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

Abstract

The air-sea fluxes of methanol and acetone were measured concurrently using a protontransfer-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 21 ). 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.

Seasonal variability in microbial methanol utilisation in coastal waters of the western English Channel

“…Recent direct flux measurements of methanol also demonstrated a consistent flux of methanol from the atmosphere to surface waters along a meridional transect of the remote Atlantic Ocean (Yang 15 et al 2013) and the Greenland Sea (Yang et al 2014b). Methanol is ubiquitous in atmospheric and marine environments where seawater concentrations have been reported ranging between <27 and 429 nM (Williams et al 2004, Kameyama et al 2010, Yang et al 2013, Yang et al 2014b, Beale et al 2015). An annual study in the western English Channel reported surface seawater methanol concentrations ranging between 16 and 20 78 nM over an annual cycle with no obvious seasonality (Beale et al 2015).…”

“…A net air-to-sea flux was first demonstrated in Northern temperate waters by Beale et al (2013). Recent direct flux measurements of methanol also demonstrated a consistent flux of methanol from the atmosphere to surface waters along a meridional transect of the remote Atlantic Ocean (Yang 15 et al 2013) and the Greenland Sea (Yang et al 2014b). Methanol is ubiquitous in atmospheric and marine environments where seawater concentrations have been reported ranging between <27 and 429 nM (Williams et al 2004, Kameyama et al 2010, Yang et al 2013, Yang et al 2014b, Beale et al 2015).…”

Measurement of wind profiles by motion-stabilised ship-borne Doppler lidar

“…We calculate attitude and velocity following the complimentary filtering approach of Edson et al (1998); this method is routinely used to motioncorrect ship-borne turbulence measurements (e.g. McGillis et al, 2001;Brooks, 2008;Norris et al, 2012;Yang et al, 2014;Drennan et al, 2014;Landwehr et al, 2015;Prytherch et al, 2015). The ship's mean horizontal velocity when underway can approach 6 m s −1 ; the wave-induced velocity per- Because the lidar Doppler velocities are 2 s averages, we use a corresponding 2 s averaged platform velocity to correct them; the standard deviation of the individual 10 Hz platform velocity measurements is also calculated as a quality control measure, in order to flag measurements for which the ship motion changes substantially during the lidar measurement interval and to provide a measure of the noise added to the Doppler winds by the ship motion.…”

Gradient flux measurements of sea-air DMS transfer during the Surface Ocean Aerosol Production (SOAP) experiment

“…This version of COARE removes the reliance on earlier ship measurements of COARE3.0 (Fairall et al, 2003) which may be subject to air-flow distortion effects, and provides better 25 agreement with independent observations (e.g. Yang et al, 2014). COARE3.5 was also used to compute u*, U10n (U10 adjusted to neutral stability), bulk sensible and latent heat fluxes.…”