Dynamics of the Direct Intrusion of Gulf Stream Ring Water onto the Mid-Atlantic Bight Continental Shelf

Onshore intrusions of offshore waters onto the Mid-Atlantic Bight continental shelf can greatly affect shelf circulation, biogeochemistry and fisheries. Previous studies have concentrated on onshore intrusions of the slope water that sits between the shelf and the offshore Gulf Stream. This study presents a direct intrusion of Gulf Stream warm-core ring water onto the shelf representing a previously unknown exchange process at the shelfbreak. Impingement of warm-core rings at the shelfbreak generates along-isobath intrusions of the ring water that grow like Pinocchio’s nose, extending hundreds of kilometers to the southwest. Combining satellite and Ocean Observatory Initiative Pioneer Array glider data and idealized numerical simulations, we provide a dynamical explanation of the ring-water onshore intrusion. It results from topographically induced vorticity variation of the ring water, rather than from entrainment of the shelfbreak frontal jet. This intrusion of the Gulf Stream ring water has important biogeochemical implications. It could facilitate migration of marine species across the shelfbreak barrier and transport low-nutrient surface Gulf Stream ring water to the otherwise productive shelfbreak region.