Spatial characterization of glacial and periglacial landforms in the highlands of Sierra Nevada (Spain)

Abstract

Sierra Nevada constitutes the southernmost and highest massif in the Iberian Peninsula, with elevations exceeding 3000m. Two large glacial advances were recorded during the Last Glaciation and several minor advances occurred until the Early Holocene. Since then, periglacial activity has prevailed above 2500m. Here, we present a new and more accurate geomorphological map of the highlands of Sierra Nevada, integrating in a GIS environment i) high resolution satellite imagery, ii) topographic data, and iii) field observations. This approach has allowed a better characterization of the spatial extent of cold-climate morphogenic processes and associated landforms formed during the Last Glaciation and subsequent deglaciation. Despite its extension and high altitude, the steep relief of Sierra Nevada and its southern location conditioned a significantly lower glaciated surface (104.6km) with respect to other Iberian massifs. We have also inferred the paleoclimatic conditions of the study area through the calculation of Equilibrium Line Altitudes (ELAs). The distribution of the lowest moraines suggests an ELA for the maximum glacial extent at 2525m in the northern slope and 2650m in the southern side, increasing towards the east. Local ELA differences are related to: (i) the influence of the warmer Mediterranean Sea in contrast to the cooler Atlantic Ocean, (ii) the climate with more continental characteristics on the northern slope, and (iii) the microscale control of the local topography. Mean annual air temperatures in the ice-free summit plateaus were between -4/-6°C during the maximum local glacial extent, determining permafrost conditions with intense periglacial dynamics. Rock glaciers and protalus lobes developed until 2500m, the lowest boundary for permafrost regime. The distribution of other glacial and periglacial landforms within the limits of the maximum ice extent provides evidence to better understand the extent of subsequent glacial stages and post-glacial landscape evolution in Sierra Nevada.

High-Resolution Monthly Precipitation Fields (1913–2015) over a Complex Mountain Area Centred on the Forni Valley (Central Italian Alps)

“…Qualitative reconstruction of the past climatic characteristics over long time scales is possible thanks to geomorphological and biological paleoclimatic indicators (e.g., typical features of glacial and periglacial environment, debris covered glaciers and rock glaciers, tree remnants under glacial deposits, and pollens) [19][20][21][22]. Quantitative reconstructions, instead, come from dendroclimatic analysis [23][24][25] or from meteorological observations that in Italy began to be collected regularly in the last decades of the XVIII century [26].…”

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

“…As suggested by mountain glacier models based on geomorphological evidence, during that phase summit plateaus must have remained mostly ice‐free due to the redistribution of snow by the wind, with an equilibrium line altitude located at 2525 m on the northern slope and 2650 m on the southern slope. This means that temperatures at the peaks were approximately −4 to −6°C, which suggests the existence of permafrost conditions . In some of these sectors, as in the Machos plateau, currently inactive meter‐sized sorted circles developed.…”

“…They are thus inherited features, as suggested by the presence of lichens and cryo‐xerophyte herbaceous vegetation at the surface. During the maximum ice extent of the Last Glaciation in the Sierra Nevada, there were also hillsides up to 2500 m high that were not glaciated, so they must have had a soil thermal regime of permafrost, as suggested by the existence of rock glaciers outside the glaciated environment …”

“…The current landscape, shaped in strata of Paleozoic micachists that were highly tectonized by the alpine orogeny, stands out due to the fact that it contains the southernmost glacial and periglacial landforms in Europe . Glacial activity reached maximum development in the high areas of the valleys, in their headwaters and slopes above 2500 m. Large cirques were carved by Quaternary glaciers, which deposited sediments in the valley bottoms forming different moraine systems above 1900–2000 m. According to 10 Be cosmogenic dates, sedimentary and erosive records show ages of glacial phases ranging from 135 ka to 300 years .…”

Multiproxy reconstruction of Holocene glaciers in Sierra Nevada (south Spain)

“…Oldest and Younger Dryas) (García-Ruiz et al 2016;Hughes and Woodward 2016;Palacios et al 2017;Ribolini et al 2017). In Sierra Nevada, south Spain, glacial activity followed a similar pattern: glaciers covered 105 km 2 during the maximum ice extent of the Last Glaciation with several km-long ice tongues flowing down the valleys (Palma et al 2017), but shrank dramatically at 20-19 ka and only expanded during the coldest phases of Termination-1 (Oliva et al 2014a;Palacios et al 2016).…”