Ocean incursion and melting near ice-sheet grounding lines via high-resolution large-eddy simulations

Project Information

GLmelt

Grant agreement ID: 101109897

DOI

10.3030/101109897

Project terminated on 15 November 2024

EC signature date 2 May 2023

Start date 1 April 2024

End date 31 March 2026

Funded under

• Marie Skłodowska-Curie Actions (MSCA)

Total cost

No data

EU contribution

€ 211 754,88

Coordinated by

ECOLE NORMALE SUPERIEURE DE LYON
France

Periodic Reporting for period 1 - GLmelt (Ocean incursion and melting near ice-sheet grounding lines via high-resolution large-eddy simulations)

Reporting period: 2024-04-01 to 2026-03-31

Summary of the context and overall objectives of the project

Ice shelf melting and retreat are accelerating in polar regions because the warm off-shore waters are gaining greater access to the
base of ice shelves. Warm waters have the potential of reaching the grounding line and thereby melting it causing the retreat of the
full ice shelf, resulting in elevated rates of ice discharge into polar seas and sea level rise. The interconnection between ocean
conditions, warming, and ice melting in ice-shelf cavities is poorly understood due to the paucity of observations and turbulence-solving
simulations. This knowledge gap hinders future projections of ice changes and makes it impossible to predict if and when
tipping points will be crossed within the 21st century, as their timing critically depends on the details of ice-ocean interactions.

The Marie Curie project GLmelt (Ocean incursion and melting near ice-sheet grounding lines via high-resolution large-eddy simulations) was designed to fill the critical knowledge gap on the relationship between ice melting rate and ocean conditions by
running numerical simulations capable of resolving turbulence. The focus was on near-grounding-line regions where ice sheet sensitivity
to ice melting is greatest. The first key objective was to develop an open-source numerical model capable of resolving under-ice ocean dynamics near grounding lines. The second key objective was to investigate melt rate distributions considering a range of ice-shelf cavity configurations found in nature.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Due to some personal reasons of the fellow, the project could run only for a quarter of the scheduled duration (6 out of 24 months). Therefore, the original objectives of the project were achieved partially. Currently, we have run simulations of meltwater plumes in freshwater, as a preliminary to in saltwater. We have tested the impact of the slope angle, which varies between ice shelves, on the variations of plume properties along the ice base. We have used the Nek5000 simulation code and ran the simulations on the Pole Scientifique de Modélisation Numérique of ENS de Lyon. The results are in qualitative agreement with previous work but show quantitative discrepancies, which we explore and explain in detail in an upcoming manuscript that will be submitted to the Journal of Fluid Mechanics. We have also run simulations of subglacial lakes, whose dynamics share similar physical ingredients as sub-ice oceans and are of interest to several team members at the Laboratoire de Physique of ENS de Lyon. In essence, we have:
a) developed and validated a numerical model capable of resolving under-ice ocean dynamics in the near-grounding-line region. However, as a starting point, the effect of salinity was not taken into consideration and a freshwater environment was studied. Further, direct numerical simulation (DNS) was used in these simulations instead of the originally proposed large-eddy simulation (LES) model.
b) a manuscript targeting the prestigious "Journal of Fluid Mechanics" is in its final phase of preparation
c) preliminary results of this study were presented in FRISP 2024 and NEK User Meeting

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Our work investigates in detail, thanks to the use of high-resolution direct numerical simulations, processes controlling the evolution of plume properties along the ice base. Notably, we have found that buoyancy fluctuations generate significant turbulent kinetic energy, i.e. of the same order of magnitude as mechanical shear. We report on plume properties in the freshwater case, complementing recent studies in saltwater, and discuss the agreement, far from perfect, with the theoretical meltwater plume model.