Breaching 2 °C warming could lead to significant melting of the Filchner Ronne Ice Shelf

The Filchner Ronne Ice Shelf is the second largest ice sheet on Earth and covers the southern part of the Weddell Sea, which borders Antarctica. Under the eastern portion of the ice shelf lies the Filchner Trough, an area of deeper water — up to 1600 metres deep in places — on the Antarctic continental shelf. The water temperature within the trough is regulated by the Antarctic Coastal Current, which causes a seasonally varying amount of warm deep water to flow into the trough. Pulses of warm deep water — distinct periods of time when increased volumes of this water flow into the Filchner Trough — have been linked with increases in the melting of the base of the ice shelf above.

Vanessa Teske and colleagues modelled how the amount of warm deep water entering the Filchner Trough changed between 2015 and 2100 under four different climate scenarios based on the IPCC’s Shared Socioeconomic Pathways (SSPs). Under the best scenario (SSP1-2.6, which meets the Paris climate agreement threshold of no more than 2 °C of global warming compared to the pre-industrial period), the frequency of the pulses increased, and the mean temperature in the trough rose 0.5 °C above the 1850 – 2014 mean by 2100. However between each pulse, the temperature in the trough returned to closer to the 1850 – 2014 mean, limiting the melting of the ice shelf. In the other scenarios, which modelled greater mean global temperature increases, the pulses increased in frequency until the trough was mostly filled with warm deep water year round.

“Two of the four climate scenarios (SSP3-7.0 and SSP5-8.5) lead to a regime change in the Filchner Trough before the end of this century. The cold shelf water that currently fills the trough will be replaced by warmer water originating in the Antarctic Circumpolar Current. This warming has a major influence on the melting behaviour of the ice sheet in East Antarctica. But even the more moderate scenario SSP2-4.5 already shows a warming of the mean water temperature in the Filchner Trough by 1°C,” Vanessa Teske explains the modelling results. “Only the 2°C climate target-compliant scenario (SSP1-2.6) does not appear to lead to a regime change in the Filchner Trough for the time being.”

The authors warn that if this water temperature increase in the trough occurred, there would be a strong increase in the melting rate of the base of the Filchner Ronne Ice Shelf. This would lead to a significantly increased contribution to global sea-level rise.

Original Publication:

Vanessa Teske, Ralph Timmermann, Tido Semmler: Subsurface warming in the Antarctica‘s Weddell Seas can be avoided by reaching the 2°C warming target. Communications Earth & Environment (2024). DOI: 10.1038/s43247-024-01238-5