Given the fluctuations in daily sea ice measurements, climatology typically relies on monthly averages. October daily extents are now fully reported and the 2017 October monthly results can be compared with years of the previous decade. MASIE showed 2017 reached 6.8M km2, exceeding the 6.6M October 10 year average. SII was close behind at 6.7M for the month. The 11 year linear trend is more upward for MASIE, mainly due to early years, especially 2007 and 2008 reported higher in SII. In either case, one can easily see the Arctic ice extents have not declined; MASIE shows 2017 higher than 2016 by 800k km2, and more than 2007 by 1M km2.
Sea Ice Index statistics are from newly released SIIv.3.0, as reported in Sea Ice Index Updates to v.3.0.
The graph below shows October comparisons through day 304 (Oct. 31).
Note that 2017 in both MASIE and SII tracked the 10 year average, higher most of the month, and slipping behind toward the end. SII is now about 200k km2 less than MASIE. 2012 recovered strongly, doubling in extent after being decimated by the August Great Arctic Cyclone. 2007 shows a inexplicable one-day jump, taking it close to average. 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 formation of ice this year does not appear thin, since it is concentrated in the central Arctic. Watch the October refreezing of the Arctic from the center outward.
The table shows ice extents in the regions for 2017, 10 year averages and 2016 for day 304. Decadal averages refer to 2007 through 2016 inclusive.
NH extent is slightly below average due to deficits in Beaufort and Chukchi. East Siberian is growing while Laptev is maxed out. Other seas are around average except for Greenland Sea down, offset by Baffin Bay being up.
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
Summary: IMS Daily Northern Hemisphere Snow and Ice Analysis
The National Oceanic and Atmospheric Administration / National Environmental Satellite, Data, and Information Service (NOAA/NESDIS) has an extensive history of monitoring snow and ice coverage.Accurate monitoring of global snow/ice cover is a key component in the study of climate and global change as well as daily weather forecasting.
The Polar and Geostationary Operational Environmental Satellite programs (POES/GOES) operated by NESDIS provide invaluable visible and infrared spectral data in support of these efforts. Clear-sky imagery from both the POES and the GOES sensors show snow/ice boundaries very well; however, the visible and infrared techniques may suffer from persistent cloud cover near the snowline, making observations difficult (Ramsay, 1995). The microwave products (DMSP and AMSR-E) are unobstructed by clouds and thus can be used as another observational platform in most regions. Synthetic Aperture Radar (SAR) imagery also provides all-weather, near daily capacities to discriminate sea and lake ice. With several other derived snow/ice products of varying accuracy, such as those from NCEP and the NWS NOHRSC, it is highly desirable for analysts to be able to interactively compare and contrast the products so that a more accurate composite map can be produced.
The Satellite Analysis Branch (SAB) of NESDIS first began generating Northern Hemisphere Weekly Snow and Ice Cover analysis charts derived from the visible satellite imagery in November, 1966. The spatial and temporal resolutions of the analysis (190 km and 7 days, respectively) remained unchanged for the product’s 33-year lifespan.
As a result of increasing customer needs and expectations, it was decided that an efficient, interactive workstation application should be constructed which would enable SAB to produce snow/ice analyses at a higher resolution and on a daily basis (~25 km / 1024 x 1024 grid and once per day) using a consolidated array of new as well as existing satellite and surface imagery products. The Daily Northern Hemisphere Snow and Ice Cover chart has been produced since February, 1997 by SAB meteorologists on the IMS.
Another large resolution improvement began in early 2004, when improved technology allowed the SAB to begin creation of a daily ~4 km (6144×6144) grid. At this time, both the ~4 km and ~24 km products are available from NSIDC with a slight delay. Near real-time gridded data is available in ASCII format by request.
In March 2008, the product was migrated from SAB to the National Ice Center (NIC) of NESDIS. The production system and methodology was preserved during the migration. Improved access to DMSP, SAR, and modeled data sources is expected as a short-term from the migration, with longer term plans of twice daily production, GRIB2 output format, a Southern Hemisphere analysis, and an expanded suite of integrated snow and ice variable on horizon.
Some people unhappy with the higher amounts of ice extent shown by MASIE continue to claim that Sea Ice Index is the only dataset that can be used. This is false in fact and in logic. Why should anyone accept that the highest quality picture of ice day to day has no shelf life, that one year’s charts can not be compared with another year? Researchers do this, including Walt Meier in charge of Sea Ice Index. That said, I understand his interest in directing people to use his product rather than one he does not control. As I have said before:
MASIE is rigorous, reliable, serves as calibration for satellite products, and continues the long and honorable tradition of naval ice charting using modern technologies. More on this at my post Support MASIE Arctic Ice Dataset
via Science Matters
November 1, 2017 at 12:18PM