Antarctic sea ice experiences record low extent for the second time in 5 years

Sea ice in the polar regions may be disappearing, but sea ice in the South is not. The extent of sea ice at the southern hemisphere experienced a record low in February. Researchers have identified the causes, but there are still many unanswered questions.

Their study was published in the journal Advances in Atmospheric Sciences.

The extent of sea ice in the northern part of the planet is rapidly declining as a result of global warming, but at the southern part of the planet, sea ice has been increasing over the last decade.

The southern hemisphere experienced a record minimum extent of sea ice in 2017, but there was something of a brief but quite marked aberration in the face of this overall increasing trend.

It happened again just five years later.

The first time the sea ice extent in the southern hemisphere has been under 2 million square kilometers was in 1978. The data showed that the ice cover in the Bellingshausen/Amundsen Seas was lower than normal. The sea ice extent was 30 percent lower than the average over the three-decade baseline period.

There is no scientific consensus on the causes of the variability of the sea ice in the South Pole, with a great deal yet to be explored. A group of researchers from Sun Yat-sen University and Southern Marine Science and Engineering Guangdong Laboratory in China set out to find out why a fresh sea-ice extent minimum occurred in such a short period of time.

The team used data from the National Snow and Ice Data Center to develop a sea-ice budget analysis. A sea-ice budget analysis involves a consideration of the number of inputs versus outputs of the sea-ice system, in other words, the sea ice that was added and the sea ice that was lost. The sea-ice budget analysis was used to connect the melting seasons to atmospheric circulation.

In the summertime, the processes that cause the sea ice to melt are dominated by the thermodynamics. There are anomalies in the transport of heat toward the pole in the Bellingshausen/Amundsen Seas, the western Pacific Ocean, and the eastern Weddell Sea.

A positive feedback of albedo and temperature has led to an increase in overall IR radiation and visible light. Albedo describes the whiteness of a surface. The greater the reflection of the radiation, the greater the absorption.

According to a study, sea ice is whiter than the dark unfrozen sea, thus there is less reflection of heat and more absorption.

The status of sea ice extent is influenced by both dynamics and thermodynamics in the spring. The dynamics of ice loss in the Amundsen Sea see northward ice motion that pushes more ice to the lower latitudes towards the tropics. Thinner sea ice freeboard along the coast of the Amundsen Sea plays a critical role with respect to the spring and summer melting.

According to the researchers, the new record for the sea-ice extent minimum occurred at the same time as a combination of La Ni and a positive Southern Annular Mode. The SAM describes a belt of strong westerly winds or low pressure that surrounds the continent, moving north or south, while La Ni is a weather pattern of powerful winds that blow warm ocean surface water strong from South America to Indonesia in the tropics.

The Amundsen Sea low is a center of low atmospheric pressure over the far south of the Pacific Ocean and off the coast of West Antarctica. The variability of atmospheric conditions in the region is greater than anywhere else.

The Amundsen Sea low has been found to be the cause of all the atmospheric impacts on the sea-ice extent anomalies.

The researchers were able to answer some questions.

The location that needs to be studied next is if tropical variability is having an impact.

More information: An Unprecedented Record Low Antarctic Sea-ice Extent during Austral Summer 2022, Advances in Atmospheric Sciences (2022). DOI: 10.1007/s00376-022-2087-1 Journal information: Advances in Atmospheric Sciences Citation: Antarctic sea ice experiences record low extent for the second time in 5 years (2022, April 19) retrieved 19 April 2022 from https://phys.org/news/2022-04-antarctic-sea-ice-extent-years.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.