How glaciers would look like today in a world without Us?
This work aims to quantify the anthropogenic impact on the Argentière Glacier with respect to changes related to climate natural variability. We use a detection-attribution approach to produce retrospective ensemble simulations of the climate and the glaciers, with and without greenhouse gasses and aerosol forcings over 1850–2014. The time of emergence of the anthropogenic signal, that is, the date when it becomes statistically distinguishable from climate natural variability, occurs in 1979 for temperature in the Argentière location, with warming reaching 1.35°C in 2014 relative to 1850. The emergence of the anthropogenic signal occurs later for the glacier changes: the snout position is still compatible with natural variability in 2014, whereas for the glacier mass change, it occurred in 2008, ∼30 years after that of the temperature. In 2014, 66% [21%–111%] of the total mass loss since 1850 can be attributed to anthropogenic activities, a result that is dependent on the natural variability estimated from the climate model used in this study. The combination of increasing concentration of greenhouse gasses and decreasing aerosols in the atmosphere led to an acceleration of the glacier retreat over the last 3 decades.
Read more: Clauzel L., M. Ménégoz, A. Gilbert, O. Gagliardini, D. Six, G. Gastineau and C. Vincent, 2023. Sensitivity of glaciers in the European Alps to anthropogenic atmospheric forcings: Case study of the Argentière Glacier. Geophysical Research Letters, 50, e2022GL100363. DOI:10.1029/2022GL100363
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Ice rises and ice rumples are locally grounded features found in coastal Antarctica and are surrounded by otherwise freely floating ice shelves. In both cases, local highs in the bathymetry are in contact with the ice shelf from below, thereby regulating the large-scale ice flow, with implications for the upstream continental grounding line position. We investigate ice rises and ice rumples using a three-dimensional full Stokes ice flow model under idealised scenarios. The simulations span end-member basal friction scenarios of almost stagnant and fully sliding ice at the ice–bed interface. We analyse the interaction with the surrounding ice shelf by comparing the deviations between the non-local full Stokes surface velocities and the local shallow ice approximation (SIA). Deviations are generally high at the ice divides and small on the lee sides. On the stoss side, where ice rise and ice shelf have opposing flow directions, deviations can be significant. During sea level increase and decrease experiments, transitions from ice rise to ice rumple occur (and vice versa) and divide migration is more abrupt the higher the basal friction. We identify a hysteretic response of ice rises and ice rumples to changes in sea level, with grounded area being larger in a sea-level-increase scenario than in a sea-level-decrease scenario. This hysteresis shows not only irreversibility following an equal increase and subsequent decrease in sea level but also that the perturbation history is important in determining the current ice rise or ice rumple geometry.
