Quarterdeck Volume 4, Number 2, Summer 1996

The world is our oyster
R/V Gyre cruises North and South America this summer

Daniel A. Bean
Douglas C. Biggs
Edwin W. Shaar

The Department of Oceanography's research vessel, Gyre, departed on June 4, 1996 for a four-month cruise surveying the ocean floor using the Geodynamic Research Institute's high-resolution seafloor imaging and mapping system, [TAMU]2.* Chance & Chance (C&C) Technologies Inc. of Lafayette, Louisiana, chartered the ship and will operate the [TAMU]2 system to conduct a bathymetry survey for use building a Pan-American telecommunications cable route. Alaminos surveys The [TAMU]2 system required an initial week of calibration and testing in the Gulf of Mexico, which enabled oceanography students and faculty to survey Alaminos Canyon using [TAMU]2 and survey a nearby Loop Current eddy using an Acoustic Dopper Current Profiler (ADCP), a conductivity-temperature-depth (CTD) meter, and expendable bathythermographs (XBTs). Oceanography graduate students Dan Bean, Tiesong Lu, and Chris Spagnuolo along with geology/geophysics graduate student Jen McGuire joined Professor Doug Biggs in this initial stage of the research cruise. [TAMU]2 is a high-resolution side-scan sonar system which is towed near the ocean surface. The objective of the Alaminos Canyon survey was to supplement data collected previously by the Deep Tow survey system, which surveys near the ocean floor.Ý After collecting bathymetry data and images of most of the Alaminos Canyon area, the team processed them on the ship to create a realistic mosaic image of the canyon. There is currently a drill ship in this area, and these data will be important for determining the safety and feasibility of deep-water drilling now and in the future. Earlier this year, each student on board the Gyre participated in a Deep Tow survey of the Alaminos Canyon, so this cruise provided an excellent opportunity for the students to expand their experience with acoustic research equipment. They were directly involved in planning Alaminos Canyon survey cruise tracks, launching and retrieving [TAMU]2, monitoring the instrument package, and collecting and processing the data. Tracking Eddy A After completing the [TAMU]2 survey of Alaminos Canyon, Gyre did an ADCP, CTD, and XBT transect through an eddy that was found by a previous Gyre cruise to have separated from the Loop Current in September 1995. The warm-core ring called "Eddy A" was centered near 25°N, 95°W in June 1996. It had drifted west-southwest across the gulf and was colliding with the continental margin. The XBT survey found that its sea-surface height anomaly (the difference between the water level of the eddy and the water surrounding it) had decreased about 30 centimeters since September. Upon reaching the continental margin, bottom friction apparently caused the anticyclonic Eddy A to transfer some of its mass and vorticity, generating a region of cyclonic circulation. On to the Caribbean and Pacific! After the student training and research in the Gulf of Mexico, Gyre proceeded to Cozumel, Mexico to offload some of the scientific party, then stopped at the Caribbean island of St. Croix to pick up equipment and additional C&C personnel. C&C's [TAMU]2 survey began near St. Croix and extends through the Panama Canal and down the Pacific side of South America to Las Machas, Chile. Gyre is expected to return to Louisiana to end the cruise in early October 1996. This cruise represents an important partnership between the oceanography department and industry. The mission of the cruise is to obtain data for crucial telecommunications improvements in the Caribbean and South America. It also provides Texas A&M oceanographers and students with at-sea experience and a new, precise, high-resolution data set describing marine geology and tectonic features of the Peru-Chile Trench and the Caribbean Sea. For the first time, scientists will be able to examine variations in the structure of a subducting ocean plate at or near the trench axis in one 3000-kilometer swath. This [TAMU]2 work is an outstanding example of merging scientific and private-sector interests for mutual benefit. The project also constitutes important financial support for Texas A&M geoscience research and associated graduate programs.

Path of the R/V Gyre in the Gulf of Mexico and Pacific.

Comments to: web@ocean.tamu.edu

Last updated February 5, 1997