Climate variability accelerates Thwaites Glacier collapse

Over the last two decades, the contribution of the West Antarctic Ice Sheet to sea level rise has doubled, and a substantial fraction of this mass loss has been linked to climate variability. Here, we analyse the future behaviour of Thwaites glacier under a noisy climate and show that climate variability alone is sufficient to trigger its collapse within approximately 300 years, while under present-day climate conditions, a complete disintegration occurs after 500-700 years. Low-frequency modes of ocean variability may accelerate disintegration by up to 250 years. Furthermore, from our simulations ensemble, we identify a “safety band" located within 60~km upstream of the current grounding line. Beyond this band, Thwaites Glacier undergoes a self-sustained retreat irrespective of ambient climate conditions. Grounding lines that remain within this band, however, still allow for glacier slowdown and even re-advance in the absence of ocean melt or if sub-shelf accretion occurs. The window for effective climate mitigation therefore remains open only while the grounding line stays within this safety band. Our results provide a robust metric for assessing glacier stability and highlight the need to account for climate variability in sea-level rise projections.