Will North Atlantic threshold response to ocean changes be enough?

Feb 17, 2008

Predictions that the 21st century is safe from major circulation changes in the North Atlantic Ocean may not be as comforting as they seem, according to a Penn State researcher.

"The Intergovernmental Panel on Climate Change concluded that it is very unlikely that the North Atlantic meridional overturning circulation (MOC) will collapse in the 21st century. They predict a probability of less then 10 percent," says Klaus Keller, assistant professor of geosciences. "However, this should not be interpreted as an all clear signal. There can be a considerable delay between the triggering of an MOC collapse and the actual collapse. In a similar way, a person that has just jumped from a cliff may take comfort that pain in the next few seconds is very unlikely, but the outlook over the long term is less rosy."

Keller and his colleagues analyzed a possible threshold response for the MOC. A threshold response occurs when a system reacts in a highly nonlinear and potentially abrupt way. For example, a paddler can tip a canoe quite a bit without getting wet. However, pushing that canoe just a bit further can result in a wet paddler. The impacts of pushing the canoe to the side are negligible until the very last small push triggers the overturning of the canoe in a threshold response.

The MOC may also respond to human-made greenhouse gas emissions in a threshold response. The research projects sizeable impacts on patterns of surface air temperatures and precipitation, fisheries and terrestrial ecosystems if a slowdown or complete collapse of the MOC occurs.

"Currently, MOC projections are deeply uncertain. This uncertainty puts a large value on observation systems that could deliver an actionable early warning of an MOC collapse," Keller said today (Feb. 17) at the annual meeting of the American Association for the Advancement of Science in Boston. "The problem is that information that arrives after the threshold response has been triggered is only of very limited use. For example, warning a person in a canoe about an approaching waterfall can be useful before the waterfall, but is not really useful after the canoe went over the waterfall.

"The problem with the potential MOC collapse is that the signs of an approaching threshold response are very subtle to detect. The noise is large and picking out the signal from the noise is non trivial," he adds.

"There is tantalizing evidence for a recent MOC slow down. However, this is not an open-and-shut case," Keller continues.

The researchers analyzed how they could improve MOC observation systems to result in more skillful MOC projections. For example, optimizing the locations of the observation system can considerably improve the projections.

Improved MOC projections can enable improved climate policies and can have economic value. Keller and colleagues show that investments into an MOC observation system that would provide an early warning of an approaching MOC collapse would likely pass a cost benefit test.

Source: Penn State

Explore further: Not all phytoplankton in the ocean need to take their vitamins

add to favorites email to friend print save as pdf

Related Stories

Introducing the multi-tasking nanoparticle

51 minutes ago

Kit Lam and colleagues from UC Davis and other institutions have created dynamic nanoparticles (NPs) that could provide an arsenal of applications to diagnose and treat cancer. Built on an easy-to-make polymer, these particles ...

Eta Carinae: Our Neighboring Superstars

1 hour ago

(Phys.org) —The Eta Carinae star system does not lack for superlatives. Not only does it contain one of the biggest and brightest stars in our galaxy, weighing at least 90 times the mass of the Sun, it ...

Indonesia passes law to tap volcano power

1 hour ago

The Indonesian parliament on Tuesday passed a long-awaited law to bolster the geothermal energy industry and tap the power of the vast archipelago's scores of volcanoes.

Recommended for you

EU project sails off to study Arctic sea ice

4 hours ago

A one-of-a-kind scientific expedition is currently heading to the Arctic, aboard the South Korean icebreaker Araon. This joint initiative of the US and Korea will measure atmospheric, sea ice and ocean properties with technology ...

Snails tell of the rise and fall of the Tibetan plateau

5 hours ago

The rise of the Tibetan plateau—the largest topographic anomaly above sea level on Earth—is important for both its profound effect on climate and its reflection of continental dynamics. In this study published in GSA ...

New signs of eruption at Iceland volcano

21 hours ago

Teams monitoring Iceland's Bardarbunga volcano have found evidence of a possible underground eruption as powerful earthquakes continue to shake the area, Icelandic authorities said Thursday.

NASA sees a weaker Tropical Storm Marie

21 hours ago

When NOAA's GOES-West satellite captured an image of what is now Tropical Storm Marie, weakened from hurricane status on August 28, the strongest thunderstorms were located in the southern quadrant of the ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

EarthScientist
1 / 5 (1) Feb 18, 2008
If you Penn State folks understood the mechanism for the Atlantic and the role of the fish placed in the ocean,you might be able to have some predictability of the MOC ,as you boys call it.Grid Scientists are tasking now to clean up your assumptions and straighten out your science. We have not been tasking before,but have decided to task at this time.Your process will be enhanced when you apply our tasking information to your process. You'll See...