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The chronology of deglacial meltwater pulses from the Laurentide Ice Sheet is well documented. However, the deglacial history of the North American-Arctic (north-eastern Laurentide and Innuitian) and western Greenland ice sheets draining into the Labrador Sea via Baffin Bay is less well constrained. Here we present new high-resolution, radiocarbon-dated records from the central Baffin Bay spanning ∼17 to 10 kyr BP and documenting the full deglacial history of Baffin Bay. Sedimentological and geochemical data confirm the presence of two periods of enhanced detrital carbonate delivery, termed Baffin Bay Detrital Carbonate Events (BBDCs). These events are dated to ∼14.2–13.7 kyr BP and ∼12.7–11 kyr BP. They are synchronous across Baffin Bay and their mineralogical signature indicates a common source of detrital carbonate from northern Baffin Bay. The first event, BBDC 1, postdates Heinrich Event 1 and the second event, BBDC 0, predates the recently revised timing of Heinrich Event 0. The onset of the BBDC events appears not to be systematically linked to Greenland temperature change as they occur during both interstadial and stadial periods. This indicates that deglaciation of North American-Arctic and western Greenland ice sheets with the associated iceberg and meltwater discharge were decoupled from the dominant North Atlantic climate mode, where iceberg discharge events from the Laurentide Ice Sheet occurred during stadial periods.

Stable carbon and oxygen isotopes from benthic and planktic foraminifers, planktic foraminifer assemblages and ice rafted debris from the North Atlantic Site U1314 (Integrated Ocean Drilling Program Expedition 306) were examined to investigate orbital and millennial-scale climate variability in the North Atlantic and its impact on global circulation focusing on the development of glacial periods during the mid-Pleistocene (ca 800–400 ka). Glacial initiations were characterized by a rapid cooling (6–10 °C in less than 7 kyr) in the mean annual sea surface temperature (SST), increasing benthic δ18O values and high benthic δ13C values. The continuous increase in benthic δ18O suggests a continuous ice sheet growth whereas the positive benthic δ13C values indicate that the flow of the Iceland Scotland Overflow water (ISOW) was vigorous. Strong deep water formation in the Norwegian Greenland Sea promoted a high transfer of freshwater from the ocean to the continents. However, low SSTs at Site U1314 suggest a subpolar gyre cooling and freshening that may have reduced deep water formation in the Labrador Sea during glacial initiations. Once the 3.5‰ threshold in the benthic δ18O record was exceeded, ice rafting started and ice sheet growth was punctuated by millennial-scale waning events which returned to the ocean part of the freshwater accumulated on the continents. Ice-rafting events were associated with a rapid reduction in the ISOW (benthic δ13C values dropped 0.5–1‰) and followed by millennial-scale warmings. The first two millennial-scale warm intervals of each glacial period reached interglacial temperatures and were particularly abrupt (6–10 °C in ∼3 kyr). Subsequent millennial-scale warm events were cooler probably because the AMOC was rather reduced as suggested by the low benthic δ13C values. These two abrupt warming events that occurred at early glacial periods were also observed in the Antarctic temperature and CO2 records, suggesting a close correlation between both Hemispheres. The comparison of the sea surface proxies with the benthic δ18O record (as the Southern sign) indicates the presence of a millennial-scale seesaw pattern similar to that seen during the Last Glacial period.

Changes in the orbital parameters, solar output, and ocean circulation are widely considered as main drivers of the Holocene climate. Yet, the interaction between these forcings and the role that they play to produce the pattern of changes observed in different domains of the climate system remain debated. Here, we present new early to middle Holocene season-specific sea surface temperature (SST) and d 18 Oseawater results, based on organic-walled dinoflagellate cyst and planktonic foraminiferal data from two sediment cores located in the central (SL21) and south-eastern (LC21) Aegean Sea (eastern Mediterranean). Today, this region is affected by high to mid latitude climate in winter and tropical/ subtropical climate in summer. The reconstructed d 18 O seawater from LC21 displays a marked (w1.3%) negative shift between 10.7 and 9.7 ka BP, which represents the regional expression of the orbitally driven African monsoon intensification and attendant freshwater flooding into the eastern Mediterranean. A virtually contemporaneous shift, of the same sign and magnitude, is apparent in the d 18 Ospeleothem record from Soreq Cave (Northern Israel), an important part of which may therefore reflect a change in the isotopic composition of the moisture source region (Aegean and Levantine Seas). Our SST reconstructions show that Aegean winter SSTs decreased in concert with intensifications of the Siberian High, as reflected in the GISP2 nss [K þ ] record. Specifically, three distinct sea surface cooling events at

We present a new reconstruction of Mediterranean sea surface temperatures (SST) during the last glacial maximum (LGM). A calibration data set based on census counts of 23 species of planktonic foraminifera in 129 North Atlantic and 145 Mediterranean core top samples was used to develop summer, winter and annual average SST reconstructions using artificial neural networks (ANNs) and the revised analogue method (RAM). Prediction errors determined by cross-validation of the calibration data set ranged between 0.5 and 1.1 °C, with both techniques being most successful in predicting winter SSTs. Glacial reconstructions are based on a new, expanded data set of 273 samples in 37 cores with consistent minimum level of age control. The new LGM reconstructions suggest that the east–west temperature gradient during the glacial summer was 9 °C, whereas during the glacial winter, the gradient was 6 °C, both some 4 °C higher than that existing today. In contrast to earlier studies, our results tend to suggest much cooler SST estimates throughout the glacial Mediterranean, particularly in the eastern basin where previous SST reconstructions indicated a decrease of only 1 °C. Our new SST reconstructions will provide the modelling community with a detailed and updated portrayal of the Mediterranean Sea during the LGM, setting new targets on which glacial simulations can be tested.

We present a detailed comparison of five “transfer function” techniques calibrated to reconstruct sea-surface temperature (SST) from planktic foraminifer counts in western Pacific surface sediments. The techniques include the Imbrie–Kipp method (IKM), modern analog technique (MAT), modern analog technique with similarity index (SIMMAX), revised analog method (RAM), and the artificial neural network technique (ANN). The calibration is based on a new database of 694 census counts of planktic foraminifers in coretop samples from the western Pacific, compiled under a cooperative effort within the MARGO (multiproxy approach for the reconstruction of the glacial ocean surface) project. All five techniques were used to reconstruct SST variation in a well-dated Holocene to last glacial maximum interval in core MD972151 from the southern South China Sea (SCS) to evaluate the magnitude of cooling in the western tropical Pacific during the LGM. Our results suggest that MAT, SIMMAX, RAM and ANN show a similar level of performance in SST estimation and produce ⩽1 °C uncertainties in coretop SST calibrations of the western Pacific. When applying these techniques to the downcore faunal record, the IKM, which performed significantly worst in the calibration exercise, produced glacial SST estimates similar to present-day values, whereas the other four techniques all indicated ∼1 °C cooler glacial SST. Because of their better performance in the calibration dataset, and because of the convergence among the techniques in the estimated magnitude of glacial cooling in the studied core, we conclude that MAT, SIMMAX, RAM and ANN provide more robust planktic foraminifer paleo-SST estimates than traditional IKM techniques in western Pacific paleoceanographic studies.

IMAGES core MD01-2416 (511N, 1681E) provides the first centennial-scale multiproxy record of Holocene variation in North Pacific sea-surface temperature (SST), salinity, and biogenic productivity. Our results reveal a gradual decrease in subarctic SST by 3–51C from 11.1 to 4.2 ka and a stepwise long-term decrease in sea surface salinity (SSS) by 2–3 p.s.u. Early Holocene SSS were as high as in the modern subtropical Pacific. The steep halocline and stratification that is characteristic of the present-day subarctic NorthPacific surface ocean is a fairly recent feature, developed as a product of mid-Holocene environmental ch ange. HighSSS matched a salient productivity maximum of biogenic opal during Bolling-to-Early Holocene times, reaching levels similar to those observed during preglacial times in the warm mid-Pliocene prior to 2.73 Ma. Similar productivity spikes marked every preceding glacial termination of the last 800 ka, indicating recurrent short-term events of mid-Pliocene-style intense upwelling of nutrient-rich Pacific Deepwater in the Pleistocene. Such events led to a repeated exposure of CO2-richdeepwater at the ocean surface facilitating a transient CO2 release to the atmosphere, but the timing and duration of these events repudiate a long-term influence of the subarctic NorthPacific on global atmosph eric CO 2 concentration. r 2004 Elsevier Ltd. All rights reserved.

Latest Quaternary benthic foraminifer census counts in four cores from the Yellow Sea (Hwanghae) were analyzed to decipher paleoenvironmental changes in this area since the Last Glacial Maximum. Principal component analyses of samples from two cores in the central Yellow Sea indicate that the faunal variation in these cores re#ects a sequence of distinct assemblages divided by sharp boundaries. The shifts between individual biofacies correspond to changes in geochemical and lithological composition of the sediments, and stable-isotope ratios of foraminiferal shells, and most can be correlated between cores. The major faunal transition, at a clear increase in bottom-water salinity, occurred between 8.47 and 6.63 ka, and may indicate the establishment of modern-type circulation in the Yellow Sea. The inferred threshold size of the Yellow Sea Basin for the establishment of such circulation seems to be rather close to its present-day extent. Faunal shifts at 10.6 and 4.67 ka probably re#ect changes in the intensity of river runo!, associated sediment and organic carbon delivery, and bottom-water oxygenation. Changes in benthic foraminifer faunas between 12.9 and 11.75 ka may signal the Younger Dryas climatic oscillation in the Yellow Sea. The Lateglacial marine transgression reached the central part of the Yellow Sea around 15.09 ka. Possibly, an uplift of the central and eastern Yellow Sea area during the late Holocene can explain the discrepancy between the timing of the transgression in the Yellow Sea and the global sea-level curve. ( 2000 Published by Elsevier Science Ltd. All rights reserved.