GSO Researchers Explore the Shelf Break


GSO Professor Melissa Omand led a 14-member scientific party that included URI GSO researchers Pat Kelly, Kellen Rosburg, Austen Blair, Conor McManus, CT Harry, Noah Walcutt (incoming GSO student in January) and three URI undergraduates on a Rhode Island Endeavor Program cruise to the Atlantic shelf break, the transition area from the relatively shallow continental shelf waters and the continental slope which leads to the deep ocean abyss.

The shelf break is a dynamic and productive area, with nutrients mixing upward from deep water and plankton and other particles sinking, known as “marine snow.”  Omand’s cruise was designed to test how best to sample carbon export, the composition of the marine snow and nutrient fluxes in ways that resolve sinking and flux events over the “small” spatial scales – nominally 10km – characteristic of the shelf break front. Physical processes that drive fluxes over these scales are important, but are not resolved in global climate models.

Omand, who was Chief Scientist and Principal Investigator, and her team brought a variety of instruments to the shelf break to conduct sampling: a neutrally buoyant sediment trap that collected sinking marine snow as it drifted in the currents at a depth of 150 meters; a Wirewalker that vertically profiled between the surface and 150 meters; and surface-tethered array traps which sampled sediment at a depth of 200 meters.

Even before the R/V Endeavor arrived at the shelf break, a Slocum glider launched by Woods Hole Oceanographic Institution scouted the area for a week beforehand to give the research team an understanding of what was going on in the environment, helping them efficiently use their time on station.

The team continued to use the Slocum glider throughout the cruise, and will be comparing its measurements of nitrate, oxygen, particle scattering to those taken by a Remote Environmental Monitoring Unit (REMUS), an autonomous underwater vehicle piloted by scientists from the University of Maryland.  The data from each of those underwater vehicles were also compared to data collected by the more traditional conductivity, temperature, depth and optical sensors deployed over the side from Endeavor.

Professor Omand said that this test of a diverse array of autonomous platforms, the first of its kind, was a success that can be used as a template for future larger efforts.

In another first, the cruise was the first time a Chief Scientist directed an Endeavor cruise from ashore. R/V Endeavor was recently outfitted with a Ku band satellite antenna and associated equipment, giving Endeavor the ability to relay high definition video between ship and shore at 4 megabits per second. This “telepresence” capability enabled Prof Omand to observe, direct and consult with researchers on R/V Endeavor while she remained ashore at the Inner Space Center at GSO.


Photo: Prof. Melissa Omand in the Inner Space Center at GSO, photo by Alex DeCiccio