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Short Cruise Report, RV Maria S. Merian, Cruise MSM-64, Southampton – Galway – St. John's, 27 May – 23 Jun 2017Dr. Dagmar KiekeInstitut für UmweltphysikAG OzeanographieUniversität BremenOtto-Hahn-Allee 1D-28359 BremenGermanyTel.:Fax:email: 49-421-218-62154 [email protected] Cruise Report- RV Maria S. Merian, cruise MSM-64 Southampton/UK – Galway/Ireland – St. John's/Canada27 May – 23 Jun 2017Chief Scientist: Dr. Dagmar KiekeCaptain: Björn MaaßFigure 1. Track of RV MARIA S. MERIAN, cruise MSM-64, and locations of hydrographic profiles (red,numbers denote profile numbers), deployed moorings (yellow), inverted echo-sounders with pressuresensors (PIES, white), and Argo float deployments. Bathymetric contours are shown every 1000 m.1/12

Short Cruise Report, RV Maria S. Merian, Cruise MSM-64, Southampton – Galway – St. John's, 27 May – 23 Jun 20171. ObjectivesPhysical oceanographic measurements conducted during cruise MSM-64 contributed tothe scientific project RACE-II (“Regional Atlantic ChangE”), sub-project 1.2, funded by theGerman Ministry for Education and Research (BMBF). Scientific work during cruise MSM64 emphasized on a detailed mapping of water mass properties along 47 /48 N that wascombined with comprehensive measurements of the current system. In addition to shipbased observations, recovery and redeployment of deep-sea moorings at the western andeastern boundaries of the North Atlantic was conducted. These serve to determine theexport and import rates of subpolar or subtropical water masses in these regions. Variouslocations within the deep basins have been equipped (partly since 2006) with invertedecho-sounders carrying pressure sensors (PIES) that allow capturing variations of thedifferent branches of the North Atlantic Current (NAC). Together with the deep-seamoorings these form the oceanic long-term observatory NOAC (“North Atlantic Changes”)deployed along 47 /48 N. In combination with satellite altimetry the data serve toinvestigate the main components of the Atlantic Meridional Overturning Circulation(AMOC) at this latitude.In addition to this program, the two multibeam echo-sounder systems installed in thevessel’s hull (Kongsberg EM-712 and EM-122) were calibrated, and the required seaacceptance test for the EM-712 device was carried out by a technical-scientific team. Dueto this, the cruise was split into two separate legs (Southampton-Galway, Galway-St.John’s) with personnel being exchanged in Galway/Ireland on June 02nd, 2017.The primary objectives of cruise MSM-64 were:1) to capture the strength and the variability of the eastern boundary current off GobanSpur at the Irish shelf edge, which required the recovery and redeployment of deepsea moorings2) to recover data recorded by bottom-mounted PIES. This data serves to investigatethe strength and variability of the NAC crossing 47 /48 N in the NewfoundlandBasin and in the West European Basin3) to analyze the deep water export in the Deep Western Boundary Current (DWBC)across 47 N in the Newfoundland Basin as well as the export of Labrador SeaWater (LSW) through Flemish Pass by means of deep-sea moorings and ship2/12

Short Cruise Report, RV Maria S. Merian, Cruise MSM-64, Southampton – Galway – St. John's, 27 May – 23 Jun 2017based observations4) to capture the water column properties and identify changes in the components ofNorth Atlantic Deep Water5) to investigate the strength of the NAC from PIES and ship observations as the NACcrosses the Mid-Atlantic Ridge and enters the eastern basin.Due to the echo-sounder calibration and sea acceptance test added to cruise MSM-64, thecruise was longer than originally scheduled, but the available time to pursue the originalscientific program of cruise MSM-64 needed to be shortened. As further time was lost inthe eastern basin due to bad weather, the section along the western flank of the MidAtlantic Ridge could not be carried out, and thus objective 5 could not be met.Scientific tools comprised profiling of the entire water column using two lowered AcousticDoppler Current Profilers (LADCP) andaConductivity-Temperature-Depth-Oxygen(CTDO) unit, all attached to a carousel water sampler. Water sampling activities consistedof taking oxygen and salinity samples for the sake of CTDO-sensor calibration as well astaking samples for the analysis of anthropogenic tracers (chlorofluorocarbons) and carbonand oxygen isotopes ratios in seawater. Vessel-mounted ADCP measurements deliveredvelocity data of the upper water column. Seven Argo floats of type NKE ARVOR weredeployed along 47 /48 N and programmed to drift at a parking depth of 1000 dbar and tocycle between 2000 dbar and the sea surface every ten days. Work related to deployingand recovering deep-sea moorings concentrated on the boundary currents at the easternand western continental margins (Goban Spur at the Irish shelf break; eastern flank ofFlemish Cap; Flemish Pass). Telemetry, recovery, and (re-)deployment of inverted echosounders equipped with pressure sensors (PIES) focused on devices installed in the deepbasins along the 47 /48 N section.2. Narrative of cruise MSM-64RV MARIA S. MERIAN left the berth in Southampton, UK, on May 27th, 2017, at 09:30 UTC.When heading towards the southern exit of the English Channel, the scientific mission ofcruise MSM-64 started at 13:24 UTC the same day, when continuous logging of underwaydata was switched on. Course was set towards the Irish shelf break near Porcupine Bank,where a number of test stations were carried in deep and shallow water during May 28 th toMay 31st. These served to check the performance acoustic releases at depth, checks of3/12

Short Cruise Report, RV Maria S. Merian, Cruise MSM-64, Southampton – Galway – St. John's, 27 May – 23 Jun 2017the CTDO unit and the two LADCPs attached to the carousel water sampler. Furthermore,the water sample analysis devices were tested. During May 28th to May 31st the twomultibeam echo-sounding devices for shallow and deep water applications were calibratedalong a specific calibration track. Also, the sea acceptance test for the previously newlyinstalled EM-712 multibeam echo-sounder was successfully carried out. On June 02nd, RVMARIA S. MERIAN approached Galway/Ireland and, while lying on the roads in the GalwayBay, we exchanged scientists and technicians. After finishing this exchange, the originalscientific field program of cruise MSM-64 began, and we headed south towards GobanSpur at the Irish shelf break. Between June 03rd and June 09th, we recovered andredeployed mooring EB-1. As the recovery of the two moorings EB-2 and EB-3unfortunately failed, we could only redeploy mooring EB-3. Furthermore, hydrographiccasts including measurements of the oceanic current field were done, and the two easternPIES were exchanged. On June 09th/10th, a severe storm system required interruptingstation work and deviating from the original cruise track. After finishing station work in theWest European Basin, we crossed the Mid-Atlantic Ridge and continued station work inthe Newfoundland Basin. While approaching Flemish Cap, several PIES were recoveredand partly immediately redeployed. Data recorded by the devices over the past year wasretrieved via acoustic telemetry. Hydrographic station work was continued until reachingthe Deep Western Boundary Current east of Flemish Cap. There, we recovered the twomoorings BM-22 and BM-24 on June 17th 2017. Between June 18th and June 21st, wecarried out a densely space CTD section across the western flank of Flemish Cap,reinstalled the remaining PIES in the deep Newfoundland Basin and redeployed themoorings BM-22 and BM-24. On June 21st, we crossed Flemish Cap and continuedhydrographic station work along 47 N in Flemish Pass. On June 22nd, we recovered andsubsequently redeployed mooring BM-25.Continuous logging of underway data was stopped on June 23rd, 17:30 UTC, whichmarked the end of the scientific mission MSM-64 of RV MARIA S. MERIAN. The vesselarrived at the pilot station of St. John's and was finally towed at pier 17 at 19:00 UTC thesame day. In total, 91 hydrographic stations were carried out during cruise MSM-64.Seven Argo floats were deployed. Four deep-sea moorings were recovered, and five wereinstalled again. Seven PIES were recovered, and seven were deployed again, partlyupgraded with an additional currentmeter that turned these devices into C-PIES.4/12

Short Cruise Report, RV Maria S. Merian, Cruise MSM-64, Southampton – Galway – St. John's, 27 May – 23 Jun 2017AcknowledgementsWe would like to thank the master of the vessel, Björn Maaß, and his entire crew for theassistance and great support granted to us during the two legs of cruise MSM-64. Theprofessional and constructive cooperation between the different scientific teams and theship’s team, the hospitality experienced onboard the vessel, and the friendly workingenvironment is greatly appreciated.Further thanks go to Barbara Kozak at our home laboratory, the Federal Ministry forEducation and Research (BMBF), the German Research Foundation (DFG), the DFG’sPermanent Senate Commission on Oceanography, and the Control Station GermanResearch Vessels (Leitstelle Deutsche Forschungsschiffe) that provided the necessaryship time, funding, and support to pursue all scientific work.5/12

Short Cruise Report, RV Maria S. Merian, Cruise MSM-64, Southampton – Galway – St. John's, 27 May – 23 Jun 2017Table 1. Participants of cruise MSM-64NameInstituteField of ActivityLeg1. Kieke, Dagmar, Dr.IUPHB/MARUM chief scientist2. Altona, KarimIUPHB/MARUM sampling of tracers and isotopes23. Buinyi, AlekseiIUPHB/MARUM CTDO/LADCP watch, VMADCPprocessing1 2dos Santos Ferreira,4. Christian1 2MARUMmultibeam calibration15. Frahm, LauraUHHmultibeam calibration16. Garcia Quintana, YarisbelUEACTDO/LADCP watch1 27. Gerken, Jan8. Gerriets, Andrea9. Harbas, TeoIUPHB/MARUM CTDO/LADCP watchLDFBriese2multibeam calibration1superintendent1multibeam calibration110. Herland, AsmundKongsberg11. Köllner, ManuelaBSHmooring analysis1 212. Küper, SveaUHBoxygen analysis2Briesetechnical support113. Meyer, Christian14. Mirau, BastianIUPHB/MARUM moorings15. Nowitzki, HannahIUPHB/MARUM CTDO/LADCP watch, PIES analysis16. Pennelly, ClarkUEACTDO/LADCP watch17. Retsch, MatthiasMPIaerosol measurements18. Roessler, Achim, Dr.19. Schneehorst, Anja20. Steinfeldt, Reiner, Dr.21. Stokland, Gard22. Sültenfuß, Pia23. Uhde, Hans-Hermann24. Wischnewski, FannyIUPHB/MARUM ADCP and PIES data processingBSHmoorings, Argo float deploymentsIUPHB/MARUM CTD/O data processing, calibration,data analysis, salinometryKongsbergmultibeam calibrationIUPHB/MARUM sampling of tracers and isotopesBSHmoorings, Argo float deploymentIUPHB/MARUM CTDO/LADCP watch, LADCPprocessing6/121 221 221 21 21 2121 21 2