Varieties of shallow temperature maximum waters in the Western Canadian Basin of the Arctic Ocean

The properties and spreading pathways of shallow temperature maximum waters (STMs) in the western Canadian Basin are investigated using CTD and mooring data obtained in 1997-98 as part of the SHEBA (Surface Heat Budget of the Arctic Ocean) drift experiment and available historical data. Three distinct varieties of STM are recognized on the basis of salinity range: (1) Surface Mixed Layer Water (SMLW) with S < 30 psu; (2) Eastern Chukchi Summer Water (ECSW) with 31 < S < 32 psu; and (3) Western Chukchi Summer Water (WCSW) with S > 32 psu. These STMs carry sufficient heat within the Upper layers of the ocean to significantly affect the rates of ice cover and decay. For example, during the winter of 1997-98 anomalously warm STM ( > 0 degreesC) originating from ECSW was observed to spread northwards along the Northwind Ridge and Chukchi Plateau, where the maximum reduction of the ice covers was subsequently observed in late summer, 1998 [Maslanik et al., 1999]. Regional climate variability and ice cover in the western Canadian Basin are thus affected not only by anomalous atmospheric circulation patterns, but also by the circulation of upper ocean water masses.