Abstract
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 Kings Bay 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 4–9 m d−1). This study shows the feasibility to seismically monitor not only frontal ablation rates but also the dynamic ice loss contribution continuously and at high temporal resolution.
Highlights
Glaciers are an important contributor to eustatic sea level rise in a warming climate (Gardner et al, 2013; Huss and Hock, 2015), with dynamic discharge being one of the largest uncertainties in future predictions (Vaughan et al, 2013)
A different approach was applied by Köhler et al (2016), who calibrated an empirical model of dynamic ice loss using frontal glacier ablation measured through time series of repeat satellite images, allowing reconstruction of frontal ablation directly from seismic calving signals with weekly resolution and going back decades
We successfully developed empirical models relating calving signals to volumes at Kronebreen, a fast-flowing tidewater glacier in northwest Svalbard, based on calving volumes from 10 d of repeat lidar scanning in August and September 2016
Summary
Glaciers are an important contributor to eustatic sea level rise in a warming climate (Gardner et al, 2013; Huss and Hock, 2015), with dynamic discharge being one of the largest uncertainties in future predictions (Vaughan et al, 2013). A different approach was applied by Köhler et al (2016), who calibrated an empirical model of dynamic ice loss using frontal glacier ablation measured through time series of repeat satellite images, allowing reconstruction of frontal ablation directly from seismic calving signals with weekly resolution and going back decades. In this approach, a constant ratio between frontal melting and calving was implicitly included, an assumption that requires validation through independent dynamic ice loss measurements. We compare our results with independently measured frontal ablation rates at Kronebreen to assess the potential to quantify the contribution of frontal melting
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