On the evolution of an ice shelf melt channel at the base of Filchner Ice Shelf, from observations and viscoelastic modeling

Abstract

Abstract. Ice shelves play a key role in the stability of the Antarctic Ice Sheet due to their buttressing effect. A loss of buttressing as a result of increased basal melting or ice shelf disintegration will lead to increased ice discharge. Some ice shelves exhibit channels at the base that are not yet fully understood. In this study, we present in-situ melt rates of a channel which is up to 330 m high and located at the southern Filchner Ice Shelf. Maximum observed melt rates are 2.3 m a−1. Melt rates decline inside the channel along flow and turn into freezing 55 km downstream of the grounding line. While closer to the grounding line melt rates are higher within the channel than outside, this reverses further downstream. Comparing the evolution of this channel under present-day climate conditions over 250 years with its present geometry reveals a mismatch. This mismatch indicates melt rates two times higher were necessary over the past 250 years to form today's channel geometry. In contrast, forcing the model with present-day melt rates results in a closure of the channel, which contradicts observations. Time series of melt rate measurements show strong tidally-induced variability in vertical strain-rates. We found no evidence of seasonality, but discrete pulses of increased melting occurred throughout the measurement period. The type of melt channel in this study diminishes with distance from the grounding line and are hence not a destabilizing factor for ice shelves.

High-resolution simulations of the plume dynamics in an idealized 79°N Glacier cavity using adaptive vertical coordinates

“…Subglacial melting thins the glacier tongue, which can reduce the buttressing of the ice sheet, i.e., the support of the grounded glacier that is provided by the friction between the ice tongue and the lateral fjord boundaries (Goldberg et al, 2009). With a thinner ice tongue, thus less buttressing, the glacier can flow faster into the ocean, which contributes to sea level rise (Shepherd et al, 2004;Goldberg et al, 2009;Humbert et al, 2022). Furthermore, basal melting can destabilize the ice tongue, which can lead to its breakup (Rignot & Steffen, 2008); in consequence, a lot of ice would be discharged into the ocean (Shepherd et al, 2004).…”