HR: 1340h
AN: SA53B-1178    [Abstracts]
TI: Using Ancient Earth Climates as a Model for Extrasolar Terrestrial Planets
AU: * Shukla, S P
EM: sps246@nyu.edu
AF: New York University, Andre & Bella Meyer Hall of Physics New York University 4 Washington Place, New York, NY 10003 United States
AU: Seager, S
EM: seager@dtm.ciw.edu
AF: Carnegie Institution - Department of Terrestrial Magnetism, 5241 Broad Branch Road, NW, Washington, DC 20015-1305 United States
AU: Chandler, M
EM: mac59@columbia.edu
AF: Columbia University - CCSR/GISS, 2880 Broadway, New York, NY 10025 United States
AU: Shopsin, M
EM: shopsinm@panix.com
AF: Columbia University - CCSR/GISS, 2880 Broadway, New York, NY 10025 United States
AB: One of the greatest discoveries of this century will surely be the detection of an Earth-like extrasolar planet, orbiting in a "habitable zone" around its host star. NASA's Terrestrial Planet Finder (TPF) is being designed to detect and characterize Earth-like planets around nearby stars. Because extrasolar planets are so distant, they will appear only as point sources. Therefore, any observable quantities, such as obtained spectra, will be spatially integrated over an observed planetary hemisphere. Earth's spectral signature has changed throughout its climatic evolution, and hence, we have many examples of "Earth as an extrasolar planet" to study. A study of Earth paleoclimates and their hemispherically integrated radiative signatures will provide insight into the range of habitable environments that could exist on Earth-like extrasolar planets. Such a range is key to ensure that TPF can detect and characterize a wide range of Earth-like planets, and may even discern their climates and habitability. In this study, we utilize the 3D NASA Goddard Institute for Space Studies Model II General Circulation Model (GCM) to simulate Earth-based paleoclimatic conditions. We then use the diagnostic output from the GCM (such as temperature, specific humidity, albedo, cloud cover, snow and ice cover) in a line-by-line radiative transfer code to compute planetary spectra and other radiative signatures for our simulations. We chose to focus on cold climate variations, specifically simulations of the Last Glacial Maximum and Neoproterzoic glaciations (e.g., "snowball Earth"), for we expect that the more extreme climate variations may produce the most distinctive radiative signatures, quite discernable from our modern signature. For example, we found that our Neoproterzoic simulation produced a 94.6% increase in snow and ice cover from the modern run, which had dramatic radiative effects. We present our results on the spectral signatures of various paleo-Earth climate simulations in comparison to modern-day Earth.
DE: 3309 Climatology (1616, 1620, 3305, 4215, 8408)
DE: 3359 Radiative processes
DE: 5210 Planetary atmospheres, clouds, and hazes (0343)
DE: 5225 Early environment of Earth
SC: SPA-Aeronomy [SA]
MN: Fall Meeting 2005