Monday, June 11, 2007
BrO at Summit
Last night the GaTech CIMS group (Greg Huey, David Tanner, etc) measured relatively high levels of BrO (bromine monoxide) during a high wind event (windspeeds greater than 14 m/s). This is one of the things that we were looking for this summer. In 2003/4 we saw unusually high OH radical during blowing snow events and our hypothesis was that Br chemistry may be occurring. The OH was not that elevated last night, but the OH/HO2 ratio was. In addition, there was a peak in the reactive gaseous Hg. While this is not conclusive, it is all very encouraging. Interestingly, Jack Dibb and Pieter Beckman's soluble Br- was not elevated. So we have much to figure out. A related question is: Where is the Br coming from. As you can see from the top figure (from University of Cologne), there was a high pressure system over southern Greenland. This was giving us strong westerly winds.
Above is a Hysplit model calculation (from NOAA-ARL) of where the air we sampled last night came from. This is a 2 day back trajectory which suggests that this airmass stayed on icesheet for the past 2 days, but started off near the coast, not too far from Kangerlussuaq.
Here is the SCIAMACHY Satellite measurement of total column BrO for 04-06 June 2007, the data for 07-09 June would be better, but it is not available yet. In anycase, you can see that hotspots for BrO west of Hudson Bay and around the North Pole. Also significant BrO over all of Greenland. Some of this BrO is probably high above our heads, but perhaps some comes in from the Coast during this storms, or maybe mixes down from above. This is still a mystery. See http://www.oma.be/BIRA-IASB/Molecules/BrO/level3.php for more SCIA BrO data.
This figure shows where open water is and where sea ice is melting. This is the average plot for the month of May, but shows significant open water southwest of Greenland. Theory is that you have to have open leads in the ice with Br- in the ice reacting with ozone to make BrO.
See that National Snow and Ice Data Center (http://nsidc.org/data/seaice_index/archives/index.html) for more sea ice extent data.
Posted by Barry Lefer at 6:14 PM