Ice cover is near its minimum in The Arctic. The Sun is also setting in the Arctic.
Put those two pieces of information together, and it becomes clear that the September minimum has very little effect on the Earth’s shortwave radiation budget.
On the other hand, areas of open water allow longwave radiation to escape.
Put those two pieces of information together, and it is not at all clear whether late summer Arctic ice loss is a negative or positive climate feedback.
Add the extra moisture in the air due to the open water which in turn gives above ave snow extent which secures the cold for ice growth…Mother Nature Rules..Not Man!
I’m curious about this topic. Since about 2002, the ice extent in the Arctic has been below normal by quite a bit at the minimum.
Simultaneously, the DMI temperature records show that the air temps in the Arctic during the refreezing period (say, Sep to Jan) have generally been well above average during those years.
I started from the position that the air temps determined the ice cover and that higher air temps during the refreeze resulted in less ice, thinner ice, etc., so it wouldn’t be surprising that the next season’s minimum extent would come in lower than average once again.
However, is there a feedback from the above-average amount of open water to the air temperature? That is, are the higher than normal Oct-Jan temps possibly kept high due to the higher than normal open water area?
If that’s the case, then whatever is causing the reduced summer extent (say sea currents, for example) would have to change first, driving higher ice volume and only then would air temperatures return to their long-term averages. So, which is it? Ice extent drives air temps or air temps drive ice extent? Or both?
Any insights?
Incidentally, it’s fairly clear that ice strongly influences air temps in the summer, because no matter how sunny it is, the DMI air temp rarely moves more than a degree or so above the long-term averages.
I don’t understand the top post at all. A darker surface absorbs more heat than a brighter one. Open water is darker than ice. The oceans will warm, melting the ice. It’s possible uncovered water will be cooler at night than previous years in winter if the ice recedes (ice also traps heat in the water under it), but day-time warming will more than offset that, especially in the summer time, when the Arctic receives more sunlight hours per day.
Consequently, I expect winter temps to change little or maybe even get cooler in the Arctic if ice continues to recede for that period, and I expect the winter refreeze to cover a similar amount of area. But summertime temps will get hotter, as they have done over the the last couple of decades along with reduction of ice. The Arctic region has warmed more than any other large region on the globe over the last 30 years (at 4.7C per decade, according to the UAH satellite record). That’s year-round data, not just summertime. Observation doesn’t gel with the comments above.
Sorry, that should be 0.47C per decade – 4.7C per century.
One can compare Arctic temperature data with September sea ice coverage.
http://moyhu.blogspot.com/2010/07/arctic-trends-using-gsod-temperature.html
http://nsidc.org/images/arcticseaicenews/20091005_Figure3.png
I didn’t expect the correlation to be quite so good, but if one looks at the peak temp years (1995, 2005, 2007), they match very well with the record sea ice minimums of those years. Other factors are in play, of course, and the match isn’t perfect, but this data doesn’t corroborate the thesis above.
Summertime temps have not gotten hotter over the past couple of decades at least during the period they spend above freezing. They’ve remained quite stable and this year they were actually cooler as measured by DMI. The year-round average is a different story.
http://ocean.dmi.dk/arctic/meant80n.uk.php
That’s a very odd data set. I notes it doesn’t measure in 10ths of degrees (it measures in 5K scale).
From the same website, this is their sea surface temperature anomaly map.
http://ocean.dmi.dk/arctic/satellite/index.uk.php – (Change the main parameter to ‘sea surface temp anomalies’)
Summer time temps over the Arctic have increased. The anomaly map showing changes by as much as 4 and 5C + is for September, and greatly at odds with the data you showed from their other page – assuming I’m reading that page correctly. It’s not an intuitive graphic.
It’s also *seems* to be at odds with many published studies:
http://ao.atmos.colostate.edu/other_papers/2007GL029897.pdf
http://www.the-cryosphere.net/3/11/2009/tc-3-11-2009.pdf
http://psc.apl.washington.edu/zhang/Pubs/Steele_etal2007GL031651.pdf
http://www.esajournals.org/doi/full/10.1890/06-0503.1
… for example. All indicating a rapidly warming summertime Arctic over the last few decades.
Has anyone contacted DMI to ask about those graphics and the data behind them? I may do so tomorrow. Good night.
Areas that are ice free will of course increase in temperature. Te region north of 80N is never ice free, and temperatures have not increased there over the last 50 years.
Hey Barry..I meant that the open water is able to feed Moisture into the surrounding landmasses which can cool faster producing more snow than if the arctic was solid ice. The increased area of White reflecting Snow helps the land area cool even faster & in turn can transfer that cold back over the Arctic which will drop the SST down to the point of freezing which works especially well after the arctic loses the solar energy.This is one reason why we can see great rebounds…Its just another guess on my part & it would not hurt my feelings if somebody shot my theory down in Flames!
The Average Earth Albedo is 0.298 – 29.8% of the sunlight is reflected back to space without having an impact on Earth temperatures.
The Albedo of solid snow-covered sea ice is usually about 0.65 – 65% of the sunligh is relfected. As the melt season continues, the snow melts and melt ponds appear and the Albedo of late season sea ice will fall to about 0.4.
Open ocean water has an Albedo of 0.08 to about 0.2 – with ocean near the equator having the lower value and ocean at higher latitudes having the higher numbers (due to the lower solar incidence angle).
There is also cloudiness to take into account. On average, there is about 65% cloud cover and the optical thickness (the actual amount of sunlight that does not get through the clouds) is about 28%. So, regardless of the sea surface conditions, the Albedo is going to start out at least 0.18.
In July, open Arctic ocean water is going to have an Albedo (including clouds) of about 0.4. Sea ice covered regions will be about 0.6. So there is a calculable difference in the amount of solar energy being absorbed by the surface at this time of year (it is not a really big difference however).
By the time the melt season really gets going in August and September, the solar incidence angle declines to 20 degrees, then 15 degrees and finally 0 degrees several days after the solstice on September 21 (and the amount of sunlight reflected rises exponentially as this angle declines for both sea ice and open water).
When the sun gets down to about 10 degrees at 80N in late August, there is very little difference between open ocean water Albedo and sea ice covered Albedo, both are about 0.6 (and rise rapidly towards 0.95 for September 21st). So, by September, it makes no difference at all.
One should also keep in mind that surface area represented by the Arctic ocean basin(above 75N for example) is only 1.7% of the total Earth surface so it is not going to make any difference to global temperatures – only local ones – especially when the Albedo difference (including clouds) between sea ice and open ocean is so small.
I have contacted DMI and will update any response here, if they give permission.
I note that the surface area covered at DMI is 80 degrees North, which spends most of the year covered with ice. How much of the area 80 degrees north has been open water at melt minimum the last few years?
Other assessments of Arctic (summertime) temperature trends cover a broader area. I also noted that the DMI temperatures for October seem to have become warmer over the record.
The October temperatures for the past few years have been among the highest in the temperature record at DMI, lending credence to the notion that less ice equals more heat near the record minimums of the last few years. But that’s a heavily qualified conclusion, of course.
For the wider Arctic region, annual anomalies match fairly well with interannual sea ice coverage variability. There seems to be a correlation, particularly in the record-breaking years. Of course, other factors, like the surrounding land temperatures, and lateral heat transport through the atmosphere and oceans will have an impact, so I would not state anything here categorically. The same should apply, for the same reasons, to conclusions opposite to mine.
Had I the time and skill, I would collect sea surface data from stationary locations most impacted by receding ice over the record (more open water for longer periods over the record), and attempt to find the trend specific to the topic from observations. A large number of coastal sea surface measurements, if possible.
I finally got a reply from DMI. Below are parts of the email I received (I only edited out greetings and non-content stuff). Replies are in quotes and bolded.
This was the link I gave in the email:
http://wattsupwiththat.com/2010/08/05/dmi-polar-data-shows-cooler-arctic-temperature-since-1958/
I already figured that the area DMI covers is almost completely ice-bound year round. It was good to have that confirmed. The summer temperatures in other data sets (studies I mentioned) cover a wider area, and observe increased summertime Arctic temps over the long-term.
This doesn’t answer the question over whether an ice/albedo feedback has yet been observed, but it does put paid to the notion that DMI temps provide any insight. Until the sea ice at >80N has been significantly reduced, DMI data cover an area where the ice albedo has little changed over the satellite record. We must rely on data that from locations where summertime sea ice coverage has noticeably decreased over the long-term to see if there has been accelerated warming or not. One or a handful of locations won’t do. We need as many as possible to average out local dynamics and obtain a climate signal, if any.
There might be a clue in Arctic ocean temperatures, which have increased by half a degree (centigrade) per decade over the satellite record.
http://vortex.nsstc.uah.edu/public/msu/t2lt/uahncdc.lt – (trends along the bottom of the page for each region/decade)
The Arctic ocean is the fastest warming place on Earth – faster the land Arctic and the entire Arctic region. Arctic waters are getting warmer faster than anywhere else.