Monitoring permafrost and periglacial processes in Sierra Nevada (Spain) from 2001 to 2016

Outside the Alps, the Sierra Nevada is probably the best studied European massif with respect to its past and current environmental dynamics. A multi‐approach research program started in the early 2000s focused on the monitoring of frozen ground conditions in this National Park. Here, we present data on the thermal state and distribution of permafrost and seasonal frozen ground in different sites across the highest areas of the massif. New results confirm the absence of widespread permafrost conditions, with seasonal frost prevailing above 2500 m. Small permafrost patches have been only detected in glaciated areas of the Veleta and Mulhacen cirques during the Little Ice Age at elevations of 3000–3100 m. The remnants of those glaciers are still preserved under the thick debris layer covering the cirque floors. Geomatic and geophysical surveying of a rock glacier existing in the Veleta cirque, together with the monitoring of soil temperature at different depths, have revealed permanently frozen conditions undergoing a process of degradation. In the rest of the massif, a seasonal frost regime prevails, even at the highest plateaus at 3300–3400 m, where annual soil temperatures average 2.5°C. The monitoring of soil temperatures in other different periglacial features has also revealed positive average values ranging between 2°C (inactive sorted‐circles) and 3–4°C (inactive and weakly active solifluction lobes). Consequently, we conclude that the present‐day climatic regime does not allow the existence of permafrost in the Sierra Nevada, and environmental dynamics is controlled by the intensity and duration of seasonal frost in the ground.