Short term variations of local CH3Br concentrations: Effects from ocean sources

Author: S. Mark Leidner and John M. Henderson
Date: 
May 29, 2001 - June 2, 2001
Type: 
Presentation
Venue: 
American Geophysical Union, Spring Meeting 2001
Citation: 

Scott, C., M. Ko, S. M. Leidner, and J. M. Henderson, 2001. Short term variations of local CH3Br concentrations: Effects from ocean sources. 2001 AGU Spring Meeting, Boston, MA 29 May-2 June 2001.

Chlorine (Cl) and bromine (Br) are primarily responsible for the observed stratospheric ozone loss seen over the past few decades. Since methyl bromide (CH3Br) is believed to be the largest source of Br in the stratosphere, there has been much interest in its sources and sinks, both natural and anthropogenic. We have examined hourly ground-based measurements of CH3Br from La Jolla, California. During 1998, numerous occurrences of elevated levels of CH3Br are seen (greater than 100 pptv) which last 24 - 48 hours in duration. Ocean productivity is a known source of CH3Br. Given the location of the measurements, it is likely that the ocean sources are responsible for the local variations seen in the CH3Br at La Jolla. We investigate this hypothesis by examining ocean productivity and sea surface temperatures using the fifth generation Penn State/NCAR Mesoscale Modeling System (MM5). Utilizing the SST, ocean productivity and the MM5, we have parameterized the ocean source of CH3Br that is released into the atmosphere. Results from our analysis are presented of a six day bloom cycle off the shores of California.