Hydrophysical experiment Megapolygon-87 in the northwestern Pacific subarctic frontal zone

The purpose of this paper is to familiarize readers with major results and findings of the biggest multi-institutional Soviet hydrophysical experiment, Megapolygon-87, conducted in the northwestern Pacific Subarctic Frontal Zone in June-October 1987, Six large-scale, high-spatial-resolution conductivity-temperature-depth (CTD) surveys (1653 profiles) and numerous moorings tan array of 177 buoys deployed within a 500 km x 500 km area) with current meters at four depths provided unique observations of frontal structure, mesoscale and submesoscale eddies, and their evolution and interaction with each other. We discuss errors induced in the velocity records by surface waves and show how they can be corrected to a reasonable value. joint analysis of current meter and CTD data allowed detection of a number of interesting processes and objects in the study area. Among them are meandering of the Subarctic Front around its branching point with formation of chains of cyclonic and anticyclonic mesoscale eddies and strong baroclinicity of velocity fields with significant difference between the thermocline and abyssal flows. Statistical characteristics of corrected Megapolygon-87 velocities are compared with preceding measurements in the region.