A study of the vertical scale of halogen chemistry in the Arctic troposphere during Polar Sunrise at Barrow, Alaska

The vertical extent and impact of halogen chemistry in the Arctic springtime was investigated through balloon-based measurement of several atmospheric chemical components. Various chemical species, including volatile organic compounds (VOCs), ozone, and elemental mercury, that are modified by halogen chemistry were measured from the surface to ∼300 m during late March through mid-April 2005 in Barrow, Alaska. It is observed that the halogen chemistry appears to be most active in the lowest 100-200 m of the atmosphere. The Hg vertical concentration profiles are consistent with destruction by chemistry that evolves from a species emitted from the snowpack, most likely Br₂ and BrCl, and the VOC profiles also demonstrate the limited vertical scale of halogen-initiated chemistry taking place above the Arctic snowpack.