Zhenxia Long and Will Perrie
Fisheries & Oceans Canada, Bedford Institute of Oceanography, Dartmouth, NS, Canada
1. Introduction
Warm saline Atlantic water enters the Barents Sea mainly through the Barents Sea Opening, keeps the southern Barents Sea largely ice free and increases air-sea interactions. In the northern Barents Sea, modified Atlantic water enters Nansen Basin through the Victoria Channel and the St. Anna Trough. Recent studies suggest that the inflow from the St. Anna Trough plays an important role in the heat balance in the central Arctic Ocean (Long and Perrie 2015).
2. Model description and experiment design
A coupled ice-ocean model (CIOM) was implemented in the Arctic Ocean, based on the Princeton ocean model (POM) and a multi-category ice Hibler model (Figure 1a). The simulations were driven by the surface fields from CRCM (the Canadian Regional Climate Model) simulations under A1B scenario from 1979 to 2099. The focus of our analyses is the ice-ocean simulations of the Barents Sea (Figure 1b).
3. Impacts of climate change in the Barents Sea
The changes in the storm track density in the Barents Sea are significantly correlated with the water volume transport through the Barents Sea Opening (Figure 1c). The maximum increases in the storm activity in the Barents Sea occur in 2000-2019, and the increases are relatively weak thereafter. Correspondingly, the simulated water volume transport through the Barents Sea Opening increases from 2.3 Sv in the 1980s to 2.7 Sv in the 2020s, but decreases after the 2030s, and there is no significant trend (Figure 1d). The associated ocean heat transport has a similar change, but shows significant multidecadal variability. The average heat transport after the 2030s is about 65 TW, which is about 10 TW higher than the average during 1980-2000 (Figure 1e).
The average ocean temperature in the northern Barents Sea decreases from ~-0.2oC in the 2010s to ~ -0.5oC in the 2030s, and there is no significant change thereafter (Figure 1f). For example, the temperature at 80m is about -1oC to -0oC in 1980-1999, but slowly decreases after 2000-2019, and the decrease reaches -1oC in the northwestern Barents Sea by the end of the century, in 2080-2099. In the southern Barents Sea, the average ocean temperature tends to increase from the 1980s to the 2090s. The average temperature increases from about 0oC in the 2000s to about 1oC in the 2090s (Figure 1g). Meanwhile, the warm water at 80m is limited to coastal areas during 1980-1999, but slowly expands northeastward, and dominates the southern Barents Sea in 2080-2099. The maximum increase in ocean temperature is about 3oC in 2080-2090.
The temperature decrease in the northern Barents Sea from the 2010s to the 2030s is mainly associated with the increased surface heat flux (Figure 1h). Under the climate change scenario, the average surface heat flux increases from 15 TW in 2000s to about 30 TW in the 2090s. However, the solar radiation and lateral heat transport tend to increase the ocean temperature. The average solar radiation gradually increases from about 10TW in the 2000s to about 20 TW in the 2090s. In addition, the increase in the lateral heat transport is relatively weak and increases from about 5TW in the 2000s to about 10TW in the 2090s. Therefore, the changes in solar radiation and lateral heat transport tend to partly offset the impacts of the enhanced surface heat flux. Correspondingly, the average ocean temperature decreases from the 2000s to the 2040s, and there is no significant trend from the 2040s to the 2090s.
By comparison, in the southern Barents Sea, the increased lateral heat transport and solar radiation play important roles in the ocean temperature increases (Figure 1i). Under the A1B scenario, the solar radiation increases from about 20TW in the 2000s to about 50TW in the 2090s. Meanwhile, the lateral heat transport increases from 40TW to about 60TW in the 2020s, but there is no significant trend thereafter. Similar to the changes in the northern Barents Sea, the surface heat flux increases from about 60TW in the 2000s to about 100TW in the 2090s, which partly offsets the impacts resulting from the increased lateral advection and solar radiation, and the net heat flux tends to increase ocean temperature.
4. Conclusions
Under the A1B scenario, there is a decreasing trend in ice cover in the Barents Sea. While the reduced albedo associated with the ice loss significantly increases the solar radiation absorbed by the ocean, the ice loss increases the ocean heat loss through the enhanced turbulent heat fluxes and longwave radiation. In addition, the changes in the arctic storm activity play an important role in the increased lateral heat transport through the Barents Sea Opening.
The changes of the ocean temperature in the southern Barents Sea show a different pattern from that in the northern Barents Sea. In the southern Barents Sea, the average ocean temperature tends to increase under the A1B scenario, due to the increased lateral heat transport and solar radiation. Although there is an increase in the heat loss through the turbulent heat flux, the net impacts of the heat balance tend to increase the ocean temperature. However, in the northern Barents Sea, the heat loss through the turbulent heat flux and longwave radiation is dominant from about the1980s to 2030s, and the average ocean temperature decreases from ~-0.2oC in the 2010s to ~-0.6oC in the 2040s, but stabilizes thereafter.
References
Long, Z. and Perrie, W., 2015: Scenario changes of Atlantic water in the Arctic Ocean. J. Clim., 28, 5523-5548, doi: http://dx.doi.org/10.1175/JCLI-D-14-00522.1
Long, Z. and Perrie, W., 2017: Changes in ocean temperature in the Barents Sea in the twenty-first century. J. Clim., 30, 5901-5921, doi: http://dx.doi.org/10.1175/JCLI-D-16-0415.1
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