The RRS Discovery cruise 304 was conducted from 12 May to 6 June 2005 from and to Santa Cruz (Tenerife). The cruise was completed as part of the NERC founded RAPID programme to monitor the meridional overturning circulation at 26 N. The primary purpose was to service the eastern boundary and Mid-Atlantic Ridge part of the 26 N mooring array which had previously been serviced during the RRS Charles Darwin cruises 170 and 177. 12 moorings were successfully recovered, however two of the shallow eastern boundary moorings failed to release. Intense fishing activity at these sites is likely to be the cause. 12 mooring and four bottom pressure landers were re-deployed. Data from two bottom mounted inverted echosounders was uploaded via acoustic telemetry. A total of 10 CTD casts to calibrate the mooring sensors were carried out and 3 Argo floats (from the UK Met Office) were launched. The moored sensors are CTD loggers for the most part but also bottom pressure sensors, different types of current meters and inverted echosounders are used to determine the strength and structure of the meridional overturning circulation.

CTD stations on 20W line from 50N to 20N, following the old WOCE line A16N Physical measurements (CTDO and LADCP) and discrete samples for salt, oxygen, inorganic nutrients and alkalinity/inorganic carbon Underway ADCP, surface ocean measurements, surface meteorology measurements. Contribution to GO-SHIP sustained hydrography program. Partial repeat of a hydrographic line last occupied in 2003.

The aims of this cruise were to elucidate the processes responsible for controlling iodocarbon concentrations and provide a dataset that can be used to develop modelled estimates of iodocarbon sea-air fluxes in tropical Atlantic waters.

The main testable hypothesis of the proposed work is: Atmospheric inputs control rates of primary production and microbial diversity in oceanic waters where nutrients are limiting. The objectives of the project are to: 1. Obtain an improved temporal and spatial estimate of atmospheric dust inputs to the tropical N Atlantic through collections on a dedicated SOLAS process cruise. 2. Obtain an improved estimate of the seawater dissolution of N, P, Fe and Zn species from aerosol dust. 3. Determine the impact of atmospheric dust derived micronutrients on microbial community production and species diversity in the surface microlayer and underlying waters. In addition, researchers from the Archer/Geider group were on-board. The overall aim of their research was to determine the extent to which the photoprotective roles of DMSP and QAs influence their production rates in marine surface waters and hence, the production of their volatile breakdown products. The cruise objectives for this work were to: 1. relate DMSP and QAC concentrations to plankton community structure, light regime, photoinhibition, xanthophyll cycle and MAA accumulation in varying oceanic provinces and over diel cycles. 2. determine the potential for photoinhibition and DMSP/GBT turnover in natural phytoplankton in contrasting oceanic provinces. The cruise departed Tenerife on February 5, 2008, and we have conducted regular stations (typically 2 per day) along the cruise track. The track took us into the oligotrophic Atlantic waters, productive Cape Verde waters, and tropical waters with very high nitrogen fixation (judged initially from the Trichodesmium concentrations). The various researchers and groups have also started a range of biological experiments at different sites along the cruise track. We have encountered a major dust event in week 2, and then from week 3 of the cruise we encountered large amounts of dust. We have visited the TENATSO time series site near the Cape Verdes and have undertaken an extensive set of measurements there. We have collected the atmospheric dust for elemental analyses (at UEA and NOCS), and also to produce leachates which are used on board for biological experiments. We have undertaken sampling of the water column to analyse for dissolved and particulate metals, nutrients, dissolved organic matter, amino acids, hemes, thiols and phytochelatin synthase expression. In addition, nitrogen fixation measurements were undertaken, in tandem with nifh gene sampling. Nitrate uptake experiments have been conducted. Furthermore, bacterial phosphate uptake experiments have been undertaken using addition of collected dust. Halocarbon and DMS gas measurements have been conducted during the cruise. In addition, experiments have been undertaken by the Archer/Geider group on effects of high sun light exposure on DMS and GBT production. The cruise has been very successful with a minimum of lost time.

The objective of cruise JC103 was to service the moorings of the RAPID 26°N project that are deployed to monitor the Atlantic Meridional Overturning Circulation. For each mooring instruments were recovered, data were downloaded and instruments were redeployed. A number of CTDs were made to calibrate the instruments from the moorings. During passage from port of Spain to Nassau trial CTDs were completed in the waters of the Turks and Caicos Islands. After departing Nassau on 29th April work commenced on the western boundary sub-array comprising of moorings WBADCP, WBAL, WB1, WB2, WB2l, WB2h, WB4 and WB4L. The ship returned to Nassau on 6th May to disembark one person before sailing east once again. The final mooring of the wester sub-array was serviced on 8th May before continuing east to the mid-Atlantic Ridge (MAR) sub-array. Work on the MAR sub-array commenced on 13th May at mooring MAR0. The other moorings in this sub-array were MAR1, MAR1L, MAR2, MAR3 and MAR3L were all completed by 18th May. On the following day the NOG mooring was deployed and as the ship transited to the astern sub-array the first of 5 Argo floats was deployed on 21st May. The eastern boundary sub-array starts at EB1, which was serviced on 23rd May. Following this moorings at EB1L, EBHi, EBH1, EBH2, EBh3,EBh4 and EBH4L in the following days up until 31st May. A number of CTDs were completed form 31st may to 2nd June.

CD170 was a collaborative cruise with the Knorr cruise KN182_2. The latter cruise was conducted between 2 May 2005 and 26 May 2005. These cruises were completed as part of the UK Natural Environment Research Council (NERC) funded RAPID Programme and the US National Science Federation (NSF) funded MOCHA Programme to monitor the Atlantic Meridional Overturning Circulation at 26.5 degrees North. The primary purpose of both cruises was to service the 26.5 degrees North mooring array deployed in 2004 during RRS Discovery cruises D277 and D278. These cruises are the first annual refurbishment of this array.

These mooring operations were completed as a part of the United Kingdom Natural Environment Research Council (NERC) funded RAPID Programme to monitor the Atlantic Meridional Overturning Circulation at 26.5°N. The primary purpose of this cruise was to service the Eastern Boundary and Mid-Atlantic Ridge sections of the 26.5°N mooring array first deployed during RRS Discovery cruises D277 and D278 (SOC cruise report number 53), and serviced in 2005 during RRS Charles Darwin cruise CD177 (NOCS cruise report number 5), in 2006 on RRS Discovery cruise D304 (NOCS cruise report number 16) and FS Poseidon cruises P343 and P345 (NOCS cruise report number 28) and in 2007 on RRS Discovery cruise D324 (NOCS cruise report number 34). Cruise D334 started and finished in Tenerife, Spain and covered the Eastern Boundary and Mid-Atlantic Ridge moorings deployed on D324 and P343. This cruise was the fourth annual refurbishment of the Eastern Boundary and Mid-Atlantic Ridge sections of the mooring array. The array will be further refined and refurbished during subsequent years. The instruments deployed consist of a variety of current meters, bottom pressure recorders, CTD loggers and Inverted Echosounders, which, combined with time series measurements of the Florida Straits current and wind stress estimates, will be used to determine the strength and structure of the MOC at 26.5°N.

Cruise D344 was primarily used for the annual servicing of the eastern boundary and mid-Atlantic ridge moorings that form part of the RAPID-MOC mooring array across the North Atlantic at 26°N. In addition, the easternmost western boundary mooring, WB6, was serviced and the trial current meter mooring off the island of Abaco, WB-CM, was recovered. As the Discovery had made a faster passage than anticipated, a number of CTD stations were performed along 24° 30'N to augment the hydrography section scheduled to take place in January 2010. The instruments deployed on the RAPID-MOC array consist of bottom pressure recorders, CTD loggers, and current meters 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 26.5°N.