Record-breaking warming in the Kamchatka Current halocline

We used historical CTD observations and Argo data to obtain the characteristics of the Kamchatka Current halocline and its eddies. Kamchatka Current eddies have a cold low salinity core in contrast with Aleutian eddies that contain warm and saline waters of Alaskan Stream origin. The Kamchatka Current eddies are smaller with diameter of ~ 100–120 km. Kamchatka Current eddies have a thick cold layer in a halocline. The temperature in their core increased by ~ 2.4 °C from the beginning of observations in 1990, while salinity decreased. We found that 2012 was the coldest year in the Kamchatka Current. Record-breaking warming occurred in the Kamchatka Current during 2015 to 2018. Temperature in the halocline rose by ~ 3 °C from 2012 to 2018 at 26.6σ θ , while in the western Bering Sea temperature rose by 2.3 °C. It is plausible that the warming in the Kamchatka Current halocline during 2012 to 2018 is associated with the lowest recorded sea ice coverage in the Bering Sea. Similar warming occurred in the Oyashio Current. Salinity, temperature and specific density in the 2012 Simushir eddy were extremely low for the 30-year row of observations from 1990 to 2020. Extremely low salinity was also found in the 2012 Aleutian eddy off the Near Strait.