UPDATE: Perhaps in response to criticism here, MIT has changed the press release wording. See below.
From MIT, now if they could work the wind patterns in, as NASA suggests, we might have a clearer picture of why the Arctic summer sea ice extent has changed.
Ocean currents play a role in predicting extent of Arctic sea ice
CAMBRIDGE, Mass. — Each winter, wide swaths of the Arctic Ocean freeze to form sheets of sea ice that spread over millions of square miles. This ice acts as a massive sun visor for the Earth, reflecting solar radiation and shielding the planet from excessive warming.
The Arctic ice cover reaches its peak each year in mid-March, before shrinking with warmer spring temperatures. But over the last three decades, this winter ice cap has shrunk: Its annual maximum reached record lows, according to satellite observations, in 2007 and again in 2011.
Understanding the processes that drive sea-ice formation and advancement can help scientists predict the future extent of Arctic ice coverage — an essential factor in detecting climate fluctuations and change. But existing models vary in their predictions for how sea ice will evolve.
Now researchers at MIT have developed a new method for optimally combining models and observations to accurately simulate the seasonal extent of Arctic sea ice and the ocean circulation beneath. The team applied its synthesis method to produce a simulation of the Labrador Sea, off the southern coast of Greenland, that matched actual satellite and ship-based observations in the area.
Through their model, the researchers identified an interaction between sea ice and ocean currents that is important for determining what’s called “sea ice extent” — where, in winter, winds and ocean currents push newly formed ice into warmer waters, growing the ice sheet. Furthermore, springtime ice melt may form a “bath” of fresh seawater more conducive for ice to survive the following winter.
Accounting for this feedback phenomenon is an important piece in the puzzle to precisely predict sea-ice extent, says Patrick Heimbach, a principal research scientist in MIT’s Department of Earth, Atmospheric and Planetary Sciences.
“Until a few years ago, people thought we might have a seasonal ice-free Arctic by 2050,” Heimbach says. “But recent observations of sustained ice loss make scientists wonder whether this ice-free Arctic might occur much sooner than any models predict … and people want to understand what physical processes are implicated in sea-ice growth and decline.”
Heimbach and former MIT graduate student Ian Fenty, now a postdoc at NASA’s Jet Propulsion Laboratory, have published the results from their study in the Journal of Physical Oceanography.
An icy forecast
As Arctic temperatures drop each winter, seawater turns to ice — starting as thin, snowflake-like crystals on the ocean surface that gradually accumulate to form larger, pancake-shaped sheets. These ice sheets eventually collide and fuse to create massive ice floes that can span hundreds of miles.
When seawater freezes, it leaches salt, which mixes with deeper waters to create a dense, briny ocean layer. The overlying ice is fresh and light in comparison, with very little salt in its composition. As ice melts in the spring, it creates a freshwater layer on the ocean surface, setting up ideal conditions for sea ice to form the following winter.
Heimbach and Fenty constructed a model to simulate ice cover, thickness and transport in response to atmospheric and ocean circulation. In a novel approach, they developed a method known in computational science and engineering as “optimal state and parameter estimation” to plug in a variety of observations to improve the simulations.
A tight fit
The researchers tested their approach on data originally taken in 1996 and 1997 in the Labrador Sea, an arm of the North Atlantic Ocean that lies between Greenland and Canada. They included satellite observations of ice cover, as well as local readings of wind speed, water and air temperature, and water salinity. The approach produced a tight fit between simulated and observed sea-ice and ocean conditions in the Labrador Sea — a large improvement over existing models.
The optimal synthesis of model and observations revealed not just where ice forms, but also how ocean currents transport ice floes within and between seasons. From its simulations, the team found that, as new ice forms in northern regions of the Arctic, ocean currents push this ice to the south in a process called advection. The ice migrates further south, into unfrozen waters, where it melts, creating a fresh layer of ocean water that eventually insulates more incoming ice from warmer subsurface waters of subtropical Atlantic origin.
Knowing that this model fits with observations suggests to Heimbach that researchers may use the method of model-data synthesis to predict sea-ice growth and transport in the future — a valuable tool for climate scientists, as well as oil and shipping industries.
“The Northwest Passage has for centuries been considered a shortcut shipping route between Asia and North America — if it was navigable,” Heimbach says. “But it’s very difficult to predict. You can just change the wind pattern a bit and push ice, and suddenly it’s closed. So it’s a tricky business, and needs to be better understood.”
Martin Losch, a research scientist at the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany, says the feedback mechanism identified by the MIT group is important for predicting sea-ice extent on a regional scale.
“The dynamics of climate are complicated and nonlinear, and are due to many different feedback processes,” says Losch, who was not involved with the research. “Identifying these feedbacks and their impact on the system is at the heart of climate research.”
As part of the “Estimating the Circulation and Climate of the Ocean” (ECCO) project, Heimbach and his colleagues are now applying their model to larger regions in the Arctic.
This research was supported in part by the National Science Foundation and NASA.
Written by: Jennifer Chu, MIT News Office
###
Note:Sloppy reporting by MIT, not citing the paper title or DOI. It doesn’t seem to be online yet here at the journal:
http://journals.ametsoc.org/loi/phoc
Doesn’t have this paper, in monthly or early edition that I can find by searching for the author names.
UPDATE: Perhaps in response to the complaint I sent to the PR officer and the author, they have now changed the text to read:
Before:
Heimbach and former MIT graduate student Ian Fenty, now a postdoc at NASA’s Jet Propulsion Laboratory, have published the results from their study in the Journal of Physical Oceanography.
After:
Heimbach and former MIT graduate student Ian Fenty, now a postdoc at NASA’s Jet Propulsion Laboratory, will publish a paper, “Hydrographic Preconditioning for Seasonal Sea Ice Anomalies in the Labrador Sea,” in the Journal of Physical Oceanography.
The feedback ? Well note that AMO is just as warm but the ice has stopped melting. That implies a NEGATIVE feedback.
“The Arctic ice cover reaches its peak each year in mid-March, before shrinking with warmer spring temperatures. But over the last three decades, this winter ice cap has shrunk: Its annual maximum reached record lows, according to satellite observations, in 2007 and again in 2011.”
Not sure what some of you are reading, but this article talks about the above. Ryan is correct in this situation, the paper talks about winter ice not at any other times of the year.
“Each winter, wide swaths of the Arctic Ocean freeze to form sheets of sea ice that spread over millions of square miles. This ice acts as a massive sun visor for the Earth, reflecting solar radiation and shielding the planet from excessive warming.”
During winter the ice prevents more energy from the warmer ocean from escaping. The ice only acts as a a sun visor around Summer, massive being the incorrect word when it is still around the freezing point. It is clearly talking about winter not any other seasons, therefore during this period the sun has no direct influence in the Arctic. Only by warmer ocean currents interacting with it from the tropics.
“The Northwest Passage has for centuries been considered a shortcut shipping route between Asia and North America — if it was navigable,” Heimbach says. “But it’s very difficult to predict. You can just change the wind pattern a bit and push ice, and suddenly it’s closed. So it’s a tricky business, and needs to be better understood.”
Only part here it refers to any other season, but Winter.
Summary – The model conclusion with further details is reflecting results from winter ice only. It is irrelevant about the sun influence in summer because it’s about winter.
Where is CO2 in this story ?
Eh???
Solar radiation is why it is warmer in the summer than in the winter. The thickness of the ice is a function of the air temperature above the ice and the water temperature below. The sun warms the air and the ice gets thinner. (The air doesn’t even have to be above freezing for that to happen.) The sun goes away, the air cools and the ice gets thicker.
The melting of the ice is hugely influenced by the currents under it. There are places called polynyas where ice never forms, no matter how cold the air gets.
The bottom line is that ice coverage is a function of solar radiation and ocean currents. That was the science forty years ago (when I first learned it) and it still is.
If you want a pretty accessible presentation on the processes involved, here is a link to a presentation by Budgell and Lien.
It’s nice to note that, being actual scientists not activists, they are clear about the problems they are having and the limitations of their work.
“Each winter, wide swaths of the Arctic Ocean freeze to form sheets of sea ice that spread over millions of square miles. This ice acts as a massive sun visor for the Earth, reflecting solar radiation and shielding the planet from excessive warming.”
Well, the ice that remains when summer returns. During the winter, the Arctic is in darkness. There is little to no sunlight reaching the ice to reflect.
You don’t need a climate model to do the calculation on Arctic sea ice vs open water.
Open water at 273 K radiates 315 W/m^2.
Average TSI at 71.3N latitude(Barrow, Alaska), from NREL, TSI averaged over 24 hour period based on measured data on the ground, 30 year averages-
Jan- 0
Feb- 13 W/m^2
March- 67 W/m^2
April- 154 W/m^2
May- 196 W/m^2
June- 204 W/m^2
July- 188 W/m^2
Aug- 108 W/m^2
Sept- 54 W/m^2
Oct- 21 W/m^2
Nov- 0
Dec- 0
These numbers are even smaller as you approach the N pole.
Downwelling radiation in the Arctic is around 140 W/m^2. Excess downwelling radiation from anthropogenic CO2 accumulated over the last century is 2 W/m^2. As you can easily calculate, the net heat balance with no sun is a loss of 173 W/m^2. The only months that have sufficient sun to prevent re-freeze are May, June and July. Convection dramatically increases the heat loss, and wind-driven spray makes it even larger. Open ocean in the Arctic winter can’t help but freeze.
Only have to look at ocean surface temperatures to confirm solar radiation virtually controls all of the temperature contours.
http://www.ssec.wisc.edu/data/sst/latest_sst.gif
Ryan, you didn’t get it. The Vizor ist up in summer. The ice is reduced, because it’s reduced. You understand now? Not? Hmm, to be honest, I neither. But if the Alfred-Wegener- Institut in Bremen agrees, I get suspicious. The leading members, Professors Meinhard Schulz-Baldes and Peter Lemke declare on their website, that the IPCC reports are the most reliable scientific publications in the world: http://www.awi.de/de/aktuelles_und_presse/hintergrund/klimawandel/interview_zur_klimawandeldebatte/. I swear, it’s real!! They are very independent and not at all biased, at least not more than Al Gore, the Potsdam Insitut für Klimafolgenforschung and the Burger-Seller at Metuchen Railway Station in NJ and the Australian Prime Minister. But anyway, the abstract does not sound that bad.
“This ice acts as a massive sun visor for the Earth, reflecting solar radiation and shielding the planet from excessive warming.”
I’m getting tired of this nonsense. Most of the time, Arctic ice is on night side where it doesn’t have anything to reflect. And even when it’s on day side, it’s inclined at very sharp angle and is not getting any great amount of insolation.
Instead, it acts as thermal insulation, preventing sea water to radiate even more energy out into the space and cool the Earth more than necessary.
Because it is this radiation what causes the ice to form. There’s no other cooling mechanism in polar regions.
Plusk says:
November 21, 2012 at 9:50 am
No one noticed that air temperatures over the Arctic Ocean are many degrees above average?
http://ocean.dmi.dk/arctic/meant80n.uk.php
That’s interesting. Although just the current year it shows summer temperatures are almost identical to the long term average,but in winter they are far above the average. Yet we are seeing record summer Arctic sea ice melt AND record winter sea ice formation.
This compelling that air temperatures (and therefore GHG warming) have minimal effect on sea ice extent.
Does anyone here with better math and physics than I, please tell me if a 30% difference in the arctic ice cover in the Arctic at the Fall equinox results in greater or fewer Watts of sunlight reaching the Earth than a 1% difference in cloud cover in the tropics on the same day.
Ryan said: Ummm, hardly. In the winter the ice sheet forms because there is no solar radiation and the Arctic is completely dark for 6 months. How then can it act as a solar vizor reflecting solar radiation and protecting the planet from excessive warming???
—
Global warming is strange science it causes the implausible to happen on a daily basis. Reflecting sunlight at night is just one of them. Please keep up.
chris y, so your information would suggest that if the arctice sea ice didn’t return during the winter (for some bizzar reason, maybe catastrophic warming or somehting) it would actualy help cool the earth? Esentualy the ice is acting as an insulating blanket, helping to keep the earth warm?
There’s some negative feedback for you. Amazing stuff!
It appears that they took the note about sloppy reporting seriously. The online article has been revised to read:
“Heimbach and former MIT graduate student Ian Fenty, now a postdoc at NASA’s Jet Propulsion Laboratory, will publish a paper, “Hydrographic Preconditioning for Seasonal Sea Ice Anomalies in the Labrador Sea,” in the Journal of Physical Oceanography.”
Thus providing the title of the paper and revising to indicate that it is not published yet.
@chris y
“You don’t need a climate model to do the calculation on Arctic sea ice vs open water. Open water at 273 K radiates 315 W/m^2.”
Perfect. Isn’t is amazing how clear things become when you apply basic physics? The fact is it is warmer under the ice than above it and as Jeff in Calgary points out, the ice prevents a lot of heat escaping.
Someone above mentioned that the ice was white and something about the angle of incidence for solar radiation. A white surface has to be raised to a higher temperature to get rid of the same amount of heat than a dark surface. The ice prevents heat getting ‘into the ice’ from below and it prevents heat getting in the ice from above. That is just the properties of a white icy surface. The angle of incidence has little effect when the surface is that bright white. Hence the interest in Black Carbon dropping onto the ice and snow. The record recovery rate this Fall was directly the result of the absence of ice – the sea water lost masses of heat as soon as the sun dropped below a certain threshhold angle. Expect more of the same if it continues to experience a large summer melt with storms etc.
Here’s something worth repeating:
The history of the Arctic sea ice record has now been re-done by the NSIDC.
The NSIDC – Meier 2012 – has a new paper which provides a more consistent history. September minimum down to 8M km2 now in the 1950s which seems more realistic compared to the 10M and 11M km2 it was before. (See the Acknowledgements at the end of the paper for a little surprise.)
http://www.the-cryosphere.net/6/1359/2012/tc-6-1359-2012.pdf
And The NSIDC – J Stroeve 2012 – has also redone the numbers for climate model predictions versus actual sea ice decline using the new history data (remember how the ice was melting so much faster than the models – the new data shows the difference is not so great anymore).
http://www.washingtonpost.com/blogs/wonkblog/files/2012/09/6a0133f03a1e37970b017c31e57448970b-800wi.jpg
http://nsidc.org/monthlyhighlights/2012/09/an-arctic-without-sea-ice/
http://www.agu.org/pubs/crossref/2012/2012GL052676.shtml
Way off topic, but apt for the date.
Happy Thanksgiving to Anthony, moderaters [-ors(?)] and all readers.
So many people like to say how the Arc is dark so much of the time. But,
only the North Pole spends half a year with dark or dusk, and the other half
with 24 hour sunshine. The Arctic Circle has all days except its two solstice
days having a sunrise and a sunset.
So many people like to say how low the sun is in the Arctic. But, the sun
only fails to exceed 23.5 degrees at the North Pole, and peaks at twice that
at the Arctic Circle.
So many people like to say how reflective water is when the sun is at a low
angle above the horizon. Water is about 11% reflective at 23 degrees, ~22%
at 15 degrees, and about 35% reflective at 10 degrees from parallel to the
water surface.
Northern hemisphere sea ice typically peaks only a week or two before the
vernal equinox, and is not down to its yearround average until usually
sometime in June. When insolation above the atmosphere in the Arctic is
greater than anywhere else, and above the figure for the equator on an
equinox day.
When the sun is 23 degrees above the horizon, sunlight passes through
about 2.5-2.6 times as much atmosphere as when the sun is at zenith – and
a lot still gets through. The sun is about that high 1.5 hours after sunrise
and about 1.5 hours before sunset on an equinox day at the equator,
roughly 2 hours after sunrise and before sunset on a mid to late spring day
or a summer day in Philadelphia. I have seen the sun upturn temperatures
as high as upper 70’s F (~25 C) 2 hours after sunrise in and around
Philadelphia.
And, northern hemisphere sea ice has some presence well south of the
Arctic Circle, even in May when the sun is getting high. For example, the
southen half of Hudson Bay is usually mostly ice-covered into the middle
of June.
Overall, Arctic and near-Arctic sea ice is more significant than its
detractors claim. And, this affects snow cover in North America, Asia and
Europe, down to latitudes as low as the low or mid 40’s in North America
and Asia. When spring comes in early at 50 degrees north latitude, the
sun is already moderately high and up a majority of the day.
Thankfully, there are positive feedbacks other than the surface albedo
one that I think IPCC overestimated, and there is a negative feedback
(lapse rate feedback) that I suspect IPCC does not consider to increase
as increase of greenhouse gases increases the lapse rate.
“The Northwest Passage has for centuries been considered a shortcut shipping route between Asia and North America”
For even more centuries it has been considered a shortcut shipping route between Europe and Asia.
Bill Illis, I always look for your comments.
@John robertson
“I had thought the Russian Tsar’s Navy, The US Navy,British Admiralty and the nordic countries all kept records of arctic currents and ditto for some of the fishing and whaling fleets”
What? You think a bunch of sailors and fishermen would know something about the seas they sail on? Of course not. You need MIT for that.
vukcevic (November 21, 2012 at 9:41 am) asked:
“Question is what makes sea currents change.”
Wind. This isn’t an unknown.
Jeff in Calgary says:
November 21, 2012 at 10:27 am
….. open water does a prety good job of reflecting solar energy, and I thin that the arctic pack ice would not do as good as many people think. It is not a smoth ice sheet like at a skating rink, or a flat white layer like fresh snow.
_____________________________________
As soon as the ice forms it is covered with a layer of soot from all those new Chinese coal plants /sarc or maybe not. A friend living in Alaska says the air pollution blowing in from China is sometimes nasty.