multiproxy comparison of oceanographic temperature during heinrich events in the eastern subtropical atlantic abstract abrupt climate change episodes associated with catastrophic calvings of the laurentide and european ice sheets during the last glacial heinrich events he had far reaching effects in the atlantic we have measured minor and trace element concentrations in planktonic foraminiferal calcite in a core from the iberian margin md95 2040 and a core from the gulf of cadiz md99 2339 during he 1 4 and 5 to explore the use of the mg temperature proxy for constraining regional temperature changes during these unique periods of ice rafting high sedimentation rates throughout the length of both cores allow a detailed reconstruction of temperature during abrupt events mg ca derived temperatures reveal 5 13 c amplitude of cooling during he1 the largest and most well defined event in this region the northern site most likely experienced the higher end of this amplitude range cooling implied by the mg ca data is within the range of assemblage derived sea surface temperature sst changes from the same cores showing 10 c perturbations for each he but the mg ca data imply smaller changes during he4 and he5 cooling estimated from unsaturated alkenone ratios 3 c represent the smallest changes the prominence of he1 in this region is consistent with the changes over the wider north atlantic that show colder temperatures during he1 vs he4 we use cd ca to reconstruct nutrient concentrations and find very low values 0 02 0 04 mol mol at both locations during he these low values are consistent with core top planktonic cd ca from each region suggesting that the cooling during he was unlikely to be caused by more intense upwelling than in the modern temperature comparisons of other proxies alkenone u 37 k and assemblage data from the same core suggest that mg ca paleothermometry is sensitive to the relative size of each he this sensitivity is capable of highlighting other variables that influence the impact of heinrich events on sst including the background climate state

origin of the northern atlantic s heinrich events as first noted by heinrich 1988 glacial age sediments in the eastern part of the northern atlantic contain layers with unusually high ratios of ice rafted lithic fragments to foraminifera shells he estimated that these layers are spaced at intervals of roughly 10 000 years in this paper we present detailed information documenting the existence of the upper five of these layers in odp core 609 from 50 n and 24 w their ages are respectively 15 000 radiocarbon years 20 000 radiocarbon years 27 000 radiocarbon years about 40 000 years and about 50 000 years we also note that the high lithic fragment to foram ratio is the result of a near absence of shells in these layers although we are not of one mind regarding the origin of these layers we lean toward an explanation that the heinrich layers are debris released during the melting of massive influxes of icebergs into the northern atlantic these sudden inputs may be the result of surges along the eastern margin of the laurentide ice sheet

warming of surface waters in the mid latitude north atlantic during heinrich events 1 during the six heinrich events of the last 70 kyr episodic calving from the circum atlantic ice sheets released large numbers of icebergs into the north atlantic these icebergs and associated meltwater flux are hypothesized to have led to a shutdown of atlantic meridional overturning circulation and severe cooling in large parts of the northern hemisphere however due to the limited availability of high resolution records the magnitude of sea surface temperature sst changes related to the impact of heinrich events on the midlatitude north atlantic is poorly constrained here we present a record of u37k based ssts derived from sediments of integrated ocean drilling project site u1313 located at the southern end of the ice rafted debris ird belt in the midlatitude north atlantic 41 n we demonstrate that all six heinrich events are associated with a rapid warming of surface waters by 2 4 c in a few thousand years the presence of ird leaves no doubt about the simultaneous timing and correlation between rapid surface water warming and heinrich events we argue that this warming in the midlatitude north atlantic is related to a northward expansion of the subtropical gyre during heinrich events as a wide range of studies demonstrated that in the central ird belt heinrich events are associated with low ssts these results thus identify an antiphased seesaw pattern in ssts during heinrich events between the midlatitude warm and northern north atlantic cold this highlights the complex response of surface water characteristics in the north atlantic to heinrich events that is poorly reproduced by freshwater hosing experiments and challenges the widely accepted view that within the ird belt of the north atlantic heinrich events coincide with periods of low ssts

rapid subtropical north atlantic salinity oscillations across dansgaard oeschger cycles geochemical and sedimentological evidence suggest that the rapid climate warming oscillations of the last ice age the dansgaard oeschger cycles were coupled to fluctuations in north atlantic meridional overturning circulation through its regulation of poleward heat flux the balance between cold meltwater from the north and warm salty subtropical gyre waters from the south influenced the strength and location of north atlantic overturning circulation during this period of highly variable climate here we investigate how rapid reorganizations of the ocean atmosphere system across these cycles are linked to salinity changes in the subtropical north atlantic gyre we combine mg ca palaeothermometry and oxygen isotope ratio measurements on planktonic foraminifera across four dansgaard oeschger cycles spanning 45 9 59 2 kyr ago to generate a seawater salinity proxy record from a subtropical gyre deep sea sediment core we show that north atlantic gyre surface salinities oscillated rapidly between saltier stadial conditions and fresher interstadials covarying with inferred shifts in the tropical atlantic hydrologic cycle and north atlantic overturning circulation these salinity oscillations suggest a reduction in precipitation into the north atlantic and or reduced export of deep salty thermohaline waters during stadials we hypothesize that increased stadial salinities preconditioned the north atlantic ocean for a rapid return to deep overturning circulation and high latitude warming by contributing to increased north atlantic surface water density on interstadial transitions

gisp2 oxygen isotope ratios the gisp2 oxygen isotope record with its high resolution detail yields crucial information on past climate change the glacial 18o oscillations of the gisp2 core with their very fast onsets are templates of a prototype oscillation of variable duration with an amplitude of 3 9 the halfway mark of the cold warm transition is reached in 2 years the top is reached in 50 years the 18o time gradient of the leading front is about 7 8 per 100 yr after reaching the top 18o slowly declines by 0 14 per 100 yr the duration of 18o decline varies from a couple of centuries for fast oscillations to about 4000 yr for slower ones the subsequent 18o downturn during the warm cold transition has a 18o time gradient of 3 2 per 100 yr and lasts about 80 yr

climate response of the florida peninsula to heinrich events in the north atlantic abstract hydrogen and carbon isotope values d 13c were measured on lipid biomarkers from a sediment core collected in lake tulane florida usa to infer shifts in climate and hydrologic variables during the last glacial isotopic trends from 24 samples correlate with plant community shifts evaluated in a previous pollen study by grimm et al 2006 we observe maxima in leaf values and minima in d values concurrent with peaks in pinus pollen abundances and heinrich events 4 2 increased leaf values during north atlantic cold spells indicate lower water use efficiency among angiosperms around lake tulane combined d values from terrestrial and aquatic lipids confirm that aridity decreased during cold stadial periods heinrich events and increased during warm interstadials furthermore lower d values in aquatic lipids during stadials are attributed to warming as well as changing moisture sources the anti phase relationship between temperatures and aridity derived from our subtropical lacustrine record and those at high latitude in the north atlantic is likely the result of complex ocean atmosphere teleconnections that resulted from the collapse of atlantic meridional overturning circulation during heinrich events in the north atlantic

high frequency palaeoceanographic changes during the past 140 000 yr recorded by the organic matter in sediments of the iberian margin abstract biogenic records of the marine palaeoproductivity carbonates organic carbon and c 37 alkenones and the molecular stratigraphy of past sea surface temperatures ssts u 37 k were studied at high resolution in two cores of the iberian margin the comparison of these records indicates that the oceanographic conditions switched abruptly during the past 160 kyr between three kinds of regimes a first regime with high 17 22 c sst and low productivity typifies the interglacial periods marine isotopic stages mis 5 and 1 several periods during mis 6 2 and the terminations ii and i are characterised by about 4 5 c colder sst and a higher organic matter accumulation both of which define the second regime this anticorrelation between sst and marine productivity suggests that these variations are related to the intensity of the coastal upwelling by contrast with this upwelling behaviour extremely low biological productivity and very cold sst 6 12 c occurred during short phases of glacial mis 6 4 and 2 and as abrupt events 1 kyr or less during mis 3 the three oceanographic regimes are consistent with micropalaeontological changes in the same cores based on foraminifera and diatoms the general trend of these hydrologic changes follows the long term glacial interglacial cycle but the millennium scale variability is clearly related to heinrich events and dansgaard oeschger cycles strengthening of the upwelling corresponds probably to an intensification of the subtropical atmospheric circulation over the north atlantic which was influenced by the presence of continental ice sheets however extreme glacial conditions due to massive discharges of icebergs interrupted the upwelling interestingly both terminations ii and i coincided with strong but transient intensification of the upwelling

position of the polar front along the western iberian margin during key cold episodes of the last 45 ka 1 this paper documents the migration of the polar front pf over the iberian margin during some of the cold climatic extremes of the last 45 ka it is based on a compilation of robust and coherent paleohydrological proxies obtained from eleven cores distributed between 36 and 42 n planktonic 18o globigerina bulloides ice rafted detritus concentrations and the relative abundance of the polar foraminifera neogloboquadrina pachyderma sinistral were used to track the pf position these three data sets compared from core to core show a consistent evolution of the sea surface paleohydrology along the iberian margin over the last 45 ka we focused on five time slices representative of cold periods under distinct paleoenvironmental forcings the 8 2 ka event and the younger dryas two recent cold events occurring within high values of summer insolation heinrich events 1 and 4 reflecting major episodes of massive iceberg discharges into the north atlantic and the last glacial maximum typifying the highest ice volume accumulated in the northern hemisphere for each event we generated schematic maps mirroring past sea surface hydrological conditions the maps revealed that the polar front presence along the iberian margin was restricted to heinrich events the sea surface conditions during the last glacial maximum were close to those at present day except for the northern sites which briefly experienced subarctic conditions

changes in planktic foraminiferal faunas temperature and salinity in the gulf stream during the last 30 000 years influence of meltwater via the mississippi river abstract variations in the distribution of planktic foraminiferal faunas temperature and salinity in the surface water of the gulf stream during the last 30 000 years have been reconstructed based on a sediment core from the blake ridge subtropical western atlantic ocean temperatures and salinities were calculated using planktic foraminiferal transfer functions and previously published oxygen isotope values productivity was estimated using the 106 m size fraction of planktic foraminifera the reconstructed values show that temperature variations have been small during the investigated period with a total range of only 3 c the highest temperatures about 1 5 c above the present temperature in the area occurred during the late glacial heinrich event 1 and the mid holocene time periods the lowest temperatures about 1 5 c below the present temperatures occurred during the bolling interstadial the early holocene period was relatively cool the low temperatures during the bolling interstadial and during the early holocene are in contrast to the northeastern atlantic where the bolling interstadial was the warmest period of the deglaciation and the early holocene the warmest during the holocene we attribute the lower temperatures during the bolling and early holocene periods to colder meltwater from the laurentide ice sheet flowing into the gulf of mexico through the mississippi river system and carried to the blake ridge via the gulf stream

paleohydrological changes during the last deglaciation in northern brazil abstract we here report a reconstruction of hydrological balance variations in northern brazil for the last 20 ka deduced from the d values of aquatic and land plant molecules extracted from the sediment infill of lake caco our reconstructed precipitation lake water isotope ratio and evaporation evapotranspiration isotope effect allows us to obtain an estimate of moisture balance and to a lesser extent precipitation amount and seasonality changes during the end of the last glacial maximum lgm between ca 20 and 17 3 ka high d values and smaller fractionation of leaf waxes indicate an arid to semi arid climate with a long lasting dry season an abrupt change towards much wetter conditions occurred within ca 500 years from 17 3 to 16 8 ka as shown by a 50 decrease in d h ratios and a marked increase in h isotopic fractionation of leaf waxes this abrupt isotopic change coincides with a major transformation from savanna dominated vegetation to humid rain forest around the lake based on pollen data comparisons with other paleo precipitation records from south american sites indicate that lateglacial humid conditions were controlled by intensification of the itcz and or a southward shift of its mean position across our study site our isotope data show only a small rise in aridity during younger dryas event 13 11 5 ka although the holocene was not screened in details d h ratios of terrestrial and aquatic compounds show near constant offsets suggesting stable and relatively humid climate conditions during this period

quantitative integration of 3d and 4d seismic impedance into reservoir simulation model updating in the norne field the ultimate goal of reservoir simulation in reservoir surveillance technology is to estimate long term production forecasting and to plan development and management of petroleum fields however maintaining reliable reservoir models which honour available static and dynamic data involve inherent risks due to the uncertainties in space and time of the distribution of hydrocarbons inside reservoirs recent applications have shown that these uncertainties can be reduced by quantitative integration of seismic data into the reservoir modelling workflows to identify which areas and reservoir attributes of the model should be updated this work aims using seismic data to reduce ambiguity in calibrating reservoir flow simulation model with an uncertain petro elastic model proposing a circular workflow of inverted seismic impedance 3d and 4d and engineering studies with emphasis on the interface between static and dynamic models the main contribution is to develop an updating procedure for adjusting reservoir simulation response before using it in the production forecasting and enhance the interpretive capability of reservoir properties accordingly the workflow evaluates consistency of reservoir simulation model and inverted seismic impedance assisted by production history data to close the loop between reservoir engineering and seismic domains the methodology is evaluated in a complex faulted sandstone reservoir the norne benchmark field where a significant reservoir behaviour understanding about the static and dynamic reservoir properties is obtained towards the quantitative integration of seismic impedance data this leads to diagnosis of the reservoir flow simulation reliability and generation of an updated simulation model consistent with observed seismic and well production history data as well as a calibrated petro elastic model furthermore as norne field is a benchmark case this study can be considered to enrich the discussions over deterministic or probabilistic history matching studies

rocks under strain strain induced time lapse time shifts are observed for depleting reservoirs pressure depletion as a result of oil and gas production creates changes in the stress and strain fields of the rock material both inside and outside the reservoir seismic waves propagating through these rocks have different traveltimes before and after depletion because the layer thicknesses change and the seismic velocity is altered by the changes in the stress and strain fields the cumulative change in two way traveltimes with depth is referred to as time lapse time shift

meltwater pulse 1a from antarctica as a trigger of the bolling allerod warm interval meltwater pulse 1a mwp 1a was a prominent feature of the last deglaciation which led to a sea level rise of 20 meters in less than 500 years concurrent with mwp 1a was the onset of the bolling allerod interstadial event 14 600 years before the present which marked the termination of the last glacial period previous studies have been unable to reconcile a warm northern hemisphere with mwp 1a originating from the laurentide or fennoscandian ice sheets with the use of a climate model of intermediate complexity we demonstrate that with mwp 1a originating from the antarctic ice sheet consistent with recent sea level fingerprinting inferences the strength of north atlantic deep water nadw formation increases thereby warming the north atlantic region and providing an explanation for the onset of the bolling allerod warm interval the established mode of active nadw formation is then able to respond to subsequent freshwater forcing from the laurentide and fennoscandian ice sheets setting the stage for the younger dryas cold period the melting of continental ice sheets during the last deglaciation provided a freshwater source to the ocean that affected global sea level and the strength of the thermohaline circulation an exceptionally large melting event inferred from far field relative sea level records occurred

principles of avo crossplotting hydrocarbon related avo anomalies may show increasing or decreasing amplitude variation with offset conversely brine saturated background rocks may show increasing or decreasing avo

a model for tsunami flow inversion from deposits tsuflind abstract modern tsunami deposits are employed to estimate the overland flow characteristics of tsunamis with the help of the overland flow characteristics the characteristics of the causative tsunami wave can be estimated the understanding of tsunami deposits has tremendously improved over the last decades there are three prominent inversion models a moore s advection model moore et al 2007 b soulsby s model soulsby et al 2007 and c tsusedmod jaffe gelfenbuam 2007 tsuflind incorporates all three models and adds new modules to better simulate tsunami deposit formation and calculate flow condition tsuflind takes grain size distribution thickness water depth and topography information as inputs tsuflind computes sediment concentration grain size distribution of sediment source and initial flow condition to match the sediment thickness and grain size distribution from field observation furthermore tsuflind estimates the flow speed froude number and representative wave amplitude the model is tested by using field data collected at ranganathapuram india after the 2004 india ocean tsunami tsuflind reproduces the field measurement grain size distribution with less than 5 error tsunami speed in this test case is about 4 7 ms 1 at 150 m inland and decreases to 3 3 ms 1 350 m inland from the shoreline the estimated wave amplitude of the largest wave for this test case is about 5 to 7 m

simulated resumption of the north atlantic meridional overturning circulation slow basin wide advection and abrupt local convection abstract the resumption process of the north atlantic meridional overturning circulation moc is investigated in a series of freshwater hosing experiments using a comprehensive coupled climate model four different freshwater perturbations are applied to the north atlantic between 50 n and 70 n leading to a substantial weakening of moc and an expansion of winter sea ice cover over the greenland iceland norwegian gin seas deactivating the freshwater forcing leads to a two phase recovery of the moc the first phase is a slow basin wide advection process whereas the second phase is an abrupt decadal scale transition located in the north atlantic the slow basin wide advection process to an intermediate state of the moc is characterized by a restart of the deep water production in the area of the subpolar gyre and the irminger basin however the ice cover over the gin seas remains whereas the surface density gradually increases in the gin seas on a century time scale the length of this intermediate state depends on the strength of freshwater perturbation which determines the magnitude of the meridional density gradient in the north atlantic the second transition phase is triggered by a model specific density threshold reached in the gin seas when passed the moc abruptly intensifies by 60 within 60 80 years the analysis shows that this abrupt intensification only depends on surface salinity in the gin seas the model results reveal that the simulated sea ice retreat in the gin seas and a rapid increase of the greenland air temperature of the second phase of the resumption of the moc are similar in amplitude to temperature proxies observed during dansgaard oeschger events of the last ice age

δd values of n alkanes in tibetan lake sediments and aquatic macrophytes a surface sediment study and application to a 16 ka record from lake koucha abstract a set of lake surface sediment samples and aquatic macrophytes from the eastern and central tibetan plateau and a sediment core from koucha lake northeastern tibetan plateau were analysed for hydrogen isotope signals of aliphatic lipid biomarkers the d values of n alkanes were correlated with those of meteoric water in the summer months and showed increasing pearson correlation coefficients with increasing n alkane chain length r 0 80 for n c 31 while in samples from the most humid regions southeastern tibetan plateau the apparent enrichment factors between meteoric water and lipids are close to those reported for other humid sites e 135 for mid chain and 125 for long chain n alkanes they become smaller e 118 to 41 mean value 86 at sites with a negative moisture balance northeastern and central tibetan plateau and qaidam basin this might be caused by enrichment in deuterium of the source water used for lipid synthesis as a result of lake water evaporation and soil and leaf water evapotranspiration in the core from lake koucha decreasing d values of all n alkanes between 15 and 10 cal ka bp give evidence for an intensification of the asian summer monsoon at ca 9 cal ka bp a ca 15 shift towards higher d values of mid chain n alkanes suggests enhanced evaporation of the lake water which outweighs higher precipitation amounts because of a temperature increase during the early holocene monsoonal maximum only a few surface sediment samples show a significant offset between d values of mid chain n alkanes and n c 31 d mid n c31 and no systematic dependence between this offset and environmental parameters such as mean annual precipitation was found in the core available data for most samples also do not show a significant offset only a slight increase 15 of d mid n c31 at ca 10 0 cal ka bp and a decrease 17 at ca 6 8 cal ka bp might indicate wetter and drier conditions respectively however interpretation of d mid n c31 throughout the record is difficult because of a lack of reliable data for n c 31 in key sections of the core so more records are necessary to further test the potential applicability of d mid n c31 as a proxy for palaeo hydrological conditions

oxygen and hydrogen isotopic ratios of water in precipitation beyond paleothermometry paleoclimatologists face a dilemma no sedimentary proxy is a pure recorder of quantitative climate information yet climate modelers and policy makers increasingly seek quantitative comparisons between instrumentally documented possibly anthropogenic climate changes and those produced naturally in the past in the second edition of his influential book bradley 1999 p 6 discussed the calibration of proxy records to learn past climate changes calibration involves using modern climatic records and proxy materials to understand how and to what extent proxy materials are climate dependent it is assumed that the modern relationships observed have operated unchanged throughout the period of interest the principle of uniformitarianism in other words one relates the characteristics of sediment to climate at different places for one time or at a place for short times and then uses that relation plus characteristics of older sediments to estimate the climatic conditions that produced those sedimentary characteristics bradley 1999 then extensively discussed the difficulties in applying this methodology in a complex world with imperfect recorders nonetheless the goal of using calibrated proxies for quantitative as well as qualitative paleoclimatic reconstruction is clear a prominent recent use of calibrated paleoclimatic data is the assessment of whether the probably anthropogenic warming of the latter 20th century moved beyond the band of natural variability of the prevailing climate bradley 2000 combined recent instrumental records with several longer proxy based reconstructions of surface temperature including that of mann et al 1999 based on this composite data set bradley 2000 argued that temperatures in the late 20th century were unique in the context of the entire millennium the proxy records were primarily based on tree ring data but included isotopic and major element geochemistry of corals and occurrence of melt layers and isotopic ratios of water in ice cores however broecker 2001 questioned the basis for the reconstruction of

phasing of deglacial warming and laurentide ice sheet meltwater in the gulf of mexico evidence is emerging that the tropical climate system played a major role in global climate change during the last deglaciation however existing studies show that deglacial warming was asyn chronous across the tropical band complicating the identification of causal mechanisms the orca basin in the northern gulf of mexico is ideally located to record subtropical atlantic sea surface temperature sst warming in relation to meltwater input from the laurentide ice sheet paired d 18 o and mg ca data on the planktonic foraminifer globigerinoides ruber from core en32 pc6 are used to separate deglacial changes in sst and d 18 o of sea water sst as calculated from mg ca data increased by 3 8c from ca 17 2 to 15 5 ka in association with heinrich event 1 and was not in phase with greenland air temperature subtracting tem perature effects from d 18 o values in g ruber reveals two excur sions representing laurentide meltwater input to the gulf of mex ico one of 1 5 from ca 16 1 to 15 6 ka and a second major spike of 2 5 from ca 15 2 to 13 0 ka that encompassed melt water pulse 1a and peaked ca 13 8 ka during the bolling allerod conversion to salinity through the use of a laurentide meltwater end member of 225 indicates that near surface salinity de creased by 2 4 during these spikes these results suggest that gulf of mexico sst warming preceded peak laurentide ice sheet decay and the bolling allerod interval by 2 k y and that heat was retained in the subtropical atlantic during heinrich event 1 consistent with modulation of deglacial climate by thermohaline circulation

tropical north atlantic subsurface warming events as a fingerprint for amoc variability during marine isotope stage 3 the role of atlantic meridional overturning circulation amoc as the driver of dansgaard oeschger do variability that characterized marine isotope stage 3 mis 3 has long been hypothesized although there is ample proxy evidence suggesting that do events were robust features of glacial climate there is little data supporting a link with amoc recently modeling studies and subsurface temperature reconstructions have suggested that subsurface warming across the tropical north atlantic can be used to fingerprint a weakened amoc during the deglacial because a reduction in the strength of the western boundary current allows warm salinity maximum water of the subtropical gyre to enter the deep tropics to determine if amoc variability played a role during the do cycles of mis 3 we present new high resolution mg ca and 18o records spanning 24 52 kyr from the near surface dwelling planktonic foraminifera globigerinoides ruber and the lower thermocline dwelling planktonic foraminifera globorotalia truncatulinoides in southern caribbean core vm12 107 11 33 n 66 63 w 1079 m depth our subsurface mg ca record reveals abrupt increases in mg ca ratios the largest equal to a 4 c warming during the interstadial stadial transition of most do events during this period this change is consistent with reconstructions of subsurface warming events associated with cold events across the deglacial using the same core additionally our data support the conclusion reached by a recently published study from the florida straits that amoc did not undergo significant reductions during heinrich events 2 and 3 this record presents some of the first high resolution marine sediment derived evidence for variable amoc during mis 3

delayed hydrological response to greenland cooling at the onset of the younger dryas in western europe during the younger dryas cold event about 12 800 years ago environmental change in western europe seems to occur 170 years after cooling over greenland lake sediment analyses confirm this delay and suggest european hydrological and vegetation change occurred only after the build up of sea ice in the north atlantic pushed the westerly wind system south

deglacial sea surface temperature and salinity increase in the western tropical atlantic in synchrony with high latitude climate instabilities a sediment core from the western tropical atlantic covering the last 21 000 yr has been analysed for centennial scale reconstruction of sea surface temperature sst and ice volume corrected oxygen isotopic composition of sea water delta 18 o ivc sw using mg ca and delta 18 o of the shallow dwelling planktonic foraminifer globigerinoides ruber white at a period between 15 5 and 17 5 kyrbp the mg ca sstand delta 18 o ivc sw a proxy for sea surface salinity sss reveals a warming of around 2 5 degrees c along with all increase in salinity a second period of pronounced warming and sss increase occurred between 11 6 and 13 5 kyr bp within age model uncertainties both warming intervals were synchronous with air temperature increase over antarctica and ice retreat in the southern south atlantic and terminated with abrupt centennial scale sss decrease and slight sst cooling in conjunction with interglacial reactivation of the meridional overturning circulation moc we suggest that during these warm intervals production of saline and warm water of the north brazil current resulted in pronounced heat and salt accumulation and was associated with warming in the southern atlantic southward displacement of the intertropical convergence zone and weakened moc at the termination of the younger dryas and heinrich event 1 intensification of cross equatorial heat and salt transport caused centennial scale cooling and freshening of the western tropical atlantic surface water this study shows that the western tropical atlantic served as a heat and salt reservoir during deglaciation the sudden release of accumulated heat and salt at the end of younger drays and heinrich event 1 may have contributed to the rapid reinvigoration of the atlantic moc c 2005 elsevier b v all rights reserved

millennial to century scale variability in gulf of mexico holocene climate records of the intertropical convergence zone itcz related to orbital forcing the d 18 o of the surface dwelling planktic foraminifer globigerinoides ruber show negative excursions between 14 and 10 2 ka radiocarbon years that reflect influx of meltwater into the western gom during melting of the laurentide ice sheet the relative abundance of the planktic foraminifer globigerinoides sacculifer is related to transport of caribbean water into the gom maximum transport of caribbean surface waters and moisture into the gom associated with a northward migration of the average position of the itcz occurs between about 6 5 and 4 5 ka in addition abundance variations of g sacculifer show century scale variability throughout most of the holocene the gom record is consistent with records from other areas suggesting that century scale variability is a pervasive feature of holocene climate the frequency of several cycles in the climate records is similar to cycles identified in proxy records of solar variability indicating that at least some of the century scale climate variability during the holocene is due to external solar forcing index terms 4267 oceanography general paleoceanography 9604 information related to geologic time cenozoic 3030 marine geology and geophysics micropaleontology

speleothem u series dating of semi synchronous climate oscillations during the last deglaciation evidence for nearly synchronous climate oscillations during the last deglaciation has been found throughout the northern hemisphere but few records are based on independent time scales of calendar years we present a rare uranium series dated oxygen carbon isotope record for a speleothem from tangshan cave china which demonstrates that abrupt deglacial climatic oscillations from 16 800 to 10 500 yr bp are semi synchronous with those found in greenland ice core records relatively rapid shifts in speleothem oxygen isotope ratios demonstrate that the intensity of the east asian monsoon switched in parallel with the abrupt transitions separating the bolling allerod younger dryas and pre boreal climatic reversals however the dated isotopic transitions appear to have lasted longer our results demonstrate the dominant role of atmospheric teleconnections in the rapid propagation of deglacial climatic signals on a hemispheric scale and highlight the importance of u series dated speleothems in the timing and characterization of abrupt climate change c 2003 elsevier b v all rights reserved

resaturated pay a new infill target type identified through the application and continuous improvement of 4d seismic at the forties field forties is a giant north sea oil field with an estimated 4 2 billion to 5 billion barrels of oil initially in place the field has been producing since 1975 and by year end 2015 had produced more than 2 7 billion barrels of cumulative oil production the peak production rate exceeded more than 500 000 barrels of oil per day bopd in 1979 and since then more than 3 8 billion barrels of water have been injected into the field the majority of the field is now water swept due to the combined effect of water injection and extensive depletion supported by a large underlying aquifer the ability to identify the few remaining unswept portions of the reservoir has elevated 4d seismic into a key technology to derisk all new wells drilled at forties the types of 4d targets at forties are ever evolving as continuous improvements in seismic acquisition and processing technologies deliver higher quality time lapse seismic data with every subtle improvement in 4d repeatability additional and sometimes unexpected i

evidence for warm wet heinrich events in florida analyses of pollen and plant macrofossils from a new core spanning the past 60 000 years from lake tulane florida show a strong antiphase relationship in temperature between florida and the north atlantic region during the pleistocene oak scrub and prairie phases were coeval with long intense dansgaard oeschger interstadials warm periods that initiated bond cycles pine phases were coeval with the north atlantic long stadials cold periods that ended bond cycles and were terminated by heinrich events lake levels were higher during pine phases and climate was wetter however climate in florida was also warmer during these phases which were cold periods in the north atlantic perhaps diminution of thermohaline circulation before and during heinrich events reduced northward heat transport and retained warmth in the subtropical atlantic and gulf of mexico

heinrich events massive late pleistocene detritus layers of the north atlantic and their global climate imprint 1 millennial climate oscillations of the glacial interval are interrupted by extreme events the so called heinrich events of the north atlantic their near global footprint is a testament to coherent interactions among earth s atmosphere oceans and cryosphere on millennial timescales heinrich detritus appears to have been derived from the region around hudson strait it was deposited over approximately 500 250 years several mechanisms have been proposed for the origin of the layers binge purge cycle of the laurentide ice sheet jokulhlaup activity from a hudson bay lake and an ice shelf buildup collapse fed by hudson strait to determine the origin of the heinrich events i recommend 1 further studies of the timing and duration of the events 2 further sedimentology study near the hudson strait and 3 greater spatial and temporal resolution studies of the layers as well as their precursory intervals studies of previous glacial intervals may also provide important constraints

distinct climate change synchronous with heinrich event one recorded by stable oxygen and carbon isotopic compositions in stalagmites from china abstract uranium series dating of oxygen and carbon isotope records for stalagmite sj3 collected in songjia cave central china shows significant variation in past climate and environment during the period 20 10 ka stalagmite sj3 is located more than 1000 km inland of the coastal hulu cave in east china and more than 700 km north of the dongge cave in southwest china and despite minor differences displays a clear first order similarity with the hulu and dongge records the coldest climatic phase since the last glacial maximum which is associated with the heinrich event 1 in the north atlantic region was clearly recorded in sj3 between 17 6 and 14 5 ka in good agreement in timing duration and extent with the records from hulu and dongge caves and the greenland ice core the results indicate that there have been synchronous and significant climatic changes across monsoonal china and strong teleconnections between the north atlantic and east asia regions during the period 20 10 ka this is much different from the holocene optimum which shows a time shift of more than several thousands years from southeast coastal to inland china it is likely that temperature change at northern high latitudes during glacial periods exerts stronger influence on the asian summer monsoon relative to insolation and appears to be capable of perturbing large scale atmospheric oceanic circulation patterns in the northern hemisphere and thus monsoonal rainfall and paleovegetation in east asia climatic signals in the north atlantic region propagate rapidly to east asia during glacial periods by influencing the winter land sea temperature contrast in the east asian monsoon region

a 50 000 year record of climate oscillations from florida and its temporal correlation with the heinrich events oscillations of pinus pine pollen in a 50 000 year sequence from lake tulane florida indicate that there were major vegetation shifts during the last glacial cycle episodes of abundant pinus populations indicate a climate that was more wet than intervening phases dominated by quercus oak and ambrosia type ragweed and marsh elder the pinus episodes seem to be temporally correlated with the north atlantic heinrich events which were massive periodic advances of ice streams from the eastern margin of the laurentide ice sheet possible links between the tulane pinus and heinrich events include hemispheric cooling the influences of mississippi meltwater on sea surface temperatures in the gulf of mexico and the effects of north atlantic thermohaline circulation on currents in the gulf

persistent summer expansion of the atlantic warm pool during glacial abrupt cold events palaeoclimate records and numerical model simulations indicate that changes in tropical and subtropical sea surface temperatures and in the annual average position of the intertropical convergence zone are linked to high latitude climate changes on millennial to glacial interglacial timescales it has recently been suggested that cooling in the high latitudes associated with abrupt climate change events is evident primarily during the northern hemisphere winter implying increased seasonality at these times8 however it is unclear whether such a seasonal bias also exists for the low latitudes here we analyse the mg ca ratios of surface dwelling foraminifera to reconstruct sea surface temperatures in the northeastern gulf of mexico for the past 300 000 years we suggest that sea surface temperatures are controlled by the migration of the northern boundary of the atlantic warm pool and hence the position of the intertropical convergence zone during boreal summer and are relatively insensitive to winter conditions our results suggest that summer atlantic warm pool expansion is primarily affected by glacial interglacial variability and low latitude summer insolation because a clear signature of rapid climate change events such as the younger dryas cold event is lacking in our record we conclude that high latitude events seem to influence only the winter caribbean climate conditions consistent with the hypothesis of extreme northern hemisphere seasonality during abrupt cooling events