Wading through melt pools

Last night we were surrounded by coastal fast ice attached to the land. But that ice has begun to break up and we're now drifting along with it towards the north-west.

The low winds forecast for tomorrow make it an ideal day to refuel the Amundsen from the barge that was moored nearby last summer and has been trapped in the ice all winter. So today is likely to be the last chance for heading out on the ice this trip as soon it won't be thick enough to walk on safely.

It's an eerie feeling wading into the melt pools that are starting to appear on the surface of the ice. Somehow it doesn't hit you that you're standing on the sea, on ice just a metre thick, until you start stepping through water.

I spend the afternoon with a team investigating whether the melt pools change how much light passes through the ice. Light affects both what type of organisms can live below and also how much energy enters the water, Andrea Rossnagel of the University of Manitoba tells me. The scientists drilled two holes in the ice on either side of a melt pool and passed a rope between them. Then Haakon Hop of the Norwegian Polar Institute dived under the ice through a hole that a seal created earlier and measured the amount of light getting through at metre intervals along the length of the rope using an ocean colour radiometer.

Having spent more than an hour in sub-zero temperature water, Haakon sprinted around the ice to warm up before returning to the depths to take samples of water for his own work on zooplankton - tiny sea creatures that feed on algae and floating plant cells. Not much is known about the concentrations of zooplankton just below the ice as it's hard to sample that close to the surface without diving. Although the Amundsen has a "moon pool" that researchers can use to access open water from inside the boat when it's surrounded by ice, they can't start to take measurements until a few metres below the surface.

Meanwhile, Debbie Armstrong of the University of Manitoba drilled cylindrical samples of ice to measure the amount of harmful substances such as mercury present while Stephane Thanassekos of Laval University cast a net about 20 m down through the seal hole to look for fish larvae. He didn't find any today but a few weeks ago they were plentiful.

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