As we mentioned last week, Coast Guard Cutter Healy is sending in regular updates as she makes her way on an Arctic science mission. This post by Ensign Emily Kehrt comes to us from about 90 nautical miles northwest of Point Barrow, the northernmost point in Alaska.
We just re-entered open water after a week in very thick ice. Although we were never more than four miles from the ice edge, the ice was so thick and snow-covered that Healy could barely break through it.
By the end of the first day, the OODs [Officer of the Deck] were measuring the progress made during their watches in ship lengths. On one particular day, the watch team on the 8 p.m. to midnight could still see the ridge in the ice where the 4 a.m. to 8 a.m. watch team had taken the watch that morning. As our Commanding Officer, Captain Bill Rall, stated in an operational summary, “Less than 2NM from open water, still no relief. We could literally walk to the ice edge faster than taking the ship.”
While the OODs were looking for cracks and leads in the ice to help us make some headway, the science party looked for the perfect ice floe for an afternoon on-ice science deployment. Don Perovich, a member of the science party who has many years experimenting on Arctic ice, explained what they look for in an ice floe – a large, flat piece, with melt ponds for surface water samples (see picture left). The ice has to be thick enough to support the people on the ice and all of their gear, but it can’t be too thick, because the science party needs to be able to drill all the way through it.
Once we find the perfect piece, the science team is primarily trying to understand the distribution of sunlight through different ice surface conditions, thicknesses, and melting habits. By understanding the distribution of sunlight, they can learn a lot about the bio-geochemistry of the ice.
While deployed on the ice, the scientists are conducting multiple experiments to this end. During each station, the science party will take one or two ice cores to test for oxygen isotopes, which helps paint a picture of how that particular piece of ice formed. They bring the cores back to the ship where a biologist measures algae growth on the bottoms. They also save some pieces to take home to measure soot build-up for a different experiment.
They also take water samples at different depths, measuring productivity in and chemical properties of the water. Where they don’t take cores, they use electromagnetic pulses to measure the ice thickness in different locations. They also test for spectral albedo, or the reflectivity of the sun on the ice, measuring the light coming from the sun, reflecting off the ice, and permeating through the ice to the water below.
We’ll be conducting open water science stations for the next week, before we head back into the ice.
Till next time,
ENS Emily Kehrt