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Last day in McMurdo, before WAIS

Posted November 30th, 2009 by celene.carillo@oregonstate.edu
Some of the odd ice features you get with the combination of drifting snow and ice

Some of the odd ice features you get with the combination of drifting snow and ice

We’ve had a break in the weather this past week and a number of  flights that had previously been delayed have been able to make it into the camp. I am still in McMurdo but I have a flight scheduled for Monday the 30th. While my time in McMurdo has been fun I am much more excited to get to work. Because of all the various delays we will have to work very hard to catch up.

During the downtime in McMurdo I was able to participate in various recreational activities and tours that our offered. The highlight for me was  trip to the pressure ridges near Scott Base. The pressure ridges form where the ice shelf meets the sea ice.  An ice shelf is essentially a glacier that is floating on the ocean.  The ice forms on land but then flows down towards the sea. The point at which the ice is no longer contacting ground but instead floating is called the grounding line. Understanding the the way a glacier interacts with the ocean in relation to its grounding line is very important in estimating sea level change. When pieces of an ice shelf break off to form icebergs they do not affect sea level because that ice has  already been displaying its liquid volume. This is same principle of bouyancy that can be illustrated by watching the water level in a glass as ice cubes melt (okay, admittedly not that exciting), but what you’ll see is that level does not change. If an ice shelf begins to disintegrate beyond if grounding line and ice that was previously on land is now calving into the ocean, then you will have an increase in sea level. Many scientist are concerned about the collapse of ice shelves like the Larsen B because the ice shelves may provide a buttressing effect on the ice stored on the continent. The loss of the ice shelves may then accelerate the loss of the grounded ice.

But back to the pressure ridges. What we saw on the tour was sea ice buckling against the ice shelf. The sea ice, which is

Pressure ridges, with Mt. Erebus in the background

Pressure ridges, with Mt. Erebus in the background

water that has frozen on the surface of the ocean, abuts the ice shelf and is stressed by tides and currents. The product of these forces are large cracks in the sea ice and sail like structures where the ice has jutted up. The cracks in the sea ice are a great place for seals to surface and consequently a great place to see some Antarctic wildlife. We saw one seal from a distance but we didn’t approach it because we don’t want to stress the animals down here.

In addition to the pressure ridges I also got to visit an ice cave that has formed inside a glacier. Check out the video to learn more about that trip.

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