Characteristics of the deep ocean carbon system during the past 150,000 years: ΣCO 2 distributions, deep water flow patterns, and abrupt climate change

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Abstract
Studies of carbon isotopes and cadmium in bottom-dwelling foraminifera from ocean sediment cores have advanced our knowledge of ocean chemical distributions during the late Pleistocene. Last Glacial Maximum data are consistent with a persistent high-ΣCO 2 state for eastern Pacific deep water. Both tracers indicate that the mid-depth North and tropical Atlantic Ocean almost always has lower ΣCO 2 levels than those in the Pacific. Upper waters of the Last Glacial Maximum Atlantic are more ΣCO 2 -depleted and deep waters are ΣCO 2 -enriched compared with the waters of the present. In the northern Indian Ocean, δ 13 C and Cd data are consistent with upper water ΣCO 2 depletion relative to the present. There is no evident proximate source of this ΣCO 2 -depleted water, so I suggest that ΣCO 2 -depleted North Atlantic intermediate/deep water turns northward around the southern tip of Africa and moves toward the equator as a western boundary current. At long periods (>15,000 years), Milankovitch cycle variability is evident in paleochemical time series. But rapid millennial-scale variability can be seen in cores from high accumulation rate series. Atlantic deep water chemical properties are seen to change in as little as a few hundred years or less. An extraordinary new 52.7-m-long core from the Bermuda Rise contains a faithful record of climate variability with century-scale resolution. Sediment composition can be linked in detail with the isotope stage 3 interstadials recorded in Greenland ice cores. This new record shows at least 12 major climate fluctuations within marine isotope stage 5 (about 70,000–130,000 years before the present).

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