From Science Matters

By Ron Clutz

The animation shows the rapid growth of Arctic ice extent during October 2025, from day 274 to day 304, yesterday.  For all of the fuss over the September minimum, little is said about Arctic ice growing 3M km2, that’s 3 Wadhams in one month!.  Look on the left (Russian side) at the complete closing of the Northern Sea Route for shipping.

The graph below shows 2025 compared to the 19-year average (2006 to 2024 inclusive), to SII (Sea Ice Index) and some notable years.

This year October added 2.6M km2 from end of September compared to an average October increase of 3.4M km2.  The first two weeks were above average, before the refreezing rate slowed down ending in a deficit of ~0.5M km2.  In other terms the end of October ice extents were four days behind the average, according to MASIE.  SII started the same, but tracked lower in the second half of October.

The table below shows the distribution of ice in the Arctic Ocean basins.

Region	2025304	Day 304 Ave.	2025-Ave.	2007304	2025-2007
(0) Northern_Hemisphere	7867621	8401977	-534356	8175072	-307451
(1) Beaufort_Sea	975681	937777	37904	1038126	-62444
(2) Chukchi_Sea	683493	466318	217175	242685	440809
(3) East_Siberian_Sea	1087032	952325	134707	835071	251961
(4) Laptev_Sea	849204	848501	703	887789	-38585
(5) Kara_Sea	137515	478870	-341355	311960	-174445
(6) Barents_Sea	1466	81088	-79621	52823	-51356
(7) Greenland_Sea	351374	418343	-66969	443559	-92184
(8) Baffin_Bay_Gulf_of_St._Lawrence	128777	247258	-118481	289374	-160596
(9) Canadian_Archipelago	568663	740190	-171526	817220	-248557
(10) Hudson_Bay	8609	66501	-57892	48845	-40236
(11) Central_Arctic	3051977	3153485	-101508	3206345.33	-154368

Overall ice extent was 534k km2 below average or 6%.  Surpluses appear on the Eurasian shelf seas of Beaufort, Chukchi and East Siberian, while sizeable deficits are shown elsewhere on the Atlantic side, especially Kara, Baffin Bay, Canadian Archipelago and Central Arctic.

Illustration by Eleanor Lutz shows Earth’s seasonal climate changes. If played in full screen, the four corners present views from top, bottom and sides. It is a visual representation of scientific datasets measuring ice and snow extents.