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: Microscopic organism plays a big role in ocean carbon cycling

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

How productive are the ore factories in the deep sea?

18 hours ago

About ten years after the first moon landing, scientists on earth made a discovery that proved that our home planet still holds a lot of surprises in store for us. Looking through the portholes of the submersible ...

NASA image: Volcanoes in Guatemala

23 hours ago

This photo of volcanoes in Guatemala was taken from NASA's C-20A aircraft during a four-week Earth science radar imaging mission deployment over Central and South America. The conical volcano in the center ...

User comments : 0

More news stories

Study links California drought to global warming

While researchers have sometimes connected weather extremes to man-made global warming, usually it is not done in real time. Now a study is asserting a link between climate change and both the intensifying California drought ...

Google+ boss leaving the company

The executive credited with bringing the Google+ social network to life is leaving the Internet colossus after playing a key role there for nearly eight years.