Tuesday, August 28, 2012

Unprecedented snow melt and heat in the European Alps

The recent heat wave in Europe has especially been anomalous at higher altitudes resulting in some of the highest Alpine peaks in Europe being snow-free for the first time on record including the iconic peak Matterhorn.

Early snow melt and record temps at mountain-top stations in the Alps

On August 19th the temperature at Jungfraujoch, Switzerland (the highest railway station in Europe) reached 12.8°C (55.0°F) the warmest temperature ever measured at this site where records began in 1937. This observatory is located at an elevation of 3580m (11,745’) just above the famous railway station. 

The significance of this is that this site has been studied by European climatologists for 75 years and is considered a 'bell-weather' location because of its long POR and isolation from surrounding possible human-induced influence. 

The Jungfraujoch Observatory of Switzerland  (not a recent photo)

The Jungfraujoch Observatory has the longest (since  1937) temperature time series of any high-altitude (3000m+) weather station in Europe. Graphic and caption from Meteo Swiss.

Another site on the border of Switzerland and Italy near the summit of Mt. Rosa (2nd highest mountain in the Alps after Mt. Blanc) named Capanna Regina Margherita (also known as Mt. Signalkuppe) and located at an elevation of 4554m (14,940’) registered a record temperature of 8.3°C (47.0°F) on August 20th. This surpassed its previous record high of 7.2°C (45.0°F) although records have only been kept here for about 15 years. The minimum temperature at the site that day was -0.1°C (31.8°F), also a record. This is the highest weather station in Europe. The Plateau Rosa near here is snow-free for the first time on record.

Aguille du Midi, a mountain in the Mt. Blanc massif in the French Alps, with an elevation of 3842m (12,605’) registered a high of 13.4°C (56.1°F) and low of 4.7°C (40.5°F) on August 19th, both records for the site since it was built in 1955. The peak is accessible by a cable car from the ski resort of Chamonix, France. Chamonix (elevation 1035m/3,396’) also recorded its all-time record warmest temperature on August 20th with a 34.4°C (93.9°F) reading. For the first time on record the peak of Aguille du Midi is now snow-free.

(not a recent photo)

For the first time in memory many of the highest Alpine peaks, including the iconic Matterhorn, have lost their entire snow cover (aside from glaciers). Sonnblick Observatory in Austria (located at 3030 m/9,940’) had its earliest snow melt on record this summer when the last of the winter snow disappeared by July 31st. The previous earliest snow melt (since records began here in 1886) was August 12th, 2003, the year of the famous European heat wave.

Alpine Glacier Melt

The Pasterze Glacier in Austria as photographed in 1875 (top) and then again in 2004 (bottom). Bottom photo by Gary Braasch.

It has been widely recognized (and researched) that most of Europe’s Alpine glaciers have been in retreat for the past 60 years or so. How much of this is due to solar radiation and how much to Global Climate Change remains a center of debate although it would seem that the two are related. An article in Geophysical Research Letters (Vol. 36, 2009) by M. Huss et al studied a 94-year time series of annual glacier melt at four high elevation sites in the Alps and found that the first massive melt off occurred in the late 1940s when “global shortwave radiation over the summer months was 8% above the long-term average and significantly higher than today”. Dimming of solar radiation from the 1950s until the 1980s reduced glacial melt rates. In the 1990s to the current time solar radiation has increased again but this time (since 2000) has also been accompanied by warmer summertime surface temperatures. Thus the glacial melt rates have exponentially increased in the past decade.

NASA released this statement at the annual AGU (American Geophysical Union) meeting in San Francisco last December (2011):

“Dec. 12, 2011: A new glacier inventory of the French Alps produced by Marie Gardent and colleagues at the University of Savoie has found that 100 square kilometers of glacier area has been lost between the early 1970s and today—a 26 percent loss. Using Landsat data together with historical aerial photography and maps, Gardent was able to evaluate and compare historic and contemporary glacier surface area.”

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