20 research outputs found
Toward Regional Characterizations of the Oceanic Internal Wavefield
Many major oceanographic internal wave observational programs of the last 4
decades are reanalyzed in order to characterize variability of the deep ocean
internal wavefield. The observations are discussed in the context of the
universal spectral model proposed by Garrett and Munk. The Garrett and Munk
model is a good description of wintertime conditions at Site-D on the
continental rise north of the Gulf Stream. Elsewhere and at other times,
significant deviations in terms of amplitude, separability of the 2-D vertical
wavenumber - frequency spectrum, and departure from the model's functional form
are noted. Subtle geographic patterns are apparent in deviations from the high
frequency and high vertical wavenumber power laws of the Garrett and Munk
spectrum. Moreover, such deviations tend to co-vary: whiter frequency spectra
are partnered with redder vertical wavenumber spectra. Attempts are made to
interpret the variability in terms of the interplay between generation,
propagation and nonlinearity using a statistical radiative balance equation.
This process frames major questions for future research with the insight that
such integrative studies could constrain both observationally and theoretically
based interpretations
Open-ocean deep convection explored in the Mediterranean
Open-ocean deep convection is a littleunderstood process occurring in winter in remote areas under hostile observation conditions, for example, in the Labrador and Greenland Seas and near the Antarctic continent. Deep convection is a crucial link in the âGreat Ocean Conveyor Beltâ [Broecker, 1991], transforming poleward flowing warm surface waters through atmosphere-oceaninteraction into cold equatorward flowing water masses. Understanding its physics, interannual variations, and role in the global thermohaline circulation is an important objective of climate change research.
In convection regions, drastic changes in water mass properties and distribution occur on scales of 10â100 km. These changes occur quickly and are difficult to observe with conventional oceanographic techniques. Apart from observing the development of the deep-mixed patch of homogeneous water itself, processes of interest are convective plumes on scales <1 km and vertical velocities of several cm sâ1 [Schott et al., 1994] that quickly mix water masses vertically, and instability processes at the rim of the convection region that expedite horizontal exchanges of convected and background water masses [e.g., Gascard, 1978]
Acoustic observations of heat content across the Mediterranean Sea
The ability to monitor the heat content of oceans over long distances is becoming increasingly important for understanding the role of oceans in climate change, for determining the variability of the state of the oceans, for operational ocean observing systems, and for studying large-scale ocean processes such as water-mass formation. Although the properties of the upper layers of the ocean can be routinely measured on large scales by satellite remote sensing (providing altimetric and infrared data) and with expendable probes dropped from commercial vessels, the deep interior of the ocean is more difficult to monitor. Ocean acoustic tomography1 is a promising technique for such applications, as it has the potential to provide systematic, instantaneous and repeated measurements of the ocean interior over large parts of an ocean basin. Here we demonstrate the capability of this technique for measuring the heat content across an entire (albeit small) ocean basinâthe western Mediterranean Sea