Lateglacial paleoglacier and paleoclimate reconstructions in the north-western Italian Alps. (15th December 2022)

• Record Type: Journal Article
• Authors: Serra, Elena; Magrani, Fabio; Valla, Pierre G.; Gribenski, Natacha; Carcaillet, Julien; Lundbek Egholm, David
• Is Part Of: Quaternary science reviews. Volume 298(2022)
• Publication Date: 2022-12-15
• Subjects: Lateglacial -- 10Be cosmogenic dating -- Glacier modelling -- Paleoclimate reconstruction -- Western European Alps; Geology, Stratigraphic -- Quaternary -- Periodicals; Stratigraphie -- Quaternaire -- Périodiques; 551.79
• DOI: 10.1016/j.quascirev.2022.107822
• Languages: English
• ISSNs: 0277-3791

Abstract

Abstract: Lateglacial (19.0–11.7 ka ago) paleo-temperature records in the Western European Alps document several short-term cooling episodes within the general post-Last Glacial Maximum warming trend, in phase with North Hemisphere climatic oscillations. Alpine paleo-precipitation reconstructions are instead rare, and further constraints are needed in order to assess whether Lateglacial cold periods were associated with a modified atmospheric circulation pattern over the European Alps. The Alpine paleoglacial record offers a quantitative framework to investigate Lateglacial paleoclimatic conditions and glacier sensitivity in response to both temperature and precipitation changes. Through the combination of 10 Be surface-exposure dating of glacial landforms and deposits constraining ice front and surface, together with numerical glacier simulations (iSOSIA), our study aims to reconstruct in space and time the main Lateglacial ice stages and associated paleo-climatic conditions in three tributary valleys (Valpelline, Valsavarenche and Val di Cogne) located within the Dora Baltea catchment (north-western Italian Alps). Our dating-modelling approach reveals in all the three investigated sectors two distinct paleoglacier stages at ca. 13 and 11 ka, documenting respectively the ice configurations at the transition between the Oldest Dryas cold period and the Bølling-Allerød interstadial, and between the Younger Dryas cold period and the early Holocene warming. Numerical ice-simulation outcomes suggest a similar-to-today precipitation pattern during the two ice stages, with either same absolute or homogeneously decreased precipitation values over the Dora Baltea catchment, although a unique quantitative solution of paleo-precipitation magnitudes could not be constrained from our dataset. Using present-day precipitation pattern and magnitude, our results provide paleo-temperature offsets from present-day between −3.3 and −3.8 °C for the older glacial stage, and −2.7 to −3.2 °C for the younger glacial stage, coinciding with the upper range of paleo-temperature reconstructions from other paleoclimatic proxies. Finally, Alpine glaciers' sensitivity to climate fluctuations differ significantly between the investigated catchments, with a much higher glacier sensitivity to changes in the Equilibrium Line Altitude in the northern (Valpelline) compared to the southern (Valsavarenche and Val di Cogne) tributaries, reflecting different topographic and/or climatic conditions between the three valleys. Highlights: Combining dating and modelling, we investigated paleo-glaciers and -climate in the Dora Baltea catchment (NW Italian Alps). We reconstructed two Lateglacial ice stages (∼13 and 11 ka) documenting the end of the Oldest and Younger Dryas cold periods. Precipitation patterns during the two stages were similar to today, with same absolute or homogeneously decreased values. Paleo-temperature offsets from present-day were between -3.3 to -3.8°C and -2.7 to -3.2°C for the older and younger stages. Glaciers' climate sensitivity varies significantly between tributaries reflecting topographic and local climatic differences.