HR: 0830h
AN: OS51B-0860    [PDF]
TI: Long-Term Fuid Flow Measurements From Widely Varied Oceanic Settings Elucidate Near-Surface Hydrologic Environments
AU: * Tryon, M D
EM: mtryon@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Dr, La Jolla, CA 92093-0244 United States
AU: Brown, K M
EM: kmbrown@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Dr, La Jolla, CA 92093-0244 United States
AB: The quantification of aqueous flux rates from various ocean floor environments has been a goal of numerous scientific programs for more than a decade with increasing focus on gas hydrate regions. Six years ago we developed the Chemical and Aqueous Transport (CAT) meter to collect long-term temporal records of low to moderate aqueous flow rates in sedimented ocean floor environments and, more specifically, to quantify to mass flux associated with the formation of gas hydrates. Since that time thirty of these instruments have been built and over a hundred deployments accomplished in a variety of hydrate and non-hydrate settings. We present here an overview of the results of these deployments and compare and contrast the flow records from these varied hydrological environments. Specific environments include: Gas Hydrates (Hydrate Ridge and the Eel River area on the Cascadia convergent margin, and Bush Hill in northern Gulf of Mexico), Hydrothermal (Japan's Sagami Bay and the incoming plate offshore Costa Rica's Nicoya Peninsula, TicoFlux area), and the tectonically active convergent margin off Nicoya and Osa. One of the most important outcomes of this research is the realization that fluid flow across the seabed/ocean interface is often dominated by shallow subsurface and oceanographic processes which vary significantly over time. These processes can be as simple as the diurnal pressure gradients caused by the rise and fall of tides to highly complex processes associated with the formation and transport of subsurface free gas. These processes have been both a boon and a bane to our research. Tidal oscillations have tended to mask the net flow in many very low flux settings. The high degree of spatial and temporal variation in some environments have revealed the extreme difficulty of quantifying the more widespread mass flux associated with the underlying tectonic processes. Yet, the nature of these variations have allowed us to better constrain the fundamental processes involved, ultimately leading to a better understanding of the overall hydrologic system. Our greater understanding of the near-surface hydrological environment has also increased our understanding of shallow sediment biological and geochemical processes. The serendipitous collection of data from the OOST region of Nicoya containing synchronous hydrologic events suggests that CAT meters may also prove to be effective monitors of volumetric strain such as that associated with aseismic creep events.
DE: 1094 Instruments and techniques
DE: 1800 HYDROLOGY
DE: 3015 Heat flow (benthic) and hydrothermal processes
DE: 8045 Role of fluids
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting