Horizontal gradients of bromine monoxide (BrO) across the lead and young sea ice features, from surface based instruments near Barrow, AK during the BRomine, Ozone, Mercury EXperiment (BROMEX), Spring 2012
Abstract
Reactive halogens in the lower atmosphere alter the oxidation pathways in polar regions during springtime. Bromine radicals play a key role in ozone depletion episodes (ODEs) and the oxidation of many gaseous constituents. Inorganic saline surfaces are believed to be the sources of the reactive bromine. However, the specific mechanisms that activate and sustain the production of these radicals remains uncertain. One of the main goals of BROMEX is to better understand the coupling of ice and snow surfaces to the chemistry occurring at or near these surfaces. Three ground based instrument sites observed bromine monoxide (BrO) via Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS), in-situ ozone, and basic meteorology. One site was stationary at Barrow and the other two aboard autonomous buoys (IceLander1,2) at different remote sea-ice locations. IceLander1 (IL1) was deployed to the landfast ice northeast of Barrow for the duration of March. IceLander2 (IL2) was deployed to the sea ice west of Barrow. During March, the three instruments conducted simultaneous measurements spanning a spatial area of approximately 10x50 km. Upon the lead opening at Barrow, observations from a now drifting IL2, were made from the downwind side of the open lead. Young sea ice features between Barrow and IL2 were probed (by comparable measurements at both locations) over a spatial fetch greater than 100km. During periods of horizontal advection between the sites, typical parcel transit times were on the order of less than one hour to upwards of a day. We report limited evidence that there is an appreciable difference in the BrO abundance measured when air parcels traverse over the active ice zone, between the IL2 and Barrow sites. A BrO boundary layer vertical column density diurnal pattern with a minimum at local solar noon is similarly observed at all sites for the entire experiment. Minimal horizontal BrO gradients, similar rates of ozone change, and recurring BrO diurnal patterns at all sites signify widespread processes controlling both halogen activation and chemical recycling over snow and ice surfaces. We reaffirm that mechanistic studies of ice and snow surfaces are vital to understanding halogen activation and other processes that operate during a dynamic polar springtime.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.A31D0068W
- Keywords:
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- 0365 ATMOSPHERIC COMPOSITION AND STRUCTURE / Troposphere: composition and chemistry;
- 1621 GLOBAL CHANGE / Cryospheric change;
- 1630 GLOBAL CHANGE / Impacts of global change;
- 1640 GLOBAL CHANGE / Remote sensing