Abstract
Using satellite altimetric sea surface height (ADT) data, we search for propagation of hydrographic anomalies along the Norwegian Atlantic Slope Current (NwASC) from the Svinøy section in the south to the Fram Strait in the north. Our analyses indicate that ADT anomalies, related to low-frequency temperature variations, propagate downstream with speeds of about 2 cm s. Notably, this speed is nearly an order of magnitude slower than the speed of the NwASC, which in agreement with previously estimated propagation speeds of hydrographic anomalies along the flow. A conceptual tracer advection model, consisting of a thin current core interacting with an adjacent slow moving reservoir, is introduced to examine temperature anomaly propagation along the NwASC. It is shown that shear dispersion effects, resulting from cross-stream eddy mixing and velocity shear, can qualitatively explain the observed delayed propagation of hydrographic anomalies: low-frequency temperature anomalies move downstream with an effective velocity that corresponds to a mean velocity across the entire Atlantic Water layer, rather than the speed of Norwegian Atlantic Slope Current.
Highlights
Heat transport associated with the poleward flow of Atlantic Water through the Nordic Seas plays a critical role for the climatic conditions in the Arctic Ocean, influencing the stratification and the sea ice cover (Rudels et al, 2005; Rudels, 2012; Carmack et al, 2015)
Observations show that temperature anomalies of the Atlantic Water in the Nordic Seas propagate poleward with speeds of a few cm s−1, and with a delay of a couple of years affect theArctic Ocean sea ice extent and hydrography (Polyakov et al, 2005; Årthun et al, 2012; Carmack et al, 2015)
A lagged correlation analysis of the Absolute Dynamic Topography (ADT) along the Norwegian Atlantic Slope Current (NwASC) (Fig. 3) resulted in a slanted pattern of elevated correlation that corresponds to a propagation speed of about 2 cm s−1
Summary
Heat transport associated with the poleward flow of Atlantic Water through the Nordic Seas plays a critical role for the climatic conditions in the Arctic Ocean, influencing the stratification and the sea ice cover (Rudels et al, 2005; Rudels, 2012; Carmack et al, 2015). Propagation of heat/salinity anomalies from the subpolar North Atlantic, across the Greenland–Scotland Ridge, and further through the Nordic Seas toward the Arctic Ocean is a robust observational feature found in numerous investigations, including analyses of hydrographic data (Furevik, 2001; Sundby and Drinkwater, 2007; Skagseth et al, 2008; Chafik et al, 2015; Yashayaev and Seidov, 2017), satellite-based SST data (Furevik, 2000; Chepurin and Carton, 2012) and surface drifters (Koszalka et al, 2013). Chepurin and Carton (2012) use lagged correlation analyses of satellite sea surface temperatures (SSTs) that trace propagation along a path from the North Atlantic, into and anti-clockwise around the Nordic Seas Along this path, they estimate a transit time from the Svinøy section to the Fram Strait of 3 years, corresponding to a speed of about 3 cm s−1.
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