Seafloor maps no longer secret.

Seafloor maps no longer secret

In a reversal bound to excite oceanographic researchers, fishermen, mineral explorers and myriad others, the U.S. Navy has decided to allow the release of highly detailed maps of seafloor topography in the nation's Exclusive Economic Zone (EEZ), a 200-mile-wide border extending from U.S. shores. Established by President Reagan in 1983, the EEZ covers an area slightly larger than that of U.S. land.

In an effort to survey this neew frontier, the National Oceanic and Atmospheric Administration (NOAA) has been mapping the EEZ floor both with Sea Beam, a high-resolution bathometer that measures water depth, and with extremely precise navigation systems. Yet most of these maps have never surfaced in the public domain. Concerned that detailed maps would help foreign submarines navigate undetected through U.S. waters, the Navy persuaded the White House in 1985 to prohibit release of Sea Beam data without Defense Department approval (SN: 3/15/86, p.170). For the last four years, NOAA officials have tried to convince the Navy to reconsider.

This year the appeals paid off. In late March, Oceanographer of the Navy Admiral Richard F. Pittenger wrote a letter to NOAA Administrator William Evans announcing that "most" data from the EEZ could soon be released for public use. One exception, exit routes for ballistic missile submarines, will remain controlled. Lt. Bruce Hillard of NOAA's Ocean Mapping Section in Rockville, Md., says the agency has yet to receive official notice concerning which specific areas will remain classified, but that NOAA hopes to begin releasing the Sea Beam data shortly. So far, the agency has produced some 25 maps, covering roughly 2 percent of the EEZ.

The high-resolution maps will be vast improvements over old bathymetric plots. Sea Beam's sonar covers a broad swath of seafloor, allowing a ship to map an entire area by tracking back and forth in well-spaced lines. Older techniques measured only the depths directly beneath a ship. Since mapping ships made tracks 5 to 10 miles apart in offshore areas, cartographers had to fill the gaps with their imagination, making the available maps very subjective, Hillard says.