Hydrophysical experiment “Megapolygon‐87” in the northwestern Pacific subarctic frontal zone

Abstract

Six large-scale, high-spatial-resolution conductivity-temperature-depth (CTD) surveys (1653 profiles) and numerous moorings (an 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.

Impact of remotely generated eddies on plume dispersion at abyssal mining sites in the Pacific

“…Extreme examples of strong deep-ocean flow include turbidity currents in canyons of continental slopes 14 and so-called benthic storms 15 . In two accounts 16 , 17 of western ocean margins, a synoptic flow-field related to the propagation of large (mesoscale) features was coherent over the full ocean depth. In the Central Tropical Pacific, the influence of surface eddies on the currents at abyssal depths has also been noted 18 , 19 .…”

Subthermocline eddies observed by rapid‐sampling Argo floats in the subtropical northwestern Pacific Ocean in Spring 2014

“…For the cold STE, the isoline of the minimum S (33.73 psu) extends from about 40°N off the east coast of Japan to about 50°N off the west coast of North America (Figure a). The isoline of the maximum DO (248.3 µmol/kg) has similar geographic positions to the 33.73 psu isohaline west of 160°W (Figure b), both showing a good correspondence with the SAF in the North Pacific [ Maximenko et al ., ] (Montgomery potentials in Figure ). These results seem to suggest that the warm STE originates from the North Pacific STF region, and the cold one originates from the North Pacific SAF region.…”

A dynamically consistent analysis of the mesoscale eddy field at the western North Pacific Subarctic Front

“…In situ observations of temperature/salinity and velocity carried out in September/October 1987 comprise the core data set used in the study. These measurements were done in the course of a multiship experiment “Megapolygon‐87.” A detailed account of the data and of the major results of MP was recently given by Maximenko et al [2001] and can be found in earlier Russian literature [e.g., Koshlyakov et al , 1992]. In the present study we focus on the most intense period (6 September to 5 October 1987) of spatial coverage of MP area by in situ observations.…”

“…In the present study we apply the dynamically constrained data interpolation technique to one such data set, namely the Megapolygon (MP) experiment (Figure 1). The MP data, revisited recently by Maximenko et al [2001] (hereafter MX), are synthesized with Geosat altimetry and ECMWF winds through a multivariate interpolation of all these data sets on a regular space–time grid. Interpolation is performed by minimizing misfit between a solution of quasigeostrophic (QG) equations and observations.…”