Boundary Layer Halogens in Coastal Antarctica

Saiz‐Lopez, Alfonso; Mahajan, Anoop S.; Salmon, Richard; Bauguitte, Stéphane; Jones, A. E.; Roscoe, H. K.; Plane, J. M. C.

doi:10.1126/science.1141408

Cited by 301 publications

(332 citation statements)

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“…Iodine monoxide (IO) mixing ratios of several ppt have been detected by ground-based passive and active differential optical absorption spectroscopy (DOAS) (Frieß et al, 2001;Saiz-Lopez et al, 2007b). Observations from satellite (Schönhardt et al, 2008;Saiz-Lopez et al, 2007a) indicate that the presence of IO is a widespread phenomenon along the Antarctic coast and over the sea ice covered Antarctic ocean.…”

Section: Introductionmentioning

confidence: 99%

Iodine monoxide in the Antarctic snowpack

et al. 2010

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Abstract. Recent ground-based and space borne observations suggest the presence of significant amounts of iodine monoxide in the boundary layer of Antarctica, which are expected to have an impact on the ozone budget and might contribute to the formation of new airborne particles. So far, the source of these iodine radicals has been unknown. This paper presents long-term measurements of iodine monoxide at the German Antarctic research station Neumayer, which indicate that high IO concentrations in the order of 50 ppb are present in the snow interstitial air. The measurements have been performed using multi-axis differential optical absorption spectroscopy (MAX-DOAS). Using a coupled atmosphere -snowpack radiative transfer model, the comparison of the signals observed from scattered skylight and from light reflected by the snowpack yields several ppb of iodine monoxide in the upper layers of the sunlit snowpack throughout the year. Snow pit samples from Neumayer Station contain up to 700 ng/l of total iodine, representing a sufficient reservoir for these extraordinarily high IO concentrations.

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Section: Introductionmentioning

confidence: 99%

Iodine monoxide in the Antarctic snowpack

et al. 2010

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“…BrCl). The latter are rapidly photolyzed to halogen atoms.In Antarctica, besides BrO up to 20 pmol/mol IO was observed (13,14), which enhances the ozone depletion. Nevertheless, so far no IO has been reliably observed in the Arctic.…”

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confidence: 99%

“…LP-DOAS instruments employ a defined absorption path of several kilometers between a light emitting/receiving telescope and a retroreflector. However, due to their demanding logistic requirements these accurate and direct measurements of halogen oxides in polar regions are rare and until now were only performed at coastal sites or inland (8,9,10,14,23,24). Later also passive DOAS measurements with satellite (see, e.g., Ref.…”

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confidence: 99%

Observation of halogen species in the Amundsen Gulf, Arctic, by active long-path differential optical absorption spectroscopy

Pöhler

Vogel

Frieß

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

115

136

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In the polar tropospheric boundary layer, reactive halogen species (RHS) are responsible for ozone depletion as well as the oxidation of elemental mercury and dimethyl sulphide. After polar sunrise, air masses enriched in reactive bromine cover areas of several million square kilometers. Still, the source and release mechanisms of halogens are not completely understood. We report measurements of halogen oxides performed in the Amundsen Gulf, Arctic, during spring 2008. Active long-path differential optical absorption spectroscopy (LP-DOAS) measurements were set up offshore, several kilometers from the coast, directly on the sea ice, which was never done before. High bromine oxide concentrations were detected frequently during sunlight hours with a characteristic daily cycle showing morning and evening maxima and a minimum at noon. The, so far, highest observed average mixing ratio in the polar boundary layer of 41 pmol/mol (equal to pptv) was detected. Only short sea ice contact is required to release high amounts of bromine. An observed linear decrease of maximum bromine oxide levels with ambient temperature during sunlight, between −24°C and −15°C, provides indications on the conditions required for the emission of RHS. In addition, the data indicate the presence of reactive chlorine in the Arctic boundary layer. In contrast to Antarctica, iodine oxide was not detected above a detection limit of 0.3 pmol/mol.halogen chemistry | ozone depletion | bromine explosion | polar | DOAS T he depletion of the stratospheric ozone layer due to reactive halogen species is well known. Similarly, ozone depletion events (ODEs) in the polar boundary layer, arising after sunrise, were discovered in the 1980s (1, 2, 3). These events were found to be related to high concentrations of filterable bromine. It was therefore proposed that ozone could be destroyed by catalytic reaction cycles involving bromine atoms (Br) and bromine monoxide (BrO) (4).The initial reaction is the release of Br 2 from the liquid to the gas phase and the photolysis to Br, which will lead to a quick oxidation to BrO by destroying an ozone molecule. Note that there is always some production of Br atoms from the photochemical degradation of CH 3 Br, which is ubiquitous in the atmosphere. Bromine atoms are recycled from BrO by different processes. The most important recycling is the BrO self-reaction (R 2·BrO ) with the total rate constant k 2·BrO ¼ 3.2 × 10 −12 cm 3 molec −1 s −1 (5) producing Br atoms or Br 2 . During daylight, Br 2 is again photolyzed to Br, thus all channels of R 2·BrO lead to a net loss of O 3 . Overall, reactive bromine (Br and BrO) acts as a catalyst for ozone destruction. An autocatalytic release of bromine from the sea salt surface ice, the so-called "bromine explosion" (6), supplies sufficient bromine to the gas phase. A simplified overview on bromine release mechanisms and ozone destruction cycles is given in Fig. 1 (for a recent review see 7).The key role of bromine was first confirmed by long-path differential optical absorption ...

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“…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.…”

Section: Introductionmentioning

confidence: 99%

Halocarbons associated with Arctic sea ice

Atkinson¹,

Hughes²,

Shaw³

et al. 2014

Deep Sea Research Part I: Oceanographic Research Papers

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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.

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Boundary Layer Halogens in Coastal Antarctica

Cited by 301 publications

References 25 publications

Iodine monoxide in the Antarctic snowpack

Iodine monoxide in the Antarctic snowpack

Observation of halogen species in the Amundsen Gulf, Arctic, by active long-path differential optical absorption spectroscopy

Halocarbons associated with Arctic sea ice

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