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Many glaciers on the Antarctic Peninsula have retreated and accelerated in recent decades. Here we show that there has been a widespread, quasi-synchronous, and sustained increase in grounding line discharge from glaciers on the west coast of the Antarctic Peninsula since 2018. Overall, the west Antarctic Peninsula discharge trends increased by over a factor of 3, from 50 Mtyr-2 during 2017 to 2020 up to 160 Mtyr-2 in the years following, leading to a 7.4 % increase in grounding line discharge since 2017. The acceleration in discharge was concentrated at glaciers connected to deep, cross-shelf troughs hosting warm-ocean waters, and the acceleration occurred during a period of anomalously high subsurface water temperatures on the continental shelf. Given that many of the affected glaciers have retreated over the past several decades in response to ocean warming, thereby highlighting their sensitivity to ocean forcing, we argue that the recent period of anomalously warm water was likely a key driver of the observed acceleration. However, the acceleration also occurred during a time of anomalously high atmospheric temperatures and glacier surface runoff, which could have contributed to speed-up by directly increasing basal water pressure and, by invigorating near-glacier ocean circulation, increasing submarine melt rates. The spatial pattern of glacier acceleration therefore provides an indication of glaciers that are exposed to warm-ocean water at depth and/or have active surface-to-bed hydrological connections; however, many stages in the chain of events leading to glacier acceleration, and how that response is affected by glacier-specific factors, remain insufficiently understood. Both atmospheric and ocean temperatures in this region and its surroundings are likely to increase further in the coming decades; therefore, there is a pressing need to improve our understanding of recent changes in Antarctic Peninsula glacier dynamics in response atmospheric and oceanic changes in order to improve projections of their behaviour over the coming century. [ABSTRACT FROM AUTHOR]

We observe the evacuation of 11-year-old landfast sea ice in the Larsen B embayment on the East Antarctic Peninsula in January 2022, which was in part triggered by warm atmospheric conditions and strong offshore winds. This evacuation of sea ice was closely followed by major changes in the calving behaviour and dynamics of a subset of the ocean-terminating glaciers in the region. We show using satellite measurements that, following a decade of gradual slow-down, Hektoria, Green, and Crane glaciers sped up by approximately 20 %–50 % between February and the end of 2022, each increasing in speed by more than 100 ma-1. Circumstantially, this is attributable to their transition into tidewater glaciers following the loss of their ice shelves after the landfast sea ice evacuation. However, a question remains as to whether the landfast sea ice could have influenced the dynamics of these glaciers, or the stability of their ice shelves, through a buttressing effect akin to that of confined ice shelves on grounded ice streams. We show, with a series of diagnostic modelling experiments, that direct landfast sea ice buttressing had a negligible impact on the dynamics of the grounded ice streams. Furthermore, we suggest that the loss of landfast sea ice buttressing could have impacted the dynamics of the rheologically weak ice shelves, in turn diminishing their stability over time; however, the accompanying shifts in the distributions of resistive stress within the ice shelves would have been minor. This indicates that this loss of buttressing by landfast sea ice is likely to have been a secondary process in the ice shelf disaggregation compared to, for example, increased ocean swell or the drivers of the initial landfast sea ice disintegration. [ABSTRACT FROM AUTHOR]