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Jim Hunt

Thanks for the mention Neven.

Here's the latest post cyclone AMSR2 sea ice concentration map:

plus a sea ice drift animation:




The January graph for Arctic Sea Ice Extent is very dynamic. I pose the thought that that is one to watch very carefully for trends...


Nevertheless, these short-term effects may be just enough to nudge Global Sea Ice Extent to yet another record low minimum (although Antarctic sea ice also has a say in this, of course):

I'm going to check the numbers tomorrow, but it looks like the record for lowest Global SIE minimum has been broken (yet again):



Is it just me or do others not understand figure 4 from the latest NSIDC update?

Jim Hunt

AMSR2 derived Arctic sea ice extent is still decreasing following the recent cyclone:

However Arctic sea ice area has started to increase once again:


Meanwhile global sea ice extent is most certainly in "lowest in the satellite era" territory:


So, Jim, being conservative I could think about comparing the 16 million square km figure to, say, an 18 million square km figure and be able to say that over 30 years the global sea ice extent has 'definitely' gone down 10%?

Al Rodger

Jim Hunt,
It's interesting that JAXA plot their data with 2018 a lot less icy than 2017 (only six days that are not a new record level in Jan & one day in February. Bar those seven days this freeze season has been record-breaking since 27 Dec. Yet Hamburg are showing it far more of a dance between the two. That the two sources of SIE should differ by that margin isn't such a surprise except you label the Hamburg data JAXA/Hamburg.

Jim Hunt

Al - The raw AMSR2 data comes from JAXA, but the University of Hamburg process it differently to the Japanese National Institute of Polar Research when calculating sea ice concentration. The former uses the "ARTIST sea ice" algorithm (ASI for short). The latter is commonly referred to as "JAXA extent", and uses the NASA "bootstrap" algorithm.

Al Rodger

So the difference between the Hamburg record & the JAXA record shows algorithm choice can have quite substantial effects. Hamburg plot 2018 far closer to 2017 than that seem at NOAA ChArctic which in turn are just a little closer to Hamburg than the two years plotted by JAXA. Yet JAXA & Hamburg differ only in the algorithm. And there is also a difference in the absolute values although the big difference we cannot lay at the door of the algorithm choice. (Consider Feb 5th - NOAA 13.9, JAXA 13.3, Hamburg 13.0)

However, the different records would thus give different answers if you use the SIE at the start of the year to predict the daily maximum of the year.

As I follow JAXA I see today the daily SIE for 2018 running 600k below the daily maximum of 2017 but as a predictor the average daily SIE through 2018 (Jan1-Feb12) is 120k sq km below the equivalent 2017 value. This Jan1-Feb12 data appears a reasonable predictor for the maximum daily value of the year. Over the last 15 years this measure has only twice underestimated the maximum but more than 100k sq km (although substantially so - 280k & 180k) and has far more often overestimated it.

So, always game for a laugh, a projection of a 2018 record maximum daily JAXA SIE of 13,755,000(+/-100,000) sq km.

Al Rodger

I was going to link to my graphic of JAXA SIE anomalies (usually 2 clicks to 'download your attachment')

Robert S

At a purely anecdotal level, over the past couple of years I'm noticing what looks like a move of the pole of cold from the Siberian side of the AO to the CAA/Greenland. This may be related to some of the other patterns we're seeing that are impacting the ice. I'll have to do some data analysis once spring is really here...

Susan Anderson

Robert S, I think I first heard that idea some years ago, and it certainly seems to be evident in reality.

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