Submitted by Anonymous on Mon, 11/30/2009 - 16:17
Forums
Ice Core Drilling in West Antarctica

Hi my name is Claire Brown and I had a few questions from my polar geoscince class at Texas A&M. What are the challenges of drilling on a marine based ice sheet? Is this drill time completely dedicated to the a single core? Do you drill another for comparison?What other research are you doing at the Antarctic? What kind of drilling techniques/specific machinery do you use to successfully extract a core from this region? Thank you!

Tue, 12/29/2009 - 07:49

Heidi Roop

Hi Claire! Thank you for the questions!
What are the challenges of drilling on a marine based ice sheet?
A: We are on the ice divide where there is bedrock below us. The pressure of the ice sheet makes the bedrock and some of the ice below sea level, where just the edges of the ice sheet flow into floating ice shelves. Based on our location at the ice divide, where the ice flows outwards towards the ocean, we don't face too many challenges related specifically to the marine-based nature of the ice sheet.
Based on the response from Dave Ferris, one of the WAIS drillers, the greatest challenges are the different types of ice that we drill into. The first is brittle ice, which has the tendency to crack once it is removed from the borehole. This happens because the pressure in the bubbles is greater than the pressure at the surface of the ice sheet due to the weight  ofthe ice sheet. The weight of the ice sheet compresses the bubbles. So, when the ice is removed and re-enters a low-pressure environment (at the surface of the ice sheet), it breaks or pops.
The second type of ice we will core here at WAIS is warm ice (ice near the melting point). Warm ice is the ice that is near bedrock and is warmed up from the thermal energy of the earth. This ice has the tendency to melt when it is drilled as the ice is closer to melting point than the ice more distal from the earth's core.  When you add the friction of the drill to warm ice, you warm it up further, causing it to melt and then refreeze. This poses a big challenge to the drillers because the drill can get stuck! We likely won't reach any warm ice until next year when we get closer to bedrock.
Is this drill time completely dedicated to the a single core? Do you drill another for comparison?
A: For right now, we are just drilling one core in one borehole. Once we have reached just above bedrock we will begin replicate coring. This likely won't happen until 2012. Scientists will identify the sections, or depths, of interest and the drillers will then drill down the same hole we are drilling now and basically begin drilling horizontally. First, they will go to the appropriate depth and then begin to cut over at an angle, eventually getting a near vertical section of ice that parallels the original borehole (the one we are making now).
What other research are you doing at the Antarctic?
A: I am not doing any other research but there are several people here who are interested in the physical properties of the ice and snow and have been taking samples for isotopes and chemistry. All of this work helps other scientist to understand the ice in the borehole and helps us to understand the processes occurring here at WAIS Divide. I am currently working on a video about this work so stay tuned! It should be posted in a few days, once the file makes it on a plane to McMurdo where it can be uploaded.
What kind of drilling techniques/specific machinery do you use to successfully extract a core from this region?
A: This is a high-tech operation! We have lots of computers and a relatively complicated drill set-up. The drill is specifically designed for deep ice drilling. Our drill is the DISC drill (Deep Ice Sheet Coring) and all of the design and operations are managed out of the University of Wisconsin, Madison. Stay tuned for a post with a video or pictures about the drilling process.
Thanks for the questions!
Cheers,
Heidi