Short-term variations in calving of a tidewater glacier: LeConte Glacier, Alaska, U.S.A.

Abstract

ABSTRACT. Knowledge of iceberg calving is important for understanding instabilities of tidewater glaciers and ice sheets. Since 1995 the terminus of LeConte Glacier, Alaska, U.S.A., has retreated about 2 km and the glacier has thinned approximately 120 m at its 1999 terminus position. Our focus is short-term (hours to weeks) variability of the frequency and magnitude of calving events and calving flux. Both photogrammetric and visual observations are employed in a temporal analysis over a several-week period. We combined these data with measurements of ice speed, tide level, surface water input and water-storage estimates in an attempt to better understand the calving process. Contrary to results obtained over longer time-scales on other glaciers, our results show no correlation between ice speed and the frequency of calving. However, calving events do not appear to occur randomly; often they are a response to measurable changes in other parameters within the terminus region. Caclving can often be attributed to buoyancy perturbations and possibly flexure of the nearly floating terminus. Given the multiple possibilities for buoyancy perturbations, we have found no simple relationship between any specific forcing parameter and calving at short time-scales.

The future is Nye: an extension of the perfect plastic approximation to tidewater glaciers

“…The idealized geometries, inspired by Oerlemans (2008), are chosen to be relevant to outlet glaciers. We test the model using a realistic range of yield strengths, 50-300 kPa, to examine the effect of τ y in idealized cases.…”

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.…”

Stikine Icefield Mass Loss between 2000 and 2013/2014

“…Previous studies investigating mass loss (e.g., Larsen et al, 2007;Berthier et al, 2010;Arendt et al, 2013;Larsen et al, 2015) and glacier dynamics (e.g., O'Neel et al, 2001O'Neel et al, , 2003 at Alaskan glaciers cover the Stikine Icefield, which is a small fraction of these generally regional studies. These studies lack the resolution to discern individual glaciers (e.g., Arendt et al, 2013), have incomplete coverage (e.g., Larsen et al, 2015), or do not incorporate the most recent data (e.g., Larsen et al, 2007;Berthier et al, 2010).…”

“…The approximate shape of the cross-sections at the glacier fronts for North and South Sawyer glaciers are determined by comparing ice elevations along the front transects in 2000 from the SRTM DEM to ice elevations in 2013 from the WorldView DEMs ( Figure S5). The cross-section at the front transect of LeConte Glacier is assumed to be triangular based on the cross-section shown in Figure 2A of O'Neel et al (2003), and the cross-section of Dawes Glacier is assumed to be trapezoidal based on the bathymetry data available from the USGS.…”