Atmospheric deposition of methanol over the Atlantic Ocean

In the troposphere, methanol (CH3OH) is present ubiquitously and second in abundance among organic gases after methane. In the surface ocean, methanol represents a supply of energy and carbon for marine microbes. Here we report direct measurements of air-sea methanol transfer along a similar to 10,000-km north-south transect of the Atlantic. The flux of methanol was consistently from the atmosphere to the ocean. Constrained by the aerodynamic limit and measured rate of air-sea sensible heat exchange, methanol transfer resembles a one-way depositional process, which suggests dissolved methanol concentrations near the water surface that are lower than what were measured at similar to 5 m depth, for reasons currently unknown. We estimate the global oceanic uptake of methanol and examine the lifetimes of this compound in the lower atmosphere and upper ocean with respect to gas exchange. We also constrain the molecular diffusional resistance above the ocean surface-an important term for improving air-sea gas exchange models.

Monitoring of a quasi-stationary eddy in the Bay of Biscay by means of satellite, in situ and model results

The presence of a quasi-stationary anticyclonic eddy within the southeastern Bay of Biscay (centred around 44°30′N-4°W) has been reported on various occasions in the bibliography. The analysis made in this study for the period 2003–2010, by using in situ and remote sensing measurements and model results shows that this mesoscale coherent structure is present almost every year from the end of winter-beginning of spring, to the beginning of fall. During this period it remains in an area limited to the east by the Landes Plateau, to the west by Le Danois Bank and Torrelavega canyon and to the northwest by the Jovellanos seamount. All the observations and analysis made in this contribution, suggest that this structure is generated between Capbreton and Torrelavega canyons. Detailed monitoring from in situ and remote sensing data of an anticyclonic quasi-stationary eddy, in 2008, shows the origin of this structure from a warm water current located around 43°42′N-3°30′W in mid-January. This coherent structure is monitored until August around the same area, where it has a marked influence on the Sea Level Anomaly, Sea Surface Temperature and surface Chlorophyll-a concentration. An eddy tracking method, applied to the outputs of a numerical model, shows that the model is able to reproduce this type of eddy, with similar 2D characteristics and lifetimes to that suggested by the observations and previous works. This is the case, for instance, of the simulated MAY04 eddy, which was generated in May 2004 around Torrelavega canyon and remained quasi-stationary in the area for 4 months. The diameter of this eddy ranged from 40 to 60 km, its azimuthal velocity was less than 20 cm s−1, its vertical extension reached 3000–3500 m depth during April and May and it was observed to interact with other coherent structures.

Monitoring of a quasi-stationary eddy in the Bay of Biscay by means of satellite, in situ and model results

The presence of a quasi-stationary anticyclonic eddy within the southeastern Bay of Biscay (centred around 44°30′N-4°W) has been reported on various occasions in the bibliography. The analysis made in this study for the period 2003–2010, by using in situ and remote sensing measurements and model results shows that this mesoscale coherent structure is present almost every year from the end of winter-beginning of spring, to the beginning of fall. During this period it remains in an area limited to the east by the Landes Plateau, to the west by Le Danois Bank and Torrelavega canyon and to the northwest by the Jovellanos seamount. All the observations and analysis made in this contribution, suggest that this structure is generated between Capbreton and Torrelavega canyons. Detailed monitoring from in situ and remote sensing data of an anticyclonic quasi-stationary eddy, in 2008, shows the origin of this structure from a warm water current located around 43°42′N-3°30′W in mid-January. This coherent structure is monitored until August around the same area, where it has a marked influence on the Sea Level Anomaly, Sea Surface Temperature and surface Chlorophyll-a concentration. An eddy tracking method, applied to the outputs of a numerical model, shows that the model is able to reproduce this type of eddy, with similar 2D characteristics and lifetimes to that suggested by the observations and previous works. This is the case, for instance, of the simulated MAY04 eddy, which was generated in May 2004 around Torrelavega canyon and remained quasi-stationary in the area for 4 months. The diameter of this eddy ranged from 40 to 60 km, its azimuthal velocity was less than 20 cm s−1, its vertical extension reached 3000–3500 m depth during April and May and it was observed to interact with other coherent structures.

Air-sea exchange of methanol and acetone during HiWinGS: Estimation of air phase, water phase gas transfer velocities

The air-sea fluxes of methanol and acetone were measured concurrently using a proton-transfer-reaction mass spectrometer (PTR-MS) with the eddy covariance (EC) technique during the High Wind Gas Exchange Study (HiWinGS) in 2013. The seawater concentrations of these compounds were also measured twice daily with the same PTR-MS coupled to a membrane inlet. Dissolved concentrations near the surface ranged from 7 to 28 nM for methanol and from 3 to 9 nM for acetone. Both gases were consistently transported from the atmosphere to the ocean as a result of their low sea surface saturations. The largest influxes were observed in regions of high atmospheric concentrations and strong winds (up to 25 m s(-1)). Comparison of the total air-sea transfer velocity of these two gases (K-a), along with the in situ sensible heat transfer rate, allows us to constrain the individual gas transfer velocity in the air phase (k(a)) and water phase (k(w)). Among existing parameterizations, the scaling of k(a) from the COARE model is the most consistent with our observations. The k(w) we estimated is comparable to the tangential (shear driven) transfer velocity previously determined from measurements of dimethyl sulfide. Lastly, we estimate the wet deposition of methanol and acetone in our study region and evaluate the lifetimes of these compounds in the surface ocean and lower atmosphere with respect to total (dry plus wet) atmospheric deposition.