Mark McDonald - US grants

9521282 Webb This group from Scripps Institution of Oceanography at the University of California at San Diego will conduct a seafloor experiment to determine the size of the plumbing system beneath submarine hot springs on the Juan de Fuca Ridge and Gorda Rise, offshore from Oregon, Washington and British Columbia. They will deploy ocean bottom seismometers at two sites where the D/V JOIDES Resolution will drill holes in the vicinity of hydrothermal systems. JOIDES Resolution is the vessel chartered by an international consortium for basic research on marine geology; the lead agency in the program is the National Science Foundation through its Ocean Drilling Program. The deployments will begin before drilling, and will last for about two months post-drilling. It is anticipated that tiny earthquakes and flow within the fractured rock beneath the seabed will be recorded by the seismometers, and that this will allow location of events related to opening the subsurface hot reservoir to sea water. Mechanisms causing seismic noise are expected to be 1) cracking due to thermal stress, 2) acquathermal pressure fracturing resulting from reservoir temperature change, and 3) hydrofracturing due to the hydraulic head associated with the difference in density between cold seawater and hot pore fluids. The investigators expect to differentiate among these mechanisms based on the character of the seismic signature recorded on their instruments. They also expect to place constraints on the size of the reservoir based on the distribution of recorded events. This will provide the first direct measurement of a submarine hydrothermal reservoir, and will be an important step in understanding the properties of these widespread ocean ridge features. ***

The U.S. Global Ocean Ecosystems Dynamics (U.S. GLOBEC) program has the goal of understanding and ultimately predicting how populations of marine animal species respond to natural and anthropogenic changes in climate. Research in the Southern Ocean (SO) indicates strong coupling between climatic processes and ecosystem dynamics via the annual formation and destruction of sea ice. The Southern Ocean GLOBEC Program (SO GLOBEC) will investigate the dynamic relationship between physical processes and ecosystem responses through identification of critical parameters that affect the distribution, abundance and population dynamics of target species. The overall goals of the SO GLOBEC program are to elucidate shelf circulation processes and their effect on sea ice formation and krill distribution, and to examine the factors which govern krill survivorship and availability to higher trophic levels, including penguins, seals and whales. The focus of the U.S. contribution to the international SO GLOBEC program will be on winter processes. This component will focus on determining minimum population estimates, distribution and seasonality for mysticete whales, especially blue whales. This will be accomplished using passive acoustic recorders deployed on the seafloor for a period of one to two years. The deployment of a large aperture autonomous hydrophone array in the Antarctic will incorporate the use of passive acoustics as a tool for mysticete whale detection and census. The result of the integrated SO GLOBEC program will be to improve the predictability of living marine resources, especially with respect to local and global climatic shifts.