Can extreme melt destabilize ice sheets?

Researchers have deciphered a trove of data that shows one season of extreme melt can reduce the Greenland Ice Sheet's capacity to store future meltwater - and increase the likelihood of future melt raising sea levels. Nearly a decade ago, global news outlets reported vast ice melt in the Arctic as sapphire lakes glimmered across the previously frozen Greenland Ice Sheet, one of the most important contributors to sea-level rise. Now researchers have revealed the long-term impact of that extreme melt. Using a new approach to ice-penetrating radar data, Stanford University scientists show that this melting left behind a contiguous layer of refrozen ice inside the snowpack, including near the middle of the ice sheet where surface melting is usually minimal. Most importantly, the formation of the melt layer changed the ice sheet's behavior by reducing its ability to store future meltwater. The research appears April 20. "When you have these extreme, one-off melt years, it's not just adding more to Greenland's contribution to sea-level rise in that year - it's also creating these persistent structural changes in the ice sheet itself," said lead study author Riley Culberg, a PhD candidate in electrical engineering.