Luncheon – August 4, 2006

Title: Ice Cores from Greenland and Antarctica: Climate Change in the Earth’s Past

Speaker: Todd K. Hinkley, USGS

Date: August 4, 2006

Publication: The Outcrop, August 2006, p. 4

The National Ice Core Laboratory in Lakewood has 15,000 1-meter tubes of ice cores, drilled from the ice covered regions of the world, Greenland and Antarctica. In these places the ice has reached a thickness of about two miles, as annual thicknesses of snowfall accumulate one on top of another, without melting. Drilling is done in three-month “summer” seasons in the interior of the ice sheets, supported by wheel/ski Hercules C-130 aircraft of the Air National Guard. Ice is brought to the Colorado lab by plane, by refrigerated shipboard containers, and finally by refrigerated truck.

The ice gives detailed information on the earth’s climate and atmosphere, over the past half-million years. With current interest in the possibility of climate changes in the future, the ice can tell us what kind of changes really have occurred in the past. Increasingly sophisticated chemical and physical tests on the ice can reveal increasingly varied information about the earth’s past, such as how cold the oceans were, and how much sea ice covered the oceans in ancient times. But two “bread and butter” types of information have come from the ice cores since drilling began in the 1960s, and accelerated through the 1980s and 1990s: we can tell in detail the composition of the past atmosphere (including amounts of “greenhouse gasses”), and we can tell how hot and cold it was on the earth. The air composition is revealed through “tiny bubbles” trapped in the ice, as the open spaces in snow are gradually sealed off after deep burial. Past temperatures are revealed by measuring how much “heavy water” (of World War II German A­-bomb effort fame) is in the ice. Other records of past conditions on earth, from tree rings, corals, oceans sediments, and stalactites in caves, also give good information about past conditions on earth. But ice cores are unique in giving a detailed record of the past atmosphere, and details of surprisingly rapid changes in past temperature.

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