RRS Charles Darwin Cruise CD177, 12-29 Nov 2005. RAPID Mooring Cruise Report

This report describes mooring operations and underway measurements conducted during RRS Charles Darwin Cruise CD177. Cruise CD177 was conducted between 12 November 2005 and 29 November 2005. The first part of the cruise consisted of a transit from Falmouth, UK to Santa Cruz de Tenerife, Tenerife with mooring preparation conducted on this leg. Further scientific staff joined in Santa Cruz de Tenerife for the second leg that started on the 19 November. The cruise finished in Tenerife on the 29 November. This cruise was completed as part of the United Kingdom Natural Environment Research Council (NERC) funded RAPID Programme to monitor the Atlantic Meridional Overturning Circulation at 26.5ºN. The primary purposes of this cruise were to service the two key moorings (EB1 and EB2) on the eastern boundary of the 26.5ºN mooring array and to deploy two Pressure Inverted Echosounders (PIES). The array was first deployed in 2004 during RRS Discovery cruises D277 and D278 (Southampton Oceanography Centre Cruise Report No. 53) in order to set up a pre-operational prototype system to continuously observe the Atlantic Meridional Overturning Circulation (MOC). It was subsequently serviced on RRS Charles Darwin cruise CD170 and RV Knorr cruise KN182-2 (both covered in National Oceanography Centre Southampton Cruise Report No. 2). The array will be further refined and refurbished during subsequent years. This cruise was planned in response to mooring losses suffered in the first year of the 26.5ºN array deployment. The two key eastern boundary moorings were subjected to damage through suspected fishing activity causing the loss of data above 1200m at the eastern boundary. To reduce the risk of data loss we plan to service the two key moorings on a six-monthly cycle. Instruments deployed on the array consists of a variety of current meters, bottom pressure recorders and CTD loggers which, combined with time series measurements of the Florida Channel Current and wind stress estimates, will be used to determine the strength and structure of the MOC at 26.5ºN. (http://www.noc.soton.ac.uk/rapidmoc)