A High Resolution, Three‐Dimensional View of the D‐28 Calving Event From Amery Ice Shelf With ICESat‐2 and Satellite Imagery

Abstract

Tabular calving events occur from Antarctica's large ice shelves only every few decades, and are preceded by rift propagation. We used high‐resolution imagery and ICESat‐2 data to determine the propagation rates for the three active rifts on Amery Ice Shelf (AIS; T1, T2, and E3) and observe the calving of D‐28 on September 25, 2019 along T1. AIS front advance accelerated downstream of T1 in the years before calving, possibly increasing stress at the rift tip. T1 experienced significant acceleration for 12 days before calving, coinciding with a jump in propagation of E3. ICESat‐2's high resolution and repeat acquisitions every 91 days allowed for analysis of the ice front before and after calving, and rift detection where it was not visible in imagery as a ∼1 m surface depression, suggesting that it propagates as a basal fracture. Our results show that ICESat‐2 can provide process‐scale information about iceberg calving.

Finding Antarctica’s Pole of Inaccessibility

“…The relevant geometry of the Amery Ice Shelf is more complex, and the shift is larger but again appears to be real. No major calvings occurred from the Amery Ice Shelf between 1964 and 2019 (Walker, Becker, & Fricker, 2021) and its behaviour during the time represented by this investigation was generally northwards expansion. The revision dates of the coastlines are not quite the same in all cases.…”

“…We believe it is reasonable to assume that these positions are all accurate to within something of the order of 1 km, so that the rate of change is meaningfully different from zero. Although the latest data available for the T1 point are from 2007, the Amery Ice Shelf's boundary was relatively unchanged until the calving of iceberg D28 in 2019 (Walker et al 2021), which implies that the movement of the outer SPI would have been relatively constant during this period.…”

Buoyancy‐Driven Flexure at the Front of Ross Ice Shelf, Antarctica, Observed With ICESat‐2 Laser Altimetry

“…Thus, we require additional information about the geometry of the bench to fully characterize the relationship between H and dx RM . The evolution of both dh RM and dx RM may also be related to local rheology and the profile of ice and firn density, as well as preexisting topography associated with rifts (Walker et al, 2021). 2.…”

“…For the largest ice shelves (Ross (Figure 1a), Filchner‐Ronne, and Amery), which are underlain by cold water and currently near steady state, multidecadal mean mass loss through iceberg production is estimated to exceed loss through basal melting (Depoorter et al., 2013; Rignot et al., 2013). The calving flux for these ice shelves is dominated by intermittent production of large (tens of kilometers long) tabular icebergs every few decades (e.g., Fricker et al., 2002; Lazzara et al., 1999; Walker et al., 2021). The extent and timing of these calving events are controlled by the lateral extension of full‐thickness rifts to the ice front.…”

Analysis of Temporal and Spatial Variability of Fronts on the Amery Ice Shelf Automatically Detected Using Sentinel-1 SAR Data

“…After the D28 detachment, the mass loss of AIS was approximately 315 billion tonnes due to the iceberg calving at the front, which, in addition to the basal melting underneath, is the key mass loss process. An AIS front advance will increase stress at the rift [2]. Before the D28 detachment, five rifts were actively propagated near the AIS front among seven active rifts over the 13 ice shelves in Antarctica, where most active rifts were initiated at the Amery Ice Shelf fronts [3][4][5].…”