Permafrost, the ground below the freezing point of water 0 º for two or more years, is an element of the cryosphere which has not been as much studied as other soils like glaciers or marine ice, although it plays an important role in the climate evolution of the planet and in several human activities. Now, for the first time, a review of the state of permafrost on Earth has been carried out thanks to the data analysis of more than 120 drillings distributed around the Arctic and the Antarctica, as well as in mountains and high plains worldwide.

The study, titled "Permafrost is warming at a global scale" has been published in the journal Nature Communications, and is led by the researcher Boris Biskaborn, from the Alfred Wegener Institute for Polar and Marine Research (Germany). Among the collaborators of the study is Marc Oliva, coordinator of the Research Group Antarctic, Arctic and Alpine Environments (ANTALP), from the University of Barcelona

The analysed data were stored in the Global Terrestrial Network for Permafrost, an international initiative promoting the homogenization of data gathering on permafrost monitoring. The obtained data from 2007 to 2016 show that soil temperatures of continuous permafrost raised by 0,39 ± 0,15 °C, while discontinuous permafrost warmed by 0,20 ± 0,10 °C. In high mountains, the permanent frozen soil temperature rose by 0,19 ± 0,05 °C and the few existing holes in the Antarctica show a rise of temperatures of the order 0,37 ± 0,10 °C. The temperature of the terrestrial permafrost is estimated to have increased by 0,29 ± 0,12 ° C.

The presence or absence of permafrost in the ground conditions the ecosystems of many areas located in high mountains and latitudes. Permafrost melting causes the release of carbon dioxide and methane, with its consequences, which speed up global warming. Also, this melting can cause the collapse of buildings that have built on it. It should be borne in mind, for instance, that more than 60 % of Russian territory is placed on permafrost areas, like a part of the terrestrial area in the Northern hemisphere. Therefore, this temperature rise of the frozen ground can have social and economic consequences at a local and regional scale, losing equipment, damaging infrastructures, eroding the coast, etc., apart from other implications for the global climate.

The published study in Nature Communications is connected to another study led by researcher Marc Oliva which shows that, due the rise of heat over the last decades, permafrost is only kept in the highest mountain areas in the Mediterranean basin, such as some areas in the Pyrenees, Southern Alps, the Apennines, and the Anatolia mountains, apart from some isolated areas in the Picos de Europa, Sierra Nevada, Atlas mountains and the Balkans. In Catalonia, there is only permafrost in the mountains of Besiberri, and all areas show signs of degradation, which makes it possible for it to disappear during the next decades.

This study was published in Earth-Science Reviews and gathers twenty experts from different areas of the Mediterranean area. For the first time, the conditions of permafrost in southern Europe mountain areas for the last 20,000 years have been reconstructed. The study analyses the evolution of permafrost going from the last glaciation to current date, in a geographical area ranging from the Iberian Peninsula to the Anatolian one, including the north of Africa and the Mediterranean islands. Its conclusion states that, since the last glaciation, the areas that were occupied by permafrost in the Mediterranean mountains have diminished gradually and only some mountains have recovered permafrost during the coldest phases, such as the Little Ice Age (1300-1800 AC). Since then, global warming made permafrost to be found only in the highest areas of Mediterranean mountains.

Over the next years, the members of the ANTALP research group will work on the study of cold processes in the Catalan Pyrenees, where some permafrost remains, although its distribution and expansion is still not widely known. Also, in the International Permafrost Association (IPA) meeting with the Scientific Committee on Antarctic Research (SCAR), Marc Oliva was appointed Spanish representative and co-president of the initiative Antarctic Permafrost, Periglacial Environments and Soil (ANTPAS). The UB researcher notes "everything has to contribute to and promote the study of cold ecosystems in Catalonia, and make the University of Barcelona a model institution in this topic in Southern Europe".

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