Sedimentological and molecular responses of Greenlandic lakes to Holocene climate changes and pastoral activities

• Main Author: Guillemot, Typhaine
• Other Authors: Laboratoire Chrono-environnement - CNRS - UBFC (UMR 6249) (LCE), Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté COMUE (UBFC)-Université Bourgogne Franche-Comté COMUE (UBFC), Université de Franche-Comté, Hervé Richard, Vincent Bichet
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2015
• Subjects: Greenland; Holocene; Climate change; Lake sediments; Pastoral activity; Groenland; Changement climatique; Sédiments lacustres; Activité agro-pastorale; [SDV.EE]Life Sciences [q-bio]/Ecology; environment; Igaliku; Qallimiut; greenlandic; groenlandais
• Online Access: https://tel.archives-ouvertes.fr/tel-01682886; https://tel.archives-ouvertes.fr/tel-01682886/document; https://tel.archives-ouvertes.fr/tel-01682886/file/these_A_GUILLEMOT_Typhaine_2015.pdf

In the current context of global change, understanding the interactions between Human/Environment/Climate is necessary to develop adaptive strategies and preserve ecosystems. A retrospective approach is therefore realized in three lacustrine cores to reconstruct the paleo-environmental history during the last five millennia. Lake Igaliku (N61°00’22’’, W45°26’28’’), located at 2km from the medieval episcopal cathedral in the historical farming center, has a sedimentation mainly driven by anthropogenic activities. A complete molecular inventory has been made on this sequence to characterize past agropastoral dynamics and their impacts on south Greenlandic ecosystems. The identified fecal biomarkers revealed two agropastoral phases, during the Norse settlement and recently, separated by the Little Ice Age (LIA) and mainly characterized by sheep breeding. Vegetation molecular biomarkers (n-alkanes, triterpenyl acetates) and palynological data showed a reduction of trees and shrubs cover during these two periods especially. Erosion biomarkers (TTHCs) and sedimentological data identified only one drastic erosion in the 1980s synchronous with the mechanized creation of fodder parcels. Moreover, an eutrophication of the lake waters was recorded with short chain length n-alkanes and mesotrophic diatoms. Lake Qallimiut (N60°43’27’’, W45°23’12’’) and Little Kangerluluup (N60°38’32’’, W45°38’11’’), less impacted by anthropogenic activities, are fed by major streams influenced by hydrological variations. Their sedimentation is therefore mainly driven by climate changes. To improve the temporal and spatial resolution of climate changes during the Holocene, a multi-proxy sedimentological study was made on these two sites. Petrophysical, mineralogical and geochemical analyses have identified flood events especially occurring during cooler and wetter periods such as the Middle to Late Holocene transition (ca. 2500 BC), the Sub-boreal/Sub-atlantic transition (ca. 700 BC) and the LIA (between ca. AD 1300 et ca. AD 1900). These ...