Calendar Event Details
April 6, 2005 - Code 613.2 Branch Seminar
Event Date: Wednesday, April 6, 2005
University of Michigan
When: Wednesday, April 6, 2005, 3:15 PM
Where: Building 33, Room H114, Goddard Space Flight Center, Greenbelt, Maryland
Drilling on the Earth and the Moon for new insights into global climate change
The subsurface thermal regime of a planetary body such as Earth and the Moon is controlled in part by the temperature history at the surface. Subsurface temperatures comprise an archive of past temperature changes at the surface that is complementary to the instrumental record and traditional climate proxies. From a global perspective, climate reconstruction based on the global database of borehole temperatures indicates a temperature increase over the past five centuries of about 1 K, half of which has occurred in the 20th century alone. The magnitude of ground surface warming documented in the borehole temperatures is greater in the Northern Hemisphere than in the Southern Hemisphere. An integrated reconstruction based on some 700 boreholes, the 20th century meteorological record, and a multi proxy model shows a long-term accelerated warming towards the present day. The integration of the complementary climate information greatly improves the comparability of the reconstructed surface temperature and the radiative forcing series, and suggests a greater climate sensitivity to external forcing. The geothermal approach to the study of ground surface temperature history of Earth can be easily adapted to the study of a lunar surface temperature history which is related to the history of solar activity. Due to the absence of biosphere and atmosphere, subsurface temperature is the only known proxy for a reconstruction of a climate history on the Moon. Indeed, the near surface environment of the Moon is even more favorable to the application of the geothermal method. Most of the lunar surface is covered with a regolith layer of several meters to tens of meters in thickness. The lunar regolith is much easier to be penetrated than rocks. A temperature measurement from a borehole on the Moon is free of perturbations such as land cover and ground water that have been seen in a borehole measurement on Earth. Additionally, lunar regolith has an extremely low thermal diffusivity, and therefore, the downward climate signal propagation within the regolith layer is extremely slow. A subsurface temperature profile of twenty or thirty meters may preserve information of lunar surface temperature changes over hundreds of years. Long-term temperature measurements from the Apollo 15 landing site and synthetic numerical experiment illustrate the great potential of the Moon as a new platform for the study of solar radiation and terrestrial climate change.