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We present a high-resolution magnesium/calcium proxy record of Holocene sea surface temperature (SST) from off the west coast of Baja California Sur, Mexico, a region where interannual SST variability is dominated today by the influence of the El Nino--Southern Oscillation (ENSO). Temperatures were lowest during the early to middle Holocene, consistent with documented eastern equatorial Pacific cooling and numerical mode[ simulations of orbital forcing into a La Nina--like state at that time. The early Holocene SSTs were also characterized by millennial-scale fluctuations that correlate with cosmogenic nuclide proxies of solar variability, with inferred solar minima corresponding to El Nino--like (warm) conditions, in apparent agreement with the theoretical 'ocean dynamical thermostat' response of ENSO to exogenous radiative forcing. 10.1126/science.1194887

Understanding the timings of interhemispheric climate changes during the Holocene, along with their causes, remains a major problem of climate science. Here, we present a high-resolution [sup.10]Be chronology of glacier fluctuations in New Zealand's Southern Alps over the past 7000 years, including at least tire events during the last millennium. The extents of glacier advances decreased from the middle to the late Holocene, in contrast with the Northern Hemisphere pattern. Several glacier advances occurred in New Zealand during classic northern warm periods. These findings point to the importance of regional driving and/or amplifying mechanisms. We suggest that atmospheric circulation changes in the southwest Pacific were one important factor in forcing high-frequency Holocene glacier fluctuations in New Zealand.

Paleosalinity and terrigenous sediment input changes reconstructed on two sediment cores from the northernmost Red Sea were used to infer hydrological changes at the southern margin of the Mediterranean climate zone during the Holocene. Between approximately 9.25 and 7.25 thousand years ago, about 3 ‰ reduced surface water salinities and enhanced fluvial sediment input suggest substantially higher rainfall and freshwater runoff, which thereafter decreased to modern values. The northern Red Sea humid interval is best explained by enhancement and southward extension of rainfall from Mediterranean sources, possibly involving strengthened early-Holocene Arctic Oscillation patterns and a regional monsoon-type circulation induced by increased land-sea temperature contrasts. We conclude that Afro-Asian monsoonal rains did not cross the subtropical desert zone during the early to mid-Holocene., Though from a long-term perspective, the Holocene is commonly seen as a relative stable climatic period, the tropics and sub tropics and also the Mediterranean climate zone were subject to [...]

Sea surface temperatures (SSTs) in the cold tongue of the eastern equatorial Pacific exert powerful controls on global atmospheric circulation patterns. We examined climate variability in this region from the Last Glacial Maximum (LGM) to the present, using a SST record reconstructed from magnesium/calcium ratios in foraminifera from sea-floor sediments near the Galapagos islands. Cold-tongue SST varied coherently with precession-induced changes in seasonality during the past 30,000 years. Observed LGM cooling of just 1.2°C implies a relaxation of tropical temperature gradients, weakened Hadley and Walker circulation, southward shift of the Intertropical Convergence Zone, and a persistent El Nino--like pattern in the tropical Pacific. This is contrasted with mid-Holocene cooling suggestive of a La Nina-like pattern with enhanced SST gradients and strengthened trade winds. Our results support a potent role for altered tropical Pacific SST gradients in global climate variations., Studies of El Nino-Southern Oscillation (ENSO) dynamics and impacts demonstrate that the tropical Pacific ocean-atmosphere system influences global climate on interannual to decadal time scales (1). Models suggest that this [...]

Abrupt first-order shifts in strontium and phosphorus concentrations in stalagmite calcite deposited in western Ireland during the 8200-year event (the major cooling episode 8200 years before the present) are interpreted as responses to a drier climate lasting about 37 years. Both shifts are centered on 8330 ± 80 years before the present, coinciding with a large oxygen isotope anomaly and a change in the calcite petrography. In this very high resolution (monthly) record, antipathetic second-order oscillations in phosphorus and strontium reveal decreased growth rates and increased rainfall seasonality. Growth rate variations within the event reveal a two-pronged structure consistent with recent model simulations., The 8200-year event is widely regarded as the strongest Holocene cooling episode, with clear expressions in Greenland (1, 2), the North Atlantic (3), Europe (4-11), North America (12-14), North Africa [...]

Surface winds and surface ocean hydrography in the subpolar North Atlantic appear to have been influenced by variations in solar output through the entire Holocene. The evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon-14 and beryllium-10 and centennial to millennial time scale changes in proxies of drift ice measured in deep-sea sediment cores. A solar forcing mechanism therefore may underlie at least the Holocene segment of the North Atlantic's 1500-year' cycle. The surface hydrographic changes may have affected production of North Atlantic Deep Water, potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally., A prominent feature of the North Atlantic's Holocene climate is a series of shifts in ocean surface hydrography during which drift ice and cooler surface waters in the Nordic and [...]

Evaluating the significance of Holocene submillennial [δ.sup.18]O variability in the Greenland ice cores is crucial for understanding how natural climate oscillations may modulate future anthropogenic warming. A high-resolution oxygen isotope record from a speleothem in southwestern Ireland provides evidence for centennial-scale [δ.sup.18]O variations that correlate with subtle [δ.sup.18]O changes in the Greenland ice cores, indicating regionally coherent variability in the early Holocene. Evidence for previously undetected early Holocene cooling events is presented, but mid- to late-Holocene ice rafting in the North Atlantic appears to have had little impact on [δ.sup.18]O at this ocean margin site., It is widely accepted that climate variability on time scales of [10.sup.3] to [10.sup.5] years is driven primarily by orbital, or so-called Milankovitch, forcing. Less well understood is the cause [...]

Skeletal Sr/Ca and [sup.18] O/[sup.16] O ratios in corals from the Great Barrier Reef, Australia, indicate that the tropical ocean surface ~5350 years ago was 1 ° C warmer and enriched in [sup.18] O by 0.5 per mil relative to modern seawater. The results suggest that the temperature increase enhanced the evaporative enrichment of [sup.18] O in seawater. Transport of part of the additional atmospheric water vapor to extratropical latitudes may have sustained the [sup.18] O/[sup.16] O anomaly. The reduced glacial-Holocene shift in seawater [sup.18] O/[sup.16] O ratio produced by the mid-Holocene [sup.18] O enrichment may help to reconcile the different temperature histories for the last deglaciation given by coral Sr/Ca thermometry and foraminiferal oxygen-isotope records., Oxygen isotopes in foraminifera from deep-sea cores have been used successfully to reconstruct continental ice volumes, glacio-eustatic sea level, and deep-ocean temperatures throughout the last glacial-interglacial cycle (1). Yet there [...]

Ice cores from Penny Ice Cap, Baffin Island, Canada, provide continuous Holocene records of oxygen isotopic composition ([Delta.sup.18]O, proxy for temperature) and atmospheric impurities. A time scale was established with the use of altered seasonal variations, some volcanic horizons, and the age for the end of the Wisconsin ice age determined from the GRIP and GISP2 ice cores. There is pre-Holocene ice near the bed. The change in [Delta.sup.18]O since the last glacial maximum (LGM) is at least 12.5 per mil, compared with an expected value of 7 per mil, suggesting that LGM ice originated at the much higher elevations of the then existing Foxe Dome and Foxe Ridge of the Laurentide Ice Sheet. The LGM [Delta.sup.18]O values suggest thick ice frozen to the bed of Hudson Bay., The Penny Ice Cap on Cumberland Peninsula, Baffin Island, is the southernmost major ice cap in Canada. During the Wisconsin Ice Age, the ice cap was connected to Foxe Dome(1, [...]

Stream networks are sensitive to low rates of surface uplift and can be used to decipher the history of large earthquakes even where faults do not rupture the surface, as in intraplate seismic zones. Statistical analysis of alluvial network data from topographic maps in the New Madrid seismic zone, in the central United States, shows that stream-segment gradients deviate the most from an estimated natural stream profile where surface uplift is greatest. Evidence of cumulative deformation distilled from stream network patterns represents at least several meters of differential surface uplift during Holocene time, which suggests that more than one cycle of surface deformation occurred., Landform geometry reflects crustal tectonics, and geomorphic features provide a bridge between deformation on the time scales of several earthquake cycles ([10.sup.2] to [10.sup.4] years) and recent geodetic surveys (1 [...]

Radiocarbon-dated deltaic sequences of Holocene age from different parts of the world began to accumulate within a restricted time range, from about 8500 to 6500 years ago. Evaluation of major delta processes indicates that deceleration in sea-level rise was the key factor in Holocene delta formation. Within many deltas, there is as much as a 2000-year age range between basal deposits in seaward and landward cores. This age difference records the progressive landward migration of near mean sea-level depositional environments during the lower to mid-holocene. Establishment of a chronostratigraphic framework for Holocene delta development provides a fundamental global baseline for distinguishing sea-level change from vertical land motion by tectonism and isostasy, and for evaluating rates of future marine incursion into low-lying deltas., Deltas are vital food-producing areas and population centers, but as low-lying littoral regions they are highly vulnerable to even minor changes in sea level, particularly because most deltas are actively [...]

CHANGES IN FLORAL ZONES IN East Africa during the late Quaternary have been shown by analyses of pollen from cores in swamps and lakes [1]. Pollen provides taxonomic identifications of [...]

A high-resolution oxygen-isotope record from a thorium-uranium-dated stalagmite from southern Oman reflects variations in the amount of monsoon precipitation for the periods from 10.3 to 2.7 and 1.4 to 0.4 thousand years before the present (ky B.P.). Between 10.3 and 8 ky B.P., decadal to centennial variations in monsoon precipitation are in phase with temperature fluctuations recorded in Greenland ice cores, indicating that early Holocene monsoon intensity is largely controlled by glacial boundary conditions. After ~8 ky B.P., monsoon precipitation decreases gradually in response to changing Northern Hemisphere summer solar insolation, with decadal to multidecadal variations in monsoon precipitation being linked to solar activity., Although lake [e.g. (1-3)] and marine [e.g. (4, 5)] records uniformly indicate that a major intensification in Indian Ocean monsoon (IOM) occurred at ~10 ky B.P., discrepancies exist about the [...]

Analysis of ice from Dye-3, Greenland, has demonstrated that the transition between the Younger Dryas and Holocene climate periods occurred over a 40-year period. A near annually resolved, multiparameter record of the transition recorded in the GISP2 core from Summit, Greenland, shows that most of the transition occurred in a series of steps with durations of about 5 years. Some climate proxies associated with mid-latitude sources appear to have changed about 15 years before climate proxies associated with more northern regions. Changes in atmospheric water vapor are likely to have played a large role in the climate transition., The Greenland Ice Sheet Project II (GISP2) and Greenland Ice Core Project (GRIP) ice cores were collected at the summit of the Greenland ice sheet at locations selected to obtain [...]

Lanceolate bifacial points, including one fluted specimen, have been collected from beneath an early Holocene tephra at the Uptar site, northeastern Siberia. Thus, the technology associated with the well-known Paleoindian tradition was not confined to the Americas. The Uptar collection does not compare readily with other Beringian complexes and demonstrates that there is greater diversity in the archaeological record of northeastern Siberia than traditional colonization models imply., During the Pleistocene epoch far northwestern North America was the eastern part of a vast subcontinent, named Beringia, that connected the Old and New Worlds. The Bering Land Bridge provided [...]

A depth-age scale and an accumulation history for the Holocene have been established on the Greenland Ice Sheet Project 2 (GISP2) deep core, providing the most continuously dated record of annual layer accumulation currently available. The depth-age scale was obtained with the use of various independent techniques to count annual layers in the core. An annual record of surface accumulation during the Holocene was obtained by correcting the observed layer thicknesses for flow-thinning. Fluctuations in accumulation provide a continuous and detailed record of climate variability over central Greenland during the Holocene. Climate events, including 'Little Ice Age' type events, are examined., The GISP2 ice core was drilled from surface to bedrock to obtain a paleoclimatic history spanning the last 200,000 years. The summit drilling site is located at 72.6N, 38.5 ° [...]

Midwestern Holocene Paleoenvironments Revealed by Floodplain Deposits in Northeastern Iowa SITES FOR LATE-GLACIAL AND HOLO-cene paleoecological studies are rare beyond the Wisconsinan glacial margin in the upper Midwest. Lakes and [...]

Columnar stalagmites in caves of the Guadalupe Mountains during the late Holocene record a 4000-year annually resolved climate history for the southwestern United States. Annual banding, hiatuses, and high-precision uranium-series dating show a present day--like climate from 4000 to 3000 years ago, following a drier middle Holocene. A distinctly wetter and cooler period from 3000 to 800 years ago was followed by a period of present day--like conditions, with the exception of a slightly wetter interval from 440 to 290 years before the present. The stalagmite record correlates well with the archaeological record of changes in cultural activities of indigenous people. Such climate change may help to explain evidence of dwelling abandonment and population redistribution., We present high-resolution late Holocene climate reconstruction for the southwestern United States on the basis of variations in annual band thickness, growth--no growth records, differences in mineralogy, and high-precision uranium-series [...]

During the past 10,000 years or so--the Holocene--climate in high-latitude regions has been relatively stable compared to glacial times, but the tropics underwent dramatic hydrological shifts. On page 2307 of [...]

Modern complex societies exhibit marked resilience to interannual-to-decadal droughts, but cultural responses to multidecadal-to-multicentury droughts can only be addressed by integrating detailed archaeological and paleoclimatic records. Four case studies drawn from New and Old World civilizations document societal responses to prolonged drought, including population dislocations, urban abandonment, and state collapse. Further study of past cultural adaptations to persistent climate change may provide valuable perspective on possible responses of modern societies to future climate change., In the spring of 1785, the geologist James Hutton presented a lecture to the Royal Society of Edinburgh that changed scientific inquiry into natural processes. The essence of his view [...]

The reconstruction of Global temperatures during the last millennium can provide important clues for how climate may change in the future. A recent, widely cited reconstruction (1) leaves the impression [...]

A high-resolution ice core record from Dasuopu, Tibet, reveals that this site is sensitive to fluctuations in the intensity of the South Asian Monsoon. Reductions in monsoonal intensity are recorded by dust and chloride concentrations. The deeper, older sections of the Dasuopu cores suggest many other periods of drought in this region, but none have been of greater intensity than the greatest recorded drought, during 1790 to 1796 A.D. of the last millennium. The 20th century increase in anthropogenic activity in India and Nepal, upwind from this site, is recorded by a doubling of chloride concentrations and a fourfold increase in dust. Like other ice cores from the Tibetan Plateau, Dasuopu suggests a large-scale, plateau-wide 20th-century warming trend that appears to be amplified at higher elevations., The Holocene climate of the southern Tibetan Plateau has been dominated by the South Asian Monsoon in the summer and by westerly cyclonic activity in the winter. The strength of [...]

A faunal record of sea-surface temperature (SST) variations off West Africa documents a series of abrupt, millennial-scale cooling events, which punctuated the Holocene warm period. These events evidently resulted from increased southward advection of cooler temperate or subpolar waters to this subtropical location or from enhanced regional upwelling. The most recent of these events was the Little Ice Age, which occurred between 1300 to 1850 A.D., when subtropical SSTs were reduced by 3 ° to 4 ° C. These events were synchronous with Holocene changes in subpolar North Atlantic SSTs, documenting a strong, in-phase link between millennial-scale variations in high- and low-latitude climate during the Holocene., The warm climate of the Holocene epoch [the last 11,700 thousand years (11.7 ky B.P.)] conventionally has been viewed as climatically stable (1) with little evidence of the abrupt millennial-scale [...]

Understanding past climate depends, to a large extent, on understanding the circulation of oceanic deep water masses because the atmosphere contains so much less mass and heat than the oceans [...]

Large-magnitude, rapid climate change events--some taking place within just a few decades, less than the span of a single human lifetime (1)--characterized the last glacial period, between about 50,000 and [...]

The inverse relation between atmospheric carbon dioxide concentration and stomatal frequency in tree leaves provides an accurate method for detecting and quantifying century-scale carbon dioxide fluctuations. Stomatal frequency signatures of fossil birch leaves reflect an abrupt carbon dioxide increase at the beginning of the Holocene. A succeeding carbon dioxide decline matches the Preboreal Oscillation, a 150-year cooling pulse that occurred about 300 years after the onset of the Holocene. In contrast to conventional ice core estimates of 270 to 280 parts per million by volume (ppmv), the stomatal frequency signal suggests that early Holocene carbon dioxide concentrations were well above 300 ppmv., The records of the relation of greenhouse gases to Quaternary climate change come largely from ice cores from Antarctica and Greenland. Trends in the atmospheric [CO.sub.2] amount parallel those of [...]

The period between about 8000 and 3000 years before present (yrs B.P.) was a time of profound cultural transitions: The first temple mounds were constructed in Peru, the first pyramids [...]

A record of oxygen isotopes in biogenic opal, 4200 to 1200 calibrated years before the present, from a high-altitude proglacial lake on Mount Kenya, East Africa, exhibits short-term fluctuations on a time scale of centuries as well as tong-term variations. The short-term fluctuations are attributed to changes in the glacier meltwater input, and the long-term variations are related to changes in lake temperature. The record indicates that the climate was warm in Equatorial East Africa from 2300 to 1500 years before the present., The Holocene, although relatively more stable than the Late Pleistocene, was also subject to abrupt climatic changes (1, 2). Small, low-latitude glaciers are especially sensitive to such climatic changes (3). [...]

Since the first quantitative measurements of ice-age temperatures (1) in the early 1950s, there has been controversy over the use of oxygen isotopes of marine carbonates in reconstructing past climate. [...]

Sediments from Lunkaransar dry lake in northwestern India reveal regional water table and lake level fluctuations over decades to centuries during the Holocene that are attributed to changes in the southwestern Indian monsoon rains. The lake levels were very shallow and fluctuated often in the early Holocene and then rose abruptly around 6300 carbon-14 years before the present ([sup.14]C yr B.P.). The lake completely desiccated around 4800 [sup.14]C yr B.P. The end of this 1500-year wet period coincided with a period of intense dune destabilization. The major Harrapan-Indus civilization began and flourished in this region 1000 years after desiccation of the lake during arid climate and was not synchronous with the lacustral phase., The southwestern Indian monsoon is critical for understanding past global and regional monsoon variations (1-3). The few records of Holocene monsoon variations from the areas that border the Arabian Sea [...]