People: Astrobiology Faculty

Stephen Warren
Atmospheric Sciences

I was trained as a physical chemist, with a minor in biology. I then worked in molecular biology, to solve atomic structures of proteins and viruses. But I had a competing interest in earth science, so after four years as a postdoc I went for retraining in atmospheric physics. In 1982 I accepted a position as assistant professor of geophysics and atmospheric sciences at UW, teaching climate, atmospheric radiation, and glaciology, and conducting research on radiative processes in climate, particularly the interaction of solar radiation with snow, sea ice, and clouds. The UW Astrobiology program now offers the opportunity to link my current research in geophysics to my former training in biology.

My Astrobiology-related work falls into the category of earth history. I am investigating surface processes on the frozen ocean of Snowball Earth, with a focus on the reflection (albedo), absorption, and transmission of solar radiation by the different surface types. These radiative properties determine (a) the drawdown of atmospheric CO2 necessary to initiate the snowball catastrophe, (b) the critical latitude for the ice-albedo instability, (c) the surface temperatures on Snowball Earth, (d) the duration of a snowball event (how much CO₂ is needed to warm the climate to melt the ice), and (e) the equilibrium ice thickness, which constrains the potential refugia for photosynthetic life. We are measuring albedos of modern surrogates of the snowball ocean for use in climate modeling.

Website: http://www.atmos.washington.edu/~sgwgroup/

Publications

Warren, S.G, R.E. Brandt, T.C. Grenfell, and C.P. McKay, 2002: Snowball Earth: Ice thickness on the tropical ocean. J. Geophys. Res. (Oceans), 107, C10, 3167, doi:10.1029/2001JC001123.

Warren, S.G., and S.R. Hudson, 2003: Bacterial activity in South Pole snow is questionable. Applied and Environmental Microbiology, 69, 6430-6431.

Warren, S.G., and R.E. Brandt, 2006: Comment on "Snowball Earth: A thin-ice solution with flowing sea glaciers" by David Pollard and James F. Kasting. J. Geophys. Res., 111, C09016, doi:10.1029/2005JC003411.

An Australian postage stamp commemorating my experiment to measure sea-ice albedo. My student Rich Brandt is on the left; I am on the right. This stamp was one of five commemorating the 50th anniversary of the Australian Antarctic Expeditions. It was sold in post offices across Australia during 1997-8.