Scientists are questioning whether a ‘regime shift’ to a new state of diminished Antarctic sea-ice coverage is underway, due to recent record lows.
If so, it will have impacts across climate, ecological and societal systems, according to new research published in PNAS Nexus.
These impacts include ocean warming, increased iceberg calving, habitat loss and sea-level rise, and effects on fisheries, Antarctic tourism, and even the mental health of the global human population.
Led by Australian Antarctic Program Partnership oceanographer Dr Edward Doddridge, the international team assessed the impacts of extreme summer sea-ice lows, and the challenges to predicting and mitigating change.
“Antarctic sea ice provides climate and ecosystem services of regional and global significance,” Doddridge said. “There are far reaching negative impacts caused by sea-ice loss.
“However, we do not sufficiently understand the baseline system to be able to predict how it will respond to the dramatic changes we are already observing.
“To predict future changes, and to potentially mitigate the negative impacts of climate change on Antarctica, we urgently need to improve our knowledge through new observations and modelling studies.”
While sea-ice loss affects many things, the research team identified three key impacts:
• Reduced summer sea-ice cover exposes more of the ocean to sunlight. This leads to surface water warming that promotes further sea-ice loss. Ocean warming increases melting under glacial ice shelves, which could lead to increased iceberg calving. Warmer water also affects the flow of deep-water currents that help move ocean heat around the globe, influencing the planet’s climate.
• Sea-ice loss exposes the ice shelves that fringe the Antarctic continent to damaging ocean swells and storms. These can weaken the ice shelves, leading to iceberg calving. As ice shelves slow the flow of ice from the interior of the Antarctic continent to the coast, iceberg calving allows this interior ice flow to speed up, contributing to sea-level rise.
• Sea ice provides breeding habitat for penguin and seal species, and a refuge for many marine species from predators. It is also an important nursery habitat and source of food (sea-ice algae) for Antarctic krill – an important prey species for many Southern Ocean inhabitants. Adverse sea-ice conditions that persist over several seasons could see population declines in these sea-ice dependent species.
The research team also identified socio-economic and wellbeing impacts, affecting fisheries, tourism, scientific research, ice-navigation, coastal operations, and the mental health (climate anxiety) of the global population.
For example, shorter sea-ice seasons will reduce the window for over-ice resupplies of Antarctic stations. There could also be increased shipping pressures on the continent, including from alien species incursions, fuel spills and an increase in the number and movement of tourist vessels to and from new locations.
Research co-author and sea-ice system expert, Dr Petra Heil, from the Australian Antarctic Division, said the paper highlighted the need for ongoing, year-round, field-based and satellite measurements of circumpolar sea-ice variables (especially thickness), and sub-surface ocean variables.
This would allow integrated analyses of the Southern Ocean processes contributing to the recent sea-ice deficits.
“As shown in climate simulations, continued greenhouse gas emissions, even at reduced rate, will further accelerate persistent deficits of sea ice, and with it a lack of the critical climate and ecosystem functions it provides,” Heil said.
“To conserve and preserve the physical environment and ecosystems of Antarctica and the Southern Ocean we must prioritize an immediate and sustained transition to net zero greenhouse gas emissions.
“Ultimately our decision for immediate and deep action will provide the maximum future proofing we can have in terms of lifestyle and economic values.”
