What is the global glacier ice volume outside the ice sheets?

• Published in: Journal of Glaciology
• Main Authors: Hock, Regine, Maussion, Fabien, Marzeion, Ben, Nowicki, Sophie
• Other Authors: Aeronautics Research Mission Directorate, Norges Forskningsråd
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2023
• Subjects: Antarctic; The Antarctic; Antarc*; Antarctica; Ice Sheet; Journal of Glaciology
• Online Access: http://dx.doi.org/10.1017/jog.2023.1; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143023000011

Abstract A recent study (Millan and others, 2022 a , Nature Geoscience 15(2), 124–129) claims that ice volume contained in all glaciers outside the ice sheets and its potential contribution to sea level is 20% less than previously estimated. However, the apparent decrease is largely due to differences in choice of domain, as the study excludes 80% of the glacier area in the Antarctic periphery that was included in previous global glacier volume estimates. The issue highlights the difficulty in separating glaciers from the ice-sheet proper, especially in Antarctica, and the need for both the glacier and ice-sheet communities to develop standards and protocols to avoid double-counting in global ice volume and mass-change assessments and projections. Process-based inversion models have replaced earlier scaling methods, but large uncertainties in global glacier volume estimation remain due to the ill-posed nature of the inversion problem and poorly constrained parameters emphasizing the need for more direct ice thickness observations.