NORPAC Hydrographic Data Report of the Scripps Institution of Oceanography, University of California, and the South Pacific Fishery Investigations, U. S. Fish and Wildlife Service, for the NORPAC cruise of August-September 1955.

In July, August, and September of 1955 agencies from Japan, Canada, and the United States combined their facilities to make a great synoptic oceanographic survey of the North Pacific Ocean. Such a coverage has long been needed to provide the background knowledge of hydrography for studies of fisheries problems. The enormous gyral of the Pacific Ocean had been covered before in piecemeal style with independent efforts being either too small or covering too long a time for their results to be used effectively in determining the currents and transport of water over the entire area. Contiguous cruises made by the Pacific Oceanographic Group of the Fisheries Research Board of Canada and the California Cooperative Oceanic Fisheries Investigations in August of 1950 and by the latter and the Pacific Oceanic Fishery Investigations of the U. S. Fish and Wildlife Service in Hawaii in January of 1954 had confirmed the great advantages to be gained by covering large areas in short periods. The proposal for such an effort was made at the Fifth Pacific Tuna Conference of November, 1954 and it was immediately decided to attempt to make such a survey. The hydrographic work was to comprise hydrographic casts for measurement of temperature, salinity, dissolved oxygen, phosphate-phosphorus, and in some cases, silicate and deuterium; bathythermograph lowerings, thermograph records of surface temperature, measurements of surface currents with the GEK (Geomagnetic Electrokinetograph), measurement of transparency (on daylight stations) with the secchi disc, weather observations, and depth measurements with recording sonic apparatus, and collection of water samples for determination of the level of radioactivity. The biological work consisted of net hauls for zooplankton and phytoplankton at various levels down to 1,000 meters, observations of fish, mammals and birds, trolling, and dipnetting. In area covered, number of stations occupied, number of observations taken, and samples collected this is the largest oceanographic survey ever made in such a short period (most of the data were taken in August though a few ships began in July and did not return until mid-September)