Contribution of calving to frontal ablation quantified from seismic and hydroacoustic observations calibrated with lidar volume measurements

Köhler, Andreas; Pętlicki, Michał; Lefeuvre, Pierre-Marie; Buscaino, Giuseppa; Nuth, C.; Weidle, Christian

doi:10.5194/tc-13-3117-2019

Cited by 25 publications

(27 citation statements)

References 49 publications

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“…This comparison does not show any obvious relationship, but as the observation time of 6 d is rather short, we cannot exclude the influence of environmental forcings on calving activity. Consistent with our observations, Pętlicki and Kinnard (2016) and Chapuis and Tetzlaff (2014) also found that the calving activity during their observation period of a few days was not dependent on environmental forcings, while others found an influence of ocean temperature on calving activity over seasonal timescales (Luckman et al, 2015;Schild et al, 2018).…”

Section: Relation To External Forcingssupporting

confidence: 90%

Calving event size measurements and statistics of Eqip Sermia, Greenland, from terrestrial radar interferometry

Walter¹,

Lüthi²,

Vieli³

2020

The Cryosphere

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Abstract. Calving is a crucial process for the recently observed dynamic mass loss changes of the Greenland ice sheet. Despite its importance for global sea level change, major limitations in understanding the process of calving remain. This study presents high-resolution calving event data and statistics recorded with a terrestrial radar interferometer at the front of Eqip Sermia, a marine-terminating outlet glacier in Greenland. The derived digital elevation models with a spatial resolution of several metres recorded at 1 min intervals were processed to provide source areas and volumes of 906 individual calving events during a 6 d period. The calving front can be divided into sectors ending in shallow and deep water with different calving statistics and styles. For the shallow sector, characterized by an inclined and very high front, calving events are more frequent and larger than for the vertical ice cliff of the deep sector. We suggest that the calving volume deficiency of 90 % relative to the estimated ice flux in our observations of the deep sector is removed by oceanic melt, subaquatic calving, and small aerial calving events. Assuming a similar ice thickness for both sectors implies that subaqueous mass loss must be substantial for this sector with a contribution of up to 65 % to the frontal mass loss. The size distribution of the shallow sector is represented by a log-normal model, while for the deep sector the log-normal and power-law model fit well, but none of them are significantly better. Variations in calving activity and style between the sectors seem to be controlled by the bed topography and the front geometry. Within the short observation period no simple relationship between environmental forcings and calving frequency or event volume could be detected.

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Section: Relation To External Forcingssupporting

confidence: 90%

Calving event size measurements and statistics of Eqip Sermia, Greenland, from terrestrial radar interferometry

Walter¹,

Lüthi²,

Vieli³

2020

The Cryosphere

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“…For high calving activity these methods tend to miss individual events due to limited temporal resolution and their dependency on suitable weather conditions. Promising indirect methods are terrestrial photogrammetry using timelapse imagery (Minowa et al, 2018;How et al, 2019;Vallot et al, 2019), seismic monitoring (Amundson et al, 2012;Walter et al, 2013;Bartholomaus et al, 2015;Köhler et al, 2016Köhler et al, , 2019 and wave amplitudes (Minowa et al, 2018, MinowaPodolskiy et al, 2019. Nevertheless, these methods are not suitable for measuring the calving volume directly and rely on simplified assumptions.…”

Section: Introductionmentioning

confidence: 99%

Drivers of Recurring Seasonal Cycle of Glacier Calving Styles and Patterns

et al. 2021

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Calving is a crucial process for the mass loss of outlet glaciers draining the Greenland ice sheet. Moreover, due to a lack of observations, calving contributes to large uncertainties in current glacier flow models and projections. Here we investigate the frequency, volume and style of calving events by using high-resolution terrestrial radar interferometer (TRI) data from six field campaigns, continuous daily and hourly time-lapse images over 6 years and 10-s time-lapse images recorded during two field campaigns. The results demonstrate that the calving front of Eqip Sermia, a fast flowing, highly crevassed outlet glacier in West Greenland, follows a clear seasonal cycle showing a distinct pattern in areas with subglacial discharge plumes, shallow bed topography and during the presence and retreat of proglacial ice mélange. Calving event volume, frequency and style vary strongly over time depending on the state in the seasonal cycle. Strong spatial differences between three distinctive front sectors with differing bed topography, water depth and calving front slope were observed. A distinct increase in calving activity occurs in the early melt season simultaneously when ice mélange disappears and meltwater plumes become visible at the fjord surface adjacent to the ice front. While reduced retreat of the front is observed in shallow areas, accelerated retreat occurred at locations with subglacial meltwater plumes. With the emergence of these plumes at the beginning of the melt season, larger full thickness calving events occur likely due to undercutting of the calving front. Later in the melt season the calving activity at subglacial meltwater plumes is similar to the neighboring areas, suggesting the presence of plumes to become less important for calving. The results highlight the significance of subglacial discharge and bed topography on the front geometry, the temporal variability of the calving process and the variability of calving styles.

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“…A low conversion efficiency is consistent with observations reported for other physical mechanisms of underwater noise generation. For example, only ∼ 10 −8 of the energy dissipated by a breaking surface wave on the ocean is radiated as sound (Loewen and Melville, 1991). Similarly, the conversion efficiency of the impact energy of a 1-5 mm scale raindrop falling on the sea surface to underwater impact noise is in the range 10 −9 to 10 −8 (see Eq.…”

Section: Relationship Between the Block-water Impact And Acoustic Energymentioning

confidence: 99%

Quantifying iceberg calving fluxes with underwater noise

Głowacki

Deane

2020

The Cryosphere

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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.

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Contribution of calving to frontal ablation quantified from seismic and hydroacoustic observations calibrated with lidar volume measurements

Cited by 25 publications

References 49 publications

Calving event size measurements and statistics of Eqip Sermia, Greenland, from terrestrial radar interferometry

Calving event size measurements and statistics of Eqip Sermia, Greenland, from terrestrial radar interferometry

Drivers of Recurring Seasonal Cycle of Glacier Calving Styles and Patterns

Quantifying iceberg calving fluxes with underwater noise

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