The Northwest Tropical Atlantic Station (NTAS) : NTAS-14 mooring turnaround cruise report

Abstract

The Northwest Tropical Atlantic Station (NTAS) was established to address the need for accurate air-sea flux estimates and upper ocean measurements in a region with strong sea surface temperature anomalies and the likelihood of significant local air-sea interaction on interannual to decadal timescales. The approach is to maintain a surface mooring outfitted for meteorological and oceanographic measurements at a site near 15°N, 51°W by successive mooring turnarounds. These observations are used to investigate air-sea interaction processes related to climate variability. The NTAS Ocean Reference Station (ORS NTAS) is supported by the National Oceanic and Atmospheric Administration’s (NOAA) Climate Observation Program. This report documents recovery of the NTAS-13 mooring and deployment of the NTAS-14 mooring at the same site. Both moorings used Surlyn foam buoys as the surface element. These buoys were outfitted with two Air-Sea Interaction Meteorology (ASIMET) systems. Each system measures, records, and transmits via Argos satellite the surface meteorological variables necessary to compute air-sea fluxes of heat, moisture and momentum. The upper 160 m of the mooring line were outfitted with oceanographic sensors for the measurement of temperature, salinity and velocity. The mooring turnaround was done by the Upper Ocean Processes Group of the Woods Hole Oceanographic Institution (WHOI), onboard R/V Endeavor, Cruise EN549. The cruise took place between December 5 and 21 December 2014. The NTAS-14 mooring was deployed on December 13, and immediately followed by a 36-hour intercomparison period during which data from the buoy, telemetered through Argos satellite system, and the ship’s meteorological and oceanographic data were monitored. The NTAS-13 buoy had parted on September 23 and was recovered on October 28 while drifting freely near Martinique. The rest of the mooring, which had fallen to the seafloor was recovered during EN549, on December 17. This report describes these operations, as well as other work done on the cruise and some of the pre-cruise buoy preparations. Other operations during EN549 consisted in the recovery and deployment of Pressure Inverted Echo Sounders (PIES) and the acoustic download of data from PIES and subsurface moorings that are part of the Meridional Overturning Variability Experiment (MOVE) array. MOVE is designed to monitor the integrated deep meridional flow in the tropical North Atlantic. Two Argo floats were also deployed during the cruise on behalf of the Argo group at WHOI.