Melting Arctic sea ice: How much is down to us?

Jul 27, 2012

(Phys.org) -- Natural climate variations could explain up to 30% of the loss in Arctic sea ice since the 1970s, scientists have found.

at the North Pole has shrunk dramatically over the past 40 years. The ice is now more than a third smaller each September following the summer melt than it was in the 1970s. This affects wildlife, while potentially opening up new northern sea routes and controversial opportunities for .

Scientists at the University of Reading and the Japan Agency for Marine Earth Science and Technology (JAMSTEC) have found that some of the reduction in ice since 1979 - between 5% and 30% - may be linked to the Atlantic Multi-decadal Oscillation (AMO), a cycle of warming and cooling in the North Atlantic, which repeats every 65-80 years and has been in a warming phase since the mid 1970s.

Dr. Jonny Day, University of Reading, said: "The debate over how much the change observed in can be attributed to humans and how much is due to natural variability in the climate is an important one. Our study shows that while natural changes play a significant role, the majority of sea ice loss - between 70% and 95% - is likely to be due to man-made .

"Work like ours helps to explain how humans and natural variations are affecting sea ice and helps to develop more accurate predictions."

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By using advanced statistical techniques to compare obtained since 1979 with run on some of the world's most powerful supercomputers, researchers were able to provide a better estimate of the importance of natural climate variability on the reduction in sea ice, and how much could be attributed to human activity.

They found the in winds over the Arctic (the , or AO), which can cause ice to thin in some areas and pile up in others, had surprisingly little influence on the loss of sea ice. However the Atlantic Ocean's AMO oscillation did have an impact.

The research, published online today in Environmental Research Letters, also looks back to 1953 when fewer observations are available. The natural warming/cooling cycles of the Atlantic Multi-decadal Oscillation (AMO) appear to have a much smaller influence on sea ice loss since 1953.

The scientists suggest that their work will help to provide more accurate predictions of changes in sea ice extent, allowing those working in science, policy, industry and those living throughout the polar region to have a better understanding of what the Arctic will look like in the future.

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More information: J J Day, J C Hargreaves, J D Annan and A Abe-Ouchi 2012 Sources of multi-decadal variability in Arctic sea ice extent Environ. Res. Lett. 7 034011, doi:10.1088/1748-9326/7/3/034011

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User comments : 9

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Lurker2358
4.4 / 5 (5) Jul 27, 2012
Our study shows that while natural changes play a significant role, the majority of sea ice loss - between 70% and 95% - is likely to be due to man-made greenhouse gas emissions.


Requires some qualification, since the forcing caused by second order albedo feedback caused by the melting of ice is 4 times greater than the forcing caused directly by the CO2 itself.

This can be verified by observing the winter sea ice anomalies and comparing that to the summer sea ice anomalies. The summer anomalies are several times larger than the winter anomalies, indicating that second order albedo Feedback is playing a larger role than the greenhouse effect itself.
rubberman
5 / 5 (4) Jul 27, 2012
Agreed, the article makes no mention of feedbacks associated with diminished ice cover and what roll they played in the study.
nappy
2.5 / 5 (11) Jul 27, 2012
I would say that the melt is 100% due to natural causes. CO2 is not magic and does not prevent convection. At the extremely low concentration of 358 ppm, it has no effect on warming and, it is a trailing indicator of warming. Warm water releases CO2. Humans are a bit too puny to take credit for this.
thermodynamics
4.4 / 5 (7) Jul 27, 2012
I would say that the melt is 100% due to natural causes. CO2 is not magic and does not prevent convection. At the extremely low concentration of 358 ppm, it has no effect on warming and, it is a trailing indicator of warming. Warm water releases CO2. Humans are a bit too puny to take credit for this.


Would you please give us some technical references that back up your claim that CO2 increase does not cause heat retention by the Earth? I will give you two text books as references on thermal radiation that show that CO2 does work to retain heat, even in the ppm range:

"Siegel and Howell: Thermal Radiation Heat Transfer"
"Modest: Radiative Heat Transfer"

Please look through the chapters on CO2 and H2O interactions and then please let me know where they are wrong. Thank you for your well "informed comments" and I will be waiting for your technical analysis (full sarcasm intended). I am sure your magic will help this Muggle to understand better.

Vendicar_Decarian
3.5 / 5 (11) Jul 27, 2012
To Conservatives, opinion = reality. They do not live a reality based existence.

"I would say that the melt is 100% due to natural causes." - DirtyNappy
NotParker
1.8 / 5 (5) Jul 29, 2012
"black carbon soot" has changed the albedo. Nothing to do with CO2.

http://wattsupwit...-to-why/
thermodynamics
5 / 5 (2) Jul 29, 2012
NP you say: "black carbon soot" has changed the albedo. Nothing to do with CO2."

NP: Back to your old stance on CO2. Are you ready to give up now that the BEST analyses have come back showing CO2 as the primary indicator of global warming? You can see their latest at:

http://berkeleyearth.org/

To refresh your memory, this was funded initially by the Koch brothers because Muller was an advocate of the heat island effect as being the misleading temperature dataset showing GW. His site is here:

http://muller.lbl.gov/

He used to be quoted regularly by Watt, but he seems to have lost favor these days. I am sure that Watt will have something to say about why this new analysis is "wrong" even though he has nowhere near the credentials of those who derived them. (more to come since we have the character limit)
thermodynamics
4.3 / 5 (3) Jul 29, 2012
NP:

One more issue for you. If soot is the cause of the melting of the arctic, then it would be reasonable to look back at the historical information on soot. It was much more prevalent in the northern hemisphere air in the late 1800s and early 1900s. The cause was the industrial use of coal with zero pollution control. If you look at soot in the record of arctic ice you will see the carbon particles around the beginning of the 1900s. If that is the root cause of melting, please explain to me how it is so influential now that polution control, of some sort, is being implemented around the world (including the new Chinese power plants).

One other little issue. You have mentioned in ealier posts that you did not think that humans (not even 7 billion of them) could influence climate. You are now saying we are influencing climate with soot. Please make up your mind. You confuse poor little me when you say we can't change climate and then explain how we are. (yes,sarcasm)
NotParker
2.3 / 5 (3) Jul 30, 2012
The BEST papers have been rejected from peer reviewed journals.

http://wattsupwit...-review/

But I did look at the BEST USA data.

"the most recent 5 year period TMAX in the USA is .5C colder than the previous 5 year period and colder than the 10 period starting around 1933 and extending into the early 1940s. And also colder than the mid 1950s and around 1990.

Even more interesting, the most current 5 year period is only .57C warmer than the earliest 5 year period in the 1840s."

http://sunshineho...rly-40s/

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