Yesterday, Dr. Meier commented on PIPS -VS- PIOMAS, here is Part 2
Here are some thoughts on three other sea ice issues addressed in recent posts: (1) concentration vs. extent, (2) the causes of the 2007 record minimum, and (3) whether it is possible for the Arctic to lose all its sea ice during summer. Again, I’m speaking only for myself and not as a representative of the National Snow and Ice Data Center or the University of Colorado at Boulder.
Concentration vs. Extent as a measure of the summer ice cover
Sea ice concentration fields are difficult to interpret during summer because of the significant melt that occurs. Areas of low concentration may include open water or ice with surface melt or some combination of both.
Atmospheric moisture, which is higher in the summer, can also affect the observed concentration (e.g., concentration values can change with passing storms). Extent is a more consistent and stable measure of the amount of surface covered by ice and is more legitimate in comparing the data from different years, which is why NSIDC uses extent. Because of the melt and atmospheric effects on concentration, it can be particularly misleading to Steve’s comparison of two single days of concentration data. If one wants to compare concentration, it is better to compare monthly averages, which smoothes out at least some of the ephemeral atmospheric and surface effects. Looking at anomalies for June from 1990 and 2010, there isn’t much difference in the middle of the Arctic (the 2010 anomaly is a bit lower) with lower anomalies in 2010 in coastal areas. Again though, in the central Arctic this may indicate more open water or simply more intensive surface melt. Comparisons with other years can be made at NSIDC’s Sea Ice Index.
Monthly concentration anomaly (in percent) for June 2010 (left) and June 1990 (right). Positive anomalies (higher than average concentration) are in red, negative anomalies (lower than average concentration) are in blue. Anomalies are relative to a 1979-2000 average.
Reasons behind the record low minimum 2007 ice extent
Ice motion has been discussed as a major reason for the record 2007 minimum. While ice motion was important, it was far from the only contributor. For example, Zhang et al. (2008) attribute ~30% of the ice volume loss to ice motion, with the remaining 70% due to pre-conditioning (i.e., thinner ice cover) and more solar heating. Kwok (2008) attributes 15% of the extent loss to motion of ice from the Pacific side across the pole toward the Atlantic. Ogi et al., (2008) calculated a 37% contribution of unusual winds (and resulting ice motion) to the September extent.
So, what else played a role? Kay et al. (2008) suggest that below normal cloud cover and enhanced solar energy played a role (though another study, Schweiger et al. [2008] suggest the role may have been limited). Steele et al. (2008) found anomously high sea surface temperatures during 2007, which enhanced melt. Lindsay et al. (2009) showed that by 2007, the ice cover had thinned enough to reach a threshold where a dramatic loss in extent was possible under conditions experienced during the summer of 2007. Furthermore, the thinner ice cover allows the ice cover to be blown by winds more easily (Haas et al., 2008) – i.e., the winds contributed to the low extent, but the thin ice enhanced the effect of the winds.
In other words, the 2007 minimum was not simply the result of unusual ice motion. It was the result of ice motion, enhanced melt, warmer ocean temperatures, and a long-term thinning trend seen in a variety of observations (Maslanik et al., 2007; Nghiem et al., 2007; Kwok and Rothrock, 2009). The same atmospheric conditions would not have led to such a low extent in earlier years when the ice pack was thicker. As Ogi et al. (2008) say (with clarifying comments by me italicized in brackets): “… the precipitous decline in September SIE [sea ice extent] in recent years is mainly due to the cumulative loss of multi-year ice: summertime SLP [sea level pressure] anomalies [which control the strength and direction of the wind anomalies] have played an important role in setting the timing of record lows, but the long term trend is mainly due to preconditioning [the thinning of the ice cover].”
Can the Arctic really become sea ice-free during summer?
It has been suggested that the Arctic really can’t lose all its sea ice during summer because there isn’t enough energy to melt all of the ice in the short summer. There are a couple of reasons why this thinking is faulty.
First, we know the Arctic can potentially lose all its sea ice during summer because it has done so in the past. Examination of several proxy records (e.g., sediment cores) of sea ice indicate ice-free or near ice-free summer conditions for at least some time during the period of 15,000 to 5,000 years ago (Polyak et al., 2010) when Arctic temperatures were not much warmer than today.
Second, the primary evidence provided for the implausibility of ice-free summers is the plot of daily temperature for regions poleward of 80 degrees N from the Danish Meteorological Institute. It shows that temperatures rise only a couple degrees above freezing for a period of about 75 days throughout the entire record since 1958. So there is no warming trend of the surface air temperatures in the high Arctic. So how could one possibly melt ice near the pole with summer temperatures at most a couple degrees above freezing with no increasing trend?
North of 80 degrees, the Arctic has been continuously covered by ice, even during summer, throughout the entire record (except for a small area briefly during summer 2007). As a result, any heat energy in the vicinity will be used to melt ice and will not raise temperatures. Only after the ice melts can the ocean absorb the energy allowing the ocean surface and the air above it to warm significantly. So the summer near-freezing temperatures don’t say anything much about the energy available to melt ice, only that ice is melting. (I’ll note that it is possible to have higher air temperatures locally, for example due to a weather system bringing in warm air from the south, but the average over the entire region will stay near freezing).
However, there are still only ~75 days of melt, which isn’t much time. But one needs to think about the overall process of what happens in the Arctic, not simply the direct solar energy. As temperatures increase, summer extent decreases, which allows more absorption of solar energy. This melts more ice, decreasing the extent and thinning the ice. Heat absorbed in the ocean away from the ice edge will warm the ocean waters, which will delay freeze-up in the fall. This leads to less ice growth further thinning of the ice. With warmer temperatures, melt will begin earlier in the spring and freeze-up will start later in the fall (as has been observed, e.g., Markus et al. [2009], Serreze et al. [2009], Stroeve et al. [2006]). This is a positive feedback (the sea ice-albedo feedback). Under this feedback, the ice will eventually become thin enough to melt completely most everywhere in the Arctic during a single summer.
There is little doubt in the sea ice community that during summer the Arctic can become ice-free and will become ice-free as temperatures continue to rise.
References
Haas , C., A. Pfaffling, S. Hendricks, L. Rabenstein, J.‐L. Etienne, and I. Rigor, 2008. Reduced ice thickness in Arctic Transpolar Drift favors rapid ice retreat, Geophys. Res. Lett., 35, L17501, doi:10.1029/2008GL034457.
Kay, J.E., T. L’Ecuyer, A. Gettelman, G. Stephens, and C. O’Dell, 2008. The contribution of cloud and radiation anomalies to the 2007 Arctic sea ice extent minimum, Geophys. Res. Lett., 35, L08503, doi:10.1029/2008GL033451.
Kwok, R., 2008. Summer sea ice motion from the 18 GHz channel of AMSR-E and the exchange of sea ice between the Pacific and Atlantic sectors. Geophys. Res. Lett., 35, L03504, doi:10.1029/2007GL032692.
Kwok , R. and D.A. Rothrock, 2009. Decline in Arctic sea ice thickness from submarine and ICESat records: 1958–2008, Geophys. Res. Lett., 36, L15501, doi:10.1029/2009GL039035.
Lindsay, R.W., J. Zhang, A. Schweiger, M. Steele, and H. Stern, 2009. Arctic sea ice retreat in 2007 follows thinning trend, J. Climate, 22, 165-176.
Markus , T., J. C. Stroeve, and J. Miller (2009), Recent changes in Arctic sea ice melt onset, freezeup, and melt season length, J. Geophys. Res., 114, C12024, doi:10.1029/2009JC005436.
Maslanik, J.A., C. Fowler, J. Stroeve, S. Drobot, J. Zwally, D. Yi, and W. Emery, 2007. A younger, thinner Arctic ice cover: Increased potential for extensive sea-ice loss, Geophys. Res. Lett., 34, L24501, doi:10.1029/2007GL032043.
Meier, W.N., 2005. Comparison of passive microwave ice concentration algorithm retrievals with AVHRR data in Arctic peripheral seas, IEEE Trans. Geosci. Remote Sens., 43(6), 1324-1337.
Nghiem, S.V., I.G. Rigor, D.K. Perovich, P. Clemente-Colon, J.W. Weatherly, and G. Neumann, 2007. Rapid reduction of Arctic perennial sea ice, Geophys. Res. Lett., 34, L19504, doi:10.1029/2007GL031138.
Ogi , M., I.G. Rigor, M.G. McPhee, and J.M. Wallace, 2008. Summer retreat of Arctic sea ice: Role of summer winds, Geophys. Res. Lett., 35, L24701, doi:10.1029/2008GL035672.
Polyak, L., and 17 others, 2010. History of sea ice in the Arctic, Quaternary Science Rev., 29, 1757-1778, doi:10.1016/j.quascirev.2010.02.010.
Schweiger , A.J., J. Zhang, R.W. Lindsay, and M. Steele, 2008. Did unusually sunny skies help drive the record sea ice minimum of 2007?, Geophys. Res. Lett., 35, L10503, doi:10.1029/2008GL033463.
Serreze, M.C., A.P. Barrett, J.C. Stroeve, D.N. Kindig, and M.M. Holland. 2009. The emergence of surface-based Arctic amplification, The Cryosphere, 3, 11–19.
Steele, M., W. Ermold, and J. Zhang, 2008. Arctic Ocean surface warming trends over the past 100 years, Geophys. Res. Lett., 35, L02614, doi:10.1029/2007GL031651.
Stroeve, J., T. Markus, W.N. Meier, and J. Miller, 2006. Recent changes in the Arctic melt season, Ann. Glaciol., 44, 367-374.
Zhang, J., R. Lindsay, M. Steele, A. Schweiger, 2008. What drove the dramatic retreat of arctic sea ice during summer 2007?, Geophys. Res. Lett., 35, L11505, doi:10.1029/2008GL034005.
Until proven otherwise, I will continue to believe that the ice melt extent etc is related to the higher solar output that existed from throughout the last half of the 20th Century. While “models”, created by people with practicly no knowledge of the complete impact of the Sun on Climate, make ignorant claims about the contribution of the sun, it stands as fact, that we do not know the extent to which the sun impacts climate.
As noted by Dr Mier, the arctic has been ice free before, .. and it froze back up. We know that the arctic must have been quite warm as recently as 1000 years ago, when the Vikings settled Greenland, and yet, “Greenland” turned to Iceland in a relatively short period of time. Another fact that remains, is that NO modern climate research has been done during a prolonged period of solar minimum. Taking into account all the proposed lag times and the dynamics that exists regarding climate, most of which is poorly understood, the next 10 years could turn ALL of the accepted theories on their heads.
Ah, “pre-conditioning” re 2007. Yes, I shall use that term in the future. I’ve always agreed that the 2007 situation was multiple reasons, and that “pre-conditioning” (which isn’t what I’d been calling it before right now) is certainly an important one.
Dr. Meier, I must say I’ve noticed a tendency towards “worse than we thought” reporting tendencies from NSIDC. One of the things I’d like your organization to consider is to the degree you get ahead of yourselves you do no one any favors.
“As bad as we thought in 2006” should be bad enough. You are now potentially faced, if Steve is right (and I predicted even higher than he did, tho I was silly enough to do it two months earlier unnecessarily, tho I largely agree with his analysis and have said so repeatedly), with a situation where as of minimum extent for 2010 you may have in fact more-or-less “returned” to the Pre-2007 trend.
But because there was some excited overanalyzing of 2007, and predictions of imminent doom based thereon, now you are going to find it much harder to get a “it’s as bad as we thought it was in 2006, which is plenty bad enough” message across to the public if 2010 returns the trend line to pre-2007 historic decline rate. And the only fault for that will be NSIDCs. I don’t know about you, but I think that is really unfortunate.
Anthony, has anyone done a study to compare Earth’s Aphelion distances on July 6 each year to that of ice extent on Antarctic ice during the Southern Hemisphere’s winter?
2010-Jul-06 11-hour Earth at aphelion 1.016702 AU (94,528,559 miles or 152,096,452 km)
How about Earth’s perihelion distance on Arctic ice extent during the Northern Hemisphere’s summer?
2010-Jan-03 00-hour Earth at perihelion 0.983290 AU (91,422,023 miles or 147,098,036 km)
Dave says:
July 14, 2010 at 4:00 pm …
Why does it have to be solar? What I’m pointing out is that nothing “just happens” in the natural world, with no cause. Maybe the mechanism is subtle, hard to discover, difficult to pin down scientifically, but there is always a cause. Natural variability, however, is never it – though it may be a useful term to group together a collection of common, oft occurring processes for simplified reporting.
So, to just exclaim “Natural Variability!” is as unreasonable as the old “God did it!”.
I’m a little confused by Jakers claims. It seems he believes gravity (among many other phenomena) simply doesn’t exist. Hmmmmmmmmmmm.
This is a positive feedback (the sea ice-albedo feedback). Under this feedback, the ice will eventually become thin enough to melt completely most everywhere in the Arctic during a single summer.
This albedo feedback makes sense, but there is something that makes me wonder.
There is something else that doesn’t happen under ice, but does once the ice is melted: The exposed water is able to begin evaporating. Isn’t this true? If so, wouldn’t that be a negative feedback towards sea temperature?
Living in Texas, I don’t really know how big that feedback would be in the arctic. It certainly makes a huge difference here. Here in July, a dark wet cotton shirt is more comfortable than the whitest waterproof jacket because it allows sweat to evaporate.
In the winter, I feel a lot warmer wearing a pure white dry jacket over a darker wet one.
Another thing: if I put a pitcher of tea in the fridge (not freezer) with the cover on, the tea stays liquid, no matter how long it is left there. If I put the pitcher in uncovered, the tea ices over on the same day.
Evaporation just seems like a pretty powerful negative feedback to me. It is something we experience commonly. And it seems strange that such a thing would not be mentioned along with the albedo feedback.
Jakers – the whole problem is that we humans do not have perfect insight into what makes weather, let alone climate. This whole AGW nonsense started with Phil Jones saying, in effect, that CO2 must cause the temperature to increase because we can’t explain it any other way. What he should have said is that we don’t know why temperatures were rising because climate science is still in its infancy. Money that could have been used to explore the relationship of, say for example, magnetic magma movements or solar fluctuations, has been wasted on the kind of doggeral that Mann et. al. have been shoving out.
I thought of something else about evaporation. The albedo feedback is only applicable during sunshine. Evaporation feedback is applicable when the sky is clear, cloudy, and even at night.
So if one can say (in theory) that the albedo feedback melts more ice, requiring more time for the winter to refreeze it, resulting in an earlier spring melt…
can one also say (in theory) that the evaporation feedback cools more water, requiring less time for the winter to refreeze it, resulting in a later spring melt?
dscott says:
July 14, 2010 at 4:49 pm
I argued that the South Pole was colder due to being farther away in winter than the North Pole in 8th grade General Science.
The teacher laughed, and said that was not possible due to the South Pole being closer in the summer.
Rhoda R says:
July 14, 2010 at 5:58 pm
How many billions have been wasted chasing a ghost cause?
I agree. There is so much more that could have been spent on other research.
What a terrible waste.
Thank you Dr. Meier.
What a lot of the commenters apparently fail to realize is that for a very large portion of the broad sector of the scientific endeavour that can be called “climate science”, the current indications of climatic warming due to increasing atmospheric greenhouse gases are a “given” — or a starting proposition, or a boundary condition, if you will.
For them to abandon this starting proposition, they would have to be shown universally that there are eminently plausible reasons NOT to take this expectation as a given. For Dr. Meier to say “There is little doubt in the sea ice community that during summer the Arctic can become ice-free and will become ice-free as temperatures continue to rise” is as natural as his breathing reflex. There’s no rational way for them to think any other way.
A thoroughly enjoyable read and a window into the mind of a very educated person, thanks Dr Meier.
One point does stand out though, if as Walt suggests the Arctic was warmer and ice free in the past then why does he believe that this time the warming is anthropogenic in nature and not natural?
If a natural cycle managed to warm the planet beyond what we are seeing right now then I fail to see just how a CO2 signal can be detected over and above a natural rise.
These questions aside, Its great to see guest posts such as this as it adds to my knowledge base to give me a fuller picture of wahts going on.
The south pole is colder primarily because it is at high elevation.
jakers says:
July 14, 2010 at 3:16 pm
“But if, as has been argued here often, climate sensitivity is low, this variability with no forcing would be very very small. You can’t have it both ways.”
Here;
http://www.drroyspencer.com/2010/06/millennial-climate-cycles-driven-by-random-cloud-variations/#comment-134
Michael Penny says:
July 14, 2010 at 1:04 pm
So if “Examination of several proxy records (e.g., sediment cores) of sea ice indicate ice-free or near ice-free summer conditions for at least some time during the period of 15,000 to 5,000 years ago”? How come we still have polar bears?
Polar bears are smart. They can tell the difference between natural warming and CAGW. CAGW scares the crap out of them.
It seems that we have 30+ years of good satellite data of both area and extent for both poles. However, there does not seem to be a comprehensive description of the year to year causes of the annual maxima, minima and rates of change in each year. This will require a major effort to collect together the regional meteorological and oceanographic data, which is sparse in places, and to match this to the ice patterns. But if we can’t explain the 30 years for which we have good ice data then there is little hope of predicting future positions.
So if “Examination of several proxy records (e.g., sediment cores) of sea ice indicate ice-free or near ice-free summer conditions for at least some time during the period of 15,000 to 5,000 years ago”? How come we still have polar bears?
Because they adapted to ice free conditions, and adapted back the way once the ice reformed. And if they did it once they can do it again.
Dr Meier states “First, we know the Arctic can potentially lose all its sea ice during summer because it has done so in the past. Examination of several proxy records (e.g., sediment cores) of sea ice indicate ice-free or near ice-free summer conditions for at least some time during the period of 15,000 to 5,000 years ago (Polyak et al., 2010) when Arctic temperatures were not much warmer than today. ”
So what is all the fuss about?
Jakers,
There are many MANY factors involved in natural variation. One of the reasons that “climate science” is in such an awful state right now is that even the “climate scientists” do not fully understand all of the perfectly natural variables involved, nor do they understand how all of these variables interact. This is precisely why the vast majority of models are hopelessly wrong.
In order to have a “good” model, you should know what a vast majority of the variables are and you should have a pretty darn good idea of how all of the variables interact with each other. Right now, most climate models can be characterized as educated guesses at best.
If you actually follow this site at all, you already know that SOME of the variables involved are insolation, cloud formation, oceanic cycles, solar activity (or lack thereof), orbital variations, precession, and many many others. You should already know at least that much if you do actually read the articles on this site. You should also know that we have barely even begun to scratch the surface on how all of these things interract, although there are certainly scientists attempting to ascertain the interractions between all of these forces and how they influence climate and on what time-scale.
There are a couple of reasons why this thinking is faulty.
That’s a nice way of putting it… “faulty thinking”.
“I believe your faulty knowledge and faulty concentration have led you to some faulty thinking, good sir”.
I bet Internet comments would have been much more polite if the Internet were invented back in the 1880’s – too bad Charles Babbage couldn’t get the funding he needed.
http://en.wikipedia.org/wiki/Charles_Babbage
Dr. Meier,
is this the fly in your ointment?
First, we know the Arctic can potentially lose all its sea ice during summer because it has done so in the past.
Apparently without the aid of CO2, eh? But generous of you to admit it.
jakers says:July 14, 2010 at 4:53 pm
Why does it have to be solar? What I’m pointing out is that nothing “just happens” in the natural world, with no cause. Maybe the mechanism is subtle, hard to discover, difficult to pin down scientifically, but there is always a cause. Natural variability, however, is never it – though it may be a useful term to group together a collection of common, oft occurring processes for simplified reporting.
So, to just exclaim “Natural Variability!” is as unreasonable as the old “God did it!”.
Now there’s some logic. It fits right in with the rest of the AGW mantra:
We can’t find any other causative mechanism, so it has to be CO2. After all we have a correlation.
Yeh, that’s the ticket.
stevengoddard says:
July 14, 2010 at 10:01 pm
The south pole is colder primarily because it is at high elevation.
I figured that out much later. Back in the 60’s, we didn’t have instant data access, just what was in our textbooks.
Now, we only need to figure out why one pole’s ice grows while the other shrinks.
At one time, the Arctic was doing the same thing that the Antarctic now does..make more ice.