Alexander Osadchiev: results of hydrophysical studies from the 2025 MIPT–IORAS Floating University expedition

Alexander Osadchiev’s talk was devoted to the results of hydro-physical studies conducted during the Floating University expedition organized by MIPT and the Shirshov Institute of Oceanology, which took place in September–October 2025 in the northern Bering Sea and the western Chukchi Sea. The expedition focused on the distribution and transformation of Pacific waters in the western Chukchi Sea, as well as on the propagation and modification of the Siberian Coastal Current formed by the plume of the Lena River, other East Siberian rivers, and meltwaters. For the first time in recent years, a Russian team carried out large-scale measurements in this region characterized by extremely challenging logistics and ice conditions.

The measurements revealed that in September 2025, the Lena River plume reached the Bering Strait, where it was entrained by the Pacific water jet and mixed with it. The Lena plume also extended into the Chukchi Sea north of Wrangel Island, forming a surface freshening near the Herald Canyon area. In addition to surface waters, the expedition documented the characteristics of winter waters in the western Chukchi Sea. Apparently, winter waters from the East Siberian Sea intrude into the northwestern part of Herald Canyon, while the rest of the canyon in winter is occupied by winter Pacific waters entering through the Bering Strait.

Overall, the collected data show that the water mass structure in the western Chukchi Sea is far more variable than previously assumed, indicating the need to revise the traditional classification of water masses based on T–S diagrams.