Looking back 45,000 years ago, the long ribbon of ice that drains the gigantic Greenland Ice Sheet was smaller than it is now. Presently, it measures 600 km in length. A new study suggests it was in the Holocene period when the sheet got small because of the warmth. But the ice was again getting smaller even in the coldest period, found researchers.
The Northeast Greenland Ice Stream (NEGIS) is sensitive to changes in the environment, says the study published today in Nature Communications.
History Repeating Itself
Geologist Anders Carlson (Oregon State University), is the co-author of the study. He explains more about their findings on NEGIS:
“There are some parts of the ice sheet that are relatively stable and others that show evidence of very rapid retreating — a pattern we’re seeing today as well as thousands of years ago. Some of it relates to bed topography—when the bed is below sea level, it stabilizes that part of the ice sheet. In low spots, it is unstable.”
Carlson also mentions that there are other factors for the ice mass loss. He argues that 9,000 years ago, the Earth was closer to the sun, significantly warming the planet. But ice was lost also in a very cold weather, approximately 41,000 – 26,000 years ago.
Co-author of the study and OSU paleoclimatologist Christo Buizert reconstructed the weather in the coldest periods and found out that even though temperatures were colder, summer time was warmer, thus causing ice to melt.
Carlson added that the “period was also quite dry and there wasn’t nearly as much snowfall, which may have driven the ice margin to be smaller.”
Finding the Margins of the Ice Sheet
Carlson added that they can determine what were the margins of the ice sheet in the past. They can do that by looking at the rocks that suffered from ‘sunburn’. When ice retreated, rocks were exposed to cosmic rays, creating beryllium-10 by splitting the elements in the rock.
Nicolaj Larsen (Aarhus University, Denmark) is the lead author on the study. He says the ice is retreating fast:
“Modern observations have shown that the NEGIS is very susceptible to changes in both air and ocean temperatures and is presently in a phase of rapid ice retreat.”
However, Carlson added that they didn’t predict the retreat of the ice until the end of the century.
Rex Austinwas born and raised in Thunder Bay Ontario on the shores of Lake Superior. Apart from running his own podcast (Ice Fishing And Other “Cool” Things), he spends his time canoeing and backpacking in Northern Ontario.. As a journalist Rex has published stories for Global News (Thunder Bay) we well as Buzz Feed and Joystiq. As a contributor to Great Lakes Ledger, Rex most covers science and health stories. Contact Rexhere