Jeremy D. Shakun, a paleoclimatologist and Assistant Professor in the Department of Earth and Environmental Sciences at Boston College, recently co-authored a research article detailing the climatological history of the Greenland ice sheet dating back 7.5 million years. Published in the Dec. 8 edition of Nature, a weekly science journal, Shakun’s study demonstrates that the ice sheet has historically melted and reformed in response to temperature fluctuations and can be a useful tool in global climate change research.
Professor Shakun’s research article, “A Persistent and Dynamic East Greenland Ice Sheet over the Past 7.5 million Years,” co-authored with Paul R. Bierman and Lee Corbett of the Rubenstein School of the Environment and Natural Resources at the University of Vermont, Susan Zimmerman of the Lawrence Livermore National Laboratory, and Dylan Rood of Imperial College London, explains that scientists’ current “understanding of ice-sheet variations before the last interglacial 125,000 years remains fragmentary.”
The research team sought to bring clarity to existing historical and empirical data concerning early Greenland glaciation. Some data collected over the years implies that East Greenland glaciers initially reached the coast approximately 7.5 million years ago, while marine sediments suggest the process of glaciation in East Greenland commenced 11 million years ago. To that end, the data on ice sheet erosion dynamics in the region has long been unclear.
Using the Center for Accelerator Mass Spectrometry, the team analyzed the isotopes “that were found in the quartz sand from ice-rafted debris in sediment cores” of the ice sheet, according to an article on the subject from phys.org.
The isotopes studied are typically created when bedrock interacts with cosmic rays. Shakun and his team analyzed the two elements made by the cosmic-ray interaction to calculate how long the rocks being studied had been in contact with the sky or were otherwise covered under an overlaying sheet of ice in light of changing global temperatures.
Results indicated that the ice sheet on the eastern side of Greenland has not completely melted for long in the past several million years and that the island has been scoured by glacial activity frequently over the past 7.5 million years.
Additionally, the researchers discovered that during global climate cool-down periods over the course of the past several million years, glacial activity moved to previously “ice-free” areas, which showed that the ice sheet in East Greenland exhibited a phenomenon whereby it responded to, and even tracked, global climate change, suggested Paul Bierman in a news release.
“The melting we are seeing today may be out of the bounds of how the Greenland ice sheet has behaved for many millions of years,” Bierman said.
In the same news release, Professor Shakun also asserted that the ice sheet had been around continuously for the past seven million years, according to their research and outside data.
Professor Shakun and the research team intend to continue studying rock samples to develop a more comprehensive history of glacial activity and its correlation to global climate change.