Unique Arctic Sea Ice Plots
Posted by Jeff Condon on September 23, 2009
I’ve done some improvement on my Sea Ice plots. I’ve included several graphs I haven’t seen before one of which was the ratio of extent and area suggested by Crashex on the last thread. The plots reveal some interesting and unique aspects of sea ice, and the last two graphs seem to be in opposition to the conclusion that sea ice is melting due to global warming and supportive of a weather pattern change.
This version used some smart filtering to remove points with jumps greater than 100,000km^2 in one day, an improved filtering with a wider window and some other minor improvements. I’ve plotted the data several different ways but I want to start with the improved area and extent value and anomaly plots. I’ve corrected the area plots by adding the satellite hole area in at 100% using only the larger hole from the first satellites so as to not bias the data.
You can see my plot is a near exact match for the Cryosphere version HERE.
Extent is calculated as all pixels with areas greater than 15% of the pixel.
You can see most of the big spikes have been removed. Still no significance levels Kenneth, it will take a bit more time.
There are still a few small downward spikes not removed by the 100,000km^2 threshold but the curve is much cleaner. The next graph is a plot of all years overlayed on the average curve displayed in the background. I should mention that all anomalies were calculated over the full length of the data.
It was interesting that I had area (not extent) of 2008 basically equal to the 2007 minimum.
This is the more familiar extent curve with all NSIDC years plotted. An interesting detail is that the curent extent by NSIDC isn’t higher than 2005 as Jaxa reports. (see where the black line endpoint almost reaches the closest curve directly above it – 2005) I’m interested in this because our current satellite NOAA17 is different from the one used in 2005 which was NOAA13. I believe all of JAXA’s data is from a single satellite and it has what is apparently a higher value for ice levels today than at the same time in 2005. It could be a calibration difference during satellite transitions causing the current years to appear slightly lower in ice levels.
The next plot is Area vs Extent to see if there is a pattern in the annual signal.
The greater than 1 slope means Extent changes just slightly faster than area. The next plot was requested by Crashex.
I think it shows some interesting trends in the recent years. Where the graph dips is during the summer months and the top values are where the ice packs out the entire ocean in the winter months. I removed the annual anomaly signal and replotted in the next graph.
Then I decided to look at the days at which the ice minimums and maximums occurred. These are not official values and should be determined using heavily filtered data so there is some noise but this is right from the data. If warming were the cause of ice melting rather than weather patterns we would expect the minimum to happen later each year. This meant that if there was a strong trend towards earlier in the year warming wouldn’t be the cause. If it were to shift later in the year over time, either possibility is valid.
Also, it would be reasonable to expect the winter maximum to shift earlier in the year as the higher temperatures would limit ice formation to occur sooner in the season. If it were only weather patterns the shift could be either direction.
Wow, that’s a pretty clear uptrend in both graphs. The first wouldn’t survive any trend significance test WRT weather noise but the second might be on the edge. We cannot eliminate temperature as the cause of these curves. What do the maximum’s show
This was a little surprising also, the area maximums show more variation than the minimums. There isn’t any clear shifting of the maximum date to earlier in the season though as we would expect if warming were the culprit.
Ok, the strongest trend recorded is from the winter version of the Extent maximums and it’s positive. Again I doubt this trend meets significance compared to the “weather noise” but consider that it is strongly positive meaning that the maximum ice value shifts later in the year by almost 2 days every five years, this is the opposite of what I would expect if ice levels were being reduced by global warming rather than a weather pattern change.
I don’t know where to find official figures on this so it needs confirmation and some improvement in locating an exact minimum but the minimum value in this data is shifting in the opposite direction from what would be expected due to global warming.