Underwater acoustic signatures of glacier calving

Głowacki, Oskar; Deane, Grant B.; Moskalik, Mateusz; Blondel, Philippe; Tęgowski, Jarosław; Błaszczyk, Małgorzata

doi:10.1002/2014gl062859

Cited by 44 publications

(55 citation statements)

References 43 publications

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“…In particular, the oceanographic conditions at Helheim do not support the type of thermal erosion that is known to lead to the footloose mechanism. In general, frequent gravity-driven small-magnitude freeboard calving is often observed in glaciers, compared to less frequent but larger-scale submarine calving [Warren et al, 1995;Glowacki et al, 2015]. Furthermore, water column observations of Helheim Fjord have shown a persistent warm layer of Atlantic water at depth [Straneo et al, 2011], which supports the idea of enhanced undercutting.…”

Section: Figures 3 and 4 Show Comparisons Between Previously Reportedmentioning

confidence: 73%

On the role of buoyant flexure in glacier calving

Wagner

James

Murray

et al. 2016

Geophysical Research Letters

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Interactions between glaciers and the ocean are key for understanding the dynamics of the cryosphere in the climate system. Here we investigate the role of hydrostatic forces in glacier calving. We develop a mathematical model to account for the elastic deformation of glaciers in response to three effects: (i) marine and lake‐terminating glaciers tend to enter water with a nonzero slope, resulting in upward flexure around the grounding line; (ii) horizontal pressure imbalances at the terminus are known to cause hydrostatic in‐plane stresses and downward acting torque; (iii) submerged ice protrusions at the glacier front may induce additional buoyancy forces that can cause calving. Our model provides theoretical estimates of the importance of each effect and suggests geometric and material conditions under which a given glacier will calve from hydrostatic flexure. We find good agreement with observations. This work sheds light on the intricate processes involved in glacier calving and can be hoped to improve our ability to model and predict future changes in the ice‐climate system.

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Section: Figures 3 and 4 Show Comparisons Between Previously Reportedmentioning

confidence: 73%

On the role of buoyant flexure in glacier calving

Wagner

James

Murray

et al. 2016

Geophysical Research Letters

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“…The SPL within Icy Bay varies over a 40 dB (referenced 1 μPa) range, yet the spectral characteristics are similar regardless of the SPL, implying that a single process—melting of glacier ice—is acting at variable rates. Other processes, such as calving [ Pettit , ; Glowacki et al ., ] and subglacial discharge modify the spectral characteristics over hourly to daily timescales. These characteristics of the ambient noise strengthen the possibility of using acoustic data to estimate ice melt rates within fjords or in subice shelf cavities, in addition to measuring variability of calving and other transient activity.…”

Section: Discussionmentioning

confidence: 96%

Unusually loud ambient noise in tidewater glacier fjords: A signal of ice melt

Pettit

Lee

Brann

et al. 2015

Geophysical Research Letters

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In glacierized fjords, the ice-ocean boundary is a physically and biologically dynamic environment that is sensitive to both glacier flow and ocean circulation. Ocean ambient noise offers insight into processes and change at the ice-ocean boundary. Here we characterize fjord ambient noise and show that the average noise levels are louder than nearly all measured natural oceanic environments (significantly louder than sea ice and nonglacierized fjords). Icy Bay, Alaska, has an annual average sound pressure level of 120 dB (referenced to 1 μPa) with a broad peak between 1000 and 3000 Hz. Bubble formation in the water column as glacier ice melts is the noise source, with variability driven by fjord circulation patterns. Measurements from two additional fjords, in Alaska and Antarctica, support that this unusually loud ambient noise in Icy Bay is representative of glacierized fjords. These high noise levels likely alter the behavior of marine mammals.

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“…Thus, we are unable to include valuable information regarding calving style (Table ) in our calculations of longer‐term calving flux (Table and Figure ). Further analyses may reveal other icequake properties that can be used to predict calving style, or hydroacoustic methods may meet this need [ Glowacki et al , ]. Given the importance of calving style for icequake seismogenesis, we suggest that further research in this area be accompanied by investigations into the differences in and controls on calving style at tidewater glaciers.…”

Section: Discussionmentioning

confidence: 99%

Tidal and seasonal variations in calving flux observed with passive seismology

et al. 2015

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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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Underwater acoustic signatures of glacier calving

Cited by 44 publications

References 43 publications

On the role of buoyant flexure in glacier calving

On the role of buoyant flexure in glacier calving

Unusually loud ambient noise in tidewater glacier fjords: A signal of ice melt

Tidal and seasonal variations in calving flux observed with passive seismology

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