This interesting study investigates the vulnerability of the Greenland ice sheet to climate warming. Specifically, the article addresses what it takes to make the Greenland ice sheet disappear—an event that would cause several metres of sea-level rise. The authors show that a tipping-point behaviour can be identified in their model, demonstrating that once a threshold has been crossed, Greenland becomes almost completely ice-free.

This study addresses an important question regarding the stability of ice shelves, a question that is highly relevant for Greenland and Antarctica. Using a unique combination of observations, the authors document extensive thinning and extremely high basal melt rates at the floating tongue Nioghalvfjerdsbræ, North Greenland, an important and fast-changing part of the Greenland Ice Sheet. The increase in melt rates are suggested to be caused by an increase in surface melt that is funneling surface water under the ice shelf.

This study provides new estimates of historical and projected changes in pan-Arctic runoff, with emphasis on the impact of permafrost changes and sub-surface flows on large scale hydrology. The impact of permafrost change on hydrological processes is a key uncertainty facing the cold regions hydrology community, and requires comprehensive model-based analysis as presented in this study. The analysis also addresses changes to the terrestrial runoff contribution to the freshwater budget of the Arctic, and so is of interest to a wide range of disciplines.

This study brings together an impressive amount of data to come up with an updated estimate of global glacier loss until the year 2100. This is an important result in a climate change context, and one of a global dimension.

This manuscript addresses the stability of one of the most vulnerable regions of West Antarctica. Focusing on the so-called "doomsday" glacier, Thwaites glacier, the authors use a novel model that combines ice sheet and ocean to investigate how the ice melts at the pinning point - the points where the glacier is "pinned" to the bedrock.

The history and extent of the Greenland ice sheet is a widely debated and poorly understood question. In this study, the authors show that the childhood of the Greenland ice sheet took place in the southern and eastern highlands of Greenland, and further suggest that the continental ice sheet we observe today first emerged between 7 million years and 2.6 million years ago.

The study is one of the first to model fractures in ice sheets - a fascinating and visually stunning aspect of ice sheets. The model shows that crevasses may transport large volumes of water to the bed of a glacier very quickly and captures the opening of the crevasses due to the water inflow. The impact of surface lakes on the Greenland ice sheet dynamics and mass loss is now better described.

For most countries dealing with the consequences of sea-level rise, a constructive discussion about actionable science is critical. There is a need to strengthen the lines of evidence for sea-level projections and at the same time there is a strong need for practitioners to understand which science they should rely on to plan adaptation actions. This manuscript outlines when scientific results may be considered actionable and discusses the risks in using novel results to inform decision-making. The case study discussed in the manuscript is also valid for other climate-change-related fields.