A Swirl’s Impact on a Warming Shelf: An Investigation into the Mid Atlantic Bight’s Slope Water Gyre and its Influence on a Warming Continental Shelf

Abstract:

In 2008, there was a sudden warming of the North West Atlantic Shelf which propagated southward along the United States east coast. A dynamical shift at the Tail of the Grand Banks of Newfoundland appears to initiate this warming, with anomalies in the along-slope velocity and subsurface temperature propagating southwestward at a speed consistent with a slowdown of the Labrador Current . However, a region at the Mid Atlantic Bight, while strongly correlated with the fluctuations at the Tail of the Grand Banks, is delayed by about a year relative to the propagating signal . This indicates that a separate mechanism is at play in between Cape Hatteras and Cape Cod, impacting the rate at which the circulation influences this region. A cyclonic slope water gyre can easily be identified from sea surface height on the Mid Atlantic Bight, and we hypothesize that it may impact the shelf temperature fluctuations. Observations of this gyre’s perimeter indicate strong seasonality, averaging about 2800 km over a time span from 1993 to 2019. By looking at the trend in sea surface height of the outer most boundaries of the gyre, the strength of the gyre can be investigated. Preliminary figures indicate an increase in sea surface height over time with a step change in 2009. Understanding this second mechanism at play in the Mid Atlantic Bight will aid in predicting the region’s response to changes in the Gulf Stream, and overall continental shelf responses.