Sound‐speed structure of the Arctic Ocean and the Greenland Sea Marginal Ice Zone

Abstract

Within the central ice‐covered Arctic Basin, well away from marginal influences, the vertical sound‐speed profile can be characterized by four positive sound‐speed gradient layers. These layers (and the approximate gradients) are a surface mixed layer extending to a depth of a few tens of meters (∼0.016/s); a layer from the base of the mixed layer to the depth (200–500 m) of the temperature maximum in the Atlantic water (∼ 0.080/s); a layer from the temperature maximum to the bottom of the Atlantic water at about 1000 m (∼0.010/s); and the deep water extending to the ocean bottom (∼0.016/s). The consistent and notable differences evident in the general sound‐speed structure of the Canadian and Eurasian Basins can be related to the large scale Arctic Ocean circulation. Profile‐to‐profile variability and the occurrence of small vertical scale sound‐speed features, such as relative minima/maxima and steplike structures, are significantly higher in the Eurasian Basin than in the Canadian Basin. The sound‐speed distribution within the Greenland Sea Marginal Ice Zone is dominated by the presence of a strong oceanographic front, the East Greenland Polar Front, which marks the boundary between the cool, fresh Polar water exiting the Arctic Ocean and the adjoining warmer, more saline Atlantic water. Because of this strong ocean front, profile‐to‐profile sound‐speed variability in the Marginal Ice Zone is high over short distances and times. The complex sound‐speed structure and its high variability result from various interactions between the two water masses which can take the form of eddies, intrusive layers, and steplike features.