Glacial deposits: A clue to reconstructing the history of the Antarctic ice sheet

by | 2.10.2011 at 11:44am
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We set out on the snowmobiles with all the sleds to Mount Achernar with all our stuff. After about three hours we reach the site (crossing the flagged crevasse zone with no problem). We are joined by a fifth team member, Tim Flood, a Professor at St. Norbert College in Wisconsin. Tim has expertise in petrology or rock composition. So, we will have one additional person for the Achernar part of the trip.

Kathy Licht, Tim Flood and Nicole Bader exploring glacial deposits near Mt Achernar

At first we only find ‘blue ice’ to set up camp. Blue ice gets its name mainly because – in contrast to the typical situation of having a layer of snow on top of the ice sheet – there is only ice. The snow layer that normally covers the top of the ice sheet is blown away where the winds blow pretty fast and consistently. This means there is no good place for camp right in the Achernar area because all the blue ice is a sign of strong winds. We decide to back up a few miles to where the snow starts again and camp a little but away from Mount Achernar. This means we will have a ‘daily commute’ to get to where we want to work, but at least we have a nice place to live for the week. It is less windy where we decide to set up camp and a nice layer of snow in which to pitch the tents and walk around. Blue ice is very difficult to walk on – it is just what it sounds like – walking on ice!

Setting up just another field camp at Mt Achernar

We set up camp. Unlike at Mount Howe, here each person will have their own tent. In addition, we set up the bathroom tent and a huge kitchen tent, named the ‘Arctic oven.’ The arctic oven will act as a kitchen and dining area. It is about 25 feet long, enough to be comfortable. And, when we have two stoves going inside, the temperature gets up to a comfortable 60 degrees or even higher (hence, its name); comfortable enough to start peeling off all our jackets while eating. Two little speakers that Tim picked up in an airport, attached to ipods, means we even have a stereo system in the arctic oven cook tent.

The first day we drive out to where we want to work. It takes about an hour and a half each way by snowmobile. This is quite a bit of time. In addition, the glacier deposits we want to study are much larger in area compared to at our first site at Mount Howe. It is not practical for us to drive everywhere and get to all the places by walking. We realize we will need to utilize the helicopter from nearby CTAM. So, the next week or so we alternate: a “snowmobile day” when we commute by snowmobile from camp to the field site and “helo days”. On the helo days, the helicopter flies out to our camp (a short flight by helicopter from the CTAM camp) picks us up, takes us exactly where we want to go around Mount Achernar, and then at the end of the day, comes back out to bring us back to our camp. All these trips only take the helicopter folks about 75 minutes in total each day, given how fast they go.

Collecting samples from the top of boulders that got left back by the retreating glaciers. At home in the lab at Lamont, we will use a method called 'Surface Exposure Dating' to figure out when the ice sheet left these boulders behind when it retreated.

We spend the next 8 days or so doing the same sort of work as at our first site Mount Howe. We map the glacier deposits (how red or oxidized are they – how do their elevations changes? How do the deposits themselves change in terms of shape and composition and other characteristics?). Mike K and Mike R (with occasional assistance from others) collect samples for the surface exposure dating, so they can eventually figure out how old all the deposits are. Kathy, Nicole and Tim study the composition and types of glacier rocks and sediments left behind.

Similar to our finding at Mt Howe, we find pronounced changes in the glacier moraine deposits around Mt Achernar. This indicates there are likely deposits of different ages, left behind at different times by the ice sheet when it was bigger. All the team members continue to collect samples that will be analyzed later in the lab.

Running water in Antarctica at Mt Achernar

Mike K, Kathy, Mike R, Nicole and Tim

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