Dendroclimatic temperature record derived from tree ring width of the oldest living wood in the Southern Rhaetian Alps (Ortles Cevedale Group, Italy).

The rising of the global mean temperatures with an unprecedented historically recorded rate is well documented and undeniable. In order to put the current temperatures in a long-term context and to better understand the ongoing climate change, instrumental and proxy data can be used. Nevertheless, the alpine regions often lack high altitude instrumental data and global data-sets could not accurately reproduce the temperature variations at the local scale. The Alpine chain represents a key site for understanding climatic interaction between Atlantic, Mediterranean and continental climatic conditions. Dendroclimatology allows to reconstruct long-term temperature variations in regions where local climate data exceeding one hundreds of years are not available. The “Bosco Antico” trees, belonging to the most ancient living wood of the Ortles-Cevedale area, can be considered quiet witnesses of climate variation since the earlier phases of the Little Ice Age. The derived composite chronology here presented offers a six hundred years-long dataset that records the temperature variations at seasonal resolution in Val di Sole area (Southern Rhaetian Alps, Italy). The analysis, carried out on earlywood, latewood and tree-ring width separately, pointed out that the all the chronologies are linked with June, July and August temperatures in mid-term variations. Considering the year-to year variability, instead, tree-ring and earlywood are more influenced by June temperatures whereas the latewood width is mainly driven by June and July temperatures. Our data furnish a mean summer latewood-based temperature reconstruction since 1525 A.D. The reconstruction perfectly catches the main temperature variations occurred in the last six centuries lengthening previously proposed local chronologies by about one hundred years. Main cold phases are highlighted during the 19th century and at the beginning of the 18th century tentatively ascribable to Dalton and Maunder solar stasis. Our results furnish a new dendroclimatic dataset for the Southern Rhaetian Alps that contribute to better understand the climate dynamics of this peculiar key site and improve both local and regional climate reconstructions. The comprehension of the local temperature variations at the annual resolution offer a key of interpretation of the response of glaciers to the rising temperatures. References Cerrato, R., Salvatore, M.C., Brunetti, M., Coppola, A., Baroni, C., 2018. Dendroclimatic relevance of “Bosco Antico”, the most ancient European larch living wood in Southern Rhaetian Alps (Italy). Submitted to Geografia Fisica e Dinamica Quaternaria. Leonelli, G., Coppola, A., Baroni, C., Salvatore, M.C., Maugeri, M., Brunetti, M., Pelfini, M., 2016. Multispecies dendroclimatic reconstructions of summer temperature in the European Alps enhanced by trees highly sensitive to temperature. Clim. Change 137, 275–291. https://doi.org/10.1007/s10584-016-1658-5 Coppola, A., Leonelli, G., Salvatore, M.C., Pelfini, M., Baroni, C., 2013. Tree-ring-based summer mean temperature variations in the Adamello-Presanella Group (Italian Central Alps), 1610-2008 AD. Clim. Past 9, 211–221. https://doi.org/10.5194/cp-9-211-2013 Coppola, A., Leonelli, G., Salvatore, M.C., Pelfini, M., Baroni, C., 2012. Weakening climatic signal since mid-20th century in European larch tree-ring chronologies at different altitudes from the Adamello-Presanella Massif (Italian Alps). Quat. Res. 77, 344–354. https://doi.org/10.1016/j.yqres.2012.01.004