"Ten million atoms isn't cool, you know what's cool? Ten thousand atoms" *
Current Research Projects
The last ice age in Antarctica
During the last glacial maximum, ice advanced across the continental shelf around Antarctica, and filled the Ross, Weddell and Amery embayments. The ice sheet thickened most around the margins, raising ice levels at the present grounding line by up to 1000 m in places. In the deep interior, lower snowfall resulting from the colder atmosphere and more extensive sea ice cover surrounding the continent restrained thickening, typically to no more than a few tens of meters. Debris carried to the ice-sheet margins left moraines and drift sheets that mark out the former limits of the ice sheet. We have used cosmic-ray-produced nuclides to determine the age of these deposits in the Prince Charles Mountains and around the East Antarctic coast, in Marie Byrd Land, and alongside several of the large glaciers that cut through the Transantarctic Mountains. At Reedy, Scott and Beardmore Glaciers, and several sites in the Amery Embayment, glacial maximum ice reached its highest level around 18 kyr BP, several thousand years after the culmination of northern hemisphere glaciation. Retreat was more complicated, ending by ca. 10 kyr BP in the Prince Charles Mts and along the East Antarctic Coast, but continuing into the late Holocene (2-3 kyr BP) in Marie Byrd Land and the southern Transantarctic Mts.
Cosmogenic nuclide calibration
We seem to do a lot of this. As part of the NSF-supported CRONUS project we measured several hundred calibration samples for Be-10, Al-26 and Cl-36. In parallel with these experimental efforts, Dave Argento used the radiation transport code MCNPX to simulate the complicated physics of cosmogenic nuclide production. The result is a detailed model of cosmic ray energy spectra over full ranges of altitude, cut-off rigidity and zenith angle, and coupled with excitation functions to predict production rates of all commonly measured nuclides.