Using dissolved oxygen (DO) concentration at isopycnal surfaces we have observed an oscillation in the intermediate water layer of the Western Subarctic Gyre (WSG) and the Kuril Basin of the Okhotsk Sea with a period of about 20 years. The interdecadal oscillation in DO is strongly correlated with the intensity of the Aleutian Low pressure cell with a 2-year time lag. The interdecadal variations in DO in the intermediate water layer of the WSG and the Okhotsk Sea may be a result of oscillation in the atmospheric forcing, leading to variations in the isopycnal fluxes of DO at the boundaries of the Okhotsk Sea-Western Subarctic Gyre-subtropical region, the isopycnal-surface replacement in the WSG, and in changes in the intermediate water formation rate in the Okhotsk Sea. ¿ 2001 American Geophysical Union