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Geomorphic mapping and stratigraphic analysis of a lake core document the late Quaternary glacial history of the Central and Eastern Massifs of the Picos de Europa, northwestern Spain. The distribution of glacial deposits indicates that at their most advanced positions glaciers occupied 9.1 km2, extended as far as 7 km down-valley and had an estimated equilibrium-line altitude (ELA) ranging between 1666 and 1722 m. Radiocarbon dating of sediment deposited in a lake dammed by moraines of this advance show that the maximum glacial extent was prior to 35,280 ± 440 cal yr BP. This advance was followed by two subsequent but less extensive late Pleistocene advances, recorded by multiple moraines flanking both massifs and sedimentary characteristics in the lake deposits. The last recognized glacial episode is the 19th-century maximum extent of small Little Ice Age glaciers in the highest cirques above 2200 m.

This paper contributes to the study of permafrost in the Pyrenees by reporting geoelectrical investigations and thermal measurement on the Little Ice Age (LIA) forefields of two glaciers. The aim was to assess the internal composition of sedimentary bodies (debris rock glaciers and moraine deposits) located in this proglacial environment. Ground ice was prospected using two DC resistivity techniques: vertical electrical soundings and resistivity mapping at a fixed pseudo-depth. Extreme specific resistivities ranging between 1 and 25 M m were detected under a thin (1-2 m) unfrozen layer, indicating the presence of a massive ice layer, certainly buried glacier ice. This ice of glacial origin probably covers former permafrost bodies, i.e. a much thicker layer of perennially frozen sediments. Low subsurface temperatures measured on the deposits indicate that buried glacier ice could have been preserved on top of permafrost since the end of the LIA or earlier Holocene glacier advances. This stratigraphy demonstrates that glaciers and pre-existing perennially frozen sediments (permafrost) were in contact during the LIA.

Abstract. This paper reviews multi-proxy paleoclimatic reconstructions with robust age-control derived from lacustrine, dendrochronological and geomorphological records and characterizes the main environmental changes that occurred in the Southern Pyrenees during the last millennium. Warmer and relatively arid conditions prevailed during the Medieval Climate Anomaly (MCA, ca. 900-1300 AD), with a significant development of xerophytes and Mediterranean vegetation and limited deciduous tree formations (mesophytes). The Little Ice Age (LIA, 1300-1800 AD) was generally colder and moister, with an expansion of deciduous taxa and cold-adapted montane conifers. Two major phases occurred within this period: (i) a transition MCA-LIA, characterized by fluctuating, moist conditions and relatively cold temperatures (ca. 1300 and 1600 AD); and (ii) a second period, characterized by the coldest and most humid conditions, coinciding with maximum (recent) glacier advances (ca. 1600-1800 AD). Glaciers retreated after the LIA when warmer and more arid conditions dominated, interrupted by a short-living cooling episode during the late 19th to early 20th centuries. Some records suggest a response to solar activity with colder and slightly moister conditions during solar minima. Centennial-scale hydrological fluctuations are in phase with reconstructions of NAO variability, which appears to be one of the main climate mechanisms influencing rainfall variations in the region during the last millennium.