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Forskning >> Atmosphere-Ocean Interaction

ATMOSPHERE-OCEAN INTERACTION

A strategic research project for the Geophysical Institute, University of Bergen, with the following objectives:

  • A: To improve the understanding of key atmosphere-ocean interaction processes at a fundamental level, to provide a better basis for their representation in models, and to enhance the accuracy of air-sea flux estimations;
  • B: To investigate the roles of atmosphere-ocean interaction versus horizontal atmospheric and oceanic mass and energy transports in determining
    interannual climate variability in the Atlantic-Arctic sector.

Project leader: Professor Peter M. Haugan

Scientific Coordinator: Dr. Alastair D. Jenkins

Funding: Research Council of Norway, project no. 175763/V30.


Project Summary

The project focuses on fundamental problems of atmosphere-ocean interaction, and provides the opportunity to conduct the following in-depth investigations within the following subprojects, during a 3-4 year time frame:
  1. Fundamental studies of atmosphere-ocean flux processes, comprising theoretical and basic process modelling studies of the air-sea interface;
  2. Interannual variability of surface fluxes and ocean heat storage, using atmosphere-ocean data sets from the past 50 years.
In order to make knowledge on these topics available to the scientific and broader community at local, national/regional and international levels, the project also incorporates:

     3. Atmosphere-ocean interaction seminars and information exchange.

Background

It is necessary for a proper understanding of the global atmosphere-ocean heat balance, and the spatial distribution and time evolution of greenhouse gases, to understand quantitatively and on a fundamental level the phenomena which influence air-sea fluxes of mass, momentum, and energy.  In particular, it is necessary to consider as a whole the air-sea interface and the boundary layers on both sides of it, and formulate in a self-consistent way the dynamics, and other physical and biogeochemical processess, so that continuity is maintained in the system description as one moves through the lower atmosphere down into the ocean.  In high latitude regions, gale and storm force winds, are likely to contribute in a major way to the fluxes, and the coupled system properties are not well understood under such conditions.  Steep and breaking waves are always present when the wind is strong, and so it is necessary to perform studies that take them into account. We will therefore study the hydrodynamical and physical effects of wave breaking, using suitable theoretical and ad hoc numerical models. The most important of these effects will be incorporated into a one-dimensional coupled model for the sea surface and atmospheric and oceanic boundary layers. The results from the theoretical and model investigations will be used to improve air-sea flux parameterisations for momentum, energy, moisture, heat, and mass, in regional and large-scale three-dimensional coupled models, and to identify critical parameters to be measured during field investigations.

The global radiation balance requires poleward heat transports of order 1012-1015 watts (W). The relative contributions from the atmosphere and oceans to this transport vary with latitude, with ocean transports dominating in low latitudes and atmosphere transports closer to the poles. The mean, seasonally-varying and geographically-varying atmospheric heat and moisture transports to high northern latitudes can be quantified from data and model-assisted analyses, but the accuracy is limited. Long-term mean estimates of oceanic heat transports through the ocean basins are also available, for net transport to the Nordic Seas and the Arctic Ocean), but very little is known about its interannual variability. Will perturbations in the oceanic heat transport be compensated by atmospheric heat transport as suggested by Bjerknes (1964)?  Will perturbations instead be compensated by changing albedo or radiation temperature, e.g. via sea ice extent or cloudiness?  In order to address these fundamental questions, which are crucial for regional climate and possibly also for global climate, a combination of insight into atmosphere and ocean dynamics as well as high latitude air-sea heat exchange is desirable.  Although reliable quantification of mean seasonally and geographically varying total surface heat exchange in the Nordic Seas and Arctic Ocean is difficult, recent advances in modelling tools, the availability of in situ and remote sensing data, and the usefulness of just a slight improvement of present large error bars, make the effort worthwhile. With such a basis, interannual variability can be obtained, which in combination with regional oceanic heat storage estimated from hydrography, will give a new basis for understanding interannual variability and propagation of anomalies.

The figure below shows links between Atmosphere-Ocean Interaction subprojects.  Results from fundamental studies of key air-sea processes and estimation of interannual flux variations will be used to improve and tune the parameterisation of these processes in regional and global-scale climate and operational models, with distribution of state-of-the-art information to the scientific community, via publications in journals and at conference, and by means of this web page, a series of seminars, and future planned workshops.





Links between subprojects

Project Description




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