Exploring Antarctica's Frozen Past

David Pollard, EESI senior scientist, uses ice-sheet models to understand variations of the past.

By coupling and applying these models in innovative ways, Pollard has developed new modeling techniques that allow current knowledge about floating ice shelves to be integrated into existing ice-sheet models. With these, he has simulated the advance and retreat of the grounding line - where floating ice shelves and grounded ice meet - of the West Antarctic ice shelves.

Using those methods, Pollard and Robert DeConto, professor of geosciences at the University of Massachusetts, have modeled the past 5 million years of West Antarctic ice sheet variations.

Pollard’s and DeConto’s results compare well with the recently obtained sediment core record of the ANtarctic geological DRILLing (ANDRILL) project. Together, the results show that the West Antarctic ice sheet has collapsed, re-formed and grown many times over the last several millions years largely in response to warming and cooling ocean temperatures. Their research also shows that the East Antarctic ice sheet is considerably more stable.

Pollard was one of the main developers of the Genesis GCM when he was an associate scientist at the National Center for Atmospheric Research (NCAR) in the early 1990s. Besides the Genesis GCM, he also works with the RegCM3 regional climate model, equilibrium vegetation models and the MOM2 ocean general circulation model to investigate paleoclimate problems such as warm greenhouse intervals in Earth’s geologic past.
 
One of Pollard’s next projects is to include West Antarctic subglacial lakes in his models. These lakes, numbering to date as many as 150, may help to explain ice sheet changes over deep time.

Other research projects:
Investigating Climate System Sensitivity to Orbital Forcing. “For this project with Chris Poulsen (University of Michigan), we will be running global climate models and ice sheet models to look at several hyotheses about climate change in the Quaternary. We will use existing data to test how orbital changes affect climate and ice sheets.”
 
ANDRILL Stratigraphic Drilling for Climate and Tectonic History: “Rob DeConto and I are part of the modeling team for the ANDRILL project. We are comparing our results with the project’s sediment core records in West Antarctica that represent ice-sheet fluctuations of the last ~15 million years.”