South Africa is at the confluence of three ocean systems: the upwelling of the Benguela on its west coast in the Atlantic Basin, the Mozambique Channel and the Agulhas Current on its east coast in the Indian Basin, and the Southern Ocean in the south.
For the past ten years, the LEMAR Trace Metals team has been working with South African colleagues from CSIR and Stellenbosch University to better understand trace element cycles in the Southern Ocean.
The Southern Ocean plays a disproportionate role in the absorption of anthropogenic CO2 and heat: observations and models indicate that south of 30°S, the Southern Ocean is responsible for the absorption of 40% of anthropogenic CO2 and 75% of ocean heat while it represents 30% of the total ocean surface. Without this ocean basin, atmospheric CO2 concentrations would be 50% higher than they are today. Trace metals, and iron in particular, partly control the efficiency of CO2 assimilation by phytoplankton, and therefore the global carbon cycle and the associated major elements (nitrogen, phosphorus, silicon, sulphur, etc.). In addition, trace and isotope elements make it possible to trace certain ocean processes, and ultimately to better understand the functioning of ocean ecosystems. The oceanic study of these trace elements is carried out on a global scale within the framework of the international GEOTRACES programme in which LEMAR scientists are strongly involved.
Oceanographic missions led by our South African colleagues (CSIR SOCCO and SOSCEX programme, Atlantic sector of the Southern Ocean), or planned as part of an international programme co-led by the LEMAR Trace Metals team (SWINGS, Indian sector of the Southern Ocean) allow us to take samples for trace metals, which are then analyzed on land at LEMAR by SF-ICP-MS (Ocean Spectrometry Cluster) or by voltammetry and at Stellenbosch University (SF-ICP-MS). The training of students is an important point of this project, with the recent signature of a thesis co-supervision agreement between UBO and Stellenbosch University (N. Van Horsten, 2017-2020).
These studies were initiated within the framework of LMI ICEMASA, in which LEMAR was a partner. Their funding and the mobility of students and researchers between France and South Africa are ensured both by South African (SANAP, PI: T. Mtshali), French (SeaTraM, Isblue, PI: E. Bucciarelli, SWINGS, ANR, co-PI: H. Planquette) and bilateral (Hubert Curien PROTEA Partnership: co-PI: T. Mtshali/E. Bucciarelli) projects.
SeaTraM (Seasonality of Trace Metal Distributions in the Southern Ocean): PI : E. Bucciarelli
PHC PROTEA : co-PI : E. Bucciarelli/T. Mtshali
SWINGS : South West INdian Geotraces Section : co-PI: H. Planquette/C. Jeandel