Ice Sheet Stability in a Warming World. In November 2015, we embarked on a NSF-funded investigation to build a glacial-geologic record of the East Antarctic Ice Sheet's (EAIS) behaviour during the Pliocene and earlier, when temperature and sea level both were higher than today. The impetus for this work is the ongoing debate over whether or not the EAIS collapsed, grew, or sat tight during these past warm periods, and what that might mean for the coming centuries. In other words, we are using the ice sheet's past as a likely analogue for its future.
Located in the high central Transantarctic Mountains, our field sites - Dominion Range, Otway Massif, and Roberts Massif - abut the EAIS and contain relict moraines that document former surface positions of the ice sheet. In this way the peaks act as orographic yard sticks. By dating the moraines with cosmogenic nuclide (He-3, Be-10, Ne-21) surface-exposure dating, we can ascertain when the EAIS was as thick or thicker than at present and compare that record to estimates of Pliocene and Miocene climate. Glacial geology, pure and simple.
For all nuclides, samples are being prepared at the UMaine Cosmogenic Isotope Laboratory. For He-3 dating, clean pyroxene separates are measured at Berkeley Geochronology Center using noble gas mass spectrometry. For Be-10 dating, beryllium is extracted from clean quartz via anion and cation exchange and pH-controlled precipitations, prior to being converted to BeO and packed in cathodes. These targets are measured by the CAMS facility at Lawrence Livermore national Laboratory. Aliquots of clean quartz are also used for Ne-21 dating at BGC. All sample data, including nuclide concentrations, are archived on the Informal Cosmogenic-Nuclide Exposure-Age: Antarctica database (ICE-D).
Holly Thomas (University of Maine)
Project supported by NSF grant 1443321 PLR
Project News and Updates
Over the past two seasons we have collected a large number of samples, and an even larger number of photographs from the field. While they may not find themselves on the front page of National Geographic, these photos nonetheless give an impression of what it is like to live and work in the upper Transantarctic Mountains and a sense of scale for these timeless landscapes. Closer to home, and acknowledging that we spend more time in windowless labs than roaming Antarctica's hills, a selection of lab images documents the less glamourous aspects of this project: turning rocks into data. I'm going to add photos to this informal gallery over the coming weeks, and Allie will contribute more when she travels to BGC in the autumn to work with Greg on the noble gas mass spec.
22 November 2016 onward - Field Blog
Here's a link to Allie's field blog, 'Ancient Moraines', which tracks our team's progress over the 2016-17 Antarctic season: https://ancientmorainesblog.wordpress.com/meet-the-team/.
20 October 2016 - Stay tuned
We're off back south in just four weeks. By then we'll have a new field blog up and running and hopefully a GPS tracker, if we can figure out how to make it work. Watch this space.
1 September 2016 - 'Possibly the most He-3 ever observed in a terrestrial sample'
Greg and Holly measured what is quite possibly the highest concentration of cosmogenic He-3 in a terrestrial sample (ever!), in this case from a dolerite erratic perched high above Shackleton Glacier at Roberts Massif. To mark this auspicious occasion, and once the champagne had stopped flowing, Greg wrote a piece for his blog describing how this came about and what it might mean for past ice-sheet stability. Check out Greg's blog post here.
15 August 2016 - First He-3 samples go for measurement
Rock samples take a while to get from Antarctica to Maine, travelling by boat to California before being loaded onto wheels and trucked east. So it was with mild fanfare that we got the first batch of surface-exposure samples prepared in the UMaine lab and sent off to Berkeley Geochronology Center for mass spectrometry. Holly has headed out there as part of her Research Experiences for Undergraduates (REU) grant and will be working with Greg to make these first measurements of the project. Hopes are high!
29 April 2016 - Visit to Piscataquis County Elementary School
This afternoon I took a car full of Antarctic specimens, artefacts, clothing, and 'artificial ice' to Guilford, ME, and spent a superb couple of hours talking to the 5th grade about Antarctica and what it is like to work there as a scientist. I'm not sure what the most popular/intriguing item is (the 50 year-old Pepsi can or the ice core barrel?), but the students were full of excellent questions and more than willing to don cumbersome polar clothing for fun. It is most fitting that there also happens to be a large glacial erratic right outside the classroom window, evidence of the ice sheet that passed through their town during the last ice age. See the PCES blog for more.
2015-16 Field season - Holly Thomas' field blog
Between November 2015 and January 2016, Holly, an Earth Science undergraduate, travelled to Antarctica as an integral part of our team. This was Holly's first trip to the Antarctic and you can read all about it via her highly descriptive, often hilarious field blog, which is archived on the UMaine Glacial Geology and Geochronology news page. Just scroll down the page until you find it.
28 September 2015 - 'UMaine Research Professor headed to Antarctica' WABI News