Iceberg Calving and Meltwater Plumes at Helheim Glacier, Visualized in High-Resolution Satellite Imagery
Abstract
Ice-cliff failure through calving of large icebergs may cause rapid retreat of outlet glaciers and destabilization of inland ice sheets. An improved understanding of calving mechanisms at ice cliffs is of critical importance to better constrain ice-sheet models and sea-level projections. Helheim Glacier, a tidewater glacier on Greenland's eastern coast, terminates in a ~100-m-tall ice cliff with an ice-mélange choked fjord in front. Icebergs calved at Helheim are primarily non-tabular bergs which, if extending the entire terminus thickness, generate globally-detectable glacial earthquakes during calving. Some wider tabular icebergs, which remain floating upright, also calve without producing such large glacial earthquakes. An additional process occurring at Helheim's calving front involves surface meltwater pooling and the appearance of meltwater-plume-fed polynyas in the mélange. The timing and locations of polynyas, subglacial drainage, calving behavior, and glacial earthquake occurrence are all associated processes that influence Helheim's grounding state, yet limited observational data focusing on the linkages between these processes exists. Here we utilize high-resolution DigitalGlobe optical imagery to observe temporal variability in iceberg morphology and meltwater features and compare these observations with the glacial earthquake record. Meltwater features often appear in consistent positions, suggesting that fjord geometry and the resulting glacier topography have a controlling influence on their spatial persistence. Surface pooling appears more extreme when no polynya is present, so these features are likely linked. Non-tabular iceberg calving and associated glacial earthquakes can occur even when no polynya is present, yet polynya appearance suggests a channelized subglacial drainage system and hence indicates a grounded or near-grounded front. These targeted observations will inform more generalized modeling of ice-cliff retreat, as Helheim's terminus behavior may serve as an analogue to processes at the future glacial margins of Antarctica after removal of ice shelves by warming ocean waters. Unstable ice cliffs could cause retreat into the deep Antarctic basins containing vast volumes of ice with the potential to contribute several meters to global sea level.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C41C1481M
- Keywords:
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- 0758 Remote sensing;
- CRYOSPHERE;
- 0774 Dynamics;
- CRYOSPHERE;
- 0798 Modeling;
- CRYOSPHERE