The graph above shows the monthly averages for September Arctic ice extents including 2023 compared to previous years back to 2007.  This year is slightly below the 17 year average of 4.63M km2;  MASIE shows 4.43M and SII shows 4.37.  For comparison the 2007 September values were 4.30M for MASIE and 4.27M for SII.  The predictions below refer to the SII value.

2023: August Report from Sea Ice Prediction Network

The August median forecasted value for pan-Arctic September sea-ice extent is 4.60 million square kilometers with interquartile values of 4.35 and 4.80 million square kilometers, while individual forecasts range from 2.88 to 5.47 million square kilometers. We note that the lowest two forecasts predict a new record September sea-ice extent value (current record is September 2012, with a sea-ice extent of 3.57 million square kilometers), but these forecasts are outliers relative to the other contributions.

These are predictions for the September 2023 monthly average ice extent as reported by NOAA Sea Ice Index (SII). This post provides a look at the 2023 Year To Date (YTD) based on monthly averages comparing MASIE and SII datasets. (17 year average is 2006 to 2022 inclusive).

The graph puts 2023 into recent historical perspective. Note how 2023 was slightly below the 17-year average for the first 5 months, then recovered to match average in May and has maintained or exceeded average through August. September was below average slightly and above 2007. 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 period with the lowest minimum except for 2012.  SII 2023 was running below MASIE except for May/June and is currently just below MASIE and above 2007 and 2012.

The table below provides the numbers for comparisons (all are M km2)

Monthly	MASIE 2023	SII 2023	MASIE -SII	MASIE 2023-17 YR AVE	SII 2023-17 YR AVE	MASIE 2023-2007
Jan	13.579	13.347	0.232	-0.207	-0.250	-0.183
Feb	14.481	14.177	0.304	-0.207	-0.292	-0.171
Mar	14.655	14.440	0.215	-0.212	-0.248	0.032
Apr	13.979	13.992	-0.013	-0.120	-0.025	0.283
May	11.866	12.159	-0.293	-0.742	-0.492	-0.561
June	11.044	10.963	0.081	0.242	0.099	0.218
July	8.431	8.183	0.248	0.152	0.150	0.439
Aug	5.825	5.561	0.264	-0.062	-0.083	0.241
Sept	4.430	4.371	0.059	-0.285	-0.360	0.132

The first two columns are the 2023 YTD shown by MASIE and SII, with the MASIE surpluses in column three.  Column four shows MASIE 2023 compared to MASIE 17 year average, while column five shows SII 2023 compared to SII 17 year average.  YTD September both MASIE and SII ~300k km2 below average. The last column shows MASIE 2023 holding a September surplus of 132k km2 over 2007.

Summary and Update

The experts involved in SIPN were expecting SII 2023 September to be higher than 2007 and somewhat lower than 2022.  The way it came out MASIE September was 285k km2 below average and 132 above 2007.  The Chart below shows the October ice recovery is well under way, reaching average briefly.

The table shows Day 281 (October 8) ice extents for NH overall and the regions, comparing 2023 to average and several years.

Region	2023281	Day 281	2023-Ave.	2007281	2023-2007
(0) Northern_Hemisphere	5349225	5448341	-99116	4653544	695681
(1) Beaufort_Sea	429938	633800	-203862	618242	-188304
(2) Chukchi_Sea	301437	249878	51559	27562	273875
(3) East_Siberian_Sea	180747	397106	-216358	311	180436
(4) Laptev_Sea	423091	235120	187971	302924	120168
(5) Kara_Sea	97994	54598	43396	22717	75277
(6) Barents_Sea	15003	21167	-6164	3580	11423
(7) Greenland_Sea	414298	285893	128405	414576	-278
(8) Baffin_Bay_Gulf_of_St._Lawrence	74944	64730	10214	71399	3545
(9) Canadian_Archipelago	266487	468946	-202459	408841	-142354
(10) Hudson_Bay	744	4166	-3423	1936	-1193
(11) Central_Arctic	3142582	3031785	110797	2780181	362401

On Day 281 Arctic ice was 100k km2 below average and nearly 700k km2 above 2007. The major deficits were in Beaufort, East Siberian seas and Canadian Archipelago.  Offsetting were surpluses in Laptev, Greenland sea and Central Arctic as well as smaller surpluses elsewhere.  From previous years we can expect that October 2023 will gain more than 3M km2 of ice extent over the ending extent in September.