Oceanic upwelling effects

This type of data raises the issue of the constancy of the oceanic circulation patterns over the region in question. In this case the question is to what degree the values cited in Figure 6 could be used to estimate oceanic upwelling effects along the continental margins of the Western Hemisphere as one moves back into the early Holocene and terminal Pleistocene. Table I lists a series of paired terrestrial organics/marine... 

Sarnthein, M., Winn, K. and Zahn, R., 1987. Paleoproductivity of oceanic upwelling and the effect of atmospheric CO and climatic change during deglaciation times. In Berger, W.H. and Labeyrie, L.D. (eds), Abrupt climatic change. Reidel, Dordrecht, pp 311-337. 

A further factor affecting k- is the air-sea temperature difference. When the sea is colder than the air above it, the enhanced solubility of the gas in the water (relative to the air temperature) tends to increase kj. This will occur in summer in sub-polar waters and over upwelling regions. The opposite is also found, and much of the ocean equatorward of 45"" latitude is colder than the overlying air for much of the year. However, air-sea temperature differences are generally less than 2-3 "C so that this effect results in a less than 10% modulation of k- on average. 

The DSi stripped out of the Southern Ocean s surfece waters at the site of SAMW formation is converted to BSi. This BSi eventually sinks into the deep waters (CDW), where it is remineralized to DSi and driven back south to be upwelled again into the surface waters. This trapping effect is a large part of why half of the global marine sedimentary sink of BSi is located in the Southern Ocean. South of 55°S, iron limitation is so severe, as compared to the rate of upweiiing supply of DSi, that the diatoms are not able to reduce silicic acid concentrations to zero. 

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