Dynamic Response of a High Arctic Glacier to Melt and Runoff Variations

Abstract

The dynamic response of High Arctic glaciers to increased runoff in a warming climate remains poorly understood. We analyze a 10-year record of continuous velocity data collected at multiple sites on Nordenskiöldbreen, Svalbard, and study the connection between ice flow and runoff within and between seasons. During the melt season, the sensitivity of ice motion to runoff at sites in the ablation and lower accumulation zone drops by a factor of 3 when cumulative runoff exceeds a local threshold, which is likely associated with a transition from inefficient (distributed) to efficient (channelized) drainage. Average summer (June-August) velocities are found to increase with summer ablation, while subsequent fall (September-November) velocities decrease. Spring (March-May) velocities are largely insensitive to summer ablation, which suggests a short-lived impact of summer melt on ice flow during the cold season. The net impact of summer ablation on annual velocities is found to be insignificant. Plain Language SummaryA major uncertainty in future predictions of glacier mass loss, and the corresponding sea level rise contribution, stems from a lack of understanding of potential feedbacks between surface melt and ice motion. Melt water penetrating to the bed of a glacier facilitates fast ice motion through sliding. Whether increased melt water input induces a net long-term acceleration or deceleration of ice flow however critically depends on the interaction between melt input and transience of the subglacial drainage system at both intraseasonal and interseasonal time scales. To assess this, long-term data sets of ice motion and runoff are essential. In this study, a 10-year record of continuous velocity data, collected at multiple sites on Nordenskiöldbreen in Svalbard, is presented and compared to simulated runoff. We find that the sensitivity of summer velocities to runoff drops by a factor of 3 after a runoff-induced change of drainage system morphology. While average summer motion increases with ablation, fall (September-November) motion decreases, and spring (March-May) motion appears largely insensitive to summer melt. Altogether, the net impact of increased summer melt on annual velocities is found to be negligible.

Reconciling Svalbard Glacier Mass Balance

“…A related issue is the seasonal dynamical adjustment of ice speed during the start of the ablation period, due to the decrease of basal friction. The use of continuous GPS on Svalbard glaciers (Vieli et al, 2004;Dunse et al, 2012;Vallot et al, 2017;Van Pelt et al, 2018) has confirmed the relation between water supply and ice speed-ups observed elsewhere (Iken et al, 1983;Iken and Bindschadler, 1986).…”

Quality Assessment and Glaciological Applications of Digital Elevation Models Derived from Space-Borne and Aerial Images over Two Tidewater Glaciers of Southern Spitsbergen

“…The average annual and summer (JJAS) temperatures in the period 2011-2017 were −1.6 • C and 4.3 • C respectively, whilst in 2012 annual temperature was higher (−1.1 • C) but summer temperatures were lower (3.6 • C). Higher summer temperature after 2012 would cause more intense melting and faster flow of Hansbreen, as glacier velocity is mostly controlled by the distribution and pressure of water at the glacier bed [63][64][65], which facilitate basal sliding [66][67][68].…”

A long-term dataset of climatic mass balance, snow conditions and runoff in Svalbard (1957–2018)

“…CC BY 4.0 License. -Berger et al, 2019), central Svalbard (e.g., Van Pelt et al, 2012Vega et al, 2016;Marchenko et al, 2017b;Van Pelt et al, 2018) and on an idealized Svalbard glacier (Van Pelt et al, 2016b). In this study, the model is applied for the first time to the whole of Svalbard.…”