Work

Physical processes controlling the rifting of Larsen C Ice Shelf, Antarctica, prior to the calving of iceberg A68

Year: 2021

Type: article

Abstract: The sudden propagation of a major preexisting rift (full-thickness crack) in late 2016 on the Larsen C Ice Shelf, Antarctica led to the calving of tabular iceberg A68 in July 2017, one of the largest icebergs on record, posing a threat for the stability of the remaining ice shelf. As with other ice shelves, the physical processes that led to the activation of the A68 rift and controlled its propagation have not been elucidated. Here, we model the response of the ice shelf stress balance to ice shelf thinning and thinning of the ice mélange encased in and around preexisting rifts. We find that ice shelf thinning does not reactivate the rifts, but heals them. In contrast, thinning of the mélange controls the opening rate of the rift, with an above-linear dependence on thinning. The simulations indicate that thinning of the ice mélange by 10 to 20 m is sufficient to reactivate the rifts and trigger a major calving event, thereby establishing a link between climate forcing and ice shelf retreat that has not been included in ice sheet models. Rift activation could initiate ice shelf retreat decades prior to hydrofracture caused by water ponding at the ice shelf surface.

Source: Proceedings of the National Academy of Sciences

DOI: 10.1073/pnas.2105080118

Authors: E. Larour, E. Rignot, M. Poinelli, B. Scheuchl

Institutions: California Institute of Technology, Jet Propulsion Laboratory, University of California, Irvine, Delft University of Technology

Language: English

Topic: Cryospheric studies and observations

Subfield: Atmospheric Science

Field: Earth and Planetary Sciences

Domain: Physical Sciences

SDG: Climate action

Open Access status: hybrid

Funders: National Aeronautics and Space Administration, California Institute of Technology, European Space Agency, U.S. Geological Survey, University of California, Irvine

Award: THE ICE SHEETS IN ANTARCTICA AND GREENLAND ARE CONTRIBUTING SOONER AND MORE SIGNIFICANTLY TO SEA LEVEL RISE THAN ANTICIPATED. TO UNDERSTAND THESE CHANGES AND PROJECT THE CONTRIBUTION OF ICE SHEETS TO SEA LEVEL CHANGE IN THE COMING DECADES TO CENTURIES IT IS ESSENTIAL TO OBTAIN COMPREHENSIVE CONTINUOUS OBSERVATIONS OF ICE SHEET DYNAMICS WHICH IS THE DOMINANT VECTOR OF RAPID SEA LEVEL RISE AT PRESENT AND IN THE FUTURE. OUR PROJECT ADDRESSES ANTARCTICA AND ITS 55-M SEA LEVEL EQUIVALENT. WE WILL EMPLOY A NEWLY AVAILABLE NEARLY CONTINUOUS MULTIPLESENSOR SATELLITE DATA STREAM OF ANTARCTIC OBSERVATIONS FROM THE USGS S LANDSAT-8 ESA'S SENTINEL-1A/B CSA'S RADARSAT-2 AND OTHER MISSIONS (JAXA'S ALOS PALSAR-2 AND ASI'S COSMO SKYMED) TO PRODUCE NEW EARTH SCIENCE DATA RECORD (ESDR) OF 1) MONTHLY ICE-SHEET WIDE ICE MOTION; 2) A NOVEL BED TOPOGRAPHY AND ICE THICKNESS OF ANTARCTICA THAT CONSERVES MASS AND FULFILLS THE REQUIREMENTS OF ICE SHEET MODELS; 3) ANNUAL MAPS OF GROUNDING LINE POSITIONS TO DOCUMENT THE DYNAMICS OF THE LAND ICE/FLOATING ICE BOUNDARIES AROUND THE CONTINENT; 4) CONTINUED TIME SERIES OF ICE-SHEET-WIDE ANNUAL MAPS OF ICE MOTION; AND 5) REVISED LAND ICE/FLOATING ICE/DRAINAGE BOUNDARIES SINCE THE 2007-2009 INTERNATIONAL POLAR YEAR USING NEWER CONSTRAINTS. THESE ESDRS WILL BE UNIQUE (BED TOPOGRAPHY AND ICE THICKNESS) OF HIGHER QUALITY (LOWER ERROR BARS) LOWER LATENCY (EVERY 4 MONTHS INSTEAD OF ANNUAL) AND WITH 12-TIME HIGHER TEMPORAL RESOLUTION THAN IN THE PAST. THE ESDRS WILL BE GENERATED USING AN AUTOMATED CHAIN OF PROCESSING EXTENSIVELY TESTED AND VETTED PRIOR PROJECTS THAT SEAMLESSLY INGESTS MULTI-SENSOR AND MULTI-BASELINE DATA AND FOR WHICH WE ELIMINATED RISKS. THE NEW BED MAP NAMED BEDMACHINE ANTARCTICA WILL BE AT AN UNPRECEDENTED LEVEL OF SPATIAL DETAILS (450 M POSTING) AND PRECISION (50-60 M) AND THE FIRST ANTARCTIC ICE SHEET WIDE PRODUCT THAT MERGES WITH BATHYMETRY PRODUCTS OFFSHORE AND CONSERVES MASS ON LAND AS NEEDED FOR ICE SHEET MODELING. WE DEMONSTRATED THAT METHODOLOGY IN GREENLAND AND HAVE THE EXPERTISE AND OBSERVATIONAL CONSTRAINTS TO APPLY IT TO ANTARCTICA. THE MONTHLY ICE MOTION MAPS WILL DOCUMENT ICE SHEET WIDE CHANGES IN GLACIER ACTIVITY ENABLING A NEW GENERATION OF ICE SHEET MODELS TO ASSIMILATE A DENSE COMPREHENSIVE SET OF CRITICAL OBSERVATIONS LIKE NEVER DONE BEFORE. THE ANNUAL MAPS OF GROUNDING LINE POSITIONS WILL INFORM MODELERS ABOUT THE MOST CRITICAL BOUNDARY BETWEEN OCEAN AND ICE. USING THE NEWEST DIGITAL ELEVATION MODELS OF THE ICE SHEET SURFACE FROM DLR S TANDEM-X IN 2017 AND THE WORLD VIEW REFERENCE ELEVATION MODEL OF ANTARCTICA (REMA) IN 2018 A HIGH-PRECISION (15 CM/YR PRECISION) MAP OF ICE MOTION USING INTERFEROMETRIC PHASE DATA FROM MULTIPLE SATELLITES AIRBORNE DATA FROM NASA S OPERATION ICEBRIDGE ELEVATION CHANGE MAPS FROM ICESAT-1/OIB/ ICESAT-2/CRYOSAT-2 AND OUTPUT PRODUCTS FROM REGIONAL ATMOSPHERIC CLIMATE MODELS WE WILL UPDATE EXITING DRAINAGE BOUNDARIES SEA LEVEL EQUIVALENCE ICE FRONT POSITIONS AND DEPTH OF SUBGLACIAL CHANNELS OCCUPIED BY ICE STREAMS ACROSS ANTARCTICA FOR THE SCIENTIFIC COMMUNITY. TOWARD THE END OF THE PROJECT WE WILL TRANSITION TO GENERATING ESDRS FROM THE NASA/INDIAN SPACE RESEARCH ORGANIZATION (ISRO) NISAR MISSION EFFECTIVELY PREPARING OURSELVES AND THE COMMUNITY FOR THIS MISSION THAT WILL PROVIDE EVEN GREATER ACCESS TO OBSERVATIONS OF THE ICE SHEETS. THESE ESDRS WILL RESPOND TO CRITICAL NEEDS FROM THE MODELING COMMUNITY AND THE BROAD SCIENTIFIC COMMUNITY INTERESTED IN UNDERSTANDING THE EVOLUTION OF ICE SHEETS AND THEIR CONTRIBUTION TO SEA LEVEL. THE ESDRS WILL IMPROVE THE CAPABILITIES OF NUMERICAL MODELS TO PROJECT THE FUTURE CONTRIBUTION OF ICE SHEETS TO SEA LEVEL RISE AND INFORM THE PUBLIC AND POLICY MAKERS. OVERALL THE PROJECT WILL SERVE NASA'S EARTH SCIENCE GOAL TO STUDY THE EVOLUTION OF THE EARTH'S ICE MASSES AND THEIR IMPACT ON SEA LEVEL CHANGE.

OpenAlex ID: W3204029564

FWCI: 3.992

Cites: 103

Cited by: 67

Related to: 10