Articles | Volume 11, issue 2
The Cryosphere, 11, 937–948, 2017
The Cryosphere, 11, 937–948, 2017

Research article 13 Apr 2017

Research article | 13 Apr 2017

Linking pollen deposition and snow accumulation on the Alto dell'Ortles glacier (South Tyrol, Italy) for sub-seasonal dating of a firn temperate core

Daniela Festi1, Luca Carturan2, Werner Kofler1, Giancarlo dalla Fontana2, Fabrizio de Blasi2, Federico Cazorzi3, Edith Bucher4, Volkmar Mair5, Paolo Gabrielli6,7, and Klaus Oeggl1 Daniela Festi et al.
  • 1Institute of Botany, University of Innsbruck, Sternwartestraße 15, 6020 Innsbruck, Austria
  • 2Department of Land, Environment, Agriculture and Forestry, University of Padova, Viale dell'Università 16, 35020 Legnaro, PD, Italy
  • 3Department of Agriculture and Environmental Sciences, University of Udine, via delle Scienze 208, 33100 Udine, Italy
  • 4Autonome Provinz Bozen Südtirol, Landesagentur für Umwelt, Biologisches Labor, Unterbergstraße 2, 39055 Leifers, BZ, Italy
  • 5Autonome Provinz Bozen Südtirol, Amt für Geologie und Baustoffprüfung, Eggentalerstraße 48, 39053 Kardaun (BZ), Italy
  • 6Byrd Polar and Climate Research Center, Ohio State University, 1090 Carmack Road, Columbus, Ohio 43210-1002, USA
  • 7School of Earth Sciences, 275 Mendenhall Laboratory, Ohio State University, 125 South Oval 8 Mall, Columbus, OH 43210, USA

Abstract. Dating of ice cores from temperate non-polar glaciers is challenging and often problematic. However, a proper timescale is essential for a correct interpretation of the proxies measured in the cores. Here, we introduce a new method developed to obtain a sub-seasonal timescale relying on statistically measured similarities between pollen spectra obtained from core samples and daily airborne pollen monitoring samples collected in the same area. This approach was developed on a 10 m core retrieved from the temperate-firn portion of Alto dell'Ortles glacier (Eastern Italian Alps), for which a 5-year annual/seasonal timescale already exists. The aim was to considerably improve this timescale, reaching the highest possible temporal resolution and testing the efficiency and limits of pollen as a chronological tool. A test of the new timescale was performed by comparing our results to the output (date of layer formation) of the mass balance model EISModel, during the period encompassed by the timescale. The correspondence of the results supports the new sub-seasonal timescale based on pollen analysis. This comparison also allows us to draw important conclusions on the post-depositional effects of meltwater percolation on the pollen content of the firn core as well as on the climatic interpretation of the pollen signal.

Short summary
We propose a sub-seasonal timescale based on pollen analyses for a Mt. Ortles firn core. The method can be applied to all types of glaciers, provided the proximity of the pollen source and a negligible time lag between pollen production and its deposition on the glacier. By combining pollen dating with a mass balance model we found evidence that pollen grains are resilient to downward transport by percolating water and that pollen shows a high potential for inferring past climatic conditions.