Trends in Physical Properties at the Southern New England Shelf Break

• Published in: Journal of geophysical research. Oceans 2020-02, Vol.125 (2), p.n/a
• Main Authors: Harden, B. E., Gawarkiewicz, G. G., Infante, M.
• Format: Article
• Language: English
• Subjects: Capes (landforms); climate; Continental shelves; Density; Fisheries; Geophysics; Gulf Stream; Isobaths; Marine crustaceans; Meanders; New England; Nutrients; Oceanographic institutions; Oceans; Offshore; Physical properties; Reduction; Salinity; Salinity effects; Salinity sections; Shelf Break Jet; Shellfish; Slope water; Storms; Stratification; Surface temperature; Surface water; Temperature; temperature and salinity trends; Trends
• ISSN: 2169-9275; 2169-9291
• DOI: 10.1029/2019JC015784

We analyze 11 years (2003–2013) of repeat temperature and salinity sections from across the New England shelf break south of Cape Cod during early summer (June–July). The mean sections resolved the shelf break front which supports the Shelf Break Jet, a vital component of the regional circulation. Individual sections showed a great deal of variability associated with meanders in the shelf break front consistent with previous studies in the region. Over the 11 year record, the shelf region (inshore of the 100 m isobath) warmed by 0.26 °C yr −1, with the majority of this warming occurring shallower than 20 m (0.58 °C yr −1). The full‐depth trend agrees well with previous studies of shelf warming to the north and the south of our study region. The temperature and salinity of the offshore edge of the Cold Pool Water on the shelf did not change significantly during this period. The surface warming on the shelf resulted in a decrease in near‐surface density of 0.12 kg m −3 yr −1 and an increase in stratification between 10 and 15 m of 6.7×10−5 s −2 yr −1. Offshore of the shelf break, the Slope Water also warmed and became more saline by 0.21 °C yr −1 and 0.04 yr −1 respectively, resulting in a maximal reduction in density of 0.01 kg m −3 yr −1. In the Shelf Break Front, there is some evidence of freshening and a reduction in density, which may have resulted from an offshore shift in the Cold Pool but the statistical significance is small. Plain Language Summary The ocean is getting warmer along the coast of New England. This has already impacted major fisheries including lobster but may have larger implications for temperatures on land and the path and intensity of storms. However, we lack a full picture of these changes and what is driving them, mostly due to a limited supply of measurements in similar parts of the coastal ocean. Fortunately, a collaboration between the Woods Hole Oceanographic Institution and the Sea Education Association measured the ocean at exactly the same points in late June between 2003 and 2013 to the south of Cape Cod. We found that the surface ocean was getting hotter quickest by more than 5 °C over this decade. This has made the surface water more buoyant and will likely limit the amount of vital nutrients that can reach the surface. There was also warming and an increase in salinity deeper in the ocean, over the upper continental shelf, possibly due to an increased presence of Gulf Stream water. These warming trends are similar to t