Home North pole ice Record Antarctic sea ice extent may signal change

Record Antarctic sea ice extent may signal change

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Pristine snow and ice reflect more than 80% of the sun’s energy back into space.

Sea ice around Antarctica shrank to the smallest extent on record in February, five years after the previous record high, researchers said on Tuesday, suggesting Earth’s frozen continent may be less impervious to climate change than foreseen.

In late February, the ice-covered ocean area slipped below the symbolic barrier of two million square kilometers (about 772,000 square miles) for the first time since satellite records began in 1978, according to a study published in the journal Advances in atmospheric science.

The researchers found that the primary driver of ice loss was temperature change, although changes in ice mass also played a lesser role.

The North and South Pole regions have warmed about three degrees Celsius from late 19th century levels, three times the global average.

Antarctica encountered its first recorded heat wave of 2020, with an unprecedented temperature of 9.2°C above the mean maximum, and in March a research facility in East Antarctica saw temperatures soar 30 degrees above normal.

But extreme aberrations of this kind are recent.

Unlike sea ice in the Arctic, which has been shrinking by 3% per year since the late 1970s, sea ice in Antarctica has been expanding over the same period by 1% per decade, although ‘with large annual variations.

Ice cover during this year’s southern summer has shrunk the most around West Antarctica, which has been more vulnerable to global warming than the much larger East Antarctica.

Sea ice budget

Melting sea ice has no discernible impact on sea level because the ice is already in the ocean water.

But the decrease in ice cover is nevertheless a major concern because it contributes to accelerating global warming, explained co-author Qinghua Yang, a professor at Sun Yat-sen University in Guangzhou.

When white sea ice – which reflects energy from the Sun back into space – is replaced by dark, unfrozen sea, “there is less heat reflection and more absorption”, he said. said in a statement.

“It melts more sea ice, producing more heat absorption, in a vicious circle.”

Pristine snow and ice reflect over 80% of the sun’s energy back into space, while the open ocean absorbs the same percentage.

Surprisingly, the record low of 1.9 million square kilometers on February 25 was 30% below the 1981-2010 average. The previous record was just over two million square kilometers in 2017.

The maximum extent of Antarctic sea ice has averaged about 18 million square kilometers in recent years.

To analyze the causes of this year’s record ice loss, researchers looked at Antarctica’s “sea ice budget” – ice added and ice lost, year by year – as well as drift or movement sea ​​ice daily.

“In summer, thermodynamic” – or temperature-related – processes “dominate sea melt through poleward heat transport,” the study concludes.

The record minimum Arctic sea ice extent – 3.4 million square kilometers – was recorded in 2012, with the 2nd and 3rd lowest ice covered areas in 2020 and 2019, respectively. The maximum extent of the sea ice averages about 15 million square kilometres.

The ice caps atop West Antarctica hold the equivalent of six meters of sea level rise, while the massive glaciers of East Antarctica are said to lift the world’s oceans by more than 50 metres.


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© 2022 AFP

Quote: Record Antarctic Sea Ice Extent May Signal Shift (April 19, 2022) Retrieved April 19, 2022 from https://phys.org/news/2022-04-antarctic-sea-ice-extent-shift.html

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