The domino effect of the retreating Antarctic ice sheet

May 2021: Rising temperatures are accelerating the loss of the Antarctic ice sheet. This could lead to more melt water reaching the sea and lead to ripple effects that change weather patterns across the world. It highlights the non-linear impacts of climate change and underlines the need to consider the Earth system as a whole when accelerating measure to mitigate climate change.

Information

Rising temperatures are causing the Arctic ice sheet to retreat faster, leading to potential ripple effects across the globe. Even under a 2-degree Celsius warming scenario, the Antarctic will continue to lose ice throughout the 21st century. The retreating ice sheet could expose more surface land that is less reflective and leads to increased rainfall which, in turn, would reduce the ability of the climate system to maintain a large Antarctic ice sheet. The increased run-off from melting ice could disturb the hydrological cycle in the Antarctic see and increase deep-sea temperatures. Such changes may cause ‘domino effects’ that lead to knock-on impacts on other global systems such as the flow of water in the Atlantic Ocean or decrease rainfall in the Amazon rainforest.

Implications and opportunities

An accelerated ice loss in the Antarctic could dramatically change weather patterns. For example, wind normally blows over large ice sheets from the continent out to the sea. However, with increasing temperatures, this mechanism could reverse and blow winds from the sea towards the continent. This phenomenon may cause monsoons which could trigger further ice loss and higher freshwater run-offs to reach the sea. As fresh water is less dense than saltwater, it remains on the surface rather than sinking and circulating as saltwater does. This could disrupt the ocean’s hydrological cycle, causing warm water to accumulate at depth and disrupting oceanic streams across the world. This includes disrupting the El-Niño Southern Oscillation, which could lower rainfall in the Amazon. In combination with human impacts, such as deforestation, this could cause up to 50% of rainforest in the Amazon to become tropical savannas or dry forests by the end of the 21st century. The non-linear connections between the melting of the Antarctic ice sheet and rainfall patterns in the Amazon rainforest highlight the need to shift thinking towards considering the Earth system as a whole with interconnected parts, and the need for accelerated action on mitigating climate change.

Limitations

The above estimates are based on climate modelling data that compares current developments of the Antarctic ice sheet with data from the Middle Miocene (13-17 million years ago) when atmospheric carbon dioxide and global temperature reached comparative levels to those expected by the end of the 21st century and all data should be seen within the context of the model’s limitations.

Sources

Bradshaw, C.D., Langebroek, P.M., Lear, C.H., Lunt, D.J., Coxall, H.K., Sosdian, S.M. and de Boer, A.M., 2021. Hydrological impact of Middle Miocene Antarctic ice-free areas coupled to deep ocean temperatures. Nature Geoscience, pp.1-8.

Vetter, D., 2021. Just 2 degree of warming could trigger ‘climate domino effects’, new study reveals. Available at: https://www.forbes.com/sites/davidrvetter/2021/06/03/just-2-degrees-of-warming-could-trigger-climate-domino-effects-new-study-reveals/?sh=5535476c6e91