Permalink : http://hdl.handle.net/2115/65007

JaLCDOI : 10.14943/lowtemsci.75.15

KEYWORDS : Seismicity;infrasound;array;tidewater glacier;Greenland

Outlet glaciers in Greenland have retreated and lost mass over the past decade. Understanding the dynamics of tidewater glaciers is crucial for forecasting sea-level rise and for understanding the future of the Greenland Ice Sheet, given the buttressing support that tidewater glaciers provide to inland ice. However, the mechanisms controlling glacier-front location and the role played by external forcings (e.g., meltwater input and tidal oscillation) in basal motion and fracture formation leading to iceberg calving are poorly understood. Today it is known that glaciers generate seismic and infrasound signals that are detectable at local and teleseismic distances and can be used to monitor glacier dynamics. Here, we present examples of data recorded by a temporary network of seismic and infrasound instruments deployed at a tidewater glacier (Bowdoin Glacier, Greenland) in July 2015. Some stations were installed on ice at distances as close as ～ 250 m from the calving front, representing the closest deployments to the calving front that have been made to date. Multiple seismic and infrasound events were recorded by five seismic and six infrasound sensors, and linked to surface crevassing, calving, and ice-cliff collapses, and presumably also hydrofracturing, iceberg rotations, teleseismic earthquakes, and helicopter-induced tremors. Using classic seismological and array analysis approaches (e.g., “short-term averaging/long-term averaging” and “f-k” analysis), as well as image processing techniques, we explore this unique dataset to understand the glacial response to external forcings. Our observations, supported by GPS measurements of ice velocity, local weatherstation records, and time-lapse photography, provide a valuable resource for studying seismogenic glacial processes and their dependence on ocean tides and other environmental factors.