Year: 2025
Type: article
Abstract: Surface crevassing on the Greenland Ice Sheet is a large source of uncertainty in processes controlling mass loss due to a lack of comprehensive observations of their location and evolution through time. Here we use high-resolution digital elevation models to map the three-dimensional volume of crevasse fields across the Greenland Ice Sheet in 2016 and 2021. We show that, between the two years, large and significant increases in crevasse volume occurred at marine-terminating sectors with accelerating flow (up to +25.3 ± 10.1% in the southeast sector), while the change in total ice-sheet-wide crevasse volume was within measurement error (+4.3 ± 5.9%). The sectoral increases were offset by a reduction in crevasse volume in the central west sector (-14.2 ± 3.2%), particularly at Sermeq Kujalleq (Jakobshavn Isbræ), which exhibited slowdown and thickening over the study period. Changes in crevasse volume correlate strongly with antecedent discharge changes, indicating that the acceleration of ice flow in Greenland forces significant increases in crevassing on a timescale of less than five years. This response provides a mechanism for mass-loss-promoting feedbacks on sub-decadal timescales, including increased calving, faster flow and accelerated water transfer to the bed.
Source: Nature Geoscience
Language: English
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
SDG: Climate action
Open Access status: hybrid
Estimated APC paid: $12,690
Awards: WE PROPOSE TO EXTEND AND SUBSTANTIALLY IMPROVE THE COMPREHENSIVE RECORD OF THICKNESS VELOCITY AND ICE DISCHARGE FOR GREENLAND S MARINE-TERMINATING OUTLET GLACIERS IN ORDER TO CONSTRAIN ICE SHEET AND OCEAN MODELS AND BETTER UNDERSTAND CHANGES IN ICE DYNAMICS FRESHWATER FLUX MASS BALANCE AND CONTRIBUTION TO SEA LEVEL RISE. PREDICTIONS OF THE FUTURE BEHAVIOR OF GREENLAND S FAST-FLOWING OUTLET GLACIERS REMAIN HIGHLY UNCERTAIN DUE TO THEIR COMPLEX AND VARIABLE DYNAMICS. EXISTING ICE-SHEET WIDE RECORDS OF GLACIER VELOCITY DISCHARGE AND FRESHWATER FLUX COVER TOO SHORT A PERIOD AND ARE TOO COARSE IN TEMPORAL RESOLUTION TO PROVIDE ADEQUATE CONSTRAINTS FOR NUMERICAL ICE SHEET MODELS AND EFFORTS TO QUANTIFY FRESHWATER FORCING ON OCEAN CIRCULATION. RECENT EXPANSIONS IN OBSERVATIONAL CAPACITY FROM AIR AND SPACE NEW DATA ACCESS IMPROVED DATA PROCESSING METHODS AND ENHANCED SURFACE MASS BALANCE MODELING NOW ENABLE BACKWARD EXPANSION OF THESE RECORDS TO MID 1980 S WITH SEASONAL TO DAILY TEMPORAL RESOLUTION. WE WILL MERGE OBSERVATIONS FROM A WIDE RANGE OF EARTH OBSERVING SENSORS UTILIZING NASA PRODUCTS FROM THE MEASURES GREENLAND ICE MAPPING PROJECT AND OPERATION ICEBRIDGE AS WELL AS SUB-METER RESOLUTION IMAGERY FROM DIGITALGLOBE. THE LATTER OFFERS THE TRANSFORMATIVE POTENTIAL TO BRIDGE THE MEASUREMENT GAP BETWEEN GROUND OBSERVATIONS AND REMOTE SENSING BY ENABLING ~DAILY RESOLUTION ICE VELOCITY OBSERVATIONS OVER LARGE AREAS. WE WILL ALSO UTILIZE HIGH RESOLUTION REANALYSIS MODEL ESTIMATES OF SURFACE MASS BALANCE AND MELT RUNOFF TO DETERMINE GLACIER/ FJORD SCALE FRESHWATER FLUXES. WE WILL USE OUR IMPROVED RECORD TO ASSESS VARIABILITY IN ICE DYNAMICS DISCHARGE AND FRESHWATER FLUX AT A RANGE OF TIMESCALES FROM SHORT-TERM CHANGES DUE TO ICEBERG CALVING AND SEA ICE CONDITIONS TO MULTI-DECADAL SHIFTS DUE TO LONG-TERM CLIMATE AND OCEAN TRENDS. OUR PROJECT INCLUDES COLLABORATORS WHO WILL USE THESE OBSERVATIONS TO CONSTRAIN NUMERICAL ICE SHEET MODELS AND QUANTIFY FRESHWATER FORCING ON OCEAN CIRCULATION OFFERING IMMEDIATE AND WIDE-RANGING SCIENCE RETURN. OUR PROPOSAL RESPONDS TO SEVERAL OF THE OBJECTIVES OF THE NRA INCLUDING TO DETERMINE THE MECHANISMS CONTROLLING MASS BALANCE AND DYNAMICS OF THE GREENLAND ADVANCE UNDERSTANDING OF LAND-ICE PROCESSES ESPECIALLY CONNECTIONS AMONG THE WARMING OCEAN AND INCREASES IN GLACIAL FLOW RATES CHARACTERIZE LAND ICE PROPERTIES... AND PHYSICAL PROCESSES SUCH THAT THEY CAN BE INCORPORATED INTO MODELS AND USE REMOTE SENSING DATA TO VALIDATE AND IMPROVE MODELS OF LAND-BASED ICE AND THEIR CONTRIBUTIONS TO SEA-LEVEL CHANGE . OUR OBSERVATIONS WILL CROSS-VALIDATE AND IMPROVE MEASUREMENTS OBTAINED FROM THE NASA GRACE AND UPCOMING ICESAT-2 MISSIONS., The Polar Geospatial Center: Community and Facility Support, G3181354122, G3507382215, G4448173235, GEO OSE Track 1: Enhancing the accessibility of novel geostatistical inversion workflows for cryosphere research, G5113138680, NUMEROUS STUDIES HAVE REVEALED RAPID CHANGES IN ICE DISCHARGE FROM GREENLAND WITH MANY OF THE ICE SHEET S OUTLET GLACIERS HAVING ACCELERATED DRAMATICALLY OVER THE LAST TWO DECADES. THESE OBSERVATIONS ARE SIGNIFICANT IN THAT THEY SHOW GREENLAND S MASS BALANCE CAN FLUCTUATE RAPIDLY AND UNPREDICTABLY. DESPITE THE LARGE MAGNITUDES OF THESE CHANGES WE DO NOT YET UNDERSTAND THE UNDERLYING PROCESSES CONTROLLING FAST FLOW WELL ENOUGH TO DETERMINE THEIR LONG-TERM IMPACT ON SEA LEVEL. OBSERVATIONS MADE OVER THE LAST SEVERAL YEARS INCLUDING THOSE FROM OUR PRIOR PROJECTS INDICATE LESS POTENTIAL FOR RUN-AWAY ICE LOSS THAN WAS INITIALLY FEARED WHEN THE FIRST OBSERVATIONS OF RAPID CHANGE WERE MADE. NONETHELESS OUTLET GLACIER DYNAMICS REMAIN A WILD CARD IN THE SEA-LEVEL PROJECTIONS AS NOTED IN THE LAST TWO INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE (IPCC) ASSESSMENTS. IMPROVING SUCH PREDICTIONS AND GAINING A FIRM UNDERSTANDING OF THE DYNAMICS THAT DRIVE MASS BALANCE REQUIRES ANNUAL TO SUB-ANNUAL OBSERVATIONS OF OUTLET GLACIER VARIABILITY (VELOCITY ELEVATION AND ICE FRONT POSITION) TO AVOID ALIASING OF THE RAPIDLY VARYING SIGNALS. FURTHERMORE ALTHOUGH GLACIERS CAN CHANGE FAR MORE RAPIDLY (SUB-ANNUAL SCALES) THAN EXPECTED DECADAL-SCALE OBSERVATIONS ARE STILL REQUIRED TO PROVIDE THE KNOWLEDGE NEEDED FOR CENTURY-SCALE PROJECTION. THE TECHNOLOGY FOR MEASURING VELOCITY IN GREENLAND IS MATURE AS DEMONSTRATED THROUGH OUR ONGOING AND PAST GREENLAND ICE MAPPING PROJECTS (GIMP-1&2). THROUGH THESE PROJECTS WE HAVE REPEATEDLY MEASURED ICE VELOCITY IN GREENLAND ESTABLISHING A RECORD FROM 2000 TO PRESENT. THROUGH GIMP-3 WE WILL CONTINUE THIS EFFORT TO EXTEND THE RECORD OF ICE FLOW VELOCITY THROUGH 2022 A PERIOD WHEN GREENLAND LIKELY WILL CONTINUE TO EVOLVE RAPIDLY WITH THE CURRENT WARMING. THE GIMP-3 PRODUCTS WILL BE ENTIRELY COMPATIBLE WITH PRIOR PRODUCTS BUT WE WILL TAKE ADVANTAGE OF NEW SENSORS THAT HAVE BEEN LAUNCHED IN THE LAST 5 YEARS (LANDSAT 8 SENTINEL 1A/B AND SENTINEL 2A/B) TO GREATLY IMPROVE TEMPORAL AND SPATIAL SAMPLING. IN ADDITION WE WILL TAKE ADVANTAGE OF THE IMPROVED AVAILABILITY OF LANDSAT TM DATA TO EXTEND THE RECORD BACK IN TIME TO 1984. IN CONJUNCTION WITH THE RESULTS FROM OUR EARLIER PROJECTS GIMP-3 WILL PROVIDE AN IMPORTANT NEARLY FOUR-DECADE-LONG PRECURSOR DATA SET FOR THE NISAR L-BAND SAR MISSION SCHEDULED TO LAUNCH NEAR THE END OF THE DECADE AS A JOINT EFFORT BETWEEN NASA AND THE INDIAN SPACE AGENCY. IN ADDITION GIMP-3 VELOCITY MEASUREMENTS WILL PROVIDE A STRONG COMPLEMENT TO THE THINNING MEASUREMENTS MADE BY NASA S ICESAT-2 AND ICEBRIDGE MISSIONS., Automated, High Resolution Terrain Generation for XSEDE, G647621482, G8264246533, The Polar Geospatial Information Center: Joint Support
OpenAlex ID: W4407108216