Benjamin Lehmann

Research Statement

My research focuses on the evolution of mountains and the complexities of the earth surface processes that it involves. Past climate has modulated the thickness and the extent of alpine glaciers and ice caps. Therefore quantifying the spatial and temporal fluctuations in ice extent provides insights into past climate.

PhD topic

My PhD is about the quantification of the glacier erosion in the Western Alps (Mer de Glace glacier, Mont Blanc massif, France) during the last glacial (since Last Glacial Maximum to present day). The main objective of this project is the reconstruction of paleo-ice extent of the Mer de Glace glacier using a multi-method approach: optically stimulated luminescence (OSL) surface exposure dating and terristrial cosmogenic nuclide dating (TCN).

Methods

OSL surface exposure dating is sensitive to light, based on the progressive bleaching of the OSL signal in a rock sample that depends on its exposure time, mineralogical properties and environmental conditions. The longer a surface is exposed to sunlight, the deeper the bleaching is occuring, showing in alpine glacier setting a positive correlation between exposure age and elevation. The main advantages of this dating technic is to be able to reconstruct exposure history from decade to millennium, while having a high spatial resolution (low cost in prepation time) .

Biography

Coming from a mountain environment I have always been fascinated by the complexity of the evolution of this landscape and by natural processes (geological, glaciological, hydrological) that control it. In this context, I focused my academic training in the fields of geosciences. Graduated of a MSc in Solid Earth geosciences (Joseph Fourier university, Grenoble, France), I decided to focus my career on cryosphere tematics. I thus engaged myself in the scientific cooperation of the Glacioclim Observatory of La Paz, in Bolivia (www.great-ice.ird.fr). Over two years, I was responsible of the glaciological, meteorological and hydrological monitoring of glaciated drainage basins (Zongo and Charquini Sur). After this professional experience, I decided to engage myself in research to understand the feedback mechanisms between climate and earth surface processes in mountain environment.

Awards

  • EGU 2016: Outstanding Student Poster and PICO (OSPP) Awards 2016 – Benjamin Lehmann et al.: Reconstruction of glacier fluctuations in the Western Alps since the LGM using OSL surface exposure dating (Link & Poster)
  • UKLUM15: Student Poster Awards 2016 – Benjamin Lehmann et al.: Constraining post-LGM glacier fluctuations using OSL-surface exposure dating in the Western Alps (Abstract)

Publications and conference presentations

  • EGU 2017 – Talk: Benjamin Lehmann et al.: Reconstruction of glacier fluctuations in the Mont‐Blanc massif, western Alps: a multi‐method approach (Abstract)
  • SGM 2016 – Talk: Benjamin Lehmann et al.: Reconstruction of glacier fluctuations in the Mont-Blanc massif, western Alps: a multi-method approach (Abstract)
  • EGU 2016 – Poster: Benjamin Lehmann et al.: Reconstruction of glacier fluctuations in the Western Alps since the LGM using OSL surface exposure dating (Abstract)
  • SGM 2015 – Poster: Benjamin Lehmann et al.: OSL-surface exposure dating as a tool to constrain post-LGM glacier fluctuations in the Western Alps (Abstract)
  • UKLUM15 – Poster: Benjamin Lehmann et al.: Constraining post-LGM glacier fluctuations using OSL-surface exposure dating in the Western Alps (Abstract)

Contact

SNSF Doctoral Student
Université de Lausanne
Institute of Earth Surface Dynamics (IDYST)
le Géopolis – Bureau 3151
1015 Lausanne, Switzerland

Tel: +41 (0)21 692 3543
Skype: benjamin-lehmann