Present-day environmental dynamics in ice cave A294, Central Pyrenees, Spain

Abstract

Several ice caves have been discovered in the Pyrenees. Among them, cave A294 hosts one of the most interesting ice deposits, which is mainly composed of firn ice. This paper investigates the present-day climate dynamics and the isotopic composition of precipitation, dripping water and ramp snow) to evaluate the palaeoclimatic potential of the ice cave deposit. The cave experiences a chimney effect during the winter but acts as a thermal trap during the summer. Four climate phases with mean annual temperatures ranging from –0.77 to 0.26ºC have been interpreted along the year. At present-day conditions, even though some congelation ice forms annually, the ice has a negative mass balance with an annual ice loss of ca. 12 m3 that mainly affects the walls of the ice deposit. The seasonal variability of the stable isotopic (δ¹⁸O and δD) composition of dripping water and ramp snow has a smaller amplitude compared to that of the precipitation (rain and snow). The data show a good correlation (r²=0.94) and match the Global Meteoric Water Line. We hypothesise that the metamorphosis of snow into ice causes no significant postdepositional alteration, and thus the ice from cave A294 may be used as a reliable palaeoclimatic archive. Given the reduced volume of ice deposits in the region and their rapid melting, it is extremely urgent to study the ice record in cave A294.