Renewal and circulation of intermediate waters in the Canadian Basin observed on the SCICEX 96 cruise

During the summer of 1996 the nuclear submarine USS Pogy occupied a line of stations extending through the middle of the Canadian Basin between about 88° N, 44° W (Lomonosov Ridge) and about 78° N, 144° W (center of the Canada Basin). CTD/Niskin bottle casts extending to 1600 m were carried out at eight stations, providing the first high-quality temperature, salinity, CFC, tritium, and ³He data obtained from this region, although XCTD data had previously been collected in this region. These data, along with data from stations at the basin boundary to the south and west, reveal the presence of well-ventilated intermediate water beneath the halocline in the center of the Canada Basin, indicating renewal times of the order of 1-2 decades. The least ventilated intermediate water was observed at the northern end of the Canada Basin along the southern flank of the Alpha Ridge. Intermediate water is derived from the Atlantic Ocean and enters the Arctic Ocean through Fram Strait and the Barents Sea. It flows around the Arctic basins in boundary currents and splits in the eastern Amundsen Basin with one branch crossing the Lomonosov Ridge and flowing along the East Siberian continental slope and the other flowing along the Eurasian flank of the Lomonosov Ridge. From the 1996 Scientific Ice Expedition (SCICEX 96) observations we conclude that the branch that flows along the East Siberian continental slope transports this water to the Chukchi Rise, where it apparently enters the central Canada Basin with some flow continuing along the boundary to the southern Canada Basin. The Fram Strait Branch Water mixes extensively with waters from the Canadian Basin during its transit along the East Siberian continental slope, being diluted by a factor of about 5 by the time it reaches the central Canada Basin. The Barents Sea Branch Water does not undergo such extensive mixing and is diluted by a factor of only about 2 when it reaches the central Canada Basin.