Heat Budget and Circulation Variability off Angola and Namibia, Cruise No. M131, October 7 - November 12, 2016, Recife (Brazil) - Walvis Bay (Namibia) (English)

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biogeochemical component in the eastern boundary upwelling region off Angola and Namibia. The program was an integral component of the EU collaborative project PREFACE ("Enhancing prediction of tropical Atlantic climate and its impacts") and the BMBF collaborative projects SACUS ("Southwest African Coastal Upwelling System and Benguela Niños") and RACE ("Regional Atlantic Circulation and Global Change"). The major aim of the cruise was (1) to determine the variability of eastern boundary current transport, water masses variability and wave propagation along the coastal wave guide; (2) to quantify physical processes controlling the mixedlayer heat and freshwater budget in the eastern boundary region, including the loss of heat due to turbulent mixing; and (3) to investigate upper-ocean water mass variability associated with the variability of the meridional overturning circulation along a transatlantic transect at about 11°S. Altogether, four moorings with instrumentation observing the variability of currents, hydrography and oxygen along the continental margin off Angola and Namibia were successfully recovered (two moorings could not be recovered) and five new moorings were deployed. Seven highresolution hydrographic and microstructure sections that included oxygen, nutrient, turbidity and particle measurements along selected international repeat lines in the eastern boundary current system were successfully completed, thereby advancing the understanding of seasonal and interannual variability of hydrography, mixed-layer properties and diapycnal heat flux. At two of these sections, autonomous measurement platforms (gliders) with microstructure probes or nutrient sensors were deployed sampling the sections at very high resolution for a period of up to six days. A high-resolution transatlantic hydrographic section was successfully completed using an underway sampling system. The observational program was complemented by sampling the sediment and measurements of the size distribution of aerosols.