Modelling the isotopic composition of snow using backward trajectories: a particular precipitation event in Dronning Maud Land, Antarctica

• Published in: Annals of Glaciology
• Main Authors: Helsen, Michiel, van de Wal, Roderik, van den Broeke, Michiel, Kerstel, Erik, Masson-Delmotte, Valérie, Meijer, Harro, Reijmer, Carleen, Scheele, Marinus
• Other Authors: Institute for Marine and Atmospheric Research Utrecht (IMAU), Universiteit Utrecht / Utrecht University Utrecht, Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Centre for Isotope Research Groningen (CIO), University of Groningen Groningen, Royal Netherlands Meteorological Institute (KNMI)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2004
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; Annals of Glaciology; Antarc*; Antarctica; Dronning Maud Land
• Online Access: https://hal.science/hal-03103979; https://hal.science/hal-03103979/document; https://hal.science/hal-03103979/file/fichier3.pdf; https://doi.org/10.3189/172756404781814230

International audience We consider a specific accumulation event that occurred in January 2002 in western Dronning Maud Land, Antarctica. Snow samples were obtained a few days after accumulation. We combine meteorological analyses and isotopic modelling to describe the isotopic composition of moisture during transport. Backward trajectories were calculated, based on European Centre for Medium-Range Weather Forecasts operational archive data so that the history of the air parcels transporting water vapour to the accumulation site could be reconstructed. This trajectory study showed that the air masses were not (super)saturated along most of the transport path, which is in contrast with assumptions in Lagrangian fractionation models and probably true for most precipitation events in Antarctica. The modelled fractionation along the trajectories was too limited to explain the measured isotopic content of the snow. It is shown that the observed isotopic composition of precipitation resulted from fractionation of initially more depleted water. This lower initial isotopic composition of water vapour might result from atmospheric mixing with more depleted air along the trajectory or from earlier condensation cycles, not captured by the trajectories. This is in accordance with isotope fields resulting from general circulation models, indicating a gradient in isotopic composition from the Equator to Antarctica.