Ocean circulation explains why the Arctic affected by global warming more than the Antarctic

Aug 25, 2014 by Genevieve Wanucha
By 2050, sea ice may vanish during Arctic summers. Credit: National Oceanic and Atmospheric Administration

Over recent decades, scientists have watched a climate conundrum develop at the opposite ends of Earth: The Arctic has warmed and steadily lost sea ice, whereas Antarctica has cooled in many places and may even be gaining sea ice. Now, MIT researchers have a better understanding of the elemental processes behind this asymmetric response of the polar regions to the effects of human-induced changes to the climate.

In a paper published in Philosophical Transactions of the Royal Society, John Marshall, the Cecil and Ida Green Professor of Oceanography at MIT, and his group investigated this phenomenon by considering ocean dynamics. The ocean, because of its ability to absorb and transport enormous amounts of heat, plays a critical role in climate change. The authors argue that ocean circulation can explain why the Arctic has warmed faster than the Antarctic.

In MIT computer simulations of the ocean and climate, excess heat from is absorbed into the Southern Ocean around Antarctica and in the North Atlantic Ocean, but it doesn't linger. Instead, the moving ocean redistributes the heat. In the Southern Ocean, strong, northward-flowing currents pull the heat towards the equator, away from the Antarctica. In the North Atlantic Ocean, a separate northward-flowing current system shunts the heat into the Arctic. So while Antarctica warms only mildly, the Arctic Ocean's temperature increases quickly, accelerating sea-ice loss and warming the Arctic atmosphere.

The model results reveal the differing responses to greenhouse gases in each region, with the Arctic warming more than twice as rapidly as the Antarctic. They also add confidence to the existing predictions of enormous future changes up north. By mid-century, the Arctic may warm so much that the oceans could go sea-ice free in the summers.

Marshall's group also showed that the ocean's response to the ozone hole can help explain the lack of warming to date around Antarctica. The millions of square feet of deterioration in the ozone over Antarctica was caused by emissions of the man-made pollutants chlorine and bromine, chlorofluorocarbons, which peaked at the turn of the century and are now slowly dwindling.

When they introduced an ozone hole into their model, the winds over the Southern Ocean grew faster and shifted southward, consistent with the observed wind changes around Antarctica. They found that this intensification of winds initially cools the sea surface and expands sea ice, but then a slow process of warming and sea ice shrinkage takes over. This warming happens, they suggest, because the stronger winds eventually dredge up to the surface relatively warm waters from the deep ocean. "Around Antarctica, the ozone hole may have delayed warming due to greenhouse gases by several decades," Marshall says. "I'm tempted to speculate that this is the period through which we are now passing. However, by 2050, ozone hole-effects may instead add to the warming around Antarctica, an effect that will diminish as the ozone hole heals."

"The researchers present a useful and timely reminder that the ocean is not a passive bath tub when it comes to climate change, but play an active role in shaping the spatial structure of climate change," says Richard Seagar, the Palisades Geophysical Institute/Lamont Research Professor at the Lamont-Doherty Earth Observatory, who was not involved in the study. "The work will likely motivate a lot of future work to better determine how the spatial patterns and temporal evolution of past and future climate change are influenced by an active ocean and its coupling back to the atmosphere."

The framework offers a new -centric picture of the effect of greenhouse gases and the ozone hole on polar climates. The slight cooling measured around Antarctica today might be a consequence of the temporary cooling influence of the . But as the century proceeds, both of the human-induced effects on the climate may combine to warm the waters around Antarctica. This MIT model joins several other recent demonstrations of the concerning, but uncertain, future effects of on Antarctic and glaciers and, in turn, ecosystems and sea-level rise.

Explore further: How wind helps Antarctic sea ice grow, even as the Arctic melts

More information: "The ocean's role in polar climate change: asymmetric Arctic and Antarctic responses to greenhouse gas and ozone forcing." John Marshall, et al. Phil. Trans. R. Soc. A 13 July 2014 vol. 372 no. 2019 20130040 DOI: 10.1098/rsta.2013.0040

add to favorites email to friend print save as pdf

Related Stories

Ocean winds keep Antarctica cold, Australia dry

May 11, 2014

New Australian National University-led research has explained why Antarctica is not warming as much as other continents, and why southern Australia is recording more droughts.

Large sea ice changes North of Swalbard

Jun 12, 2014

During the last decades warmer Atlantic water has caused a retreat of the ice edge north of Svalbard. In contrast to other areas of the Arctic Ocean, the largest ice loss north of Svalbard occurred during ...

Recommended for you

Kiribati leader visits Arctic on climate mission

Sep 20, 2014

Fearing that his Pacific island nation could be swallowed by a rising ocean, the president of Kiribati says a visit to the melting Arctic has helped him appreciate the scale of the threat.

NASA catches a weaker Edouard, headed toward Azores

Sep 19, 2014

NASA's Aqua satellite passed over the Atlantic Ocean and captured a picture of Tropical Storm Edouard as it continues to weaken. The National Hurricane Center expects Edouard to affect the western Azores ...

User comments : 6

Adjust slider to filter visible comments by rank

Display comments: newest first

TegiriNenashi
1.4 / 5 (9) Aug 25, 2014
Excellent: now global warming zealots can add check mark to the growing list of explained phenomena. Antarctic ice cover expanding? Simple: the current moves heat north (to the equator). Pine Island Glacier is melting? Simple: the current moves heat south (to the Antarctic Amundsen coast)!
thermodynamics
3.4 / 5 (5) Aug 25, 2014
Good article. Now Alche/WaterDud can explain to us how his "perfect" model (using a bowl of water, ice cubes, and a candle) "perfectly" explains this phenomena.

He says it models everything, so it must model this.
pandora4real
4.2 / 5 (5) Aug 25, 2014
And if you're wondering why only trolls have commented previously on this, it's because it has become common courtesy to kill the goddamned trolls. If you can't cut off their virtual nuts and let people with a modicum of intelligence comment, guess who you'll be left with?

SCI-ENCE people! Falsify-ability. These people are not like you. They cannot state the null hypothesis under which they will reject their hypothesis. That's called faith. Would you let Amish publish stupid comments on EVERY article about combustion engines? Wake up, do your job, and adopt YOUR OWN blog policy on these comments. Environmental terrorists are not given shrift.
howhot2
4 / 5 (4) Aug 25, 2014
"The esearchers present a useful and timely reminder that the ocean is not a passive bath tub when it comes to climate change, but play an active role in shaping the spatial structure of climate change," says Richard Seagar, Water_pressure will explode on that quote.

Here is an interesting one from the article Thermo; "Around Antarctica, the ozone hole may have delayed warming due to greenhouse gases by several decades," Marshall says. "I'm tempted to speculate that this is the period through which we are now passing. However, by 2050, ozone hole-effects may instead add to the warming around Antarctica, an effect that will diminish as the ozone hole heals."

I never thought of the ozone hole having an effect on greenhouse warming. Apparently it's there.
runrig
3.7 / 5 (3) Aug 26, 2014
I never thought of the ozone hole having an effect on greenhouse warming. Apparently it's there.

How .... I have considered it a factor (O3 is after all a GHG) - it is in the Strat, I know, but considering that the ave height of Antarctica is 12,000ft and allowing for the fact that the Tropopause is very low there - Stratospheric O3 (lack of) must have an influence on the Trop below. Just how that can be quantified I don't know. Is it factored into GCM's even?
antigoracle
2.3 / 5 (3) Aug 26, 2014
And if you're wondering why only trolls have commented previously on this, it's because it has become common courtesy to kill the goddamned trolls. If you can't cut off their virtual nuts and let people with a modicum of intelligence comment, guess who you'll be left with?
--pandoraTurd
Another gem from the AGW Cult's peanut gallery. This is what they consider "intelligence".