Climate tug of war disrupting Australian atmospheric circulation patterns

Jun 21, 2013
Strong El Niño events over the recent decades pull the westerly jets toward the equator and rising global temperatures push the westerly jets toward the pole.

(Phys.org) —The study, in the Nature journal Scientific Reports, demonstrates that mid-latitude high pressure zones (30 S-45 S) are being pushed further into the Southern Ocean by rising global temperatures associated with greenhouse warming. This is despite more frequent occurrences of strong El Niños in recent decades, which should have drawn the high pressure zones in the opposite direction toward the equator.

"What we are seeing," says study lead author, Mr Guojian Wang "is a 'tug of war' between stronger El Niños driving the winds north and the -warming effect driving the winds south".

Mr Wang, said the result confirms the robustness of the Southern Hemisphere circulation changes over the past three to four decades as the global temperature rose, "so much so that it overode the influence from strong El Niños during this period."

Study co-author, Dr Wenju Cai said the most conspicuous change is a rising sea level pressure in the mid-latitude bands and a decreasing sea level pressure over the Southern (55-70 S), a pattern referred to as the Southern Annular Mode. The changing pressures indicate a poleward or southward expansion of the tropical and subtropical atmospheric zones.

In turn, this indicates that over the long-term, there is a relationship between a rising global mean temperature and an upward trend of the Southern Annular Mode.

"The research reinforces our past work that climate change is altering circulation and increases our confidence in this conclusion," Dr Cai said.

Dr Cai has previously reported on changes in that have been shifting and strengthening the Pacific Ocean winds poleward and in turn strengthening the , pushing the East Australian Current further south down the Australian coast.

He said during El Niño, the warmer ocean releases heat to the atmosphere and global increase. At the same time, warm ocean surface temperatures along the equator cause the tropical and subtropical atmospheric belts to move toward the equator, generating a 'negative' phase of the Southern Annular Mode.

"On year-to-year time scales, higher are associated with a negative phase of the Mode but over the past 35 years, when El Niño has been strong and conducive to a negative trend, we are seeing an opposite trend with the circulation systems moving southward impacting on regional climate," he said.

Explore further: Tropical air circulation drives fall warming on Antarctic Peninsula

add to favorites email to friend print save as pdf

Related Stories

Human-generated aerosols affect our weather

Jan 22, 2008

The rise of human-generated pollution in the global atmosphere is forcing a change in ocean circulation in the Southern Hemisphere, in turn affecting our region’s weather systems.

Understanding autumn rain decline in SE Australia

May 23, 2008

According to a report from a CSIRO Wealth From Oceans Flagship study – published this week in the science journal Geophysical Research Letters – since 1950 Victoria has suffered a 40 per cent decline in aut ...

Changing El Nino could reshape Pacific Ocean biology

Jun 15, 2012

Over the past few decades, the scientific understanding of El Nino has grown increasingly complex. Traditionally viewed as a periodic warming focused largely in the eastern equatorial Pacific Ocean, El Nino is associated ...

Study finds Southern Hemisphere becoming drier

Oct 03, 2012

A decline in April-May rainfall over south-east Australia is associated with a southward expansion of the subtropical dry-zone according to research published today in Scientific Reports, a primary research journal from t ...

Recommended for you

Agriculture's growing effects on rain

20 hours ago

(Phys.org) —Increased agricultural activity is a rain taker, not a rain maker, according to researchers at Pacific Northwest National Laboratory and their collaborators at the University of California Los ...

Asian air pollution affect Pacific Ocean storms

Apr 14, 2014

In the first study of its kind, scientists have compared air pollution rates from 1850 to 2000 and found that anthropogenic (man-made) particles from Asia impact the Pacific storm track that can influence ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

Sherrin
5 / 5 (6) Jun 25, 2013
Very interesting. This winter, we've barely seen a single cold front through Canberra (harbinger of the westerly winds). In years gone by, the first significant cold fron burst through our area by mid-March. here are we almost July and barely a single (weak) cold front. Explains the lack of snowfall in the mountains too.
Howhot
5 / 5 (6) Jun 29, 2013
Just look at this map to see a prediction of 2060.

http://www.nasa.g...ass.html

The polar regions really get hit hard, as do the Aussi's.

More news stories

UN weather agency warns of 'El Nino' this year

The UN weather agency Tuesday warned there was a good chance of an "El Nino" climate phenomenon in the Pacific Ocean this year, bringing droughts and heavy rainfall to the rest of the world.

Low Vitamin D may not be a culprit in menopause symptoms

A new study from the Women's Health Initiative (WHI) shows no significant connection between vitamin D levels and menopause symptoms. The study was published online today in Menopause, the journal of The North American Menopa ...

Astronomers: 'Tilt-a-worlds' could harbor life

A fluctuating tilt in a planet's orbit does not preclude the possibility of life, according to new research by astronomers at the University of Washington, Utah's Weber State University and NASA. In fact, ...