Calving controlled by melt-under-cutting: detailed calving styles revealed through time-lapse observations

How, Penelope; Schild, K. M.; Benn, Douglas I.; Noormets, Riko; Kirchner, Nina; Luckman, Adrian; Vallot, Dorothée; Hulton, Nick; Borstad, Chris

doi:10.1017/aog.2018.28

Cited by 66 publications

(121 citation statements)

References 51 publications

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“…Although immediate calving responses to the 2015 lake drainage were confined to discrete ice-falls along the thermo-erosional notch, the subsequent topple events under ice-free lake conditions are indicative of increased stress gradients at the calving front promoting the outward toppling of unstable flakes and pillars of ice in response to debuttressing. Similarly, How et al (2019) observed that calving termini are highly sensitive to variations in backstress, with even relatively small reductions, such as those associated with the falling limb of an ocean tide, observed to increase calving frequency. The recurrence of waterline events within 24 hr of both the 2014 and 2015 lake drainages implies rapid reestablishment of melt-undercutting as the dominant driver of calving at Russell Glacier IDL.…”

Section: Effects Of Sudden Lake Drainage On Calving Dynamicsmentioning

confidence: 88%

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Calving Seasonality Associated With Melt‐Undercutting and Lake Ice Cover

Mallalieu

Carrivick

Quincey

et al. 2020

Geophysical Research Letters

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A detailed understanding of calving processes at the lacustrine margins of the Greenland ice sheet is necessary for accurately forecasting its dynamic response to ongoing climate change. However, existing data sets of lacustrine calving are limited to summer seasons and to alpine glaciers. Here, we use an integrated time-lapse and structure-from-motion approach to generate the first continuous year-round volumetric record of calving processes at a lacustrine ice sheet margin. We identify two distinct calving regimes that are associated with melt-undercutting and lake ice cover. We also find that calving rates respond rapidly to sudden lake drainage. Given that lake temperature, lake ice cover, and sudden lake drainages are controlled by air temperature and ice-margin thinning, we suggest that climate change, manifested in lengthening summer seasons, will accelerate rates of mass loss and terminus recession at lacustrine ice-margins in Greenland.Plain Language Summary Lakes situated at the margins of glaciers and ice sheets are important because they promote the detachment of large blocks of ice to form icebergs, a process known as calving. Climate change is increasing the number of lakes at the margins of the Greenland ice sheet, and many of those already present are increasing in size. Consequently, a detailed understanding of lake calving processes is needed to accurately predict the future response of the ice sheet to climate change. This study improves our knowledge of calving processes by using time-lapse cameras to record images of calving activity at a lake located in western Greenland over a continuous 14-month period. We use the images to create 3D models that illustrate how calving processes change through time and find that rates and styles of calving vary seasonally in response to lake-driven undercutting of the ice sheet margin and the presence or absence of lake ice cover. Our results suggest that ice loss via calving activity at the lake edges of the Greenland ice sheet will increase in future as summer seasons lengthen in response to climate change.

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Section: Effects Of Sudden Lake Drainage On Calving Dynamicsmentioning

confidence: 88%

“…termini (e.g., Chapuis & Tetzlaff, 2014;How et al, 2019;Medrzycka et al, 2016), whereby relatively low-magnitude falls are the most prevalent calving mechanism, but mass loss is dominated by a small number of high-magnitude events.…”

Section: Calving Processesmentioning

confidence: 99%

Calving Seasonality Associated With Melt‐Undercutting and Lake Ice Cover

Mallalieu

Carrivick

Quincey

et al. 2020

Geophysical Research Letters

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“…Certainly, the presence of sills is known to modify fjord water properties substantially by blocking access of dense waters to the calving front (Gladish et al, 2015), but this extrapolation remains a simplification due to vertical mixing within fjords (e.g. Inall et al, 2014) and because periodic dense inflows over sills have been observed in Greenland (Mortensen et al, 2011). Therefore, both the retreat and submarine melt implementations would be improved with methods to quantify water mass transformation between the shelf and calving fronts.…”

Section: Missing Processes and Priorities For Future Improvementmentioning

confidence: 99%

Twenty-first century ocean forcing of the Greenland ice sheet for modelling of sea level contribution

et al. 2020

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Abstract. Changes in ocean temperature and salinity are expected to be an important determinant of the Greenland ice sheet's future sea level contribution. Yet, simulating the impact of these changes in continental-scale ice sheet models remains challenging due to the small scale of key physics, such as fjord circulation and plume dynamics, and poor understanding of critical processes, such as calving and submarine melting. Here we present the ocean forcing strategy for Greenland ice sheet models taking part in the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6), the primary community effort to provide 21st century sea level projections for the Intergovernmental Panel on Climate Change Sixth Assessment Report. Beginning from global atmosphere–ocean general circulation models, we describe two complementary approaches to provide ocean boundary conditions for Greenland ice sheet models, termed the “retreat” and “submarine melt” implementations. The retreat implementation parameterises glacier retreat as a function of projected subglacial discharge and ocean thermal forcing, is designed to be implementable by all ice sheet models and results in retreat of around 1 and 15 km by 2100 in RCP2.6 and 8.5 scenarios, respectively. The submarine melt implementation provides estimated submarine melting only, leaving the ice sheet model to solve for the resulting calving and glacier retreat and suggests submarine melt rates will change little under RCP2.6 but will approximately triple by 2100 under RCP8.5. Both implementations have necessarily made use of simplifying assumptions and poorly constrained parameterisations and, as such, further research on submarine melting, calving and fjord–shelf exchange should remain a priority. Nevertheless, the presented framework will allow an ensemble of Greenland ice sheet models to be systematically and consistently forced by the ocean for the first time and should result in a significant improvement in projections of the Greenland ice sheet's contribution to future sea level change.

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“…For the time period of our experiment between 24 August and 2 September, the approach of Köhler et al (2016) yields an ice loss of about 18•10 6 m 3 . Since about two-thirds of the grounded vertical terminus area of Kronebreen are submarine (Lindbäck et al, 2018) and assuming that submarine ice loss occurs mainly through melting as suggested by our visual calving observations at Kronebreen and How et al (2019), the corresponding dynamic ice loss would be 6•10 6 m 3 which is just slightly above the values estimated from the KRBN and KRBS records in this study, i.e., the contribution of calving to frontal ablation would be 18-30% (Table 1). For the entire year of 2016, the approach of Köhler et al (2016) yields an ice loss of about 640±80•10 6 m 3 .…”

mentioning

confidence: 75%

“…CC BY 4.0 License. observations at other glaciers in Svalbard (How et al, 2019). In addition, an autonomous calving event detector is implemented to compare the time series of seismicity and directly observed calving (see Fig.…”

mentioning

confidence: 99%

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

Köhler¹,

Pętlicki²,

Lefeuvre³

et al. 2019

Preprint

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Abstract. Frontal ablation contributes significantly to the mass balance of tidewater glaciers in Svalbard and can be recovered with high temporal resolution using continuous seismic records. Determination of the relative contribution of dynamic ice loss through calving to frontal ablation requires precise estimates of calving volumes at the same temporal resolution. We combine seismic and hydroacoustic observations close to the calving front of Kronebreen, a marine terminating glacier in Svalbard, with repeat lidar scanning of the glacier front. Simultaneous time-lapse photography is used to assign volumes measured from lidar scans to seismically detected calving events. Empirical models derived from signal properties such as integrated amplitude are able to replicate volumes of individual calving events and cumulative subaerial ice loss over different lidar scan intervals from seismic and hydroacoustic data alone. This enables quantification of the contribution of calving to frontal ablation, which we estimate for Kronebreen to be about 18–30 %, slightly below the subaerially exposed area of the glacier front. We further develop a model calibrated for the permanent seismic station KBS at about 15 km distance from the glacier front, where 15–60 % of calving events can be detected under variable noise conditions due to reduced signal amplitudes at distance. Between 2007 and 2017, we find a 5–30 % contribution of calving ice blocks to frontal ablation which emphasizes the importance of underwater melting (roughly 150–350 m a−1). This study shows the feasibility to seismically monitor not only frontal ablation rates but also its dynamic ice loss contribution continuously and at high temporal resolution.

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Calving controlled by melt-under-cutting: detailed calving styles revealed through time-lapse observations

Cited by 66 publications

References 51 publications

Calving Seasonality Associated With Melt‐Undercutting and Lake Ice Cover

Calving Seasonality Associated With Melt‐Undercutting and Lake Ice Cover

Twenty-first century ocean forcing of the Greenland ice sheet for modelling of sea level contribution

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

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