Ph.D. Meteorology, University of Melbourne, 2001
Atmospheric and Oceanic Sciences
Global climate modeling, cycles of water and carbon, polar climate variability, large-scale dynamics of the atmospheres and oceans
Current Research: Improving estimates of past climate by study of processes controlling isotope ratios in ice cores
The stable isotopic records from snow in Greenland stand as the gold
standard for understanding climate variations in the Arctic during the last
100,000 years. While the basic tenets that underlie interpretation of isotopic information appear robust in a mean sense, many specific meteorological and glaciological processes can confound simple interpretations. Processes of interest include variations in moisture sources, cloud processes, surface
ablation, blowing snow, and vapor diffusion in the firn. The limitations exist because direct measurements to evaluate the influences of processes have been lacking. With advanced instrumentation and an understanding of cloud and snowpack physics, we can now resolve fundamental uncertainties on the controls on the isotopic composition of the ice sheet. In recent accomplishments, we used isotope ratios from layers of snow that build up the ice sheet to understand climate history. The signal, however, is far more complex than simply understanding the weather conditions at the time snow is formed. The figure shows that while the individual layers are easily observable though optical imaging of the snowpack and simple density measurements, the isotope ratios reflect a different history associated with molecular exchange both within the snowpack and exchange between surface snow and ambient vapor. Our results challenge existing interpretations of polar ice-core records because the vapor-exchange process is larger than previously considered. The findings strengthen previous interpretations because of the more complete accounting for relevant physics rather than focusing only on correlations with temperature.