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Montevideo, February 25th 2024 - 09:54 UTC

 

 

Antarctic sea ice reaches all-time low, according to new scientific report

Tuesday, April 19th 2022 - 20:01 UTC
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There seems to be no scientific consensus as to the causes of this phenomena There seems to be no scientific consensus as to the causes of this phenomena

A new scientific report has shown that the icy mass in Antarctica has shrunk below 1.4 million square kilometers for the first time since measurements began being recorded in 1978.

Since the late 1970s, Antarctic sea ice had been experiencing a modest increase of about 1% per decade until measurements taken in February showed that sea ice levels were at an all-time low since the beginning of satellite observations of the poles in 1978.

On February 25, sea ice levels in the Bellingshausen Sea, Amundsen Sea and the Weddell Sea were reported to have reached historic lows of about 30% below the 1981-2010 average.

Several causes have been said to lie behind the new phenomenon, but there seems to be no scientific consensus.

Researchers from Sun Yat-sen University and the Southern Guangdong (Zhuhai) Marine Engineering and Science Laboratory in China have taken it upon themselves to discover what had happened and why, using data spanning the years 1979 to 2022 recorded by the National Snow and Ice Data Center (NSIDC).

Their findings showed that, in the summer, thermodynamics dominates the processes that cause sea ice to melt. A sea ice balance analysis involves a consideration of sea ice added and lost, along with the dynamics (including advection and divergence contributions) and thermodynamics (processes related to freezing and melting) that affect this.

The sea ice balance analysis was carried out to cover the melting seasons and then connect it to the atmospheric circulation during the same periods. According to the team, this occurs through anomalies in poleward heat transport in the Bellingshausen/Amundsen Seas, the western Pacific Ocean, and the eastern Weddell Sea in particular.

Infrared radiation and visible light also increase in summer, as a result of positive feedback from 'albedo' (the whiteness of the surface) and temperature. The whiter the surface, the greater the reflection of radiation, while the darker the surface, the greater the absorption.

“Sea ice is whiter than the dark unfrozen sea, so there is less heat reflection and more absorption, which in turn melts more sea ice, producing more heat absorption, in a vicious cycle,” explained Qinghua Yang, co-author of the study.

By spring, however, the dynamics of ice loss in the Amundsen Sea cause the ice to shift northward toward the tropics, increasing melting. Meanwhile, the new record low for sea ice was recorded at about the same time as a combination of La Niña and a positive Southern Annular Mode (SAM).

SAM is a belt of strong westerly winds or low pressure that encircles the continent, moving northward or southward, while La Niña is a weather pattern of powerful winds blowing warm ocean surface waters from South America to Indonesia in the tropics.

Together, both SAM and La Niña deepen the Amundsen Sea Low (ASL), a center of low atmospheric pressure over the southern Pacific Ocean and off the coast of West Antarctica. Unfortunately, several issues remained unanswered as to why these phenomena were causing unprecedented sea ice melt. “If tropical variability is having such an impact, it is that location that needs to be studied next,” added Jinfei Wang, one of the other authors of the document.

Juan Manuel Lirio a geologist at the Argentine Antarctic Institute explained to Infobae that the reduction of ice was notorious in Antarctica in recent decades. “I am 62 years old, and I have been going to Antarctica to do science for 30 years. I study lakes in the north of the Antarctic Peninsula, very close to the Argentine Antarctic bases, and we see there how the glaciers are retreating and more and more lakes are forming, in quantity and surface area,” he said.

“Since 1985, the number of lakes in Antarctica has doubled as a result of glacial retreat. The worrying thing is that Antarctica is the largest white surface mirror on Earth and serves to reject sunlight and prevent global warming. It is the main 'refrigerator' that the planet has. When the sea ice surrounding the continent melts, that white surface that rejected the heat now turns blue, which is the water that attracts it,” he added.

The study comes shortly after research revealed that global sea levels could rise by up to 3 meters if the Thwaites Glacier in West Antarctica collapses. Rising sea levels threaten cities from Shanghai to London, to low-lying swathes of Florida or Bangladesh, and entire nations such as the Maldives.

In the United Kingdom, for example, a rise of 6.7 feet (2 meters) or more could put areas such as Hull, Peterborough, Portsmouth, and parts of east London and the Thames Estuary at risk of being submerged. Glacier collapse, which could begin within decades, could also submerge major cities such as New York and Sydney. Parts of New Orleans, Houston, and Miami in the southern U.S. would also be particularly affected.

Antarctica contains a large amount of water. The three ice sheets that cover the continent contain about 70% of our planet's fresh water, and it's all due to warming air and oceans. If all the ice sheets were to melt due to global warming, Antarctica would raise global sea levels by at least 183 feet (56 m). Given their size, even small losses in the ice sheets could have global consequences.

In addition to sea-level rise, meltwater would slow global ocean circulation, while shifting wind belts could affect climate in the Southern Hemisphere. In February 2018, NASA revealed that El Niño events cause the Antarctic ice shelf to melt up to ten inches (25 centimeters) each year.

El Niño and La Niña are separate events that alter the water temperature of the Pacific Ocean, which periodically swings between warmer than average during El Niño and colder than average during La Niña. Using NASA satellite imagery, researchers discovered that the oceanic phenomena cause Antarctic ice shelves to melt and at the same time increase snowfall.

In March 2018, it was revealed that more of a giant glacier the size of France in Antarctica was floating in the ocean, raising fears that it could melt faster than expected as climate warms up with a dramatic impact on sea-level rise.

(Source: Infobae)

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