A Lagrangian analysis of the dynamical and thermodynamic drivers of large-scale Greenland melt events during 1979–2017 ...

• Main Authors: Hermann, Mauro, Papritz, Lukas, Wernli, Heini
• Format: Article in Journal/Newspaper
• Language: English
• Published: ETH Zurich 2020
• Subjects: East Greenland; Greenland; Ice Sheet
• Online Access: https://dx.doi.org/10.3929/ethz-b-000456721; http://hdl.handle.net/20.500.11850/456721

In this study, we systematically investigate the dynamical and thermodynamic processes that lead to 77 large-scale melt events affecting high-elevation regions of the Greenland Ice Sheet (GrIS) in June–August (JJA) 1979–2017. For that purpose, we compute 8 d kinematic backward trajectories from the lowermost ∼500 m above the GrIS during these events. The key synoptic feature accompanying the melt events is an upper-tropospheric ridge southeast of the GrIS associated with a surface high-pressure system. This circulation pattern is favorable to induce rapid poleward transport (up to 40∘ latitude) of warm (∼15 K warmer than climatological air masses arriving on the GrIS) and moist air masses from the lower troposphere to the western GrIS and subsequently to distribute them in the anticyclonic flow over north and east Greenland. During transport to the GrIS, the melt event air masses cool by ∼15 K due to ascent and radiation, which keeps them just above the critical threshold to induce melting. The thermodynamic ... : Weather and Climate Dynamics, 1 (2) ...