New studies indicate that stronger winds and warming deep ocean water have triggered a sharp decline in Antarctic sea ice since 2016. Previously expanding, the ice reached a record high in 2014 before plummeting to record lows. Researchers link this shift to wind-driven upwelling of circumpolar deep water.
Antarctic sea ice extent has declined sharply since 2016, dropping from a record high in 2014 to several record lows, equivalent to losing an area the size of Greenland. This follows decades of slight expansion, unlike the Arctic's 40 percent decline over four decades. Two recent studies attribute the change, termed a 'regime shift,' primarily to ocean processes rather than atmospheric warming alone. Simon Josey at the National Oceanography Centre in Southampton, UK, noted that the research presents a plausible chain of events where the ocean plays the key role in the 2016 melt. Circumpolar deep water, warm and salty from the tropics, flows around Antarctica below 200 metres but has increasingly reached the surface, as shown by two decades of buoy measurements. A study by Earle Wilson at Stanford University explains that climate-driven southward shifts in storm tracks initially increased precipitation, creating a fresh surface layer that insulated sea ice and enabled 2014 expansion. However, stronger winds then drove surface water and ice outward, causing upwelling of deep warm water, particularly in the Weddell Sea between 2014 and 2016. Computer modeling matched these observed temperature and salinity changes to real-world ice fluctuations. Wilson stated, “Most signs point to a persistent and sustained decline in sea ice... All it would take is a sudden reversal of conditions for that heat to come back up.” A second study by Theo Spira at the Alfred Wegener Institute in Bremerhaven, Germany, highlights how warming expanded deep water volumes, thinning protective winter water layers. Stronger winds in 2015 and 2016 breached this barrier, with layering yet to recover. Spira remarked, “It’s the wind that pushes [sea ice] over into these rapid declines, but it’s the ocean that really keeps it low... There’s definitely evidence that we’re in a new regime.” While sea ice melt does not raise sea levels directly, it may affect krill and penguins, and potentially disrupt global currents like the Atlantic Meridional Overturning Circulation if ice production near key shelves declines. The studies appear in PNAS (DOI: 10.1073/pnas.2530832123) and Nature Climate Change (DOI: 10.1038/s41558-026-02601-4).