Declining Antarctic sea ice generating more ocean heat loss and storms
A new study shows that the ongoing decline in Antarctic sea ice is leading to more heat loss from the ocean to the atmosphere and an increase in storm activity. The research, led by the UK’s National Oceanography Centre (NOC), focuses on the record-low sea ice cover in Antarctica during the winter of 2023. The study, published in Nature, offers a clearer understanding of the impacts of this dramatic loss.
Using data from the atmospheric layer just above the ocean surface, the study found that the amount of heat lost from the ocean to the atmosphere doubled. This heat loss is also linked to a rise in storms across the high-latitude Southern Ocean, with some areas seeing up to seven extra storm days per month.
The study also warns that these changes could affect deep ocean currents. The heat loss is causing surface waters to become denser than before, which could have long-term effects on the ocean’s circulation.
Co-author Dr Andrew Meijers, from the British Antarctic Survey, explains:
“The location of this new denser surface water is relatively far from the sites at the Antarctic shelf where the densest and deepest waters of the global ocean are formed.
“However, this 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. In turn this has the potential for increasing sea ice melt in future years”.
“Further analysis is urgently needed to understand these processes and their complex feedbacks, and determine how the massive decline of winter sea ice in 2023, and again this year, will impact the Southern Ocean circulation. This is key to understanding the climatically critical ocean uptake of atmospheric heat and carbon, and the rate of melt of the Antarctic continent.”
The study suggests that these extreme conditions could continue. With 2024 showing signs of continued low sea ice levels, the researchers warn that this could lead to more storms and further changes in ocean properties, which could disrupt global circulation patterns.
Professor Simon Josey, lead author of the study from NOC, said:
“It is too early to state whether 2023 and it’s record-breaking sea-ice decline marks the onset of a fundamental shift in the amount of Antarctic sea ice. 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.”
Josey says it is crucial to use advanced ocean and climate models to understand the long-term effects of these changes. “Our research highlights the need to keep studying the link between Antarctic sea ice loss, ocean heat loss, and changing weather patterns,” he says. “These changes could affect weather and climate far beyond Antarctica.”
The study also notes that sea ice around Antarctica dropped to its lowest levels in 2023, with some regions losing up to 80% of ice compared to the 1991-2020 winter average. With the Southern Ocean exposed, more heat is lost to the atmosphere, cooling surface waters and increasing their density. This could disrupt the global ocean circulation and change how the ocean absorbs heat and carbon. The study warns that repeated low ice years could make these changes worse, potentially speeding up Antarctic ice sheet melt.
Previous analysis of the long-term impacts of declining Antarctic sea ice by co-author Dr Holly Ayres, formerly at the University of Reading and now at NOC, shows that enhanced ocean heat loss can also affect the climate as far away as the Tropics and the Northern Hemisphere.
The researchers stress the need for more studies to understand the full impact of these changes on the Southern Ocean and global climate. “It’s critical to understand how the increased heat loss and more frequent storms are linked to broader shifts in weather patterns,” adds Professor Josey.
‘Record-low Antarctic sea ice in 2023 increased ocean heat loss and storms‘
by Simon A. Josey, Andrew J. S. Meijers, Adam T. Blaker, Jeremy P. Grist, Jenny Mecking, and Holly C. Ayres is published in Nature, https://doi.org/10.1038/s41586-024-08368-y