Physical Oceanography for the Year 2000 (1987) / Chapter Skim
Currently Skimming:
'Recommended Research Initiatives'
'Recommended Research Initiatives'
Pages 4-28
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From page 4... ...
For example, what are the mechanisms, if any, by which the ocean influences year-to-year variations in the earth's climate? Does the ocean play a role in producing climate anomalies, such as droughts, floods, heat waves, or abnormal frosts?
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From page 5... ...
Ocean heat storage, transport, and transfer to the atmosphere are variable and may be the principal oceanic factors controlling these longer time scales of climate variability. Thus, long-range climate forecasting must take ocean processes into account.
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From page 6... ...
Climate variations with scales of approximately a decade and that produce important economic effects are known to exist but are less well documented than those with an annual time scale. There is evidence that the ocean plays a role in decadal climate variability, and proposals for large-scale ocean experiments to understand decadal variability have been made.
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From page 7... ...
It is the most obvious instance of interannual climate variability. Associated with the Southern Oscillation are sea surface temperature anomalies in the Pacific, Indian, and Atlantic oceans.
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From page 8... ...
Wintertime temperature anomalies are correlated with earlier atmospheric pressure anomalies over the South Pacific and with sea surface temperature anomalies in the equatorial Pacific Ocean. During the winter of 1982-1983, the strongest El Nino event ever observed took place.
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From page 9... ...
TOGA is principally an oceanographic program focused on the upper tropical ocean and overlying atmosphere. Its goals are to determine the nature of long-period fluctuations and their relationship to the global atmospheric circulation and to understand oceanographic and atmospheric processes that determine interannual variability.
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From page 10... ...
Complementary research activities in the Atlantic and Indian oceans also should be supported, although other nations may play the principal role there. World Ocean Circulation Experiment We must understand the global oceanic circulation to understand the ocean's role in maintaining the climate state and in influencing climate variability.
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From page 11... ...
Orbiting satellites give promise of regular global measurements of sea surface temperature, surface currents, and wind stress on the sea surface. If these observations are combined with subsurface measurements, it should be possible to develop a description of the ocean that, for the first time, would begin to be as complete as our description of the atmosphere.
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From page 12... ...
WOCE will have a satellite observation program. This will include missions to measure sea surface topography by radar altimetry and surface wind stress by scatterometry.
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From page 13... ...
Also included in WOCE will be strategically located jn situ instruments, for example, current meters and a global network of sea level tide gauge stations. Arrays of subsurface floats and surface drifters will contribute to the understanding of both surface currents and deep interior motions.
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From page 14... ...
to determine the interbasin exchanges in the global ocean circulation; 5. to obtain quantitative estimates of the large-scale exchange of buoyancy and chemical constituents between the upper boundary layer and the ocean interior by adequately describing the properties of the surface layer, including its horizontal mass transport and divergence; 6.
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From page 15... ...
intrusions from benthic boundary layers mixed by tides and breaking internal waves; (3) deep convective mixing in the wintertime mixed layers; (4)
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From page 16... ...
Observed internal wave spectra usually fit the universal spectrum to within a factor of three for frequencies significantly above the inertial frequency and less so in the near-inertial band. The variations are likely the dynamic signatures of the sources, sinks, and internal transfers of the internal wave field.
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From page 17... ...
Theoretical and observational evidence is emerging that the wind generates nearinertial frequency waves at large vertical scales and that internal waves and the mesoscale flow strongly interact. Classically, it has been assumed that the internal wave field dissipates its energy predominantly in the interior of the ocean, through small-scale turbulence.
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From page 18... ...
One of the more enigmatic products of the direct microstructure measurement programs is the suggestion of a low level of turbulent mixing in the ocean. Effective vertical diffusivities estimated from microstructure data are of the order of 0.1 cm2/s or less, a result consistent with predictions based on universal internal wave models.
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From page 19... ...
An effective diffusivity of the order of 1 cm^/s may then be possible in the weakly stratified abyssal ocean. A second school of thought suggests that boundary mixing is the dominant mechanism for cross-isopycnal fluxes, either by breaking internal waves or boundary layer turbulence.
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From page 20... ...
Warm core rings of the Gulf Stream have proven to be a good laboratory for studying this process. Recent work with rings has shown that the turbulence levels in actively cooled layers obey scaling laws similar to those of convective systems in the atmosphere, and that the heat and salt budgets of a cooling warm ring appear to require lateral mixing with surrounding waters.
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From page 21... ...
In such areas (e.g., the Caribbean Sea and the Mediterranean outflow) , the strong vertical mixing appears to cause rapid horizontal changes in water mass structure.
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From page 22... ...
The layers tend to be smaller than salt finger layers (a few meters versus a few tens of meters) , and more modest vertical diffusivities are calculated (on the order of 1 cm^/s versus 10 cm^/s for the finger steps)
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From page 23... ...
This will include further laboratory, theoretical, and modeling work, as well as large, well-coordinated field experiments using the most advanced mapping and microstructure instruments. Such field experiments could be served well by the use of Lagrangian techniques such as neutrally buoyant floats and tracers, both natural and introduced.
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From page 24... ...
Continental Shelf and Slope Circulation A regional approach is required to understand shelf and slope circulation regimes because the relative importance of the various physical processes that influence shelf circulation generally vary from region to region. Observations made with modern instrumentation during the last decade have resulted in much-improved descriptions of the dominant physical processes that influence circulation over continental shelves (e.g., Allen et al., 1983)
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From page 25... ...
The general subject of cross-shelf transports of, for example, mass, momentum, energy, salts, and nutrients remains poorly understood, though this is one of the most important aspects of shelf circulation. Cross-shelf surface Ekman transport driven by the alongshore wind stress is a fundamental element in dynamic models of the generation of wind-driven currents over the continental shelf, yet observations rarely show such a simple picture.
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From page 26... ...
Related to the dynamics of the mean and seasonal variation in alongshore flow are specific questions regarding the role in the alongshore momentum balance of the alongshore pressure gradient and bottom stress, two fundamental forces that are important in even the simplest theoretical and numerical models. Recent advances, both theoretical and experimental, in our understanding of the bottom boundary layer have changed our concept of the role of bottom friction.
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From page 27... ...
It seems clear that the main emphasis in the next phase of coastal physical oceanographic research will be the interaction of shelf circulation with water movements on the upper continental slope. The most vigorous kind of interaction occurs when a western boundary current occupies the upper slope -- as is the case off the South Atlantic Bight and (intermittently)
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From page 28... ...
Large anticyclonic eddies (warm core rings) impinge on the continental slope in the Middle Atlantic Bight and in the western Gulf of Mexico.
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