Mid-Ocean Dynamics Experiment records

The Mid-Ocean Dynamics Experiment (MODE) was one of the first large-scale and extensively instrumented field experiments carried out by physical oceanographers. Conducted in two phases between November 1971 and July 1973, the experiment explored the role of mesoscale eddy motions in the dynamics of general oceanic circulation. Henry Stommel of MIT and Woods Hole Oceanographic Institution (WHOI) was a driving force behind the plans for the experiment. It was during British oceanographers John Swallow and James Crease's R/V Aries expedition in 1959-1960 that evidence for the existence of energetic, rotating water columns or eddies was obtained. For their experiment, free drifting floats, since known as Swallow floats, were ballasted at 2000 and 4000 meter depths in the northwestern Atlantic Ocean and tracked in an attempt to measure slow drift in deep water. Plans for a mid-ocean dynamics experiment were solidified during a summer panel meeting at WHOI on July 20-24, 1970. Thirteen academic and oceanographic institutions and an international team of oceanographers from the United States, Great Britain, Sweden, and West Germany would later agree to participate in the experiment.

MODE was as much an exercise in organization as it was a scientific experiment. Collective responsibility and authority for the experiment resided in the twenty-one-member MODE Scientific Council, formed in mid-1971. Its membership consisted of the principal investigators from each of the experimental projects and representatives from the MODE Theoretical Panel. In addition, a six-member Executive Committee, two co-chairs, Allan R. Robinson of Harvard University and Henry Stommel, and an executive officer, Dennis Moore of Nova University, monitored the overall operation of the experiment. Standing committees were created out of a need for cooperation and collective guidance among investigators. The National Science Foundation's Office for the Decade of International Ocean Exploration was the principal source of funding for the Mid-Ocean Dynamics Experiment. Other sources included the Office of Naval Research, the National Oceanographic and Atmospheric Administration, and the British National Environmental Research Council.

The intensive MODE-I field program, carried out between March and July 1973, was the culmination of a sixteen-month theoretical and observational field study known as both MODE-0 and PREMODE. The MODE-I program was a collection of twelve individual experimental and theoretical scientific projects performed simultaneously, each a substantial experiment in its own right. The field program for MODE-I was concentrated in a 600-square-kilometer test site that extended from 28 N 69 40'W, an area in the mid-ocean between Bermuda and Florida.

The duration of MODE-I was limited by the endurance of the equipment. Six ships, two aircraft, and a variety of new, sophisticated instruments, neutrally buoyant floats, "free fall" velocity profilers, and air-dropped current probes, were utilized for the experiment. The design of the experiment relied on an objective mapping scheme previously developed by meteorologists, and applied to oceanography for this experiment.

A coordinated communications network was necessary to organize the movements of the six-ship MODE fleet, personnel, and instrumentation. Undersea cables were extended from a communications center set up at the Bermuda Biological Station to land lines in the US, making phone communications between ships and participating institutions possible. Termination points were at WHOI, MIT, and Harvard, Yale, and Johns Hopkins Universities.

Information critical to the ongoing evolution of the field program, hydrostatic data, float positions, instrumentation launches and recoveries, was relayed daily to the "Hot-Line Center" and disseminated in weekly MODE Hot Line Bulletins and biweekly Mode Hot Line News publications.

MODE-I generated a massive amount of data. An important component of the experiment was the use of different instruments to measure the same phenomena from dissimilar views. In this way a greater understanding of instrument accuracy could be determined and ultimately synthesized into a description of an eddy. To provide a forum for theoretical and dynamical discussions of the eddy problem and general oceanic circulation, to disseminate synthetic analysis of MODE-1, and to develop a draft for a synoptic atlas, scientists followed MODE-I with a two-month "Summer Institute" at the University of Rhode Island in July and August of 1974. Discussions with the ten-member USSR delegation at the Summer Institute led to plans for a joint US and USSR experiment, to be called POLYMODE. The goal was to investigate the eddy field not only on the main thermocline, but also in the deep ocean and upper mixed layer.

Two films, "Storms in the Deep Sea" and "The Turbulent Ocean," both made by Centre Films, Inc. of Hollywood, California, document the Mid-Ocean Dynamics Experiment. The latter film was made for television and aired on the Public Broadcasting System in June of 1974. A third film, the "Recovery of a MODE Mooring," by Adam Gifford and Buoy Group Film, was developed for a presentation to one of the funding agencies, the Office of Naval Research.