The Greenland Ice Sheet from space, taken by a NASA satellite.USGS
Approximately 400,000 years ago, some areas of Greenland that are now covered by a thick layer of ice were exposed to fresh air and sunlight. Today, the Greenland Ice Sheet covers most of the land mass, but the southwestern coastline is ice-free. Back then, the northwest was too.
Records of this period come from sediment and ice samples collected in the 1960s. They were all but forgotten until 2019, when an international team of scientists embarked on a collaborative effort to understand modern climate change by tracking climate over longer periods of time.
The process is captured in "The Memory of Darkness, Light and Ice," a documentary film that debuted on streaming services such as YouTube, Apple TV and Amazon Prime this fall. Director Kathy Kasic, a former evolutionary biologist, travelled to labs around the world - including at the University of Washington - to interview and film scientists as they deciphered clues about the past from old ice and sediment samples.
These samples were collected during the Cold War at a U.S. military base in Greenland. Camp Century - established in 1959, about 150 miles inland and just below the surface of the ice - was used by the U.S. to conduct military operations in secret, and do science on the side. Before Camp Century was abandoned in 1967, the team drilled more than 1,000 meters through the entire ice sheet and into the sediment below.
Eric Steig, a UW professor of Earth and space sciences, is among those featured in Kasic's film. Steig spoke with UW News about the backstory.
How did the project begin? What was your role?
Eric Steig: I was working with a team of researchers led by Paul Bierman at the University of Vermont to develop a plan for analyzing these old sediment and ice samples. We were gathering an international consortium of experts when I ran into Kathy at a scientific meeting and invited her to join us. I had seen her previous work about Antarctica and thought it was fantastic.. Because Kathy was involved early on, she was able to go to all these different labs and see the science unfold in real time.
What did your lab contribute to the research effort?
ES: My lab studies isotopes, which are the different versions of elements. We measure the concentration of heavy and light oxygen and hydrogen in little pockets of water preserved in the sediment. The ratios of those water-isotope concentrations tell us how temperatures have changed. We also analyzed isotopes of carbon and nitrogen, which reflect shifting ecological conditions in the ancient soil.
At the same time, our European colleagues were measuring the ice just above the soil, and we were working together to understand what happened at this transition point. We're using this combination of ecology, chemistry, water and plants to disentangle what the climate was like in more detail. A lot of the work has been published, but some is still underway.
Explore published work:
What has the project accomplished thus far?
ES: It gives us this beautiful window into history that we can use to learn about ice-free conditions. For example, we know there was an extended warm period around 400,000 years ago, from modeling, but now we can also see that reflected in the sediments. It might not have been that much warmer than it is today, but it was warm for a very long time.
There's plenty of evidence now that the Greenland ice sheet is melting and at some point it will be gone. Our research advances our understanding of the ice sheet and it will help us refine the ice-sheet models used to predict sea level rise.
Why did the researchers collect these samples in 1960? Why can't we get more?
ES: At the time, scientists understood the value of water isotopes and their relevance to climate. They observed this clear relationship between temperature and isotope composition that could capture climate though time, but they weren't thinking about global warming.
Fast forward a few decades and these historic samples have immense value in climate science, especially with the advent of modern analytical tools. Those of us who study Greenland would love to put holes in a lot of places to map out exactly how the ice evolved, but drilling is expensive and time consuming. Ice cores are one thing, but sediment and bedrock present new challenges. There have only been a small handful of successful attempts to drill through the ice and sample what is beneath it.
What do you think this film helps to convey?
ES: As a scientific community, we spent decades studying what Earth was like with more ice. I grew up in this era where the questions were about the ice ages. That's no longer the most pressing question. We need to be asking what the Earth was like when there was less ice, because that is where we are heading. The film captures this shift from studying cold periods to studying warm ones.
