Relationships of surface bromoform concentrations with mixed layer depth and salinity in the tropical oceans

摘要

Bromoform is ubiquitously present in the surface ocean because of its release from algae. Bromoform initiates catalytic ozone destruction in both the troposphere and stratosphere and may act as biogenic feedback in a changing climate. Thus, the temporal and spatial variation in the sea-air flux of bromoform is of great interest to atmospheric chemists. However, this is poorly characterized. Here we present a climatological approach to the sea surface bromoform concentration based on parameterizing remotely sensed variables. Significant parameters in capturing the variability were found to be chlorophyll-a concentrations, the mixed layer depth (with which bromoform is positively correlated), and salinity (negatively correlated). Climatology surface concentrations ranged from 4 to 90 ppt (～200-4500 pmol dm~(-3)), and average seasonal sea-air flux rapped from 10 to 100 nmol m~(-2) h~(-1). Using these fluxes, we obtained the total contribution of the tropical oceans to the global sea-air flux of bromoform to be 1.45 ± 0.9 Gmol a~(-1), representing about 75% of current global estimates.