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October 27, 2003
Seattle, Washington, USA

Observations from the Canada Basin: 1997-2003

Fiona A. McLaughlin¹, Eddy C. Carmack², Koji Shimada³, Motoyo Itoh⁴, Shigeto Nishino^5
1Fisheries and Oceans Canada, Institute of Ocean Sciences, 9860 W. Saanich Road, Sidney , BC, V8L 4B2, Canada, Phone 250-363-6527, Fax 250-363-6807, mclaughlinf@pac.dfo-mpo.gc.ca
²Institute of Ocean Sciences, Department of Fisheries and Oceans Canada, 9860 West Saanich Road, Sidney, BC, V8L 4B2, Canada, Phone 250-363-6585, Fax 250-363-6746, carmacke@dfo-mpo.gc.ca
³JAMSTEC, 2-15 Natsushima, Yokosuka, Kanagawa, 237-0061, Japan, Phone 81-46-867-3891, Fax 81-46-865-3202, shimadak@jamstec.go.jp
⁴Ocean Research Department, Japan Marine Science and Technology Center, 2-15, Natsushima, Yokosuka, 237-0061, Japan, Phone 81-46-867-9488, Fax 81-42-867-9455, motoyo@jamstec.go.jp
⁵Ocean Research Department, Japan Marine Science and Technology Center, 2-15, Natsushima, Yokosuka, 237-0061, Japan, Phone 81-46-867-9487, Fax 81-46-867-9455, nishinos@jamstec.go.jp

Canada Basin waters are in transition, responding to the effects of upstream change in atmospheric and oceanic circulation. The Canada Basin is unique in that it receives inflow from the Pacific Ocean, via the Bering/Chukchi Sea, and the Atlantic Ocean, which enters from the Makarov Basin via Fram Strait and the Barents Sea and the Nansen and Amundsen Basins. Observations made during SHEBA/JOIS in 1997-98 and on a cross-basin JWACS surveys in 2002 and 2003 showed that Canada Basin waters, and in particular the composition of the halocline, can no longer be viewed as laterally homogeneous and in steady state.

In 1997-98 the halocline was thinner over the Mendeleyev Abyssal Plain and northern Chukchi Plateau. Here, Pacific-origin upper and middle halocline waters occupied the upper 80 m of the water column and underlying Atlantic-origin lower halocline waters were fresher, colder and much more ventilated than observed in the past. These new observations of a sub-surface oxygen maximum suggest that outflow from the East Siberian Sea now supplies the Canada Basin lower halocline. East of the Northwind Ridge the halocline was thicker and appeared relatively unchanged.

Comparisons will be made with data collected in 2002 and 2003. Nutrients, temperature, and oxygen are used to identify spreading pathways of Pacific and Atlantic-origin waters. Time-series data follow the advance of warmer Atlantic-origin waters over the Chukchi Gap and into the southern Canada Basin, signalling the arrival of warm-anomaly Fram Strait Branch waters, first observed upstream in the Nansen Basin in 1990.

Abstract Categories: Changes in the Sea

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