Tidal and seasonal variations in calving flux observed with passive seismology

Journal of Geophysical Research F: Earth Surface
By: , and 

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Abstract

The seismic signatures of calving events, i.e., calving icequakes, offer an opportunity to examine calving variability with greater precision than is available with other methods. Here using observations from Yahtse Glacier, Alaska, we describe methods to detect, locate, and characterize calving icequakes. We combine these icequake records with a coincident, manually generated record of observed calving events to develop and validate a statistical model through which we can infer iceberg sizes from the properties of calving icequakes. We find that the icequake duration is the single most significant predictor of an iceberg's size. We then apply this model to 18 months of seismic recordings and find elevated iceberg calving flux during the summer and fall and a pronounced lull in calving during midwinter. Calving flux is sensitive to semidiurnal tidal stage. Large calving events are tens of percent more likely during falling and low tides than during rising and high tides, consistent with a view that deeper water has a stabilizing influence on glacier termini. Multiple factors affect the occurrence of mechanical fractures that ultimately lead to iceberg calving. At Yahtse Glacier, seismology allows us to demonstrate that variations in the rate of submarine melt are a dominant control on iceberg calving rates at seasonal timescales. On hourly to daily timescales, tidal modulation of the normal stress against the glacier terminus reveals the nonlinear glacier response to changes in the near-terminus stress field.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Tidal and seasonal variations in calving flux observed with passive seismology
Series title Journal of Geophysical Research F: Earth Surface
DOI 10.1002/2015JF003641
Volume 120
Issue 11
Year Published 2015
Language English
Publisher American Geophysical Union
Publisher location Washington
Contributing office(s) Alaska Science Center
Description 20 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Journal of Geophysical Research: Earth Surface
First page 2318
Last page 2337
Country United States
State Alaska
Other Geospatial Yahtse Glacier
Online Only (Y/N) N
Additional Online Files (Y/N) N