Antarctic Ocean Polar Front

Silicate concentrations also can be used to distinguish different water masses. The most obvious example is at the Southern Ocean Polar Front (see Figure 2), which separates Antarctic Surface Water from the Subantarctic system. The silicate and nitrate concentration gradients across these Southern Ocean waters occur in different locations (in a manner similar to the distinct maxima in their vertical profiles). The high concentrations of silicate (50-100 pmol N ) south of the Polar Front result from wind-induced upwelling bringing silicate to the surface faster than the local biota can turn it into particulate silica. Turnover times between surface waters and... 

Paleoproductivity studies in the Southern Ocean, where the deep-reaching Antarctic circumpolar current causes substantial sediment redistribution, have been especially dependent on the °Th-profiling method to obtain accumulation rates of opal, excess barium, organic carbon, and other paleoproductivity proxies (Anderson et al., 2002, 1998 Chase et al., 2003a Francois et al., 1997, 1993 Frank, 1996 Frank et al., 2000 Kumar et al., 1995). Studies of the Atlantic and Indian sectors of the Southern Ocean concluded that productivity in regions south of the Antarctic polar front was lower... 

In remote regions of the open ocean that receive little atmospheric input, the vertical transport of iron-rich deep waters is particularly important [73,156]. The primary source of iron to the Fe-limited Southern Ocean is entrainment of Fe-enriched water during deep winter mixing, augmented by the summer upwelling of circumpolar deep water at the Polar Front and the southern front of the Antarctic Circumpolar Current [119,155,157]. 

However, Cd P ratios of phytoplankton in surface waters or derived from phytoplankton cultures are not directly comparable to those estimated from dissolved Cd and PO4 concentrations in the nutricline, as only phytoplankton species that are exported out of the euphotic zone will leave an imprint of their Cd P ratios in the nutricline. The relative recycling efficiency of P versus Cd in the nutricline may also affect these estimates. Yet, according to a study in the Antarctic Polar Front region [119], preferential Cd uptake by phytoplankton overrides the more efficient recycling of Cd (50-95%) compared to PO4 (35%) in the upper ocean. Hence, phytoplankton Cd uptake at the surface and export out of the surface waters will greatly affect the dissolved Cd and PO " concentrations in nutriclines, and ultimately the estimated particulate Cd P ratios. 

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