Halocarbons associated with Arctic sea ice, Deep-Sea Research I, http://dx.doi.org/10. 1016/j.dsr.2014.05.012 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Abstract Short-lived halocarbons were measured in Arctic sea-ice brine, seawater and air above the Greenland and Norwegian seas (∼81°N, 2 to 5°E) in mid-summer, from a melting ice floe at the edge of the ice pack. In the ice floe, concentrations of C 2 H 5 I, 2-C 3 H 7 I and CH 2 Br 2 showed significant enhancement in the sea ice brine, of average factors of 1.7, 1.4 and 2.5 times respectively, compared to the water underneath and after normalising to brine volume. Concentrations of mono-iodocarbons in air are the highest ever reported, and our calculations suggest increased fluxes of halocarbons to the atmosphere may result from their sea-ice enhancement. Some halocarbons were also measured in ice of the sub-Arctic in Hudson Bay (∼55°N, 77°W) in early spring, ice that was thicker, colder and less porous than the Arctic ice in summer, and in which the halocarbons were concentrated to values over 10 times larger than in the Arctic ice when normalised to brine volume. Concentrations in the Arctic ice were similar to those in Antarctic sea ice that was similarly warm and porous. As climate warms and Arctic sea ice becomes more like that of the Antarctic, our results lead us to expect the production of iodocarbons and so of reactive iodine gases to increase.
IntroductionThere has been much speculation about sources of reactive halogens in the polar troposphere. The presence of high concentrations of both iodine and bromine monoxide (IO and BrO) over Antarctica and its sea ice [Saiz-Lopez et al. 2007, Schoenhardt et al. 2008 suggests an iodine-selective mechanism, as the sum of iodide plus iodate is 1000 times less abundant than bromide in seawater. Although IO has been measured above sub-Arctic sea ice at amounts of up to 4 pptv [Mahajan et al. 2010], this is less than a quarter the Antarctic concentrations.