The role of the ocean in the global atmospheric budget of acetone

Abstract

[1] Acetone is one of the most abundant carbonyl compounds in the atmosphere and it plays an important role in atmospheric chemistry. The role of the ocean in the global atmospheric acetone budget is highly uncertain, with past studies reaching opposite conclusions as to whether the ocean is a source or sink. Here we use a global 3-D chemical transport model (GEOS-Chem) simulation of atmospheric acetone to evaluate the role of air-sea exchange in the global budget. Inclusion of updated (slower) photolysis loss in the model means that a large net ocean source is not needed to explain observed acetone in marine air. We find that a simulation with a fixed seawater acetone concentration of 15 nM based on observations can reproduce the observed global patterns of atmospheric concentrations and air-sea fluxes. The Northern Hemisphere oceans are a net sink for acetone while the tropical oceans are a net source. On a global scale the ocean is in near-equilibrium with the atmosphere. Prescribing an ocean concentration of acetone as a boundary condition in the model assumes that ocean concentrations are controlled by internal production and loss, rather than by air-sea exchange. An implication is that the ocean plays a major role in controlling atmospheric acetone. This hypothesis needs to be tested by better quantification of oceanic acetone sources and sinks.

North American acetone sources determined from tall tower measurements and inverse modeling

“…Specifically, Blitz et al (2004) measured the quantum yields to be substantially lower than previously reported. Those findings imply an increased acetone lifetime, and reverse the relative importance of photolysis and OH oxidation as acetone sinks (Fischer et al, 2012). They also modify the importance of acetone as a precursor of HO x and PAN (Arnold et al, 2005), leading to less PAN in the Northern Hemisphere (especially in the upper troposphere), but more PAN in parts of the Southern Hemisphere.…”

“…Other terrestrial sources include biomass burning (Simpson et al, 2011) and direct anthropogenic emissions (Goldan et al, 1995;Goldstein and Schade, 2000;de Gouw et al, 2005). Globally, the oceans appear to be both a gross source and a gross sink for atmospheric acetone (Fischer et al, 2012); however, the magnitude and variability of the corresponding net flux is quite uncertain (de Reus et al, 2003;Williams et al, 2004;Lewis et al, 2005;Marandino et al, 2005;Sinha et al, 2007;Taddei et al, 2009;Fischer et al, 2012;Read et al, 2012;Sjostedt et al, 2012). Along with gross oceanic uptake, sinks of atmospheric acetone include photochemical oxidation by OH, photolysis, and deposition to land (Chatfield et al, 1987;McKeen et al, 1997;Gierczak et al, 1998;Blitz et al, 2004;Karl et al, 2010).…”

“…Along with gross oceanic uptake, sinks of atmospheric acetone include photochemical oxidation by OH, photolysis, and deposition to land (Chatfield et al, 1987;McKeen et al, 1997;Gierczak et al, 1998;Blitz et al, 2004;Karl et al, 2010). The mean tropospheric lifetime of acetone is estimated to be between 14 and 35 days (Jacob et al, 2002;Arnold et al, 2005;Fischer et al, 2012).…”

“…It affects atmospheric chemistry as an important source of hydrogen oxide radicals (HO x = OH + HO 2 ) in the upper troposphere (Jaeglé et al, 1997(Jaeglé et al, , 2001McKeen et al, 1997;Wennberg et al, 1998;Folkins and Chatfield, 2000;Arnold et al, 2005), and as a precursor of peroxyacetyl nitrate (PAN, CH 3 C(O)OONO 2 ), which is a key reservoir for nitrogen oxides (NO x = NO Acetone is emitted by terrestrial vegetation as a by-product of plant metabolic processes, such as cyanogenesis and acetoacetate decarboxylation Jardine et al, 2010), and during plant decay (de Gouw et al, 1999;Warneke et al, 1999). Recent estimates of the resulting biogenic flux to the atmosphere have ranged between 20 and 194 Tg a −1 (Singh et al, 2000(Singh et al, , 2004Jacob et al, 2002;Potter et al, 2003;Arnold et al, 2005;Lathière et al, 2006;Elias et al, 2011;Fischer et al, 2012;Guenther et al, 2012). The other principal source of atmospheric acetone is thought to be photochemical oxidation of precursor VOCs, including the predominantly anthropogenic 2-methyl alkanes (propane, isobutane, isopentane) as well as the biogenic 2-methyl-3-buten-2-ol (MBO) and monoterpenes (Alvarado et al, 1999;Reissell et al, 1999).…”

Impacts of bromine and iodine chemistry on tropospheric OH and HO<sub>2</sub>: comparing observations with box and global model perspectives

“…Photolysis rates use the FAST-JX scheme (Bian and Prather, 2002;Mao et al, 2010), with acetone photolysis rates updated by Fischer et al (2012). Stratospheric chemistry is based on LINOZ McLinden et al (2000) for O 3 and a linearised mechanism for other species as described by Murray et al (2012).…”