Trends in Physical Properties at the Southern New England Shelf Break

B E Harden,M Infante,G G Gawarkiewicz

doi:10.1029/2019jc015784

B E Harden, M Infante + Show 1 more

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https://doi.org/10.1029/2019jc015784

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Abstract

AbstractWe 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 , with the majority of this warming occurring shallower than 20 m (0.58 °C yr ). 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 yr and an increase in stratification between 10 and 15 m of s yr . Offshore of the shelf break, the Slope Water also warmed and became more saline by 0.21 °C yr and 0.04 yr respectively, resulting in a maximal reduction in density of 0.01 kg m yr . 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.

Highlights

The northeastern continental shelf of the United States, comprising the Gulf of Maine and the southern New England shelf, is among the most rapidly warming regions in the world oceans (Mills et al, 2013; Pershing et al, 2015)
We have examined 11 years of repeat cross-shelf hydrographic sections across the Shelf Break Front south of New England to determine trends in water mass properties
Individual sections show considerable synoptic variability including the influence of shelf break frontal meandering, but the mean and standard deviation fields are consistent with prior climatological studies

Summary

Introduction

The northeastern continental shelf of the United States, comprising the Gulf of Maine and the southern New England shelf, is among the most rapidly warming regions in the world oceans (Mills et al, 2013; Pershing et al, 2015) This has impacted the continental shelf ecosystem (Record et al, 2019; Walsh et al, 2015) with important economic consequences for the commercial fishing industry. Despite increasing public and academic awareness of this issue, we lack a full understanding of how this region is changing due, in part, to the limited number of data sets with repeat hydrographic stations at the same location and time of year for an extended period of time Those that do exist are largely limited to surface or subsurface temperature measurements and have not been able to account for changing salinity and density throughout the water column.

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