Cracks in the Arctic sea ice could raise mercury risk
NASA scientists explain mercury concentrations in Alaska
Cracks in the Arctic sea ice may be pumping atmospheric mercury down to the surface, a new study by NASA suggests.
When cracks form in sea ice, that sometimes forms an open water channel, NASA said in a Jan. 15 news release. The water in that “lead” is warmer than the air above it, which creates a churning action that can pump mercury.
And that process can push more toxic pollutants into the food chain, warns the study, which was published in the science journal Nature this week.
“None of us had suspected that we would find this kind of process associated with leads,” said Son Nghiem, a scientist at NASA’s Jet Propulsion Laboratory in California and co-author of the study.
To determine their findings, scientists measured increased concentrations of mercury near ground level after sea ice off the coast of Barrow, Alaska cracked in 2012, creating those open seawater channels called leads.
Scientists say the mixing was created when the cold air and warmer water interact is so strong, that it actually pulls mercury down from a higher layer of the atmosphere to near the surface.
You can watch a time-lapse video here of the clouds that form over cracks in Alaskan sea ice.
Almost all of the mercury in the Arctic atmosphere is transported there in the form of gas from sources in areas farther south.
Scientists have long known that mercury in the air near ground level undergoes complex chemical reactions that leave the element on the surface.
Once the mercury is completely removed from the air, these reactions stop. But this newly discovered mixing triggered by leads in the sea ice pushes down additional mercury to restart and sustain the reactions.
The concern now is that there are more leads in the Arctic Ocean as climate change reduces its sea ice cover.
“Over the past decade, we’ve been seeing more new sea ice rather than perennial ice that has survived for several years,” Nghiem said. “New ice is thinner and saltier and cracks more easily. More new ice means more leads as well.”
Nghiem points out that this new finding comes at a time where there is a push for international action on Arctic mercury pollution.
The Minamata Convention, a global treaty to curb mercury pollution in which Arctic vulnerability is particularly noted, has been signed by 94 nations since it was opened for signatures in October 2013.
“Once the Minamata Convention has been ratified and becomes international law, we expect this work to help assess its effectiveness,” Nghiem said.
NASA’s study was jointed funded by the Desert Research Institute and Environment Canada.