Significant mass loss in the accumulation area of the Adamello glacier indicated by the chronology of a 46\u2009m ice core

Abstract

Abstract. Dating glaciers is an arduous yet essential task in ice core\nstudies, which becomes even more challenging when the glacier is\nexperiencing mass loss in the accumulation zone as result of climate\nwarming, leading to an older ice surface of unknown age. In this context, we\ndated a 46\u2009m deep ice core from the Central Italian Alps retrieved in 2016\nfrom the Adamello glacier in the locality Pian di Neve (3100\u2009m\u2009a.s.l.). Here\nwe present a timescale for the core obtained by integrating results from the\nanalyses of the radionuclides 210Pb and 137Cs with annual layer\ncounting derived from pollen and refractory black carbon concentrations. Our\nresults clearly indicate that the surface of the glacier is older than the\ndrilling date of 2016 by about 20 years and that the 46\u2009m ice core reaches\nback to around 1944. For the period of 1995–2016 the mass balance at the\ndrilling site (former accumulation zone) decreased on average of about 1\u2009m\u2009w.e.\u2009a−1 compared to the period 1963–1986. Despite the severe mass loss\naffecting this glacier even in the former accumulation zone, we show that it\nis possible to obtain a reliable timescale for such a temperate glacier\nusing black carbon and pollen seasonality in combination with radionuclides\n210Pb and 137Cs. Our results are therefore very encouraging and\nopen new perspectives on the potential of such glaciers as informative\npalaeoarchives.\n