Greenland’s ice shelves have shrunk by more than a THIRD since 1978 – and will cause global sea levels to rise by 6.8 FEET if they collapse entirely, study warns

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Greenland’s ice shelves have lost more than a third of their volume since 1978, researchers have warned.

Warmer ocean waters have accelerated the disintegration of vital ice shelves, causing them to melt from below and increasing their risk of collapse.

Of the eight ice shelves that support the vast glaciers of northern Greenland, three have already collapsed completely, while the remaining five have retreated rapidly.

As ocean temperatures continue to rise, scientists say ice shelves will continue to retreat, with dire consequences for global sea levels.

If they disappeared entirely, these ice shelves could release enough water to raise global sea levels by 6.8 feet (2.1 metres), according to experts from the French National Center for Scientific Research (CNRS).

Greenland’s eight floating ice shelves have shrunk by more than 35 percent since 1978, with three completely collapsing, scientists warn.

Satellite images show the Ostenfeld Ice Shelf as it completely collapsed between 2003 and 2010

Greenland’s ice shelves were previously thought to be stable, unlike more sensitive areas of the polar ice sheet.

However, scientists have used field observations, aerial photography, satellite data, and regional climate models to show that the ice shelves have undergone accelerating collapse.

Since the 2000s, the floating ice shelves of the Zacharia-Eström, Ostenfeld and Hagen-Bray glaciers have completely collapsed.

In 2003, 80% of the Ostenfeld ice shelf collapsed into the sea, resulting in the loss of 6.5 cubic miles (27 km³) of ice.

Likewise, the Hagen Overland collapsed between 2001 and 2005, leaving behind just over a tenth of its original mass.

Greenland’s vast glaciers, shown here in green, meet the sea by passing through a number of fjords where ice shelves act like frozen dams

The Hagen Bræ Ice Shelf went from being relatively stable in the 1980s to completely collapsing, after starting to lose mass in the 2000s.

Greenland Ice Sheet

The Greenland Ice Sheet is one of two continent-wide ice masses on Earth, and is the largest in the Northern Hemisphere.

Nearly 80 percent of Greenland’s land area is covered in ice.

It has an area of ​​656,400 square miles (1.7 million square km), yet it meets the sea only in a few areas where glaciers move down fjords.

If the entire ice sheet melted, sea levels could rise as much as 24 feet, although experts say that scenario is highly unlikely.

Other remaining ice shelves also thinned and shrunk rapidly, with some retreating as much as five miles (8.3 km).

The danger of these collapses is that they will increase The rate at which ice enters the ocean, which can have a huge impact on sea levels.

Ice shelves act like giant frozen dams, preventing glaciers from entering the sea.

Greenland is already responsible for 17.3% of the rise in sea levels between 2006 and 2018.

However, the glaciers in northern Greenland contain enough ice to raise sea levels by 6.6 feet (2.1 metres).

Writing in Nature Communications“Overall, 25% of the ice sheet area is being drained by former or remaining ice shelves, representing a sea level rise equivalent to 2.1 metres,” said researchers led by Roman Milan.

“If northern Greenland’s glaciers lose the support provided by ice shelves, the increase in drainage could rival the largest contributors to Greenland’s ice mass loss.”

Researchers say the driving factor behind the rapid disintegration of the Greenland ice sheet is rising ocean waters Temperatures.

The graph shows how the front of the glaciers on the eight ice shelves retreated over time. The darker green lines show the extent of ice in the 1990s while the whiter lines show more recent extents

Ocean temperatures in western North Greenland rose modestly between 1965 and 2000, rising from 31.8 degrees.°Fahrenheit (-0.1°C) to 32°F (0.0°C).

However, between 2000 and 2015, ocean temperatures increased faster, rising from 32°F (0.0°C) to 32.45°F (0.3°C).

In the Northeast, temperatures rose faster, rising from 32.7°F (0.4°C) to 34.2°F (1.2°C) between 1990 and 2020.

“The observed increase in melting coincides with a clear rise in potential ocean warming, indicating a strong oceanic control on ice shelf changes,” the authors added.

Recent studies suggest that a worst-case scenario, in which global temperatures continue to rise at the current pace, could result in ocean levels rising an additional 4.6 feet by 2150.

If global emissions were reduced only weakly, temperatures could triple, according to scientists from Busan National University in South Korea and Fabian Schlosser of the University of Hawaii.

Even limiting global warming to no more than 2°C above pre-industrial levels – the main goal of the Paris Agreement – ​​will not be enough to slow the rate of rise in sea levels.

The new study warns that only by limiting global temperature rise to less than 3.2 degrees Fahrenheit (1.8 degrees Celsius) compared to pre-industrial levels by the end of this century can accelerating sea level rise be avoided.

If sea levels continue to rise at current rates, large parts of the UK could be at risk of flooding.

Sea levels could rise by up to 4 feet by 2300

Scientists have warned that global sea levels could rise by up to 1.2 meters (4 feet) by 2300 even if we meet the 2015 Paris climate goals.

Long-term change will be driven by melting ice from Greenland to Antarctica, which is set to redraw global coastlines.

Sea level rise threatens cities from Shanghai to London, to low-lying areas of Florida or Bangladesh, and to entire countries such as the Maldives.

It is essential that we reduce emissions as quickly as possible to avoid a further rise, a German-led team of researchers said in a new report.

By 2300, the report forecasts sea levels will rise by 0.7 to 1.2 metres, even if nearly 200 countries meet targets set in the 2015 Paris Agreement.

The goals set by the agreements include reducing greenhouse gas emissions to net zero in the second half of this century.

She added that ocean levels will inevitably rise because heat-trapping industrial gases already emitted will remain in the atmosphere, causing more ice to melt.

In addition, water naturally expands when its temperature rises above four degrees Celsius (39.2 degrees Fahrenheit).

Every five years of delay after 2020 in reaching peak global emissions would mean an additional 8 inches (20 cm) of sea level rise by 2300.

“Sea level is often talked about as a really slow process and you can’t do much about it… but the next 30 years are really important,” said Dr. Matthias Mengele, lead author of the study, from the Potsdam Institute for Climate Impact Research in Potsdam. Germany.

None of the 200 governments that signed the Paris Agreement are on track to fulfill their pledges.

(Tags for translation) Daily Mail

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