direct determination of the timing of sea level change during termination ii an outcrop within the last interglacial terrace on barbados contains corals that grew during the penultimate deglaciation or termination ii we used combined 230th and231pa dating to determine that they grew 135 8 0 8 thousand years ago indicating that sea level was 18 3 meters below present sea level at the time this suggests that sea level had risen to within 20 of its peak last interglacial value by 136 thousand years ago in conflict with milankovitch theory predictions orbital forcing may have played a role in the deglaciation as may have isostatic adjustments due to large ice sheets other corals in the same outcrop grew during oxygen isotope 18o substage 6e indicating that sea level was 38 5 meters below present sea level about 168 0 thousand years ago when compared to the 18o signal in the benthic v19 30 v19 28 record at that time the coral data extend to the previous glacial cycle the conclusion that deep water temperatures were colder during glacial periods

direct comparison of marine and terrestrial climate variability during marine isotope stages 6 and 5 results from santa barbara basin odp hole 893a 1 planktonic foraminiferal 1 8 o pollen and opal records from santa barbara basin are used to evaluate climate changes in the northeast pacific during marine isotope stages mis 6 and 5 while the oak and foraminifera record the major glacial interglacial changes opal is not correlated with these large scale transitions surface water warming in the basin was synchronous with terrestrial warming but earlier than ice sheet melting and increasing northern hemisphere insolation at termination ii during and immediately after deglaciation our marine proxies indicate the presence of an isothermal upper water column later in substage 5e the water column became thermally stratified surface productivity increased and laminated sediments began accumulating sediment trap and hydrographic data suggest these changes were due to the onset of a strong seasonal cycle similar to that seen today in the basin a series of rapid coolings within mis 5 appears to be synchronous with north atlantic ice rafting events and greenland stadials

evidence from u th dating against northern hemisphere forcing of the penultimate deglaciation milankovitch proposed that summer insolation at mid latitudes in the northern hemisphere directly causes the ice age climate cycles1 this would imply that times of ice sheet collapse should correspond to peaks in northern hemisphere june insolation but the penultimate deglaciation has proved controversial because june insolation peaks 127 kyr ago whereas several records of past climate suggest that change may have occurred up to 15 kyr earlier2 3 4 5 6 7 8 there is a clear signature of the penultimate deglaciation in marine oxygen isotope records but dating this event which is significantly before the 14c age range has not been possible here we date the penultimate deglaciation in a record from the bahamas using a new u th isochron technique after the necessary corrections for recoil mobility of 234u and 230th and a small age correction for sediment mixing the midpoint age for the penultimate deglaciation is determined to be 135 2 5 kyr ago this age is consistent with some coral based sea level estimates but it is difficult to reconcile with june northern hemisphere insolation as the trigger for the ice age cycles potential alternative driving mechanisms for the ice age cycles that are consistent with such an early date for the penultimate deglaciation are either the variability of the tropical ocean atmosphere system or changes in atmospheric co2 concentration controlled by a process in the southern hemisphere

oceanographic dynamics and the end of the last interglacial in the subpolar north atlantic the last interglacial interval was terminated by the inception of a long progressive glaciation that is attributed to astronomically influenced changes in the seasonal distribution of sunlight over the earth however the feedbacks internal dynamics and global teleconnections associated with declining northern summer insolation remain incompletely understood here we show that a crucial early step in glacial inception involves the weakening of the subpolar gyre spg circulation of the north atlantic ocean detailed new records of microfossil foraminifera abundance and stable isotope ratios in deep sea sediments from ocean drilling program site 984 south of iceland reveal repeated progressive cold water mass expansions into subpolar latitudes during the last peak interglacial interval marine isotope substage 5e these movements are expressed as a sequence of progressively extensive southward advances and subsequent retreats of a hydrographic boundary that may have been analogous to the modern arctic front and associated with rapid changes in the strength of the spg this persistent millennial scale oceanographic oscillation accompanied a long term cooling trend at a time of slowly declining northern summer insolation providing an early link in the propagation of those insolation changes globally and resulting in a rapid transition from extensive regional warmth to the dramatic instability of the subsequent 100 ka

decadal scale changes in shallow infaunal foraminiferal assemblages at the porcupine abyssal plain ne atlantic abstract trends in the abundance diversity and taxonomic composition of live rose bengal stained foraminiferal assemblages 0 1 cm layer 63 m fraction were analysed in replicate multiple corer samples collected at the porcupine abyssal plain 48 50 n 16 30 w 4850 m water depth over a 13 yr period 1989 2002 total densities were significantly higher in 1996 2002 compared to 1989 1994 a change coincident with a spectacular rise in the density of the holothurian amperima however total densities exhibited no significant relation to seasons or any significant correlation with modelled organic matter flux the north atlantic oscillation nao index amperima densities or megafaunal assemblage composition over the same period species richness and diversity measures decreased and dominance increased although not significantly multivariate analyses revealed three assemblages represented by samples collected in 1989 1994 1996 july 1997 and october 1997 october 2002 these reflected temporal changes in the densities of higher taxa and species trochamminaceans notably a small undescribed species increased from 5 9 1989 1994 to 29 40 1996 2002 of the assemblage with a corresponding rise in absolute abundance species of hormosinacea and lagenammina also tended to increase in density from 1996 1997 onwards rotaliids dominated by alabaminella weddellensis and epistominella exigua showed a bimodal distribution over time with peak densities in may 1991 32 and september 1998 28 and lowest densities in 1996 1997 responses by these species to seasonal phytodetritus inputs probably explain the relative abundance of e exigua and to a lesser extent a weddellensis in 1989 and 1991 when phytodetritus was present a qualitative change in the phytodetrital food repackaging of food by megafauna increased megafaunal disturbance of the surficial sediment or a combination of these factors are possible explanations for the dominance of trochamminaceans from 1996 onwards the miliolid quinqueloculina sp was virtually absent in multicore samples 0 1 cm 63 m fraction from 1989 1994 peaked in september 1996 22 when degraded phytodetritus was present on core surfaces was less common in march 1997 and thereafter was relatively uncommon however horizontally sliced box core samples 0 5 cm 250 m fraction revealed that large specimens were more abundant in march 1997 and also were concentrated in deeper sediment layers than in september 1996 we suggest that quinqueloculina sp migrated to the sediment surface in response to a 1996 flux event grew and reproduced before migrating back into deeper layers as the phytodetrital food became exhausted overall the abyssal time series revealed decadal scale changes among shallow infaunal foraminifera more or less coincident with changes in the megafauna as well as indications of shorter term events related to seasonally pulsed phytodetrital inputs

pre bolling warming in santa barbara basin california surface and intermediate water records of early deglacial warmth abstract a new piston core from santa barbara basin california provides evidence of the timing magnitude and character of deglaciation including evidence of warming prior to termination ia images site md02 2503 570 m water depth consists of intermittently laminated hemipelagic sediments extending to interstadial d o event 6 34 ka that accumulated at 135 cm ka during the deglacial episode 16 75 10 ka 18 o values decreased by 3 2 in the planktonic species globigerina bulloides indicating a total warming of 8 9 c recorded by surface dwelling foraminifera inferred by removing the 1 influence of ice volume change similarly benthic species bolivina argentea and uvigerina peregrina record a 1 65 18 o decrease across the deglacial interpreted as a 2 3 c warming at upper intermediate depths 18 o values of both planktonic and benthics indicate that surface and intermediate waters began to warm 2 ka prior to termination ia beginning at 16 5 ka intermediate water warming exhibits similar structure and synchronous timing with surface waters these findings are consistent with a growing number of records from around the globe that exhibit pre bolling warming prior to termination ia and extends the record of such processes to the northern pacific

controls on detrital sedimentation in the cariaco basin during the last climatic cycle insight from clay minerals abstract a high resolution analysis of the clay mineral content of sediments of the cariaco basin spanning the last climatic cycle was performed in order to determine how the detrital sedimentation in the basin records climatic oscillations at various timescales at the scale of glacial interglacial cycles the clay mineral content records changes in the geographic origin of the detrital supply from a dominantly kaolinite and smectite rich southern source during glacial to a more illite rich northerly source during interglacials though possibly influenced by eustatic variations these changes mostly reflect the latitudinal fluctuations of the intertropical convergence zone itcz the eemian shows an increased contribution from the northern source compared to the holocene during mis3 seasonality modulates the effect of itcz position and leads to increased smectite contribution fluctuations of the smectite and kaolinite contents during dansgaard oeschger cycles reflect changes of runoff intensity enhanced supplies in kaolinite during heinrich like events and stadials also suggest remobilizations of sediments deposited on the unare platform resulting from rapid sea level variations the younger dryas is characterized by a significantly different clay mineral association reflecting a drastic modification of terrigenous supply an eolian contribution would explain this peculiar mineralogy although local contributions cannot be ruled out a similar event is noted at the mis6 5 transition pointing for the occurrence of a younger dryas like episode during termination ii

stalagmite evidence for the onset of the last interglacial in southern europe at 129 1 ka multi proxy data from an italian stalagmite constrain the commencement of full last interglacial conditions in southern europe at 129 1 ka consistent with absolutely dated records currently available from both hemispheres the post glacial transition towards warmer and wetter conditions commenced at 134 2 ka oxygen isotope evidence suggests this was interrupted briefly at 130 2 ka an event probably related to the termination ii pause associated with heinrich event 11 for most of the stalagmite the pattern of delta 18 o variation mimics the air temperature record from the vostok ice core especially through marine isotope stage 5 there is no obvious evidence for substantial early interglacial warming

latest quaternary north pacific surface water responses imply atmosphere driven climate instability a full sequence of brief interstadials dansgaard oeschger d o cycles are recorded from 60 to 25 ka in santa barbara basin california ocean drilling program hole 893a by planktonic foraminiferal isotopic and assemblage changes at unparalleled high resolution for the oceans synchronous climatic response between north pacific surface waters and the greenland ice sheet during d o cycling is strongly indicated by remarkable similarities in speed magnitude and character of rapid oceanic and atmospheric reorganizations inferred sea surface temperature warmings of as much as 5 c within a few decades and brief warming overshoots of as much as 3 c suggest involvement of an atmospheric amplification top down in situ atmospheric warming of the ocean is implied by differential responses partial decoupling in the changes recorded in surface and thermoclinal waters

variations in solar magnetic activity during the last 200 000 years is there a sun climate connection abstract the production of 10be in the earth s atmosphere depends on the galactic cosmic ray influx that in turn is affected by the solar surface magnetic activity and the geomagnetic dipole strength using the estimated changes in 10be production rate and the geomagnetic field intensity variations in solar activity are calculated for the last 200 ka large variations in the solar activity are evident with the sun experiencing periods of normal enhanced and suppressed activity the marine 18o record and solar modulation are strongly correlated at the 100 ka timescale it is proposed that variations in solar activity control the 100 ka glacial interglacial cycles however the 10be production rate variations may have been under estimated during the interval between 115 ka and 125 ka and may have biased the results future tests of the hypothesis are discussed

structure of the penultimate deglaciation along the california margin and implications for milankovitch theory the detailed structure and timing of the penultimate deglaciation are insufficiently defined yet critical for understanding mechanisms responsible for abrupt climate change here we present oxygen isotope records from planktonic and benthic foraminifera at unprecedented resolution encompassing late marine oxygen isotope stage mis 6 and termination ii ca 150 120 ka from the santa barbara basin supported by additional southern california margin records a region highly sensitive to millennial scale climate oscillations during the last deglaciation these records reveal millennial and centennial scale climate variability throughout the interval including an interstadial immediately preceding the deglaciation a brief warm event near the beginning of termination ii and a bolling allerod younger dryas like climate oscillation midway through the deglaciation recognition of these events in an oxygen isotope record from a 230th dated stalagmite allows the adoption of this radiometric chronology for the california margin records this chronology supports the milankovitch theory of deglaciation the suborbital history of climate variability during termination ii may account for records of early deglaciation

magnetic properties of deep sea sediments off southwest greenland evidence for major differences between the last two deglaciations high resolution rock magnetic data atomic mass spectroscopy 14 c dates 18 o and grain size analyses from a piston core hu90 013 013 located off southwest greenland provide a record of the last two deglaciations during termination i a welldefined interval having high volumetric magnetic susceptibility k and a low ratio of anhysteretic susceptibility to volumetric magnetic susceptibility k arm k postdates the younger dryas and the 18 o change marking the stage 2 1 boundary and correlates with sedimentological and geomorphological evidence for greenland ice sheet retreat from the coastline to the continental interior during termination ii a very similar magnetic signal coincides with the 18 o shift marking the stage 6 5 glacial interglacial transition and continues throughout substage 5e we suggest that this magnetic signal during both termination i and termination ii marks continental meltwater carried detritus from greenland if so the synchronous changes in magnetic and oxygen isotopic records at termination ii indicate very early and rapid deglaciation of greenland in contrast to the relatively late deglaciation observed for termination i distinct fluctuations in k and k arm k occur below the onset of the 18 o change at termination i where they occur at 16 900 yr b p and at termination ii these fluctuations are interpreted as due to sudden influxes of detritus into the basin caused by unpinning of ice from the continental shelf at the inception of deglaciation

sea level at the last glacial maximum evidence from northwestern australia to constrain ice volumes for oxygen isotope stage 2 new sea level information from the bonaparte gulf in northwestern australia is used to constrain the magnitude and rates of change of ice volumes during the last glacial maximum lgm the region is tectonically stable and far from the former ice covered regions the glacio hydro isostatic adjustment of the coast is therefore relatively small and the corrections for this evect are not sensitive to details of the rebound model microfossil analysis and ams radiocarbon dating of 11 gravity cores taken across the shelf and bonaparte gulf demonstrate that 1 the lgm sea levels were locally at 125 4 m 2 the lgm terminated abruptly at 19 000 cal yr bp with a rapid rise in sea level of about 15 m over the next 500 years and 3 the onset of the minimum sea levels occurred before 22 000 cal yr bp when corrected for the glacio hydro isostatic evects the increase of lgm ice volumes over the present day ice volume is 52 5 106 km3 the termination of the lgm is marked by a rapid ice discharge of 5 2 106 km3 2001 elsevier science b v all rights reserved

apparent synchroneity of submillennial scale climate events between greenland and santa barbara basin california from 30 10 ka abstract evidence is presented from odp hole 893a santa barbara basin for possible synchroneity between greenland and california margin submillennial climate change records during termination 1 and the last glacial maximum lgm planktonic foraminiferal isotope and faunal records are compared to the gisp2 18o records greenland for the interval between 30 and 10 ka using a new chronology based on 38 planktonic 14c dates apparent synchronous climatic events include interstadial is events 2 3 and 4 a broad warming trend between 21 and 19 ka and a broad cooling trend between 19 and 17 ka bolling and allerod warm episodes separated by the cooler older dryas event younger dryas cool episode and the preboreal the resulting tight correlation supports an intimate teleconnection between santa barbara basin surface waters and greenland air temperatures differences between greenland and santa barbara basin suggest that some regional variations were superimposed on the global pattern of climate change e g the pre bolling warming

brief interstadial events in the santa barbara basin ne pacific during the past 60 kyr the instability of the northern hemisphere glacial climate over the past 100 kyr has been revealed by at least 20 brief warm interstadial episodes called dansgaard oeschger events recorded in greenland ice cores1 3 and in north atlantic sedimentary records4 5 a few of these events have been recognized elsewhere6 8 here we describe a record of ocean oxygenation and circulation from the santa barbara basin in the northeast pacific ocean which correlates well with the greenland ice core records we see 19 of the 20 dansgaard oeschger events in the form of laminated sediments deposited under anoxic conditions and we can correlate at least 16 of these with the 17 ice core interstadials of the past 60 kyr thus these short term events were not restricted to the north atlantic region the events had substantial ecological and oceanographic effects in the santa barbara basin including changes in benthic faunal populations and in the age and composition of bottom waters similar ventilation changes have been seen in the gulf of california9 10 suggesting that these changes may have been widespread and synchronous along the northeast pacific margin these results suggest sensitivity of broad areas of the ocean atmosphere cryosphere system to short term climate change

a north atlantic tephrostratigraphical framework for 130 60 ka b2k new tephra discoveries marine based correlations and future challenges abstract building chronological frameworks for proxy sequences spanning 130 60 ka b2k is plagued by difficulties and uncertainties recent developments in the north atlantic region however affirm the potential offered by tephrochronology and specifically the search for cryptotephra here we review the potential offered by tephrostratigraphy for sequences spanning 130 60 ka b2k we combine newly identified cryptotephra deposits from the ngrip ice core and a marine core from the iceland basin with previously published data from the ice and marine realms to construct the first tephrostratigraphical framework for this time interval forty three tephra or cryptotephra deposits are incorporated into this framework twenty three tephra deposits are found in the greenland ice cores including nine new ngrip tephras and twenty separate deposits are preserved in various north atlantic marine sequences major minor and trace element results are presented for the new ngrip horizons together with age estimates based on their position within the ice core record basaltic tephras of icelandic origin dominate the framework with only eight tephras of rhyolitic composition found new results from marine core md99 2253 also illustrate some of the complexities and challenges of assessing the depositional integrity of marine cryptotephra deposits tephra based correlations in the marine environment provide independent tie points for this time interval and highlight the potential of widening the application of tephrochronology further investigations however are required that combine robust geochemical fingerprinting and a rigorous assessment of tephra depositional processes in order to trace coeval events between the two depositional realms

sea level change glacial rebound and mantle viscosity fornorthern europe northwestern europe remains a key region for testing models of glacial isostasy because of the good geological record of crustal response to the glacial unloading since the time of the last glacial maximum models for this rebound and associated sea level change require a detailed knowledge of the ice sheet geometry including the ice thickness through time existing ice sheet reconstructions are strongly model dependent and inversions of sea level data for the mantle response may be a function of the model assumptions thus inverse solutions for the sea level data are sought that include both ice and earth model parameters as unknowns sea level data from fennoscandia the north sea the british isles and the atlantic and english channel coasts have been evaluated and incorporated into the solutions the starting ice sheet for fennoscandia is based on a reconstruction of a model by denton hughes 1981 that is characterized by quasi parabolic cross sections and symmetry about the load centre both global northwestern europe as a whole and regional subsets of the data solutions have been made for earth model parameters and ice height scaling parameters the key results are as follows 1 the response of the upper mantle to the changing ice and water loads is spatially relatively homogenous across scandinavia the north sea and the british isles 2 this response can be adequately modelled by an effective elastic lithosphere of thickness 65 85 km and by an effective upper mantle viscosity from the base of the lithosphere to the 670 km depth seismic discontinuity of about 3 4 1020 pa s the effective lower mantle viscosity is at least an order of magnitude greater 3 the ice thickness over scandinavia at the time of maximum glaciation was only about 2000 m much less than the 3400 m assumed in the denton hughes model 4 the ice profiles are asymmetric about the centre of the ice sheet with those over the western part being consistent with quasi parabolic functions whereas the ice heights over the eastern and southern regions increase much more slowly with distance inwards from the ice margin

persistent suborbital climate variability in marine isotope stage 5 and termination ii new surface water records from two high sedimentation rate sites located in the western subtropical north atlantic near the axis of the gulf stream provide clear evidence of suborbital climate variations through marine isotope stage mis 5 persisting even into the warm peak of the interglaciation substage 5e we found that the amplitude of suborbital climate oscillations did not vary significantly for the whole of mis 5 implying that ice volume has little or no influence on the amplitude of suborbital climate variability in this region although some records suggest that longer suborbital variations 4 10 kyr during mis 5 are linked to deepwater changes none of the existing records is of sufficient resolution to assess if a linkage occurred for oscillations shorter than 4 kyr however when examined in conjunction with published data from the norwegian sea new evidence from the subpolar north atlantic suggests that coupled surface deepwater oscillations occurred during the penultimate deglaciation this supports the hypothesis that during glacial and deglacial times ocean ice interactions and deepwater variability amplify suborbital climate change at higher latitudes we suggest that during the penultimate deglaciation the north atlantic deepwater source varied between nordic sea and open north atlantic locations in parallel with surface temperature oscillations

orbital controls on the el nino southern oscillation and the tropical climate the global synchroneity of glacial interglacial events is one of the major problems in understanding the link between milankovitch forcing and the climate of the late quaternary in this study we isolate a part of the climate system the tropical pacific and test its sensitivity to changes in solar forcing associated with changes in the earth s orbital parameters we use a simplified coupled ocean atmosphere model that is run for the past 150 000 years and forced with milankovitch changes in the solar insolation this system responds primarily to the precessional cycle in solar forcing and is capable of generating a mean response to the changes in the seasonal distribution of solar radiation even while the annual mean insolation is roughly constant the mean response to the precessional forcing is due to an interaction between an altered seasonal cycle and the el nifio southern oscillation enso changes in the enso behavior result in a mean tropical climate change the hypothesis is advanced that such a change in the tropical climate can generate a globally synchronous climate response to milankovitch forcing

evidence for last interglacial chronology and environmental change from southern europe establishing phase relationships between earth system components during periods of rapid global change is vital to understanding the underlying processes it requires records of each component with independent and accurate chronologies until now no continental record extending from the present to the penultimate glacial had such a chronology to our knowledge here we present such a record from the annually laminated sediments of lago grande di monticchio southern italy using this record we determine the duration 17 70 0 20 ka and age of onset 127 20 1 60 ka b p of the last interglacial as reflected by terrestrial ecosystems this record also reveals that the transitions at the beginning and end of the interglacial spanned only 100 and 150 years respectively comparison with records of other earth system components reveals complex leads and lags during the penultimate deglaciation phase relationships are similar to those during the most recent deglaciation peaks in antarctic warming and atmospheric methane both leading northern hemisphere terrestrial warming it is notable however that there is no evidence at monticchio of a younger dryas like oscillation during the penultimate deglaciation warming into the first major interstadial event after the last interglacial is characterized by markedly different phase relationships to those of the deglaciations warming at monticchio coinciding with antarctic warming and leading the atmospheric methane increase diachroneity is seen at the end of the interglacial several global proxies indicate progressive cooling after 115 ka b p whereas the main terrestrial response in the mediterranean region is abrupt and occurs at 109 50 1 40 ka b p

timing duration and transitions of the last interglacial asian monsoon thorium 230 ages and oxygen isotope ratios of stalagmites from dongge cave china characterize the asian monsoon and low latitude precipitation over the past 160 000 years numerous abrupt changes in 18o 16o values result from changes in tropical and subtropical precipitation driven by insolation and millennial scale circulation shifts the last interglacial monsoon lasted 9 7 1 1 thousand years beginning with an abrupt less than 200 years drop in 18o 16o values 129 3 0 9 thousand years ago and ending with an abrupt less than 300 years rise in 18o 16o values 119 6 0 6 thousand years ago the start coincides with insolation rise and measures of full interglacial conditions indicating that insolation triggered the final rise to full interglacial conditions

chronology reconstruction for the disturbed bottom section of the gisp2 and the grip ice cores implications for termination ii in greenland and d 18 oatm in the trapped gases our reconstructed ages for basal ice samples are based on comparison of published measurements of ch4 and d 18 oatm from the disturbed section of the grip and gisp2 cores with the same properties in the vostok ice core ngrip d 18 oice values are also used to constrain the chronology during the end of marine isotope stage 5e for each sample we assign an age that represents the unique or most probable time of gas trapping given its gas composition of 157 samples with ch4 and d 18 oatm data 10 give unique ages twenty five newly measured values of the triple isotope composition of o2 from the disturbed section of the gisp2 core add a third time dependent gas property that agrees with our reconstruction our reconstruction supports earlier conclusions of landais et al 2003 that the disturbed section primarily includes ice from the last interglacial mis 5e and the penultimate glacial period mis 6 the oldest ice in the basal layer of gisp2 and grip has an age 237 ka the climate history we derive suggests that the last interglacial at summit greenland around 127 ka was slightly warmer than the current interglacial period reduction of various ion concentrations in ice and thickening of the ice sheet during termination ii was similar to that in termination i

millennial scale variability to 735 ka high resolution climate records from santa barbara basin ca 1 determining the ultimate cause and effect of millennial scale climate variability remains an outstanding problem in paleoceanography partly due to the lack of high resolution records predating the last glaciation recent cores from santa barbara basin provide 2500 5700 year windows of climate with 10 50 year resolution ages for three cores determined by seismic stratigraphic correlation oxygen isotope stratigraphy and biostratigraphy date to 293 ka mis 8 450 ka mis 12 and 735 ka mis 18 these records sample the late pleistocene during which the 100 kyr cycle strengthened and the magnitude of glacial interglacial cyclicity increased thus these records provide a test of the dependence of millennial scale behavior on variations in glacial interglacial cyclicity the stable isotopic 18o composition of planktonic foraminifera shows millennial scale variability in all three intervals with similar characteristics duration cyclicity to those previously documented during mis 3 at this site stadial g bulloides 18o values are 2 75 1 75 average 2 25 and interstadial values are 1 75 0 5 average 1 with rapid decadal scale interstadial and stadial initiations of 1 2 as in mis 3 interstadials lasted 250 1600 years and occurred every 650 1900 years stadial paleotemperatures were 3 5 9 5 c and interstadial paleotemperatures were 7 5 13 c upwelling evidenced by planktonic foraminiferal assemblages and 13c increased during interstadials similar to mis 3 high productivity during some stadials was reminiscent of the last glacial maximum this study builds upon previous records in showing that millennial scale shifts were an inherent feature of northern hemisphere glacial climates since 735 ka and they remained remarkably constant in the details of their amplitude cyclicity and temperature variability

tephra correlations and climatic events between the mis6 5 transition and the beginning of mis3 in theopetra cave central greece abstract three cryptotephra layers associated with important periods of climatic change were identified in the middle palaeolithic sequence of theopetra cave greece the lower cryptotephra layer thp tii5 is correlated with the p 11 pantellerian eruption dated to 128 131 ka this cryptotephra postdates a thick sequence of combustion layers that show a complex vegetation succession quite similar to that of the last deglaciation succession in the cave two other cryptotephras thp tii10 and thp tii12 are correlated with the nisyros upper pumice and the pantellerian y6 green tuff dated to 50 ka and 45 7 ka respectively this sequence confirms the position of the nisyros upper tephra below the pantellerian green tuff in the volcanic event stratigraphy of the mediterranean moreover these two upper cryptotephras bracket an extended combustion layer with interstadial vegetation characteristics that may be coincident with the complex greenland interstadial 13 14 on the basis of this new chronology it can be deduced that the intensity of occupation and presence or absence of humans in the cave were closely related to climatic changes in addition a remarkable similarity in the pattern of occupational intensity during the last two deglaciations can be suggested

last interglacial palaeovegetation palaeoenvironments and chronology a new record from lago grande di monticchio southern italy abstract the sediments of lago grande di monticchio southern italy extend continuously from the present back to the penultimate glacial stage and have an independent lamination based chronology of high precision and accuracy results are presented here from a detailed palynological investigation of that part of the sediment sequence that extends from the last millennia of the penultimate glacial stage to the first stadial following the last interglacial li quantitative palaeovegetation and palaeoclimate reconstructions made from the palynological data are also presented the onset of the li is dated to 127 20 ka bp a date that is consistent with other recent estimates the duration of the li is estimated to have been 17 70 ka the palaeovegetation record indicates a transition period of 3 35 ka at the end of the penultimate glacial stage prior to the onset of the li no younger dryas like oscillation is recorded although the transition was interrupted by a brief event lasting ca 250 years during which pollen of woody taxa was reduced in abundance steppe vegetation dominated during the latter part of the penultimate full glacial stage but was replaced progressively by wooded steppe during the transition although the development of forest cover marked the onset of the li the forests were relatively open or discontinuous during the first 2 65 ka closing progressively thereafter and generally dominating between 123 00 and 109 50 ka bp the end of the li is dated to 109 50 ka bp after which date forest cover became discontinuous and wooded steppe or steppe dominated during the 1 90 ka of the subsequent stadial as might be expected given the location of the lake the composition of the li forests differs markedly from those recorded from northern europe as well as from those recorded at other localities in southern europe the palaeoclimate reconstructions reveal complex changes in seasonality the maximum coldest month mean temperatures being between 125 70 ka bp and 123 00 ka bp whereas maxima for both annual temperature sum and the ratio of actual to potential evapotranspiration were between 120 60 ka bp and 115 80 ka bp reconstructed zonal mean values for all three climatic variables in the zones in which they peak exceed values at the locality today comparison with other palaeovegetation records of the li from europe reveals that forest cover generally opened up north of the alpine region probably ca 115 ka bp coinciding with a marked decrease in sea surface temperatures in the nordic seas this probably corresponds to a marked shift in forest composition at lago grande di monticchio at 115 80 ka bp with an associated reconstructed decrease of ca 5 c in coldest month mean temperature nonetheless forest continued to dominate at lago grande di monticchio until 109 50 ka bp such comparisons also reveal considerable complexity in the geographical and altitudinal patterns of change in palaeovegetation during the li such complexity is to be expected given the parallel complexity of holocene changes systematic comparisons between reconstructions of palaeoclimate are hampered by a lack of consistency in approach and in the variables reconstructed further insight into this complexity of palaeoclimate development during the li requires a synthesis of the available data and application of a consistent reconstruction approach that also provides robust estimates of the uncertainty in the reconstructed values

abrupt termination of marine isotope stage 16 termination vii at 631 5 ka in santa barbara basin california the marine isotope stage 16 15 boundary termination vii is the first deglacial warming step of the late quaternary following the mid pleistocene transition mpt when 41 kyr climatic cycles shifted to strong 100 kyr cycles the detailed structure of this important climatic event has remained unknown until now core mv0508 19jpc from santa barbara basin california contains a decadal scale climatic and geochemical sediment record of 4000 years duration that includes the early part of this deglacial episode this record reveals that the climatic shift during the early deglacial occurred rapidly 700 years in a progression of three abrupt warming steps the onset of marine isotope stage mis 15 was remarkably abrupt with 4 5 c sea surface warming in 50 years the deglacial sequence contains the well dated lava creek tephra 631 3 4 ka from yellowstone caldera used to date the onset of termination vii at 631 5 ka the late mis 16 and early mis 15 interval exhibits multiple decadal scale negative excursions in 13c of planktic foraminifera likely the result of repeated discharges of methane from methane hydrates associated with both ocean warming and low sea level a warm interstadial that interrupts late mis 16 is marked by elevated concentrations of redox sensitive elements indicating sulfidic oxygen deficient bottom and pore waters and elevated concentrations of total organic carbon and cd reflecting increased surface productivity unlike younger sediments on the california margin these indicators of increased productivity and low dissolved oxygen do not consistently correspond with each other or with preserved laminations possibly reflecting instability of a still evolving ocean atmosphere system following the mpt

meltwater events and the mediterranean reconnection at the saalian eemian transition in the black sea abstract the last glacial interglacial transition or termination i t i is well documented in the black sea whereas little is known about climate and environmental dynamics during the penultimate termination t ii here we present a multi proxy study based on a sediment core from the se black sea covering the penultimate glacial and almost the entire eemian interglacial 133 5 0 7 122 5 1 7 ka bp proxies comprise ice rafted debris ird o and sr isotopes as well as sr ca mg ca and u ca ratios of benthic ostracods organic and inorganic sediment geochemistry as well as tex 86 and u k 37 derived water temperatures the ending penultimate glacial mis 6 133 5 to 129 9 0 7 ka bp is characterised by mean annual lake surface temperatures of about 9 c as estimated from the tex 86 palaeothermometer this period is impacted by two black sea melt water pulses bswp ii 1 and 2 as indicated by very low sr ca ostracods but high sedimentary k al values anomalously high radiogenic 87 sr 86 sr ostracod values max 0 70945 during bswp ii 2 suggest a potential himalayan source communicated via the caspian sea the t ii warming started at 129 9 0 7 ka bp witnessed by abrupt disappearance of ird increasing 18 o ostracod values and a first tex 86 derived temperature rise of about 2 5 c a second abrupt warming step to ca 15 5 c as the prelude of the eemian warm period is documented at 128 3 ka bp the mediterranean black sea reconnection most likely occurred at 128 1 0 7 ka bp as demonstrated by increasing sr ca ostracods and u ca ostracods values the disappearance of ostracods and toc contents 2 document the onset of eemian sapropel formation at 127 6 ka bp during sapropel formation tex 86 temperatures dropped and stabilised at around 9 c while u k 37 temperatures remain on average 17 c this difference is possibly caused by a habitat shift of thaumarchaeota communities from surface towards nutrient rich deeper and colder waters located above the gradually establishing halo and redoxcline

climatic and hydrologic oscillations in the owens lake basin and adjacent sierra nevada california oxygen isotope and total inorganic carbon values of cored sediments from the owens lake basin california indicate that owens lake overflowed most of the time between 52 500 and 12 500 carbon 14 14 c years before present b p owens lake desiccated during or after heinrich event h1 and was hydrologically closed during heinrich event h2 the magnetic susceptibility and organic carbon content of cored sediments indicate that about 19 sierra nevada glaciations occurred between 52 500 and 23 500 14 c years b p most of the glacial advances were accompanied by decreases in the amount of discharge reaching owens lake comparison of the timing of glaciation with the lithic record of north atlantic core v23 81 indicates that the number of mountain glacial cycles and the number of north atlantic lithic events were about equal between 39 000 and 23 500 14 c years b p

collapse of the california current during glacial maxima linked to climate change on land time series of alkenone unsaturation indices gathered along the california margin reveal large 4 to 8 c glacial interglacial changes in sea surface temperature sst over the past 550 000 years interglacial times with ssts equal to or exceeding that of the holocene contain peak abundances in the pollen of redwood the distinctive component of the temperate rainforest of the northwest coast of california in the region now dominated by the california current ssts warmed 10 000 to 15 000 years in advance of deglaciation at each of the past five glacial maxima ssts did not rise in advance of deglaciation south of the modern california current front glacial warming along the california margin therefore is a regional signal of the weakening of the california current during times when large ice sheets reorganized wind systems over the north pacific both the timing and magnitude of the sst estimates suggest that the devils hole nevada calcite record represents regional but not global paleotemperatures and hence does not pose a fundamental challenge to the orbital milankovitch theory of the ice ages

climatic variability during the last interglacial inferred from geochemical proxies in the lake el gygytgyn sediment record the last interglacial period lip is often regarded as a good analogue for potential climatic conditions under predicted global warming scenarios despite this there is still debate over the nature duration and frequency of climatic changes during this period one particularly contentious issue has been the apparent evidence of climatic instability identified in many marine cores but seemingly lacking from many terrestrial archives especially within the arctic a key region for global climate change research in this paper geochemical records from lake el gygytgyn north eastern russia are used to infer past climatic changes during the lip from within the high arctic with a sampling resolution of 20 90 years these records offer the potential for detailed high resolution palaeoclimate reconstruction this study shows that the lip commenced in central chukotka 129 thousand years ago ka with the warmest climatic conditions occurring between 128 and 127 ka before being interrupted by a short lived cold reversal mild climatic conditions then persisted until 122 ka when a marked reduction in the sedimentation rate suggests a decrease in precipitation a further climatic deterioration at 118 ka marks the return to glacial conditions this study highlights the value of incorporating several geochemical proxies when inferring past climatic conditions thus providing the potential to identify signals related to environmental change within the catchment we also demonstrate the importance of considering how changes in sedimentation rate influence proxy records in order to develop robust palaeoenvironmental reconstructions

sea level reversal during termination ii the termination of the penultimate glacial period tii shows both similarities and differences to the last termination ti both terminations show significant cold reversals in the postglacial warming trend ti consists of a continuously increasing sea level trend whereas tii may demonstrate a sea level reduction midway through the termination we present a new continuous sea level record for tii derived from red sea 18 o records that supports the existence of the tii sea level reversal the record gives an unprecedented look at the structure of the tii sea level reversal which consists of an early highstand lasting several millennia in duration followed by a 30 12 m to 40 12 m reduction in sea level and a stillstand of several millennia before the final sea level rise to the marine oxygen isotope stage mis 5e interglacial we suggest that there is a link between the sea level reversal and internal millennial scale variability in the climate system

deglacial laminated facies on the nw european continental margin the hydrographic significance of british irish ice sheet deglaciation and fleuve manche paleoriver discharges we have compiled results obtained from four high sedimentation rate hemipelagic sequences from the celtic sector of the nw european margin ne atlantic to investigate the paleoceanographic and paleoclimatic evolution of the area over the last few climatic cycles we focus on periods characteristic of deglacial transitions we adopt a multiproxy sedimentological geochemical and micropaleontological approach applying a sampling resolution down to ten microns for specific intervals the investigation demonstrates the relationships between the bay of biscay hydrography and the glacial deglacial history of both the proximal british irish ice sheet biis and the western european continent we identify recurrent phases of laminae deposition concurrent with major biis deglacial episodes in all the studied cores evidence for abrupt freshwater discharges into the open ocean highlights the influence of such events at a regional scale we discuss their impact at a global scale considering the present and past key location of the bay of biscay versus the atlantic meridional overturning circulation amoc

tropical forcing of north pacific intermediate water distribution during late quaternary rapid climate change abstract evidence is presented demonstrating intermediate water 500 m temperature variability at odp hole 893a in santa barbara basin during submillennial climate change 11 60 ka benthic 18 o oscillations are considered to result primarily from shifts in intermediate water temperature at the site detailed comparison of both benthic and planktonic records from the basin provide crucial evidence for differing surface and intermediate water mass temporal responses to rapid climate change gradual warming of intermediate water compared to abrupt cooling suggests mechanistic differences between processes controlling north pacific intermediate water expansion and contraction relative to southern component intermediate waters comparisons suggest intermediate water warming preceded by 60 200 years the most rapid interval of surface warming inferred to be associated with north pacific atmospheric reorganization tropical forcing of sea level anomalies in the eastern pacific via trade wind strength may control california undercurrent flow 300 500 m and be the cause of early intermediate water warming in santa barbara basin

the middle pleistocene al mahruqah formation in the murzuq basin northern sahara libya evidence for orbitally forced humid episodes during the last 500 000 years abstract geological and geomorphological work in the endorheic murzuq basin fezzan in the northern sahara desert sw libya has revealed that the middle pleistocene al mahruqah formation consists of at least four limestone beds at four distinct elevations the corresponding limestone beds are named from oldest to youngest the antalkhata member the brak member the bi r az zallaf member and the aqar member the four members are interpreted as lacustrine deposits and they are well distinguished by their spatial extent and lithology twenty five radiometric and thermal ionisation mass spectrometric tims 230th u ages ranging from about 490 130 ka have been determined on these lacustrine limestones according to these radiometric 230th u ages the accumulation of the four limestone members of the al mahruqah formation followed the orbitally forced milankovitch eccentricity cycle of 100 ka during at least the last 400 ka the four members formed in humid episodes of several tens of thousands of years duration when large lakes might have existed the 13c and 18o values from samples of the four members of the al mahruqah formation provide independent genetic evidence on the lacustrine origin of the deposits in the murzuq basin the spatial extent of the limestone deposits and thus the intensity of the humid episodes decreases at least from the brak member to the aqar member from about 52 000 km2 to 1400 km2 respectively in spite of the limited precision and reliability of the new 230th u ages it seems possible that short humid episodes interrupted the intervening arid episodes other long term palaeohydrological records from northern and southern africa as well as the mediterranean region support the palaeoclimatic results from the murzuq basin

rapid climate change from north andean lake fuquene pollen records driven by obliquity implications for a basin wide biostratigraphic zonation for the last 284 ka this paper compares a new super high resolution pollen record from a central location in lake fuquene 4 n with 3 pollen records from marginal sites from the same lake basin located at 2540 m elevation in the eastern cordillera of colombia we harmonized the pollen sum of all records and provided previously published records of climate change with an improved age model using a new approach for long continental pollen records we dissociated from subjective curve matching and applied a more objective procedure including radiocarbon ages cyclostratigraphy and orbital tuning using the new 284 ka long fuquene basin composite record fq bc as the backbone groot et al 2011 we showed that a common 9 m cycle in the arboreal pollen percentage ap records reflects obliquity forcing and drives vegetational and climatic change the ap records were tuned to the 41 kyr component filtered from standard benthic 18o lr04 record changes in sediment supply to the lake are reflected in concert by the four records making frequency analysis in the depth domain an adequate method to compare records from the same basin we calibrated the original 14c ages and used where necessary biostratigraphic correlation i e for records shorter than one obliquity cycle pollen records from the periphery of the lake showed changes in the abundance of alnus and weinmannia forests more clearly while centrally located record fq 9c shows a more integrated signal of regional vegetation change the revised age models show that core fq 2 reflects the last 44 ka and composite record fq 7c the last 85 5 ka marginally located core fq 3 has an age of 133 ka at 32 m core depth and the lowermost 11 m of sediments appear of older but unknown age the longest record fq bc shows 60 yr resolution over the period of 284 27 ka all pollen records are in support of a common regional vegetation development leading to a robust reconstruction of long series of submillennial climate oscillations reflecting dansgaard oeschger do cycles reconstructed climate variability in the tropical andes since marine isotope stage mis 8 compares well with ngrip 18o based epica dome c d based and the mediterranean sea surface temperature record md01 2443 44 uk 37 based underpinning the global significance of the climate record from this tropical andean lake a basin wide biostratigraphy is presented and we concluded although with varying robustness that each core is representative of regional vegetational and climatic change

the structure of termination ii penultimate deglaciation and eemian in the north atlantic abstract a study of the 140 100 ka interval in core t90 9p from the north atlantic 45 n 25 w based on analysis of oxygen and carbon isotope records from planktonic and benthonic foraminifera and from the bulk sediment fine fraction facilitates a detailed paleoceanographic reconstruction of the penultimate deglaciation termination ii and of the eemian interglacial 18o stage 5e the first step of termination ii was characterised by low productivity and a mixed water column which was a remnant of glacial conditions a 3 ka period of relatively stable conditions with a stratified water column termination ii pause occurred half way through termination ii and preceeded a second and more rapid climatic shift the end of the deglaciation eemian maximum i e isotopic event 5 53 initiated the establishment of strong seasonal water column stratification north atlantic deep water nadw production remained low during the complete glacial interglacial transition after the eemian maximum nadw prodution was restored and bottom waters remained quite stable during the course of the eemian while surface waters gradually cooled in the second half of the stage a short surface water cooling event accompanied by a reduced seasonal water column stratification and nutrient instability occurred at approximately 117 ka bp

ice ages the california current and devils hole at the end of an ice age climate changes across the globe but this response is not uniform in some parts of the world oceanic and atmospheric temperatures started to rise well before continental ice sheets began to melt in his perspective lea 1 highlights the report by herbert et al 2 who show that ocean temperatures in the california current led ice volume change by 10 000 to 15 000 years the data support earlier results from a terrestrial record at devils hole helping to reconcile them with the leading theory of ice age cycles 1 http www sciencemag org cgi content full 293 5527 59 2 http www sciencemag org cgi content short 293 5527 71

evolution of millennial scale climate variability during the mid pleistocene 1 we use the oxygen isotopic composition of planktonic foraminifera globigerinoides ruber white from ocean drilling program site 1058 in the subtropical northwestern atlantic to construct a high resolution 800 year climate record spanning the mid pleistocene climate transition 410 ka to 1350 ka we investigate whether or not millennial scale instabilities in the proxy record are associated with the extent of continental glaciation g ruber 18o values display high frequency fluctuations throughout the record but the amplitude about mean glacial and interglacial 18o values increases at marine isotope stage mis 22 880 ka and is highest during mis 12 these observations support that millennial scale climate instabilities are associated with ice sheet size time series analysis illustrates that these variations have significant concentration of spectral power centered on periods of 10 12 ka and 5 ka the timing of these fluctuations agrees well or coincides with the periodicities of the second and fourth harmonics respectively of precessional forcing at the equator an insolation based origin of the millennial scale instabilities would be independent of ice volume and explains the presence of these fluctuations before the mid pleistocene climate transition as well as during interglacial intervals e g mis 37 and 17 because the amplitude of the millennial scale variations increases during the mid pleistocene transition feedback mechanisms associated with the growth of large 100 ka paced polar ice sheets may be important amplifiers of regional surface water hydrographic changes

multivariate anomaly modeling of primary geochemical halos by u spatial statistic algorithm development a case study from the sari gunay epithermal gold deposit iran abstract an accurate separation of anomalous areas values in primary geochemical halos with heterogeneous spatial variations requires an appropriate algorithm that considers the complex patterns and multivariate relationships of the input geochemical data there are several problems in multivariate modeling of geochemical compositional data because such data present spurious values of spatial correlation between the variables to address this problem this paper proposes an improved u spatial statistic algorithm for 3d multivariate anomaly modeling of the geochemical dataset with compositional nature at the sari gunay epithermal gold deposit nw iran to perform 3d multivariate modeling isometric logarithmic ratio ilr as an effective method to transform compositional data from the simplex to real space and minimum maximum autocorrelation factor maf as a multivariate geostatistical method were used in an integrated analysis in comparison to the other separation techniques this integrated approach has an advantage to control the heterogeneous spatial variations in the input data in this approach we improved the u spatial statistic method by using the variogram tool theory by using this approach we identified the primary geochemical haloes associated with au as sb hg front halo elements cu ag pb near ore halo elements and ni co tail halo elements at the sari gunay gold depsoit the results were validated by using contrast coefficient and exploratory index tools by examining the 3d multivariate primary anomalous geochemical halos zones of possible hidden epithermal gold and porphyry copper gold mineralizations were recognized at this deposit for future exploration

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr