Using Greenland Ice Sheet ablation zone radiostratigraphy to test modern data against century-averaged steady state conditions
Abstract
Surface melt and ice flow within the Greenland Ice Sheet ablation zone are quantified by modern observational data representative of recent years and decades. These data document surface melt enhancement, which may herald a departure from steady state balance between the ablation zone's geometry, velocity, and surface ablation. We test whether or not modern ablation zone observations are out of balance with century-averaged steady state conditions, which we derive from radiostratigraphy. Ice penetrating radar data collected by NASA's Operation IceBridge illustrate emergent internal layers in central west Greenland. Theory suggests that such emergent internal layers, oriented parallel to ice flow, can approximate particle paths under certain conditions. We use observationally-constrained velocity solutions from a higher order ice sheet model to simulate particle paths and internal layers, and confirm these conditions exist in selected regions of the study area. Using remotely-sensed modern surface velocities and three-dimensional ice sheet model output on ice flow, we convert internal particle path lengths ( 10 km) to particle travel times. We find that radar-detected internal layers can be used to define englacial particle displacements over century-long time scales. We use emergent internal layer geometry (i.e. particle displacement) and remotely-sensed ice velocities to solve for surface melt rates theoretically required to maintain steady state ice sheet geometry on a century-long time step. These century-averaged steady state melt rates match independent, observationally-derived surface melt rates within uncertainty bounds. This result implies that ice flow has responded to melt enhancement to maintain a state of balance.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.C12B..08F
- Keywords:
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- 0726 Ice sheets;
- CRYOSPHEREDE: 0728 Ice shelves;
- CRYOSPHEREDE: 1217 Time variable gravity;
- GEODESY AND GRAVITYDE: 4207 Arctic and Antarctic oceanography;
- OCEANOGRAPHY: GENERAL