RAPID 26N Report for RRS Discovery research Expedition DY186, 10th Dec 2024 to 19th Dec 2024

The purpose of RRS Discovery research expedition DY186 was to refurbish the Western Boundary of the RAPID 26°N array of moorings that span the Atlantic from the Bahamas to the Canary Islands. The expedition started in Fort Lauderdale, USA on Wednesday 10th December 2024 and ended on Thursday 19th December 2024 in Fort Lauderdale, USA. The moorings are part of a purposeful Atlantic wide array that observes the Atlantic Meridional Overturning Circulation and the associated heat and freshwater transports. The RAPID-MOCHAWBTS array is a joint UK- US programme. During DY186 moorings were serviced at sites: WB1, WB1L, WB2, WB2L, WBADCP, WBAL. Bottom pressure data was downloaded from WB3LZ. The bottom pressure lander WB2LZ was faulty and was recovered. Sites with suffix ‘L’ denote landers fitted with bottom pressure recorders. Moorings were equipped with instruments to measure temperature, conductivity and pressure, and a number of moorings were also equipped with current meters and/or oxygen sensors. CTD stations were conducted throughout the cruise for purposes of providing pre- and post-deployment calibrations for mooring instrumentation. Shipboard underway measurements were systematically logged, processed and calibrated, including: surface meteorology, 5m depth sea temperatures and salinities, water depth, and navigation. Water velocity profiles from 15 m to approximately 800 m depth were obtained using two vessel mounted Acoustic Doppler Current Profilers (one 75 kHz and one 150 kHz).