The North Atlantic shelfbreak current: an advective link for climate variability


OCCI Funded Project: 2006

Proposed Research

The North Atlantic shelfbreak front and jet are vitally important components of the coastal circulation in the northwest Atlantic, making up an extensive connected system that extends many thousands of kilometers, establishing an advective link between the subarctic and subtropical domains (Fig. 1). Through this advective pathway, the shelfbreak current transports high-latitude climate-driven variability equatorward. However, because the front acts as a barrier that inhibits cross-shelf exchange, it is not clear exactly how these signals are communicated to the interior of the Atlantic where they might have an impact on the larger climate system (e.g. the often cited scenario where the conveyor belt system is shut down by low salinity waters covering convection regions). Recent studies suggest that there are geographical regions along the path of the current where mass and freshwater are lost, however little direct evidence of these pathways exists. In the proposed study, I will investigate the role of the shelfbreak current in the propagation of climate signals, focusing on how and where such anomalies leave the coast to impact the North Atlantic. I will use a hydrographic climatology of the shelfbreak current that I have developed, spanning the full length of the current from Cape Farewell, Greenland to Cape Hatteras, North Carolina, supplemented by additional data from the offshore domain. The study has two specific goals: (1) construct a detailed steady-state description of freshwater pathways exiting the shelf region, looking in particular at the current branching that occurs at the Tail of the Grand Banks of Newfoundland, and (2) investigate the propagation of climate variability in the shelfbreak system, using the climatology to trace the evolution of anomalous freshwater pulses as they propagate along the coast in the North Atlantic, including their fate at the critical juncture at the Tail of the Grand Banks. The ultimate goal of this work is to develop sufficient understanding to be able to use the history of past events to predict the impact of future freshening events on the larger North Atlantic.