Continental shelf pump
In oceanic biogeochemistry, the continental shelf pump is proposed to operate in the shallow waters of the continental shelves, acting as a mechanism to transport carbon (as either dissolved or particulate material) from surface waters to the interior of the adjacent deep ocean. Overview. Originally formulated by Tsunogai "et al." (1999), the pump is believed to occur where the solubility and biological pumps interact with a local hydrography that feeds dense water from the shelf floor into sub-surface (at least subthermocline) waters in the neighbouring deep ocean. Tsunogai "et al."'s (1999) original work focused on  the East China Sea, and the observation that, averaged over the year, its surface waters represented a sink for carbon dioxide. This observation was combined with others of the distribution of dissolved carbonate and alkalinity and explained as follows : Significance. Based on their measurements of the CO flux over the East China Sea (35 g C m y), Tsunogai "et al." (1999) estimated that the continental shelf pump could be responsible for an air-to-sea flux of approximately 1 Gt C y over the world's shelf areas. Given that observational and modelling of anthropogenic emissions of CO estimates  suggest that the ocean is currently responsible for the uptake of approximately 2 Gt C y, and that these estimates are poor for the shelf regions, the continental shelf pump may play an important role in the ocean's carbon cycle. One caveat to this calculation is that the original work was concerned with the hydrography of the East China Sea, where cooling plays the dominant role in the formation of dense shelf water, and that this mechanism may not apply in other regions. However, it has been suggested that other processes may drive the pump under different climatic conditions . For instance, in polar regions, the formation of sea-ice results in the extrusion of salt that may increase seawater density. Similarly, in tropical regions, evaporation may increase local salinity and seawater density. The strong sink of CO at temperate latitudes reported by Tsunogai "et al." (1999) was later confirmed in the Gulf of Biscay, the Middle Atlantic Bight and the North Sea. On the other hand, in the sub-tropical South Atlantic Bight reported a source of CO to the atmosphere. Recently, work has compiled and scaled available data on CO fluxes in coastal environments, and shown that globally  marginal seas act as a significant CO sink (-1.6 mol C m y; -0.45 Gt C y) in agreement with previous estimates. However, the global sink of CO in marginal seas could be almost fully compensated by the emission of CO (+11.1 mol C m y; +0.40 Gt C y) from the ensemble of near-shore coastal ecosystems, mostly related to the emission of CO from estuaries (0.34 Gt C y). An interesting application of this work has been examining the impact of sea level rise over the last de-glacial transition on the global carbon cycle. During the last  glacial maximum sea level was some lower than today. As sea level rose the surface area of the shelf seas grew and in consequence the strength of the shelf sea pump should increase.