover science payload elements a rover deployed gpr may enable three dimensional mapping of local stratigraphy which in turn can assist in evaluating the history of aqueous activity and the accessibility of near surface water