Jim White, director of the Institute of Arctic and Alpine Research at the University of Colorado, Boulder, and the lead U.S. investigator on the NEEM project, said that while three previous ice cores drilled in Greenland in the last 20 years recovered ice from the Eemian, the deepest layers were compressed and folded, making the data difficult to interpret.
With this study, although there was some folding of the lowest ice layers in the NEEM core, sophisticated ice-penetrating radar helped scientists sort out and interpret the individual layers to paint an accurate picture of the warming of Earth's Northern Hemisphere as it emerged from the previous ice age.
"When we calculated how much ice melt from Greenland was contributing to global sea rise in the Eemian, we knew a large part of the sea rise back then must have come from Antarctica," said White. "A lot of us had been leaning in that direction for some time, but we now have evidence that confirms that the West Antarctic ice sheet was a dynamic and crucial player in global sea rise during the last interglacial period."
The intense surface melt in the vicinity of NEEM during the warm Eemian period was seen in the ice core as layers of re-frozen meltwater. Meltwater from surface snow had penetrated the underlying snow, where it re-froze. Such melt events during the past 5,000 years are very rare by comparison, confirming that the surface temperatures at the NEEM site during the Eemian were significantly warmer than today, said the researchers.
The Greenland ice core layers--formed over millennia by compressed snow--are being studied in detail using a big suite of measurements, including stable water isotope analysis that reveals information about temperature and moisture changes back in time. Lasers are used to measure the water stable isotopes and atmospheric gas bubbles trapped in the ice cores to better understand past variations in climate on a year-by-year basis--simila
|Contact: Peter West|
National Science Foundation