Agulhas Return Current Surface Mooring Reference Station

University Of Washington, Seattle WA

Investigators

Abstract

A surface mooring will be deployed at 38.5°S, 30°E, equatorward of the Agulhas Return Current (ARC) in October 2010. The mooring will contribute to the global network of OceanSITES time series reference stations, and also to various process studies in the region, including the NSF funded Agulhas Current Time Series experiment led by Dr. Beal (RSMAS). The mooring will carry a suite of meteorological sensors to monitor the radiative and turbulent air-sea heat fluxes, evaporation minus precipitation, and wind stress. In addition, surface temperature and salinity and 15-m currents will be measured, and the mooring will carry an air-sea pCO2 system for monitoring the carbon flux. All measurements will be telemetered to shore and made available in near-real time. Intellectual merit: The Agulhas Return Current has some of the largest air-sea heat fluxes found in the entire Southern Hemisphere, and thus is a region of intense air-sea interaction. As with other basins, heat is carried poleward by the western boundary current (i.e. the Agulhas Current) and is released as the current retroflects and extends eastward into the South Indian Ocean basin. Although the mean fluxes are almost as large as in the western boundary current extensions (WBCE) of the Northern Hemisphere (Gulf Stream and Kuroshio Extension), the geometry of the African landmass is fundamentally different: it terminates at about 34°S, equatorward of the WBCE. The ARC reference station is needed to quantify the air-sea heat fluxes and understand the physics leading to the disequilibrium between the ocean and atmosphere, physics that also affect the ability of the ocean to uptake carbon dioxide in this region. Ultimately, these measurements will lead to a better understanding of the regional and global heat balance and the rate at which the ocean is absorbing carbon dioxide. Broader impacts: The mooring will contribute to the global network of OceanSITES time series reference stations. Data will be made publicly available in near-real time through the project web pages and through OceanSITES data centers. Partnerships have been formed with ASCLME, who will provide shiptime and help connect the project to African National Weather Services. Data from the ARC reference station mooring will be used to help assess operational weather prediction models as well as NWP re-analyses products used in climate studies. These assessments will likely lead to improved forecasts and re-analyses in the southern African and southwestern Indian Ocean region. The project will also contribute to various process studies, including the NSF funded ACT experiment led by Dr. Beal and other fieldwork coordinated by the SCOR Working Group #136 on the Climatic Importance of the Greater Agulhas System. The telemetered data will be presented and used at the next SCOR WG #136 workshop, to be held in East Africa in Spring 2011. The workshop will have a capacity building element, with travel support provided to invited scientists from developing nations.