Climate of Antarctica and the Southern Ocean

Project Description
Short Title: CASO
Project URL: http://www.clivar.org/organization/southern/CASO/
Proposal URL:http://classic.ipy.org/development/eoi/proposal-details.php?id=132

CASO provides an integrated and interdisciplinary approach to understanding the role of Antarctica and the Southern Ocean in past, present and future climate during the IPY 2007-2008 (see http://www.clivar.org/organization/southern/documents/SOIPY.pdf for a more complete description of the CASO science plan).

CASO is organised into five themes:
1. Antarctica and the Southern Ocean in the global water cycle
2. Southern hemisphere teleconnections
3. Climate processes at the Antarctic continental margin
4. Climate ecosystem biogeochemistry interactions in the Southern Ocean
5. Records of past Antarctic climate variability and change

This proposal describes IPY activities grouped in the Antarctic Ocean Circulation cluster of EOIs that contribute to the goals of CASO.

Objectives:
1. To obtain a synoptic circumpolar snapshot of the physical environment of the Southern Ocean (collaboration with other IPY activities will extend the snapshot to include biogeochemistry, ecology, and biodiversity).
2. To enhance understanding of the role of the Southern Ocean in past, present and future climate, including connections between the zonal and meridional circulation of the Southern Ocean, water mass transformation, atmospheric variability, ocean-cryosphere interactions, physical-biogeochemical-ecological linkages, and teleconnections between polar and lower latitudes.

Outcomes/Deliverables:
1. Improved climate predictions, from models that incorporate a better understanding of southern polar processes.
2. Proof of concept of a viable, cost-effective, sustained observing system for the southern polar regions (including ocean, atmosphere and cryosphere).
3. A baseline for the assessment of future change.

Major field programs:
1. A circumpolar array of full-depth multi-disciplinary hydrographic sections and XBT/XCTD sections, extending from the Antarctic continent northward across the Antarctic Circumpolar Current, including key water mass formation regions (EOIs 109, 173, 225 284, 599, 730, 770, 806, 924, 51, 350, 283, 584, 911, 271, 440, 596).
2. An enhanced circumpolar array of sea ice drifters, measuring a range of ice, ocean and atmosphere parameters (108, 109, 51).
3. Profiling floats deployed throughout the Southern Ocean, including acoustically-tracked floats in ice-covered areas (109, 180, 599, 485, 596).
4. Current meter moorings to provide time series of ocean currents and water mass properties at key passages, in centres of action of dominant modes of variability, and in areas of bottom water formation and export (109, 173, 225, 599, 604, 806, 51, 596).
5. Environmental sensors deployed on marine mammals (77, 596).
6. Direct measurements of diapycnal and isopycnal mixing rates in the Southern Ocean (183).
7. Analysis of ice cores, sediment cores and deep corals to extend observations of Southern Ocean variability back beyond the instrumental era (109, 806, 51).
8. Bottom pressure gauges will be used near Drake Passage to monitor ocean currents, validate tidal models, and improve regional corrections to satellite altimeter products (567, 580).
9. Automatic weather stations, flux measurements in the boundary layer and drifters to measure atmospheric variability (pressure, winds, heat and freshwater flux) (108, 109).

The observations will be integrated closely with modelling studies using a variety of approaches (coupled climate models; high resolution ocean-ice models; atmospheric models; tidal models; Lagrangian diagnostics; 320, 284, 567, 580, 590,117).