Arctic Sea Ice Is Growing Despite Summer-Like Weather in Finland

Finnish meteorologist Pekka Pouta reported that in some parts of Finland, the so-called thermal summer is still continuing. This means that the average daily temperature remains mostly above ten degrees Celsius.

This is unusual, as we are already in October, meaning that according to the calendar we are in the middle of autumn. In addition, according to Pouta's forecast, warm air currents will reach Finland in the coming days as well, so the summery weather looks set to continue.

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Based on this, one might imagine that the melting of the ice fields in the Arctic Ocean would likewise continue at a rapid pace. This is not the case, however. During the past few days, Arctic sea ice has expanded rapidly, to the extent that according to the latest data (from the day before yesterday), its extent was greater for this time of year than at any point since 2014.

In fact, Arctic sea ice begins to grow every year in September, including this year. According to the National Snow and Ice Data Center, the average extent of Arctic sea ice in September was the largest since 2022, as shown in the figure below. 

The figure also shows that the average extent of Arctic sea ice in September has, in practice, neither increased nor decreased significantly since 2007. Consequently, the enthusiasm—particularly among the Russians—to use the Northeast Passage for freight transport does not appear likely to diminish, unless the trend in sea-ice extent returns to the downward trajectory seen between 1995 and 2007.

Previous thoughts on the same topic:
Recent Arctic Sea Ice Decline Is Not Accelerating
Observations on Arctic Sea Ice Challenge the Notion of Particularly Rapid Melting
Stalled Melting of Northern Polar Ice Buys the West Time to Strengthen Arctic Capabilities

Northern Sea Ice Area Has Not Responded to Exceptionally High Temperatures

The past October was extremely hot in many places (one, two, three examples), and for that reason, I checked NASA's NSIDC website to see if the northern sea ice might also have started melting. However, this was not the case; rather, it was the fifth largest in recorded history, as shown in the image below, which presents the polar ice area for each October over the years.

The October area of the northern sea ice was at its smallest in 2020, followed in order by 2007, 2016, and 2019. After these years comes the current year, 2024.

Thus, the area of northern sea ice has not responded to the exceptionally high temperatures on Earth’s surface—or, alternatively, there may be inaccuracies in the measurements of either the surface temperature or the ice area. Time will eventually reveal which explanation is correct.

In any case, throughout 2024, the northern sea ice area has not been the smallest on record for any month. In January, it ranked as the 24th smallest, in February the 14th smallest, in March the 25th smallest, in April the 27th smallest, in May the 24th smallest, and even in June it was the 11th smallest. After that, the melting rate of the ice accelerated compared to other years, and in July its area was the 5th smallest on record, in August the 2nd smallest, in September the 4th smallest, and in October the 5th smallest.

I won’t attempt to predict the coming months. Instead, I would like to point out to you - my esteemed readers - that the image above, which I generated based on NSIDC data seems to suggest that the melting of the ice, which began in the early 1990s, may have stabilized around 2007 and is now oscillating around a new equilibrium or is decreasing noticeably more slowly than in previous years.

I wrote earlier this year about a similar phenomenon in the July statistics, and indeed, it is also evident in the statistics for all other months. So, it remains to be seen how the ice area will develop over the last three months of this year.

Previous thoughts on the same topic:
Reevaluating Arctic Sea Ice Melt: A Closer Look at Trends and Predictions
Climate Model Predictions and the Reality of Arctic Sea Ice
Can climate models predict the distribution of warming?