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.
A surface mooring was deployed at 38.5°S, 30°E, equatorward of the Agulhas Return Current (ARC), on 30 November 2010. Ship time was provided by the Agulhas and Somali Current Large Marine Ecosystem (ASCLME) project. The mooring carried a suite of sensors provided by the NOAA Pacific Marine Environmental Laboratory (PMEL) Ocean Climate Station (OCS) group led by M. Cronin, to monitor the radiative and turbulent air-sea heat fluxes, evaporative minus precipitation, and wind stress, surface and near surface temperature and salinity, and 15m currents. The mooring also carried a PMEL air-sea pCO2 system for monitoring the carbon flux. All measurements were telemetered to shore and made available in near-realtime on the project webpage: www.pmel.noaa.gov/OCS/ARC. The deployment was intended to last for a full year, but was shortened when buoy broke free from its anchor on 16 January 2011. It was later recovered by a French research ship in March 2011. Intellectual merit – The Agulhas Return Current has some of the largest air-sea heat, moisture, and carbon dioxide fluxes found in the entire Southern Hemisphere. Although this region has many similarities to other western boundary current extensions (e.g. Gulf Stream and Kuroshio Extension), the geometry of the system is fundamentally different: the African landmass terminates equatorward of the eastward flowing ARC. Measurements acquired by the buoy will ultimately lead to a better understanding of the regional and global heat balances and carbon cycle. Additional unexpected information was gained from the mooring break. Deep ocean currents, associated with a rare occurrence of an early retroflection of the Agulhas Current, are thought to be the cause of the break. These currents are being studied by members of SCOR Working Group #136 on the Climatic Importance of the Greater Agulhas System. Data from the drifting buoy also will be used to analyze the processes responsible for modifying the near-surface water as the Agulhas Return Current flows eastward, away from the African landmass. Broader impacts – The project will contribute to the NSF funded Agulhas Current Timeseries (ACT) experiment led by Dr. Beal (RSMAS). During its deployment, the mooring had 100% data return. Data were made publicly available in near-realtime through the project web pages. In addition to the analyses with the ACT data, the ARC flux mooring will be used to help assess operational weather prediction models, NWP reanalyses products, and satellite data used in climate studies. These assessments will likely lead to improved forecasts and reanalyses in the southern African and southwestern Indian Ocean region. This NSF-funded deployment will help lead to a longterm reference station in this region, a primary goal of the SCOR Working Group. A graduate student from University of Cape Town, Amy Weeber, participated in the deployment cruise and another UCT student, Amy Harding Goodman, will be using the data in her thesis work. The telemetered data were presented and used at the SCOR WG #136 workshop, held jointly with a Capacity Building workshop in Mauritius in April 2011. Two drifters, deployed on the ARC deployment cruise through the NOAA Adopt a Drifter Program, were adopted by 4th and 5th graders at Bryant Elementary School in Seattle. Dr. Meghan Cronin spoke with the students before and after the deployment and the presentations were provided to the Global Learning and Observations to Benefit the Environment (GLOBE) Africa.
