The Inter-annual Variability In The Fluxes Through Main Straits In The Arctic Ocean

Fram Strait, Barents Sea Opening, Bering Strait and Davis Strait almost closearound the Arctic Ocean. Warm and salty Atlantic water enters into the Arctic Oceanthrough the first2channels and forms the lower Atlantic Layer in the Canada Basinand Eurasian Basin. So the volume and heat fluxes through Fram Strait and BarentsSea Opening are important to the thermal-dynamic process in the Arctic Ocean. At thesame time, cold and fresh polar surface water exports into the NorthAtlantic along thewest side of Fram Strait and Davis Strait which can influence local air-sea interaction,upper ocean stratification, the strength of thermohaline circulation and even theglobal climate. In the Pacific sector, Pacific Water flows into Canada Basin throughBering Strait as a freshwater source to maintain the upper halocline layer of the ArcticOcean. In one word, the inter-annual variability in the volume, heat and freshwaterfluxes through the4channels has great significance to water masses distribution,circulation etc. in the Arctic Ocean.In this paper, SODA (Simple Ocean Data Assimilation2.0.2) is applied into thecalculation of the fluxes through the4straits after proving its reliability. It is showedthat the inter-annual variability in these fluxes has more or less connections with seasurface height, Ekman transport and even the large scale atmospheric circulation suchasAO and NAO.In Fram Strait and Barents Sea Opening, Atlantic inflow reaches its annualmaximum in winter. The long-term mean volume, heat fluxes in the2straits are3.6Sv,48.7Tw and2.3Sv,55Tw respectively. The inter-annual variability in the heat flux iscontrolled by the velocity and is related to the NAO index positively. When NAO isstronger, warmer Atlantic inflow through Barents Sea Opening will be strengthenedby eastward Ekman transport anomaly. Meanwhile, the Norwegian Atlantic Currentbring warmer Atlantic water into Fram Strait through West Spitsbergen Current in thenext winter. The annual maximum for both Fram and Davis Strait freshwater exports happens inwinter with their long-term mean volume, freshwater fluxes about-2.54Sv,-88.9mSvand-3.74Sv,-180mSv respectively. In addition, the total freshwater export throughthe2straits has a negative correlation with winter AO index. During positive AOperiods, north wind in Fram Strait is stronger which makes on-shore Ekman transportanomaly and rise sea surface height (SSH) there. As a result,the East GreenlandCurrent will be strengthened because of the SSH gradient. Meanwhile, on-shoreEkman transport anomaly in the southern Beaufort Sea releases large quantity offreshwater, which is previously stored in Beaufort Gyre, through Canadian ArcticArchipelago, then into Baffin Bay and finally to be exported through Davis Strait. Allabove would explain the relationship between AO and the freshwater export from theArctic Ocean to some extent in the inter-annual scale.The Pacific inflow reaches its annual maximal volume flux in summer with thelong-term mean value equals to1.1Sv. The barotropic geostrophic velocity is incharge of its inter-annual variability and could be effected by summer sea levelpressure’s variation. When the first EOF mode of summer SLP variation turns topositive, both the Arctic High and the Aleutian Low is strengthened. In the north, theArctic High converges Ekman transport which would reduce the SSH along northcoast of Siberian and Alaska by either larger off-shore transport or strongerup-welling. While in the Bering Sea lower SLP transports more water eastward ontothe shelf southeast of the strait and raise SSH there. Finally the SSH pattern inducedby wind will enhance a northward Pacific inflow through Bering Strait by geostrophicadjustment.