ON THE WATER EXCHANGE THROUGH BERING STRAIT1

Abstract

A critique of current observations from Bering Strait through 1960 elucidates the gross features of the flow. There is no substantiating evidence for a net southerly flow ever occurring through Bering Strait into the Bering Sea in summer, although the current may on occasion be southerly near Cape Dezhneva and Cape Prince of Wales.During 5–7 August 1964, the most intensive survey to date of the oceanographic conditions and currents was made from the USCGC Northwind. Hydrographic conditions and currents in 1964 were typical of Bering Strait in summer. In the eastern channel of the strait, there was a pycnocline at 10–15 m, which was also a region of velocity shear; the surface water layer speeds were typically 50–100 cm/sec, and the lower layer speeds less than 50 cm/sec. While speeds in the western channel were more uniform, they varied widely with time (20–70 cm/sec). The northward transport calculated from the Northwind data was 1.4 × 106 m3/sec, with about one‐half flowing through each channel.At least three types of speed fluctuations may be observed in Bering Strait: 1) short‐term irregular fluctuations of 10–15 cm/see, probably related to turbulence; 2) regular fluctuations of as much as 50% of the mean speed, occurring at all depths and having a period of 12–13 hr (tidal or inertial); and 3) long‐term fluctuations of as much as 100%, probably associated with major changes in the wind regime, the atmospheric pressure distribution over the Bering or Chukchi seas,or both.The accelerations would give rise to corresponding fluctuations in transport. In addition, a seasonal variation in transport has been reported, showing the flow in winter to be approximately one‐fourth that in summer, but this effect is poorly documented.A mathematical analysis of the flow includes a balance among the pressure gradients in the direction of flow, frictional stresses in the horizontal plane, and the local and nonlinear accelerations. The calculated sea surface slope is about 2.6 × 10−6 down to the north. This surface slope is the primary driving force of the northerly flow and can probably be modified only by major variations in atmospheric conditions.