New research from the British Antarctic Survey shows that the West Antarctic ice sheet will melt faster this century, regardless of fossil fuel decline. Simulations show that even with the best global temperature controls, melting would be three times faster than in the 20th century. This will have serious consequences for sea levels and coastal communities around the world.
The rate of melting of the West Antarctic ice sheet is predicted to increase significantly this century, regardless of fossil fuel cuts. While the future looks challenging, reducing reliance on fossil fuels remains critical to adapting to and mitigating climate change.
Research from the British Antarctic Survey (BAS) published this week in the journal Nature Climate Change shows that the West Antarctic Ice Sheet will continue to melt at an accelerated rate for the rest of the century, no matter how we reduce fossil fuel use. A large acceleration in ice melt is now likely unavoidable, meaning Antarctica's contribution to sea level rise is likely to increase rapidly in the coming decades.
Scientists ran simulations on the UK's National Supercomputer to examine ocean-driven melting of the West Antarctic Ice Sheet: how much is inevitable and must be adapted to; how much melting is still something the international community can control by reducing greenhouse gas emissions.
Taking into account climate variability such as El Niño, they found no significant differences between medium-range emissions scenarios and the most ambitious target of the 2015 Paris Agreement. Even under a best-case scenario of global temperature rise of 1.5°C, melting would be three times faster than in the 20th century.
The West Antarctic Ice Sheet is losing ice and is the largest contributor to sea level rise in Antarctica. Previous modeling found that warming in the Southern Ocean, particularly in the Amundsen Sea region, may be responsible for the ice loss. The total ice volume of the West Antarctic Ice Sheet is enough to raise global average sea level by 5 meters.
Millions of people around the world live near coasts, and these communities will be greatly affected by rising sea levels. A better understanding of future changes will allow decision-makers to plan ahead and adapt more easily.
Lead author Dr Caitlin Noten, a researcher at the British Antarctic Survey, said: "It looks like we have lost control of the melting of the West Antarctic Ice Sheet. Action on climate change would have been needed decades ago if we wanted to maintain its historical status. The good thing is that by recognizing this situation early, the world will have more time to adapt to the coming sea level rise. If you need to abandon or significantly transform coastal areas, 50 years of preparation time will make all the difference."
The team simulated four future scenarios for the 21st century, as well as one historical scenario for the 20th century. These future scenarios either stabilize global temperature rise at the 1.5°C and 2°C targets set by the Paris Agreement, or follow the medium- and high-carbon emission standard scenarios.
All scenarios lead to significant future widespread warming of the Amundsen Sea and increased ice shelf melting. The three lower-range scenarios follow nearly identical paths through the 21st century. Even in the best-case scenario, the Amundsen Sea is warming about three times faster, melting the floating ice shelves that stabilize inland glaciers, although the floating ice shelves did start to flatten by the end of the century.
In the worst-case scenario, the ice shelves melt more severely than otherwise, but only after 2045. The authors note that this scenario of rapid increases in fossil fuel emissions is considered unlikely.
The study's future projections of melting of the Amundsen Sea ice shelf are sobering, but do not diminish the importance of mitigating the effects of climate change.
"We must not stop our efforts to reduce our dependence on fossil fuels. In the long term, everything we do now will help slow the rate of sea level rise. The slower the rate of sea level change, the easier it will be for governments and societies to adapt, even if it cannot be stopped," Noten warned.