Hydrological and Kinematic Precursors of the 2017 Calving Event at the Petermann Glacier in Greenland Observed from Multi-Source Remote Sensing Data

Abstract

Both a decrease of sea ice and an increase of surface meltwater, which may induce ice-flow speedup and frontal collapse, have a significant impact on the stability of the floating ice shelf in Greenland. However, detailed dynamic precursors and drivers prior to a fast-calving process remain unclear due to sparse remote sensing observations. Here, we present a comprehensive investigation on hydrological and kinematic precursors before the calving event on 26 July 2017 of Petermann Glacier in northern Greenland, by jointly using remote sensing observations at high-temporal resolution and an ice-flow model. Time series of ice-flow velocity fields during July 2017 were retrieved with Sentinel-2 observations with a sub-weekly sampling interval. The ice-flow speed quickly reached 30 m/d on 26 July (the day before the calving), which is roughly 10 times quicker than the mean glacier velocity. Additionally, a significant decrease in the radar backscatter coefficient of Sentinel-1 images suggests a rapid transformation from landfast sea ice into open water, associated with a decrease in sea ice extent. Additionally, the area of melt ponds on the floating ice tongue began to increase in mid-May, quickly reached a peak at the end of June and lasted for nearly one month until the calving occurred. We used the ice sheet system model to model the spatial-temporal damage and stress on the floating ice, thereby finding an abnormal stress distribution in a cracked region. It is inferred that this calving event may relate to a weakening of the sea ice, shearing of the tributary glacier, and meltwater infiltrating crevasses.

Ice Flow Velocity Mapping for Long-Time Motion Analysis of Typical Glaciers in Northwestern Greenland

“…Between 1999 and 2009, the ice front remained relatively stable, but in 2019, it retreated significantly, reaching a distance of 23 km. It is speculated that this retreat may have caused the glacier to disintegrate, which is consistent with the disintegration event reported in 2017 [17]. The ice front of the Humboldt Glacier had remained relatively stable, but since 1975, it has shown a trend of retreat.…”

Seawater Intrusion in the Observed Grounding Zone of Petermann Glacier Causes Extensive Retreat

“…We constrain the ice shelf velocity using Satellite observations from 2008 (Joughin et al., 2016) to 2020 (Millan et al., 2022). Our model does not allow for the evolution of damage during simulations, but there is substantial evidence of extensive cracking and rift formation across the ice shelf (Li et al., 2021; Millan et al., 2022; Rückamp et al., 2019). In order to ensure that these changes in ice shelf behavior are captured by the model, we constrain the ice velocity of the ice shelf 15 km downstream of the initial grounding line all the way to the ice front using observations.…”