At the University of Manitoba’s Sea-ice Environment Research Facility frost flowers can be created under controlled conditions. These structures, which grow on young sea ice in the Arctic, can expose concentrated ocean brine to the atmosphere and may be implicated in bromine explosions.
By Tyler Irving
Posted May 2012
Frost flowers and bromine explosions sound almost extraterrestrial but they occur regularly in Canada’s Arctic. According to a recent study conducted as part of the 2007–2009 International Polar Year, these phenomena may be linked to changes in sea ice formation and could increase in the future.
Since the 1990s, researchers have noted that the return of the sun during the Arctic spring appears to trigger increases inatmospheric concentrations of bromine oxide (BrO). At the same time, concentrations of ground-level ozone (O) and gaseous elemental mercury (GEM) decrease, often to near-zero values. It is hypothesized that these phenomena are related through a cascade of photo-catalyzed reactions, called a bromine explosion.
Feiyue Wang is a professor in the Department of Chemistry at the University of Manitoba and one of the authors of the study, published in the Journal of Geophysical Research. Taking direct ground measurements from the Canadian research icebreaker CCGS Amundsen, Wang’s group was able to show a strong correlation between rising levels of BrO and falling levels of Oand GEM in real time. The study also used satellite data to examine the spatial distribution of increases in BrO. “It's mainly limited to the Beaufort Sea area, which suggests it is a tropospheric phenomenon, as opposed to a stratospheric one,” says Wang.
One possible source of bromine could be newly forming sea ice. As sea water freezes, its natural salts, including bromides, get concentrated on the top and bottom of the ice sheet. At the same time, filamentous ice crystal structures called frost flowers form on top of the ice. Frost flowers can act like sponges, soaking up concentrated brine and exposing it to the atmosphere. However, it’s unclear how the anionic bromide in the salts becomes activated to form atomic bromine and BrO. To answer that question, Wang and his team designed the outdoor Sea-ice Environment Research Facility (SERF) at U of M to create frost flowers under controlled conditions. “Although it's only been operational for a couple of months, we’ve already got several nice frost flower events, including a really beautiful blossom that lasted about 30 hours,” Wang says.
If it’s proven that frost flowers are the source of bromine, it could have major implications. Climate change is reducing the amount of multi-year sea ice, which could mean more newly forming first-year ice. This in turn could drive more bromine explosions, drawing mercury from the atmosphere into the surface environment. Mercury levels in Arctic marine mammals are already of concern, especially for those people who rely on these animals for food.
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