A new model that allows scientists to reconstruct Antarctic weather from more than 100 years ago has revealed atmospheric conditions over the southern continent unlike anything seen in modern times.
These conditions may have played a major role in the 1911-12 “race for the pole” between Norwegian Roald Amundsen and British explorer Robert Falcon Scott, in which Amundsen’s expedition reached the South Pole uneventfully on 14 December 1911, while Scott’s perished on the return journey, after reaching the pole about a month later.
To make the finding a team of researchers led by Ryan Fogt, a climate scientist at Ohio University in Athens, Ohio, began by collecting air-pressure measurements at stations in Australia, New Zealand, South America, and South Africa and comparing them to data from modern weather stations in Antarctica.
Based on this, they created their model, which they then used to make Antarctic weather maps all the way back to 1905.
They found that the summer of 2011-12 was extremely unusual, with “really high pressure anomalies” along the routes followed by Amundsen and Scott, says Fogt.
Such conditions, he says, are associated with warm temperatures — warm enough that Amundsen’s expedition would have seen temperatures above minus-16 degrees Celsius as it approached the South Pole, more than 10 degrees higher than average. “That worked well for him,” Fogt says.
Scott, on the other hand, started later. When the warm temperatures hit his party, it was still on the Ross Ice Shelf, thousands of metres lower and hundreds of kilometres north of Amundsen’s party. The result was that for him, the warm temperatures were an impediment, accompanied by a heavy, wet snowstorm.
“It was miserable for them,” says Fogt. “They couldn’t make much progress.”
On his return, Scott ran into another warm snap, this time as he was descending from the Antarctic Plateau via the Beardmore Glacier, on which his party made slow progress. “It might not have been good conditions for sledging,” says Fogt, though he notes that Scott’s party might also have become complacent and started collecting rock samples – “what they called ‘geologising.’”
Then conditions turned cold again, and the party eventually perished, caught in a blizzard only 18 kilometres from a massive supply cache they called the One Ton Depot.
The warm weather, Fogt hypothesises, may have helped set them up for this disaster. Just as autumn temperatures feel colder than spring ones, even when the thermometer is the same, he says, “I suspect the cold conditions felt even colder to them, having had a week of really warm conditions descending the Beardmore Glacier. That might have slowed them down and played a role in the end result.”
But the new research does more than add science to one of the most dramatic stories in Antarctic exploration. The same climate reconstructions also help put in perspective the changes we are seeing in recent times.
Specifically, they show that the past 30 years have seen much lower summer air pressures than occurred in the early and middle years of the twentieth century, Fogt says, in which relatively high air pressures were the norm (even if not quite as high as those producing the weather seen by Amundsen and Scott).
Today’s low-pressure conditions tend to produce wind conditions that keep most of Antarctica’s ice relatively stable, Fogt says. But will they last, or revert, suddenly causing the glaciers to melt more rapidly?
It’s a complex question, depending in part on what happens to the Antarctic ozone hole, which, despite ozone depletion’s negative effects on human health due to increased ultraviolet radiation, may help produce the low-pressure conditions currently helping to keep Antarctica cool. “I don’t think the models can give us a full answer,” Fogt says.
Richard Alley, a geoscientist at Pennsylvania State University, adds that however much the new work may fascinate historians trying to understand the Scott/Amundsen chapter in Antarctic history, they are also “a great advance” in helping scientists unravel the complex interplay between greenhouse gases, the ozone hole, and other climate-change factors influencing the Antarctic ice sheets.
“This…will help us understand what happened to get us where we are, and what may happen in the future depending on decisions we humans may make, with huge implications for future sea-level rise,” he says.
The research is published in the journal Geophysical Research Letters.