Seismic detection and analysis of icequakes at Columbia Glacier, Alaska

Abstract

[1] Contributions to sea level rise from rapidly retreating marine-terminating glaciers are large and increasing. Strong increases in iceberg calving occur during retreat, which allows mass transfer to the ocean at a much higher rate than possible through surface melt alone. To study this process, we deployed an 11-sensor passive seismic network at Columbia Glacier, Alaska, during 2004Alaska, during -2005. We show that calving events generate narrow-band seismic signals, allowing frequency domain detections. Detection parameters were determined using direct observations of calving and validated using three statistical methods and hypocenter locations. The 1-3 Hz detections provide a good measure of the temporal distribution and size of calving events. Possible source mechanisms for the unique waveforms are discussed, and we analyze potential forcings for the observed seismicity.

A three-dimensional calving model: numerical experiments on Johnsons Glacier, Livingston Island, Antarctica

“…This is close to the value obtained for the neighbouring (but ending on land) Hurd Glacier (0.22 MPa a 1/3 ; Otero, 2008), for which ground-penetrating radar measurements and geomorphological evidence suggest a polythermal structure (Navarro and others, 2009). It is also quite similar to, though slightly higher than, the value of 0.20 MPa a 1/3 for Storglaciären, Sweden (Hanson, 1995), which is also known to be polythermal.…”

“…a −1 (reached in the northern sector because of the topography and the prevailing northeasterly wind direction) and maximum ablation rates up to −4 m w.e. a −1 measured over the past 10 years (Ximenis, 2001;Otero, 2008). The equilibrium line (approximate location shown in Fig.…”

“…Details of the procedure can be found in chapter 3 of Otero (2008). The grid used in the computations is shown in Figure 6, and consists of 5845 nodes and 3731 elements.…”

Calving Behavior at Rink Isbræ, West Greenland, from Time-Lapse Photos

“…Feedbacks between calving and ice dynamics imply a strong coupling between processes acting at the ice margins and changes upglacier (Joughin et al, 2004;Thomas, 2004;Howat et al, 2005;Joughin et al, 2008c;Nick et al, 2009;Vieli and Nick, 2011). Studies focusing on individual calving events suggest that rapid and localized perturbations may additionally determine the location, magnitude, and timing of events (O'Neel et al, 2003(O'Neel et al, , 2005(O'Neel et al, , 2007Bassis and Jacobs, 2013;Chapuis and Tetzlaff, 2014). Short-term terminus stability is therefore dependent on several parameters modifying boundary conditions at the ice cliffs, including atmospheric and oceanic factors, the presence of sea ice/ice mé-lange in the fjord, as well as glacier specific factors such as ice thickness and fjord bathymetry.…”

Resources in the Near-Surface Earth: An Introduction and Overview

“…The acquisition of active source shallow seismic data has also been effective in imaging the internal structure and bed properties of Alpine glaciers (Musil et al, 2002). Passive seismic methods have been used to detect and monitor rapid retreat of glaciers associated with sudden calving events (O'Neel et al, 2007). Qamar (1988) showed evidence for a simple relationship between the volume of an iceberg breaking off the glacier terminus and the duration of the seismic signal generated, using it to estimate the calving rate of the Columbia Glacier (Alaska) from seismological data alone.…”