Distribution of Pacific-origin water in the region of the Chukchi Plateau in the Arctic Ocean in the summer of 2003

The upper ocean thermohaline structures in the region of the Chukchi Plateau are analyzed with the hydrographic data collected by the Chinese National Arctic Research Expedition in the summer of 2003. Three types of the Pacific-origin water were found in the upper ocean, Alaska Coastal Water (ACW), summer Bering Sea Water (sBSW) and winter Bering Sea Water (wBSW) are indicated by two maximums temperature and one minimum temperature, piling up from the upper to the lower respectively. The extreme warm ACW with a maximum temperature of 1.62℃ was found in the southwestern Canada Basin at a depth of about 50 m. A pathway of the ACW into the basin from its adjacent area did not existed in the expedition period. So it is speculated that the extreme warm feature of the ACW was formed locally in 2003. The relative weak ACW occurred to the east of the Chukchi Cap and in the southern Chukchi Abyssal Plain. The latter one might originate from a warm downwelling that existed in a small canyon at the shelf break of the Chukchi Sea. The sBSW without the ACW was found only at the southwestern flank of the Chukchi Cap. The ACW and the sBSW were not found in the northernmost station at 81°N,which indicates the north boundary of the upper Pacific-origin water in the Canada Basin. The wBSW, which existed in all deep stations, was exactly uniform at temperature. The difference of the core potential temperature of the wBSW in the deep regions is only 0.08℃.