The two glaciers, both part of the west Antarctic ice sheet, originated in the mid-Holocene period, roughly 7,000 to 5,000 years ago, and have remained stable until very recently, according to research just published in Nature Geoscience. That part of Antarctica is retreating and thinning quickly, with the two glaciers melting underneath given deep, warm currents.

A better understanding of the glaciers’ evolution could lessen the uncertainty about the west Antarctic ice sheet’s behavior in future climate change scenarios. The melting of the glaciers could trigger extensive ice loss in that part of Antarctica, which could contribute as much as 3.4 meters to global sea level rise over the next few centuries.

The study focused on beaches on three islands in the Amundsen Sea Embayment. Researchers performed radiocarbon testing on shells dating back as much as 5,500 years ago, when the beaches were formed. By testing shells found at different elevations on the islands, scientists were able to calculate the level of the sea over time.

The resolution of the sea level recorded does not account for marginal fluctuations of the two glaciers, scientists said. But there is no evidence that the Thwaites and Pine Island glaciers were substantially smaller than today at any point over the past 5,500 years. DM/OBP

Laura Millan Lombrana in Madrid