Ice Sheets and Global Climate
Dr. Simon Brassell
IU Department of Geological Sciences and
the School of Public and Environmental Affairs
December 7, 2006
Ice sheets are barometers of global climate, varying with changes in global temperatures. Satellite and other data reveal that both the vast Greenland ice sheet and Arctic sea ice have thinned in the recent past, and massive sections of the west Antarctica ice shelf have calved into the ocean. However, the extent and thicknesses of ice sheet have waxed and waned through successions of ice ages, affecting sea level, Earth's reflectivity, and formation of the cold, salty, dense water that is the starting point of the global conveyor that drives deep ocean circulation. The ice sheets themselves serve as recorders of climate change preserving evidence for variations in tiny bubbles of air trapped within the annual layers of ice. Thus, ice cores collected from Antarctica and Greenland provide records of ancient atmospheres that now extend back almost 800,000 years. They reveal temporal fluctuations in carbon dioxide and global temperatures that parallel the sequence of glacial cycles recognized from independent geochemical records preserved in ocean sediments. Such examination of past climates shows the current pace of global climate change is unprecedented, and atmospheric levels of CO2 are now higher than at any time in the past 800,000 years, and perhaps many million of years. These observations are consistent with expectations from anthropogenic burning of fossil fuels, and enable development of scenarios that can characterize future global warming.
Simon Brassell received both a B.Sc. first class honours degree in Chemistry and Geology in 1976, and a Ph.D. in Organic Geochemistry in 1980 from the University of Bristol in the U.K. He was a Royal Society Research Fellow there before moving to the U.S., first at Stanford University before moving to Indiana University in 1991. Professor Brassell's research and teaching focus on evidence for past and present climate change from sediment and rock records. He pioneered the development of molecular proxies now widely used as measures of ancient sea surface temperatures.
Web links:
Recent news articles on ice sheets:
"Antarctic Ice Sheet Is Melting Rapidly"
http://www.washingtonpost.com/wp-dyn/content/article/2006/03/02/AR2006030201712.html
"Polar ice sheets show net loss"
http://news.bbc.co.uk/2/hi/science/nature/4790238.stm
"Impact of Climate Warming on Polar Ice Sheets Confirmed"
http://www.nasa.gov/vision/earth/environment/ice_sheets.html
"Greenland Ice Sheet On A Downward Slide"
http://earthobservatory.nasa.gov/Newsroom/NasaNews/2006/2006101923416.html
Recent news articles on ice cores as records of climate
"Ice cores unlock climate secrets"
http://news.bbc.co.uk/2/hi/science/nature/3792209.stm
"Deep ice tells long climate story"
http://news.bbc.co.uk/2/hi/science/nature/5314592.stm
"Antarctic Ice Core Reveals Climate Link with Greenland"
http://www.spiegel.de/international/spiegel/0,1518,448089,00.html