URI instrument that simulates Earth's rotation garners scientists $1.1 million NSF grant

04/09/04

Physical oceanographers at the University of Rhode Island Graduate School of Oceanography (GSO) and the University of Massachusetts at Dartmouth have received three new National Science Foundation grants totaling more than $1.1 million. The grants were awarded to support two projects that will utilize a new rotating table in GSO's Geophysical Fluid Dynamics Laboratory.

The rotating table, purchased by GSO physical oceanographer Dr. Peter Cornillon with funding from NASA and URI, is used to simulate the rotation of the earth, which has a major influence on the circulation in the ocean. This facility allows processes that occur on time scales from days to months in the ocean to be simulated in the laboratory over minutes to hours. The laboratory also has a particle image velocimetry (PIV) system, purchased with funds from the Champlin Foundation, which allows the velocity of the fluid to be determined remotely.

These two pieces of equipment were essential for the success of these grants, the first two externally funded research projects to use this facility.

GSO physical oceanographers Dr. Vitalii Sheremet and Dr. Peter Cornillon received a $586,673 grant to study the Scotian Shelf Water Crossover events which are characterized by the shelfbreak current leaping directly from the Scotian Shelf south of Nova Scotia onto Georges Bank across the Northeast Channel instead of flowing into the Gulf of Maine. Understanding the causes and variability of the crossovers is critical for knowledge of the basic ecology of the region and successful management of the Georges Bank fisheries. The physical features of the water in this region are known to be linked to the North Atlantic Oscillation (NAO), a recurring atmospheric pressure pattern that determines climate variability in the region, and the river output from the Gulf of St. Lawrence, and, therefore, are greatly affected by global warming and climate change. The proposed study involves theoretical, numerical, and laboratory modeling along with analysis of hydrographic and satellite remote sensing data. Funds earlier received from the Vetlesen Foundation allowed Sheremet to build a prototype laboratory model, perform exploratory research, and obtain preliminary results, which significantly contributed to the success of the current proposal.

Dr. Miles Sundermeyer of UMass-Dartmouth and Dr. Dave Hebert of GSO received grants totaling $571,352 over 4 years to study, using the rotating table, horizontal stirring in the ocean caused by small eddies. Studies of the temporal evolution of the distribution of purposely injected inert chemical tracers in the coastal and open ocean suggest that lateral dispersion on scales of 1 to 10 km is larger than can be explained by dispersion due to vertical variations in the currents and turbulent mixing of the tracer. Dispersion on these scales affects distributions of physical, biological, and chemical tracers, and is particularly important to understanding global ocean circulation and heat balances. It has been hypothesized that the observed dispersion on these scales may be due to stirring by small-scale eddy motions generated by mixing events produced by breaking internal waves. Previous analytical and numerical modeling studies support this conclusion. However, a complete description of the generation of these eddies, their effect on lateral stirring, and their eventual dissipation is still lacking. The laboratory experiments performed by Sundermeyer and Hebert will address these questions.

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