Geochemical and physical water mass properties and halocarbon ventilation in the Southern Canadian Basin of the Arctic Ocean
Date
1996
Authors
McLaughlin, Fiona Ann
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Abstract
Temperature, salinity, nutrients, oxygen, and halocarbon data collected in the Arctic Ocean reveal a frontal structure previously unrecognized in the hydrography of the Canadian Basin. Samples were collected in 1993 on a 1300-km section extending from the Beaufort Sea in the Canada Basin to the East Siberian Sea in the Makarov Basin and reveal a lateral boundary between water masses of Atlantic and Pacific origin. The term water mass assembly is introduced to describe the basic arrangement or vertical stacking of water masses found in the Arctic Ocean, recognizing that water mass components within each assembly may differ from basin to basin. Because the presence or absence of Pacific origin water is a key characteristic distinguishing the two assemblies (EA and WA), the water mass boundary between the two assemblies is referred to as the Atlantic/Pacific front.
Earlier research indicated that water masses in the Arctic Ocean were separated by a front located above the Lomonosov Ridge. Although all stations from the Canada Basin display classic WA assembly characteristics, the Makarov Basin station shows EA assembly characteristics in the upper and Atlantic layers and a WA assembly deep layer. This suggests a relocation in the position of the Atlantic/Pacific boundary away from the Lomonosov Ridge. Further, data show the transition region between the Atlantic and deep layers is fresher in the Makarov Basin than corresponding water in either the Canada or Eurasian basins, implying a source of cold, low-salinity water, perhaps from Eurasian shelves.
The front separating these two assemblies now lies above the Mendeleyev Ridge and is marked by large lateral gradients in all measured properties. In particular, the penetration of anthropogenic halocarbons is 2 to 3 times deeper and the apparent ages are younger in the Makarov Basin than in the Canada Basin, implying enhanced rates of ventilation and more vigorous circulation.