Circulation changes in a warmer ocean

Feb 22, 2013
Simulated changes in sea surface temperature (oC, contours) with comparison to reconstructed changes (circles) in the North Atlantic.

Circulation changes in a warmer ocean In a new study, scientists suggest that the pattern of ocean circulation was radically altered in the past when climates were warmer.

Ancient warm periods offer useful insights into potential future warming and its impacts.  The mid-Pliocene, ~3 million years ago, was a relatively recent period of global warmth that is often considered as an analog for our future.

During this , unusually warm surface conditions existed in the North Atlantic, which has often been simply explained by the intensification of the existing pattern of . However, reproducing these changes with has eluded researchers for more than a decade—suggesting either that there was something wrong with the long-standing explanation or with the models used to predict the behavior of warmer oceans.

An alternative pattern of warm ocean circulation

A team of Bergen scientists reevaluated the existing observations and used the Norwegian Earth System model (NorESM) to carry out simulations to better understand ocean circulation during the warm mid-Pliocene.

They illustrated that the largest changes occurred in the deep Southern Ocean, but not in the North Atlantic, indicating that the existing explanation was not adequate. They found that the data and simulations pointed toward an altogether different pattern of ocean circulation, with playing a stronger role due to faster renewal of the deeper in the Southern Ocean during the mid-Pliocene. This alternative explanation provided a solution to the long standing discrepancy between reconstructions of ocean circulation at the time and available .

North Atlantic warming

The team also addressed the unusual warmth in the North Atlantic during the warm mid-Pliocene.  The observed high latitude warmth was shown not to require the intensification of todays ocean circulation and the transport of ocean heat to the north, rather it was a direct response to changes in insolation and atmospheric carbon dioxide levels at the time. The study highlights just how differently ocean circulation was when the planet was warmer and carbon dioxide levels were high.

The study by Zhongshi Zhang, Kerim Nisancioglu and Ulysses Ninnemann from the Bjerknes Centre for Climate Research in Bergen was published on Tuesday February 19th in Nature Communications.

Explore further: Magnitude-7.2 earthquake shakes Mexican capital

More information: Zhang, Z.-S. et al. Increased ventilation of Antarctic deep water during the warm mid-Pliocene. Nat. Commun. 4:1499 doi: 10.1038/ncomms2521 (2013).

add to favorites email to friend print save as pdf

Related Stories

No evidence of polar warming during penultimate interglacial

Jul 18, 2012

The Atlantic Meridional Overturning Circulation (AMOC), driven by temperature and salinity gradients, is an important component of the climate system; it transfers an enormous amount of heat via ocean currents and atmospheric ...

Atlantic to Pacific feedback discovered

Feb 22, 2007

French scientists say an exchange of water vapor from the Atlantic to the Pacific might be an important feedback mechanism for abrupt climatic changes.

Recommended for you

Magnitude-7.2 earthquake shakes Mexican capital

Apr 18, 2014

A powerful magnitude-7.2 earthquake shook central and southern Mexico on Friday, sending panicked people into the streets. Some walls cracked and fell, but there were no reports of major damage or casualties.

User comments : 0

More news stories

China says massive area of its soil polluted

A huge area of China's soil covering more than twice the size of Spain is estimated to be polluted, the government said Thursday, announcing findings of a survey previously kept secret.

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.

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...