Science & Technology: Researchers: Climate Change Warms Groundwater

Climate change warms groundwater

A level cap, a groundwater measuring point of the Weiden water management office. Not only the air and the seas are getting warmer – climate change is also becoming noticeable underground with rising temperatures. Photo: Hannes Hemmerle / dpa

(Photo: dpa)

According to a study at Bavarian measuring points, the groundwater in the Free State has warmed up significantly. At a depth of 20 meters, the water is on average almost one degree warmer than 30 years ago, report scientists from the Martin Luther University Halle-Wittenberg (MLU) in the journal “Frontiers in Earth Science”. The rise in temperature below ground was only marginally below that of the air.

The researchers compared the temperatures at 35 measuring stations across Bavaria at different depths with data from the 1990s. If the air warms up, the soil will become warmer over time – and with it the groundwater. “In contrast to the atmosphere, the subsurface is very sluggish,” said MLU geoscientist Peter Bayer, one of the authors. It shows rather long-term trends – a good indicator of climate change.

The results match previous findings by other researchers. As early as the late 1980s and early 1990s, it became apparent that the groundwater in the Swabian and Franconian Jura was warming, although the topic of climate change was only just beginning to be discussed, said Thomas Himmelsbach, head of the Groundwater and Soil Department at the Federal Institute for Geosciences and Raw Materials (BGR).

“We now have an eye on this worldwide,” explained the hydrogeologist. “The groundwater is a reflection of the mean annual temperature of the air. There is a certain time lag, but the temperature pays itself through. ” A few years ago the Federal Agency carried out a study of a completed lens filled with fresh groundwater on the North Sea island of Langeoog. There it could be proven that the temperature had risen by an average of around one degree within 80 years.

There are already some dramatic consequences of the warming of the soil and groundwater – on animals and plants, but above all on the water balance, says Himmelsbach. “The world‘s biggest impact is the melting of glaciers and permafrost.” At a water conference in Baku, people asked themselves: Why is the Caspian Sea rising? Why does the Volga have so much water? Now it turns out: the reason is probably increased inflows from northern Russia. In some ports in the Caspian Sea there are already problems with the water level.

In this country, the greatest concern so far has been a drop in the groundwater level as a result of climate change – because depending on the region, there is less rainfall and the underground reservoirs no longer fill well.

“The new study shows once again how extensive climate change is. It changes our entire planet – not only outside, but also inside, ”commented Bavaria’s Environment Minister Thorsten Glauber (Free Voters) on the study. Another alarm signal is that climate change is warming groundwater. ” Bavaria should become climate neutral by 2050. “We have to act now.”

On average, according to the study, the groundwater in the Free State at a depth of 20 meters was almost 0.9 degrees warmer than it was in the 1990s. At a depth of 60 meters, the warming was around 0.3 degrees. During the same time, the average air temperature rose by 1.05 degrees Celsius. From a depth of about 15 meters, short-term local or seasonal fluctuations can no longer be measured, it said.

The consequences of water warming underground are difficult to assess, said study co-author Bayer. A higher water temperature affects the growth of microbes, for example. It puts subterranean ecosystems under pressure, which are adapted to very constant temperatures.

Himmelsbach referred to reefs off Australia and also the North Sea, where there are now Pacific oysters. “They probably couldn’t have stayed there earlier,” said the hydrogeologist. “A degree is a lot. Flora and fauna will change. “

Study on the Internet

Federal Environment Agency on climate change

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