New results of fossil glacial ice and permafrost evolution in Sierra Nevada

Since 2001, information about the evolution of this area fossil ice and permafrost has been collected; that is why the rock glacier located at the Western side of Corral del Veleta, at 3,150 metres high, has been taken as a reference. The main stretch of this area has been monitored and every year, during the last week of August, several parameters are measured: first, the thermic temperature regime of the active layer, by five sensors on a two metres area; second, rock body mobility, by 27 metal bars anchored; and third, the level of snow which covers the area in summer, by photogrammetry.

The instability of glacierʼs main stretch has enabled researchers to determine the volume of fossil ice and permafrost loss. The results obtained for the period 2001-2012 show a volume of 10,060.15 cubic metres in an area of 3,815 square metres. It is necessary to consider that these numbers are approximate as data are estimated taking into account that fossil ice and permafrost are distributed in a homogeneous way and have a similar thickness along all the area. The research group doubts about the fulfilment of these conditions, especially taking into account the results obtained from the last electrical tomography carried out in 2009. If these results are compared with the ones got in 1999, an important decrease of internal ice bodies and a smaller spatial distribution are observed.

Annual monitoring of fossil ice and permafrost degradation shows that this process is constant in time but variable in magnitude. For example, in 2003-2004 period 270.8 cubic metres of ice bodies were melt, but in 2004-2005 this number was increased up to 2,121.1 cubic metres. About the thermic temperature regime for these two periods, it is important to mention that in 2003-2004 there were 25 of days with positive temperatures on the active layer (May-August), whereas in 2004-2005 there were 105, out of a total of 123 days. And about the permanence of snow on the ground, it is necessary to indicate that in the last week of August, when data are measured, in 2004 there was snow in about 60 % of the western part of the area of Corral del Veleta, and it covered a great part of the rock glacierʼs surface, whereas in 2005, in middle June, there was not any snow left.

Snow plays a major role in the expansion of thermal pulse on groundʼs active layer. This fact was better proved during the summers of 2010 and 2011, when all the area of Corral de la Veleta was covered with snow, a layer of about two metres thick. This situation proved snowʼs major role in the process of fossil ice and permafrost degradation. Thermic data from November 2009 to June 2012 corroborate it: the middle area of the rock glacier has negative temperatures during these 32 months (between -0,2 ºC and -2 ºC), and the process of glacial ice and permafrost degradation stopped. However, in the summer of 2012, the process began again as ground was not covered with snow in summer. The observations made during the last week of August in 2012 showed again collapses on the surface of the rock glacier, as the process of glacial ice and permafrost degradation was reactivated. It is estimated that the volume of ice bodies melt could be of 1,182.6 cubic metres.

Researchers affirm that these data prove the series of physical processes which began with the external radiation which affects the ground and gets to the upper part of fossil ice and permafrost and degrades them. Ice bodiesʼ degradation occurs in summer, in a few weeks, and it has been stressed since Sierra Nevada summits are covered with snow during less time.

Corral del Veletaʼs glacier was formed during the Little Ice Age, a period of cooling that occurred from mid-14th to mid-19th centuries. In fact, the information we have about this glacier dates from 17th to mid-20th centuries. It is important to remark that Sierra Nevada was, during the Quaternary and the Little Ice Age, the most southern European mountain range that had glaciers. Professor Antonio Gómez Ortiz stresses the scientific interest of these new results of the evolution of glacial ice and permafrost in Sierra Nevada, as they can be used as a model to better explain periglacial processes in Mediterranean high mountains. The expert also remarks the importance of these results to monitor climate in this western Mediterranean area, especially to study ecosystemsʼ dynamics.

This year the research in Sierra Nevada, coordinated by the Consolidated Research Group on Landscape and Mediterranean Mountain Paleoenviroment and the Service of Landscape Management and Evolution of the UB, goes on thanks to the support given by the Ministry of Economy and Competitiveness, Sierra Nevada National Park, Certursa Sierra Nevada and the Agency for Management of University and Research Grants (AGAUR) of the Government of Catalonia. It is a multidisciplary and inter-university project that has the participation of researchers from the Complutense University of Madrid, the University of Extremadura, the University of Lisbon, the University of Granada, the University of Almeria and the University of Barcelona, which coordinates it.