Climate Science Glossary

Term Lookup

Enter a term in the search box to find its definition.

Settings

Use the controls in the far right panel to increase or decrease the number of terms automatically displayed (or to completely turn that feature off).

Term Lookup

Settings


All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Home Arguments Software Resources Comments The Consensus Project Translations About Donate

Twitter Facebook YouTube Pinterest MeWe

RSS Posts RSS Comments Email Subscribe


Climate's changed before
It's the sun
It's not bad
There is no consensus
It's cooling
Models are unreliable
Temp record is unreliable
Animals and plants can adapt
It hasn't warmed since 1998
Antarctica is gaining ice
View All Arguments...



Username
Password
New? Register here
Forgot your password?

Latest Posts

Archives

Ice-Free Arctic

Posted on 7 November 2010 by Riccardo

Talking about ice-free arctic often triggers a lot of shouts and accusations of catastrophism. Yet, we know that the arctic has already been ice-free in summer before. We know it's possible, what is left to understand are the conditions which may produce such an event.

There is evidence (Polyak et. al 2010) that current conditions of an extensively glaciated Arctic were established at the beginning of the Pleistocene, about 3 million years ago. The quaternary glacial-interglacial cycles, governed by orbital cycles, are reflected in the Arctic sea ice extension. At times, average temperature has been 3-5 °C higher than present and totally or almost totally ice-free conditions during summer occured.

It is thought that the main driver of these ice retreats is summer insolation at high latitudes, though regional effects (e.g. the presence of large ice sheets) produce geographically non uniform or delayed retreats. The last occurrence of a maximum in northern high latitude summer insolation was about 10 thousand years ago. It was a generally warmer than present period, but not uniformly so, and the temperature north of 60° was a couple of degrees centigrade above present (Kaufmann 2004).

A recent review on arctic ice variability suggests that "the seasonal Arctic sea ice cover was strongly reduced during most of the early Holocene and there appear to have been periods of ice-free summers in the central Arctic Ocean". This finding lowers the "threshold" for an ice-free summer to a few degrees centigrade of warming.

This fact may come as a surprise. Indeed, IPCC projections of summer arctic sea ice extent, while showing an overall decrease, do not show ice-free conditions up to at least the end of 21st century.

Observed (red) and modeled September Arctic sea ice extent (Copenhagen Diagnosis 2009)

But as the figure itself shows, the projections do not agree well with the real world. Measurements of the ice extent (red curve, updated to 2008) show a much steeper decrease in the last 30 years. Modelling results have shown that "abrupt reductions are a common feature of these 21st century simulations". Ice albedo feedback and increased ocean heat transport are identified as the culprits of these abrupt reductions.

An anticipated consequence of the ice albedo feedback is that the september minimum ice extent reduction trend should at first increase. At some point, the remaining ice extent becomes too small for its reduction to have a significant amplification effect and the decreasing trend slows down. We can easily check where we're now by looking at the NSIDC september ice extent.



NSIDC september arctic sea ice extent (black) with a second order polynomial fit (red).


The linear fit (not shown) gives a trend of 80,000 square kilometers of sea ice extent loss per year or about 12% of the average over the full period per decade. But the analysis of the residuals shows that a second order polynomial is more appropiate. Then, we can confidently say that over the period 1979-2010 the downward trend has accelerated.

In summary, we know that a summer ice-free arctic is possible, that it does not require extremely high temperature, that we're not far from there, and that the downward trend is accelerating. So, why should we be surprised when scientists say that in a few decades we'll easily sail to the North Pole in September?

0 0

Printable Version  |  Link to this page

Comments

Prev  1  2  

Comments 51 to 77 out of 77:

  1. #49: "(to do with geomagnetic research, solar winds, " If you want to invoke solar winds, explain recent heating concurrent with weakening of the solar wind. Solar wind output is at its lowest since accurate records began 50 years ago. This finding comes from the seasoned ESA/NASA solar probe Ulysses, which completed nearly three polar orbits of the Sun from 1993 to 2008 Why is it necessary to speculate about these exotic mechanisms? Arctic ice melts in response to warming temperatures.
    0 0
  2. Hi, Daniel #47 (Go Spartans!) To followup with more ICESAT results, a NASA analysis of satellite data has quantified the amount of multiyear sea ice lost through melt from the Beaufort Sea (~30%) vs Advection through Fram Strait (~50%). See also this write-up on ClickGreen.org
    0 0
  3. Re: Artful Dodger Thanks for the links, I'll check them out tomorrow afternoon when I have more time. Your ice expertise would be of great value here, if present more regularly. A possibility? Guest posts available... ( - AD runs away, screaming "No, my Precious! We mustn't writes us a guest post, Nooooo..." - ) The Yooper
    0 0
  4. Arkadiusz Semczyszak @ 48: “Changes that took place 6000-7000 years ago were controlled by other climatic forces than those which seem to dominate today ... " D'oh! Why didn't I think of that? Changes in the distant past, whether local or global, were not caused by a plague of monkeys burning carbon. ;) muoncounter @ 51: Arkadi already mentioned that changes in the past had different causes, although we can still say that ice melts, and melted in the past due to sufficient energy in its environment to supply the heat of fusion. This is where ocean currents among other things come in.
    0 0
  5. Re: Artful Dodger (52) Digested the links. Sobering. From 2004 to 2009 (using ICESAT data), 336 cubic miles of multiyear ice, or about 3 times the volume of Lake Erie (if represented as ice), has been lost to melt, not advection out the Fram or other exits. Gone. See ya, ne'er-pass-this-way-again. Finito. And under the column 'Peak year of loss' for $200? Any takers? Bueller? Nope, not 2007. 2008 lost about 50% more ice due to melt than 2007. Think on that for a minute. So much for the "recovery". The next summer with a strong Arctic Dipole sees an ice-free pole. Especially if it coincided with a strong El-Nino and/or a wakening sun. If not 2011, then 2012 becomes likely... We live in interesting times. The Yooper
    0 0
  6. Too right, Daniel. In 2007 persistent winds herded Sea Ice into an anomalously small Extent, but the resulting compaction actually preserved ice that would otherwise have melted earlier. In 2008, -09 and -10, spreading sea ice resulted in dramatic melt, as measured by Volume. We have perhaps only 2 or 3 years until all the multiyear sea ice in the Arctic is gone.
    0 0
  7. Re: Artful Dodger (56) Sounds like time for a beer then. Because the world is going to find out what the loss of the Northern Hemisphere's refrigeration system is going to mean. Didn't think it would happen on our watch. The next melt season will be fun, though. The Yooper
    0 0
  8. Daniel: Here's a sobering read "A World without Ice", Henry Pollack (2009). This could be like quaffing Jaggie and Red bull after a Spartans game! But what a head-ache the day after...
    0 0
  9. Thanks, Dodger! Busy day on tap tomorrow, but I'll check that out tomorrow night. Looks cool (sorry)! BTW, my wife and son went to the MSU:UM game this year (I had to work on getting ready to move into our new house out of the old one). Lucky buggers. The Yooper
    0 0
  10. This one. Warm Arctic in 1922. And this: If you don't want to read this at least look at Figure 3 of Arctic temps. Now this in conjunction to the above link: Last nine years of Arctic sea ice extent. It is true the last decade of sea ice is much less than in the 1970's, but the 1970's were much cooler. But the last nine years do not show a downward trend. They are sitting in a pattern determined by a current warming phase of the Arctic. Will it continue to warm up? The next few years should let us know. 2007 was the lowest summer extent but 2009 was in the middle. I can't see a continued downward trend from the linked data unless the temps continue to rise.
    0 0
  11. #60: "the last decade of sea ice is much less than in the 1970's, but the 1970's were much cooler. " Yes, now you're getting it. "the last nine years do not show a downward trend." No legitimate prediction says that there is a monotonically decreasing ice extent. Individual years fluctuate; always have, always will. But look at the AMSR graph objectively: lowest mins, in order are 2007, 2008, 2010, 2009, 2005. Get the pattern? "a pattern determined by a current warming phase of the Arctic." Yes, one that's been around since the mid 70s.
    0 0
  12. "It is true the last decade of sea ice is much less than in the 1970's, but the 1970's were much cooler." hrmmm . . . I wonder why that could be . . . "But the last nine years do not show a downward trend." Wha? Whatchu smokin? Go here and then repeat that with a straight face. You might also note the wide swings in the last couple of years. Theory: decreasing summer ice means a rapid increase in new winter ice, but since the ice is new and not so thick, it melts quickly with the onset of summer. Each year, for the last decade, the multi-year ice volume has decreased. "They are sitting in a pattern determined by a current warming phase of the Arctic." Yes, a current warming phase--lasting at least 30 years. October temps were 4-6C above the 1979-2000 average. When was the last 30 year period that saw such a steady decrease? "Will it continue to warm up? The next few years should let us know." That's right. Keep watching the global temps. When you think it's time to do something about it, do it. I imagine others feel the same way (and are currently trying to do something about it).
    0 0
  13. #62 DSL I did go to your link. I like the actual ice measurement extent Actual ice extent. If you look at the actual amount of ice melt and refreeze it would be a straight line between the two for all the years. In the early mid 2000 decade there was less summer melt but less winter refreeze, after 2007 the summer melt is greater but so is the refreeze in the winter. Did you look at Figure 3 of my second link? Yes the 1970's were cool but figure 3 shows the 1930-1940 decades were as warm in the Arctica as they currently are.
    0 0
  14. #63: "actual amount of ice melt and refreeze it would be a straight line between the two for all the years." No. The September seasonal min anomalies are dropping much more rapidly than the March seasonal max. That's been discussed a number of times in prior articles. This requires more intense melt seasons, followed by a widespread refreeze forming 'new ice'. New ice melts more rapidly than old ice.
    0 0
  15. Norman, let me ask you something. The stuff you are promoting suggests that the decline of Arctic sea ice has just been a 'natural cycle' which should end 'any time now' (actually about ten years ago). You've convinced yourself that the past nine years are 'flat' (for the record, they look more like 'straight down' to me) and thus that the inevitable ice growth of the natural cycle is right around the corner. If five years from now Arctic ice has grown considerably I'd be absolutely shocked and need to re-examine how the apparently overwhelming indications to the contrary could all have been so wrong. So here's the question... if in five years Arctic sea ice is instead sharply lower even than current levels will that be an indication to you that something is very wrong with what you have chosen to believe? Or will you just accept whatever the new 'skeptic' explanation is (my money is on, 'oh we expected the Arctic to melt out entirely all along... this is completely normal and really happens all the time') and go on disbelieving all evidence to the contrary?
    0 0
  16. #65 CBDunkerson Well in your understanding of the Climate science, do we have 5 years to watch and see? Or are there climate tipping points of no return? I will keep watching the Arctic Ice to see. I am even doing my own research on my own local area (Omaha Nebraska) to see what the data indicates. On a daily basis I log the Daily High/Low temps Log the Normal High/Low temps Calculate the anomaly (I put it on an Excel spread sheet). I log the Record high and Low temps an log the years they took place. I am monitoring the low temps as one of the fingerprints of AGW theory is warmer nights. I was convinced in the 1990's that Global Warming was a quite real (I could walk around in a T-shirt outside in January, temps in the 60's F). It was a climate shift for me from my experience as a child. My memory was of cold and snowy winters. What started my active research on the other side (you call it denier) was when a co-worker told me about how hot it was in the 1930's (from a story about his Father watering cows in the heat). I thought it was just exaggeration of memory until I started to log record high temps for myself and found the 1930's (in the Nebraska and Iowa region) were much hotter than the heating going on in the 1990's. A quick stat. Before 1970 (in Omaha Nebraska) there were 18 record high temps. After 1970 there were 13. The decade of the 1930's had 7 record high temps in January. 1980's had 5 and 2000's had 5. I would agree that the Globe is warming. I am not convinced it is not a natural cycle. I agree AGW does exist. My major question is to the amount. I am still doing active research at this time.
    0 0
    Moderator Response: Please comment on the relevant threads: Regarding weather in your own geographical area (or anybody else's local geographic area), or short periods of time, see It’s freaking cold!, and 1934 - hottest year on record, and 2009-2010 winter saw record cold spells, and Global temperatures dropped sharply in 2007. Regarding natural cycles, see Climate’s changed before, and It’s a 1500 year cycle, and It cooled mid-century, and It warmed before 1940 when CO2 was low.
  17. Re: Artful Dodger (58) Picked up a copy at Barnes and Noble in Green Bay (mile south of the "frozen tundra" of Lambeau Field). Will try to get on it soon, but am behind in previewing my advance copy of BPL's book on climate change (only half done). The Yooper
    0 0
  18. muoncounter@51: Ice melts from warming temps and also changes in albedo. The particulate load that China adds daily to the Arctic is nothing to sneeze at.
    0 0
  19. Rob@39: The route that the St Roch took was not sailed in the summer of 2010. The southerly route was sailed. One has to compare apples to apples. The Germans sailed the NE passage during WW2. In fact, the Russians have a robust set of ports on the NE passage today. There is a lot that we don't know about the Arctic and ice. Presently, Hudson Bay is very warm and is being fed by the Gulf Stream. The main thrust of my comments is for people to open their minds. Co2 potentially has caused some warming in the Arctic. There are lots of other explanations for the decline in ice as well. Let's try and understand all forces in this rather than only focusing on co2.
    0 0
  20. #17 Camburn at 05:16 AM on 8 November, 2010 And not least, is the tremendous amount of soot that China spews that lands in the Arctic. Yes. Here is an intercomparison of Annual total number of hours of Reduced Visibility observed at the Hong Kong Observatory and Annual Minimum Sea Ice Extent in the Arctic (reversed scale). The teleconnection between Chinese soot and Arctic melt is undeniable. Let me note it is possible to burn coal with no soot output while it is impossible to burn it without producing CO2. Eliminating black carbon emissions is not even prohibitively expensive. It is routinely done in Europe and to a somewhat lesser extent in the US of A. Some background material: JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, D04204, 2005 doi:10.1029/2004JD005296 Distant origins of Arctic black carbon: A Goddard Institute for Space Studies ModelE experiment Dorothy Koch and James Hansen "The (former) Soviet Union (FSU) was implicated as a major source of Arctic haze in many studies. Novakov et al. [2003] found that black carbon emissions from the FSU in the late 1990s was less than 1/4 their peak levels of 1980. European emissions are also about 1/3 their levels in the 1970s. However China and India have doubled their BC emissions since the late 1970s. Thus BC emissions are more heavily weighted toward south Asia than they were in the 1970s and 1980s, when many of the Arctic haze studies took place."
    0 0
  21. #68: "The particulate load that China adds daily to the Arctic" #70: "The teleconnection between Chinese soot and Arctic melt is undeniable." That this soot largely originates in the burning of coal is proof that anthropogenic input is real and of significant, measurable magnitude. If this soot is moving to the Arctic, so are the exhaust gases which are produced with the soot. To verify this conclusion, look at the significantly higher average annual CO2 concentrations in the Arctic: compare BRW, ALT, ICE, OSM, PAL, MBC, ZEP to MLO. Further verification comes from Fisher et al 2010, who traced combustion gases via CO (monoxide) monitoring using data from both aircraft and the AIRS satellite: We find that Asian anthropogenic emissions are the dominant source of Arctic CO pollution everywhere except in surface air where European anthropogenic emissions are of similar importance. So if soot, then CO and CO2. And that is melting Arctic ice.
    0 0
  22. James Hansen is well known for saying that controlling black carbon is one of the lowest hanging fruits in controlling AGW. For those who claim the IPCC goes only after CO2 this is a clear counter example of scientists trying to identify the cheapest fixes to go after first. That said, even with black carbon controlled, without controlling CO2 the ice will all melt out. We need to control as many sources of warming as possible.
    0 0
  23. Berényi Péter comparing summer ice extend to visibility in Hong Kong doesn't tell much about the causality between the two. Probably there's not. More relevant could be meaurements BC concentration in ice cores. It's in Central Greenland, not over the arctic ocean, but it clearly shows (fig 2a) that BC deposition there went through a quite large peak around 1910 and then declined. In the last decades, though, it's slowly increasing again, but still well below the peak.
    0 0
  24. #73: "doesn't tell much about the causality between the two." Hopper et al 1994 reiterate my point in #71 ... hourly black carbon data exhibited considerable episodic behaviour over periods of a few days to a week. These elevated concentrations of black carbon were most often correlated with increases in carbon dioxide and methane concentrations. Such correlations can arise from several causes, but transport of a polluted air mass from industrialized regions to the high Arctic would account for the simultaneous increases in numerous monitored constituents, and is consistent with previous studies of Arctic Haze. Black carbon is apparently a valid 'tracer' for carbon dioxide. BP in his considerable wisdom now strengthens the link between Arctic melt and atmospheric CO2. To take this one step further, black carbon transport is apparently affected by ocean oscillations. From Sharma et al 2006: The results revealed that EBC concentrations were 40% higher during the positive phase of the North Atlantic Oscillation than during the negative phase. The source contributions at the two sites were determined by using trajectory analysis techniques, which revealed that Alert came under the influence of Siberia/Europe transport while Barrow showed influence from Siberian and Pacific/Asian transport. This suggests the end of the 'its all because of ocean oscillations' tripe. The varying wind and weather associated with ocean oscillations are merely the agents that modify the transport of GHGs from anthropogenic sources to the Arctic.
    0 0
  25. muoncounter you should distinguish between BC absorption in the atmosphere and on the ice surface. I was referring to the latter which directly influences the ice melting.
    0 0
  26. #75: "distinguish between BC absorption in the atmosphere and on the ice surface." I'm suggesting that the presence of BC in the Arctic, traced to sources in Europe and Asia, is the key; not where the BC winds up once it is in the Arctic. With BC comes CO, CH4 and CO2 from fossil fuel and biomass burnings. The relative weight of melting due to GHG-induced warming vs. surface BC-induced heat retention isn't the question.
    0 0
  27. There is an updated link to the full version of Polyak et al 2010 http://www.cgd.ucar.edu/staff/mholland/papers/Polyak_2010_historyofseaiceArctic.pdf
    0 0

Prev  1  2  

You need to be logged in to post a comment. Login via the left margin or if you're new, register here.



The Consensus Project Website

THE ESCALATOR

(free to republish)


© Copyright 2020 John Cook
Home | Links | Translations | About Us | Privacy | Contact Us