Overachieving September Arctic Ice

September daily extents are now fully reported and the 2017 September monthly results can be compared with years of the previous decade.  MASIE showed 2017 exceeded 4.8M km2  and SII was close behind, also reaching 4.8M for the month.  The 11 year linear trend is more upward for MASIE, mainly due to 2008 and 2009 reported higher in SII.  In either case, one can easily see the Arctic ice extents since 2007 have not declined and are now 500k km2 higher.

In August, 4.5M km2 was the median estimate of the September monthly average extent from the SIPN (Sea Ice Prediction Network) who use the reports from SII (Sea Ice Index), the NASA team satellite product from passive microwave sensors.

The graph below shows September comparisons through day 273 (Sept. 30).Note that starting day 260 2016 had begun its remarkable recovery, and is now well above the 10 year average, nearly matching 2017. Meanwhile 2007 is 1.1M km2 behind and the Great Arctic Cyclone year of 2012 is 1.4M km2 less than 2017.  Note also that SII is currently matching MASIE.

The narrative from activist ice watchers is along these lines:  2017 minimum is 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, and in any case refers to the satellite era baseline, which began in 1979.

The formation of ice this year does not appear thin, since it is concentrated in the central Arctic.  For example, Consider how Laptev and East Siberian seas together added 180k km2 in the just the last ten days:

Click on image to enlarge.

The table shows ice extents in the regions for 2017, 10 year averages and 2007 for day 273. Decadal averages refer to 2007 through 2016 inclusive.

Region 2017273 Day 273
2017-Ave. 2007273 2017-2007
 (0) Northern_Hemisphere 5200394 4944703 255690 4086883 1113511
 (1) Beaufort_Sea 397521 540936 -143415 498743 -101222
 (2) Chukchi_Sea 141983 217113 -75130 51 141932
 (3) East_Siberian_Sea 369289 326398 42891 311 368978
 (4) Laptev_Sea 377166 166604 210562 235245 141922
 (5) Kara_Sea 46667 28503 18164 15367 31300
 (6) Barents_Sea 2010 20562 -18552 4851 -2841
 (7) Greenland_Sea 134724 245771 -111046 353210 -218486
 (8) Baffin_Bay_Gulf_of_St._Lawrence 85755 48614 37141 42247 43508
 (9) Canadian_Archipelago 498801 356144 142657 307135 191666
 (10) Hudson_Bay 1621 4741 -3121 1936 -316
 (11) Central_Arctic 3143698 2988219 155479 2626511 517187

Deficits in Beaufort and Chukchi are more than offset by surpluses in East Siberian and Laptev. Kara and Barents together are average.  Greenland Sea is down but note the strong surpluses in Canadian Archipelago and the Central Arctic, which is already at 95% of its March maximum.


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.

For context, note that the average maximum has been 15M, so on average the extent shrinks to 30% of the March high before growing back the following winter.  In 2017 about 33% of the March maximum was retained, so the melt season losses were considerably less than in the past.

Background from Sept. 20

Dave Burton asked a great question in his previous comment, and triggered this response:

Dave, thanks for asking a great question. All queries are good, but a great one forces me to dig and learn something new, in this case a more detailed knowledge of what goes into MASIE reports.

You asked, where do they get their data? The answer is primarily from NIC’s Interactive Multisensor Snow and Ice Mapping System (IMS). From the documentation, the multiple sources feeding IMS are:



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




  1. Hifast · 16 Days Ago

    Reblogged this on Climate Collections.


  2. angech · 15 Days Ago

    Have a question on multi year ice.will get back when have time.


    • Ron Clutz · 10 Days Ago

      angech, looks like you are busy. Not knowing your exact question, I will comment anyway. Multi-year ice is used as a proxy for ice volume, which is extent times thickness.

      In the post above I overstated the length of the remote sensing record of Arctic ice thickness. In fact it is only a decade or so; moreover PIOMAS is not a dataset, but a model producing volume estimates. This paper explains the difficulties:
      Uncertainties in Arctic sea ice thickness and volume: new estimates and implications for trends,
      M. Zygmuntowska et al.,Nansen Environmental and Remote Sensing Center, Bergen, Norway

      “Sea ice thickness is a quantity that cannot be measured directly by satellite-based instruments. Altimeters on board satellites measure the elevation of the Earth’s surface, and by identifying leads between the ice floes, the freeboard (the height of the ice above the water level) can be derived. The thickness is calculated by assuming hydrostatic equilibrium and estimating the density of sea ice and snow and the snow depth on top of the ice. These quantities may vary both in space and time and introduce large uncertainties in the sea ice thickness estimates.

      “We show that the mean sea ice thickness is strongly influenced by the choice of sea ice density, while the trend and the annual cycle are hardly affected. The resulting mean values in October/November range between 1.39 and 2.00 m. At the end of winter, in February/March sea ice thickness has increased and ranges between 1.53 and 2.20 m. Because the influence of sea ice density increases with sea ice thickness, we found the range to be smaller for FYI (about 55 cm), and larger for MYI (about 80 cm).

      “A bias in sea ice thickness as a measure of uncertainty that propagates into the estimates of uncertainty in sea ice volume has been previously used to assess uncertainties in modelled Arctic sea ice volume with PIOMAS (Schweiger et al., 2011). This is comparable to the uncertainties in our studies, and the resulting uncertainties in sea ice volume of 6.3 % in spring and 10 % in autumn are of the same order (14 and 12.7 % in our study for the two seasons, respectively).

      “We find large uncertainties in the total sea ice volume and trend. The mean total sea ice volume is 10120±1280 km3 in October/November and 13250 ± 1860 km3 in February/March for the time period 2005–2007. Based on these uncertainties we obtain trends in sea ice volume of −1450 ± 530 km3 a −1 in October/November and −880 ± 260 km3 a −1 in February/March over the ICESat period (2003–2008). Our results indicate that, taking into account the uncertainties, the decline in sea ice volume in the Arctic between the ICESat (2003–2008) and CryoSat-2 (2010–2012) periods may have been less dramatic than reported in previous studies.

      “However, final quantitative conclusions about a change in sea ice volume are hard to make, considering the large uncertainties and unresolved biases found in our study.”


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  4. oldbrew · 15 Days Ago

    Ask Pen Hadow whether this year’s Arctic sea ice was thick or thin. 😊



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  6. Bruce C. Atwood · 11 Days Ago

    see the real data here; http://nsidc.org/arcticseaicenews/


    • Ron Clutz · 11 Days Ago

      Bruce, all the data in my post are real and come from the same place.


  7. Gary Brunner · 11 Days Ago
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  9. Pingback: Arctic sea ice—shrinking due to manmade global warming? | Earth Rising - An Alternative Environmental Commentary
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