salt that may increase seawater density. Similarly, in tropical regions, evaporation may increase local salinity and seawater density. The strong sink of CO2 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 CO2 to the atmosphere. Recently, work has compiled and scaled available data on CO2 fluxes in coastal environments, and shown that globally marginal seas act as a significant CO2 sink (-1.6 mol C m−2 y−1; -0.45 Gt C y−1) in agreement with previous estimates. However, the global sink of CO2 in marginal seas could be almost fully compensated by the emission of CO2 (+11.1 mol C m−2 y−1; +0.40 Gt C y−1) from the ensemble of near-shore coastal ecosystems, mostly related to the emission of CO2 from estuaries (0.34 Gt C y−1). 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. References See also Biological pump Ocean acidification Solubility pump Aquatic ecology Biological oceanography Carbon Chemical oceanography Geochemistry Biogeochemistry Continental shelves Oceanographical terminology