In 2018, Swiss glaciers lost over 2.5 percent of their overall volume, reported the Swiss Academy of Sciences in a recent press release. This corresponds to 1.4 billion cubic meters of ice that melted from Switzerland’s glaciers in just one year.
However, this year of exceptional melting actually began with a rather promising winter season. The 2017-2018 winter commenced earlier than expected in Switzerland, starting in the first days of November and continuing through December with reported snowfall above average levels. January also saw higher temperatures than normal, as well increased precipitation.
While snow depth below 1000m elevation was around half the expected average by January, snow above 2000m elevation was still twice the expected average in March, representing the highest snow levels seen in the past 20 years.
GlacierHub interviewed the author of the press release, Matthias Huss, who said, “After the winter measurements in April and May, we actually thought that this might be a good year for the glaciers at last.” Huss is also the leader of the Swiss Glacier Monitoring Network (GLAMOS) and a glaciologist at the Swiss Federal Institute of Technology Zurich, Switzerland.
However, both April and May were hot and dry, decreasing snow at altitude to relatively normal levels. Then, the months from April to September were characterized by drought conditions and high temperatures, making it the third-hottest and overall driest summer on record.
“This is probably the largest annual shrinkage since the mega-heatwave of 2003,” said Martin Beniston, an honorary professor and former director of the Institute for Environmental Sciences at the University of Geneva, Switzerland, in an interview with GlacierHub.
Both Beniston and Huss told GlacierHub that, had it not been for this snow-rich winter, Switzerland’s glaciers would have faced even more extreme losses. Indeed, the above-average quantities of snow in the Alps during winter 2017-2018 helped offset some loss of ice this summer.
In an interview with GlacierHub, Mauri Pelto, a glaciologist at Nichols College and the director of the North Cascades Glacier Climate Project commented on the implications of 2018’s extreme melting. “The significance of a big year of melt followed by another is there will be no comparable rebound,” he said.
Wilfried Haeberli, a glaciologist and professor emeritus at the University of Zurich, Switzerland, put this year’s loss in perspective. “Since the turn of the century the average loss rate of all glaciers in the Alps can be estimated at around 1-2 percent per year. The loss rate of 2018 is roughly twice this amount,” he noted in an interview with GlacierHub. Together in the last 10 years, Swiss glaciers have lost one-fifth of their volume, which is enough to cover the entirety of Switzerland with 25 cm of water.
While certainly extreme, losing 2.5 percent of glacial volume in one year is not unprecedented. Years with observations of “extreme” glacier melt are becoming both more frequent and more severe. Huss recalled the years 2015 and 2017, when Swiss glaciers lost comparable amounts of ice, saying, “2018 was not absolutely exceptional, in terms of the last decade. And this is of course the actually worrying news.”
Pelto, Beniston, and Haeberli echoed similar sentiments, saying that the observed losses for Swiss glaciers were, “exceptional but not unusual,” and that 2018 was, “hardly a surprise,” but instead, “part of a long-term development, which is in agreement with robust results from model simulations about global warming and glacier vanishing,” respectively.
“The fact that high snowlines and mass balance loss are affecting glaciers in every corner of the world indicates that this is not a regional change, but that global climate change is the driver,” said Pelto.
Huss also pointed out the difficulty of deducing whether extreme conditions in the past few years is due to weather variability, or whether we are to experience these extremes as our new normal. However, noting that the volume loss for Swiss glaciers in the past decade was more than expected based on projected scenarios for the 21st century, he is certain that, “if it is the latter, then we might expect Swiss glaciers to disappear even earlier than expected.”
According to Beniston, since the 3rd Assessment Report of the IPCC in 2001, projections have estimated that at the current rate of climate change, glaciers will decline by anywhere from 50 to 90 percent by 2100. “[This year] provides a measure of things to come,” he said, “in the sense that by the second half of the 21st century, what are considered extreme summers today (like 2018) will become average summers.”
Ultimately, Haeberli told GlacierHub he sees these striking glacier mass losses as “writing on the wall,” indicating that opportunities for action to reduce impacts of global warming are now being lost. He closed his comments by calling upon the necessity of “rapid deceleration” of greenhouse gas emissions in order to limit negative effects on living conditions on Earth and allow us more time to “develop well-reflected sustainable adaptation strategies.”
A recent study on the Borgne d’Arolla, a glacier-fed stream in the Swiss Alps, shows that there is less biodiversity among macroinvertebrates than expected in the summer and higher biodiversity than expected in the winter. Chrystelle Gabbud, a geologist at the University of Lausanne in Switzerland, and her associates, found that the rates of streambed disturbance in the Borgne d’Arolla were also much more frequent than normal observations of disturbance in glacial rivers, even during times of peak discharge. The team’s results were published in September in Science of the Total Environment and attribute the above biodiversity inversion phenomenon to the increased frequency of flushing events.
Why is it that glacier-fed rivers in the Alps are experiencing even more flushing events? Evidence points toward the impacts of global climate change, as rising temperatures influence increased glacial melting and sediment production during the summer months, which in turn means that flushing must be facilitated more often.
Summertime runoff in glacier-fed Alpine rivers is exceptionally useful for supplying water for hydroelectric power production. The flow of water is abstracted at water intakes, which hold back both water and sediment, functioning similarly to dams but on a smaller scale. Intakes also have a relatively low threshold for how much sediment can accumulate before they must be flushed. This means that in basins with high erosion, namely glaciated basins, this flushing happens more frequently. In the summer months, when glacial melt is at its peak, flushing of water intakes can occur up to several times a day. Flushing disrupts the streambed, increases water turbidity, contributes to river aggradation, and negatively affects the macroinvertebrate community both in abundance and biodiversity.
Gabbud and fellow researchers collected samples of macroinvertebrates (animals that do not have a backbone but that are large enough to be seen with the naked eye, such as crustaceans, worms and aquatic insects) at several locations over the course of two years (2016 and 2017) to determine the impacts of flushing water intakes on species biodiversity and abundance. The surrounding tributaries served as controls for the Borgne. The researchers’ findings effectively contradicted the normal expectations for seasonal biodiversity changes.
Normal biodiversity expectations anticipate that both species richness and abundance should be higher during the summer months, from June to September, which also correspond to the highest water temperatures. However, Gabbud and her team found that biodiversity of macroinvertebrate populations in the Borgne d’Arolla during winter months (and coldest water temperatures) was comparable to the expected levels for the surrounding tributaries during the spring and summer. The Borgne was found to be mostly devoid of life in the summer months, a result which the researchers primarily attribute to the high frequency of flushings.
The team also compared observations in 2016 to those in 2017. Variations in flushing frequency and duration between the two years led Gabbud and her associates to two determinations. One, that more flushing had a direct negative impact on the presence of macroinvertebrate biodiversity and abundance. Two, that flushings with shorter duration also correlated with higher rates of streambed disturbance.
In addition, they found that as the frequency of flushing decreased, macroinvertebrate populations started to return. Outside of the summer months, flushing happens much less frequently. In a four-day period between flushes, biodiversity was almost able to reach pre-disturbance levels.
The researchers’ observations led them to recommend that the frequency of flushing at the water intakes be decreased and the duration of flushing be increased. They stipulate that higher magnitude flushings, resulting from taking too much time between events, could also have negative impacts. Thus, this situation creates a tension between maintaining hydropower and maintaining biodiversity, a major policy issue.
Currently, Switzerland has a single set of regulations regarding mitigating impacts and restoring ecological areas being used for hydropower generation. There are provisions related to sediment management; however, guidance provided by the Swiss National Government does not mention water intakes by name, instead only addressing dams and maintaining sedimentconnection.
Seeing as water intakes govern over 50 percent “of hydropower impacted rivers by basin area” in the Swiss Alps, Gabbud and her team emphasize that future regulations must incorporate both sedimentmanagement and flow management.
From Science: “About 1 million years ago, one of Earth’s most important metronomes mysteriously shifted: Ice ages went from occurring every 40,000 years to every 100,000 years. At the same time, the ‘conveyor belt’ of warming currents in the North Atlantic Ocean slowed sharply. Last week, scientists at the Goldschmidt Conference presented a clue to these twin mysteries: evidence that glaciers in the Northern Hemisphere suddenly began to stick to their beds. Growing thicker, they might have triggered a cooling that disrupted the conveyor belt and allowed the 100,000-year cycle that we see today to take root.”
Glacier Recession and Summer Streamflow in the Cascades
From Water Resources Research: “The Pacific Northwest (PNW) is the most highly glacierized region in the conterminous United States (858 glaciers; 466 km2)… We applied a high‐resolution glacio‐hydrological model to predict glacier mass balance, glacier area, and river discharge for the period 1960‐2099…Results show that the rate of regional glacier recession will increase, but the runoff from glacier melt and its relative contribution to streamflow display both positive and negative trends.”
From New York Times: “After an emergency landing on a Swiss glacier, the group of 12 Americans drank melted snow and survived on rations of one chocolate bar a person until daring pilots shuttled them to safety after five days marooned on the ice. Relics of that harrowing adventure and the successful rescue of all those onboard…resurfaced after more than 70 years this month when scorching summer temperatures in Europe caused the glacial ice to recede.”