Interannual surface salinity in Northwest Atlantic shelf

Type Article
Date 2017-05
Language English
Author(s) Grodsky Semyon A.1, Reul NicolasORCID2, Chapron BertrandORCID2, Carton James A.1, Bryan Frank O.3
Affiliation(s) 1 : Univ Maryland, Dept Atmospher & Ocean Sci, College Pk, MD 20742 USA.
2 : Inst Francais Rech & Exploitat Mer, Plouzane, France.
3 : Natl Ctr Atmospher Res, Climate & Global Dynam Lab, POB 3000, Boulder, CO 80307 USA.
Source Journal Of Geophysical Research-oceans (2169-9275) (Amer Geophysical Union), 2017-05 , Vol. 122 , N. 5 , P. 3638-3659
DOI 10.1002/2016JC012580
WOS© Times Cited 24
Keyword(s) salinity, interannual, satellite
Abstract Sea surface salinity (SSS) from the Aquarius and SMOS satellite missions displays a steady increase of ~1psu over the entire northwestern Atlantic shelf south of Nova Scotia during the 2011-2015. Put in the context of longer ocean profile data the results suggest that mixed layer salinity and temperature north of the Gulf Stream experience positively correlated shelf-wide interannual oscillations (1psu/2degC). Salty and warm events occur coincident with anomalous easterly-southeasterly winds and Ekman transport counteracting the mean southwestward shelf currents. They are coincident with the weakening of both branches of the Scotian Shelf Current (SSC), but only moderately correlate with shifts of the Gulf Stream North Wall. This suggests that salt advection by anomalous SSC acting on the mean salinity gradient is the primary driver regulating the transport of fresh/cold water from high latitudes. The advection mechanism imposes a connectedness of the larger-scale interannual variability in this region and its tie to atmospheric oscillations.
In the second part, an analysis of 15-year long numerical simulations is presented which show 8 interannual salinity oscillations (positive and negative). Six of these are driven by the horizontal advection by slow varying currents (>2 months), while 2 events are driven by the horizontal eddy advection (<2 months). In line with observations, salt/warm model events correspond to anomalously weak SSC, correlate with southeasterly wind anomaly, and confirm that interannual horizontal salt advection drives the interannual salinity. Indeed, vertical exchanges provide a negative feedback, while interannual horizontal diffusion and the net surface salt flux anomalies are small.
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