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Home >> Resources >> FLIP >> Bibliography - Abstracts |
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Following is a listing of abstracts which were
presented at the American Geophysical Union Conference in December 2002
in San Francisco, California. Stable Platform Designs for Global DEOS Moorings John A Orcutt Jonathan Berger Frank L Vernon III Scripps Institution of Oceanography, 9500 Gilman Drive, 0210, La Jolla, CA 92093, United States Oceanography has been dominated for at least two centuries by an expeditionary approach and examples include the voyage of the Beagle in 1831-1836 and the Challenger Expedition in 1872 - 1876. In the U.S., the capabilities for expeditionary research were greatly amplified during and especially following WWII. Today the U.S. alone has established a research fleet of 28 vessels organized through UNOLS. While experimental oceanography has made enormous contributions over the decades and centuries, this approach has not been well suited to investigating processes in which transients are important. The Dynamics of Earth and Ocean Systems (DEOS) program was developed in 1997 to promote the idea of making long-term observations in the oceans - to establish a long-term presence in the oceans. DEOS, now under the sponsorship of the Consortium for Ocean Research and Education (CORE) with support from the NSF, advocates the collection of long-term time-series data with the recognition that this is the only viable approach to observe transients and changes and to enhance the signal-to-noise ratio of weak signals. Moored ocean buoys are a technically feasible approach for making sustained time series observations in the oceans and will be an important component of any long-term ocean observing system. Scripps and Woods Hole developed the ocean mooring systems, designed for decadal time scales, in an NSF-sponsored design study. One of the designs bears a strong familial resemblance to R/P FLIP and is especially well suited for maximizing system life as well as ensuring robust Internet connectivity. I will review this design and describe feasibility experiments conducted to test communications feasibility. Because of the broad spectrum of scientific needs identified during planning, it is clear that there is no single buoy or mooring design that will meet all of these needs while at the same time minimizing costs. An alternative British design may be particularly well suited for high latitude deployments. Ongoing experiments to demonstrate components of the mooring program will be discussed. Internal Waves, Reference Frames and the Search for Intrinsic Frequency Robert Pinkel Luc Rainville Jonathan Pompa Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093-0213, United States For the past 40 years, internal wave and fine-scale fields have been studied using a variety of spectral techniques. Frequency spectra of vertical displacement and horizontal velocity appear to be continuous, with the addition of discrete near-inertial and tidal peaks. When the combined space-time variability of the fields is tested against linear internal wave theory, agreement is generally poor. An added "vortical" or "fine-structure" field is often invoked to explain observations. Working from deep-sea stable platforms both in the Arctic (the polar ice cap) and the open ocean (FLIP), recent data suggest that much of the continuous nature of the internal wave frequency spectrum results from simple Doppler spearing of a few principal spectral constituents. The apparent role of the vortical field is dependent on the reference frame in which observations are made. Such observations encourage revision of our view of the spectral cascade of energy from large to small scales. Observations of Langmuir Circulation from FLIP Jerome A Smith Scripps Institution of Oceanography, 0213 U.C.S.D, La Jolla, CA 92093-0213, United States Langmuir circulation has significance across the marine disciplines. Enhanced deepening and inhibited re-stratification can alter the surface temperature and hence net air-sea exchanges. Organization of bubbles into windrows introduces dramatic sound speed variability and also affects air/sea gas fluxes. Organization of seaweed and plankton affects marine life, including pelagic fisheries. Finally, dispersal by Langmuir circulation is a major component in models for oil-spill tracking and for search-and-rescue operations. To get an adequate picture of the forcing and response of Langmuir circulation (and the wind-mixed layer in general), the observations needed include windstress, directional waves, wave breaking, heat and moisture fluxes, stratification (temperature and salinity profiles), velocity profiles across the mixed layer and thermocline, spacing and orientation of windrows, and a measure of the strength of the circulation (e.g., surface rms velocities). These measurements span both the air/sea interface and the thermocline, and must be maintained continuously for many days to span storms and daily, tidal, and inertial cycles. In addition, the total power requirements exceed that comfortably supplied by batteries or local generation by wind or solar energy. It appears that FLIP is uniquely qualified as a platform from which the required range of measurements may all be made. Findings concerning the evolution and dynamics of Langmuir circulation that were facilitated by FLIP are reviewed and summarized, with emphasis on observations from 1990, 1995, and 2002. Spar Buoy Laboratories - Origins and Early Realizations Fred N. Spiess Scripps Institution of Oceanography, Marine Physical Laboratory, 8635 Discovery Way, La Jolla, CA 92037, United States At least as early as the 1950's there was a realization in the ocean research community of a need for stable platforms that could remain on station in the deep ocean for protracted periods. The 1959 report (Oceanography 1960-1970) of the NAS/NRC Committee on Oceanography includes the recommendation that a manned spar buoy laboratory should be among the new types of research platforms that should be built. By the late 1960s there were at least four craft of this type in operation: Cousteau's Bouee-Laboratoire, US Naval Ordnance Laboratory's SPAR, General Motors Defense Laboratory's POP, and the Marine Physical Laboratory's FLIP. All of these achieved their stability by using relatively deep draft spar buoy configurations. They differed, however, in their design philosophies and thus in their overall dimensions, general configurations, ultimate uses and longevity. FLIP has had the longest life of any of the four, for a variety of reasons, but primarily due to its versatility, as attested to in other papers in this session. This paper will discuss the origins, design considerations and careers of these and other similar craft. Langmuir Cells, Mixed Layer Evolution, and the Search for the Ekman Layer Robert A Weller Albert J Plueddemann Woods Hole Oceanographic Institution, Clark 204A MS29, Woods Hole, MA 02543, United States Making the accurate near-surface velocity measurements needed to both describe and understand the structure and variability of the oceanic mixed layer has challenged oceanographers for many years. Deployment of prototype Vector Measuring Current Meters (VMCMs) from the Research Platform FLIP in the 1970s produced some of the first velocity observations that resolved the vertical structure of upper ocean currents. When the relation between the time series of surface stress and upper ocean currents was examined, the phase angle between the wind-driven flow and the surface wind stress was found to depend on the frequency of the variability as predicted by Ekman theory, though the vertical structure of the mean flow did not in detail match an Ekman spiral. Subsequent cruises on FLIP identified the role of the surface buoyancy forcing in driving diurnal variations in the velocity and density structure of the upper ocean which, when averaged, modified the mean vertical structure of the wind-driven flow near the surface. The relationship of upper ocean structure and the evolution of the mixed layer to the combination wind stress and buoyancy forcing was analyzed and the resulting understanding used as the basis for developing the Price-Weller-Pinkel (PWP) one-dimensional mixed layer model. The model was found to often work well, replicating the temporal evolution of the upper ocean velocity and density structure. Built into the model physics is rapid vertical mixing within the homogenous part of the surface layer. It was hypothesized that the presence of Langmuir cells could provide such rapid vertical mixing; and further work from R/P FLIP turned to efforts to first determine if Langmuir cells could be observed, and later to study the role of Langmuir circulation in mixed layer dynamics. A combination of deployments of computer cards to mark surface flow patterns and in-situ acoustic Doppler measurements within the mixed layer showed that Langmuir cells could be visualized and observed. A VMCM modified to measure vertical (w) as well as horizontal velocities showed the circulation could be strong, with w in excess of 20 cm s-1. As techniques to image Langmuir Cells improved, it was found that the circulation was variable in time, with growth and decay modulated by a combination of wind stress and surface wave Stokes drift. Work remains to be done to better understand the dynamics of Langmuir circulation and other influences of surface waves on mixed layer dynamics and to include these processed in mixed layer models. |
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