[A-CG42] Biogeochemical linkages between the surface ocean and atmosphere

[ACG42-01] Production of bromoform in sea ice and emission to the atmosphere

*Daiki Nomura¹, Atsushi Ooki¹, Ellen Damm², Gerhard Dieckmann², Bruno Delille³, Markus Frey⁴, Mats Granskog⁵, Klaus Meiners^6,7, Anna Silyakova⁸, Takeshi Tamura⁹, Jean-Louis Tison¹⁰, Youhei Yamashita¹¹ (1.Faculty of Fisheries Sciences, Hokkaido University, 2.Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany, 3.Université de Liège, Liège, Belgium., 4.British Antarctic Survey, Cambridge, United Kingdom., 5.Norwegian Polar Institute, Tromsø, Norway., 6.Antarctic Climate andEcosystems Cooperative Research Centre, University of Tasmania, Hobart, Australia., 7.Australian Antarctic Division, Kingston, Australia., 8.Centre for Arctic Gas Hydrate, Environment and Climate, Tromsø, Norway., 9.National Institute of Polar Research, Tokyo, Japan., 10.Université Libre de Bruxelles, Bruxelles, Belgium., 11.Graduate School of Environmental Sceince, Hokkaido University, Sapporo, Japan.)

Keywords:sea ice, bromoform, polar ocean

Bromoform (CHBr₃) is one of the important bromine containing volatile halocarbons that are involved in ozone depletion in the atmosphere. Although the possible source of reactive bromine species from snow and sea ice has been discussed, mechanisms that control CHBr₃ production within sea ice and emission to the atmosphere remain unclear. Here, we show evidence of massive CHBr₃ production at sea ice surface-snow interfaces and its strong emission to the atmosphere from five field-campaigns to the Arctic Ocean, the Southern Ocean, and the Sea of Okhotsk in the winter and spring, in addition to supporting laboratory experiments. We found that the ice-related strong CHBr₃ emission was linked to the production of the CHBr₃ at the snow-sea ice interface through the haloform reaction. Our results suggest that sea ice acts as a strong CHBr₃ source for the atmosphere, indicating a significant contribution to the atmospheric bromine cycle.