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.

Highlights

  • Melt channels in ice shelves have been hypothesized to destabilize ice shelves and were often linked to enhanced basal melt. 15 This triggered a variety of observational studies (Le Brocq et al, 2013; Langley et al, 2014; Drews, 2015; Marsh et al, 2016; Dow et al, 2018; Hofstede et al, 2021a)

  • We find basal melt rates in a melt channel and its surroundings on Filchner Ice Shelf to be up to 2.3 m a−1

  • Close to 465 the grounding line, melt rates are larger inside the channel than outside, while further downstream this relationship reverses

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Summary

Introduction

Melt channels in ice shelves have been hypothesized to destabilize ice shelves and were often linked to enhanced basal melt. 15 This triggered a variety of observational studies (Le Brocq et al, 2013; Langley et al, 2014; Drews, 2015; Marsh et al, 2016; Dow et al, 2018; Hofstede et al, 2021a). 15 This triggered a variety of observational studies (Le Brocq et al, 2013; Langley et al, 2014; Drews, 2015; Marsh et al, 2016; Dow et al, 2018; Hofstede et al, 2021a). Melt channels in ice shelves have been hypothesized to destabilize ice shelves and were often linked to enhanced basal melt. Such channels diminish with increasing distance from the grounding line at numerous locations. The main questions are if such channels are locations of enhanced basal melt and what causes them to diminish.

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