FLEPVAR 2015 (Variability in Flemish Pass), Cruise No. MSM42 - May 2 - May 22, 2015 - Bermuda - St. John's (Canada) (English)

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Cruise MSM42 with RV MARIA S. MERIAN dealt with investigating the recent changes in the water mass structure and the oceanic circulation system in a narrow region focusing on the vicinity of Flemish Pass and Flemish Cap located at the western edge of the subpolar North Atlantic. Several densely spaced hydrographic sections were carried out across major pathways associated with the southward export of Labrador Sea Water (LSW), one of the important water masses that contribute to the cold and deep limb of the Atlantic Meridional Overturning Circulation (AMOC). Particular focus was on the LSW export through Flemish Pass, a meridional underwater passage located at about 47°W having a sill depth of about 1200 m. There, a deep-sea mooring (BM-25/3) carrying an Acoustic Doppler Current Profiler (ADCP) of type Long Ranger, capable to record the current velocity over a vertical distance of about 600 m, was successfully deployed. Work at hydrographic stations included conductivity-temperature-depth/oxygen (CTD/O) profiling and analysis of water samples to calibrate the corresponding conductivity and oxygen sensors. Furthermore, water samples were taken at selected stations and measured on board with respect to analyzing the oceanic content of anthropogenic tracers such as sulphurhexafluoride (SF6) and chlorofluorocarbon (component CFC-12) throughout the water column. Continuous and station-based data of the oceanic velocity field was obtained from lowered and vessel-mounted ADCP devices. Weather conditions were most of the time quite fair, sea ice or any icebergs were absent. Including two test-stations, 160 CTD/O- and ADCP-stations have been carried out in total, delivering a valuable high-quality set of physical oceanographic data.