Study Reveals Factors for Antartica’s Regime Shift and Its Impacts

Polar scientists are sounding the alarm about the significant regime shift at the Earth’s south pole. In 2023, the South Pole witnessed a staggering sea ice loss, equivalent to Greenland’s size. In 2022, temperatures in East Antarctica soared to 30-40°C above normal.

Interestingly, the Antarctic has been a less prominent subject of study and research than its northern counterpart, the Arctic. For years, scientists have monitored the Arctic’s diminishing summer sea ice, while the Antarctic has largely been overlooked in the climate change narrative due to its remoteness and early scientific miscalculations.

In 1995, based on the climate models, the IPCC suggested that a warming planet would bring more snow to the south pole and thought the Antarctic’s massive ice storage was safe. However, the models have proven to be inaccurate.

Recent observations at the south pole reveal that Antarctica is undergoing significant changes in the land, sea, and atmosphere above. This is not just a change but a regime shift, a long-term alteration in Antarctic ice occurring at the South Pole.

The study, “Observational Evidence for a Regime Shift in Summer Antarctic Sea Ice,” published in February 2024 in the Journal of Climate, highlights the significant changes observed in the Antarctic, including shifts in ocean-sea ice dynamics and temperature extremes. 2023’s record-low Southern Ocean ice is potentially tied more to long-term warming than previously thought.

A paper by Will Hobbs and colleagues from the Australian Antarctic Program Partnership (AAPP) at the University of Tasmania notes evidence that the extent of Antarctic sea ice may exhibit a “regime shift” that could have far-reaching impacts on the climate. Hobbs explained the regime shift as an abrupt change in a system’s behaviour.

Researchers have shown that there has been a doubling of summer Antarctic sea ice variability throughout satellite observations, consistent with the study of Purich and Doddridge in 2023. They found that the variability of Antarctic sea ice and the length of time the anomalies have lasted has increased significantly since 2006.

Dr Will Hobbs talks about their study

“The extreme lows in Antarctic sea ice have led researchers to suggest that a regime shift is underway in the Southern Ocean, and we found multiple lines of evidence that support such a shift to a new sea-ice state.”

“We explored whether a significant change in sea-ice variability has led to more extreme sea-ice events over the last decade and whether that’s because of a changed response to the atmosphere or the ocean,” Dr Hobbs said.

“We found that the variability of Antarctic sea ice, and how long the anomalies last, has increased significantly since 2006.”

“Perhaps the most striking change for scientists is that while the atmosphere has always been the main driver of Antarctic sea-ice variability, the recent extreme fluctuations over the last decade can’t be explained by the atmosphere alone.”

“AAPP research shows that the changes we’re seeing – how much the sea ice can shift from its average state, and how long those shifts can stick around – are controlled by ocean processes. This is more evidence that ocean changes are probably the secret to what’s happened in recent years,” he said.

A co-author of the study, Dr Phil Reid of the Bureau of Meteorology (an AAPP partner agency), said that scientists are now carefully examining whether the new freeze season—which should start in March—will bring a repeat of last winter’s alarmingly low sea-ice cover.

“To understand and be able to simulate the mechanisms responsible for these unprecedented extreme events, we need a coordinated and sustained observation network that includes real-time monitoring of the upper ocean, immediately under the sea ice.”

“We also need to monitor where and when sea ice isn’t present – particularly around the coastal margins. The presence of sea ice can act as a buffer between ocean swells and ice shelves. Removing this buffer increases coastal exposure, which can destabilise ice shelves, potentially increasing the flow of Antarctic glaciers and adding to sea level rise.”

“This summer has set a new record for the length of Antarctic coastline exposed to damaging swells and surface ocean warming,” said Dr Reid. (Good Things, 2024).

Impacts of the Antarctic’s receding sea ice

As sea ice melts, it exposes darker ocean surfaces with lower albedo than ice. This leads to increased sunlight absorption and subsequent warming, a phenomenon known as the ice-albedo feedback, potentially exacerbating the effects of climate change.

The study notes, “Sea ice is a critical component of the Antarctic ecosystem, and extremely low summer ice cover has significant impacts. A stark example is the reported 2022 catastrophic breeding failure of emperor penguin (Aptenodytes forsteri) colonies due to early sea ice loss. Sea ice loss could also have significant consequences for Southern Ocean biogeochemistry. Changes in sea ice behaviour can affect the synchronicity between ice retreat and the onset of water column biological productivity, which have been well studied locally and at circumpolar scales. Based on our findings, understanding how the physical environment, biogeochemistry, and ecosystems could be affected by such changes in local sea ice is critical, considering that variability in sea ice extent has been shown to affect phytoplankton communities’ diversity near the northern Antarctic Peninsula, with implications for the ocean carbon cycle. The ecosystem impacts of a sustained and repeated loss of Antarctic sea ice are complex and varied, but the impacts of increased variability have not yet been systematically considered.”