September 18, 2025: Arctic sea ice has experienced another very small increase rate for this week of 0.36% (last week’s increase rate was 0.09%), from the level on 09/11/2025 of 4.671 M km² to 4.688 M km² for this week.  So, it looks like we have probably reached that transition point to the sea ice increase season.

The sea ice extent for 2025 to date has now dropped one more spot to 12th place for the lowest sea ice extent for this day of the year as noted below when the lowest sea ice extent was at 3.452 M km² on 09/18/2012. 

Ranking of lowest sea ice extent for the day of the post, values in M km² :

2012    3.452
2020    3.904
2007    4.156
2019    4.166
2023    4.267
2024    4.326
2016    4.441
2008    4.548
2011    4.576
2015    4.585
2010    4.628
2025    4.688

The negative sea ice anomaly this week was greater than the anomaly of -0.74646 M km² on 09/11/2025 to a higher negative anomaly of -0.78362  M km² on 09/18/2025, and so more anomalously negative for this time of year.