Down‐welling circulation of the northwest European continental shelf: A driving mechanism for the continental shelf carbon pump

Abstract

Annually integrated measurements of pCO2 have demonstrated that seasonally stratified regions of temperate shelf seas can be an important sink of atmospheric CO2. A key process to support this sink is the transport of carbon from shelf seas to below the permanent pycnocline of the deep ocean. Using a hydrodynamic model simulation of the northwest European Continental shelf, we find that both the large scale circulation and frictional processes support the off‐shelf transport of carbon sufficiently quickly to remove ∼40% of the carbon sequestered by one growing season before the onset of the next. This transport is highly heterogeneous, with some regions being only weakly flushed. Only 52% of this exported carbon is transported below the permanent pycnocline, hence the shelf sea and open ocean carbon cycles are intrinsically coupled.