Given the fluctuations in daily sea ice measurements, climatology typically relies on monthly averages. November daily extents are now fully reported and the results can be compared with years of the previous decade.
MASIE showed 2017 reached 9.7M km2, 0.2M below the 9.9M November 10 year average. SII was slightly lower at 9.5M for the month. The 10 year average for SII is about 200k km2 lower than MASIE, with a similar differential appearing in 2017.
In either case, one can easily see the Arctic ice extents have not declined in the last decade. MASIE shows 2017 matching 2007, higher than 2012 by 200k km2, and 844k km2 more than 2016.
Sea Ice Index statistics are from recently released SIIv.3.0, as reported in Sea Ice Index Updates to v.3.0.
The graph below shows November comparisons through day 334 (Nov. 30).
Note that 2017 in both MASIE and SII tracked the 10-year average, slightly lower throughout. SII is now about 240k km2 less than MASIE. 2012 grew strongly to approach the 10-year average, recovering after being decimated by the August Great Arctic Cyclone. 2007 lags behind and the lackluster 2016 recovery is also evident.
The narrative from activist ice watchers is along these lines: 2017 minimum was not especially low, but it is very thin. “The Arctic is on thin ice.” They are basing that notion on PIOMAS, a model-based estimate of ice volumes, combining extents with estimated thickness. That technology is not mature, with only a decade or so of remote sensing. The image below from AARI shows widespread thick ice at end of November 2017.
The formation of ice this year shows solid concentrations in the central Arctic. Watch the November refreezing of Arctic marginal seas from the center outward.
At the top, open water in Chukchi is shrinking while neighboring Beaufort and East Siberian seas freeze completely. On the left, Hudson Bay starts with fast ice on the western shore, now growing extent strongly. On the right, Kara ice cover is 90% complete.
The table shows ice extents in the regions for 2017, 10-year averages and 2016 for day 334. Decadal averages refer to 2007 through 2016 inclusive.
NH extent is close to average with the only large deficit in Chukchi. Most seas are nearly average with a large surplus of Hudson offsetting Chukchi. Both seas are now refreezing strongly.
Earlier observations showed that Arctic ice extents were low in the 1940s, grew thereafter up to a peak in 1977, before declining. That decline was gentle until 1994 which started a decade of multi-year ice loss through the Fram Strait.
There was also a major earthquake under the north pole in that period. In any case, the effects and the decline ceased in 2007, 30 years after the previous peak. Now we have a plateau in ice extents, which could be the precursor of a growing phase of the quasi-60 year Arctic ice oscillation.
Background on MASIE Data Sources
MASIE reports are generated by National Ice Center from the Interactive Multisensor Snow and Ice Mapping System (IMS). From the documentation, the multiple sources feeding IMS are:
Platform(s) AQUA, DMSP, DMSP 5D-3/F17, GOES-10, GOES-11, GOES-13, GOES-9, METEOSAT, MSG, MTSAT-1R, MTSAT-2, NOAA-14, NOAA-15, NOAA-16, NOAA-17, NOAA-18, NOAA-N, RADARSAT-2, SUOMI-NPP, TERRA
Sensor(s): AMSU-A, ATMS, AVHRR, GOES I-M IMAGER, MODIS, MTSAT 1R Imager, MTSAT 2 Imager, MVIRI, SAR, SEVIRI, SSM/I, SSMIS, VIIRS
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