Boundary undercurrent and water mass changes in the Lincoln Sea

Abstract

Oceanographic measurements taken between 1989 and 1994 in the Lincoln Sea describe the currents and water mass structure along the continental slope of the Arctic Basin between the Canadian and Eurasian Basins. The measurements included periodic conductivity and temperature versus depth (CTD) profiles from ice camps, CTD cross sections normal to the slope, and year‐round current measurements. Analysis of this data describes the hydrographic structure of the waters over the continental slope and identifies some significant interannual variations. An undercurrent, confined to the continental slope, with a width of about 50 km and speeds of 5–9 cm s−1 is shown in geostrophic current cross sections. The presence of this easterly flow at depth is confirmed by current meter measurements, and its existence has also been observed in the Beaufort Sea and the Barents Sea [Aagaard, 1989]. The waters within this undercurrent exhibit temperature‐salinity (TS) characteristics similar to Canadian Basin waters, suggesting a boundary current system which is continuous along the continental slope north of Alaska and Canada. Significant interannual variations in temperature and salinity profiles may be related to variations in the large‐scale circulation of the Arctic. Examination of the upper pycnocline waters over the slope between 1991 and 1994 indicated a relative temperature maximum overlying a minimum, TS characteristics similar to waters attributed to Bering Sea origin found in the Canadian Basin. These characteristics were not seen, however, during 1989 and 1990, suggesting a recent increase in the transport of surface waters from the Canadian Basin into the Eurasian Basin.