Guest post by Dr. Walt Meier, National Snow and Ice Data Center
Winds, Temperatures, and Arctic Sea Ice Extent
As the summer sea ice melt season gets into high gear, I thought I’d do a post on sea ice processes and other tidbits about sea ice that may be useful as people watch the seasonal sea ice extent decline. My thanks to Anthony for the opportunity to share this information.
Often, much of the focus in the news is on the effect of warming air temperatures on observed decline in Arctic sea ice extent, such as in the The Economist article. Others have suggested, such as in last Saturday’s post, that winds are the key to understanding the extent decline. These are not competing viewpoints, but reflect complementary contributions to changes in sea ice extent. For a full description of how sea ice changes – day-by-day, month-by-month, and over the years and decades – both wind and air temperatures (along with other factors, e.g., the oceans) need to be considered.
Winds and daily variations in extent
Winds primarily affect sea ice extent by pushing ice around, either spreading the ice out over larger area (increasing extent) or compressing it into a smaller area (decreasing extent). Often, day-to-day changes in sea ice extent are primarily due to changes in winds and not freezing or melting. The winds can also open areas of water within the ice-pack, called leads, if they push floes of ice apart. Thus, even during winter, there are open water areas or areas of thin ice (as leads begin to re-freeze) throughout the ice-pack. It is this feature that has allowed submarines to surface at the North Pole since the 1950s, even though the overall sea ice thickness was much greater in the 1950s compared to today. (In other words, surfacing subs at the North Pole are not an indicator of Arctic sea ice conditions.)
Winds and interannual changes in extent
Winds are variable, blowing at different directions and speeds. Thus over time, the effect of the winds settles into an average pattern and their net effect on extent is smaller relative to temperatures. However, average wind patterns can themselves vary over longer periods of time due to large-scale climate oscillations, most notably for the Arctic Oscillation (AO). During the late 1980s and early 1990s, the AO was often in a positive mode that favors the motion of older, thicker sea ice out of the Arctic. The remaining younger, thinner ice cover was more easily melted completely in the subsequent summers. This contributed to some of the summer extent decline during that period, as was noted in papers by Rigor and Wallace (2004) and Rigor et al. (2002). However, in recent years, this relationship appears to have broken down. After very strongly negative AO winters in 2009-2010 and 2010-2011, the summer sea ice again reached low levels (Stroeve et al., 2011).
Winds and summer extent
Even over a season, variation in the winds can play an important role. They were a key factor in the record low extent of 2007, as noted for example by Ogi and Wallace (2012) and Zhang et al. (2008) , who found that ~30% of the record low extent could be attributed to unusual ice motion (driven by the winds). According to Ogi et al. (2010), 50% of the year-to-year variation in extent can be explained by the variation in winds. Ogi and Wallace (2012) noted that if the wind patterns were similar to 2007, the minimum extent during 2010 and 2011 would have likely been as low as or lower than 2007.
Effects of winds and temperature on long-term changes in sea ice
Winds can also influence the long-term trend in extent. Ogi et al. (2010) estimated that up to 33% of the trend for 1979-2009 could be explained by winds. One mechanism for this long-term influence is via long-term changes in the winds, which have been noted by Ogi et al. (2010) and Smedsrud et al. (2009). Another effect on extent due to winds is in how effective winds are pushing the ice around. Spreen et al. (2011) noted that while some increase in wind speed is observed (in agreement with the Ogi and Smedsrud papers), the speed of the ice increased much more. In other words, the winds are becoming more effective at pushing the ice around.
The motion of sea ice is affected not only by winds (and other smaller factors), but also by the ice itself. Thinner ice is more easily pushed around by the winds than thicker ice (Haas et al., 2008). And the sea ice cover has been getting substantially thinner through the loss of older, thicker ice (e.g., Maslanik et al., 2011; Kwok and Rothrock, 2009). Zhang et al. (2008) found that thinner ice cover was a crucial factor in the 2007 ice loss and if the ice pack were thicker, a record low would not have occurred under the same winds. As mentioned above, some of this loss can be ascribed to the positive AO of a couple decades ago. However, since then the AO has been in a mostly neutral or negative mode and yet older ice has continued to be lost. For those interested, a nice animation of changes in ice age can be seen at the NOAA Climate Watch website.
Thus, the long-term thinning trend is primarily a reflection of additional energy from globally warming temperatures. Thick ice still moves out of the Arctic (or melts within the Arctic), but the additional energy in the Arctic prevents the replenishment of thicker ice at the same pace. The system is out of equilibrium and older, thicker ice continues to decline (though with some year-to-year variability). The additional energy is not always indicated by warmer local air temperatures though, especially in ice-covered areas. The Danish Meteorological Institute (DMI) air temperature estimates for north of 80° N, shows summer temperatures just above freezing during summer and there is little or no trend. This is because the additional energy is used to melt the surface of the ice and not warm the atmosphere, which stays near the melting point through the summer.
Conclusion
So, overall, the long-term decline in sea ice is mostly due to increasing temperatures leading to thinner ice cover that is more easily melted completely during summer. Winds accelerate or slow the long-term decline through the motion of thick ice out of the Arctic for period of up to a few years. The effects of winds may have longer-term consequences because their effect on ice motion increases as ice thins. The interplay between the two factors – wind and temperature – is perhaps best exemplified by the estimates for September sea ice extent in the recently released Sea Ice Outlook. There is a wide spread between different outlooks – about 500,000 square kilometers; even the uncertainties of a single method are on the same order of magnitude. That 500,000 square kilometer uncertainty reflects uncertainty in how the winds will vary this summer. However, all of the outlook contributions are more than 1.5 million square kilometers below normal, which demonstrates the effect of the long-term warming trend.
References
Haas, C., A. Pfaffling, S. Hendriks, 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.
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.
Maslanik, J., J. Stroeve, C. Fowler, and W. Emery (2011), Distribution and trends in Arctic sea ice age through spring 2011, Geophys. Res. Lett., 38, L13502, doi:10.1029/2011GL047735.
Ogi, M., K. Yamazaki, and J. M. Wallace (2010), Influence of winter and summer surface wind anomalies on summer Arctic sea ice extent, Geophys. Res. Lett., 37, L07701, doi:10.1029/2009GL042356.
Ogi, M. and J. M. Wallace (2012), The role of summer surface wind anomalies in the summer Arctic sea ice extent in 2010 and 2011, Geophys. Res. Lett., 39, L09704, doi:10.1029/2012GL051330.
Rigor, I.G. and J.M. Wallace (2004), Variations in the Age of Sea Ice and Summer Sea Ice Extent, Geophys. Res. Lett., v. 31, doi:10.1029/2004GL019492.
Rigor, I.G., J.M. Wallace, and R.L. Colony (2002), Response of Sea Ice to the Arctic Oscillation, J. Climate, v. 15, no. 18, pp. 2648 – 2668.
Smedsrud, L. H., Sirevaag, A., Kloster, K., Sorteberg, A., and Sandven, S. (2011), Recent wind driven high sea ice area export in the Fram Strait contributes to Arctic sea ice decline, The Cryosphere, 5, 821-829, doi:10.5194/tc-5-821-2011.
Spreen, G., R. Kwok, and D. Menemenlis (2011), Trends in Arctic sea ice drift and role of wind forcing: 1992–2009, Geophys. Res. Lett., 38, L19501, doi:10.1029/2011GL048970.
Stroeve, J. C., J. Maslanik, M. C. Serreze, I. Rigor, W. Meier, and C. Fowler (2011), Sea ice response to an extreme negative phase of the Arctic Oscillation during winter 2009/2010, Geophys. Res. Lett., 38, L02502, doi:10.1029/2010GL045662.
Zhang, J., R. Lindsay, M. Steele, and A. Schweiger (2008), What drove the dramatic retreat of arctic sea ice during summer 2007?, Geophys. Res. Lett., 35, L11505, doi:10.1029/2008GL034005.
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Latest graphs are on the WUWT Arctic Sea Ice page
Related articles
- The Economist Provides Readers With Erroneous Information About Arctic Sea Ice (wattsupwiththat.com)
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What about melting from below as a consequence of the high sea surface temperatures over the last few decades (from stronger El Ninos) flowing past Spitzbergen into the Arctic Ocean ?
“Thus, the long-term thinning trend is primarily a reflection of additional energy from globally warming temperatures.”
I was with you until this point. What is the basis for this statement?
The primary driver of the long-term thinning trend appears to be that thicker multi-year ice has been transported through the Fram Strait, i.e.;
In this 2011 paper “Recent wind driven high sea ice export in the Fram Strait contributes to Arctic sea ice decline” by L. H. Smedsrud, et al. used;
In this 2001 paper, “Fram Strait Ice Fluxes and Atmospheric Circulation: 1950–2000” by Torgny Vinje found that:
How can you conclude that “overall, the long-term decline in sea ice is mostly due to increasing temperatures leading to thinner ice cover” when you have provided no citations to support this conclusion?
One thing that many critics of WUWT miss is that this is a really good forum to reach a lot of people. Often more people than might read one’s own site. I’ve appreciated Dr. Meier’s responses on sea ice subjects and and am glad to see these “proactive” comments as we move into both peak sea ice melt and peak sea ice hype season.
As for me, I leave ice predictions to you guys!
Anthony,
I love your blog, and I just reblogged this post.
Keep up your work putting out the lies of the opposition.
Wayne
[REPLY: Wayne, Dr. Meier has been very forthcoming and one of the few to engage here and knows he has a tough audience. If you have a substantive objection to make, please engage. -REP}
“Below normal”
Excuse me. Normal according to what time frame? I have, for years wondered about the thirty year ice “normal”. If I am not mistaken the start of that thirty year “normal” was after a thirty year cold spell (40’s-70’s) so unless the ice did not increase during those thirty years of colder than ‘normal’ the thirty year average has to be biased towards a larger “normal” than we see today.
OK that’s just one scientists opinion but where did I make a logic mistake?
“Winds can also influence the long-term trend in extent. Ogi et al. (2010) estimated that up to 33% of the trend for 1979-2009 could be explained by winds…
Thus, the long-term thinning trend is primarily a reflection of additional energy from globally warming temperatures.”
Even if the 33% is true, the rest is not well founded. The main reason for the temperature increase is the positive AMO phase and this is not global warming. Temperatures in the arctic are not very different from the last peak 60 or 70 years ago. Soot is another issue.
“What is the basis for this statement? The primary driver of the long-term thinning trend appears to be that thicker multi-year ice has been transported through the Fram Strait”
Dr Meier said
“Winds can also influence the long-term trend in extent. Ogi et al. (2010) estimated that up to 33% of the trend for 1979-2009 could be explained by winds.”
So one might conclude that his educated opinion based on his life work is that wind accounts for 33% of the sea ice loss leaving the rest to increased energy uptake.
Clearly ice has declined recently. And all other things being equal, warming will result in less ice.
The only quibble I have with any of this is the use of the word “normal”. We don’t have good enough long-term data in my opinion to say what is usual with regard to ice coverage in the arctic or understand the full extent of its natural variation. Furthermore the word “normal” carries the implication that this level is in some sense ideal and that deviations from it are “abnormal” and potentially problematic. I have yet to see any evidence that recent declines in ice are causing, have caused, or are likely to cause any kind of problem.
Thus, the long-term thinning trend is primarily a reflection of additional energy from globally warming temperatures.
I’d like to see a plausible mechanism which allows warmer air temperatures to melt thicker older multi-year ice faster than thinner perennial new ice, before I accept your ‘thus’.
http://wattsupwiththat.com/2012/03/01/nasa-and-multi-year-arctic-ice-and-historical-context/
BTW, the likely mechanism is an increase in solar insolation and more embedded particulates (soot) accumulating on the surface of older ice decreasing its albedo.
Which also means melting ice is a significant cause of warming Arctic atmospheric temperatures, as it insulates the ocean from heat loss.
Apologies if this is double posted, but WordPress seems to have lost the first attempt.
Any sea ice study that bases a conclusion on observations between 1979 and 2010 is no more valuable than predicting the temperature at midnight based on the trend from 8:00am to 5:00pm.
Dr. Meier, is there any interest in an update of the historic sea ice estimations over the last century. I think, this data is based on a paper you co-authored. The pre-satellite data appears not to match with a multitude of historical reports and additionally there appear to be downward steps where datasets have been combined.
Links to historical data
http://www.real-science.com/new-giss-data-set-heating-arctic
http://i680.photobucket.com/albums/vv161/Radiant_2009/popularmechanics1957-2.jpg
Thank you, Dr Meier for taking the time to privide your insight. I see many references cited regarding wind as well as ice thickness studies for this article.
However, your explanation of the many drivers of ice extent relies heavily on the existence of warming temperatures in the Arctic. Yet any references to studies of the number of above freezing hours or higher daily temperatures in the various weather stations in the Arctic are not listed. Would it be possible to get unadjusted temperature references for support?
Hello Dr. Meier,
First, I think a thank you is in order for offering a post here. Hopefully the comments stay gracious enough to encourage continued posts. It is good to see.
Second, I want to present my major issue here. Your conclusion is that increasing Arctic temperatures are the main driver of ice decrease, yet the major swings in Arctic temperature are during the colder months according to the Denmark Institute temperatures. It is readily apparent to anyone with an understanding of the mechanics of statistics that the temperatures are wildly variable in the other seasons, but in melt season they are remarkably consistent. This can be seen by comparing the DMI actuals (red line) to the DMI averages (green line) in the WUWT Sea Ice tab (click your way through the years, readers). I wondered if you, or anyone else could quantify the effect of CO2 on this temperature variability?
Regards,
David Falkner
Let’s just hope it stays ‘warmer’ as the benefits of warming are far better than ‘coldening’ (as Tim Blair often describes it).
“So, overall, the long-term decline in sea ice is mostly due to increasing temperatures leading to thinner ice cover that is more easily melted completely during summer”
If so Dr. Meier how do you explain that
1) chartered maps in the 1930s (Danish) showing the same extent than during the 2000s, i.e. during a period of rapid mode of circulation high pressure anticyclones -Dust Bowl- not at all warming?
2) if as you claim global temperature rise influences arctic sea ice melt, how do you explain the increase dynamics observed remobilizing ice and stronger winds, higher waves documented in the Atlantic that cannot be associated with a diminishing poles/equator gradient?
3) If arctic ice state was a novelty, unprecedented interrupting a state of perennial stability how do you explain the absence of 100y old ice, 50 y old ice in the 1980s?
4) Since you wish to minimize modes of atmospheric circulation to the role of 0.8 C global temperature rise (on land, if we can trust HadCrut etc…) how come the shape of summer arctic sea ice is always the same?
5) How do you explain that during the global LIA, Arctic sea ice extent was in fact reduced as per a recent paper by a Canadian researcher? Is it that in fact, Arctic sea ice is no reliable proxy for Global Warming and that transitional periods toward cooling produce increased dynamics that for short periods can reduce arctic sea ice extent? Are you aware that during the onset of the last glaciation the Svalbard islands enjoyed a warming trend that finally was interrupted when the glaciation reached these islands (quoted in Leroux Dynamic Analysis of Weather and Climate 2010 Springer/Praxis)?
We are in the middle of the most rapid change in the earth’s magnetic field in recorded history. Most notably in the Arctic. We know from the fossil records that major climate change and species extinction are related to magnetic field changes.
The Antarctic is cooling, not warming as the south magnetic pole moves away from the geographic pole. The Arctic is warming as the magnetic pole moves towards the geographic pole. CO2 cannot explain this. Charged particles enter the earth’s atmosphere from the sun in fantastic quantities at the magnetic poles. As the magnetic poles move, so does the location of entry of these particles.
Completely ignored by the high priests of science in their quest to solve society’s problems through human sacrifice. Be it virgins or carbon tax, the solution is always the same, as are the result. More suffering and no benefit to anyone except the priests.
A thoughtful article, well written. Thank you Dr Meier.
One question which of course arises from your analysis is this: if the warming in arctic temperatures is due to six or so cycles of high solar activity, what would be the effect of 25 years of much lower activity?
We are about to have a most interesting period in climate science, if cycles 24 and 25 are much lower than the previous ones.
After all, if it has taken 30 – 50 years to bring summer ice extent down to where it now is, it wouldn’t take Einstein to predict that to return it to 1950s levels will take an equally long time……
It is therefore entirely likely that summer sea ice extent will remain relatively low until at least 2025.
The key outcome will be whether it shows a slow (or even accelerating) rise, stays static or continues on a downward trend toward little if any summer sea ice.
David Falkner says:
June 20, 2012 at 10:24 pm
the major swings in Arctic temperature are during the colder months according to the Denmark Institute temperatures.
==========
The same effect is found in the Canadian records. It is the low temperatures that are getting warmer. The high temperatures are unchanged. The same effect is found generally all over the world. The climate is becoming less extreme, not more extreme.
High temperatures are not getting any higher, which suggests there is strong negative feedback in the system as temperatures increase, which prevents high temperatures from rising higher. Only low temperatures are showing signs of increase, which suggests that feedback is not constant, that feedback varies as temperature.
Which suggests that averaging is masking what is actually going on with the climate. That climate science, in its fascination with using averaged data, is working against developing an understanding of climate.
Seems to me that temperatures higher than the 40 year average over the colder months
http://ocean.dmi.dk/arctic/plots/meanTarchive/meanT_2012.png
would have lead to less build up of thick ice, so of course it is now disappearing quicker.
Again, the fact that we are still climbing out of the little ice age (I hope we haven’t reached the peak yet), and that we don’t seem to have much reliable data going back much before than 40 year average (or it just not used because it is inconvenient?), makes the use of terms such as “normal” and “average” pretty much pointless terminology in a historical sense.
ferd,
“The climate is becoming less extreme, not more extreme. ”
yes, that does seem to be what the real life data is telling us. Sort of makes you wander how NICE the climate was during the MWP and Roman times. Must have been a pretty nice times weather-wise, I reckon. Barmy summer type days in Autumn and Winter.. yummm !! Plants must have luvved it !!! And now with the extra CO2 as well……. flourishing !!!!!
Dr Meier
Thanks for your article.
Can you tell me the range of tides in the Arctic?
Living next to the sea here in the UK (with a total tidal range of up to 5 metres locally) it is very noticeable that high tides- combined with strong winds- have a dramatic impact on shaping our beaches and moving sand dunes around. Similarly low tides, whilst helping to deposit sand would presumably have a bg impact in the arctic in helping to put pressure on ice as the water levels fall?
As a skier I am also aware of the dramatic impact of sun on snow/ice and whilst appreciating the diffrence in angles any increase in sun hours over a long term average would presumably have some impact?
tonyb
All the many graphs and data are neatly collated here, as many WUWT readers will know:
https://sites.google.com/site/arcticseaicegraphs/
[David Falkner says:
June 20, 2012 at 10:24 pm]…
An excellent post. Simply comparing the earliest (1958) with the latest (2011) demonstrates the remarkable consistency of summer air temperatures in the Arctic.
Good to read. My issue Dr Meir is with your use of the word “normal”. As we have less than 40 years reliable data, and lots of mostly ignored anecdotal evidence of similar melt in the 1920’s, please explain why you consider we have enough to define “normal”.
As I understand it — many years ago when they first reached agreement on how to divide up Colorado River water they used collected data for past river volumes to determine average overall volume — divding that amount up among the participating groups. No sooner was the ink dry on the treaty then the Colorado River returned to what was its historically normal and much lower flow rate. The [snip . . kbmod] has been hitting the fan ever since.
Until you start writing papers that include information about historic assessments of Artic sea ice extent you can’t be taken seriously. Certainly reports by scientists and explorers and sea captains about artic sea ice extent are better proxies than are the tree rings that are used as proxies for past global temperatures. I mean human beings were there — they saw things with their own eyes and reported what they saw.
Such reports might be as inconvenient for your ideas about the cause of artic sea ice loss as Dr. Mann found the Medieval Warm Period to be for his ideas about current temperatures. But I don’t know. Maybe such old data will support your ideas. Don’t you think it is worth your time to look? Or do you, employing some sixth sense that seems to have evolved among the new breed of climatologists, instincttively shy away from data that might refute your beliefs — consigning such to the memory hole?
I am not a scientist but just a casual reader of the things on this site — but obviously you are reaching conclusions using only part of the data available. You are not giving us the full picture and thus what you say is highly suspect. Your paper is just about as viable as that old Colorado River water treaty.
Eugene WR Gallun