Abstract
Abstract. Accurate estimates of calving fluxes are essential in understanding small-scale glacier dynamics and quantifying the contribution of marine-terminating glaciers to both eustatic sea-level rise (SLR) and the freshwater budget of polar regions. Here we investigate the application of acoustical oceanography to measure calving flux using the underwater sounds of iceberg–water impact. A combination of time-lapse photography and passive acoustics is used to determine the relationship between the mass and impact noise of 169 icebergs generated by subaerial calving events from Hansbreen, Svalbard. The analysis includes three major factors affecting the observed noise: (1) time dependency of the thermohaline structure, (2) variability in the ocean depth along the waveguide and (3) reflection of impact noise from the glacier terminus. A correlation of 0.76 is found between the (log-transformed) kinetic energy of the falling iceberg and the corresponding measured acoustic energy corrected for these three factors. An error-in-variables linear regression is applied to estimate the coefficients of this relationship. Energy conversion coefficients for non-transformed variables are 8×10-7 and 0.92, respectively, for the multiplication factor and exponent of the power law. This simple model can be used to measure solid ice discharge from Hansbreen. Uncertainty in the estimate is a function of the number of calving events observed; 50 % uncertainty is expected for eight blocks dropping to 20 % and 10 %, respectively, for 40 and 135 calving events. It may be possible to lower these errors if the influence of different calving styles on the received noise spectra can be determined.
Highlights
1.1 The role of iceberg calving in glacier retreat and sea-level riseThe contribution of glaciers and ice sheets to the eustatic sea-level rise (SLR) between 2003 and 2008 has been estimated to be 1.51 ± 0.16 mm of sea-level equivalent per year (Gardner et al, 2013)
The model formation begins with a discussion of the statistics of iceberg volume and drop height estimated from the time-lapse images, leading to estimates of the block impact kinetic energy (Sect. 4.1). This is followed by an analysis of the acoustic emission from ice block impacts in terms of its amplitude–frequency characteristics, resulting in an estimate of the total underwater noise energy generated by a calving event (Sect. 4.2)
Based on this relationship, a new methodology is suggested for quantifying the calving flux from the underwater noise of iceberg–water impact (Sect. 4.5)
Summary
1.1 The role of iceberg calving in glacier retreat and sea-level riseThe contribution of glaciers and ice sheets to the eustatic sea-level rise (SLR) between 2003 and 2008 has been estimated to be 1.51 ± 0.16 mm of sea-level equivalent per year (Gardner et al, 2013). Several studies found that increased submarine melting is a major factor responsible for the observed rapid retreat of tidewater glaciers (e.g., Straneo and Heimbach, 2013; Luckman et al, 2015; Holmes et al, 2019). Terminus undercutting results from submarine melting and is often considered to be a major trigger of ice breakup at the glacier front (Bartholomaus et al, 2013; O’Leary and Christoffersen, 2013). In support of this idea, the solid ice discharge from tidewater glaciers was found to be highly correlated with ocean temperatures
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
