Mesoscale features along the first Oyashio Intrusion

Abstract

Satellite and hydrographic observations obtained during May 1981 are used to examine the sea surface and subsurface temperature structures within a portion of the Tohoku Area (38°–43°N) extending east of Japan to 149°E longitude. These data delineate the Oyashio Front and the evolution of mesoscale features dominating the surface layer circulation east of northern Honshu and Hokkaido. A perturbation on the first Oyashio Intrusion generated eddies adjacent to the Oyashio Front and contributed to a jetlike feature with associated, paired vortices that intruded into what has been defined as the “perturbed area” (39°–42°N) southeastward from the vicinity of the Tsugara Strait. NOAA6 satellite Advanced Very High Resolution Radiometer infrared images and sea surface temperature distributions identified specific eddies and fronts, that also appeared as banded warm and cold regions within XBT (expendable bathythermograph) sections. The satellite data helped define the lateral extent of the features, while the sections provided estimates of their vertical extent. A new procedure for the determination of satellite sea surface temperatures was used to produce a composite temperature distribution over a portion of the Tohoku Area. The satellite‐derived temperature estimates exhibited a 0.8°C rms scatter about a 0.6°C warm bias relative to the XBT data. This map displays the intense mesoscale sea surface temperature variability in the region along the Oyashio Front and within the subarctic regime.