General Information

The Institute of Geosciences and Environment (IGE), Grenoble, France, is advertising a 3-year PhD position.

The PhD candidate will produce and analyse ocean—ice-sheet coupled simulations in the Amundsen Sea sector, West Antarctica, with the aim to better understand decadal variability and future projections. More information is provided below.

The PhD candidate will be hired by University Grenoble Alpes and supervised by Nicolas Jourdain at IGE. The position will start in October 2020.

We are looking for a highly motivated candidate with a Master’s degree (or equivalent) in environmental science, fluid dynamics, mechanics/energetics, or a related field. A strong interest in programming is required, but previous experience in numerical modelling is not compulsory.

Applicants should send their CV and transcripts of the 2 previous years to before May 22nd.

PhD project and scientific context

The West Antarctic ice sheet has lost mass over the last few decades and has thus contributed significantly to global sea level rise. Warming of the oceanic sub-surface has caused an increase in melting under floating ice shelves, particularly in the Amundsen Sea (Jenkins et al. 2018). This has led to a retreat of the glaciers fronts and grounding lines (Mouginot et al. 2014; Rignot et al. 2014), and to the acceleration of their flow, which possibly indicates the premises of marine ice-sheet instabilities (Favier et al. 2014; Joughin et al. 2014). However, the role of natural variability versus anthropogenic forcing is still unclear. This is related to both a lack of understanding of ocean processes near the ice sheet and to major uncertainties on ice dynamics.

On the one hand, ice-shelf basal melting in the Amundsen Sea is strongly linked to exchanges between the region of the Circumpolar Antarctic Current, which contains a mass of relatively warm water (CDW, for Circumpolar Deep Water), and the shallower continental shelf (typically 500 to 1000m) on which ice streams come afloat. These exchanges are related to the presence of eddies, tides, interactions between the mean current and bathymetry, and melt-induced circulation under the ice shelves (Stewart et al. 2018; Jourdain et al. 2017). On interannual and decadal scales, atmospheric convection in the equatorial Pacific modulates zonal wind friction over the Amundsen Sea continental slope, which affects the CDW transport to ice-shelf bases (Holland et al. 2019).

On the other hand, ice dynamics are strongly influenced by bedrock topography: the direction of the bedrock slope with respect to the ice-stream direction determines the unstable nature of an ice flow (Schoof 2007; Pattyn et al. 2012), while lateral buttressing of ice shelves in bays tends to stabilize ice flows (Gudmundsson 2013). Consequently, the evolution of glaciers over the past and future decades is highly dependent on the initial position of glaciers relative to bedrock.

In this PhD work, the student will first revisit the evolution of coastal and sub-glacial ocean dynamics, as well as glacial dynamics in recent decades (1960-2020), and since the beginning of the 20th century. This will be done by first studying the variability of ocean circulation and sub-glacial melting simulated by the NEMO ocean model (Mathiot et al. 2017). A physical analysis of a set of simulations with different parameters and forcing conditions will be performed to better understand the interplay of processes that trigger melt anomalies, but also the mechanisms that stop them.

Then, the coupled ocean/ice-sheet model NEMO-Elmer/Ice (Favier et al. 2019) will be used in a configuration representing the Amundsen region. Several assumptions will be made to reconstruct plausible ice-sheet state before the 1990s, which is poorly known. The PhD candidate will use this coupled modelling framework to simulate the contribution of the Amundsen sector to global mean sea level over the coming decades.

Local and international collaborations

IGE, previously known as LGGE, gathers renowned experts in Antarctic Sciences, on topics including paleo-climate from ice cores, glaciers and ice-sheet dynamics, physical oceanography and climate, as well as atmosphere and snow physics (among other fields). The modelling work will be carried out in close collaboration with NEMO experts at IGE (Pierre Mathiot, Julien Le Sommer, Jean-Marc Molines) and in France (NEMO team at LOCEAN-IPSL in Paris) and with Elmer/Ice experts at IGE (Fabien Gillet-Chaulet, Olivier Gagliardini, Gaël Durand).

This PhD project will take place within the French ANR project called EIS (Elmer Ice Sheet, Jan. 2020 - Dec. 2023, partnership with LSCE and CNRM), and will benefit from a large collaboration network thanks to the PROTECT H2020 project (Aug. 2020 - Jul. 2024, 25 european partners).