Abstract
Abstract. After Totten, Denman Glacier is the largest contributor to sea level rise in East Antarctica. Denman's catchment contains an ice volume equivalent to 1.5 m of global sea level and sits in the Aurora Subglacial Basin (ASB). Geological evidence of this basin's sensitivity to past warm periods, combined with recent observations showing that Denman's ice speed is accelerating and its grounding line is retreating along a retrograde slope, has raised the prospect that its contributions to sea level rise could accelerate. In this study, we produce the first long-term (∼50 years) record of past glacier behaviour (ice flow speed, ice tongue structure and calving) and combine these observations with numerical modelling to explore the likely drivers of its recent change. We find a spatially widespread acceleration of the Denman system since the 1970s across both its grounded (17±4 % acceleration; 1972–2017) and floating portions (36±5 % acceleration; 1972–2017). Our numerical modelling experiments show that a combination of grounding line retreat, ice tongue thinning and the unpinning of Denman's ice tongue from a pinning point following its last major calving event are required to simulate an acceleration comparable with observations. Given its bed topography and the geological evidence that Denman Glacier has retreated substantially in the past, its recent grounding line retreat and ice flow acceleration suggest that it could be poised to make a significant contribution to sea level in the near future.
Highlights
Over the past 2 decades, outlet glaciers along the coastline of Wilkes Land, East Antarctica, have been thinning (Pritchard et al, 2009; Flament and Remy, 2012; Helm et al, 2014; Schröder et al, 2019), losing mass (King et al, 2012; Gardner et al, 2018; Shen et al, 2018; Rignot et al, 2019) and retreating (Miles et al, 2013, 2016)
Between 1972 to 1990, observations indicate that ice accelerated 26 ± 5 % on the ice tongue (Fig. 3b) and 11 ± 5 % at the grounding line (Fig. 3c) in comparison to more limited accelerations of 9 ± 1 % and 3 ± 2 %, respectively, between 1990 and 2017. When comparing these observations against our numerical modelling experiments we find that grounding line retreat, changes in ice shelf thickness and the unpinning of ice from Chugunov Island (Fig. 5h) are all required to explain an acceleration of a comparable magnitude and spatial pattern across the Denman system
We observe a long-term acceleration of Denman Glacier across both grounded and floating sections of ice, with both the ice front advance rate and ice near the grounding line accelerating by 36±5 % and 17±4 %, respectively, between 1972 and 2017
Summary
Over the past 2 decades, outlet glaciers along the coastline of Wilkes Land, East Antarctica, have been thinning (Pritchard et al, 2009; Flament and Remy, 2012; Helm et al, 2014; Schröder et al, 2019), losing mass (King et al, 2012; Gardner et al, 2018; Shen et al, 2018; Rignot et al, 2019) and retreating (Miles et al, 2013, 2016) This has raised concerns about the future stability of some major outlet glaciers along the Wilkes Land coastline that drain the Aurora Subglacial Basin (ASB), Totten, Denman, Moscow University and Vanderford glaciers. Numerical models predict future sea level contributions from the outlet glaciers which drain the ASB over the coming decades to centuries (Golledge et al, 2015; Ritz et al, 2015; DeConto and Pollard, 2016), but large uncertain-
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
