(NewsNation) — New research proves the thickest part of the Greenland Ice Sheet is far less impenetrable than previously believed, a problem for seaside cities if the global temperature continues to climb.

The study, published in the Proceedings of the National Academy of Sciences, revealed that the center of the sheet — the world’s second largest — has previously melted and remained melted for long enough periods to result in plant growth, like moss and fungi.

The 2-mile-deep ice core examined in the study was first extracted in 1993. According to researchers, the plant discoveries prove “that tundra vegetation once covered central Greenland, mandating that the island was largely ice-free.”

A historically deiced center of Greenland could foretell a flooded future. Paul Bierman, a University of Vermont geologist, believes this discovery should end all doubt about the ice sheet’s sensitivity to warming.

“There are people … who kept saying, ‘it’s just the edge of the ice sheet, you’re worrying too much,’” he told Inside Climate News. “Now that we have this set of fossils … it completely shuts down the argument of, ‘Oh, don’t worry about the rest of the ice sheet.’”

The sheet has lost a considerable amount of area in the past few decades, with a 2024 Nature study revealing a nearly 2,000 square mile decrease between 1985 and 2022.

That same study suggested that previous estimates of changes to the ice sheet’s mass balance – how much snow and ice is accumulated each year against how much is lost – had been undercounted by as much as 20%.

A fully-melted Greenland Ice Sheet would raise the global sea level by about 23 feet, sinking some coastal cities.

Researchers posit that analysis of these recovered materials can act as “imperfect but important analogs for human-induced climate warming.”