Characteristics and Flow of Pacific Water in the Western Chukchi Sea:Effects of Strong Wind Forcing

The Chukchi Sea represents an important transition zone between waters of the Pacific and Arctic Oceans. However, due to the relative dearth of measurements on the western Chukchi shelf, the precise pathways and modification of the Pacific-origin water in this region are not well understood. Here we present results from a shipboard survey in September 2009 that sampled both the US and Russian sides of the Chukchi shelf as part of the RUSALCA program. The hydrographic properties and pathways of four different water masses are investigated. In some respects the spatial distributions of these water masses are as would be expected based on information from the historical World Ocean Database, but there were significant differences. Most notably, the two main summer waters entering the Chukchi Sea were transposed in Bering Strait, and the warm, fresh Alaskan coastal water was diverted from its normal coastal pathway northwestward through Herald Canyon. It is argued that this was the result of atmospheric forcing. Using an idealized numerical model we show that the Ekman response to the wind can cause such a transposition, and that the consequences of this will persist on the shelf long after the winds subside.