NW Africa: Cores, Traps, ROVs - Cruise No. M58 - April 16 - June 24, 2003 - Dakar (Senegal) - Ponta Delgada (Azores) (English)

With the three legs of R/V METEOR Cruise M58 the Research Center Ocean Margins (RCOM) continued an expedition campaign, which started in January 2003 off Southwest Africa. RCOM, sponsored by the Deutsche Forschungsgemeinschaft since 2001, is a joint venture of the University of Bremen, the Alfred-Wegener Institute for Polar and Marine Research, Bremerhaven, the Max-Planck Institute for Marine Microbiology, Bremen and the Senckenberg Institute, Wilhelmshaven. Long-term scientific objectives are basic and application oriented investigations of the transition zone between the oceans and continents. The continental margin off Northwest Africa is largely shaped by a complex interplay of sediment transport processes directed both downslope and along slope. Specifically south of26°N the considerably enhanced accumulation of sedimentary deposits originates from an intense marine productivity in the coastal upwelling regime. This results in widespread sediment movements and mass wasting events varying in style and velocity from slow motion slumps, where the original internal structures of the sediment column are mostly preserved, to debris flows, which typically display poor sorting, to tubidites transporting sediment material from the continental slopes far into the abyssal plains. Strong erosional bottom currents substantially contribute to the material transport and also to the development of large sediment drift bodies. Main aim of the first leg was a quantitative account of sediment transport processes from local scales to dimensions of 10 to 100 km2 extent. Individual episodes of massive sediment movements should be outlined in their temporal and spatial distribution and mass balances determined for the important constituents (organic and terrigenous components, carbonate). For this purpose, an integral representation and exact chronostratigraphic classification of the sedimentary sequences is an indispensable prerequisite to resolve the relation between mass wasting events and climate cycles, in particular sea level changes and glacial sea level low stands, as well as to identify and reconstruct the steering mechanisms of the sedimentation in the vicinity of high productivity regions. Central topic of the second leg were sedimentological investigations off NW Africa, where one of the worlds most important upwelling systems is located, additionally influenced by large amounts of Saharan dust deposits delivering nutrients into the ocean. Both processes are of fundamental importance for the particle formation in the ocean, considerably affect the biological and carbonate pumps and thus the global atmospheric CO2 budget. High accumulation rate sedimentary deposits found east of the Canary Islands and west of Dakhla and Cape Blanc should comprise appropriate climatic archives for high-resolution paleoceanographic studies aiming at adocumentation of very high rate climatic variations in the past. These rapid shifts of the climatic system as well as todays knowledge and rising concern about increasing anthropogenic influences attract more and more public interest to such investigations. Tests of various modern technological developments in marine science were the primary goal of the third leg. Initial activities also involved control and maintenance of sensor arrays at several moorings about 60 nm north of Gran Canaria. The second and main topic of this cruise were multiple deployments of the newly acquired 4000 m Work Class ROV (Remotely Operated Vehicle) QUEST in deep waters. This RCOM owned automated submersible was operatedfrom R/V METEOR for the first time.