El Nino, La Nina rearrange South Pole sea ice

September 19, 2001

Scientists have been mystified by observations that when sea ice on one side of the South Pole recedes, it advances farther out on the other side. New findings from NASA's Office of Polar Programs suggest for the first time that this is the result of El Niños and La Niñas driving changes in the subtropical jet stream, which then alter the path of storms that move sea ice around the South Pole.

The results have important implications for understanding global climate change better because sea ice contributes to the Earth's energy balance. The presence of sea ice, which is generated around each pole when the water gets cold enough to freeze, reflects solar energy back out to space, cooling the planet. When there is less sea ice, the ocean absorbs the sun's heat and that amplifies climate warming.

By looking at the relationship between temperature changes in the ocean, atmospheric winds, storms, and sea ice, the new study pinpoints causes for retreating and advancing ice in the Atlantic and Pacific ocean basins on either side of the South Pole, called the "Antarctic dipole."

"El Niños and La Niñas appear to be the originating agents for helping generate the sea ice dipole observed in the ocean basins around the Antarctic," said David Rind, lead author of the study and a senior climate researcher at the NASA Goddard Institute for Space Studies. The study appears in the September 17 issue of Journal of Geophysical Research.

During El Niño years, when the waters of the Eastern Pacific heat up, warm air rises. As the air rises it starts to move toward the South Pole, but the earth's rotation turns the winds eastward. The Earth's rotation is just strong enough to cause this rising air to strengthen the subtropical jet stream, a band of atmospheric wind near the equator that also blows eastward.

When the subtropical jet stream gets stronger over the Pacific basin, it diverts storms away from the Pacific side of the South Pole. Since there are fewer storms near the Pacific-Antarctic region during El Niño years, there are less winds to blow sea ice farther out into the ocean, and ice stays close to shore.

At the same time, the air in the tropical Atlantic basin sinks instead of rising. That sinking air weakens the subtropical jet stream over the Atlantic, guiding storms towards the South Pole. The storms, which intensify as they meet the cooler Antarctic air, then blow sea ice away from the pole farther into the Atlantic.

During La Niña years, when the Eastern and central Pacific waters cool, there is an opposite effect, where sea ice subsides on the Atlantic side, and advances on the Pacific side.

The study is important because the amount of sea ice that extends out into the ocean plays a key role in amplifying or decreasing the warming effects of the sun on our climate. Also, the study explains causes of the Antarctic sea ice dipole for the first time, and provides researchers with a greater understanding of the effects of El Niño and La Niña on sea ice.

Scientists may use these findings in global climate models to gauge past, present and future climate changes.

"Understanding how changes in the temperature in the different ocean basins will affect sea ice is an important part of the puzzle in understanding climate sensitivity," Rind said.
-end-
For more information see:

http://www.gsfc.nasa.gov/topstory/20010917seaice.html

NASA/Goddard Space Flight Center

Related Sea Ice Articles from Brightsurf:

2020 Arctic sea ice minimum at second lowest on record
NASA and the National Snow and Ice Data Center (NSIDC) at the University of Colorado Boulder shows that the 2020 minimum extent, which was likely reached on Sept.

Sea ice triggered the Little Ice Age, finds a new study
A new study finds a trigger for the Little Ice Age that cooled Europe from the 1300s through mid-1800s, and supports surprising model results suggesting that under the right conditions sudden climate changes can occur spontaneously, without external forcing.

How much will polar ice sheets add to sea level rise?
Over 99% of terrestrial ice is bound up in the ice sheets covering Antarctic and Greenland.

A snapshot of melting Arctic sea ice during the summer of 2018
A study appearing July 29 in the journal Heliyon details the changes that occurred in the Arctic in September of 2018, a year when nearly 10 million kilometers of sea ice were lost throughout the summer.

Antarctic penguins happier with less sea ice
Researchers have been surprised to find that Adélie penguins in Antarctica prefer reduced sea-ice conditions, not just a little bit, but a lot.

Seasonal sea ice changes hold clues to controlling CO2 levels, ancient ice shows
New research has shed light on the role sea ice plays in managing atmospheric carbon dioxide levels.

Artificial intelligence could revolutionize sea ice warnings
Today, large resources are used to provide vessels in the polar seas with warnings about the spread of sea ice.

Antarctic sea ice loss explained in new study
Scientists have discovered that the summer sea ice in the Weddell Sea sector of Antarctica has decreased by one million square kilometres -- an area twice the size of Spain -- in the last five years, with implications for the marine ecosystem.

Antarctic sea-ice models improve for the next IPCC report
All the new coupled climate models project that the area of sea ice around Antarctica will decline by 2100, but the amount of loss varies considerably between the emissions scenarios.

Earth's glacial cycles enhanced by Antarctic sea-ice
A 784,000 year climate simulation suggests that Southern Ocean sea ice significantly reduces deep ocean ventilation to the atmosphere during glacial periods by reducing both atmospheric exposure of surface waters and vertical mixing of deep ocean waters; in a global carbon cycle model, these effects led to a 40 ppm reduction in atmospheric CO2 during glacial periods relative to pre-industrial level, suggesting how sea ice can drive carbon sequestration early within a glacial cycle.

Read More: Sea Ice News and Sea Ice Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.