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The equatorial Pacific Ocean is one of the major high-nutrient, low-chlorophyll regions in the global ocean. In such regions, the consumption of the available macro-nutrients such as nitrate and phosphate is thought to be limited in part by the low abundance of the critical micro-nutrient iron (1). Greater atmospheric dust deposition (2) could have fertilized the equatorial Pacific with iron during the last ice age--the Last Glacial Period (LGP)--but the effect of increased ice-age dust fluxes on primary productivity in the equatorial Pacific remains uncertain (3-6). Here we present meridional transects of dust (derived from the [sup.232]Th proxy), phytoplankton productivity (using opal, [sup.231]Pa/[sup.230]Th and excess Ba), and the degree of nitrate consumption (using foraminifera-bound δ[sup.15]N) from six cores in the central equatorial Pacific for the Holocene (0-10,000 years ago) and the LGP (17,000-27,000 years ago). We find that, although dust deposition in the central equatorial Pacific was two to three times greater in the LGP than in the Holocene, productivity was the same or lower, and the degree of nitrate consumption was the same. These biogeochemical findings suggest that the relatively greater ice-age dust fluxes were not large enough to provide substantial iron fertilization to the central equatorial Pacific. This may have been because the absolute rate of dust deposition in the LGP (although greater than the Holocene rate) was very low. The lower productivity coupled with unchanged nitrate consumption suggests that the subsurface major nutrient concentrations were lower in the central equatorial Pacific during the LGP. As these nutrients are today dominantly sourced from the Subantarctic Zone of the Southern Ocean, we propose that the central equatorial Pacific data are consistent with more nutrient consumption in the Subantarctic Zone, possibly owing to iron fertilization as a result of higher absolute dust fluxes in this region (7, 8). Thus, ice-age iron fertilization in the Subantarctic Zone would have ultimately worked to lower, not raise, equatorial Pacific productivity., The major nutrients for phytoplankton growth (nitrogen, phosphorus and silicon) are supplied to the surface waters of the equatorial Pacific by wind-driven upwelling along the Equator. Their consumption by phytoplankton [...]

A major puzzle of paleoclimatology is why, after a tong interval of cooling climate, each late Quaternary ice age ended with a relatively short warming leg called a termination. We here offer a comprehensive hypothesis of how Earth emerged from the last global ice age. A prerequisite was the growth of very large Northern Hemisphere ice sheets, whose subsequent collapse created stadial conditions that disrupted global patterns of ocean and atmospheric circulation. The Southern Hemisphere westerlies shifted poleward during each northern stadial, producing pulses of ocean upwelling and warming that together accounted for much of the termination in the Southern Ocean and Antarctica. Rising atmospheric C[O.sub.2] during southern upwelling pulses augmented warming during the last termination in both polar hemispheres. 10.1126/science.1184119

Wind-driven upwelling in the ocean around Antarctica helps regulate the exchange of carbon dioxide (C[O.sub.2]) between the deep sea and the atmosphere, as well as the supply of dissolved silicon to the euphoric zone of the Southern Ocean. Diatom productivity south of the Antarctic Polar Front and the subsequent burial of biogenic opal in underlying sediments are limited by this silicon supply. We show that opal burial rates, and thus upwelling, were enhanced during the termination of the last ice age in each sector of the Southern Ocean. In the record with the greatest temporal resolution, we find evidence for two intervals of enhanced upwelling concurrent with the two intervals of rising atmospheric C[O.sub.2] during deglaciation. These results directly link increased ventilation of deep water to the deglacial rise in atmospheric C[O.sub.2].

The increase in export production in the Southern Ocean contributed to low levels of carbon dioxide and high levels of iron in the glacial atmosphere. The winds from Patagonian deserts transported iron to the Southern Ocean. The observations compare well with the fact that the iron depletion in the Ocean in the glacial periods was reduced by iron-rich winds. The fluxes of biogenic detritus out of surface waters were high in the glacial periods.

Two isotopes, 231 protactinium (231Pa) and 230 thorium (230Th), can be used to estimate fluctuations in the productivity of the Southern Ocean during glacial and interglacial periods. These isotopes are useful because how much of them is deposited in ocean sediments depends on the activity of marine plankton, which in turn depends on atmospheric carbon dioxide levels. Ratios of 231Pa and 230Th show that productivity in the Atlantic south of the Antarctic polar front (APF) was lower during glacial periods than during interglacials but that the converse was true north of the APF.

The chemocline rise in the Black Sea by 40-50 meters was due to natural forcing. This was observed from analyses of shelf sediments obtained from the Black Sea's Bosporous region. Paleochemocline dynamics can be determined by geochemical signals obtained from the analyses. The chemocline/pycnocline dynamics of the Black Sea is confirmed by its tens of meters water-column structures.