FY 1981

Tides of the eastern Bering Sea shelf

Pearson, C.A., H.O. Mofjeld, and R.B. Tripp

Chapter 8 in The Eastern Bering Sea Shelf: Oceanography and Resources, D. Hood and J.A. Calder (eds.), Vol. 1, USDOC/NOAA/OMPA, 111–130 (1981)

The acquisition of a substantial amount of pressure-gauge and current-meter data on the Bering Sea shelf has permitted a much more accurate description of the tides than has previously been possible. Cotidal charts are presented for the M₂ and, for the first time, the N₂, K₁, and O₁ constituents, and tidal current ellipse charts for M₂ and K₁. S₂, normally the second largest semidiurnal constituent, has not been included because it is anomalously small in the Bering Sea. The tide enters the Bering Sea through the central and western Aleutian Island passes and progresses as a free wave to the shelf. Largest tidal amplitudes are found over the southeastern shelf region, especially along the Alaska Peninsula and interior Bristol Bay. Each semidiurnal tide propagates as a Kelvin wave along the Alaska Peninsula but appears to be converted on reflection in interior Bristol Bay to a Sverdrup wave. A standing Sverdrup (Poincaré) wave resulting from cooscillation in Kuskokwim Bay is evident on the outer shelf. The semidiurnal tides are small in Norton Sound where there is an amphidrome. The diurnal tides, which can have only Kelvin wave dynamics, cooscillate between the deep basin and the shelf. Amphidromes are found between Nunivak Island and the Pribilof Islands, and west of Norton Sound. Throughout most of the shelf the tide is of the mixed, predominantly semidiurnal type; however, the diurnal tide dominates in Norton Sound. Tidal models by Sünderman (1977) (a vertically integrated M₂ model of the entire Bering Sea) and by Liu and Leendertse (1978, 1979) (a three-dimensional model of the southeastern shelf incorporating the diurnal and semidiurnal tides) are discussed. Good qualitative agreement is found between the models and observations.