Greenland has lost more ice than previously thought: Study

Greenland

Climate change has caused Greenland's ice sheet to lose 20 percent more ice than previously thought, according to research published Wednesday that used satellite imagery to track the retreat of glaciers over the past four decades.

Previous studies have found that about 5,000 gigatons of ice has been lost from the surface of the Greenland ice sheet in the past two decades, a major contributor to rising sea levels.

In the new study, researchers in the United States compiled nearly 240,000 satellite images of glacier terminus positions—where glaciers meet the ocean—from 1985 to 2022.

"Nearly every glacier in Greenland has thinned or retreated over the past few decades," lead author Chad Greene, a glaciologist from NASA's Jet Propulsion Laboratory, told AFP.

"There really aren't any exceptions, and this is happening everywhere, all at once."

They found that over 1000 gigatons (1 gigaton is equivalent to 1 billion tons), or 20 percent, of ice around the edges of Greenland had been lost over the past four decades and not been accounted for.

"The Greenland ice sheet has lost appreciably more ice in recent decades than previously thought," researchers said in the journal Nature.

Because the ice at the island's edges is already in the water, the authors stressed that this would have had a "minimal" direct impact on sea level rise. But it could herald further overall ice melt, allowing glaciers to more easily slip towards the sea.

Researchers found that the Greenland glaciers most susceptible to seasonal changes—that is expanding in winter and retreating in summer—are also the ones most sensitive to the impact of global warming and experienced the most significant retreat since 1985.

The melting of Greenland's vast ice sheet—the world's second-largest after Antarctica—is estimated to have contributed more than 20 percent to observed sea level rise since 2002.

Rising sea levels threaten to intensify flooding in coastal and island communities that are home to hundreds of millions of people, and could eventually submerge whole island nations and seafront cities.

Warming

The previous year marked the hottest on record, with Copernicus, Europe's climate monitor, noting persistently and unusually high ocean temperatures. In 2023, the Arctic, warming at a rate approximately four times faster than the global average, experienced its warmest summer ever, primarily attributed to accelerated human-induced climate change.

The atmospheric warming contributes to glacier surface melting, creating a pathway for ice loss. As the melted water seeps to the base of the ice sheet, it facilitates the sliding of ice into the ocean, likened to water between a tire and the road, as explained by Greene.

The warming of oceans, absorbing about 90 percent of excess heat from human-driven carbon pollution, is interconnected with the melting of critical ice shelves supporting Greenland and Antarctica's vast ice sheets.

Concerns have been raised regarding potential repercussions, including the disturbance of deep-water currents crucial for global weather patterns. The influx of additional freshwater into the ocean from melting ice could impact the Atlantic Meridional Overturning Circulation (AMOC), a vast system regulating the global transfer of heat from the tropics to the northern hemisphere.

A consortium of international scientists cautioned last year that changes in AMOC and melting ice sheets are among approximately two dozen climate tipping points, posing an "unprecedented" threat to humanity.

Source: Phys.org