The overall aim of the UKSOLAS project DOGEE-SOLAS is the parameterization of air-sea gas exchange, which is a currently a major uncertainty in global modelling. RRS Discovery cruise D320 thus was primarily concerned with the measurement of air-sea gas transfer velocities and some of the important physical parameters that influence them through contributing to near surface turbulence, and other processes. In brief, specific cruise objectives were: 1. Determine open ocean gas transfer velocities through a number of dual-tracer releases (3He & SF6). 2. Investigate the role of surfactant in gas exchange through a targeted surfactant release in conjunction with (1). 3. Determine CO2 fluxes and transfer velocities, and make associated hydrographic and turbulence related measurements from autonomous ASIS (Air-Sea Interaction Spar) buoys. 4. Measure air-sea fluxes of CO2, sensible heat, latent heat and momentum using the AUTOFLUX automated sensor array 5. Measure underway, total gas tension, dissolved O2, and CO2 to obtain independent air-sea gas exchange estimates. 6. Make covariance and gas budgeting estimates of air-sea gas exchange using intelligent profiling Lagrangian floats. 7. Independently determine DMS fluxes and gas transfer velocities for comparison with CO2 to examine the role of gas solubility in gas transfer. 8. Deploy a spar buoy (NOC) for measurement of wave heights and bubble properties 9. Record and measure whitecap coverage and wave breaking coincident with the air-sea flux measurements using ship mounted cameras 10. Record key meteorological variables 11. Quantify flow distortion biases in the direct flux measurements via the use of established models. 12. Make biogas, surfactant and bacterial measurements in the surface microlayer and in the uppermost metres of the ocean using surface microlayer samplers, a remotely operated catamaran, and a near surface sampler. 13. Deploy an autonomous powered profiler (ASIP) for turbulence-related measurements in the mixed layer. Objectives 1-12 were all met. Unfortunately, due to mechanical failure and loss of ASIP, objective 13 was not realised.

The three key objectives of our original proposal were to test: 1. The hypothesis that mantle upwelling and melting is focused at the centres of slow spreading ridge segments and transposed by sub-horizontal flow away from there. 2. The hypothesis that plate accretion and separation mechanisms are fundamentally different in 'magma-starved' areas. 3. Mechanisms of detachment faulting and extensional strain localisation in the lower crust and upper mantle. We proposed to achieve these objectives by detailed surveying and sampling across an extensive region of magma-poor seafloor spreading around Fifteen Twenty Fracture Zone (FTFZ), coupled with microstructural, geochemical and palaeomagnetic analyses. TOBI deep-towed sidescan and magnetic data were to be obtained both to inform the choice of sampling sites and to aid in structural, lithological and geodynamic interpretations. We spent 29 days on the Mid-Atlantic Ridge (MAR) in the vicinity of 13 to 15N. We collected multibeam ship-based bathymetry, gravity and magnetic data and TOBI sidescan, magnetic and water-column data from a total area of about 8,000 km2. We recovered samples from 47 drill and dredge stations throughout the area, in support of the objectives.

Objectives: To quantify marine halocarbon emission variability and latitudinal variation, characterise in situ open ocean atmospheric reactive iodine latitudinal variability and characterise oxidative chemistry perturbation due to oceanic emission of halogens from the Mauritanian upwelling region. Rationale: Transecting from the UK through Biscay, south past the west coast of Africa, through the Mauritanian upwelling, to pass Cape Verde simultaneous to the intensive deployment at the UK SOLAS Observatory on Sao Vicente, the measurements made on Discovery cruise D319 are intended to provide a detailed latitudinal characterisation of marine atmospheric halogen chemistry. This will feed validation and constraint data to regional and global models in projects linked to RHaMBLe. In addition the cruise will address a number of key scientific questions required to determine the global importance of iodine chemistry and to further our understanding of the controls of halogen chemistry in the remote ocean: i) How heterogeneous are the direct halogen sources and on what scale is the heterogeneity - does the upwelling region produce more or less halogens than the 'background' region? ii) What are the relative contributions of I atoms to the remote MBL from I2 and organic iodine? iii) Is sufficient iodine released to the remote MBL to sustain aerosol nucleation or to significantly affect the ozone budget and free radical populations? Measurement Description: Measured species included a variety of halocarbons in both water column and atmosphere and atmospheric boundary layer measurements of I2, OIO and IO by Broadband Cavity Enhanced Absorption Spectroscopy (BBCEAS). A compact version of the FAGE system, developed for the FAAM BAe-146, was deployed to provide measurements of IO or OH / HO2, permitting direct assessment of RHS-induced changes in the oxidising environment through the upwelling region. A range of trace gas monitors was simultaneously deployed to measure O3 and NOx. Aerosol number and size distribution measurements from 3 nm to 20 micron diameter were also made by a range of mobility (SMPS) and optical instrumentation, (OPC and FSSP). Additional aerosol measurements were provided as part of the NERC-funded ACMME project (PI Allan). Measurements of pigments in the surface waters were made by HPLC. Prevailing meteorological conditions were used to direct the cruise in terms of geographical positioning and measurement interpretation, e.g. i) exploitation of any broad flow connection between Cape Verde and the ship to interpret measurements as process studies and ii) identification of in- and out-of-plume conditions to contrast chemistry influenced and uninfluenced by emissions from the upwelling region.

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.

Characterization of the Quaternary and Neogene sedimentary cover of the NW Atlantic shelf zone off Morocco and Quaternary deformations. This falls under the ANR ISIS project.

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 purpose was to service the Eastern Boundary and Mid-Atlantic ridge sections of the 26.5ºN mooring array. The Rapid-MOC array of moorings was deployed across the Atlantic to set up a pre-operational prototype system to continuously observe the Atlantic Meridional Overturning Circulation (MOC). This array will be further refined and refurbished during subsequent years as part of the Rapid-WATCH programme. The instrumentation deployed on the array consists of a variety of CTD loggers, current meters, bottom pressure recorders, and Inverted Echo-sounders, which, combined with time series measurements of the Florida Current and wind stress estimates, can be used to determine the strength and structure of the MOC.