Ocean temperatures in the upper 250 m in the northern North Pacific (60¿N, 149¿W) increased by more than 1 ¿C from 1972 to 1986 but are now decreasing. Subsurface temperature anomalies are well correlated (~0.58) with the air temperature anomalies at Sitka, Alaska; hence the coastal air temperatures can be used as a proxy data set to extend the ocean temperature time series back to 1828. Up to 30% of the low-frequency variance can be accounted for with the 18.6-year nodal signal. Additionally, spectral analysis of these air temperature variations indicates a significant low-frequency peak in the range of the 18.6-year signal. Similar low-frequency signals have been reported for Hudson Bay air temperatures since 1700, for sea surface temperatures in the North Atlantic from 1876 to 1939, and for sea level in the high-latitude southern hemisphere. The water column temperature variations presented here are the first evidence that the upper ocean is responding to this very long period tidal forcing. An enhanced high-latitude response to the 18.6-year forcing is predicted by equilibrium tide theory, and it should be most evident at latitudes poleward of about 50¿. These low-frequency ocean-atmosphere variations must be considered in high-latitude assessments of global climate change, since they are of the same magnitude as many of the predicted global changes. ¿ American Geophysical Union 1993