Global distribution and seasonal concentration change of methyl iodide in the atmosphere

Publication Type:

Journal Article


Journal of Geophysical Research: Atmospheres, Volume 113, Issue D18, p.D18311 (2008)





Air/sea constituent fluxes, Biosphere/atmosphere interactions, latitudinal distribution, methyl iodide, seasonal distribution, Troposphere: composition and chemistry, Troposphere: constituent transport and chemistry


We investigated seasonal variations in atmospheric CH3I at high, middle, and low latitudes in both hemispheres: at Alert (82.5°N, 62.5°W), over the northern and western Pacific Ocean (shipboard measurements); Cape Ochiishi (43.2°N, 145.5°E); Tsukuba (36.0°N, 140.1°E); Happo Ridge (36.7°N, 137.8°E); Hateruma Island (24.1°N, 123.8°E); San Cristobal Island (1.0°S, 89.4°W); Cape Grim (40.4°S, 144.6°E); and Syowa Station in Antarctica (68.5°S, 41.3°E) throughout 2004 and over an extended period of years at some sites. The highest median CH3I concentration was observed at San Cristobal Island, on the equator in the eastern Pacific, although no concentration elevation was found on or near the equator over the western Pacific. The lowest concentration was found in the Arctic and Antarctica, where they showed very similar seasonal variations that were clearly inversely correlated with variations in incident solar radiation. In the marine boundary air at midlatitude, the CH3I concentration was well correlated with surface seawater temperature (SST). Global atmospheric CH3I in wintertime was rather uniformly distributed (around 0.5 ppt) at middle and high latitudes.