Nearly eighty percent of Greenland is covered by ice that run thousands of feet thick. Greenland’s ice has grown and shrunk over the years, resulting from the variations from the climate. The truth lies is that mapping out the history of these changes is merely impossible. Countless research had been done over the years, however, often times, as the researchers dug deeper into Greenland’s past, the more tangled the history became.
Two new studies published in Nature recently illustrate some of the difficulty scientists face while studying changes to the Greenland ice sheet. A study conducted by Joerg Schaefer suggests that Greenland was almost entirely ice free for long periods of time over the last 2.6 million years. Another study conducted by Paul Bierman, on the contrary, suggests that East Greenland’s ice sheet has been stable for the past 7.5 million years.
Instability of Greenland’s Ice Sheets
Schaefer initially examined rock cores that were drilled from under the ice sheet in 1993, focusing of finding different set of isotopes called cosmogenic nuclides. These isotopes would indicate that the rock was released from its “icy prison” at some point in history.
Cosmic rays are constantly bombarding the Earth from all directions. When these rocks are exposed to these cosmic rays, the rocks’ atomic structure can generate the isotopes eryllium-10 and aluminum-26, the cosmogenic nuclides Schaefer was specifically looking for.
Ice sheets serve as shields, preventing any cosmic rays from hitting the bedrock. Since Greenland’s ice sheet ranges over 9000 feet thick, it is too thick for cosmic rays to pass through. However, Schaefer found cosmogenic nuclides in the bedrock, suggesting that the bedrock must have been exposed to cosmic rays at some point in the past.
Schaefer suggests that Greenland may have been nearly ice-free for 280,000 years before it began freezing again about 1.1 million years ago. Data collected from Schaefer and his colleagues found that ice sheet melted and refroze multiple times over the past few million years, indicating that ice sheet is much less stable than previously anticipated. Schaefer argues that current models created by glaciologists are far too stable and do not represent the instability of the bedrock.
Ice Sheet Stability
Bierman on the contrary, beryllium-10 in the core samples and found that the concentration of the isotope dropped over time. He argues that there must have been a near-constant ice cover over the land during the 7.5 million year period. However, there are multiple limitations to his findings as his study looks at the averages over long periods of time. However, Bierman argues that short-term changes aren’t seen but instead, we seen long-term overall trends.
How do we decipher between these two conclusions?
Simple! Both Schaefer and Bierman both suggest that these results just indicate the importance of how much further research is needed to be done to uncover the entire truth. Schaefer in particular, emphasizes the importance of collaboration and focusing on further studies that map the history of Greenland’s entire ice sheet.