Articles | Volume 14, issue 6
Research article
06 Jun 2018
Research article |  | 06 Jun 2018

Ground surface temperature reconstruction for the last 500 years obtained from permafrost temperatures observed in the SHARE STELVIO Borehole, Italian Alps

Mauro Guglielmin, Marco Donatelli, Matteo Semplice, and Stefano Serra Capizzano

Abstract. Here we present the results of the inversion of a multi-annual temperature profile (2013, 2014, 2015) of the deepest borehole (235 m) in the mountain permafrost of the world located close to Stelvio Pass in the Central Italian Alps. The SHARE STELVIO Borehole (SSB) has been monitored since 2010 with 13 thermistors placed at different depths between 20 and 235 m. The negligible porosity of the rock (dolostone,  <  5 %) allows us to assume the latent heat effects are also negligible. The inversion model proposed here is based on the Tikhonov regularization applied to a discretized heat equation, accompanied by a novel regularizing penalty operator. The general pattern of ground surface temperatures (GSTs) reconstructed from SSB for the last 500 years is similar to the mean annual air temperature (MAAT) reconstructions for the European Alps. The main difference with respect to MAAT reconstructions relates to post Little Ice Age (LIA) events. Between 1940 and 1989, SSB data indicate a cooling of ca. 1 °C. Subsequently, a rapid and abrupt GST warming (more than 0.8 °C per decade) was recorded between 1990 and 2011. This warming is of the same magnitude as the increase in MAAT between 1990 and 2000 recorded in central Europe and roughly doubling the increase in MAAT in the Alps.

Short summary
The reconstruction of ground surface temperature for the last 500 years, obtained at the deepest mountain permafrost borehole of the world (Stelvio Pass, 3000 m a.s.l., Italian Alps), is presented here. The main difference with respect to MAAT reconstructions obtained through other proxy data for all of Europe relates to post Little Ice Age (LIA) events. Indeed at this site a stronger cooling of ca 1 °C between 1940 and 1989 and even a more abrupt warming between 1990 and 2011 was detected.