Antarctica’s Sea Ice Reaches Alarming Low for Third Consecutive Year, Scientists Warn of ‘Regime Shift’
For the third year in a row, Antarctica’s sea ice coverage has dropped below 2 million square kilometers, marking a significant decline that has not been observed since satellite measurements began in 1979. The latest data from the US National Snow and Ice Data Center confirms that the past three years have been the three lowest on record for the amount of sea ice floating around the continent. Scientists are now warning of a “regime shift,” indicating that Antarctica’s sea ice has undergone an abrupt critical transition.
Antarctica’s sea ice reaches its lowest extent during the height of the continent’s summer in February each year. On February 18th, the five-day average of sea ice cover fell to 1.99 million square kilometers, and by February 21st, it had dropped to 1.98 million square kilometers. The record low was set in February 2023 at 1.78 million square kilometers. While it is still uncertain if the current level represents this year’s minimum, scientists are confident that these past three years will remain the lowest on record.
Last year, Antarctica’s sea ice reached its peak extent in September, but it was the lowest on record, surpassing the previous record by approximately 1 million square kilometers. Scientists were astonished by the significant decrease in ice regrowth, which fell well outside of anything previously observed. Although there was a slight recovery in coverage in December as the refreeze progressed, it eventually fell back to the current levels. While there are no reliable measurements of Antarctic sea ice thickness, experts suggest that the regrown ice may be thinner than usual, potentially leading to quicker melting.
Scientists are still investigating the causes behind the decline in sea ice, but they are concerned that global heating may be playing a role, particularly by warming the Southern Ocean surrounding the continent. Sea ice acts as a reflector of solar radiation, so less ice can result in increased ocean warming. Walt Meier, a senior research scientist at the National Snow and Ice Data Center, explains that since most of the ice melts completely each summer, much of it is only 1-2 meters thick, and even thinner near the ice edge. The low maximum extent last September suggests that the ice was likely thinner on average in many areas, but it is challenging to determine its exact impact on the rate of melt and the approaching minimum.
The decline in sea ice has significant implications for Antarctica’s ecosystems, as they are closely tied to the ice. From the formation of phytoplankton that can remove carbon from the atmosphere to the breeding sites of penguins, sea ice plays a crucial role. Ariaan Purich, a climate scientist specializing in Antarctica and the Southern Ocean at Monash University, led research last year suggesting that the continent’s sea ice may have undergone a “regime shift” driven by warming of the subsurface ocean about 100 meters down. Recent research by Will Hobbs and colleagues at the Australian Antarctic Program Partnership and other institutions further supports this claim. Their study, published in the Journal of Climate, examines changes in sea ice extent and formation patterns over two periods: 1979 to 2006 and 2007 to 2022. The researchers found that the amount of sea ice has become much more variable or erratic in the later period, and this change cannot be explained solely by atmospheric changes.
While scientists have identified an abrupt critical transition in Antarctica’s sea ice, they are still uncertain about the exact driver of this change. It could be ocean warming or a change in ocean salinity, but it is also possible that it is a natural shift. The loss of sea ice is just one of several major changes occurring in Antarctica that will have global consequences. The exposure of more of the continent to the ocean is accelerating the loss of ice on land, which contributes to rising global sea levels. Scientists are urging governments to take these Antarctic changes more seriously and are calling for sustained measurements of ocean temperature and salinity beneath the sea ice, improvements in climate models, and more time for research.
In conclusion, Antarctica’s sea ice has reached an alarming low for the third consecutive year, indicating a regime shift and an abrupt critical transition. The decline in sea ice has significant implications for Antarctica’s ecosystems and global sea levels. Scientists are still investigating the causes behind this decline and are concerned about the role of global heating. Urgent action is needed to gather more data and improve climate models to address this pressing issue.