Climate change is evident even at high altitudes in the Alps. There, the snowpack has melted almost three days earlier every decade since the 1960s, as measured data now confirm. By the end of the century, the snow at an altitude of 2500 meters could even disappear a month earlier than it does today. This could have considerable consequences for many alpine plants, because they then lack the insulating layer of snow against the spring frosts.
Whether in Antarctica, America or Europe – global warming is causing glaciers to shrink all over the world. In the meantime, more and more snow and ice are melting in the Alps. According to forecasts, they could even have almost completely disappeared by 2100. And that not only has consequences for ski tourism. The water cycle in the mountains will also change and the flora and fauna will have to adapt to the rising temperatures. In the case of alpine plants, the snowmelt in spring normally determines the time of the growing season.
What can you expect from the Alps?
Scientists working with Maria Vorauf from the University of Basel have now investigated how the timing of alpine snowmelt has changed and how this could develop in the future due to global warming. They also wanted to estimate how this development affects the vegetation period of the alpine plants. “The snow cover protects alpine plants from frost and the growing season begins when the snow melts. Changes in the snowmelt have a very strong impact on this period, ”said Vorauf. In their study, the research team first examined whether and how much the time of snowmelt has changed in recent decades and how much the air temperature and snowfall play a role in this.
So far, only a few series of measurements on the snowpack at high altitudes have been available, as much of the measurement data was only collected in the vicinity of inhabited areas below 2000 meters. The “intercantonal measurement and information system” used by the researchers, on the other hand, has automatically recorded the snow depth in the Swiss Central Alps between 2000 and 3000 meters every half hour since 2000. The team combined these data with series of measurements from 23 lower-lying stations, the manual measurements of which go back to at least 1958. Based on the evaluated measurement data and the latest climate scenarios for Switzerland, the scientists were able to create a model that enables forecasts of the future development of the alpine snowpack. With this she predicted the shifts to be expected by the end of the 21st century.
Six days earlier in the future
According to the measurement data, the day of the snowmelt has shifted steadily forward over the past centuries. “There was a clear trend towards earlier snowmelt, and for ten stations this shift was statistically significant,” the researchers said. According to this, the snowpack melted between 1958 and 2019 at an altitude of 1000 to 2500 meters every decade on average around three days earlier. However, this shift was not linear; it was particularly pronounced in the late 1980s and early 1990s. This corresponds to the strong temperature increases in this period of time, as demonstrated in climate research.
If greenhouse gas emissions continue to rise as before without consistent climate protection, then the date of the snowmelt in the last third of the 21st century will very likely be advanced by six days per decade, the researchers estimate. This means that at the end of the century, snowmelt at an altitude of 2500 meters would occur around a month earlier than it is today. And this development obviously cannot be stopped by heavier snowfalls: The higher precipitation in winter, as forecast in the climate models for Switzerland, cannot compensate for the earlier snowmelt at high altitudes, according to Vorauf and her team. Because the changed air temperature is more decisive for the snowmelt than the height of the snow cover, according to the scientists. “As soon as the three-week average air temperature exceeds five degrees Celsius, the snow melts relatively quickly,” explains Vorauf. “The temperature is much more important than the height of the snowpack, especially at high altitudes.”
Consequences for the alpine vegetation
This development could have considerable consequences for alpine plants: premature snowmelt could in future lead to the growth time for alpine plants being extended by around a third. As has already been proven by other studies, an accompanying early start of the growing season can lead to a lower number of flowers, reduced leaf growth and a lower survival rate for alpine plants because they and the soil are less protected from frost due to the lack of snow cover . “Some species, such as the crooked sedge, which is typical of alpine turf, will grow and bloom earlier because of the earlier snowmelt,” explains Vorauf.
However, the alpine plant species – despite the faster rising temperatures in the alpine region – are not necessarily more affected by climate change than plants at other altitudes. “The topography and exposure of the alpine terrain creates very diverse microclimates in the smallest of spaces. The plants can move into this at a constant height over short distances, ”explains Vorauf. As a result, alpine plant species do not always have to “flee” upwards, as was often assumed up to now.
Source: University of Basel, Article: Climatic Change, doi: 10.1007 / s10584-021-03027-x