An article published recently in Nature Geoscience warns that Antarctica’s ice masses have begun to experience a process scientists call “Greenlandification.” The term refers to the unprecedented retreat of Greenland’s outlet glaciers and longer surface melt seasons.
Like Antarctica, Greenland was originally expected to remain more stable despite climate change. However, recent Antarctic research contradicts this claim, showing rapidly increasing surface melt, shrinking sea ice and higher rates of iceberg calving from ice shelves.
Oceanic and atmospheric warming has rendered the Antarctic ice sheet more susceptible to rapid grounding line retreat for its glaciers, according to the comment paper by Ruth Mottram of the Danish Meteorological Institute and colleagues. In other words: Because a glacier’s grounding line marks where the ice no longer rests on a land mass but floats on the open ocean, the line’s retreat inland indicates a melting glacier. Antarctica has also lost much buttressing due to the shrinking ice shelves, a process that Greenland has also witnessed since the 1980s.
Mottram’s team referenced satellite imagery to compare Antarctica and Greenland. Specifically, they used datasets from Gravity Recovery and Climate Experiment (GRACE), a powerful, recently developed satellite system that measures mass change and is operated via two satellites, one trailing the other. Jacqueline Austermann, a researcher at Lamont-Doherty Earth Observatory, which is part of the Columbia Climate School, and professor of Earth and Environmental Sciences, explained that because Earth’s gravity exerts its pull on both satellites, “if one approaches a high mass first, it gets pulled a little towards it, and the satellites measure the distance between [each other].” The inter-satellite distances over time show that both Antarctica and Greenland demonstrate accelerating ice sheet mass loss, Mottram and colleagues wrote.
The increasing resemblance between Antarctica and Greenland is a growing source of concern among researchers. In the past, “there [was] a big difference between Greenland and Antarctica,” stated Jonathan Kingslake, a geochemist at Lamont-Doherty Earth Observatory and associate professor of Earth and Environmental Sciences. In an interview with Glacierhub, he explained that Greenland’s climate has grown much warmer. Meanwhile, Antarctica’s colder weather historically reduced melting rates and allowed for large floating extensions of ice connected to the main continent, known as ice shelves, to extend from its edges. “When you talk about Greenlandification, you talk about the transition of Antarctica from that state… to a place more like Greenland where there is a lot of melting on the surface,” Kingslake said. “And you don’t get these floating ice shelves anymore.”
The paper cautioned that losing ice shelves will likely present massive consequences for Antarctica. Seventy-five percent of the Antarctic coastline has ice shelves, which buttress outlet glaciers and help slow the ice flow from the frozen continent. Without the vital protection that ice shelves provide, outlet glaciers will break apart even faster than before. Greenland’s Sermeq Kujalleq glacier has been impacted by this phenomenon. Its accelerated retreat, beginning around the turn of the century, was one of the major factors behind an increased study of Greenland’s ice sheet changes. Antarctica losing its ice shelves echoes the changes scientists have witnessed in Greenland.
Similar to the way the majority of Greenland’s ice tongues (ice shelves confined to narrow fjords) collapsed and vanished in the early 2000s, Antarctic ice shelves are also disappearing. Mottram’s team notes that Antarctic ice shelves have already had a net loss of 36,700 square kilometers from 1997 to 2021, slightly more than the total area of Maryland; this loss has exceeded what is likely restorable through the natural cycle of seasonal glacier growth and retreat. Large Antarctic outlet glaciers have thus become more exposed and sensitive to retreat, like those in Greenland.
Most Antarctic ice loss is concentrated in the West Antarctic Ice Sheet and in the Antarctic Peninsula. The Amundsen Sea Embayment in Western Antarctica in particular saw a 50% acceleration in ice flow in the Pine Island and Thwaites Glaciers since the 1990s and 2000s, respectively. This is similar to the melting pattern of Greenland’s Sermeq Kujalleq Glacier. While the Eastern Antarctic Ice Sheet was previously thought to be more stable than its western counterpart, it has now also experienced grounding line retreat and ice thinning.
Mottram’s team noted the ice shelves are being weakened by processes occurring above and below the water. Beneath the surface, the warming ocean melts the underside of the ice, producing freshwater. As Kingslake explained, “that freshwater ‘wants’ to float above the salty water, so you tend to get this upward motion… that draws in more warm salty water.” This process then continues the melting cycle.
In addition, ice shelves are eroded above the water by hydrofracturing, a process in which the ice begins to crack due to additional pressure resulting from meltwater lakes forming on the ice surface. They are created by small amounts of melting and add pressure to the ice. That pressure generates cracks or fractures that continue to grow, rendering the icy mass vulnerable to breaking.
Together, the melting from below and the cracking of the upper surface lead to rapid ice deterioration: many of the already-collapsed ice shelves were found to have been unstable due to underside melting, and hydrofracturing from above dealt the final blow.
Despite advances in research, there are still unknowns. In particular, there are gaps in the models scientists use to represent physical phenomena. “There are a lot of things we don’t really know how to model, lots of processes we don’t know how to describe with equations,” acknowledged Kingslake. “You need to choose the right numbers, the right parameters to use, but we don’t have that much data to tune those parameters.” The paper indicates that these deficits can be remedied through more research into the drivers of cryosphere change, which can improve model inputs such as how atmospheric warming and ocean circulation affect ice calving, ice shelf melt, surface ice melt and sea ice decline.
This information is crucial not just for scientists, but also for policymakers and governments. Antarctica’s Greenlandification will lead to higher sea levels, with consequences “felt far beyond the world’s most remote continent,” the authors wrote. Coastal areas are especially vulnerable: as sea level rises, so does the risk of destructive floods and storm surges. More detailed and accurate models can help society prepare for these threats.
For many, Antarctica is a wake-up call. A melting South Pole used to be considered a problem of the future, but the data reveal that the future has arrived much more quickly than expected. With Greenland illustrating Antarctica’s potential fate, Mottram and her coauthors highlighted the continued importance of understanding Antarctica’s role in shaping the environment as the climate changes.
