Award: OCE-1434805

Mercury cycling in the Arctic is very complex since atmospheric chemistry plays an important role in modifying chemical form of mercury. Indeed, atmospheric gaseous elemental mercury (Hg⁰) is quickly oxidized to divalent mercury (Hg^II) during springtime partly due to halogen radicals. We call that atmospheric mercury depletion events (AMDEs). Here, we tried to evaluate the potential role of sea ice in the mercury dynamics studying two distinct locations: (1) in close proximity to the Arctic Ocean, and (2) in the interior arctic tundra. Main results from the underway sampling by the three groups has confirmed the notion that dissolved Hg⁰ builds up under the ice and that the concentrations are higher than found in open water. The concentrations in the open water in the early stages of the cruise were very low suggesting the potential for Hg⁰ deposition to the ocean from the atmosphere. This has rarely been observed and the finding suggest the air-sea exchange of Hg in the Arctic is unique compared to other ocean basins. Comparing these two study sites, we were able to understand that the sea ice influences a large region of the Arctic through AMDEs. Rapid changes were observed in the atmosphere (including ozone concentrations), as well as in the surface snowpack samples with dissolved mercury enhancement for approximately two days. Our results help for the global mercury cycling understanding in such remote environments.

Last Modified: 04/08/2017
Modified by: Yannick Agnan