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October 27, 2003
Seattle, Washington, USA

Distribution of the Convective Lower Halocline Water in the Eastern Arctic Ocean

Takashi Kikuchi¹, Koji Shimada², Kiyoshi Hatakeyama³, James H. Morison^4
1Ocean Observation and Research Department, Japan Marine Science and Technology Center, 2-15, Natsushima-cho, Yokosuka, 237-0061, Japan, Phone 81-46-867-9486, Fax 81-46-867-9455, takashik@jamstec.go.jp
²Ocean Observation and Research Department, Japan Marine Science and Technology Center, 2-15, Natsushima-cho, Yokosuka, 237-0061, Japan, Phone 81-46-867-9485, Fax 81-46-867-9455, shimadak@jamstec.go.jp
³Ocean Observation and Research Department, Japan Marine Science and Technology Center, 2-15, Natsushima-cho, Yokosuka, 237-0061, Japan, Phone 81-46-867-3876, Fax 81-46-867-9455, hatakeyamak@jamstec.go.jp
⁴PSC/APL, University of Washington, 1013 NE 40th Street, Seattle, WA, 98105-6698, USA, Phone 206-543-1394, Fax 206-616-3142, morison@apl.washington.edu

We investigate distribution of Convective Lower Halocline water (CLHW) in the eastern Arctic Ocean using observational data. At first, results from ice-drifting buoys showed differences of water mass characteristics in the upper ocean among in the Amundsen Basin, over the Arctic Mid Ocean Ridge, and in the Nansen Basin. The CLHW, which is represented as salty water with freezing temperature, covers the Arctic Mid Ocean Ridge and the Nansen Basin, but the property of CLHW in the Amundsen Basin has been weakened in the early 2000s. The differences of water mass characteristics among these regions were caused by whether effective winter convection occurred in the basin or not.

Using the climatological data, we found that typical CLHW covers only the Nansen Basin. The advance/retreat of CLHW since 1990s in the eastern Arctic Ocean was investigated using historical observational data. In the early 1990s, the CLHW covered only the Nansen Basin, which is similar to the result from the climatology. The area of the CLHW extended to the northern side of the Arctic Mid Ocean Ridge in the mid 1990s and moreover the CLHW covered in the whole of the Amundsen Basin in the late 1990s. In the early 2000s, the area of CLHW was shrunk and moved back to the northern side of the Arctic Mid Ocean Ridge. These results correspond to the results on the surface salinization in the eastern Arctic Ocean.

It should be concluded that the change of Cold Halocline was caused not only by a change of surface salinity but also by a frontal shift of the whole of the upper ocean in the eastern Arctic Ocean. Accurate ocean current measurement has been conducted using ice-drifting buoy. We found that topographic controlled current was dominant over the Lomonosov Ridge and the Arctic Mid Ocean Ridge. In the Amundsen Basin, mean current direction was from the Lomonosov Ridge to the Arctic Mid Ocean Ridge in the spring to early summer season. The mean speed is about 2.0 cm/sec. This result is different from the notion that was imaged from sea-ice drift and suggested that there would be along-isobath difference of water properties within the Amundsen Basin.

Abstract Categories: Changes in the Sea

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