FY 1982

On exchange of water between the Gulf of Alaska and the Bering Sea through Unimak Pass

Schumacher, J.D., C.A. Pearson, and J.E. Overland

J. Geophys. Res., 87(C8), doi: 10.1029/JC087iC08p05785, 5785–5795 (1982)

We present the first long-term current and bottom pressure observations from Unimak Pass, Alaska, and adjacent locations on the Gulf of Alaska and Bering Sea shelves. Vector mean current recorded between March and August 1980 was ~12 cm/s toward 284°T or onto the Bering Sea shelf, however, magnitude decreased from ~20 cm/s to ~6 cm/s between the first and second halves of the record. At shorter periods (3–10 days), current fluctuations in the pass were strongly coherent (K10.1029/JC087iC08p05785≤ 0.7) with the pressure difference measured along the axis of the pass, and this was coherent with geostrophic wind estimates. The results indicated that wind-induced sea level perturbation was the dominant forcing mechanism for fluctuations. Relations among current, bottom pressure, pressure difference, and geostrophic wind time series also showed that dynamic variation on the Gulf of Alaska shelf was primarily responsible for current fluctuations in the pass. Hydrographic data indicated that a baroclinic current existed along the Gulf of Alaska coast, and this flow became the long-term mean flow through the pass. We suggest that this feature was the extension of the Kenai Current. The historic supposition that water is transported from the Gulf of Alaska into the Bering Sea was verified; however, the waters are of coastal origin rather than from the Alaskan Stream.