Precursor of disintegration of Greenland's largest floating ice tongue

Abstract

Abstract. The largest floating tongue of Greenland’s ice sheet, Nioghalvfjerdsbræ, has been relatively stable with respect to areal retreat until 2022. Draining more than 6 % of the ice sheet, a disintegration of Nioghalvfjerdsbræ's floating tongue and subsequent acceleration due to loss in buttressing are likely to lead to sea level rise. Therefore, the stability of the floating tongue is a focus of this study. We employed a suite of observational methods to detect recent changes at the calving front. We found that the calving style has changed since 2016 at the southern part of the eastern calving front, from 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 an area upstream of the main calving front that consists of open water and an ice mélange that has substantially expanded, leading to the formation of a narrow ice bridge. These geometric and mechanical changes may be a precursor of instability of the floating tongue. We complement our study by numerical ice flow simulations to estimate the impact of future ice-front retreat and complete ice shelf disintegration on the discharge of grounded ice. These idealized scenarios reveal that a loss of the south-eastern area of the ice shelf would lead to a 0.2 % increase in 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 5.1 % due to loss in buttressing. Eventually, a full collapse of the floating tongue increases the grounding line flux by 166 %.

Atlantic Water warming increases melt below Northeast Greenland’s last floating ice tongue

“…However, it has been thinning in the last decade 5 , 6 . A recent study based on remote sensing data detected changes in the calving front, which indicate an onset of destabilization 38 . A retreat accompanied by a reduction in buttressing is thought to increase the ice discharge upstream with implications for global sea level rise.…”

The atmosphere-land/ice-ocean system in the region near the 79N Glacier in Northeast Greenland: Synthesis and key findings from GROCE

“…To assess the upper-end effect of the ice discharge of the 79NG on sea level change we conduct a series of model simulations of three scenarios by a subsequent removal of increasingly larger frontal parts of the 79NG floating tongue up to a full collapse (i.e. the removal of the entire tongue), following Humbert et al (2023). The simulations using the ice sheet model ISSM (Larour et al, 2012) and the initial state are based on a joint inversion for the basal friction coefficient on grounded ice and the ice hardness in floating ice.…”

“…We investigated the impact of a possible disintegration of the floating tongue of the 79NG on the solid ice discharge based on a high-resolution setup of the ISSM model (Humbert et al, 2023). For the 79NG Mouginot et al (2015) provide an annual mean estimate of ice discharge across the grounding line of 12.0 ± 0.8 Gt a −1 for the period 2010-2015 based on remote sensing data.…”

Fractures in glaciers—Crack tips and their stress fields by observation and modeling

“…The true orthophoto processing follows the common photogrammetric approach and with a given surface topography of the glacier, a mosaicing of the individual images is conducted. More details of the MACS‐Polar system can be found in [3]. The resulting mosaic of a crack tip is presented in Figure 2(B).…”

“…A detailed analysis of the crack and the calving front (Figure 2B) was conducted in [3] and has shown that this crack is also a mode I crack. Therefore, it is comparable to the situation of the crevasse field.…”