NW Greenland was ice-free 400,000 years ago — what does this mean for us?

It is a cylindrical column of ice, extracted using specialized drilling equipment, that provides a historical record of climate and environmental conditions dating back thousands of years.

Obtaining well-dated sedimentary records from ice-free locations during interglacials is a challenging task, primarily due to the presence of modern-day ice cover. 

However, the Camp Century ice core provides a unique exception, containing frozen subglacial sediments suggesting the region was ice-free during the Pleistocene.

Andrew Christ from the University of Vermont and colleagues used cosmogenic nuclide data to estimate the exposure time of the sediments found in the Camp Century ice core.

In other words, by understanding how long the sediments were exposed to cosmic radiation, they were able to gain crucial insights into the timing of events related to the Greenland Ice Sheet's behavior during the Marine Isotope Stage (MIS) 11 interglacial period.

They also conducted luminescence dating on the sediments. This method measures the trapped energy from natural ionizing radiation that accumulates over time in minerals such as quartz and feldspar. 

By analyzing this trapped energy, the scientists estimated when the materials were last exposed to sunlight or heat.

Proof of an ice-free Greenland

Their investigation revealed that the sediments were deposited by flowing water in an ice-free tundra environment during the MIS 11 interglacial.

This means that the area was exposed to sunlight less than 16,000 years earlier, further supporting the idea of an ice-free Greenland during that period.

To comprehend the deglaciation process during MIS 11, the researchers employed a series of ice sheet models. 

The study revealed that to have an ice-free Camp Century location, the melted ice sheet would have added about 1.4 meters to the global mean sea level during the interglacial period, which was between 6 and 13 meters higher than today. 

These findings hold significant implications for our understanding of future climate scenarios. 

"If moderate warmth for 29 [thousand years] during MIS 11 resulted in significant ice loss from Greenland, then rapid, prolonged, and considerable anthropogenic Arctic warming will likely cause melting of the [Greenland Ice Sheet], raise sea level, and trigger additional climate feedbacks in the coming centuries," wrote the authors.

As scientists continue to unlock the mysteries of our planet's past, these discoveries are a stark reminder of the urgent need for climate action to ensure a sustainable future for future generations.

The complete study was published in Science.