Bathymetry of Northeast Greenland from Oceans Melting Greenland (OMG) High-Resolution Airborne Gravity and Magnetometer Data
Abstract
Knowledge of continental shelf and fjord bathymetry is important for understanding the future of the Greenland Ice Sheet (GrIS) and its impact on sea level rise. Recent glacial mass loss in Greenland has been attributed to warming ocean waters, whose circulation and access to the grounding line is governed by the bathymetry of the continental shelf surrounding the island. Bathymetry is unknown in much of the coastal areas of Greenland due to ice covered waters that make ship-based mapping a challenge. Northeast Greenland (NEG), in particular, has few ship-based multibeam eco sounding (MBES) data lines available. In 2016, National Aeronautics and Space Administration's (NASA) Oceans Melting Greenland (OMG) mission collected a dataset of high-resolution airborne gravity and magnetic data in NEG. Here we estimate the bathymetry of NEG from gravity and magnetic data where Nioghalvfjerdsfjorden (79North) and Zachariae Isstrøm drain into the sea. NEG is a complex geologic region with known density variations and scarce MBES constraints. Due to this, a regional gravity trend was removed from the observed free air gravity anomaly and the airborne magnetic data was used to interpret the local geology before the gravity inversion was applied. The resulting bathymetry presents a shallower basin in the Southwest area of the surveyed region in front of the Zachariae Isstrøm grounding line than previous models, in addition to numerous interconnected seawater cavities. A north-south trending bathymetric ridge divides the region into nearshore and outboard sectors. At its southern end this ridge is subaerially exposed early Proterozoic gneissic rock islands. At its northern end combined gravity and magnetic analyses suggest the ridge continues as sediment, likely deposited by the glaciers during retreat from the Last Glacial Maximum (LGM) and influenced by the presence of the hard rock ridge to the south. This multistep inversion approach reveals the importance of collecting gravity and magnetic data in regions where ship-based constraints are hard to achieve and establishes a procedure for obtaining a geologically informed model of the underlying bathymetry.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C53B1347L
- Keywords:
-
- 0473 Paleoclimatology and paleoceanography;
- BIOGEOSCIENCES;
- 0776 Glaciology;
- CRYOSPHERE;
- 0793 Biogeochemistry;
- CRYOSPHERE