Warming of intermediate layers in the upper Oyashio in 1953–2007

Abstract

Considerable variations in intermediate water characteristics were found in the upper Oyashio based on the oceanographic data from 1953 to 2007. The long-term temperature trend at the 26.75σϑ isopycnal is 0.03°C/year. This temperature trend is considerably higher than that determined earlier for the Sea of Okhotsk intermediate water and much higher than the World Ocean temperature trend. The westward transport of warm and salty water of the Alaskan Stream is most likely to cause the changes in the Kamchatka Current and upper Oyashio. It is established that Aleutian mesoscale eddies move westward from the location of their formation south of the Blizhniy Strait and transport warm water (3.8–4.2°C) in their core (100–600 m, ∼26.75σϑ)). As the trajectory of eddies is quite stable, the westward flow of warm and salty intermediate waters considerably influences the upper Oyashio characteristics.