Ice Sheets Rapidly Expelling Meltwater Can Produce Deep Underwater Valleys on Human Timescales

Quaternary Science Reviews, 5 October 2022

During the warm period at the end of the last ice age (20,000 years ago), a massive ice sheet over the North Sea melted fast enough to carve out enormous valleys in the ocean floor within several hundred years, much faster than previously thought. Ice sheets typically grow and shrink in a very slow life cycle, on scales that take tens of thousands of years. When an ice sheet retreats, meltwater drains through the ice and merges with a network of streams underneath the ice sheet. Increased meltwater production can strengthen these streams into fast-flowing currents and erode the bedrock beneath the ice sheet. This study shows that the beginnings of these giant valleys can appear within a few decades, an astonishingly short timescale. Valleys carved beneath an ice sheet can either stabilize or destabilize it by controlling how the water flows beneath the ice. If the meltwater flows away in discrete channels, the ice sheet settles firmly on the bedrock; but the spread of meltwater underneath the ice lubricates its slide towards the ocean, aiding the ice sheet’s collapse. Rising global temperatures today are creating similar conditions to those that melted the huge polar ice sheets of 20,000 years ago. This study highlights a currently overlooked process that can rapidly switch on beneath melting ice sheets. Authors underscore the importance of understanding the formation and impact of these valleys to anticipate how Greenland and Antarctica could respond in the future to sustained warming.

https://www.sciencedirect.com/science/article/pii/S0277379122003110?via%3Dihub