Arctic layer salinity controls heat loss from deep Atlantic layer in seasonally ice‐covered areas of the Barents Sea

Abstract

In the seasonally ice‐covered northern Barents Sea an intermediate layer of cold and relatively fresh Arctic Water at ~25–110 m depth isolates the sea surface and ice cover from a layer of warm and saline Atlantic Water below, a situation that resembles the cold halocline layer in the Eurasian Basin. The upward heat flux from the Atlantic layer is of major concern. What causes variations in the heat flux and how is the Arctic layer maintained? Using observations, we found that interannual variability in Arctic layer salinity determines the heat flux from the Atlantic layer through its control of stratification and vertical mixing. A relatively fresh Arctic layer effectively suppresses the upward heat flux, while a more saline Arctic layer enhances the heat flux. The corresponding upward salt flux causes a positive feedback. The Arctic layer salinity and the water column structures have been remarkably stable during 1970–2011.

Food‐web structure varies along environmental gradients in a high‐latitude marine ecosystem

“…1a). The southwest region of the Barents Sea is strongly influenced by the inflow of relatively warm and saline Atlantic water (temperature > 3°C; salinity > 35.0 psu) (Ingvaldsen et al 2002), whereas the northern Barents Sea is a typical stratified Arctic environment with colder and fresher Arctic water masses occupying the upper part of the water column (temperature < 0°C; salinity 34.0 to 34.7 psu), above a deep layer of modified Atlantic water (Lind andIngvaldsen 2012, Lind et al 2016) ( Fig. 1c; Supplementary material Appendix 1 Fig.…”

“…Bottom depth was registered by depth sensors for each bottom-trawl station. Following an approach by Lind et al (2016), ocean temperature and salinity observations from conductivity-temperature-depth profiles, sampled during the joint Norwegian-Russian ecosystem surveys in August and September during 2004-2007, were interpolated on horizontal grids with a high vertical resolution, see Supplementary material Appendix 1 for details. Mean temperature and salinity, and corresponding standard deviations, were estimated for the whole water column in each polygon from the gridded fields (Supplementary material Appendix 1 Fig.…”

“…Nonetheless, information on changes that have occurred in recent decades due to warming and analyses that substitute space-for-time can provide some indication of how food webs may look like in a warmer Barents Sea. The northern part of the Barents Sea is among the regions in the Arctic undergoing some of the most extensive and rapid environmental changes driven by global warming with large reductions in the sea ice cover accompanied by substantial warming of the entire water column (Lind and Ingvaldsen 2012, Carmack et al 2015, Lind et al 2016). This has led to a rapid retraction of the marginal ice zone and a prolonged openwater season (Dalpadado et al 2014, Carmack et al 2015.…”

Sea-ice thickness from field measurements in the northwestern Barents Sea

“…The ice thickness values of 0.3-0.4 m produced by the FDD model simulation begun from an ice free state on 17 February are between the two modes, supporting our hypothesis that ice thermodynamic growth is the main contributor to the ice formation during the period between 17 February and 26 March. There is also evidence in photographs ( Figure 9) taken during the HEM flights of rafting of newly formed thin ice resulting in thickness of around 0.2-0.4 m. The typical situation in the northern Barents Sea is for a layer of cold and fresh Arctic Water to overlie an Atlantic core, this limits the heat loss from the Atlantic water below, maintaining conditions favorable for ice production (Lind et al, 2016). That rapid thermodynamic growth is Journal of Geophysical Research: Oceans 10.1002/2016JC012199 possible in this region has previously been shown by Nghiem et al [2005] who documented rapid ice formation over the location of a deep elongated channel known to carry cold Arctic water which connects the Franz Josef-Victoria Trough to the Hinlopen Basin between Svalbard and Franz Josef Land.…”

“…The Barents Sea is one of the marginal shelf seas of the Arctic Ocean, which surround the Arctic Basin. Located in the European sector of the Arctic (Figure 1a), it is influenced by both Atlantic water and Arctic water [Nghiem et al, 2005;Smedsrud et al, 2013;Onarheim et al, 2015;Lind et al, 2016]. Most of the sea ice in the Barents Sea is formed locally, with a fraction imported from the Arctic Basin through the straits between Svalbard and Novaya Zemlya [Vinje and Kvambekk, 1991;Vinje, 2001;Kern et al, 2006;Kwok, 2009;Pavlova et al, 2014].…”