The study team, led by researchers at the University of Texas at Austin Jackson School of Geosciences and the University of California, Berkeley, investigated sediment cores from the WAIS to understand the region's past climate and environment during the early portion of the Eocene epoch, roughly 50 million years ago. This time period is significant as it marks a transition between a warm Earth with sea levels much higher than today to one beginning to cool and transition to the icehouse world that now dominates.
Previous research on the WAIS has been limited to drilling ice cores or investigating exposed rock formations and has often focused on the last few million years when ice sheet growth was dominant. Sediments, however, provide an alternative window into the history of the WAIS, but until recently, obtaining these sediments from miles below the ice has not been feasible.
To overcome this challenge, the researchers used a novel approach to obtain the sediment cores. They melted their way through the ice sheet with hot water and then pumped water jets to collect sediment beneath it. This approach is far less invasive than traditional ice drilling and allows the researchers to analyze sediment from locations that were previously inaccessible.
The cores revealed a wealth of information about the paleoenvironment of the region. Grain size analysis, geochemical compositions, and microfossil abundance provided insights into the nature of the sediments. For instance, the presence of rounded quartz sand with feldspar and mica indicates the existence of a river delta or estuary where sediments from terrestrial sources were deposited and distributed by water currents.
"The cores were full of surprises. Finding this extensive river system underneath the ice was not one we might have easily predicted," said lead researcher Reed Scherer.
The implications of these findings go beyond the history of the WAIS. They have important implications for our understanding of the role of Antarctica in global climate change and sea-level rise.
Understanding the conditions under which the WAIS might collapse and contribute significantly to global sea levels involves projecting how much ice it might lose under similar conditions to those observed during past warm climates, like the warm Eocene. Therefore, discovering that significant portions of the WAIS were above sea level and susceptible to erosion in the geologic past provides further evidence that the current ice sheet is vulnerable if Earth were to warm to such temperatures again in the future.
