Ross Island’s North Shore

The weather finally cooperated with us and we made it out for our reconnaissance flight on Saturday. We even managed to bag a couple of samples along the way. After spending the last 8 weeks on the south side of Ross Island it was very interesting to see the north side. The mountains drop more dramatically into the sea on here, and the ice over the open waters of Ross Sea presents a much more fractured and dynamic surface than we normally see in McMurdo Sound. All together it makes for a much more dramatic backdrop while we work.

We worked our way around Ross Island in the counter-clockwise direction. As soon as we rounded Cope Crozier we started probing the sea ice, looking for ice thick enough to land next to ice thin enough for us to sample. Finding this combination isn’t easy. When we spotted a suitable ice flow that we thought was thick enough to land on the helicopter would set down gently with the pilot keeping the rotors spinning at full power. Working under the spinning blades someone would hop out and quickly drill the ice to see how thick it is.

There’s a pattern to the distribution of ice thickness in both land fast ice and pack ice (the ice not anchored to the land), but it takes a little while to start to see it in a new area. Successive storms, cold snaps, and the underlying pattern of prevailing winds and currents establish a checkerboard of thick and thin flows. After we checked a few flows and found them too thin to power down the aircraft we started finding flows that were thick enough. Once we were dialed in on the thicker floes we were able to piece together a safe path along them to the younger sea ice.

We didn’t find any truly young sea ice. The thinnest ice that we found was 28 cm, probably about two weeks old, though this ice was covered with old, moderately salty (60 ppt, roughly twice the salinity of the ocean) frost flowers. Although the ice was plenty thick to walk across we took the opportunity to test out techniques for working over thin ice. Hopefully we will need these techniques for our next foray. If the weather allows on Monday we will head back out to the north side of Ross Island, this time working to the northwest toward Beaufort Island. From our reconnaissance flight we could see thick pack ice all the way to Beaufort and a glimmer of sunlight off of the lead that seems to persist in a semicircle around it. With luck that lead will be full of very young ice and frost flowers!