Modification of water masses in the Barents Sea and its coupling to ice dynamics: a model study

Abstract

The physical and biological environment of the Barents Sea is characterised by large variability on a wide range of scales. Results from a numerical ocean model, SINMOD, are presented showing that the physical variability is partly forced by changes in annual net ice import. The mean contribution from ice import in the simulation period is about 40% of the total amount of ice melted each year. The annual ice import into the Barents Sea varies between 143 and 1,236 km 3 , and this causes a substantial variability in the amount of annual ice melt in the Barents Sea. This in turn impacts the freshwater content. The simulated freshwater contribution from ice is 0.02 Sv on average and 0.04 Sv at maximum. When mixed into a mean net Atlantic Water (AW) inflow of 1.1 Sv with a salinity of 35.1, this freshwater addition decreases the salinity of the modified AW to 34.4 and 33.9 for the mean and maximum freshwater fluxes, respectively. Ice import may thus be important for the Barents Sea production of Arctic Ocean halocline water which has salinity of about 34.5. The changes in the ice melt the following summer due to ice import also affect the formation of dense water in the Barents Sea by changing stratification, altering the vertical mixing rates and affecting heat loss from the warm AW. The model results thus indicate that ice import from the Arctic has a great impact on water mass modification in the Barents Sea which in turn impacts the ventilation of the Arctic Ocean.

Dense water formation and circulation in the Barents Sea

“…The CDW variability on Great Bank is thus more affected by ice import from the north than regional climate indicators. Ice import and the associated freshwater input have been found by earlier studies to have a large influence on salinity anomalies in the Barents Sea (Maus, 2003;Ellingsen et al, 2009), and to contribute to the stronger stratification in the northern Barents Sea which is important to water mass transformations (Steele et al, 1995;Harms, 1997). The most dominant signal in the the initial salinity on Great Bank is the long term increase over almost the entire simulation period (Fig.…”

“…Midttun, 1985;Rudels and Friedrich, 2000;Schauer et al, 2002), and potential sources of variability in dense water characteristics have been identified (e.g. Rudels, 1987;Cavalieri and Martin, 1994;Schauer, 1995;Harms, 1997;Backhaus et al, 1997;Schauer et al, 2002;Ellingsen et al, 2009). The surface salinity before the freezing season has been found to be important, but the factors controlling the salinity depend on the region being investigated.…”

“…For the Novaya Zemlya Bank, freshwater carried with the Norwegian/Novaya Zemlya Coastal Current has been suggested (Rudels, 1987;Schauer, 1995;Schauer et al, 2002). Harms (1997) argued that ice freezing/melting is more important than the freshwater runoff, while Ellingsen et al (2009) found that ice import through the northern boundaries is of major importance to dense water characteristics. Water column stability is another source of variability (Backhaus et al, 1997;Harms, 1997;Maus, 2003;Skogseth et al, 2004).…”

The Barents Sea frontal zones and water masses variability (1980–2011)

“…9b and c). Such biases are not unusual for models and the causes of these flaws are numerous (see for example Sundfjord et al, 2007or Ellingsen et al, 2009. Despite these imperfections, the model correctly reproduces the observed BS seasonal cycle (not shown) and succeeds in capturing the interannual variability.…”

Modified Halocline Water over the Laptev Sea Continental Margin: Historical Data Analysis

“…The reduced SIE indicates more open water and therefore the possibility for more brine release and increasing salinity due to more intensive formation of new sea ice. In periods when wind exports large amounts of ice out of the Barents Sea, the salinity of the water increases, and vice versa (Ellingsen et al 2009). The 5-yr lag corresponds to an ;5-yr transit time for the Atlantic-origin water between the Barents and Laptev Seas on the basis of tracer analysis (Frank et al 1998;Smith et al 2011).…”