19 Sep 2022
19 Sep 2022
Status: a revised version of this preprint is currently under review for the journal TC.

Precursor of disintegration of Greenland's largest floating ice tongue

Angelika Humbert1,2, Veit Helm1, Niklas Neckel1, Ole Zeising1, Martin Rückamp3,1, Shfaqat Abbas Khan4, Erik Loebel5, Dietmar Gross6, Rabea Sondershaus7, and Ralf Müller7 Angelika Humbert et al.
  • 1Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Bremerhaven, Germany
  • 2University of Bremen, Department of Geosciences, Bremen, Germany
  • 3Geodesy and Glaciology, Bavarian Academy of Sciences and Humanities, Munich, Germany
  • 4DTU Space, National Space Institute, Technical University of Denmark, Department of Geodesy and Earth Observations, Copenhagen, Denmark
  • 5Technische Universität Dresden, Institut für Planetare Geodäsie, Dresden, Germany
  • 6Division of Solid Mechanics, Institute for Mechanics, Technical University of Darmstadt, Darmstadt, Germany
  • 7Division of Continuum Mechanics, Institute for Mechanics, Technical University of Darmstadt, Darmstadt, Germany

Abstract. The largest floating tongue of Greenland’s ice sheet, Nioghalvfjerdsbræ, has so far been relatively stable with respect to areal retreat. Curiously, it experienced significant less thinning and ice flow acceleration than its neighbour Zacharias Isbræ. Draining more than 6 % of the ice sheet, Nioghalvfjerdsbræ might become a large contributor to sea level rise in the future. Therefore, the stability of the floating tongue is a focus of this study. We employ a suite of observational methods to detect recent changes. We found that the calving style has changed at the southern part of the eastern calving front from normal tongue-type calving to a crack evolution initiated at frontal ice rises reaching 5–7 km and progressing further upstream compared to 2010. The calving front area is further weakened by a substantial increase of a zone of fragments and open water at the tongue’s southern margin, leading to the formation of a narrow ice bridge. These geometric and mechanical changes are a precursor of instability of the floating tongue. We complement our study by numerical ice flow simulations to estimate the impact of future break-up or disintegration events on the ice discharge. These idealised scenarios reveal that a loss of the south-eastern area would lead to 1 % of increase of ice discharge at the grounding line, while a sudden collapse of the frontal area (46 % of the floating tongue area) will enhance the ice discharge by 8.3 % due to loss in buttressing.

Angelika Humbert et al.

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Angelika Humbert et al.

Angelika Humbert et al.


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Short summary
The largest floating glacier mass in Greenland, the 79° N Glacier, is showing signs of an instability. We investigate how crack formation at the glaciers calving front has changed over the last decades by using satellite imagery and airborne data. The calving front is about to loose contact to stabilising ice islands. Simulations show that the glacier will accelerate as a result of this, leading to increase in ice discharge of more than 8 % if its calving front retreats by 46 %.