2017: August Report from Sea Ice Prediction Network

For the August Report there were 37 contributions with the median Outlook value for September 2017 Arctic sea ice extent of 4.5 million square kilometers with quartiles of 4.2 and 4.8 million square kilometers (See Figure 1 in the Overview section, below). These values are unchanged from the July Report, which is consistent with the moderating impact of summer 2017 Arctic weather. The range is 3.1 to 5.5 million square kilometers in August, unchanged from the July Outlook. To place this Outlook in context, recently observed values were 4.3 million square kilometers in 2007, 3.6 million square kilometers in 2012, and 4.7 million square kilometers in 2016. 

These are predictions for the September 2017 monthly average ice extent as reported by NOAA Sea Ice Index (SII). This post provides a look at the 2017 Year To Date (YTD) based on monthly averages comparing MASIE and SII datasets. (10 year average is 2007 to 2016 inclusive)

The graph puts 2017 into recent historical perspective. Note how 2017 was below the 10-year average for the first 4 months, then recovered to match average in May and has maintained average through August. The outlier 2012 provided the highest March maximum as well as the lowest September minimum, coinciding with the Great Arctic Cyclone that year.  2007 began the decade with the lowest minimum except for 2012.  SII 2017 is running below MASIE and is currently just below MASIE 2007 and 2012.

The table below provides the numbers for comparisons.

Monthly	2017	2017	2017	2017-10yr Ave	2017-10yr Ave	2017- 2007
Averages	MASIE	SII	SII Deficit	MASIE	SII	MASIE
Jan	13.503	13.174	-0.329	-0.418	-0.512	-0.259
Feb	14.478	14.112	-0.366	-0.363	-0.440	-0.173
Mar	14.509	14.273	-0.236	-0.544	-0.542	-0.114
Apr	13.941	13.760	-0.180	-0.412	-0.446	0.246
May	12.838	12.618	-0.220	0.075	-0.138	0.412
June	10.975	10.720	-0.255	0.069	-0.218	0.148
July	8.383	7.901	-0.482	0.024	-0.206	0.367
Aug	6.006	5.472	-0.533	0.051	-0.185	0.421

The first two columns are the 2017 YTD shown by MASIE and SII, with the SII deficits in column three.  The difference has doubled the last two months and averaged -325k km2 for the YTD. Column four shows MASIE 2017 compared to MASIE 10 year average, while column five shows SII 2017 compared to SII 10 year average.  YTD MASIE is -190k km2 to average and SII is -336k km2 to average.  The last column shows MASIE 2017 holding an August surplus of 421k km2 over 2007.  For the YTD 2017 is 131k km2 higher than 2007, overcoming this year’s deficits in the early months.

For more on SII versions 1 and 2 differences see Arctic Ice Uncertainties

Summary

The experts involved in SIPN are expecting SII 2017 September to be higher than 2007 and slightly lower than 2016.  The way MASIE is going, this September looks to go higher than 2016 unless some bad weather intervenes.

Footnote:

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

MASIE: “high-resolution, accurate charts of ice conditions”
Walt Meier, NSIDC, October 2015 article in Annals of Glaciology.