Air‐sea exchange of carbon dioxide in ocean margins: A province‐based synthesis

In determining global sea‐to‐air CO 2 flux from measurements or models, the ocean margin has not been resolved from the land or the open ocean. Recent studies have indicated that shelves can be either a large sink or a source for atmospheric CO 2 . This CO 2 sink/source term may substantially alter our current view of the global carbon budget for land and oceans. However, past fieldwork and synthesis have focused on a few shelves in the northern temperate zone while the vast majority of other shelves are ignored. By dividing the highly heterogeneous shelves into seven provinces, we suggest that the continental shelves are a sink for atmospheric CO 2 at mid‐high latitudes (−0.33 Pg C a −1 ) and a source of CO 2 at low latitudes (0.11 Pg C a −1 ). Warm temperature and high terrestrial organic carbon input are most likely responsible for the CO 2 release in low latitude shelves.