Inferring subglacial hydrology from investigations of supraglacial lake drainages and meltwater plumes at Store Glacier, West Greenland

• Main Author: Hagen, Isabel
• Format: Thesis
• Language: English
• Published: Apollo - University of Cambridge Repository 2020
• Subjects: Greenland; glaciers; subglacial; glacier; Ice Sheet; Tidewater
• Online Access: https://dx.doi.org/10.17863/cam.58899; https://www.repository.cam.ac.uk/handle/1810/311809

The Greenland ice sheet has experienced a six-fold increase in ice loss during the last three decades, contributing significantly to global sea level rise. About 60% of the Greenland ice loss comes from dynamic ice loss from tidewater glaciers. Tidewater glaciers each have unique subglacial drainage systems and discharge meltwater into adjacent fjords differently. However, studies of the subglacial hydrology of individual tidewater glaciers have been limited, largely due to the difficulty in obtaining direct measurements. The input of water to the subglacial drainage systems come from drainage of supraglacial lakes, crevasses and moulins. The water travel downstream through subglacial channels, eventually reaching the terminus of the glacier, where the freshwater discharge form buoyant plumes that rise through the ambient ocean water, and eventually reach the surface. In this study, supraglacial lake volume and drainage were analysed with the dual-satellite FASTER algorithm, and meltwater plume areas were assessed through time-lapse photogrammetry in the Python toolbox PyTrx, in order to reconstruct the subglacial hydrology of the tidewater glacier Store Glacier in West Greenland during the 2018 summer melting season. The results of this study indicate a distributed and inefficient drainage system in June, with drainage leading to increased subglacial storage in cavities and disconnected channels. By early July, the drainage system on the glacier below 1000 m elevation had developed into an efficient system, experiencing fast hydraulic transmissivity, while elevations above 1000 m still experienced slow hydraulic transmissivity in a distributed drainage system. This research provides high-detail observations of the unique subglacial drainage system of a tidewater glacier. Understanding the subglacial hydrology of tidewater glaciers is key for making ice loss predictions about the next century.