Dwindling Antarctic sea ice is driving more storms in the Southern Ocean, a new study has found, raising concerns about potential disruptions to global weather patterns.
The study by researchers from the UK’s National Oceanography Centre warns that the record loss of Antarctic sea ice in 2023 has led to a doubling of ocean heat loss to the atmosphere and a marked increase in storms across the Southern Ocean.
This intense heat exchange has added up to seven extra storm days a month in some areas, according to the study, published in the journal Nature on Wednesday. It has also altered the density of surface water, potentially disrupting deep ocean circulation, which plays a role in regulating temperatures and weather patterns.
“The massive increase in ocean heat loss to the atmosphere is increasing the density of water at the sea surface to values not previously seen in the newly ice-free regions,” Professor Simon Josey, lead study author and an expert on ocean-atmosphere interactions, said.
Antarctic sea ice acts as a “winter blanket” over the Southern Ocean, insulating it from the cold atmosphere and regulating heat exchange.
When this ice diminishes, heat from the ocean escapes into the atmosphere, causing surface water to cool and become denser. This process can trigger a cascade of effects, from increased storm activity to shifts in the deep ocean circulation that help regulate the planet’s climate.
The 2023 sea ice cover was 50 to 80 per cent lower than the winter average recorded between 1991 and 2020 in key regions like the Weddell, Ross, and Bellingshausen seas. This decline was coupled with a phase shift in peak ocean heat loss which now occurs later in the year, during June, instead of the traditional peak in late April.
“Based on our study, years of low sea ice like this will continue to have more storms and greater changes to ocean properties that could impact the wider ocean circulation,” Dr Josey said.
Antarctic sea ice loss not only affects local ecosystems such as penguin populations, but it also poses significant risks to global climate stability.
Although the immediate effects of declining sea ice are felt in the Southern Ocean, the study shows potential global consequences. As surface water density in the Southern Ocean increases, it could disrupt the formation of Antarctic bottom water, a critical part of the global conveyor belt that drives ocean currents and regulates the distribution of heat and nutrients worldwide.
Dr Andrew Meijers, co-author of the study from the British Antarctic Survey, said this process could further accelerate ice melt.
“The cooling and subsequent sinking of waters previously covered by sea ice has the potential to release deeper warm waters that would normally be kept away from ice by an insulating surface layer,” he explained. “In turn, this has the potential for increasing sea ice melt in future years.”
Climate impacts could ripple out far beyond the Antarctic. Enhanced heat loss in the Southern Ocean could influence atmospheric circulation, potentially altering weather patterns as far away as the Northern Hemisphere and the tropics.
Previous studies have raised concerns over the impact of Antarctic sea ice loss on shifts in global climate systems, including the jet stream.
Whether the dramatic sea ice loss of 2023 signals a long-term change is unclear, but there are concerns. “It is too early to state whether 2023 and its record-breaking sea ice decline marks the onset of a fundamental shift in the amount of Antarctic sea ice,” said Dr Josey.
“However, our study does reveal the extreme conditions to be expected in future years of low ice regrowth, with 2024 looking like it is continuing the sharp change seen in 2023.”
Repeated years of low sea ice could compound the observed changes, amplifying their effects on ocean currents, atmospheric circulation and weather patterns.
Dr Josey emphasised the urgency of further research, calling for advanced climate models to better understand the risks over the long term.
“This is vital to determine how the increased number of storms are linked to the extra heat supply into the atmosphere and for assessing societal risks, including potential changes to weather conditions in the decades ahead,” he said.
