Seasonal export of South Atlantic Bight and Mid-Atlantic Bight shelf waters at Cape Hatteras

Abstract

Studies of Middle Atlantic Bight (MAB) shelf water export to the open ocean at Cape Hatteras have produced fairly consistent estimates of ~0.25Sv, with just under half of the total carried within the Shelfbreak Front (SBF), and the remainder carried southward over the MAB shelf inshore of the shelf break and the SBF. Mean northward transport along the northern South Atlantic Bight (SAB) delivers SAB shelf water to the Cape Hatteras, which must also be exported to the open ocean. In the following, the magnitude of year-round SAB shelf water export at Cape Hatteras is estimated for the first time, and is found to be as large as the exported MAB shelf water volumes, with large seasonal variability. In summer, SAB export volume is much larger than the volume of exported MAB shelf water, while in late winter, MAB export volume exceeds that of SAB shelf water. Several aspects of circulation fields at Cape Hatteras that affect export pathways and residence times of both MAB and SAB shelf water are examined. The importance of these large and variable export volumes to carbon budgets in the southern MAB and northern SAB is considered.