FY 1981

Circulation over the continental shelf of the southeastern Bering Sea

Kinder, T.H., and J.D. Schumacher

Chapter 5 in Eastern Bering Sea Shelf: Oceanography and Resources, D.W. Hood and J.A. Calder (eds.), Vol. 1, USDOC/NOAA/OMPA, 53–75 (1981)

Using extensive direct current measurements made during the period 1975-78, we describe flow over the southeastern Bering Sea shelf. Characteristics of the flow permit us to define three distinct regimes, nearly coincident with the hydrographic domains defined in the previous chapter. The coastal regime, inshore of the 50 m isobath, had a slow (1-5 cm/sec) counterclockwise mean current and occasional wind-driven pulses of a few days' duration. The middle regime, bounded by the 50 and 100 m isobaths, had insignificant (<1 cm/sec) mean flow but relatively stronger wind-driven pulses. The outer regime, between the 100 m isobath and shelf break ( ~ 170 m), had a 1-5 cm/sec westward mean and low-frequency events unrelated to local winds. Over the entire shelf most of the horizontal kinetic energy was tidal, varying from 60 percent in the outer regime to 90 percent in the coastal regime. About 80 percent of the tidal energy was semidiurnal. Mean flow over the shelf is well described qualitatively by dynamic topographies, and shallow current data from both coastal and outer regimes agree quantitatively as well. Two meteorological conditions that force the observed current pulses have been identified. In summer eastward-traveling low atmospheric pressure centers caused low-frequency pulses in the middle regime, and weaker pulses in the coastal regime. In winter, outbreaks of cold and dry continental air forced pulses within the coastal and middle regimes.