Calving of a tidewater glacier driven by melting at the waterline

Abstract

ABSTRACT. We present a study of the development of a thermo-erosional notch at the waterline and its influence on calving of Hansbreen, a medium-sized grounded tidewater glacier in southern Svalbard. The study is based on the results of undercut notch melt modelling, based on measurements of sea-water properties, repeated terrestrial laser scans and analysis of time-lapse camera images. There is a strong correlation between observed calving activity and modelled melt rate of the undercut notch. Measured depths of the undercut reach 4 m and vary greatly over time. The calving activity of Hansbreen was significantly lower in 2011 than in 2012, due to the persistent presence of the ice pack in Hornsund fjord, which cooled the sea surface and suppressed the wave action. Calving on Hansbreen is controlled by a local imbalance of forces at the front, due to thermo-erosional undercutting at the sea waterline. Calving activity is therefore sensitive to changes in sea-water temperature and wave height. It may be expected that calving rates will rise with increased advection of warm oceanic water to the Arctic.

Recent Deceleration of the Ice Elevation Change of Ecology Glacier (King George Island, Antarctica)

“…Despite shallow depths of the proglacial lagoon, it seems that the water depth controls termini retreat rate through enhanced calving. This may be caused by undercutting of the ice cliff [59][60][61] by relatively warm water, reaching 4 • C (Figure 7). However, given that the elevation change caused by front retreat is limited by low ice cliff height due to small water depths, this should not affect the interpretation of long-term climate effects.…”

Seasonal Variations in Ice-Front Position Controlled by Frontal Ablation at Glaciar Perito Moreno, the Southern Patagonia Icefield

“…An approach commonly taken in previous studies is to define frontal ablation rate,ȧ, as the sum ofċ andṁ, and compute the frontal ablation as a residual of dL/dt and u m (e.g., Warren et al, 2001;Haresign and Warren, 2005;Luckman et al, 2015;McNabb et al, 2015). Recent studies on tidewater glaciers have shown that calving (ċ) and melting under waterline (ṁ) vary in time under the influence of atmospheric and fjord water conditions (e.g., Benn et al, 2007;Bartholomaus et al, 2013;Luckman et al, 2015;Pȩtlicki et al, 2015). For example, it is hypothesized that crevasses filling with meltwater enhances calving in summer season due to hydrofracture (Benn et al, 2007).…”

“…Icemélange inhibits calving, which resulted in a glacier advance of 5 km over winter. Another process relevant to calving is thermal notch formation on the calving front, which is suspected as a triggering mechanism of calving (e.g., Pȩtlicki et al, 2015).…”

“…The fast flow causes formation of crevasses at the glacier surface, which causes calving. Thermal notch formation at the waterline on the calving cliff is observed at both freshwater and tidewater glaciers, and is considered to be a triggering mechanism of subaerial calving (e.g., Kirkbride and Warren, 1997;Vieli et al, 2002;Röhl, 2006;Pȩtlicki et al, 2015). When a lake is sufficiently deep, ice reaches flotation, as observed in tidewater glacier, which results in an increase in the calving rate and retreat (e.g., Naruse and Skvarca, 2000;Boyce et al, 2007;Tsutaki et al, 2011;Sakakibara et al, 2013).…”

Modeling the Controls on the Front Position of a Tidewater Glacier in Svalbard

“…Luckman et al (2015), in turn, studied two tidewater glaciers in Svalbard and found a statistical correlation between frontal ablation (the mass loss from both calving and submarine melting) and ocean temperatures between 20 and 60 m depth, suggesting that submarine melting may dominate frontal ablation. In the case of Hansbreen, thermo-erosional undercutting at the sea waterline, has been shown to play a role in calving (Petlicki et al, 2015).…”