Greenland melted recently: High risk of sea level rise today

 A large portion of Greenland was an ice-free tundra landscape -- perhaps covered by trees and roaming woolly mammoths -- in the recent geologic past (about 416,000 years ago), a new study in the journal Science shows. The results help overturn a previous view that much of the Greenland ice sheet persisted for most of the last two and a half million years. Instead, moderate warming, from 424,000 to 374,000 years ago, led to dramatic melting. At that time, the melting of Greenland caused at least five feet of sea level rise, despite atmospheric levels of heat-trapping carbon dioxide being far lower than today (280 vs. 420 ppm). This indicates that the ice sheet on Greenland may be more sensitive to human-caused climate change than previously understood -- and will be vulnerable to irreversible, rapid melting in coming centuries.

The scientists -- from the University of Vermont (UVM), Utah State University, and fourteen other institutions -- used sediment from a long-lost ice core, collected at a secret U.S. Army base in the 1960s, to make the discovery. They applied advanced luminescence and isotope techniques to provide direct evidence of the timing and duration of the ice-free period.

A Green Land

During the Cold War, a secret U.S. Army mission, at Camp Century in northwestern Greenland, drilled down through 4560 feet of ice on the frozen island -- and then kept drilling to pull out a twelve-foot-long tube of soil and rock from below the ice. Then this icy sediment was lost in a freezer for decades. It was accidentally rediscovered in 2017 and shown to hold not just sediment but also leaves and moss, remnants of an ice-free landscape, perhaps a boreal forest.

But how long ago were those plants growing -- where today stands an ice sheet two miles thick and three times the size of Texas?

An international team of scientists was amazed to discover that Greenland was a green land only 416,000 years ago (with an error margin of about 38,000 years).

Their new study was published in the journal Science on July 21, 2023.

Source: ScienceDaily