More news from the American Geophysical Union meeting. Two new studies show that Swiss glaciers are 1) shrinking and 2) shrinking at an increasingly rapid rate. This means that researchers are observing the same phenomena in the Alps that have already been reported in the Himalayas here and here and in the Andes.
Swiss glaciers are melting away at an accelerating rate and many will vanish this century if climate projections are correct, two new studies suggest.
One assessment found that some 10 cubic km of ice have been lost from 1,500 glaciers over the past nine years.
The other study, based on a sample of 30 representative glaciers, indicates the group’s members are now losing a metre of thickness every year.
Both pieces of work come out of the Swiss Federal Institute of Technology.
“The trend is negative, but what we see is that the trend is also steepening,” said Matthias Huss from the Zurich university’s Laboratory of Hydraulics, Hydrology and Glaciology.
The investigators reported that there has been no measured change in snowfall accumulation, which when combined with melt rates, determines a glacier’s mass balance. Rather the melting away of the Swiss glaciers is attributed entirely to a longer melt season resulting from global warming.
In one [study], Daniel Farinotti and his team tried to assess the total volume of ice in Swiss glaciers -1,500 of them, from the mighty Aletschgletscher (the largest glacier in the Alps) to small ice fields that cover less than three square km.
The research used direct measurements where available, and combined this with modelling to estimate ice volumes for areas that are data-deficient.
The assessment found a total ice volume present in the Swiss Alps of about 75 cubic km by the year 1999 (a baseline for the purpose of the study). It is a bigger figure than previously thought.
“However, 1999 is quite some time ago now, so what we did was try to calculate the volume lost since this baseline; and we estimate a figure of 13% – from 1999 to today,” explained Mr Farinotti.
For 2003, remembered for its strong heatwave across Europe, the team estimates that 3-4% of the volume in Switzerland at that time was lost in that one year alone.
Farinotti points out that the largest 50 Swiss glaciers hold 80% of the total ice, which is fortunate since the smaller glaciers will all be gone within a few years. The largest glacier, the Aletschgletscher, is expected to survive until the end of the century.
The other study by a team lead by Matthias Huss analyzed 4 glaciers over the period from 1900 to 2007. (From the BBC article it appears that the authors may have since expanded their study to some 30 glaciers, but I cannot be certain as I do not have access to the paper as presented at the AGU meeting.)
In their paper Determination of the seasonal mass balance of four Alpine glaciers since 1865 [subscription required] published in March of this year in the Journal of Geophyisical Research the authors state that:
The aim of this study is to determine continuous time series of mean specific seasonal mass balance as well as the spatial distribution of mass balance of four well-documented glaciers in the Swiss Alps for the last 142 years. We extend the temporally limited mass balance series to the entire period since 1865, which marked the beginning of instrumental weather observations in Switzerland, and then resolve them into spatially distributed winter and summer balances. This provides a basis for the study of climate-glacier interaction in alpine environments and for the identification of processes that govern the mass balance evolution.
Mass balance of alpine glaciers is dominated by two processes not directly related to one another: Accumulation is due to deposition of solid precipitation and contributes mainly to the winter balance of the glacier surface; ablation is determined by the melting of ice and snow, and dominates the summer balance. Conventional mass balance programs often do not distinguish between the two components [Dyurgerov and Meier, 1999]. However, seasonal values of mass balance provide the best insights to assess the effects of climatic forcing on glaciers.
As it turns out, the period of greatest shrinkage took place not in the last decade but in the 1940’s, which tells us something about climate.
The annual variability of [equilibrium line altitude] ELA (ELA = the altitude on a glacier where the annual addition (accumulation) of mass is exactly compensated by the annual disappearance (ablation) of mass) induces an immediate step change in specific mass balance (b = total mass change divided by glacier area). is considerable. The lowest and the highest ELA values differ by 600 m. Even decadal mean ELAs show variations of up to 300 m between periods of positive and negative mass balances. The mean ELA was slightly higher in Period II [1942-50] than in Period IV [1998-2006]. This implies that the greater mass losses in the 1940s are a climatic signal. The 1940s were warm and dry, whereas the most recent period is even warmer but wetter. The greater mass losses in Period II seem also to be favored by the larger glacier extents, i.e., lower-reaching glacier tongues. Some adaptation of the glaciers to the changed climatic conditions has taken place in the last century enabling the ice mass to be closer to equilibrium with higher ELAs.
“Warmer but wetter” is significant because it is what the climate models predict as warmer global temperatures lead to increased ocean evaporation, which puts more moisture into the atmosphere leading in turn to greater precipitation in some areas (and less in others).
Time series of cumulative mean specific net balance for Aletsch, Rhone, Gries and Silvretta in 1865–2006. Two decadal periods with positive (I, III) and strongly negative mass balances (II, IV) are highlighted.
The authors write in the conclusion:
We demonstrate that the mass balance evolution of four glaciers in the Swiss Alps has undergone significant fluctuations. Two decadal periods of mass gains are found, which are due to less negative summer balances. The general trend since 1865 is strongly negative, however, displaying large differences between neighboring glaciers. The most negative mass balances occurred in the 1940s. This is due to extraordinarily low winter accumulation and high summer temperatures. In future, we plan to extend the spatial coverage of the seasonal mass balance series to more than 20 glaciers in Switzerland in order to shed light on regional differences in high Alpine mass balance evolution. Our results emphasize the need to continue in situ mass balance measurements in seasonal resolution over long periods. We provide a promising method for combining these point measurements with geodetic observations and mass balance modeling to obtain mass balance quantities with high spatial and temporal resolution and extend measured mass balance series back in time.
Huss points out the long-term significance for us of this glacial shrinking:
Switzerland’s glaciers are iconic but their shrinkage is more than just an issue for the tourists with their cameras; their loss would have profound ecosystem and economic consequences.
“Glaciers store the water in winter and release it in the summer when it is dry and warm when there is more need for water,” added Mr Huss.
“And they can also store it in the wet and cold years and release it in the hot and warm years. That’s an important reservoir.
“In the south-western part of Switzerland, almost all run-off water from glaciers is temporarily stored and used for electricity production. More than half the electricity consumed in Switzerland is produced from hydropower.”
Credits: map and chart above taken from: