Paleo Slide Set: Polar Ice Cores
Midnight sun.
During the midnight sun, twilight keeps the Greenland Ice Sheet illuminated well into the 
early morning. Scientists have come here, to the interior of Earth's largest island, to unlock 
important clues about Earth's climatic history. Nearly two miles above sea level, the summit 
of the Greenland Ice Sheet is high, bleak, and as cold as it looks in this photo. During the 
short summer field season when scientists occupy nearby drilling sites, air temperatures range 
from -20 to 0 degrees C, but may drop as low as -40 degrees C. 

Photo Credits:
Bruce Vaughn 
Institute of Arctic and Alpine Research (INSTAAR), University of Colorado at Boulder.