Decadal variability of the North Pacific Polar Front: Subsurface warming versus surface cooling

[1] Over 200 hydrographic sections are used to trace the Polar Front defined as the southern boundary of the pure'' subarctic stratification with a pronounced, extremely cold, subsurface temperature minimum underlain by a temperature maximum. The front extends from 40degreesN off Japan to 57degreesN in the Gulf of Alaska where it retroflects and continues WSW with the Alaskan Stream. The front's decadal variability from 1977-1999 is examined along 150degreesE, 170degreesE, 175.5degreesE, and 180degreesE. At these longitudes the front is relatively stable, except for 170degreesE, where it shifts north-south by 400 km every 6 years. Most time series reveal a subsurface warming of similar to1degreesC per decade, and a surface cooling, of the front. Since the subsurface temperature minimum is a remnant of winter convection, the subsurface warming signals an amelioration of the winter climate, whereas the summer climate becomes colder.