the Air Vent

Because the world needs another opinion

Sea Ice Update

Posted by Jeff Id on September 21, 2009

Arctic sea ice crossed over and exceeded the 2005 level on Sept 20.

Sea ice extent is plotted using AMSR-E data at the IJIS website with the following values.

2009 5383594 km^2 and 2005 was 5345156.

AMSR-E Sea Ice Extent

Sea ice has officially reached its minimum in the Arctic continuing its recovery from the 2007 minimum. In the Antarctic the ice levels continue to grow. I’ve calculated the ice area anomalies (not extent) from the raw NSIDC data myself here. This data is slightly different from my previous work as the NSIDC has updated 2008 to use the NOAA17 data instead of the failed 15 and 13 satellites.

North Ice anomaly2

South Ice Anomaly

Global Ice anomaly

And of course my favorite, global sea ice offset to show the actual size of the melting in relation to the average sea ice on earth. Tamino’s crowd loves this one. My average area is slightly low as the Arctic satellite hole is not added in.

Global Ice anomaly from average

Global sea ice anomaly - offset to show total sea ice. Click for full size.

Since they also love to criticize me for even showing global sea ice, HERE is a link to the Cryosphere graph where the pro’s also calculate the global sea ice anomaly with very similar results.

22 Responses to “Sea Ice Update”

  1. Jeff Id said

    Natural variation?

  2. timetochooseagain said

    Why does your Antarctic drop off at the end?

    By the way, considering that some have bizzarely asserted that there isn’t any global trend at all, I find objections to you showing that there is one rather odd…

  3. DeWitt Payne said

    It looks like there are a couple of glitches in the recent record (2007-2009) and one in about 1988. There’s a chunk of data missing from December 1987 to January 1988. That could easily cause an anomaly glitch. Are there similar missing data in 2007-2009?

  4. Jeff Id said

    I think it must be a corrupted file or something in 1988 I figured out which days were giving the bad values but didn’t have time to do much more than that.

    From 08 to present I used the near realtime data which is NOAA17. The signal is much cleaner than before but hasn’t been processed for final acceptance yet. I’m not sure if the official curves have this processing done real time but unpublished or if they just filter it. This version has a 7 day square filter with truncated endpoints.

  5. Mark Stewart said

    What happens in June that causes that distinctive blip in most years?

  6. Peter Plail said

    Seems like Cryosphere have taken umbridge at your posting the final link. It isn’t working at the moment

  7. Jeff Id said

    It works for me.

  8. Jeff Id said

    #5 It’s an annual correction of a known amount. People always ask about it but it doesn’t bother me.

  9. Kenneth Fritsch said

    Jeff ID, you need to put a +/- SE on those slope values.

  10. PaulM said

    Jeff, I’m also puzzled by the latest sharp downspike in your Antarctic graph. According to Cryosphere, the S hemisphere ice anomaly is currently +ve.

  11. Jeff Id said

    #10, Cryosphere has this for the Arctic

  12. Jeff Id said

    And this for the Antarctic

    I think the little spike near the end is just noise in the data. It probably jumps too far to be real.

  13. Crashex said

    Visually comparing the recent ice plots on CT with the historic data suggests that the current area has more coverage at 95-100% than any of the recent prior years–at least all that I checked. The size of the region with near 100% coverage changes each year. With the theory that a larger mass is more difficult to accelerate, you would expect less transport of the ice out of the arctic zone as the 100% mass gets larger.

    Since you have all the extent and area data, could you plot the ratio of those values for the available time frame to see how that “effective density” trends over that time.

    I’m just curious, but don’t have the computer skills to figure out how to download the info.

  14. John F. Pittman said

    There is an interesting side to all of this. With 2009 on track to be similar to 2005, and assuming the fears of “baby” ice being thinner meant faster melt were correct, if temperatures do not increase, one would expect a greater recovery for 2009 to spring 2010 than 2008 fall to 2009 winter.

    I think that someone is about to be hoist on their own petard, or simply shown to be another AGW retard blowing smoke up people’s skirts.

  15. DeWitt Payne said


    Is this graph the sort of thing you’re looking for? This is Cryosphere Today Arctic Area divided by JAXA extent. The average value is the 1979-2000 average daily area from CT divided by the 1979-2000 NSIDC average daily extent scaled to JAXA. The different algorithms used by the different agencies produce data at different scales. It’s usually possible to do a linear transform between the different data sets, though. Uni-Hamburg area and extent numbers, which uses AMSR-E data, has a much higher minimum concentration


    Can you post a link to the NSIDC data. I forgot to bookmark it. I have the data through 2006 but not the near real time data. I could probably find it again, but there are so many different directories with different sorts of data, I don’t really want to go crawling through it again.

  16. Jeff Id said


    Happy to provide the link. The readme file has links to the data description. This is a nightmare link to find which is I suppose the point of it. They don’t want everyone downloading several gb of data.

    If you want help getting into it, let me know.

  17. BarryW said

    Another way of looking at the data. The max values are back to the about the pre 2005 levels.

  18. Jeff Id said

    #17, I think it’s more than that. The recovery in anomaly has been fairly dramatic. The reason it has been so strong is because the ice loss of 07 was driven by weather patterns rather than warming air. That’s one of the reasons I consider this a recovery from previous levels. Also, the amount of multi-year sea ice is certain to go up again. The whole thing seems like a cycle to me.

  19. MikeN said

    No, there’s going to be a low value of 3 year ice, and a substantial drop in freezing(new ice).

  20. Crashex said

    Dewitt Payne:

    Yes that’s the plot I was asking about. Thanks.

    The values surprised me. Comparing the CT plots I would not estimate that 2006 has a higher average density than 2009. The CT SMI data plots show too much light magenta (80%) and a much larger red and yellow ring at the perimeter.

    Sorry, don’t know how to show the plots here. I just use the Compare Dates link at CT and assign the dates to be sept X 2009 and sept x 2006.

  21. Crashex said

    Does this work to display the CT color plots.
    Visually integrating, I ask myself.
    Which plot has more red?
    Which plot has more light magenta?
    Which plot has more dark 100% area?

    Why doesn’t the 2009 plot indicate a greater “density” value than the 2006 plot?

  22. Sera said

    An interesting read on icebreakers

    Maybe the icebreakers are creating faults that allow the ice to move via wind patterns, rather than creating the normal blockages. The routes are posted on page two.

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