In most of the western Arctic (blue profiles in Figure 2), below the mixed layer are the Pacific Waters (PW). In regions of ice-cover, both profiles typically have a thin (~5-10m thick) surface mixed layer, although in (increasingly common) ice-free regions, wind-driven mixed layers maybe more than twice as deep (Rainville et al. The Arctic water column (Figure 2) can be considered as a stacking of mostly non-interacting layers, and categorized into typical western Arctic (Canadian Basin) or eastern Arctic (Eurasian Basin) profiles (McLaughlin et al. 2008).Īll these flow estimates are approximate, with uncertainties typically about 25%. 2001), or via the complex channels of the Canadian Archipelago (~ 1-2Sv, Melling et al. Outflows from the Arctic are all to the Atlantic, via either the western side of the Fram Strait (~ 9Sv, Fahrbach, et al. This freshening can be quantified as an equivalent volume of pure freshwater (e.g., Aagaard and Carmack 1989)). (Since the Pacific inflow is fresher than the mean salinity of the Arctic Ocean, it freshens the Arctic. However, together they contribute roughly two-thirds of the freshwater entering the Arctic, the remaining third coming from the Pacific inflow (Aagaard and Carmack 1989, Serreze et al. The other inputs to the Arctic are volumetrically small: Eurasian and Russian rivers (~ 0.1Sv) and precipitation minus evaporation (~ 0.06Sv). The Barents Sea inflow is around 1Sv in summer and 3Sv in winter, and has been substantially modified during transit of the Barents Sea (Schauer et al. 2001), although complex recirculations in the strait return around half of that immediately to the south (Rudels et al.
The Fram Strait inflow is about 7Sv (also seasonally varying) (Fahrbach et al. For discussion and references, see Beszczynska-Möller et al. The Atlantic inflow enters through both the Fram Strait (~ 350km wide, ~ 2700m deep) and the Barents Sea (mostly via St Anna Trough, ~ 200km wide, ~ 600m deep). The Atlantic inflow is generally saltier (greater than 34 psu), warmer (greater than 0✬), and about 10 times greater in volume than the Pacific inflow. Numerically, values are equivalent to parts salt per thousand parts water.) (The dimensionless unit ‘psu' is used in this article to indicate salinities measured on the Practical Salinity Scale (Lewis 1980). Properties of this inflow vary significantly seasonally, from about 0.4Sv, -1.9✬, and 33psu in winter to about 1.2Sv, greater than 2 ✬, and less than 31.9psu in summer (Woodgate et al. The only Pacific-Arctic gateway is the narrow (~ 85km wide), shallow (~ 50m deep) Bering Strait, through which about 0.8Sv (1Sv=10 6m 3/s) of water enters the Arctic. The Arctic Ocean plays two roles in the global ocean circulation - it provides an oceanic pathway between the Pacific and the Atlantic oceans and it also takes an Atlantic input, modifies it, and returns it to the Atlantic (Rudels and Friedrich 2000).
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