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A Macintosh computer program that can perform many time‐series analysis procedures is now available on the Internet free of charge. Although AnalySeries was originally designed for paleoclimatic time series, it can be useful for most fields of Earth sciences. The program's graphical user interface allows easy access even for people unfamiliar with computer calculations. Previous versions of the program are already used by hundreds of scientists worldwide.

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The degree of similarity of the •13C records of the planktonic foraminiferal species N. pachyderma and of the benthic foraminiferal genus Cibicides in the highlatitude basins of the world ocean is used as an indicator of the presence of deepwater sources during the last climatic cycle. Whereas continuous formation of deep water is recognized in the southern ocean, the Norwegian Sea stopped acting as a sink for surface water during isotope stage 4 and the remainder of the last glaciation. However, deep water formed in the north Atlantic south of the Norwegian Sea during the last

The nitrogen-isotope record preserved in Southern Ocean sediments, along with several geochemical tracers for the settling fluxes of biogenic matter, reveals patterns of past nutrient supply to phytoplankton and surface-water stratification in this oceanic region. Areal averaging of these spatial patterns indicates that reduction of the CO 2 'leak' from ocean to atmosphere by increased surface-water stratification south of the Polar Front made a greater contribution to the lowering of atmospheric CO 2 concentration during the Last Glacial Maximum than did the increased export of organic carbon from surface to deep waters occurring further north.The unstratified, nutrient-rich surface waters in the modern highlatitude ocean provide the main conduit for transferring deep-water CO 2 back into the atmosphere. This CO 2 'leak' to the atmosphere is particularly effective in the modern Southern Ocean, because of intensive vertical mixing and low nutrient utilization. Building on this observation, a series of papers 1-6 attributed the glacial lowering of atmospheric CO 2 either to enhanced biological removal of the nutrients and CO 2 in high-latitude surface waters resulting in higher sinking fluxes of organic matter (that is, higher export production), or to a lower supply rate of nutrients and CO 2 from intermediate waters produced by lower vertical mixing. But the extensive deepor intermediate-water anoxia predicted by these models, and the lack of palaeo-oceanographic evidence for increased export production in the glacial Southern Ocean, has led to the questioning of the validity of these models. Here we present new evidence which supports increased stratification south of the position of the modern Polar Front (MPF) during the Last Glacial Maximum as a mechanism that contributed to lower glacial atmospheric CO 2 and deep-water oxygen concentration.The sedimentary record of several palaeoproductivity proxies was recently presented as support for a large increase in the export flux of organic carbon in the Atlantic sector of the Southern Ocean, north of the position of the MPF, which could have contributed to lowering glacial atmospheric CO 2 as a result of Fe fertilization 7 . Here we combine a similar suite of geochemical proxies for palaeoproductivity and its fate with bulk-sediment d 15 N values to better constrain past changes in the nutrient balance of surface waters and its influence on atmospheric CO 2 . Bulk-sediment d 15 N provides a means of evaluating the fraction of surface nitrate utilized by phytoplankton [8][9][10][11] . By combining this information with export flux of nitrogen estimated from palaeoproductivity proxies, we constrain the supply rate of nitrate to surface waters. Our results indicate that, despite higher export flux of organic carbon in the Atlantic sector of the Southern Ocean north of the MPF during the last glacial period, the fraction of nitrate utilized by phytoplankton in this region did not increase, implying a sustained supply of nutrients (and thus CO 2 ) to surface waters. In...

Using 95 epibenthic δ13C records, eight time slices were reconstructed to trace the distribution of east Atlantic deepwater and intermediate water masses over the last 30,000 years. Our results show that there have been three distinct modes of deepwater circulation: Near the stage 3‐2 boundary, the origin of North Atlantic Deep Water (NADW) was similar to today (mode 1). However, after late stage 3 the source region of the NADW end‐member shifted from the Norwegian‐Greenland Sea to areas south of Iceland (mode 2). A reduced NADW flow persisted during the last glacial maximum, with constant preformed δ13C values. The nutrient content of NADW increased markedly near the Azores fracture zone from north to south, probably because of the mixing of upwelled Antarctic Bottom Water (AABW) from below, which then advected with much higher flux rates into the northeast Atlantic. Later, the spread of glacial meltwater over the North Atlantic led to a marked short‐term ventilation minimum below 1800 m about 13,500 14C years ago (mode 3). The formation of NADW recommenced abruptly north of Iceland 12,800–12,500 years ago and reached a volume approaching that of the Holocene, in the Younger Dryas (10,800–10,350 years B.P.). Another short‐term shutdown of deepwater formation followed between 10,200 and 9,600 years B.P., linked to a further major meltwater pulse into the Atlantic. Each renewal of deepwater formation led to a marked release of fossil CO2 from the ocean, the likely cause of the contemporaneous 14C plateaus. Over the last 9000 years, deepwater circulation varied little from today, apart from a slight increase in AABW about 7000 14C years ago. It is also shown that the oxygenated Mediterranean outflow varied largely independent of the variations in deepwater circulation over the last 30,000 years.