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

a 160 k y old record of el nino southern oscillation in marine production and coastal runoff from santa barbara basin california usa a 160 k y old laminated sediment record from the santa barbara basin california analyzed using scanning electron microscope techniques provides a history of interannual variability of marine production and coastal runoff we used backscatter electron imagery to measure the components of the varve these include a terrigenous lamina formed by seasonal runoff from winter rains together with a diatomaceous lamina that records marine production during the spring and early summer spectral analysis of terrigenous and diatomaceous laminae thickness reveals significant periodicities of 3 1 and 8 4 yr in the terrigenous series these are indistinguishable within the frequency resolution of the spectra from significant periodicities of 3 5 and 7 6 yr in the diatomaceous series the 3 1 and 3 5 yr periodicities record el nino modulation of coastal runoff and marine production the 8 4 and 7 6 yr periodicities are consistent with modulation by strong to very strong el nino events this is supported by the results of cross spectral analysis of the terrigenous and diatomaceous records which reveal inverse or antiphase relationships at 3 5 and 7 6 yr our work adds to a body of evidence that suggests that el nino has been a persistent feature of late quaternary climate variability

the evolution of oceanic and atmospheric anomalies in the northeast pacific during the el nino and la nina events of 1995 2001 abstract from late 1995 through early 2001 three major interannual climate events occurred in the tropical pacific the 1995 97 la nina ln 1997 98 el nino en and 1998 2001 ln we analyze atmospheric and upper oceanic anomalies in the northeast pacific nep during these events and compare them to anomalies both elsewhere in the north and tropical pacific and to typical en and ln anomaly patterns the atmospheric and oceanic anomalies varied strongly on intraseasonal and interannual scales during the 1995 97 ln and 1997 98 en the northeast pacific was dominated by negative slp and cyclonic wind anomalies and by upper ocean temperature and sea surface height ssh anomalies the latter were positive along the north american west coast and in the nep thermal anomaly pool between hawaii vancouver island and baja california and negative in the central north pacific this atmospheric oceanic anomaly pattern is typical of en an eastward shift in the atmospheric teleconnection from east asia created en like anomalies in the nep during the 1995 97 ln well before the 1997 98 en had begun the persistence of negative sea level pressure slp and cyclonic wind anomalies in the nep during the 1997 98 en intensified pre existing upper oceanic anomalies atmospheric anomalies were shifted eastward during late 1996 early 1998 leading to a similar onshore shift of oceanic anomalies this produced exceptionally strong positive upper ocean temperature and ssh anomalies along the west coast during the 1997 98 en and explains the unusual coastal occurrences of several species of large pelagic warm water fishes the growth and eastward shift of these pre existing anomalies does not appear to have been linked to tropical pacific en anomalies until late 1997 when a clear atmospheric teleconnection between the two regions developed prior to this remote atmospheric impacts on the nep were primarily from east asia as the 1998 2001 ln developed nep anomalies began reversing toward the typical ln pattern this led to predominantly negative slp and cyclonic wind anomalies in the nep and upper ocean temperature and ssh anomalies that were mainly negative along the west coast and positive in the central north pacific the persistence of these anomalies into mid 2001 and a number of concurrent biological changes in the nep suggest that a decadal climate shift may have occurred in late 1998 during 1995 2001 nep oceanic anomalies tracked the overlying atmospheric anomalies as indicated by the maintenance of a characteristic spatial relationship between these anomalies in particular wind stress curl and ssh anomalies in the nep maintained an inverse relationship that strengthened and shifted eastward toward the west coast during late 1996 early 1998 this consistent relationship indicates that anomalous ekman transport driven by regional atmospheric forcing was an important contributor to temperature and ssh anomalies in the nep and ccs during the 1997 98 en other studies have shown that coastal propagations originating from the tropical pacific also may have contributed to coastal nep anomalies during this en our results indicate that at least some of this coastal anomaly signal may have been generated by regional atmospheric forcing within the nep

sea surface temperature changes in the southern california borderlands during the last glacial interglacial cycle a variety of evidence suggests that average sea surface temperatures ssts during the last glacial maximum in the california borderlands region were significantly colder than during the holocene planktonic foraminiferal 18o evidence and average sst estimates derived by the modern analog technique indicate that temperatures were 6 10 c cooler during the last glacial relative to the present the glacial plankton assemblage is dominated by the planktonic foraminifer neogloboquadrina pachyderma sinistral coiling and the coccolith coccolithus pelagicus both of which are currently restricted to subpolar regions of the north pacific the glacial interglacial average sst change determined in this study is considerably larger than the 2 c change estimated by climate long range investigation mapping and prediction climap 1981 we propose that a strengthened california current flow was associated with the advance of subpolar surface waters into the borderlands region during the last glacial

devils hole nevada δ18o record extended to the mid holocene abstract the mid to late pleistocene devils hole 18 o record has been extended from 60 000 to 4500 yr ago the new 18 o time series in conjunction with the one previously published is shown to be a proxy of pacific ocean sea surface temperature sst off the coast of california during marine oxygen isotope stages mis 2 and 6 the devil hole and sst time series exhibit a steady warming that began 5000 to 10 000 yr prior to the last and penultimate deglaciations several possible proximate causes for this early warming are evaluated the magnitude of the peak 18 o or sst during the last interglacial lig is significantly greater 1 per mill and 2 to 3 c respectively than the peak value of these parameters for the holocene in contrast benthic 18 o records of ice volume show only a few tenths per mill difference in the peak value for these interglacials statistical analysis provides an estimate of the large shared information variation between the devils hole and eastern pacific sst time series from 41 to 2 n and enforces the concept of a common forcing among all of these records the extended devils hole record adds to evidence of the importance of uplands bordering the eastern pacific as a source of archives for reconstructing pacific climate variability

anomalous north pacific atmospheric circulation and large winter floods in the southwestern united states abstract specific anomalous atmospheric circulation conditions over the north pacific are conducive to the occurrence of the largest winter floods 10 yr return period on rivers in six hydroclimatic subregions of arizona and southern utah nevada and california composite maps of anomalies in daily 700 mb heights indicate that floods in all of the subregions are associated with a low pressure anomaly off the california coast and a high pressure anomaly in the vicinity of either alaska or the aleutian islands of these two major circulation features the presence of the low is the controlling factor in determining whether large floods will occur shifts in the locations of the low and high pressure anomalies over the north pacific appear to control which subregions experience floods with high elevation topographic features and proximity to air masses forming a major influence over the specific atmospheric circulation conditions that generate large floods in each hydroclimatic region concerning the int

late quaternary oceanography of the mouth of the gulf of california the polycystine connection the mouth of the gulf of california is a region where three principal water masses converge the equatorial water the water associated with the california current and the water from the gulf itself these water masses exhibit a complex interaction which has been recorded by the polycystine radiolarian distribution patterns defined in the underlying sediments the occurrence in the gulf of water associated with the california current is indicated by the distribution of cycladophora davisiana ehrenberg while the occurrence of the equatorial water is characterized by high abundance of tetrapyle octacantha muller where the california current meets the equatorial water a water mass boundary is formed and this is depicted by the distribution of druppatractus cf pyriformis bailey micropaleontological analysis of six sedimentary gravity cores located along the mouth of the gulf of california correlated through 18o stratigraphy show that from approximately 33 000 to 15 500 years ago the california current frequently invaded the mouth of the gulf displacing the water mass boundary system and the equatorial water southward these oceanographic events preceded the global climatic changes indicated by the 18o stratigraphy occurring first in the surface and subsurface water in the mouth of the gulf and then in the deep waters

sea level during the penultimate interglacial period based on a submerged stalagmite from argentarola cave italy accurate constraints are presented for the absolute age duration and sea level for the highstand corresponding to marine isotope stage mis 7 1 our work is based on a stalagmite collected in a currently submerged cave from italy argentarola cave flooding of this coastal cave is clearly marked within the stalagmite by a thick marine overgrowth of serpulid worms precise uranium thorium u th ages measured by thermal ionization mass spectrometry suggest that the stalagmite growth varied in phase with climate during mis 7 2 and mis 6 the penultimate glacial period in addition the period of marine transgression is bracketed between 202 and 190 kyr bp defining a mis 7 1 duration of 11 2 kyr comparison with previous studies provides a new constraint on the sea level during mis 7 1 that has approximately remained between 318 and 39 m relative to present sea level the timing of the mis 7 1 highstand is in full agreement with the specmap chronology which contrasts with the growing body of evidence showing a significant phase difference for mis 5 5 a tempting conclusion is that second order sea level highstands such as mis 7 1 may be purely driven by astronomical changes in contrast with major terminations such as termination ii atmospheric co2 levels may partly explain this contrast since the two sea level transitions mis 7 2 7 1 and mis 6 5 5 are characterized by very different co2 rises 20 vs 100 ppm fl 2002 elsevier science b v all rights reserved

late glacial to holocene changes in winds upwelling and seasonal production of the northern california current system abstract a core 120 km off the coast of southern oregon was examined for changes in lithology diatoms and pollen over the past 30 000 yr primary production during the late pleistocene was about half that of the holocene evidence from diatoms and pollen indicates that summer upwelling was much weaker implying an absence of strong northerly winds early pliocene diatoms found throughout the late pleistocene section were probably derived from diatomites east of the cascades and provide evidence for strong easterly winds over a dry continental interior the findings verify predictions of a climate model based on glacial maximum conditions there is no compelling evidence for a climatic reversal corresponding to the european younger dryas chron during the early holocene 9000 7000 yr b p there may have been years when winds were insufficiently strong to support upwelling so that warm stratified waters lay closer to the coast

millennial climate oscillations in ne pacific surface waters over the last 82 kyr new evidence from alkenones 1 a climate instability in the last glacial corresponding to dansgaard oeschger d o events has been already recognized in the california margin in northeast pacific detailed sea surface temperature sst changes in this region however have not been so far well elucidated here we report estimates of alkenone derived ssts with the do time scale from odp hole 1017e off point conception over the last 80 kyr our results show that alkenone ssts clearly record d o and heinrich events we also found that alkenone ssts during 82 58 ka and 18 15 ka were considerably higher and those in 15 12 ka were lower than those derived from 18o of planktonic foraminifera these results appear to reflect fluctuations of water masses

biomarker temperature estimates for modern and last glacial surface waters of the california current system between 33 and 42 n sea surface temperature sst estimates were made using data for c37 39 alkenones analyzed in modern and glacial age intervals of sediment cores collected along an east west 42 n from 125 to 132 w and a north south 41 33 n transect of the california current system ccs the prymnesiophyte biomarker results suggest that surface waters warmed significantly throughout this region since the last glacial maximum lgm but the magnitude of warming varied spatially stratigraphic profiles from four sediment cores along the north south transect indicate the warming period was confined to the glacial interglacial transition 15 10 ka with sst reaching a maximum value at 10 ka and maintaining a uniformly high value throughout the holocene comparison of estimates derived from analysis of modern and lgm sediment intervals indicates the magnitude of the sst change was minimal for locations south of about 36 n 1 2 c and increased significantly 3 5 c north of this latitude using a simple heat balance model we calculate from the latitudinal gradient in sst that southward flow in the california current system during the lgm was about 60 of that measured today at 36 n our findings support the conclusion of others based on pollen data that coastal upwelling in the region of the northeast pacific off northern california was significantly reduced or even completely shutdown during the lgm

biogenic sedimentation beneath the california current system for the past 30 kyr and its paleoceanographic significance a north south transect of 17 cores was constructed along the eastern boundary of the california current system from 33 to 42 n to investigate the changes in biogenic sedimentation over the past 30 kyr percentages and mass accumulation rates of caco3 corg and biogenic opal were assembled at 500 to 1000 years sample to provide relatively high resolution time space maps reveal a complex pattern of changes that do not follow a simple glacial interglacial two mode model biogenic sedimentation shows responses that are sometimes time transgressive and sometimes coeval and most of the responses show more consistency within a limited geographic area than any temporal consistency reconstructed conditions during late oxygen isotope stage 3 were more like early holocene conditions than any other time during the last 30 kyr coastal upwelling and productivity during oxygen isotope stage 3 were relatively strong along the central california margin but were weak along the northern california margin precipitation increased during the last glacial interval in the central california region and the waters of the southern california margin had relatively low productivity productivity on the southern oregon margin was relatively low at the beginning of the last glacial interval but by about 20 ka productivity in this area significantly increased this change suggests that the center of the divergence of the west wind drift shifted south at this time the end of the last glacial interval was characterized by increased productivity in the southern california margin and increased upwelling along the central california margin but upwelling remained weak along the northern california margin a sudden 300 years decrease in caco3 corg and biogenic opal occurred at 13 ka the changes suggest a major reorientation of the atmospheric circulation in the north pacific and western north america and the establishment of a strong seasonality in the central california region a carbonate preservation event occurred at 10 ka that appears to reflect the uptake of co2 by the terrestrial biosphere as the northern latitudes were reforested following retreat of the glaciers the holocene has been a period of relatively high productivity in the southern california margin relatively strong coastal upwelling along the central california margin relatively weak upwelling along the northern california margin and the northward migration of the divergence zone of the west wind drift

high resolution climatic evolution of coastal northern california during the past 16 000 years holocene and latest pleistocene oceanographic conditions and the coastal climate of northern california have varied greatly based upon high resolution studies ca every 100 years of diatoms alkenones pollen caco 3 and total organic carbon at ocean drilling program odp site 1019 41 682 n 124 930 w 980 m water depth marine climate proxies alkenone sea surface temperatures ssts and caco 3 behaved remarkably like the greenland ice sheet project gisp 2 oxygen isotope record during the balling allerod younger dryas yd and early part of the holocene during the yd alkenone ssts decreased by 3 c below mean bolling allerod and holocene ssts the early holocene ca 11 6 to 8 2 ka was a time of generally warm conditions and moderate caco 3 content generally 4 the middle part of the holocene ca 8 2 to 3 2 ka was marked by alkenone ssts that were consistently 1 2 c cooler than either the earlier or later parts of the holocene by greatly reduced numbers of the gyre diatom pseudoeunotia doliolus 10 and by a permanent drop in caco 3 to 3 starting at ca 5 2 ka coastal redwood and alder began a steady rise arguing for increasing effective moisture and the development of the north coast temperate rain forest at ca 3 2 ka a permanent ca 1 c increase in alkenone sst and a threefold increase in p doliolus signaled a warming of fall and winter ssts intensified higher amplitude and more frequent cycles of pine pollen alternating with increased alder and redwood pollen are evidence that rapid changes in effective moisture and seasonal temperature enhanced el nino southern oscillation enso cycles have characterized the site 1019 record since about 3 5 ka

mass spectrometric 230th 234u 238u dating of the devils hole calcite vein the devils hole calcite vein contains a long term climatic record but requires accurate chronologic control for its interpretation mass spectrometric u series ages for samples from core dh 11 yielded 230 th ages with precisions ranging from less than 1 000 years 2 for samples younger than 140 ka thousands of years ago to less than 50 000 years for the oldest samples 566 ka the 234 u 238 u ages could be determined to a precision of 20 000 years for all ages calcite accumulated continuously from 566 ka until 60 ka at an average rate of 0 7 millimeter per 10 3 years the precise agreement between replicte analyses and the concordance of the 230 th 238 u 234 u 238 u ages for the oldest samples indicate that the dh 11 samples were closed systems and validate the dating technique in general

geochemical variations in peoria loess of western iowa indicate paleowinds of midcontinental north america during last glaciation peoria loess deposited in western iowa during the last glacial maximum lgm shows distinct geochemical and particle size variations as a function of both depth and distance east of the missouri river geochemical and particle size data indicate that peoria loess in western iowa probably had two sources the missouri river valley and a source that lay to the west of the missouri river both sources indicate that lgm paleowinds in western iowa had a strong westerly component similar to interpretations of previous workers a compilation of loess studies in iowa and elsewhere indicates that westerly winds were dominant during loess transport over much of the midcontinent south of the laurentide ice sheet which is not in agreement with paleowinds simulated by atmospheric general circulation models agcms agcms consistently generate a glacial anticyclone with easterly or northeasterly winds over the laurentide ice sheet and the area to the south of it loess deposition in the midcontinent during the lgm may be a function of infrequent northwesterly winds that were unrelated to the presence of the glacial anticyclone

two 30 000 year high resolution greyvalue time series from the santa barbara basin and the guaymas basin this paper is included in the special publication entitled geological evolution of ocean basins results from the ocean drilling program edited by a cramp c j macleod s v lee and e j w jones two 30 000 year records of sedimentary greyvalues from the santa barbara basin and the guaymas basin are presented the records exhibit substantial variability on all timescales from millennial to annual strong shifts towards darker greyvalues parallel the postglacial sea level rise approximately 1500 year cycles occur persistently in both records spectral analyses proved the existence of gleissberg 86 year sunspot 11 year 22 year and el nino 3 9 year cycles in almost all cores from both sites in particular el nino southern oscillation forcing could be traced back until the end of the last glacial cold period both time series show a high degree of similarity both in the time and the frequency domain indicating equivalent system responses to external forcing events

a 250 000 year climatic record from great basin vein calcite implications for milankovitch theory a continuous record of oxygen 18 18o variations in the continental hydrosphere during the middle to late pleistocene has been obtained from a uranium series dated calcitic vein in the southern great basin the vein was deposited from ground water that moved through devils hole an open fault zone at ash meadows nevada between 50 and 310 ka thousand years ago the configuration of the 18o versus time curve closely resembles the marine and antarctic ice core vostok 18o curves however the u th dates indicate that the last interglacial stage marine oxygen isotope stage 5 began before 147 3 ka at least 17 000 years earlier than indicated by the marine 18o record and 7 000 years earlier than indicated by the less well dated antarctic 18o record this discrepancy and other differences in the timing of key climatic events suggest that the indirectly dated marine 18o chronology may need revision and that orbital forcing may not be the principal cause of the pleistocene ice ages

orbital scale anti phase variation of sea surface temperature in mid latitude north pacific margins during the last 145 000 years 1 the late quaternary records of alkenone sea surface temperature sst in the japan and california margins showed orbital scale anti phase sst variations between the two margins this east west seesaw like change agreed well with the long term el nino southern oscillation enso behavior predicted by the zebiak cane enso model clement et al 1999 as regards both the timing and frequency during 0 60 ka and 120 145 ka and is attributed to the precession controlled change in tropical enso behavior this anti phase sst change was not clearly demonstrated during 60 120 ka this finding suggests that the influence of tropical climatic dynamics on the mid latitude north pacific varied in response to glacial interglacial cycles

tectonic speleogenesis of devils hole nevada and implications for hydrogeology and the development of long continuous paleoenvironmental records devils hole in southern nevada is a surface collapse into a deep planar steeply dipping fault controlled fissure in cambrian limestone and dolostone the collapse intersects the water table about 15 m below land surface and the fissure extends at least 130 m deeper below water most of the fissure is lined with a 30 cm thick layer of dense maxillary calcite that precipitated continuously from groundwater for 500 000 yr the thick mammillary calcite coat implies a long history of calcite supersaturated groundwaters which combined with the absence of dissolutional morphologies suggests that devils hole was not formed by karst processes devils hole is located in a region of active extension its tectonic origin is shown by evidence of spreading of its planar opening along a fault and by the orientation of its opening and others nearby perpendicular to the northwest southeast minimum principal stress direction of the region most quaternary tectonic activity in the area including seismicity and quaternary faults and fractures occurs on or parallel to northeast striking structures the hydrogeologic implications of this primarily structural origin are that fracture networks and caves opened by extensional tectonism can act as groundwater flowpaths functionally similar to those developed by karst processes and that during active extension transmissivity can be maintained despite infilling by mineral precipitation such extensional environments can provide conditions favorable for accumulation of deposits preserving long continuous paleoenvironmental records the precipitates in devils hole store chronologies of flow system water level fluctuations hydrochemistry a half million yr proxy paleoclimate record evidence of devils hole s tectonic origin and probably atmospheric circulation

paleomagnetism of early jurassic rocks watchung mountains newark basin evidence for complex rotations along the border fault a paleomagnetic study of late triassic to early jurassic rocks from the watchung syncline provides useful new constraints on the complex development of the newark basin independent of existing structural data a baked contact test indicates stable remanent magnetizations are primary results from the eastern limb of the fold are used to calculate an early jurassic pole at long 115 1 e lat 62 2 n alpha 95 10 5 k 41 4 which is similar to previous newark basin results after results from the western limb were corrected for folding 32 of clockwise discordance remained between data from the western and eastern limbs this cryptic rotation of newark basin strata appears to be localized to the border fault zone and may be due to the presence of left lateral secondary brittle shear zones running parallel to strata of the western limb of the watchung syncline

evolution of marine terraces and sea level in the last interglacial cave hill barbados the uplifted marine terrace of last interglacial stage 5e age at cave hill barbados has been investigated with views toward terrace architecture developmental processes and sea level history methods include stratigraphic analysis of new deep exposures precise 230th geochronology and geomorphic mapping cave hill was central to earlier studies that led to important ideas on reef and terrace evolution but with which we find significant disagreement we present a new model of terrace evolution that emphasizes the role of marine erosion deposition of carbonate cover during the full eustatic cycle rather than only at highstand and principal reef development during transgression rather than at highstand by keep up rather than catch up growth the new model and geochronology contribute to an improved understanding of surficial processes during emergence of uplifting coral coasts and of global sea level changes in the last interglacial transgression in stage 5e at cave hill was accompanied by progressive marine erosion of a terrace floor and receding seacliff and deposition of a seaward thickening reefal wedge on the floor and above limestones of stage 6 and 7 ages the wedge contains a diachronous basal acropora palmata fringe reef this is overlain by an in place a cervicornis reef that aggraded progressively during sea level rise the transgressive phase took place between 136 ka or earlier and ca 128 ka during highstand between ca 127 and 120 ka the floor and seacliff continued to recede landward re gression began at or after ca 120 ka and sea level fell 37 m below the highstand level by ca 115 ka in stage 5c the seaward front of the last interglacial terrace was eroded landward an uncertain distance the sea level record at cave hill has implications for timing and constituent events of the penultimate glacial the last interglacial highstand and the fall in sea level at the transition from stage 5e to stage 5d shoreline angles which are isochronous linear geomorphic features are the most accurate markers of sustained highstand levels highstand levels and uplift rates interpreted from a palmata in barbados are less accurate and lower because the coral grew mainly in transgression the coral derived data therefore include uncertainties of depths of growth and collapse

protactinium 231 dating of carbonates by thermal ionization mass spectrometry implications for quaternary climate change measurement of protactinium 231 231pa in carbonates by thermal ionization mass spectroscopy yields 231pa ages that are more than 10 times more precise than those determined by decay counting carbonates between 10 and 250 000 years old can now be dated with 231pa methods barbados corals that have identical 231pa and thorium 230 230th ages indicate that the timing of sea level change over parts of the last glacial cycle is consistent with the predictions of the astronomical theory two devils hole calcite subsamples record identical 231pa and 230th ages suggesting that the chronology of this climate record is accurate

simulation of the climate of 18 000 years bp results for the north american north atlantic european sector and comparison with the geologic record of north america abstract the large ice sheets in north america and europe and the extensive sea ice cover in the north atlantic at the time of the last glacial maximum must have greatly modified the surface temperature patterns and in turn the location and intensity of the surface winds and jet streams a general circulation model was used to simulate the january and july patterns of temperature precipitation and wind for 18 ka bp boundary conditions for the model consisting of ice sheet location and height sea ice location and sea surface temperature were prescribed from climap 1981 the model results are illustrated and described for the north american north atlantic european sector the jet stream splits around the north american ice sheet and the southern branch strengthens considerably compared to present over the southern portion of the united states the sea ice margin of the north atlantic and the southern edge of the european ice sheet geologic evidence principally from north america of wind temperature and moisture conditions is assessed from sand dune and loess records estimates of snowline depression pollen records and lake level studies the geologic evidence is generally compatible with the model simulation

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

coastal upwelling in the california current system abstract coastal upwelling in the california current system has been the subject of large scale studies off california and baja california and of small scale studies off oregon recent studies of the winds along the entire coast from 25 n to 50 n indicate that there are significant along shore variations in the strength of coastal upwelling which are reflected in the observed temperature distribution active upwelling appears to be restricted to a narrow coastal band about 10 25 km wide along the entire coast but the region influenced by coastal upwelling may be much wider intensive observations of the upwelling zone during summer off oregon show the presence of a southward coastal jet at the surface a mean vertical shear a poleward undercurrent along the bottom and persistently sloping isopycnals over the continental shelf most of the upwelling there occurs during relatively short periods several days long of upwelling favorable winds during the upwelling season off oregon the offshore ekman transport is carried by the surface ekman layer and the onshore return flow occurs through a quasi geostrophic interior it is not known whether the structure and dynamics observed off oregon are typical of the upwelling zone along the entire coast though some of the same features have been observed off baja california current and future research will eventually show whether the oregon results are also applicable in the region of persistently strong upwelling favorable winds off northern california and in the region of complex bathymetry off central and southern california

dansgaard oeschger cycles and the california current system planktonic foraminiferal response to rapid climate change in santa barbara basin ocean drilling program hole 893a high resolution planktonic foraminiferal census data from santa barbara basin ocean drilling program hole 893a demonstrate major assemblage switches between 25 and 60 ka that were associated with dansgaard oeschger cycles stadials dominated by neogloboquadrina pachyderma sinistral and globigerinoides glutinata suggest a strong subpolar california current influence while interstadials marked by abundant n pachyderma dextral and g bulloides indicate a relative increase in subtropical countercurrent influence modern analog technique and transfer function f 20rsc temperature reconstructions support 18o evidence of large rapid 70 years or less sea surface temperature shifts 3 to 5 c between stadials and interstadials changes in the vertical temperature gradient and water column structure thermocline depth are recorded by planktonic faunal oscillations suggest bimodal stability in the organization of north pacific surface ocean circulation santa barbara basin surface water demonstrates the rapid response of the california current system to reorganization of north pacific atmospheric circulation during rapid climate change supporting assemblage data are available on diskette or via anonymous ftp from kosmos agu org directory apend username anonymous password guest diskette may be ordered from american geophysical union 2000 florida avenue n w washington dc 20009 or by phone at 800 966 2481 5 00 payment must accompany order

milankovitch theory viewed from devils hole variations in the oxygen isotope content 18o of late quaternary deep sea sediments mainly reflect changes in continental ice mass1 and hence provide important information about the timing of past ice ages because these sediments cannot yet be dated directly beyond the range of radiocarbon dating 40 50 kyr ages for the 18o record have been generated2 3 by matching the phase of the changes in 18o to that of variations in the earth s precession and obliquity adopting this timescale yields a close correspondence between the time varying amplitudes of these orbital variations and those of a wide range of climate proxies4 lending support to the milankovitch theory that the earth s glacial interglacial cycles are driven by orbital variations recently winograd et al 5 reported a record of 18o variations in a fresh water carbonate sequence from devils hole nevada dated by u th disequilibrium6 they concluded that the timing of several of the features in the record which reflects changes in the temperature of precipitation over nevada as well as changes in the isotopic composition of the moisture source5 7 showed significant deviations from that predicted by milanko vitch theory here we demonstrate that applying the devils hole chronology to ocean cores requires physically implausible changes in sedimentation rate moreover spectral analysis of the devils hole record shows clear evidence of orbital influence we therefore conclude that transfer of the devils hole chronology to the marine record is inappropriate and that the evidence in favour of milankovitch theory remains strong

duration and structure of the past four interglaciations reanalysis and additional dating of the devils hole 18o paleotemperature record confirm that the last interglaciation in the great basin the continental analog of marine isotopic substage 5e lasted 22 000 yr consistent with the vostok paleotemperature record which suggests a duration of 19 000 yr for this event in antarctica the three preceding interglaciations in the devils hole record analogs of marine isotopic substages 7e 9c and 11c range from 20 000 to 26 000 yr in duration a 20 000 yr duration for the last interglaciation is consistent with tims uranium series dated sea level high stands thus the widely held view that interglaciations were of 11 000 to 13 000 yr duration and constituted only about 10 of mid to late pleistocene climatic cycles needs reexamination the warmest portion of each interglaciation in the devils hole time series is marked by a 18o plateau signifying apparent climatic stability for periods of 10 000 to 15 000 yr duration

the last interglacial ocean the final effort of the climap project was a study of the last interglaciation a time of minimum ice volume some 122 000 yr ago coincident with the substage 5e oxygen isotopic minimum based on detailed oxygen isotope analyses and biotic census counts in 52 cores across the world ocean last interglacial sea surface temperatures sst were compared with those today there are small sst departures in the mid latitude north atlantic warmer and the gulf of mexico cooler the eastern boundary currents of the south atlantic and pacific oceans are marked by large sst anomalies in individual cores but their interpretations are precluded by no analog problems and by discordancies among estimates from different biotic groups in general the last interglacial ocean was not significantly different from the modern ocean the relative sequencing of ice decay versus oceanic warming on the stage 6 5 oxygen isotopic transition and of ice growth versus oceanic cooling on the stage 5e 5d transition was also studied in most of the southern hemisphere the oceanic response marked by the biotic census counts preceded led the global ice volume response marked by the oxygen isotope signal by several thousand years the reverse pattern is evident in the north atlantic ocean and the gulf of mexico where the oceanic response lagged that of global ice volume by several thousand years as a result the very warm temperatures associated with the last interglaciation were regionally diachronous by several thousand years these regional lead lag relationships agree with those observed on other transitions and in long term phase relationships they cannot be explained simply as artifacts of bioturbational translations of the original signals

low latitude ice cores record pacific sea surface temperatures matic records suggested that a more conventional temperature interpretation might be more appropriate with lower isotopic values during the presumed to be cooler little ice age and increasingly enriched precipitation during the 20th century warming phase thompson 2001 3 both of these conflicting interpretations suffer from inadequate calibration of the observed isotopic record in relation to climatic conditions during periods of snow accumulation on the ice caps here we use the results of on site meteorological measurements to determine the seasonality of the ice core record and then assess how the isotopic records relate to temperature precipitation and the larger scale circulation associated with snowfall at these high elevation sites we then extend the analysis to ice core records from the asian monsoon region this empirical approach to the interpretation of the isotopic record in low latitude ice cores complements theoretical studies by broecker 1997 and pierrehumbert 1999

constructing a stacked benthic δ18o record composite stacks were constructed by superimposing 6 to 13 benthic foraminiferal 1 8 o records covering the period 0 850 ka an initial timescale for each core was established using radioisotopic age control points and assuming constant sedimentation rates between these points the average of these records is our 13 core untuned stack next we matched the 41 kyr component of each record individually to variations in earth s obliquity four of the 13 records produced timescales that were inconsistent with one or more of the known radioisotopic ages the nine remaining cores were averaged to create a minimally tuned stack six of the minimally tuned cores were assembled into a tropical stack for each stack we estimated the uncertainty envelope from the standard deviation of the constituents spectral analysis of the three stacks indicates that benthic 1 8 o is dominated by a 100 kyr oscillation that has a narrow spectral peak the contribution of precession to the total variance is small when compared to prior results from planktic stacks

climate impact of late quaternary equatorial pacific sea surface temperature variations magnesium calcium data from planktonic foraminifera in equatorial pacific sediment cores demonstrate that tropical pacific sea surface temperatures ssts were 2 8 0 7 c colder than the present at the last glacial maximum glacial interglacial temperature differences as great as 5 c are observed over the last 450 thousand years changes in sst coincide with changes in antarctic air temperature and precede changes in continental ice volume by about 3 thousand years suggesting that tropical cooling played a major role in driving ice age climate comparison of sst estimates from eastern and western sites indicates that the equatorial pacific zonal sst gradient was similar or somewhat larger during glacial episodes extraction of a salinity proxy from the magnesium calcium and oxygen isotope data indicates that transport of water vapor into the western pacific was enhanced during glacial episodes

a speleothem record of younger dryas cooling klamath mountains oregon usa awell dated d 18 o record in a stalagmite from a cave in the klamath mountains oregon with a sampling interval of 50 yr indicates that the climate of this region cooled essentially synchronously with younger dryas climate change elsewhere in the northern hemisphere the d 18 o record also indicates significant century scale temperature variability during the early holocene the d 13 c record suggests increasing biomass over the cave through the last deglaciation with century scale variability but with little detectable response of vegetation to younger dryas cooling d 2005 university of washington all rights reserved

timing and duration of the last interglacial evidence for a restricted interval of widespread coral reef growth abstract we report new mass spectrometric u series ages for eight last interglacial fossil reefs along the continental margin of western australia corals were selected in growth position from localities that are characterized by apparently low levels of diagenesis and relative tectonic stability so that the fossil reefs provide critical information on last interglacial sea levels without requiring corrections for tectonic movements in addition we have improved the constraint on the timing of onset of reef growth by recovering drill core coral from the base of the reefs uranium and thorium isotopes were measured with high levels of precision leading to improvements in age resolution and allowing samples which have undergone diagenetic exchange of uranium and thorium to be more easily identified and discarded these data supplement our previous results for rottnest island and leander point leading to more than seventy mass spectrometric u series ages from which constraints can be placed on the timing duration and character of the last interglacial sea level highstand reliable ages show that reef growth started contemporaneously at 128 1 ka along the entire western australian coastline while relative sea levels were at least 3 m above the present level because western australia is located far from the former penultimate glacial maximum ice sheets and are not significantly effected by glacial unloading these data constrain the timing of onset of the last interglacial period to 128 1 ka assuming reef growth started soon after sea level approached interglacial levels a unique regressive reef sequence at mangrove bay constrains the timing of termination of the last interglacial period to 116 1 ka the major episode of reef building however both globally and locally along the western australian coast is restricted to a very narrow interval occurring from 128 ka and 121 ka suggesting that global ocean surface temperatures were warm and or sea levels were stable enough to allow prolific reef growth only during the earlier part of the last interglacial

sea surface temperature changes in the northeastern pacific ocean during the past 20 000 years and their relationship to climate change in northwestern north america abstract modern ocean atmosphere interactions in the northeastern pacific ocean have a significant effect on the climate of the west coast of north america we present radiolarian microfossil based temperature reconstructions for the eastern north pacific spanning the past 20 000 yr to examine possible correlations and linkages between continental climate change and changes in sea surface temperature sst in the northeastern pacific ocean on millennial time scales the reconstructions indicate that the regional pattern of ocean circulation off the west coast of north america was further south 15 000 cal yr b p than it is today and reached its present location 13 000 cal yr b p the north pacific drift and transition zone were further south as a result of a more southerly north pacific high pressure cell prior to 13 000 cal yr b p while two continental paleoclimate records from northwestern north america show regional differences they also can be correlated to the sst changes a coastal site at 48 n shows similar patterns in summer temperatures as observed in offshore marine records of ssts however an inland continental record seems to reflect more regional scale changes in sea surface conditions showing a thermal maximum centered at 10 000 cal yr b p which is observed in the marine transect south of 42 n we conclude based on the pattern of oceanographic change as reflected in radiolarian assemblages that changes in the past latitudinal position of the north pacific drift played a significant role in controlling continental climate immediately to its east as it does in the present environment we also conclude that during the past 20 000 yr much of the evolution of oceanographic change is related to the migration of the atmospheric pressure cells the north pacific high and aleutian low of the northeastern pacific

glacial interglacial variability in upwelling and bioproductivity off nw mexico implications for quaternary paleoclimate sedimentary accumulation of biogenic components organic carbon opal and biogenic barium on the northwestern mexican margin declined during every glacial interval of the past 140 kyr indicating decreases in upwelling induced productivity during cold periods the glacial interglacial contrasts in upwelling on this margin are attributed to reversals in land ocean thermal contrast the waxing and waning of the laurentide ice sheet and consequent responses of the western hemisphere wind fields this scenario is consistent with three independent lines of evidence terrestrial paleoclimatic data general circulation model results and our marine records this pattern of glacial interglacial variability in upwelling off nw mexico is opposite to that observed in other low latitude and midlatitude upwelling areas such as the eastern equatorial pacific these results add to a growing pool of observations that the response of oceanic upwelling to glacial climatic forcing has been regionally variable

the magnitude and proximate cause of ice sheet growth since 35 000 yr b p the magnitude of late wisconsinan post 35 000 yr b p ice sheet growth in the northern hemisphere is not well known ice volume at 35 000 yr b p may have been as little as 20 or as much as 70 of the volume present at the last glacial maximum lgm a conservative evaluation of glacial geologic sea level and benthic 18o data indicates that ice volume at 35 000 yr b p was approximately 50 of that extant at the lgm 20 000 yr b p that is it doubled in about 15 000 yr on the basis of literature for the north atlantic and a sea surface temperature sst data compilation it appears that this rapid growth may have been forced by low to mid latitude sst warming in both the atlantic and pacific oceans with attendant increased moisture transport to high latitudes the sst ice sheet growth notion also explains the apparent synchroneity of late wisconsinan mountain glaciation in both hemispheres

palaeo climate reconstruction from stable isotope variations in speleothems a review abstract speleothems are now regarded as valuable archives of climatic conditions on the continents offering a number of advantages relative to other continental climate proxy recorders such as lake sediments and peat cores they are ideal materials for precise u series dating yielding ages in calendar years thereby circumventing the radiocarbon calibration problems associated with most other continental records stable isotope studies in speleothems have shifted away from attempting to provide palaeo temperature reconstructions to the attainable goal of providing precise estimates for the timing and duration of major o isotope defined climatic events characterised by high signal to noise ratios e g glacial interglacial transitions dansgaard oeschger oscillations the 8200 year event unlike the marine records speleothem data sets are not tuned and their independent chronology offers opportunities to critically assess leads and lags in the climate system that in turn can provide important insights into forcing and feedback mechanisms improved procedures for the extraction and measurement of stable isotope ratios in fluid inclusions trapped in speleothems are likely to provide in the near future a much enhanced basis for the quantitative interpretation of o isotope ratios in speleothem calcite the latter developments open up once again the tantalising prospect of palaeo temperature estimates but more importantly perhaps provide a direct test for a new generation of general circulation models whose hydrological cycles will incorporate the water isotopes the literature is reviewed briefly to provide for the reader a sense of the current state of the art and to provide some pointers for future research directions

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

the british final magdalenian society settlement and raw material movements revealed through la icp ms trace element analysis of diagnostic artefacts abstract raw material movements and group mobility in the british final magdalenian is poorly understood following a review of the british final magdalenian creswellian this paper presents preliminary results of a major la icp ms trace elemental characterization of british bedrock flint regions and compare to these characterizations of artefacts from three assemblages from the first half of the late glacial interstadial the meiendorf classed as final magdalenian the results successfully distinguish between major bedrock flint regions and artefacts can be linked to these with confidence the results reveal the importance of east anglia the lincolnshire wolds and the salisbury plain as lithic sources for artefacts from farndon fields nottinghamshire bradgate park leicestershire and wey manor farm surrey to which some flints were transported over distances ranging from the local to 200 km the results are reviewed in the context of continental raw material movements

the california current of the last glacial maximum reconstruction at 42 n based on multiple proxies multiple paleoceanographic proxies in a zonal transect across the california current near 42 n record modern and last glacial maximum lgm thermal and nutrient gradients the offshore thermal gradient derived from foraminiferal species assemblages and oxygen isotope data was similar at the lgm to that at present warmer offshore but average temperatures were 3 3 1 5 c colder observed gradients require that the sites remained under the southward flow of the california current and thus that the polar front remained north of 42 n during the lgm carbon isotopic and foraminiferal flux data suggests enhanced nutrients and productivity of foraminfera in the northern california current up to 650 km offshore in contrast marine organic carbon and coastal diatom burial rates decreased during the lgm these seemingly contradictory results are reconciled by model simulations of the lgm wind field which suggest that wind stress curl at 42 n and thus open ocean upwelling increased while offshore ekman transport and thus coastal upwelling decreased during the last ice age the ecosystem of the northern california current during the lgm approximated that of the modern gulf of alaska cooling and production in this region was thus driven by stronger open ocean upwelling and or southward flow of high latitude water masses rather than by coastal upwelling

the correlation between 18o 16o ratios of meteoric water and surface temperature its use in investigating terrestrial climate change over geologic time abstract correlations between mean annual temperature mat and the weighted average oxygen isotope composition of yearly precipitation 18opt are well known but the utility of modern relations to make reliable estimates of temperature change over geological time is uncertain this question has been addressed by using seasonal subsets of the global data base of temperature and isotopic measurements to represent two different climate modes a comparison of middle to high latitude 18opt temperature relations for each climate mode reveals 1 a significant offset between them and 2 a difference in the strength of their correlations the offset in relations is due to differences in temperature and water vapor budget in the tropics and can lead to serious underestimates of temperature change differences in the strength of correlations arise from the influence of climate mode specific non temperature factors on 18opt the overall result is that no single relation can be used in all cases to make unambiguous temperature estimates using a temporal record of 18opt values one way to overcome these problems is to reconstruct 18opt temperature relations for the time periods being investigated if an appropriate proxy for 18opt is available it may also be possible to estimate temperature without relying on 18opt temperature relations a promising alternative to these options is to use records of 18opt to test predictions of global climate models an approach that may allow a reliable and more complete reconstruction to be made of climate change over geologic time

dating the vostok ice core record by importing the devils hole chronology the development of an accurate chronology for the vostok record continues to be an open research question because these invaluable ice cores cannot be dated directly depth to age relationships have been developed using many different approaches but published age estimates are inconsistent even for major paleoclimatic events we have developed a chronology for the vostok deuterium paleotemperature record using a simple and objective algorithm to transfer ages of major paleoclimatic events from the radiometrically dated 500 000 year 18o paleotemperature record from devils hole nevada the method is based only on a strong inference that major shifts in paleotemperature recorded at both locations occurred synchronously consistent with an atmospheric teleconnection the derived depth to age relationship conforms with the physics of ice compaction and internally produces ages for climatic events 5 4 and 11 24 which are consistent with the externally assigned ages that the vostok team needed to assume in order to derive their most recent chronology gt4 indeed the resulting v dh chronology is highly correlated with gt4 because of the unexpected correspondence even in the timing of second order climatic events that were not constrained by the algorithm furthermore the algorithm developed herein is not specific to this problem rather the procedure can be used whenever two paleoclimate records are proxies for the same physical phenomenon and paleoclimatic conditions forcing the two records can be considered to have occurred contemporaneously the ability of the algorithm to date the east antarctic dome fuji core is also demonstrated

second clock supports orbital pacing of the ice ages a new radioactive clock has settled a dispute that threatened the reigning theory of the ice ages which holds that they are paced by the cyclical stretching and squeezing of earth9s orbit around the sun an ice age chronology from ocean floor sediment and ancient corals supported the theory but minerals at a site called devils hole in nevada yielded a record not consistent with orbital timing as described on page 782 the new dating technique puts the orbital theory back on solid ground and implies that devils hole was recording only local climate

last interglacial sea stands on barbados and an early anomalous deglaciation timed by differential uplift three major sea level maxima between 137 and 120 kyr b p are documented by surveys of pairs of wave cut notches and other features associated with the broadly defined last interglacial coral terrace on barbados regression analysis of elevation differences between notch pair members as a function of their uplift rates at seven sites yields the age difference between first and third sea stands and their eustatic sea level difference these results when combined with stratigraphic data from the bahamas bermuda and western australia and a chronology based on age limits of corals from the bahamas and western australia yield an endpoint age and eustatic low tide elevation of 136 7 kyr b p and 7 4 m respectively for the first sea stand 126 kyr b p and 5 6 m for the second and 120 5 kyr b p and 3 0 m for the third the first sea stand is the result of an anomalous deglaciation that was completed during low northern summer milankovitch insolation this is contrary to the milankovitch hypothesis that orbitally controlled insolation largely determines the variations of glacial ice volume it implies that internal factors within the earth s climate system can be much stronger than the effects of insolation variations

paleoproductivity and carbon burial across the california current the multitracers transect 42 n the multitracers experiment studied a transect of water column sediment trap and sediment data taken across the california current to develop quantitative methods for hindcasting paleoproductivity the experiment used three sediment trap moorings located 120 km 270 km and 630 km from shore at the oregon california border in north america we report here about the sedimentation and burial of particulate organic carbon corg and caco3 in order to observe how the integrated caco3 and corg burial across the transect has changed since the last glacial maximum we have correlated core from the three sites using time scales constrained by both radiocarbon and oxygen isotopes by comparing surface sediments to a two and a half year sediment trap record we have also defined the modern preservation rates for many of the labile sedimentary materials our analysis of the corg data indicates that significant amounts 20 40 of the total corg being buried today in surface sediments is terrestrial at the last glacial maximum the terrestrial corg fraction within 300 km of the coast was about twice as large such large fluxes of terrestrial corg obscure the marine corg record which can be interpreted as productivity when we corrected for the terrestrial organic matter we found that the mass accumulation rate of marine corg roughly doubled from the glacial maximum to the present because preservation rates of organic carbon are high in the high sedimentation rate cores corrections for degradation are straightforward and we can be confident that organic carbon rain rate new productivity also doubled as confirmation the highest burial fluxes of other biogenic components opal and ba also occur in the holocene productivity off oregon has thus increased dramatically since the last glacial maximum caco3 fluxes also changed radically through the deglaciation however they are linked not to caco3 production but rather to changes in deepwater carbonate chemistry between 18 ka and now

glacial climate instability in the northeast pacific ocean recent climate records from greenland ice cores1 2 and north atlantic sediments3a 5 have challenged the long held notion that pleistocene climate fluctuates between two relatively stable states glacials and interglacials it has been appreciated for some time that the transitions from one state to another are not smooth6 but the new records indicate that the glacial and interglacial periods themselves appear to be punctuated by significant climate variability several short interstadial events punctuated the last glacial period for example but it has not been clear whether this climate instability is a global phenomenon or is peculiar to the north atlantic region here we present climate proxy records from sediment cores from the eastern margin of the north pacific ocean which indicate that climate in this region was also highly unstable during the last glaciation our observations suggest that glacial climate instability throughout the northern hemisphere might be linked to rapid changes in the size of the laurentide ice sheet and associated changes in atmospheric circulation

climatic and oceanographic variations on the california continental margin during the last 160 kyr organic matter in sediment samples from three odp sites ocean drilling program leg 167 that form a south north transect was investigated to reconstruct the paleoclimatic and oceanographic conditions on the california continental margin during the last 160 kyr alkenone derived paleosea surface temperatures sst are 3 to 6 c colder in glacial stages and reveal a clear relationship with global climate changes the differences are greater in the north latitudinal sst comparison exhibits water mixing of the colder california current with warmer waters from the south particularly in the southern central california borderland area organic matter accumulation on the california continental margin indicates an interplay between climatic and atmospheric glacial interglacial variations and spatially and temporally changing nutrient availability along the california coastline climatic and atmospheric dependent circulations apparently caused variations in the intensity of coastal upwelling along the southern central california margin and this suggests due to the close connection of the california current to the local wind patterns that the california current was weaker during glacial and stronger during interglacial periods

stable isotope composition of waters in the great basin united states 1 air mass trajectories 1 isentropic trajectories calculated using the noaa climate monitoring and diagnostics laboratory s isentropic transport model were used to determine air parcel origins and the influence of air mass trajectories on the isotopic composition of precipitation events that occurred between october 1991 and september 1993 at cedar city utah and winnemucca nevada examination of trajectories that trace the position of air parcels backward in time for 10 days indicated five distinct regions of water vapor origin 1 gulf of alaska and north pacific 2 central pacific 3 tropical pacific 4 gulf of mexico and 5 continental land mass deuterium d and oxygen 18 18o analyses were made of precipitation representing 99 of all cedar city events similar analyses were made on precipitation representing 66 of the precipitation falling at winnemucca during the same period the average isotopic composition of precipitation derived from each water vapor source was determined more than half of the precipitation that fell at both sites during the study period originated in the tropical pacific and traveled northeast to the great basin only a small proportion traversed the sierra nevada the isotopic composition of precipitation is determined by air mass origin and its track to the collection station mechanism of droplet formation reequilibration within clouds and evaporation during its passage from cloud to ground the rayleigh distillation model can explain the changes in isotopic composition of precipitation as an air mass is cooled pseudo adiabatically during uplift however the complicated processes that take place in the rapidly convecting environment of cumulonimbus and other clouds that are common in the great basin especially in summer require modification of this model because raindrops that form in the lower portion of those clouds undergo isotopic change as they are elevated to upper levels of the clouds from where they eventually drop to the ground

glacial anticyclone recorded in palouse loess of northwestern united states climate simulations for the last glacial maximum using general circulation models typically show a glacial anticyclone that produced an easterly wind anomaly south of the north american ice sheets evidence of this phenomenon has not been found in eolian sedimentary deposits that record surface wind patterns luminescence ages of loess and accompanying paleoecologic records from opal phytoliths and paleosol units across the columbia plateau washington state united states document a decrease up to fivefold in regional dust production and accumulation from 35 ka to 15 ka this interval corresponds to simulations indicating that a glacial anticyclone weakened prevailing south southwesterly winds that have shaped the eolian landscape of the columbia plateau since at least 75 ka at the same time that the glacial anticyclone suppressed dust production and accumulation enhanced cold and dry conditions resulted in soil formation dominated by intense bioturbation in periglacial steppe accompanied by shallow calcium carbonate precipitation this is the first evidence from eolian deposits in north america verifying that the glacial anticyclone altered surface wind patterns and affected eolian systems during the last glacial maximum

variable responses of western u s glaciers during the last deglaciation cosmogenic 10 be exposure ages from moraines in the wallowa mountains oregon identify two maximal late pleistocene glaciations at 21 1 6 0 4 ka and 17 0 6 0 3 ka and a minor glacial event at 10 2 6 0 6 ka our new high resolution chronology integrated with other well dated glacial records from the western united states demonstrates sub stantial differences in the synoptic responses of western u s glaciers to climate forcing associated with the global last glacial maximum and subsequent millennial scale events originating in the north atlantic region these variable synoptic glacier responses identify large changes in the relative contributions of regional to global controls on the climate of the western united states that accompanied the deglaciation

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