Abstract
Icebergs and ice islands (large, tabular icebergs) are challenging targets to survey due to their size, mobility, remote locations, and potentially difficult environmental conditions. Here, we assess the precision and utility of aerial photography surveying with structure-from-motion multi-view stereo photogrammetry processing (SfM) and vessel-based terrestrial laser scanning (TLS) for iceberg deterioration detection and mass estimation. For both techniques, we determine the minimum amount of change required to reliably resolve iceberg deterioration, the deterioration detection threshold (DDT), using triplicate surveys of two iceberg survey targets. We also calculate their relative uncertainties for iceberg mass estimation. The quality of deployed Global Positioning System (GPS) units that were used for drift correction and scale assignment was a major determinant of point cloud precision. When dual-frequency GPS receivers were deployed, DDT values of 2.5 and 0.40 m were calculated for the TLS and SfM point clouds, respectively. In contrast, values of 6.6 and 3.4 m were calculated when tracking beacons with lower-quality GPS were used. The SfM dataset was also more precise when used for iceberg mass estimation, and we recommend further development of this technique for iceberg-related end-uses.
Highlights
Recent calving events from ice shelves and floating glacier tongues have created immense tabular icebergs in both the Arctic (e.g., Petermann Glacier: ~300 km2) [1] and Antarctic (e.g., Larsen-C Ice Shelf: ~5800 km2) [2]
This research provides the first quantification of the deterioration detection threshold (DDT) for drifting icebergs or ice islands with observations made through SfM processing of repeat aerial-photo surveys or terrestrial laser scanning (TLS) surveys
It details a method of iceberg drift correction using Global Positioning System (GPS) data as well as protocols for point cloud generation and comparison
Summary
Recent calving events from ice shelves and floating glacier tongues have created immense tabular icebergs in both the Arctic (e.g., Petermann Glacier: ~300 km2) [1] and Antarctic (e.g., Larsen-C Ice Shelf: ~5800 km2) [2]. The calibration and validation of both iceberg and ice island deterioration models has been restrained by a paucity of in-situ data sets that accurately capture both the morphological change and corresponding environmental data required [14,15]. This is largely due to logistical, financial, and safety issues that accompany surveying these subjects in remote locations [16,17]. While there is interest in collecting deterioration data, it is first necessary to determine the capabilities of available surveying techniques to ensure that meaningful deterioration magnitudes or mass estimates are reported
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