Waters of the Makarov and Canada basins

Hydrographic measurements from the 1994 Arctic Ocean Section show how the Makarov and Canada basins of the Arctic Ocean are related, and demonstrate their oceanographic connections to the Eurasian Basin. The inflow into the Makarov Basin consists largely of well-ventilated water within a broad band of densities from a boundary flow over the Siberian end of the Lomonosov Ridge. The boundary flow contains a significant component of dense shelf water likely originating in the Barents, Kara, and Laptev Seas. Earlier ice camp data show that the Canada Basin is relatively more isolated from this ventilation source. In the Canada Basin shelf sources influenced by Bering Sea water appear to add cold waters with high silicate concentrations to the halocline and deeper. In 1994 the halocline silicate maximum over the central Makarov Basin was absent, evidence of the recent displacement of the upper (S∼ 33.1) halocline water from the Chukchi-East Siberian Sea region by water from the Eurasian Basin. Much of the Makarov Basin water in and below the halocline is in fact from the Eurasian Basin, with admixture of waters from the Canada Basin suggested by their higher silicate concentrations. Mid-depth eddies may transport anomalous properties into the central Arctic and create property gradients or fronts in mid-depth and deep waters. The complex topography of the Mendeleyev Ridge-Chukchi Plateau region also may assist spreading of water from the boundary into the interior. Atlantic layer characteristics in 1994 differed from previous general depictions. In particular the core temperatures at the Chukchi-Mendeleyev boundary were at least 0.2°C warmer on average than indicated in earlier work. The recent warming at intermediate depth has resulted from inflow of Atlantic waters that have been cooled relatively little during their transit of the Norwegian Sea.