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Methyl bromide: ocean sources, ocean sinks, and climate sensitivity.
A D Anbar1, Y L Yung, F P Chavez
1Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, USA.
Global Biogeochemical Cycles
|March 1, 1996
Summary
Oceans significantly impact atmospheric methyl bromide (CH3Br), a key ozone-depleting substance. Marine CH3Br production, linked to primary productivity, is sensitive to temperature, suggesting climate change could alter atmospheric CH3Br levels.
Area of Science:
- Geochemistry
- Atmospheric Chemistry
- Oceanography
Background:
- Methyl bromide (CH3Br) is a major carrier of ozone-destroying bromine to the stratosphere.
- Oceanic production of CH3Br is comparable to atmospheric inputs, but its mechanism and flux are poorly understood.
- CH3Br consumption in seawater is highly temperature-sensitive, influencing ocean-atmosphere exchange.
Purpose of the Study:
- To quantify the effects of temperature and marine productivity on oceanic methyl bromide (CH3Br) flux.
- To reconcile discrepancies in previous marine CH3Br concentration measurements.
- To assess the sensitivity of atmospheric CH3Br to climate change.
Main Methods:
- Developed a steady-state mass balance model for CH3Br.
- Scaled CH3Br production rates with seawater chlorophyll content.
- Analyzed latitudinal variations in marine CH3Br concentrations.
Main Results:
- The model successfully reproduced observed latitudinal variations in marine CH3Br.
- CH3Br production correlates with primary production, explaining discrepancies in prior studies.
- The open ocean appears to be a small net sink for atmospheric CH3Br, with the Southern Ocean as a potential source.
Conclusions:
- Oceanic CH3Br exchange is highly sensitive to temperature and marine productivity.
- Climate-induced variations in CH3Br can exceed those from anthropogenic sources.
- Understanding marine CH3Br production is crucial for assessing ozone depletion and climate change impacts.