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Radiocarbon in the atmosphere is regulated largely by ocean circulation, which controls the sequestration of carbon dioxide (CO(2)) in the deep sea through atmosphere-ocean carbon exchange. During the last glaciation, lower atmospheric CO(2) levels were accompanied by increased atmospheric radiocarbon concentrations that have been attributed to greater storage of CO(2) in a poorly ventilated abyssal ocean. The end of the ice age was marked by a rapid increase in atmospheric CO(2) concentrations that coincided with reduced (14)C/(12)C ratios (Delta(14)C) in the atmosphere, suggesting the release of very 'old' ((14)C-depleted) CO(2) from the deep ocean to the atmosphere. Here we present radiocarbon records of surface and intermediate-depth waters from two sediment cores in the southwest Pacific and Southern oceans. We find a steady 170 per mil decrease in Delta(14)C that precedes and roughly equals in magnitude the decrease in the atmospheric radiocarbon signal during the early stages of the glacial-interglacial climatic transition. The atmospheric decrease in the radiocarbon signal coincides with regionally intensified upwelling and marine biological productivity, suggesting that CO(2) released by means of deep water upwelling in the Southern Ocean lost most of its original depleted-(14)C imprint as a result of exchange and isotopic equilibration with the atmosphere. Our data imply that the deglacial (14)C depletion previously identified in the eastern tropical North Pacific must have involved contributions from sources other than the previously suggested carbon release by way of a deep Southern Ocean pathway, and may reflect the expanded influence of the (14)C-depleted North Pacific carbon reservoir across this interval. Accordingly, shallow water masses advecting north across the South Pacific in the early deglaciation had little or no residual (14)C-depleted signals owing to degassing of CO(2) and biological uptake in the Southern Ocean.

The greater Agulhas system around southern Africa forms a key component of the global ocean circulation (1-3) (Fig. 1). This system feeds the upper arm of the Atlantic meridional overturning [...], The Atlantic Ocean receives warm, saline water from the Indo-Pacific Ocean through Agulhas leakage around the southern tip of Africa. Recent findings suggest that Agulhas leakage is a crucial component of the climate system and that ongoing increases in leakage under anthropogenic warming could strengthen the Atlantic overturning circulation at a time when warming and accelerated meltwater input in the North Atlantic is predicted to weaken it. Yet in comparison with processes in the North Atlantic, the overall Agulhas system is largely overlooked as a potential climate trigger or feedback mechanism. Detailed modelling experiments--backed by palaeoceanographic and sustained modern observations--are required to establish firmly the role of the Agulhas system in a warming climate.

A characteristic feature of our present ocean circulation is the deep convection that occurs in the North Atlantic and spreads North Atlantic Deep Water (NADW) to the world's abyssal oceans. [...], The meridional overturning circulation (MOC) of the Atlantic Ocean is considered to be one of the most important components of the climate system. This is because its warm surface currents, such as the Gulf Stream, redistribute huge amounts of energy from tropical to high latitudes and influence regional weather and climate patterns, whereas its lower limb ventilates the deep ocean and affects the storage of carbon in the abyss, away from the atmosphere. Despite its significance for future climate, the operation of the MOC under contrasting climates of the past remains controversial. Nutrient-based proxies (1,2) and recent model simulations (3) indicate that during the Last Glacial Maximum the convective activity in the North Atlantic Ocean was much weaker than at present. In contrast, rate-sensitive radiogenic [sup.231]Pa/[sup.230]Th isotope ratios from the North Atlantic have been interpreted to indicate only minor changes in MOC strength (4-6). Here we show that the basin-scale abyssal circulation of the Atlantic Ocean was probably reversed during the Last Glacial Maximum and was dominated by northward water flow from the Southern Ocean. These conclusions are based on new high-resolution data from the South Atlantic Ocean that establish the basin-scale north to south gradient in [sup.231]Pa/[sup.230]Th, and thus the direction of the deep ocean circulation. Our findings are consistent with nutrient-based proxies and argue that further analysis of [sup.231]Pa/[sup.230]Th outside the North Atlantic basin will enhance our understanding of past ocean circulation, provided that spatial gradients are carefully considered. This broader perspective suggests that the modern pattern of the Atlantic MOC--with a prominent southerly flow of deep waters originating in the North Atlantic--arose only during the Holocene epoch.

Rapid reorganization of ocean circulation is believed to exert some control over climate changes on millennial and shorter timescales, as well as shifts in concentrations of atmospheric greenhouse gases. A high-temporal-resolution record of sea surface temperatures from the western tropical North Atlantic Ocean, spanning 29,000 years, is presented, and significant warming is found to be documented for Heinrich event H1 and the Younger Dryas event, indicating that thermohaline circulation was significant in triggering such rapid climate changes.

Shifts in ocean circulation 10,000 years ago did not induce a change in the glacial climate then prevailing, which undermines the assumption that deep ocean circulation affects climate. Two research teams, S.J. Lehman and L.D. Keigwin and T. Veum and colleagues, reached these conclusions after studying North Atlantic core data from the Younger Dryas cold episode, a short glacial period that temporarily halted the warming trend that ended the last Ice Age. With global warming looming as a threat, further research on the causes of climatic changes is needed.

During the past 800,000 years--the late Pleistocene and subsequent Holocene--Earth's climate has swung between cool and warm and back again many times. Variations in incoming solar radiation, modulated by Earth's [...]

Continental palaeo-data procured from parts of Africa and Asia show that post-glacial climate variations in tropics and subtropics are sudden and do not correspond to climate fluctuations in higher latitudes. The findings reveal that these regions experienced short periods of intense aridity and that the long-term humid phase of the post-glacial period led to drought phases. These short-term fluctuations in monsoon climate might be due to the differences in cross-equatorial heat transfer caused by thermohaline circulation.

Studies of deep-sea sediment cores drilled in the North Atlantic to examine the climatic influence of North Atlantic deep water production reveal that oceanic records from the same period correlate greatly with ice core data. Records from the subpolar North Atlantic are stable and their surface and deep-water variability begins only after the Eemian peak interglacial, suggesting that the difference in the subsequent Eemian records are due to localized events. However, available terrestrial data are inadequate to explain the irregular behavior of the Eemian climate.

The article presents a study which analyze the palaeoclimatic records from a marine sediment core in the southwestern Indian Ocean. Result of the study shows that the ocean front separating the warm subtropical ocean from the cold subantartic zone may influence global-scale temperature control from levels of carbon dioxide in the atmosphere. Researchers concluded that severe reduction on the water transport between the Indian and Atlantic oceans may have caused climate to cool beyond typical ice-age conditions.