Evaluating the Retreat, Stabilization, and Regrowth of Crane
Glacier against Marine Ice Cliff Process Models
C. Needell1 and N. Holschuh1*
1Department of Geology, Amherst College, Amherst, MA,
USA
*Corresponding author: Nicholas Holschuh
(nholschuh@amherst.edu)
Key Points (must be < 140 characters):
- Calving of Crane Glacier’s terminus after the collapse of the Larsen B
Ice Shelf accelerated by 55% from 2002 until it arrested in 2004.
- 6.74 ± 0.03 km of the 10.05 km retreat occurred in floating ice, with
cliff failure possible during the final phase assuming weak ice.
- Crane’s retreat into a narrow fjord and sea-ice growth re-established
buttressing stresses and reversed terminus retreat.
Abstract
The fastest projected rates of sea level rise appear in models which
include “the marine ice cliff instability (MICI),” a hypothesized but
mostly unobserved process defined by rapid, brittle failure of terminal
ice cliffs that outpaces viscous relaxation and ice-shelf formation.
Crane Glacier’s response to the Larsen B Ice Shelf collapse has been
invoked as evidence of MICI, but sparse data coverage of that event in
space and time has hindered interpretation of the processes controlling
terminus retreat. Using available remote sensing data, we deconstruct
Crane’s retreat, arrest, and regrowth over the last two decades. Much of
Crane’s terminus retreat occurred in floating, not grounded ice, but
calving accelerated by at least 55% during the 2 years following ice
shelf collapse, consistent with a positive geometric feedback. If
calving occurred by cliff failure, maximum cliff heights would have been
111 m, only consistent with process models that incorporate damaged ice.