The recent retrieval of a 218-meter sediment core from Antarctica's Crary Ice Rise by an international team of scientists and technicians is a groundbreaking achievement. This core, retrieved after two failed attempts, offers a unique window into the past, revealing the history of the West Antarctic Ice Sheet and its response to warmer climates. The excitement surrounding this discovery stems from the core's potential to provide insights into the ice sheet's sensitivity to global warming and its impact on sea levels.
The sediment core, a record-breaking length, was drilled through 523 meters of ice at a distance of 700 kilometers from the nearest base. The core's location at the Crary Ice Rise, where the West Antarctic Ice Sheet juts out over the bedrock of the Antarctic continent, is crucial. This ice sheet, a massive glacier, plays a significant role in global sea level rise when it shrinks, adding fresh water to the ocean. The team's primary question was: what has happened to the ice sheet in the past during warmer climates, and how can this inform our predictions for the future?
The core's composition, a mix of fine glacial flour, cobbles, and boulders, indicates the presence of both ice and open water. The sedimentologist, Dr. Georgia Grant, explains that different types of sediments found in the core point to various past environments. Microfossils, studied by Amy Leventer from Colgate University, provide crucial age estimates. These microfossils, remains of tiny single-celled photosynthetic algae called diatoms, help determine the age of the sediments with precision.
The age estimates show that most of the recovered core spans 7-10 million years ago, with the final 20 meters dating back to 17-19 million years ago. This period, the Miocene, was significantly warmer than today, by at least three degrees Celsius. The core's findings align with the Paris Climate Agreement's goal of limiting global warming to below 2 degrees Celsius, but current global policies are projected to lead to a 2.6-degree rise by 2100.
The project aimed to investigate the sensitivity of the West Antarctic Ice Sheet to 2 degrees of warming by looking back to the middle Pliocene, around three million years ago, when average global temperatures were 2-3 degrees warmer. While the core does not contain sediments from that exact age, the team hopes to find resources for another site that might have younger sediments. The discovery of open ocean conditions in a region currently covered by a massive ice shelf is particularly striking, challenging our understanding of the region's history.
The sediment core's significance lies in its ability to provide a detailed record of past climate conditions and the ice sheet's response. However, Associate Professor Molly Patterson emphasizes the need for more sediment cores from other areas to gain a comprehensive understanding. Co-chief scientist Associate Professor Huw Horgan agrees, stating that the ideal outcome would be to stop warming the planet. This discovery highlights the importance of continued research and the need to address the root causes of climate change to ensure a sustainable future.
