Polar oceanography I: Arctic Ocean

Abstract

Oceanographic work in the Arctic seas the past four years has concentrated on the dynamics of the planetary boundary layer, meso‐scale events, regional problems (particularly on the shelves), and the connection with the North Atlantic (including the formation and outflow of deep water).A major U.S. effort in the Arctic during the present reporting period was the Arctic Ice Dynamics Joint Experiment (AIDJEX). While the main thrust of the work was in ice dynamics, a good deal of oceanography was accomplished, particularly in boundary layer flow. During the 1972 pilot study, the first simultaneous measurements were made of mean and turbulent velocity at several levels through a fully developed planetary boundary layer (McPhee and Smith, 1976). The turbulent structure corresponded closely to recent atmospheric planetary boundary layer models when scaled by U*, U*2, and U*/f for velocity, stress, and depth, where U* is the surface layer friction velocity and f is the Coriolis parameter. The general conceptual framework developed was used to interpret results of the year‐long 1975–76 AIDJEX main experiment. In particular, McPhee (1977) used a bulk transport model and measured winds to predict ice drift during the melt season, when stress gradients in the ice were small. The simulations reproduced the observed velocity and velocity gradient fields remarkably well, underscoring the idea that U*/f scaling is appropriate, rather than, say, a mixed‐layer slab approach. In a second paper, McPhee (1978b) refined the statistics of the ice drift/water stress couple to show that a model adapted from the atmospheric planetary boundary layer theory of Businger and Arya (1974) gave statistics that were indistinguishable from the AIDJEX observations. The model was consistent with a Rossby‐number similarity law for the ice drag. The observations preclude the type of drag one would obtain by assuming constant eddy viscosity for a mixed‐layer slab. Other studies of the stress field beneath the ice include that of Hunkins (1975), as well as a large number published in the AIDJEX Bulletin by a variety of investigators.