Sea ice is not just solid frozen water. It’s riddled with tiny pockets and channels of liquid brine. Whether those pockets connect to form pathways determines whether seawater, nutrients and gases can move through the ice, according to decades of research by University of Utah mathematician Ken Golden.
In a new study, Golden and colleagues focus on granular sea ice, a type made of small, randomly oriented ice grains that is becoming more common as the polar regions continue warming. The scientists wanted to know when this type of ice becomes porous enough for fluids to flow vertically through it.
They found a clear tipping point. In columnar ice, characterized by orderly crystals, fluid starts flowing when 5% of the ice volume is brine. But with granular ice, that threshold is twice as high, about 10%, indicating that in this type of ice, the brine phase is far less interconnected. This difference has major implications for microbial communities that form the base of the robust sea ice ecosystem and for various geophysical processes.
“Going from 5% to 10% means that you need twice the porosity, twice the brine volume fraction to get flow. If algae are living in columnar ice versus living in granular ice, then there are quite different conditions under which they’ll get their food and nutrients,” said Golden, a distinguished professor mathematics. “It’s much harder to get it in granular ice. And there are other microorganisms, viruses and bacteria and nematodes and all sorts of other critters, that would be in the same boat.”
In this study, Golden collaborated with Cynthia Furse, a U professor of electrical and computer engineering, to measure various properties of sea ice in the Arctic and Antarctic. Their findings appear in Scientific Reports.
Continue reading Brian Maffly’s “As polar ice changes, so do the rules governing it” on @theU.