2°C Insufficient to Prevent Substantial Ice Sheet Loss and Sea-Level Rise from Both Poles

Nature Communications, 14 February 2023

This study used a new integrated model that includes the complex interactions between ice sheets, oceans and the atmosphere; importantly, it looked at both ice sheets together, and the interactions between them. The authors found that West Antarctica and Greenland will cross an irreversible threshold if global temperatures reach 1.8°C even temporarily, committing these ice sheets to increased ice loss and accelerating sea-level rise for several centuries, even if temperatures return to current levels. According to this study, limiting warming to below 2°C will therefore not be enough to slow the rate of sea-level rise over the next 130 years. Only the very low greenhouse gas emissions scenario, with temperatures peaking around 1.6°C and leveling off below 1.5 °C by the end of this century, avoids long-term acceleration of sea-level rise from the Earth’s two great ice sheets.

With high emissions, Greenland and Antarctica each contribute 60–70 cm to global sea-level rise over the next 130 years. By 2150, Greenland is contributing about 1cm/year SLR and Antarctica about 2cm/year, producing a total of 3cm/year from the two ice sheets alone, with rates still accelerating. (By comparison, sea-level rise today from all sources — ice sheets, glaciers and thermal expansion — is around 0.4cm/year.) Even though warming does begin to slow after 2100 under medium and high emissions scenarios, ice sheet melting and related sea-level rise continue to accelerate instead. For Greenland, this is mostly caused by continued and accelerating surface melting; at the other pole, a combination of factors (irreversible loss of ice shelves, warmer ocean temperatures) increase ice loss and sea-level rise from Antarctica. The study showed that if today’s high emissions continue, the huge Ross Ice Shelf — Antarctica’s largest — disintegrates completely by 2100, releasing much of the ice sheet behind to flow into the ocean. In the long term, even with medium emissions Antarctica loses substantial ice by 2500, and Greenland melt accelerates for over 250 years after peak temperatures are reached. Especially for Antarctica, only very low emissions prevent substantial ice loss over the next several centuries.

These findings underscore that even small-scale processes in the ocean or atmosphere can play a crucial role in the large-scale response of an ice sheet. With hundreds of millions of people living in vulnerable coastal areas across the world, reducing emissions today will help prevent substantial ice loss from polar ice sheets and slow sea-level rise for centuries to come.

https://www.nature.com/articles/s41467-023-36051-9