Although sea ice is often thought to block the flow of oil through ocean water, a team of researchers at the University of Alaska Fairbanks is studying how oil can percolate into ice, according to a press release from the University of Alaska Fairbanks. This has implications for the methods and policies used to clean up oil spills in the Arctic.
“Many oil cleanup crews even think of ice as an aid to cleanup,” said Kyle Dilliplaine, a graduate student at the UAF School of Fisheries and Ocean Sciences. “A lot of policies are built on the ease of cleaning up the oil when it gets ‘corralled’ by sea ice. But the science is not always behind it. It’s not that easy.”
Dilliplaine is studying how microscopic organisms within the sea ice affect the ability of oil to flow into the ice. He is collaborating with SFOS Professor Eric Collins, International Arctic Research Center Professor Hajo Eicken and SFOS affiliate faculty members Rolf Gradinger and Bodil Bluhm.
With funding from the Bureau of Ocean and Energy Management through the Coastal Marine Institute, researchers artificially grew sea ice in experimental chambers filled with seawater and added tiny organisms called biota to the ice. Then they “spilled” oil in the water under the ice.
Sea ice is porous, with many channels between its freshwater crystals. Biota living within the ice secrete mucus that may block channels, making the ice even more porous.
Oil can flow into channels and into the pores around ice crystals. The more porous sea ice is, the easier it is for oil to percolate in.
To simulate a continuous-flow oil spill, Dilliplaine pumped oil into the water and let it pool underneath the ice. To represent oil dispersal by wave action, he placed a small pump under the ice that blew out oil droplets slowly over time.
Dilliplaine found that the oil inhibited the growth of algae and mucus production. There was no significant change in the mass of chlorophyll in the oiled tank, while chlorophyll mass increased from approximately two to 80 milligrams in the tank without oil.
“In the control tank with no oil, we saw a 30-fold increase in the amount of algal pigment — which is often used as a indicator for quantifying the mass of algae on ice — from the beginning to the end of the experiment,” Dilliplaine said.
Bacteria production remained relatively constant. Dilliplaine plans to do genetic testing to learn how the composition of bacteria on the ice may have changed.
Sea ice cover in the Arctic Ocean is projected to continue decreasing in the near future. This will increase the variability of sea ice motion and ship traffic, both of which are likely to increase the number of marine accidents in the Arctic.
Understanding the influence of sea ice on the motion of spilled oil will become crucial as the potential for Arctic spills increases.
Dilliplaine stressed the importance of understanding that ice is not a barrier to oil movement. “We can’t think about the ice as a physical barrier that can help us with our cleanup. It might actually be working pretty far against us,” he said.
