Why a second catastrophic glacier year in a row?

Glaciers continue to melt rapidly

According to the Swiss Commission for Cryosphere Observation of the Swiss Academy of Sciences, which is in close contact with the Swiss Glacier Monitoring Network (GLAMOS – Glacier Monitoring in Switzerland, which systematically documents and monitors long-term glacier changes in the Swiss Alps) operated by the ETH and the Universities of Fribourg and Zurich, Swiss glaciers have lost around 4 percent of their volume this year, compared to around 6 percent last year. This is the second sharpest decline since measurements began. This means that as much ice has been lost in the last two years as in the three decades from 1960 to 1990. The two extreme years in succession led to the disintegration of glacier tongues and the disappearance of some small glaciers, among other things. This year, for example, measurements at St. Annafirn in the canton of Uri had to be discontinued. The same happened to the Pizol Glacier in 2021, which was buried in 2019 to great media effect (see Fig. 1).

The reasons for the rapid retreat of Swiss glaciers in the last two years are explained below.

Far above-average temperatures during the melting period

The glacier melting or ablation period lasts from around May/June to September/October, during which time temperatures are decisive for the extent of glacier melting. Like last year, this year's summer (June to August) was significantly too warm (2023 1.7 degrees, 2022 even 2.3 degrees, see Figs. 2 and 3). This makes this year the fifth warmest summer and last year the second warmest since measurements began in 1864.

With the exception of last September, the above-average temperatures continued in September and October, with 2023 being the warmest September ever recorded and 2022 the warmest October ever recorded, followed by this year's October. Only last year's September is out of line, which was even slightly below average. This year in particular, it took a very long time in the fall for snow to cover the glaciers and stop the ice from melting. In addition, the zero degree line was very high until well into October and even reached new record highs of over 5000 meters in September (maximum 5253 meters on September 4th).

Extremely snow-poor winter in 2021/2022 in particular

The winter of 2021/2022 and the spring of 2022 (see Fig. 4) were significantly too dry and therefore had little snow on the mountains.

This resulted in record-early melting on the mountains in 2022 (see Fig. 4) and thus also on the glaciers, so that the melting phase began very early.

In addition, there were several, sometimes intense, Saharan dust events, especially in mid-March. The dust settled on the snow and made it particularly dirty. The dark dust reduced the reflectivity (albedo) of the snow and, in turn, increased the absorption of solar energy. This significantly accelerated the melting process.

This year, the winter was too dry, but the spring was not (see Figs. 5 and 6).

As a result, there was much more snow on the glaciers at the end of spring than last year, so the melting phase began later, which initially did not look so bad for the glaciers. However, as mentioned above, this was followed by a summer with significantly above-average temperatures and an early fall, which ruined the good initial situation. The June, which was far too warm with long dry spells, was particularly bad. In addition, after the extreme melting last year and thus the bare ice up to great heights, the old ice and not last year's firn immediately reappeared after the melting, which further promoted the strong melting. So to a certain extent, this year's strong melting was also a consequence of last year's record year.

Finally, two comparative images of 2019 and 2023 at the Morteratsch Glacier, whose tongue the writing meteorologist has been visiting every fall for more than 10 years now. Although there has hardly been any major change in the position of the glacier tongue in the last 4 years, there has been a marked decrease in glacier thickness and an increase in melt craters on the glacier tongue (see Figs. 8 and 9).

The alarming retreat of Swiss glaciers in the last two years is a cause for concern. One of Switzerland's leading glacier researchers and head of the Swiss glacier monitoring network Glamos, Dr. Matthias Huss, puts it this way: "I hope that people realize how far advanced the climate crisis already is. The glaciers are only one effect, but they make the very strong warming very tangible and visible."