Tipping Points in the Cryosphere

The accelerating loss of the cryosphere, which holds 70% of the world’s freshwater in all its forms – sea ice, lake ice, mountain glaciers, the polar ice sheets and their ice shelves, snow and permafrost - is one of the clearest planet-wide consequences of global warming so far.

The loss of even parts of these key components of the cryosphere would result in severe impacts for coastal communities, infrastructure and ecosystems through permanent inundation of the lowest-lying areas and by increasing the frequency of flooding, and requires an extensive and long-term commitment to adaptation to limit these impacts. By the end of the century one billion people living in coastal areas could be impacted (IPCC 2023).

There is ample evidence for abrupt change in the past, especially for the glaciers and ice sheets. Moreover, changes in land-ice are, for the most part, are irreversible on human-to-glacial timescales. In fact, both the Greenland and Antarctic ice sheets show strong hysteresis behaviour, meaning that once certain parts of the ice sheets are gone, it would take much colder temperatures to regain the ice.

What characterises tipping dynamics in the cryosphere most, however, are the nested timescales, and possibility of tipping cascades between elements, ranging from mere hours-decades in the sea-ice, up to millennia for the ice sheets with consequences on a range of spatial scales: as global warming accelerates, there is an increasing discrepancy between the rapid forcing, and the comparably long response times in the cryosphere. This clash in timescales gives rise to a massive gap between the observed and committed impacts, in particular when it comes to sea-level rise. While typical projections focus on sea-level changes within this century, recent evidence suggests that the bulk of sea-level rise - even while triggered within this century - will unfold over hundreds, if not thousands of years.