A Pioneer in Naval Oceanography: Navy CDR Mary Sears

By Bob Freeman, Office of the Oceanographer of the Navy.

In celebration of Women’s History Month it is worth considering the accomplishments of a small, shy marine plankton specialist from Massachusetts named Mary Sears (1905-1997) who became a pioneer in naval oceanography.

Sears is generally associated with the Woods Hole Oceanographic Institution. In 1932, while completing her Ph.D. in biology from Radcliffe College, she began working as one of the first ten research assistants at the recently founded institution. She would maintain her association with Woods Hole until her retirement in 1970, becoming a senior marine biologist and eventually being named Scientist Emeritus.

In 1943, at the height of World War II, Dr. Sears was commissioned as a lieutenant junior grade (LTJG) in the Navy and assigned to the Naval Hydrographic Office in Washington, DC where she helped establish a small Oceanographic Unit that greatly expanded the role of applied oceanography in naval warfare.

As able-bodied men were needed in the combat zones, the Naval Hydrographic Office increasingly relied on women. By 1944 there were 30 women officers and 332 enlisted women working there. The Oceanographic Unit was composed of 13 women and three men.

The Naval Hydrographic Office was created in 1854 with a focus on ocean bottom mapping (hydrographic surveys) to assist in creating more accurate charts to enhance safety of navigation. Although it maintained a small marine meteorology division, it wasn’t until the 1930s that the Navy really began to focus on oceanography.

This interest was partly due to advances in submarine warfare and the newly developed sonar technology. Understanding such ocean properties as temperature distribution, pressure, salinity, and bottom characteristics is important to predicting how sound travels in the water. With this knowledge, sonar could be used more effectively in hunting enemy submarines, and our submarines could develop strategies to more effectively avoid sonar detection.

LTJG Sears coordinated ocean research conducted at Woods Hole that assisted this effort, and her fleet publication “Submarine Supplements to the Sailing Directions” predicted the presence of thermoclines in certain waters. These are areas of rapid temperature change in the water column which cause refraction and bending of sound waves. Submarines can effectively hide under thermoclines, avoiding detection by ship-mounted sonars. This remains a critical consideration in modern submarine warfare tactics.

Naval oceanography was also interested in such diverse areas as current drift for search and rescue operations and floating mines, surf predictions for amphibious landings, and the turbulent effects of sea and swell waves on moored mines. Marine biology was also an interest since bioluminescent plankton activated by ship wakes could be used to locate ships in the dark, certain organisms contributed to ambient marine noise that inhibited sonar operations, large kelp growths fouled amphibious landing craft, and certain marine organisms degraded mine mechanisms.

Much of this data was time critical and needed to support ongoing operations, so Sears gathered data from observers in the fleet and from existing civilian research papers and produced detailed oceanographic reports and pamphlets for use by mission planners.

Sears also worked on improving tidal predictions. The Navy became ruefully aware of its shortcomings in this arena after the battle of Tarawa when an inaccurate tide prediction stranded an amphibious group of Marines on a reef, allowing them to be cut to pieces by shore-based Japanese machine gunners. Sears used refined tidal predictions and wave refraction charts to recommend very successful landing locations for the subsequent amphibious assaults on Luzon and various islands around Okinawa in 1945.

During the course of the war, the Oceanographic Unit was expanded into a division, and Sears was promoted to lieutenant commander. Years later, in 1960, the preeminence of oceanography was officially recognized when the Naval Hydrographic Office was renamed the Naval Oceanographic Office. Sears remained at the Oceanographic Division until 1946, working to shape the future of naval oceanography in the post-war era. She then transferred into the Naval Reserve, eventually retiring as a commander in 1963.

After leaving active service, Dr. Sears continued to make her mark. In 1959 she was chairperson of the First International Congress on Oceanography, and she became a member of the American Association for the Advancement of Science, the American Academy of Arts and Sciences, the Society of Women Geographers and the American Geophysical Union.

In recognition of Dr. Sears’ contributions to naval oceanography, the Navy named one of its oceanographic survey ships after her. The USNS MARY SEARS (T-AGS 65) was launched in October 2000 and continues to serve today. It is the 12th Navy ship to be christened with a woman’s name, and the first oceanographic survey ship.

Roger Revelle, director of the Scripps Institution of Oceanography and a colleague of Mary Sears, once said: “…the federal government…has generally forgotten that the first oceanographer of the Navy in modern times was a short, rather shy and prim [Navy] lieutenant j.g. They underestimated the powerful natural force that is Mary Sears.”