Bas d’Arolla Glacier, Switzerland No Longer Reaches Valley

On July 25, 2018April 27, 2024 By mspeltoIn switzerland glacier retreat

Bas d’Arolla Glacier in Landsat images from 1990, 2001 and 2017. Red arrow is 1985 terminus, yellow arrow 2017 terminus location, purple dots annual snowline. A=Bas d’Arolla O=Otemma

Bas D’Arolla Glacier is one of the glaciers where the terminus is monitored annually by the Swiss Glacier Monitoring Network (SCNAT). Here we examine changes in this glacier from 1985 to 2017 including changes in the terminus, snowline elevation and tributary connection during this period using Landsat Imagery. SCNAT reports that the glacier advanced 136 m from 1972-1987, retreated at a rate of 17.6 m/year from 1987-2001, and 23 m/year from 2001-2017. The main accumulation zone between Pigne d’Arolla and Mont Collon extends from 2900 m to 3400 m, with a saddle to Otemma Glacier at 3000 m. An icefall extends from 2400 m to 2900 m. In 1985 the glacier had a low elevation terminus tongue extending from the base of an icefall at 2400 m to just below 2200 m (see map below).

In 1985 the glacier terminates at the red arrow at an elevation of 2160 m and the snowline is at 2940 m. In 1990 the terminus had advanced slightly up to 1987 and then retreated slightly with not significant overall change and the snowline is again at 2940 m. By 2001 the glacier has retreated 220 m, and the snowline is at 2900 m. In 2015 the snowline is at 3100 m with the saddle to Otemma Glacier not in the accumulation zone. This saddle should always be snow-covered. In 2017 the snowline is at 3200 m, the saddle with Otemma Glacier is again exposed and is in fact glacier ice, indicating that snow and firn has been lost and this is no longer part of the persistent accumulation zone. The main terminus tongue in 1985 that occupied the valley floor and extended 500 m from 2400 m to the terminus is gone, with a total retreat of 600 m since 1985. The glacier retreat is similar to that of neighboring Otemma Glacier and more substantial than Gietro Glacier, and reflects an annual snowline that is too high to maintain the glacier terminus tongue. the Bas d’Arolla valley floor is now glacier free. The river discharges into the Rhone River Basin, which has substantial hydropower south of Lac Geneva. Schaefli et al (2018) observe that of the 50% of Swiss power that comes from hydro, glacier mass loss alone has provided 3-4% of the total, not a sustainable model. Bliss et al (2014) indicate that the Swiss Alps have passed peak glacier runoff.

Bas d’Arolla Glacier in Landsat images from 1985 and 2017. Red arrow is 1985 terminus, yellow arrow 2017 terminus location, purple dots annual snowline. A=Bas d’Arolla O=Otemma

Map of the Bas d’Arolla Glacier and Mont Collon area, from Swisstopo

Google Earth image indicating flow, and the fact that the glacier now terminates in the icefall region, no longer reaching the valley floor.

Otemma Glacier Retreat & Snowline Rise, Switzerland

On July 7, 2015May 3, 2024 By mspeltoIn climate change glacier retreat, glacier climate change, Glacier Observations

Otemma Glacier is in the Upper Rhone River watershed and feeds Lac de Mauvoisin. Climate change is altering this glacier, with terminus change not being the main story it is the rising snowline and separation from tributaries. The lake fed by the glacier is impounded by Mauvoisin Dam one of the 10 largest concrete arch dams in the world. The reservoir can store 200 million cubic meters of water. The dam provides hydropower and protection against natural hazard. In 1818, an advance of the Gietro Glacier, now retreated high above the reservoir, generated ice avalanches which blocked the flow of the river. When the ice barrier was breached, 20 million cubic meters of flood water was released devastating the valley (Collins, 1991).There are several other large glaciers in the basin Gietro, Mont Durand and Brenay that provide runoff to power what is today a large hydropower project. The Mauvoisin Dam can produce 363 MW of power.

Otemma Glacier is one of the glaciers where the terminus is monitored annually by the Swiss Glacier Monitoring Network (SCNAT). Here we examine changes in this glacier from 1985 to 2014 including changes in the terminus, snowline elevation and tributary connection during this period using Landsat Imagery. SCNAT reports that the glacier retreated at a rate of 27 m/year from 1985-1999, to 40 m/year from 2000-2014.

Google Earth view of the glacier indicating glacier flow direction.

In 1985 the glacier terminates at the yellow arrow, with tributaries A,B & C all joining the main glacier. The snowline is at 2800 m, green dots. In 1988 the snowline extends to the divide with Bas Glacier d’Arolla at 3050 m. In 1999 the snowline also extends to the divide with Glacier d’Arolla. Tributary A no longer connects to the glacier, pink arrow, and the terminus has retreated 300 m.

By 2013 Tributary B is also detached from the main glacier (orange arrow). The terminus has retreated to the red arrow a distance of 1010 m over the thirty year period. The snowline in 2013 and 2014 almost reaches the divide with Bas Glacier d’Arolla with a few weeks left in the ablation season. The area of persistent snowcover is thus restricted to the region above 3050 m. This region is not large as the Bas Glacier d’Arolla captures most of the upper basin. That the snowline is consistently reaching the highest divide for this large glacier is noteworthy. The retreat of the large valley tongue of Otemma Glacier will remain rapid given the consistent high snowlines indicative of limited retained accumulation. Even with current climate not much of the Otemma Glacier can survive. The rising snowline is observed on most glaciers including nearby Rutor Glacier, Italy.

1985 Landsat Image

1988 Landsat Image

1999 Landsat Image

2013 Landsat Image

2014 Landsat Image