Slowly turning like sunflowers towards polar satellites in space, four large antennas dominate the snowy Finnish Meteorological Institute's Arctic Space Centre in Sodankyla, a small town of 8,000 inhabitants just north of the Arctic Circle.

Situated amidst forests, peatlands and snaking rivers, the research space has become a unique site due to its history of obtaining data on weather and climate.

"This is an excellent location for studying the boreal forest, the environment here in the Arctic and utilising the satellite data for observing climate change," Jyri Heilimo, head of the Arctic Space Centre Unit, told AFP.

"Polar orbiting satellites' orbits are converging in the poles, meaning that the Sodankyla ground station at 67 latitude can receive much more data from the satellites per day compared to, for example, the station close to the equator," Timo Ryyppo, the head of Sodankyla Satellite Data Centre said.

By using both ground measurements and satellite data, researchers have been able to study how the snow and ice cover in the northern hemisphere has changed over the years.

"We've been able to say that the snow extent has been decreasing. The amount of snow has been mostly constant, but it's unevenly distributed," said Ryyppo.

Some 550 different measuring devices are scattered across the observatory site, including several instruments attached to a 25-metre (80 feet) tower in a pine forest monitoring greenhouse gases from trees, soil and atmosphere.

"We want to know this Arctic pixel well in order to know the Arctic well," Heilimo said, as snow fell from a gloomy sky and temperatures hovered around zero Celsius (32F) in February. Locals are more accustomed to temperatures of -20C this time of the year.

Heilimo showed a graph displaying how the average temperature had trended upwards at double the speed compared with other parts of the world since measurements began on the site in 1908, as a result of human-induced climate change mostly blamed on fossil fuels.

According to a study in the Nature journal, the Arctic has warmed nearly four times faster than the globe since 1979.

"There is a cliche that 'what happens in the Arctic doesn't stay in the Arctic'... That means that the changes we see here, the melting permafrost, the temperature rise, will happen in other places also. It just happens faster here," Heilimo said.

- 'More and more important' -

Sodankyla's ground measurements have played an increasingly crucial role in supporting Europe's satellite observations tracking the changing climate in the Arctic, Simonetta Cheli, director of Earth Observation Programmes at the European Space Agency (ESA) told AFP.

The agency launched an 'Arctic-Boreal Earth Observation Supersite' with the Finnish Meteorological Institute in Sodankyla in February.

Measuring atmospheric carbon dioxide on top of snow from a satellite was "very, very difficult", Heilimo said.

"That's why we are here -- to measure and compare the satellite measurements in the Arctic area in winter conditions and to allow us to develop better methodology for detecting the atmospheric carbon dioxide from the satellites," he said.

Russia's invasion of Ukraine in 2022 and the geopolitical uncertainty has led to a freeze in relations between the EU agency and Russia, which has increased the importance of the Finnish input, according to Cheli.

"Of all the data on the Arctic, we are missing half of the data set in terms of ground truth validation. Siberia is no longer accessible to do that exercise," she said.

"Countries like Finland are therefore becoming more and more important for validating satellite data on the ground. It's becoming a central strategic infrastructure," Cheli said, citing Finland's geographical location near the Russian border.