Dec 3 2020
A new study has shown how climate change could result in irrevocable sea-level rise with a continuous increase in temperatures and the continuous decline in the Greenland ice sheet.
Greenland town. Image Credit: National Centre for Atmospheric Science.
Researchers from the University of Reading and the National Centre for Atmospheric Science (NCAS) have recently published the most elaborate study of the Greenland ice sheet to date, in The Cryosphere journal. They describe how the enormous Greenland ice sheet experiences a point of no return, beyond which it will no longer completely regrow, thereby altering sea levels across the globe permanently.
For scenarios where global warming exceeds 2 °C, which is the target set by the Paris Agreement, the new study demonstrates that considerable ice loss is predicted, with several meters of increase in the global sea level lasting for tens of thousands of years. The warmer the climate, the higher the increase in sea level.
Moreover, even if temperatures return to existing levels after some point in time, researchers have demonstrated that the Greenland ice sheet will never be able to regrow completely once it melts greater than a critical point. Once that point is reached, sea levels would permanently stay 2 m higher compared to existing levels, irrespective of other factors contributing to sea-level rise.
The reason is the huge size of the ice sheet has a significant influence on its local climate, and as it reduces, Greenland would experience less snowfall and warmer temperatures. As soon as the ice-sheet withdraws from the island’s Northern part, the region would continue to be ice-free.
Our experiments underline the importance of mitigating global temperature rise. To avoid partially irreversible loss of the ice sheet, climate change must be reversed—not just stabilised—before we reach the critical point where the ice sheet has declined too far.
Jonathan Gregory, Professor and Climate Scientist, University of Reading and National Centre for Atmospheric Science
Rising Sea Levels
The ice sheet of Greenland is seven times the area of the United Kingdom and stores a huge amount of the Earth’s frozen water. At the present melting rates, it contributes nearly 1 mm to sea level annually and accounts for about one-quarter of the complete sea-level rise.
From 2003, regardless of seasonal periods of growth, the ice sheet of Greenland has lost three and a half trillion tons of ice.
Sea-level rise is considered to be one of the most severe impacts of climate change, posing a hazard to coastal areas across the globe, and threatening the lives of millions of people living in low-lying areas. Florida, eastern England, and Bangladesh are some of the several areas known to be specifically susceptible.
According to researchers, to prevent the irrevocable sea-level rise that would be caused by the melting, climate change must be reversed before the Greenland ice sheet reduces to the threshold mass, which would be reached in around 600 years at the greatest rate of mass loss that falls in the possible range of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change.
The researchers investigated the ice sheet with the help of a computer model that integrates climate and ice-sheet models to mimic the impacts of Greenland ice sheet melting below a range of possible increases in temperature, varying from least warming to worst-case scenarios.
Under all future climates such as the current or warmer, the ice sheet decreased in size and contributed to a certain degree of sea-level rise.
Most significantly, there were scenarios where the ice sheet melting could be reversed. However, they depend on actions to mitigate global warming before it becomes too late.
Journal Reference
Gregory, J. M., et al. (2020) Large and irreversible future decline of the Greenland ice sheet. The Cryosphere. doi.org/10.5194/tc-14-4299-2020.