the Air Vent

Because the world needs another opinion

Comparison of Northern Hemisphere Perennial and Seasonal Sea Ice

Posted by Jeff Id on February 4, 2012

We have been looking at sea ice trends below the arctic circle at the request of Anthony Watts.  It is a curiosity of his that he’s been asking Walt Meier of the NSIDC to consider for some time.   I am a fan of the NSIDC because their data access is excellent and they answer questions very quickly and reasonably. This post is from the daily sea ice data as presented by the NSIDC on their FTP site.   It is several gigabytes so if you are serious, fileZilla is a good free software to facilitate download.

From the video’s produced, it is apparent that a lot of noisy data exists at the extreme lower edge of detection.   This data results in sea ice being detected in isolated squares of warm latitudes with no chance of having actual sea ice. The effect is visible in this video showing both poles through the history of satellite ice data.

You can see the great lakes around Michigan sparkle year round with sea ice detection noise yet we know that the beaches in July and August are 90F and and the only ice you will find would be in someones drink.bbSo the false detection at the low end of the microwave sensor range is a known factor.   Plotting the sea ice area outside of the circle above, we can see that the sea ice never quite hits zero.  It gets pretty close though.

It is interesting that the minimum value has a shift at about 1998.  Fluctuations in the minimums don’t seem to have much trend so I assume the effect is instrument related.  There are a number of different instruments on different satellites which have been combined to create this trend.

There is a statistically signficant trend in the sea ice outside of the arctic circle.  This ice is completely melting as expected every year so the trend we see is a result of reduced formation.  I’m curious now what percentage of this new formation is in the open sea vs landlocked lakes but that will be a subject for a future post.

The Arctic trend shown next is comprised of everything above the arctic circle.

The trend is also significantly negative.

For confirmation of the above, these results differ very little from the UIUC cryosphere page.  UIUC does infill the pole hole with estimated data whereas I simply leave it out.  The pole hole is the region around the pole where the satellite instruments do not reach.  This region changed size early in the record leaving some difficult choices as to how to handle the newly available data.  I simply used the large mask throughout the record when creating trends. My trend may be slightly more negative than theirs due to the difference but the fractional differences are very small.

The purpose behind some of this work was to determine what percentage of the above trend is seasonal ice unrelated to polar cap melt.  Taking 152000km^2/decade of seasonal ice out of the 518000km^2 total, that amounts to 29% of the melt trend is due to ice which, in the last 34 years, is completely seasonal in nature.  Arctic circle ice also melts every year so it is a mix of seasonal and perennial (multi-year) ice.  The ratio of the seasonal ice 152000 to the mixed seasonal/multiyear ice 366000 is 41% – not sure what use that is but it is interesting to consider that the multi-year ice loss is quite a bit less than these graphs show.

This next graph requires some interpretation.  It is a ratio of the seasonal ice area outside the Arctic circle to the ice inside the Arctic circle.

In looking at this plot, I read it by observing the annual peaks only.  There is a visibly evident trend in the peak values each year.  This means that the peak seasonal ice is decreasing at a higher rate than the perennial Arctic peak ice.  This seems to be a confirmation of gradual warming processes controlling the peak amount as we would expect the southerly ice to show the effects first.  One problem with this graph is that it reads near zero during the time of greatest melting so we really only have good information at the peaks.

More work needs to be done.  The next thing I want to do is look at landlocked ice to see if there are trends in satellite detection ability.  After that, I have some new ideas to isolate whether the 2007 and 2010 arctic minimums were localized effects caused by ocean currents or if they were larger in scope.

My focus on this now is because the data is interesting and extensive and I haven’t seen much work done on regional effects in blogland.  I am very much skeptical that we should be worried about any of this.  If you add up all the sea ice in the world, we have a heck of a lot of it at any given time.  About 19million Km^2 on average.  If you take the global anomaly and offset it by the average amount, it gives a good idea what the sea ice death spiral is working out to be.

This data was compiled from the daily Ease grid files presented by the NSIDC.  Code for this post his here. ice code Save it and change the extension to R as WordPress won’t allow upload of text or R files.   It is written in several sections: functions, Northern hemisphere ice, Southern hemisphere ice, plotting calls etc. Authors of the various parts include RomanM, RyanO, Nic, Steve McIntyre and myself. Nearly all of their work has been modified so many times by me they may not recognize it but still deserve credit for the good parts.  Any errors are my own.

28 Responses to “Comparison of Northern Hemisphere Perennial and Seasonal Sea Ice”

  1. kakatoa said

    “If you take the global anomaly and offset it by the average amount, it gives a good idea what the sea ice death spiral is working out to be.”

    The Global Sea Ice Area Anomaly (with offset) graph certainly looks pretty flat! Looked at from a global perspective it doesn’t appear that Sea Ice Area has been affected much over the last 30+ years.

    Thanks all the effort that went into generating the graph.

  2. jstults said

    It might be easier to share your R code with gist; syntax high-lighting, embedding, forking, etc.

  3. jstults said

    Here’s your ice-code script.

  4. Matthew W said

    “The purpose behind some of this work was to determine what percentage of the above trend is seasonal ice unrelated to polar cap melt.”

    This hasn’t been done yet by the professional climate scientists, including Walt Meir ?

    I could only guess that if there wasn’t a significant amount, the alarmistas would ignore it.

  5. Kevin O'Neill said

    There are several scientific analyses of the Great Lakes winter ice cover; these all reach the same conclusions. Temporal and spatial variability of Great Lakes ice cover, Wang et al 2011, is one example. In it the authors write,

    There was a significant downward trend in ice coverage from 1973 to the present for all the lakes, with Lake Ontario having the largest, and Lakes Erie and St. Clair having the smallest. The translated total loss in lake ice over the entire 38-year record varies from 37% in Lake St. Clair (least) to 88% in Lake Ontario (most). The total loss for overall Great Lakes ice coverage is 71%, while Lake Superior places second with a 79% loss.

  6. anon2nz said

    What is the significance of the marked step change in the second graph (the one labeled “Arctic sea ice area anomoly beloww the arctic circle”)

    Is the step change in c1995 instrumentation or is it “real”?

    It does seem strange to put a sloped line across what seems to be two almost flat lines with a step change.

    Margaret

  7. Jeff Condon said

    Margaret,

    If you have a descending anomaly, you would expect this sort of plot to cross zero at about the middle. It may be nothing but I don’t know.

  8. Brian H said

    The data Kevin quotes on the Great Lakes suggest that they are the most sensitive indicator. If a cooling trend develops, the first ice-dicator might well be there.

  9. Paul Linsay said

    When I was a boy growing up in Cleveland, Lake Erie used to freeze solid and people could drive way out in a car. Maybe even all the way to Toronto? That was in the days when the Cuyahoga River was a fire hazard.

  10. Bruce said

    1995. Cosmic Ray lag?

    http://helios.izmiran.rssi.ru/cosray/months.htm

  11. Neven said

    My focus on this now is because the data is interesting and extensive and I haven’t seen much work done on regional effects in blogland. I am very much skeptical that we should be worried about any of this. If you add up all the sea ice in the world, we have a heck of a lot of it at any given time. About 19million Km^2 on average. If you take the global anomaly and offset it by the average amount, it gives a good idea what the sea ice death spiral is working out to be.

    IMO it’s not about the sea ice per se, but about the role it plays on the level of atmospheric patterns. If it largely disappears in one place, say the Arctic, this will probably have unpredictable effects on NH atmospheric patterns (never mind the albedo feedback). That the loss of summer sea ice in the Arctic is compensated by the amount of winter sea ice in the Antarctic doesn’t alter this. It’s like saying it doesn’t matter that one billion people are suffering from hunger, because one billion people are obese.

    I hope this makes sense.

  12. steveta_uk said

    There are flickerings of ice round the coast of Britain, particularly in the early years (1970’s) but not round the coast of Iceland or Norway, which seems very odd.

    I mean, we never have sea ice around Britain.

    Or so I thought, until today: http://www.bbc.co.uk/news/uk-england-dorset-16889200

  13. Jeff Condon said

    Neven,

    “I hope this makes sense.”

    Non-sequitor, unrelated, uncorrelated all of that is a sensible comment. Sensible has a different definition from ‘correct’ though. What is not sensible at this point, is to reject the possibility of a polar cycle. Magnetic field changes, solar winds, who knows but the poles do have different field polarity, angle to the sun etc. It is difficult to conceive that the global warming effect alone would cause one pole’s ice to increase and the other to decrease. So it also seems sensible to me that there is more to the story than mankind destroying the sea ice in the north. Perhaps we can better determine the NET effect of global warming looking at all of the ice on the globe rather than a single pole.

    Modelers like to reject this possibility – in my opinion because they prefer the alarm. However, even the UIUC calculates the global trend (real scientists, not just published engineers), they just don’t offset it by the mean ice level like I did so people can have a true sense of the magnitude.

    It is also difficult to compare a bit of ice melting with an analogy of a billion starving people but I understand where people imagine we are at.

  14. Neven said

    It is difficult to conceive that the global warming effect alone would cause one pole’s ice to increase and the other to decrease.

    It becomes less difficult to conceive once you realize the differences between the two poles.

    It is also difficult to compare a bit of ice melting with an analogy of a billion starving people but I understand where people imagine we are at.

    Again: that ‘bit of ice melting’ in the North could have unpredictable effects on atmospheric patterns on the Northern Hemisphere (there already is quite a bit of speculation on that score in the literature). It also has an effect on albedo. Whether it is compensated by sea ice in the South is of no relevance or consequence. The analogy with starving vs obese people had nothing to do with severity of the problem (as we don’t know what the potential consequences are), but with the irrelevance of your remark wrt what makes Arctic sea ice decrease important.

    If what I say, makes no sense, it’s probably better if I leave it at that and let other readers be the judge.

  15. Jeff Condon said

    Neven,

    What you said before makes sense but that is different from correct as I have pointed out.

    “It becomes less difficult to conceive once you realize the differences between the two poles.”

    I have read on this subject a bit as you might imagine. I wonder if you can put the ‘difference’ into words from your perspective. I am certain that you are far too quick to disregard my comment as irrelevant. Certainly there have been much scarier scenarios painted for the North than the South but frankly, all of it is a bunch of guesses by people who in aggregate have shown a propensity to exaggerate the pending doom of a small amount of warming.

    Polar bear doom, Plague, Death spiral etc…

    Not very scary to a calmer person.

  16. Neven said

    I wonder if you can put the ‘difference’ into words from your perspective.

    The biggest difference of course is that one pole is surrounded by land, and the other by sea.

    Not very scary to a calmer person.

    But not to be entirely dismissed either, eh?🙂

  17. Jeff Condon said

    “But not to be entirely dismissed either, eh?”

    Nope.

  18. Carrick said

    One of the most obvious changes is the increase in open water along the coastline of Greenland. This is expected to lead to an acceleration in melting of the glaciers in the fjords, but also lead to an increase in precipitation (and additional accumulation) at higher inland locations.

    Another is an shift to later freezing and thawing of the sea ice leads to a shift in early winter (later freezing) and early spring (early thawing) weather.

    I think the models lack the fidelity to be able to say what will happen if (as is likely) this trend for lost ice continues.

    It’d be interesting to look and see what the ZOD looks like here. I haven’t even had time to open any of the PDFs up.

  19. Nice work. At some point i’ll have to show you how to use raster.

  20. Jeff Condon said

    Steven,

    Do you know the memory limitations for a raster brick? It would be really nice to load the whole thing into memory at one time.

  21. Bruce said

    Neven: “It also has an effect on albedo”

    Actually, albedo dropped from 1985 to 1998 and then rose again according to the Earthshine project.

    http://wattsupwiththat.com/2007/10/17/earths-albedo-tells-a-interesting-story/

  22. jeff,

    raster is designed to be memory safe. That is, it will bring data into memory if it can. Otherwise, the data stays in the file and you
    work on the data in the file. So it will depend upon your system. see memory.size() and memory.limits() commands in R.
    my system is a 4gb system.

    if you want to stick with matrices , then you might look at bigmemory matrices ( there is a package) this gives you a filebacked
    matrix. I havent played with it yet, but the BEST data is bring my system to its knees which means a bigger system or
    swicth to filebacked objects.

    A bunch of people in climate studies are using raster now and even some polar guys. ice data has been popping up on the
    geoSig list (help questions dedicated to geo stats )

    If you have any issues, a bunch of r guys hang out on the help list and will answer your questions/fix
    bugs and such.

  23. Brian H said

    So, you use raster to master vaster files faster?

    Sorry. I’ll be quiet now.
    ;p

  24. steven mosher said

    haha. .

  25. Jeff

    Nice article. Taken in total ice levels seem nothing to worry about.

    On another topic, no doubt all at the Id household will be holding a Dickens celebratory dinner tonight to celebrate the 200th anniversary of his birth?

    So perhaps you will forgive me being off topic in referring to the article you kindly carried here where we looked at his life through the prism of an ever changing climate

    https://noconsensus.wordpress.com/2010/01/06/bah-humbug/

    Sorry for being OT
    tonyb

  26. Nice. Re Antarctic, especially in the earlier years of the animation, the last place that ice remains in summer is commonly adjacent to the Peninsula, often on both sides of it, but almost always on the East side of it. What would cause persistence in the sea ice adjacent to the land that was supposed to be warming anomalously? Easy answers are easy, but it’s trickier than easy, especially the West side story. I don’t know the answer. (BTW, I do not buy the hypothesis that volcanos have something to do with the postulated differential heating of the Peninsula).

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    […]Comparison of Northern Hemisphere Perennial and Seasonal Sea Ice « the Air Vent[…]…

  28. Brian H said

    Geoff Sherrington said
    February 10, 2012 at 3:21 am

    What would cause persistence in the sea ice adjacent to the land that was supposed to be warming anomalously?

    I wondered the same, but suspect it’s because that’s the (geographically determined) major outflow point for most of the big glaciers, so it’s like an ice river delta. In fact, the “persistence” is not persistence of the same ice, but fast replacement. Warming may even facilitate the “flow”.

    Since most build-up of ice depth occurs on the far side of Antarctica, there are also elevation issues, complicated by subsidence of the interior due to increasing mass.
    Interesting!

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