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OZONE DEPLETION AND THE AIR-SEA EXCHANGE OF GREENHOUSE AND CHEMICALLY REACTIVE TRACE GASES
Citation:
Erickson, D. J., R G. Zepp, AND E. Atlas. OZONE DEPLETION AND THE AIR-SEA EXCHANGE OF GREENHOUSE AND CHEMICALLY REACTIVE TRACE GASES. CHEMOSPHERE - GLOBAL CHANGE SCIENCE 2(2):137-149, (2000).
Impact/Purpose:
The overall objective of this task is to develop quantitative relationships for assessing the vulnerability of aquatic resources to global change. The task will contribute experimental and modeling tools for assessments of the interactions of global climate and UV changes with coral reefs and selected watersheds and estuaries in the U.S. These activities are contributing primarily to two APGs in the ecosystems component of the Global Change Research Multiyear Plan: the 2006 APG (APG 3) on building the capacity to assess global change impacts on coastal aquatic ecosystems, including coral reefs and estuaries and the 2004 APG (APG 2) on building capacity to assess and respond to global change impacts on selected watersheds. One major task objective is to assess interactions of global warming and UV exposure that are contributing to the observed coral bleaching and disease. Our lab is working with scientists at the NHEERL Gulf Ecology Lab to characterize UV exposure and effects at several coral reef sites. Other research in this task is examining the interactions between UV-induced breakdown of refractory organic matter in estuaries and coastal areas that enhance UV penetration into the water and concurrently form biologically-labile nitrogen-, phosphorus- and carbon-containing substances that stimulate productivity and microbial activity. This task also involves research in central Brazil that is part of the Large Scale Biosphere Atmosphere Experiment (LBA). The objectives of this project are to assess the impacts of land use and climatic changes on soil nutrient cycles and microbiota, trace gas exchange and water quality in the Brazilian cerrado. This work involves a close collaboration between EPA and a group of scientists from the Department of Ecology, University of Brasilia, Brazil. Other objectives of this task are to assess the interactions of land use and climate changes with the ecological functioning of streams in watersheds of the Piedmont region of the southestern U.S.
Description:
One of the most important aspects of global change is that of stratospheric ozone depletion and the resulting increase in UV radiation reaching the surface of the Earth. Some 70% of the Earth surface is covered by water containing an extremely complicated milieu of organic and inorganic chemical species. The photochemical production and transformation of various
greenhouse and chemically reactive gases in the ocean has been a focus of much study over the last century. We assess the implications of increased UV radiation on aquatic and marine boundary layer biogeochemistry with a focus on trace gases that exchange between the ocean and the atmosphere. CO2, DMS, CO, OCS, CH4, N2O, non-methane hydrocarbons (NMHCs) and organohalogens are considered within the context of changing surface ocean UV fluxes and various feedbacks upon the integrated climate system. Links between the upper ocean photochemical environment and the lower atmosphere are stressed. Once in the atmosphere, these gases each play a different role in modulating several aspects of atmospheric chemistry and by implication atmospheric circulation and climate dynamics such as precipitation patterns, surface temperatures and surface atmosphere substance exchange. We augment the conceptual models proposed with new observational data on surface ocean concentrations from the southern hemisphere obtained under a range of UV exposures.