For more than 100 years, the wreck of the lost ship Endurance has sat untouched at the bottom of the icy Weddell Sea off the coast of Antarctica.
Famed polar explorer Ernest Shackleton and his crew were the last humans to lay eyes on it before its demise in 1915, watching helplessly as shifting sea ice slowly crushed their ill-fated vessel and sent it sinking 10,000 feet down to the ocean floor.
The team’s ensuing quest for rescue would become one of the most famous survival stories in history. And the Endurance would become one of the world’s most renowned shipwrecks, undiscovered but never forgotten.
Now, nearly 107 years later, the Endurance finally has been found.
An international search mission dubbed “Endurance22” announced on March 9 that it had located the wreck, just a few weeks after launching in February. Thanks to detailed notes recorded by Endurance Captain Frank Worsley in 1915, experts had a general idea of where the ship’s final resting place might be. Underwater drones helped them scout the area and eventually make the discovery.
The wreck of the Endurance, now designated a historic monument under the Antarctic Treaty, is a time capsule of another era — a different stage of human exploration and a different phase in the Earth’s post-industrial climate.
A century ago, the so-called heroic age of Antarctic exploration was nearing its end. Stretching from the late 1800s until about 1922, this period saw some of the first major explorations of an as-yet largely uncharted continent. Norwegian explorer Roald Amundsen was the first to reach the geographic South Pole in 1911. Shackleton wanted to be the first person to cross the Antarctic continent by land, but was thwarted by the loss of the Endurance.
The world was, on average, about a degree Celsius cooler then. Scientists knew about the greenhouse effect, but they weren’t yet widely touting the dangers of melting polar ice caps and sea-level rise. Explorers like Shackleton were interested in Antarctica because it was there — not because they thought its ice might one day disappear.
A century later, Antarctica is yet again the subject of international intrigue. But this time, much of that interest is focused on how the region is changing as the world warms.
The Antarctic ice sheet is currently losing about 200 billion metric tons of ice each year as melting glaciers crumble into the sea. It’s responsible for about half a millimeter of global sea-level rise annually. And the ice loss is speeding up over time.
Some experts worry that severe, sustained warming could eventually drive unstoppable and irreversible changes on the Antarctic ice sheet, causing massive glaciers to collapse and generating catastrophic increases in global sea levels. That kind of future still appears to be a long way away — but scientists are viewing the possibilities with growing urgency.
Yet even in the age of climate change, Antarctica is a land of mysteries.
Its counterpart, the Arctic, is currently warming nearly three times as fast as the rest of the world. Much of the region is responding exactly as expected: Its glaciers are shrinking; its oceans are warming; its sea ice is dwindling away.
Antarctica, on the other hand, isn’t always responding to global climate change in the most obvious ways. While the ice sheet is losing mass as a whole, it’s happening much faster in some areas than in others. Some parts of the continent are rapidly warming, while others seem to be relatively stable. Antarctic sea ice is sometimes expanding and sometimes shrinking.
In short, it’s a vast and complicated place.
Still, scientists have made extraordinary leaps since the days of Shackleton in mapping out the continent and documenting the ways it’s changing. And two conclusions are clear: Climate change is already reshaping the Antarctic, and it will only transform faster as the planet continues to warm.
“What we’re seeing in Antarctica now is it’s changing,” said Helen Fricker, a glaciologist at the University of California, San Diego’s Scripps Institution of Oceanography. “There’s no question there.”
In the century since the Endurance went down, here’s what’s changed.
A patchwork of warming
One of the clearest fingerprints of climate change in Antarctica lies just west of the Endurance’s watery grave.
It’s the Antarctic Peninsula, a narrow arm of land jutting out from the rest of the continent. After the ship sank, Shackleton and his stranded crew drifted northwest on floating sea ice until they eventually scrambled ashore on tiny, uninhabited Elephant Island, less than 200 miles north of the peninsula’s tip.
It’s a different world today. The Antarctic Peninsula became one of the fastest-warming regions on the planet in the latter half of the 20th century. Temperatures on the Antarctic Peninsula rose by nearly 3 degrees Celsius — that’s more than 5 degrees Fahrenheit — between 1950 and 2000 alone.
Since the beginning of the 21st century, the warming has slowed and even reversed itself slightly, according to a July 2016 study published in Nature. That’s likely due to natural shifts in the Antarctic climate over the last 20 years.
But it hasn’t been enough to make up for the intense warming in the previous century. And it shows. The region has suffered severe melting episodes during the summers as it’s warmed, according to Ted Scambos, a glaciologist at the University of Colorado, Boulder.
The melting has led to “massive changes in the ice sheet in the far northern tip of the Antarctica Peninsula,” he said.
The most dramatic episode occurred in 2002. A site known as the Larsen B ice shelf — an enormous ledge of ice jutting out from the peninsula — captured international attention when it suddenly crumbled to pieces and disintegrated into the sea. The entire process took place in a matter of weeks, and scientists believe strong warming and melting in the region were to blame.
The collapse of Larsen B was a major wake-up call for Antarctic scientists, said Fricker, the Scripps glaciologist. It was a sign that warming already is wreaking havoc in some parts of Antarctica — and that the ice sheet can change much faster than expected.
“One hundred years ago, and even 50 years ago, and actually even 20 years ago, we thought that ice shelves in Antarctica changed on really, really long time scales,” she said. “And then 2002, boom! Larsen Ice Shelf collapses, and we’re all like, ‘What just happened?’”
In the years since, the Antarctic Peninsula has continued to suffer from heat waves and strong melting events. In February 2020, during the Antarctic summer, temperatures at the northern tip of the peninsula hit a jaw-dropping 18.3 degrees Celsius, or 65 degrees Fahrenheit — the highest temperature ever recorded on the Antarctic continent.
Hundreds of miles away, the geographic South Pole has become another Antarctic hot spot. Over the last three decades, recent research has found, the area has warmed at a rate nearly three times faster than the global average (Climatewire, June 30, 2020).
A century ago, Shackleton planned to pass through the South Pole on his way across the Antarctic continent. Amundsen had beaten him to it just a few years prior, followed shortly by British explorer Robert Falcon Scott, who died along with his team on the journey back from the pole. Shackleton was thwarted by the sinking of the Endurance, and he never made it back — he died of an illness in transit to Antarctica on his next and last expedition a few years later.
The story at the South Pole since Shackleton’s attempts to reach it is complicated. While the region has warmed rapidly since the 1990s, it was actually cooling for a few decades prior. Scientists believe natural climate shifts helped cause the flip-flop in temperatures, in the same way they likely influenced the shifting trends on the Antarctic Peninsula in recent decades.
Other parts of the Antarctic continent also have experienced a patchwork of warming and cooling.
Air temperatures in West Antarctica have largely warmed since the mid-20th century, although not as much as the Antarctic Peninsula. But much of East Antarctica, the largest and coldest section of the continent, hasn’t warmed much at all — and some sections have even cooled a bit.
Scientists believe that natural climate cycles in the Southern Hemisphere play a major role in these inconsistent patterns. Temperatures in certain parts of the continent can be heavily influenced by natural shifts in winds or ocean temperatures, sometimes originating as far away as the tropics.
Antarctica is much more susceptible to these kinds of natural fluctuations than the Arctic, Scambos noted. The Arctic is almost completely surrounded by large landmasses, such as Canada and Siberia, which keep it relatively isolated from the rest of the world. Antarctica, on the other hand, is surrounded by a vast, open sea that flows directly into the world’s other oceans.
“It is more complicated; it’s more variable,” Scambos said. “The geography is just completely different.”
Still, places like the Antarctic Peninsula are a warning that human-caused climate change is already raising temperatures on some parts of the continent. And as the planet continues to heat up, the influence of global warming is likely to eventually outweigh the up-and-down fluctuations caused by natural climate cycles.
And even in bitterly cold East Antarctica, there are occasional warming events that likely would shock the explorers of the heroic age. Just last week, an unprecedented heat event sent temperatures there soaring 70 degrees above normal.
Scientists haven’t yet investigated the exact influence of global warming on this particular incident — freak events do sometimes happen. But it’s a reminder of what the continent could become, perhaps within another 100 years, if global warming spirals out of control.
The sea ice enigma
The story of the Endurance starts and ends with Antarctic sea ice. As the ship approached the Antarctic coastline, it became squeezed among the thick floes of ice covering the Southern Ocean. Trapped, the vessel drifted helplessly across the Weddell Sea toward the Antarctic Peninsula before it was finally crushed.
A century later, sea ice in the Weddell Sea remains thick and treacherous. It stymied previous attempts to locate the Endurance.
A change in conditions this year may have helped the latest search mission succeed. Antarctic sea ice shrank to its lowest minimum level on record this year, according to the U.S. National Snow and Ice Data Center. It hit its low point shortly before the Endurance was discovered.
“Even though the Weddell had sea ice on it, it was a loose pack — thinner and more spread out,” Scambos said. “Lots of gaps for the ship to maneuver in.”
Like so much of what happens in Antarctica, scientists believe this year’s record low is largely a consequence of natural climate fluctuations.
That doesn’t mean global warming isn’t playing a role. But unlike Arctic sea ice, which has been rapidly declining for decades, Antarctic sea ice hasn’t always behaved in the most obvious ways as the planet has warmed. In fact, it’s exhibited some puzzling trends over the last century.
Most of what scientists know about Antarctic sea ice comes from satellite images. And from the beginning of the satellite record in the 1970s until just a few years ago, Antarctic sea ice on the whole was actually expanding.
Then, starting around 2014, the trend abruptly reversed itself, and the ice began dramatically declining (Climatewire, July 2, 2019). It hit a record low minimum in 2017, rebounded a bit in 2020, and then saw another record-breaker this year.
Scientists have fewer direct observations of Antarctic sea ice trends prior to the 1970s. But according to a study published in January in Nature Climate Change, researchers have been able to reconstruct some of the earlier trends using data on the Antarctic climate in prior decades. They found that the ice was declining up until about 1960 or so, when the pattern began to reverse.
Altogether, the record suggests a seesawing pattern of expanding and declining sea ice cover in the Southern Ocean. It’s not completely clear why.
“I think there is a definitely strong role of natural variability,” said Ryan Fogt, an Antarctic climate expert at Ohio University who has studied Antarctic sea ice trends.
And there’s likely another unexpected influence at play: the recovering Antarctic ozone hole, which has been gradually healing since world leaders agreed to phase out the use of ozone-depleting chemicals in the 1980s.
As it turns out, changes in the Earth’s ozone layer can affect the circulation of air in the atmosphere. As the atmospheric ozone hole has closed, some scientists believe it’s influenced wind patterns around Antarctica in ways that may have affected the movement of sea ice.
At the same time, Fogt added, “I wouldn’t say there’s no role of human-caused climate change in all this.”
And like the uneven warming patterns across Antarctica, the signal of human-caused climate change is likely to strengthen in the future. For now, though, the influence of global warming may be engaged in a kind of tug of war with the influences of other factors.
That makes it difficult to predict exactly what might happen to Antarctic sea ice over the next few decades.
“How those things are going to interplay in the next 30 years, 40 years, is a huge question of active research right now,” Fogt said.
Where ice meets the ocean
In the century since the Endurance sank, the biggest change on the Antarctic continent — and the greatest focus of today’s expeditioners — has been the sheer amount of ice it’s losing.
Antarctica is currently pouring about 200 billion metric tons of ice into the ocean every year, according to a June 2018 study published in Nature. That’s triple the rate at which it was losing ice in the 1990s. And it’s likely to keep accelerating as time goes on.
These losses have immense implications for human societies all over the world. Since 1992, Antarctica has raised global sea levels by around a third of an inch. That’s on top of the additional contributions from the Greenland ice sheet, melting mountain glaciers and the warming of the oceans, which causes seawater to expand.
A fraction of an inch might not sound like much. But even small amounts of sea-level rise can have severe consequences, raising the risk of floods and worsening the effects of storm surge on coastal communities. And as Antarctica crumbles at faster rates, those contributions to sea-level rise also will accelerate.
Like so many other patterns in Antarctica, the melting isn’t happening evenly. The largest losses by far come from West Antarctica.
Scientists have been concerned about the West Antarctic ice sheet for decades now. In 1978, glaciologist John Mercer published a paper in Nature warning that future climate change, driven by greenhouse gas emissions, could destabilize the entire region.
It was one of the first scientific papers to call attention to the issue, according to Fricker, who gave a presentation to the American Geophysical Union in 2019 on the last 100 years of science in Antarctica.
At the time, she said, scientists “knew a little bit, but nobody knew enough to really put it all together. We didn’t even have an accurate map of the ice sheet at that time.”
It was decades later before scientists had enough information from long-term satellite records and other measurements to see how the region was already changing. Today, West Antarctica accounts for about 160 billion metric tons of Antarctic ice loss each year.
And while West Antarctica has warmed over the last century, it isn’t air temperatures that are driving most of the melting. It’s warm ocean waters seeping beneath the ice, melting glaciers from the bottom up.
What’s driving these waters is yet another complicated question. General warming of the oceans might be part of it. But most of the warm water comes from deep currents flowing down from the tropics and bubbling back up in the Southern Ocean.
Some scientists believe that shifting wind patterns around Antarctica are helping drive these warm-water currents up to the edge of the ice, speeding up the melting. As with Antarctica sea ice, these changing wind patterns could be affected by multiple factors, including human-caused climate change (Climatewire, April 10, 2018).
This bottom-up melting is a growing concern for Antarctic scientists. They’re keeping a close eye on the region — especially on some of its largest, fastest-melting glaciers.
Thwaites Glacier, sometimes referred to as the “Doomsday Glacier,” is one of the region’s biggest anxieties.
It’s pouring about 50 billion tons of ice into the ocean each year, and parts of it are becoming less stable over time (Climatewire, Dec. 14, 2021). Thwaites is currently the subject of an international scientific collaboration aimed at better understanding the processes affecting its melting — one of the biggest Antarctic science missions in history.
On the other side of the continent, East Antarctica is comparatively stable — at least for now. But scientists are already seeing signs of increased melting at certain sites along the coast.
It’s an area that deserves more attention, according to Fricker. Eventually, the region will start to change at a faster pace, just as the Antarctic Peninsula and West Antarctica have transformed. And being the largest section of the ice sheet, East Antarctica has enormous potential to affect global sea levels.
“East Antarctica — that’s what I think is the next big thing,” Fricker said. “East Antarctica is this big elephant in the room that we haven’t really started properly tackling. It’s huge.”
Even a century after the heroic age of Antarctic exploration, scientists are still plumbing the continent’s mysteries. In the past, mapping out an uncharted continent was the main priority. Today, as climate change transforms the planet, scientists are mapping out an uncharted future instead.
And while competition was the norm in Shackleton’s day — racing to be first to reach the South Pole or to cross the Antarctic continent — cooperation and collaboration are needed more than ever today.
“We’re not gonna solve this; we’re not gonna figure out Antarctica and how it’s changing without really good coordinated international fieldwork, combined with some really targeted satellite observations, as well,” she said. “There’s room for everyone, but everyone needs to work together.”