Cave monitoring and the potential for palaeoclimate reconstruction from Cueva de Asiul, Cantabria (N. Spain)

Palaeoclimate records from northern Iberia are becoming increasingly sought after as this region is one of the most southerly terrestrial locations in Europe to have its climate dictated principally by the North Atlantic. Terrestrial records therefore have the potential to offer insights into changing oceanic and atmospheric circulation in the wider North Atlantic region. Cave speleothems offer one of the most promising archives from northern Iberia due to their wide geographic distribution and potential for accurately dated climate reconstruction. Cueva de Asiul, situated in Cantabria (N. Iberia; 43°19'0.63''N, 3°35'28.32''W; 285 m.a.s.l) within the Matienzo karst depression is one such site that offers the potential for palaeoclimate reconstructions. Here we present three years of climate and cave monitoring from Cueva de Asiul, giving detailed insight into local meteorology, hydrology and cave ventilation dynamics. In doing so, this paper presents a background to high resolution, Holocene duration speleothem records which have been extracted from this cave. Annual average cave temperatures are +13.7ºC, with a maximum range of 1ºC, reflecting the seasonality of external air temperature (average external temperature +13.8°C). Cave ventilation is controlled by changes in external air temperature and variations in external air pressure during low pressure events. Local rainfall measurements show an average of 1400 mm/year with the majority of rainfall occurring during the winter, with periods of water excess between October and April. Speleothem drip rates are characterised by summer lows and a rapid transition to higher rates at the onset of the winter season. Stable isotope analysis (δ18O, δ2H) indicate that aquifer water is derived predominantly from the previous year’s rainfall and the rainfall feeding the karst system is controlled by a strong amount effect. Speleothems from this site are potentially suited to preserving extended records of rainfall amount in northern Spain and therefore have the potential to inform more clearly about Holocene scale changes in the rainfall source region, the North Atlantic