The Cryosphere Beyond a Planetary Safe Operating Space

The cryosphere, the frozen components of the Earth system, plays a vital role in regulating planetary dynamics and maintaining a stable and habitable Earth. Despite its critical importance and the rapid cryosphere degradation underway in the Anthropocene, it remains unclear whether essential functions for Earth system resilience have so far been undermined, i.e., whether cryosphere changes still remain within a ‘safe operating space’ (SOS). Here, we propose a cryosphere SOS and systematically evaluate cryosphere contributions to Earth system resilience using a planetary boundaries framework. Evidence reveals an accelerating and partly irreversible decline in cryospheric integrity, driven and amplified by positive feedbacks. Our assessment indicates that key cryospheric control variables – land ice volume, sea-ice area, permafrost mean temperature, and snow cover – are departing from Holocene-like conditions. We conclude that the cryosphere has breached its SOS and is on a trajectory that locks in long-term risks for human societies and ecosystems. Safeguarding Earth system resilience therefore, requires explicit consideration of cryosphere changes and their internal dynamics, given their ability to shift and amplify the Earth system away from Holocene-like conditions.