Sensitivity of East Antarctic outlet glaciers to future climate change

Overview

Dynamic changes in marine-terminating outlet glaciers in Greenland and West Antarctica indicate that their contribution to sea level rise has accelerated in the last two decades (Shepherd et al., 2012). This is largely due to increased velocity, thinning and retreat, which has been linked to both atmospheric and oceanic warming. In contrast, the world’s largest ice sheet – the East Antarctic Ice Sheet (EAIS) – has generally been perceived as much less vulnerable. However, mass loss has been detected in some regions (e.g. Wilkes Land: Rignot et al., 2019), and recent work suggests that its marine-terminating outlet glaciers respond rapidly to external forcing at decadal time-scales (Miles et al., 2013; 2016; 2017), even though the precise contribution of oceanic versus atmospheric forcing is unknown. This suggests that the EAIS may be more vulnerable to future climate change than previously thought, and numerical modelling suggests that some regions grounded below sea level may be close to the threshold of instability (Mengel and Levermann, 2014).

Despite growing evidence for the potential vulnerability of the EAIS, and unlike in Greenland and West Antarctica, there are very few detailed observations of many of its marine-terminating outlet glaciers (Figure 1). As such, we know very little about what controls the behaviour of outlet glaciers in the EAIS. To address this issue, the overall aim of this project is to use remote sensing observations and numerical modelling to explore the sensitivity of major East Antarctic outlet glaciers to oceanic and atmospheric forcing.

The primary research questions are:
• Are EAIS outlet glaciers more sensitive to atmospheric or oceanic forcing?
• Do changes in sea-ice substantially influence their behaviour?
• How does outlet glacier response to forcing vary between different climatic or topographic settings?
• How do specific glacier characteristics increase or decrease sensitivity to various forcings (e.g. the presence of ice tongues, ice shelves, or different topographic settings)?

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Image Captions

Figure 1: Major outlet glaciers draining the East Antarctic Ice Sheet in Victoria Land.

Methodology

The project will focus on large marine-terminating outlet glaciers that represent the major types of climatic and topographic settings within the EAIS. Initially, a variety of remote sensing data (e.g. Landsat, Sentinel, ICESAT2) will be used to determine changes in frontal position, ice velocity and ice surface elevation over the last few decades (depending on data availability), with annual to sub-annual resolution available from the 1990s. Temporal trends will then be compared to possible atmospheric (air temperatures, precipitation) and oceanic forcing (temperatures at various depths, sea ice concentrations). These data will be obtained from readily available satellite and reanalysis products (e.g. NCEP/NCAR climate reanalysis data; Hadley Centre EN3 ocean temperature data; etc.), and, where available, meteorological and ship-based measurements. Evaluation and statistical analysis of these empirical datasets will be used to develop a series of hypotheses to explain outlet glacier behaviour in the different climatic and topographic settings, which will then be tested using numerical modelling.

The modelling will likely apply state-of-the-art 3D approaches such as Úa, BICICLES or PISM depending on the chosen problem or on the particular interests of the student. These models all have robust, but different treatments of marine grounding lines and glacier termini and have been widely applied to Antarctic problems [e.g. Mendel and Levermann, 2014; Cornford et al., 2015; De Rydt et al., 2019). The modelling approach will allow the application of oceanic and atmospheric forcing processes, such as surface melt, ocean melt, changes in ice shelf or sea-ice buttressing, and basal lubrication in order to test the sensitivity of the simulated glaciers. Initially, the student will build reference states for each outlet glacier and use inversion techniques to best reproduce the remotely sensed observations of their recent behaviour. We will then apply perturbation experiments to examine the sensitivity of outlet glaciers to different forcing processes. A second component will be to explore their future behaviour under different climatic and oceanic warming scenarios, using an ensemble of runs to explore different parameter ranges. The candidate will also explore the feasibility of generating regionally-integrated assessments of glacier response for specific sectors of the ice sheet that our analysis indicates might be particularly vulnerable.

Project Timeline

Year 1

Training in Remote Sensing and GIS; collection and analysis of remote sensing datasets of major East Antarctic outlet glaciers

Year 2

Collection and analysis of atmospheric and oceanic datasets; set-up numerical modelling and perform validation against observations

Year 3

Sensitivity experiments of future behaviour using numerical modelling prepare research papers; conference attendance

Year 3.5

Further modelling and submission of research papers and thesis; conference attendance

Training
& Skills

The student will receive both generic and bespoke training in Remote Sensing and GIS, including software such as ERDAS Imagine, ArcGIS and NEST Array. Numerical modelling skills will be provided via ‘hands-on’ training from the supervisory team, and specific training in Matlab and statistical software (e.g. Stata), supplemented with an internationally-recognised summer school in Karthaus and numerical modelling training workshops. Broader transferable skills (e.g. communicating science, thesis writing, writing for publication, presentation skills) will be developed through various training events at Durham University offered by IAPETUS.

References & further reading

Cornford, S. L. et al. (2015) Century-scale simulations of the response of the West Antarctic Ice Sheet to a warming climate. The Cryosphere, 9, 1579-1600.
De Rydt, J. et al. (2019) Calving cycle of the Brunt Ice Shelf, Antarctica, driven by changes in ice shelf geometry. The Cryosphere, 13, 2771-2787
Mengel, M. & Levermann, A. (2014) Ice plug prevents irreversible discharge from East Antarctica. Nature Climate Change, 4, 451-455.
Miles et al. (2013) Rapid, climate-driven changes in outlet glaciers on the Pacific coast of East Antarctica. Nature, 500, 563-566.
Miles, A.W.J. et al (2016) Pan-ice sheet glacier terminus change in East Antarctica reveals sensitivity of Wilkes Land to sea-ice changes. Science Advances, 2 (5), e1501350.
Miles, A.W.J. et al. (2017) Simultaneous disintegration of outlet glaciers in Porpoise Bay (Wilkes Land), East Antarctica, driven by sea-ice break-up. The Cryosphere, 11, 427-442.
Rignot et al. (2019) Four decades of Antarctic Ice Sheet mass balance from 1979-2017. Proceedings of the National Academy of Sciences, 116 (4), 1095-1103.
Shepherd et al. (2012) A reconciled estimate of ice sheet mass balance. Science, 338, 1183-1189.

Further Information

Professor Chris R. Stokes
Durham University
E-mail: c.r.stokes@durham.ac.uk
Tel. 0191 334 1955

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