Michael G Shahin

and 7 more

Dynamical changes at the termini of tidewater glaciers may trigger sustained acceleration, thinning, and retreat, increasing a glacier’s contribution to sea level rise. However, processes at the ice-ocean interface occur across a range of spatial (cm to km) and temporal (minutes to years) scales, making these processes difficult to capture with many existing observational strategies. We installed two autonomous terrestrial laser scanners overlooking the terminus at Helheim Glacier, East Greenland, the first in 2015 and the second in 2018. Each laser scanner system scans every 6 hours during non-winter months and once a day during winter; together, these systems generate an extraordinary amount of data, including georeferenced point clouds, digital elevation models, velocity, and strain rates of Helheim Glacier. Our results show that large surface depressions form at a consistent location on the lee side of a subglacial ridge and have increased in occurrence over time. We also present the first inferences of Helheim Glacier’s grounding zone location; we observed over 3 km of grounding zone retreat and slightly over 1 km of grounding line migration within a tidal cycle between 2018 - 2019. Furthermore, we identify and catalog calving events that we compare with our velocity products. We find that Helheim Glacier does not undergo sustained acceleration after individual calving episodes, and variations in calving style do not impact velocity responses. Our work reveals the insensitivity of Helheim Glacier to iceberg calving during our observational record and the importance of high temporal resolution data in inferring grounding zone dynamics.

Sarah Esenther

and 9 more

Mass loss from the Greenland Ice Sheet (GrIS) is a primary contributor to sea level rise, but substantial uncertainty exists in estimates of future ice sheet losses. Surface mass balance (SMB) models, the current leading approach to sea level rise projection, anticipate continued dominance of runoff as a mass loss pathway. Despite their preeminence, SMB models in vulnerable northern environments lack adequate field validation, particularly for error-sensitive runoff estimates. We have installed a cluster of high quality field instruments at the Minturn Elv, a proglacial river site in Inglefield Land, NW Greenland to provide discharge and weather datasets for the validation and refinement of climate/SMB runoff models. The instrument cluster has meteorological, hydrological, and time lapse camera instrumentation, including a vented water level stage recorder, single shot and scanning lidars, time lapse cameras, and in situ ADCP discharge and terrestrial scanning lidar measurements. The instrument suite provides novel flow and weather datasets with the opportunity to evaluate experimental approaches to stage measurement in adverse, high-latitude areas. Inglefield is a uniquely advantaged location because proglacial runoff is dominated by SMB processes operating on the ice surface without interference from subglacial hydrology. Overall, our hydrometeorological instrument cluster at Inglefield Land will provide one of the few validation datasets for regional climate models outside of Southwest Greenland.