Neptune's Needle

Physical oceanographer. From childhood Iselin had enjoyed sailing, encouraged by a great-uncle.

During summers in his college years Iselin took long sailing trips in the Atlantic Ocean with boyhood friend Terrence Keogh. In his senior year he designed a 78-foot schooner, Chance, and had it built in Nova Scotia. For the next two summers, with college friends and Keogh, Iselin sailed to northern Labrador and to Bermuda, using equipment provided by Bigelow to make observations of the Labrador Current and the Gulf Stream. He received an A.B. at Harvard in 1926 and an A.M. in 1928. That year he had a 98-foot schooner built in Nova Scotia, which he and Keogh sailed across the Atlantic and back, again making observations.

Woods Hole Oceanographic Institution (WHOI) was established in Massachusetts in 1930. Bigelow was its director, and he appointed Iselin his general assistant. His first assignment was to design a research ship. WHOI had the 142-foot auxiliary ketch built in Copenhagen, Denmark, in 1930-1931 and christened it Atlantis. Iselin accepted the ship there and was in charge of its maiden voyage to home base. That vessel served as a research ship for WHOI until 1966.

Iselin was appointed physical oceanographer at the institution in 1932 and, after Bigelow's retirement in 1940, became its director, a position he held until 1950. He continued to serve WHOI as senior physical oceanographer, was again director from 1956 to 1958, and then held an endowed appointment until his death.

Iselin's researches were primarily on currents of the Atlantic Ocean, including their distribution, physical nature, and chemistry. He directed a series of trips on Atlantis to carry out systematic exploration of the Gulf Stream in all seasons. Iselin's trips measured temperature and salinity down to more than 4,000 meters, which provided many cross-sections in the northwestern Atlantic Ocean. Iselin's publications defined the Gulf Stream as a narrow, deep boundary between warmer waters of the Sargasso Sea and colder waters of the continental slope. He noted that, as a result of the earth's rotation, water in the boundary zone near the surface moves northeast with velocities to nine kilometers per hour in a narrow band. Iselin estimated the enormous volume of water transported in the northwest Atlantic, and he theorized on the relative importance of vertical and lateral mixing in water masses. His analyses of vertical distribution of water density proved useful to the U.S. Coast Guard in predicting the movements of icebergs in the north Atlantic.

An early project of Iselin and Ewing in the Caribbean was to determine why underwater sound waves seemed to diminish in the afternoon. Such sonar waves were just coming into use to detect submarines. With Athelstan F. Spilhaus, inventor of the bathythermograph, Iselin had first looked into this problem for the U.S. Navy in 1938. He and Ewing determined that the heating of surface water bent the sound rays downward and created an acoustic shadow zone.

Major projects on the transmission of sound in seawater, on fouling organisms, on underwater explosives, as well as on the development of undersea instruments were all directed by Iselin under wartime secrecy, and with his own participation in some of them. The scientists produced reports of great value to the navy, which led to a dramatic increase in its postwar support of oceanography.

Iselin became a dedicated member of the Committee on Undersea Warfare of the National Academy of Sciences (1946-1970) and of the NAS Committee on Oceanography (1957-1964). With Francis Minot shortly after World War II he founded the Ocean Resources Institute to focus on the problems of fishermen. Beginning in the late 1950s he took considerable interest in international problems related to the use of ocean resources

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Compiler

Peter Richards