The triggers of the disintegration of Voyeykov Ice Shelf (2007), Wilkes Land, East Antarctica, and its subsequent evolution

Abstract:

Understanding the controls on the dynamics and disintegration of ice shelves and glacier tongues is crucial to predicting future inland ice loss from the Antarctic Ice Sheet and its contribution to sea-level rise. Voyeykov Ice Shelf (VIS) in Wilkes Land, East Antarctica, lost >2000 km² of ice during a disintegration event in late March/early April 2007. Here, we investigate changes in its structure, thickness and velocity during the seven years preceding its disintegration and its evolution until April 2020 using Landsat and Envisat ASAR imagery, ICESat laser altimetry and annual velocity mosaics. We also investigate potential external triggering factors by comparing the timing and scale of changes in a range of datasets including air temperature and wind-field anomalies from climate reanalysis, surface melt predicted by a regional climate model and sea ice concentrations. We show that disintegration was preceded by widening and propagation of major rifts extending to the calving front and ice thinning (maximum mean rate -0.82 myr^-1) 10 km upstream of the grounding line between 2003-2008. Our analysis suggests ice shelf disintegration was likely triggered by mélange removal linked to an atmospheric warm anomaly and a less extensive latent heat polynya, which triggered sea ice breakout and the intrusion of warmer surface waters. Katabatic wind-driven ponding weakened the multiyear landfast sea ice adjacent to VIS and primed it for breakout. The example of VIS highlights the need for ice shelf and ice sheet models to account for mélange-ice shelf interactions in the context of predicted future warming. An important implication is that surface melt pond-driven hydrofracturing is not always a necessary precursor to ice shelf collapse.