New Constraints on Terrestrial and Oceanic Sources of

New Constraints on Terrestrial and Oceanic Sources of Atmospheric Methanol Dylan Millet Harvard University with D. Jacob (Harvard), D. Blake (UCI), T. Custer and J. Williams (MPI), J. de Gouw, C. Warneke, and J. Holloway (NOAA), T. Karl (NCAR), H. Singh (NASA), B. Sive (UNH) Thanks to: NASA Atmospheric Chemistry Program NOAA C&GC Postdoctoral Fellowship Program American Geophysical Union Fall Meeting 2007

Methanol: The Most Abundant Non-Methane Organic Gas Atmospheric Production CH 4 Oxidation by OH CH 3 OH Burden: ~4 Tg Lifetime: 5 -10 d Source of CO, HCHO, O 3 Sink of OH Wet Dep Ocean Exchange Plant Growth Plant Decay Biomass Urban Burning Emissions ? Dry Dep (Land)

Aircraft and Surface Measurements Used to Constrain Methanol Sources & Sinks Interpret with: GEOS-Chem 3 D 3 D model of atmospheric New plot with all obs chemistry SURFACE OOMPH, NEAQS-2 K 2, Kinterbish, Tennessee, UMBS, Trinidad Head, Duke Forest, Chebogue Pt, Appledore Isl. , Thompson Farm, Rondônia, Amazonas AIRCRAFT PEM-TB, INTEX-A/B, MILAGRO, ITCT-2 K 2/2 K 4, TOPSE, LBA/CLAIRE, TROFFEE, TEXAQS-II

Methanol: The Most Abundant Non-Methane Organic Gas Atmospheric Production CH 4 Oxidation by OH CH 3 OH Source of CO, HCHO, O 3 Burden: ~4 Tg Lifetime: 5 -10 d Wet Dep Ocean Exchange Plant Growth Plant Decay Biomass Urban Burning Emissions Dry Dep (Land)

Ocean Mixed Layer (OML): Source + Sink for Atmospheric Methanol Previous work: · Assume constant OML undersaturation · OML a small net sink Assumes air-sea exchange controls [CH 3 OH]OML

Ocean Mixed Layer (OML): Source + Sink for Atmospheric Methanol Recent OML Measurements imply a large methanol reservoir (20× that of the atmosphere) Short lifetime requires large OML source (~8 E 3 Tg/y) CH 3 OH 120 ± 50 n. M [Williams et al. , 2004] 66 Tg Biotic consumption ~3 d [Heikes et al. , 2002]

Ocean Mixed Layer (OML): Source + Sink for Atmospheric Methanol Recent OML Measurements imply a large methanol reservoir (20× that of the atmosphere) OML ventilation weeks-months 100 Tg/y Short lifetime requires large OML source (~8 E 3 Tg/y) Transfer from atmosphere insufficient to balance loss Large in-situ biological source implied CH 3 OH 120 ± 50 n. M [Williams et al. , 2004] 66 Tg Biological production Biotic consumption ~3 d [Heikes et al. , 2002]

Ocean Mixed Layer (OML): Source + Sink for Atmospheric Methanol Recent OML Measurements imply a large methanol reservoir (20× that of the atmosphere) OML ventilation weeks-months 100 Tg/y CH 3 OH 120 ± 50 n. M [Williams et al. , 2004] 66 Tg Biological production Biotic consumption ~3 d [Heikes et al. , 2002] Short lifetime requires large OML source (~8 E 3 Tg/y) Transfer from atmosphere insufficient to balance loss Large in-situ biological source implied Ocean emission, uptake: independent terms in atmospheric budget

Ocean Emission and Uptake of Atmospheric Methanol Calculate ocean source & sink terms independently · On basis of measured OML concentrations Ocean Emission Ocean Uptake 100 Tg y-1 85 Tg y-1 Marine biosphere: large source of =11 d Comparable to oxidation by OH atmospheric methanol Comparable to terrestrial biota Net Flux

New Air-Sea Flux Parameterization Generally Consistent with Atmospheric Observations Measured vs. modeled methanol concentrations over the S. Atlantic OOMPH 2007 Methanol profiles over the Pacific Measured Modeled

Methanol Emissions from the Terrestrial Biosphere All plants make methanol · Produced during cell growth · Emitted from leaves ~ f(T, hν) · E = 0. 11% × NPP [Galbally & Kirstine, 2002] Aircraft Measurements Reveal Overestimate of Plant Growth Source Vertical Profiles over N. America Simulated summer methanol concentrations in surface air [ppb] Broad-scale inflow to W. US well simulated Measured Modeled 2× BL overestimate during summer Only explained by overestimate of plant growth source

Bias Correlates Spatially with Regions of High Broadleaf Tree & Crop Coverage Boundary Layer Methanol Concentrations [ppb] Modeled Observed Modeled - Measured Removal of bias requires: 4 x reduction of broadleaf tree + crop emissions, or 2 x reduction of emissions from all terrestrial plants MDVD 2 vegetation coverage [Guenther et al. , 2006]

Reduced Biogenic Source Yields Better Agreement over North America and Tropical South America Vertical Profiles over N. America Amazon Boundary Layer Measured Base case 2× (all plants) 4× (bdlf trees + crops) Base case ¯ 2× ¯ 4× all plants bdlf trees, crops Measured Both optimizations of comparable quality Best estimate of global terrestrial biogenic source: 80 Tg/y (vs. 145 Tg/y base case)

Importance of Biogenic vs. Anthropogenic Sources Methanol strongly correlated with CO despite lack of large anthro. source Aircraft measurements over N. America during summer Model captures correlation, slope (with independent constraints on CO) Measured Base case 2× (all plants) 4× (bdlf trees + crops)

Updated Global Budget of Atmospheric Methanol Sources Sinks 85 Tg/y 80 Tg/y 101 Tg/y 88 Tg/y 37 Tg/y 23 Tg/y 40 Tg/y 13 Tg/y Atmospheric lifetime: 4. 7 days 12 Tg/y 5 Tg/y 108 molec/cm 2/s