Exchanges Across Antarctic and Arctic Circumpolar Shelf Break Fronts:
Similarities, Differences and Impacts
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Submitted for Consideration as an IPY Program by iAnZone, a SCOR-Affiliated Organization
The Scientific Issue
The Antarctic continent and
the central basin of the
Though the Antarctic and
Despite considerable historical interest and a strong belief that these high latitude frontal systems play significant roles with respect to the global ocean climate, they are not well documented or quantitatively understood. Much of our current information is based on highly nonsynoptic data obtained from different regions during different years under the auspices of projects having differing goals. We have few observations adequate to assess the dynamics or seasonality of the frontal systems, or their interannual variability.
A Proposal, and Some Objectives
Significant advances in our
understanding of these two great frontal systems and of their roles in the
global ocean climate system will require an effort that can only be undertaken
through a concentrated and well organized multinational program. A program of this magnitude would be well
suited to the International Polar Year.
Indeed, it would require an international committment
in terms of funds and manpower that could probably only be obtained under the
auspices of such a project. We advocate
a bi-polar approach, and the iAnZone organization proposes
to develop, jointly with an interested Arctic group, a study of the Antarctic
● Dynamical understanding of coastal currents and associated slope fronts and their links to deep ocean overturning;
● Quantification of freshwater transports, including interannual fluctuations, around both polar basins;
● Determination of the sources and maintenance mechanisms for low salinity fractions;
● Assessment of the roles of circumpolar transports of heat (on and near the continental shelves) in melting sea ice and, in the Antarctic, melting ice shelves;
● Assessment of the roles of sea ice and ice shelves in determining transports, pathways and stratification of coastal and slope currents;
the regional origins and decays of fronts, for example, the major frontal discontinuity off the
● Assessment of the degree to which shelf-break currents are adequately represented in models; and
● Determination of the quantitative importance, to coupled climate models, of these boundary current systems.
The methods and technologies needed for a study like that envisaged here exist and are readily available. Much of the requisite new field data might be obtained during routine transits with little additional effort. The global scale ocean climate models exist and undergo continual adjustment and refinement. At a minimum, repeat observations of such routine and easily-measured ocean variables as temperature, conductivity and vertical current profiles should be obtained along routes that are routinely transitted either for their scientific value or en route to resupply permanent shore facilities. Moorings can be deployed in regions of high interest, and both subsurface and ice-mounted surface drifter can be deployed to yield information on currents, ice motions, and weather patterns. Drifter results are especially informative in evaluating results from numerical model predictions that involve ocean-ice interactions. Many such models exist at present. Perturbation studies might be used to assess the impacts on the ocean of varying ice cover. The possibilities here are virtually endless.
Some Logistical Issues
A breakdown of program component according to region will be essential, since no single group can be expected to cover such large regions. Much can be done through active coordination of existing programs and of preparation of proposals for new work. Ongoing or firmly planned projects that could make strong initial contributions include:
NSF-funded AnSlope study of impacts of the
● Ongoing work by various parties on the Weddell-Scotia Confluence region;
● The NSF-funded program for study of the Arctic Freshwater Cycle, a contributor to ASOF (the Arctic-Subarctic Ocean Flux project);
efforts, primarily at the
● The planned ISPOL winter drifting station along the western
● Ongoing potential for repeat data collection along
established oceanographic transects, such as that
The iAnZone organization is prepared to take on the initial organization of an effort such as outlined above. Ultimately, however, many other organizations would become involved and would probably include the CLIVAR Southern Ocean Panel, IPAB (for Antarctic buoys) and IABP (for Arctic buoys), AsPECT, ASOF, SEARCH, the Arctic Ocean Sciences Board, and the Polar Research Board. Planning efforts would be initiated upon approval of the program. An initial workshop relative to an Antarctic frontal study is planned by iAnZone for autumn 2004, and this would provide a suitable venue for initiating planning of a bipolar effort.