Because of its remoteness, intense cold and extreme weather events, Antarctica is one of the least explored parts of our planet. As a consequence, it’s also one of the least understood parts of the Earth. Consequently, scientists continue to learn about the geology and geography of this supremely hostile environment. And some recent research clarifies the extraordinary forces at work beneath the Antarctic ice cap.
About twice the size of Australia, Antarctica is the world’s fifth-largest continent, and it is, of course, the location of the South Pole. The continent sits in the Southern Ocean and has a surface area of about 5.4 million square miles.
Temperatures on this most frigid of continents can sink to as low as a bone-chilling ?129 °F. However, average temperatures during the Antarctic winter average a slightly balmier ?30 °F. The warmest summer temperature ever recorded was 59 °F, not quite sunbathing weather.
In fact, the continent has only two seasons – summer and winter. The summer consists of six months of daylight, while the winter is the exact opposite – six months of no light. About 98 percent of Antarctica is covered in ice. On average, this ice is a staggering 1.2 miles thick.
That amount of ice is by volume about 90 percent of all the fresh water on our planet. If it all melted, that would raise the level of the world’s oceans by some 230 feet. In the eastern part of Antarctica, the ice sheet sits atop a land mass, but in the west the ice extends into the ocean by as much as 8,200 feet.
Antarctica is so remote that although there was speculation about the existence of a southern land mass, it was 1820 before the continent was actually discovered. A Russian expedition led by Fabian Gottlieb von Bellingshausen and Mikhail Lazarev was the first to sight Antarctica. But it wasn’t until 1895 that a party of Norwegians actually landed on the icy continent.
It was in 1907 that the British explorer Ernest Shackleton led a team that penetrated the interior of Antarctica, becoming the first explorers to reach the magnetic South Pole. In December 1911, the Norwegian Roald Amundsen and his men were the first to reach the geographical South Pole.
Amundsen’s great rival, the British explorer Sir Robert Scott, reached the South Pole in January 19o8, pipped to the post by the Norwegian by just a month. Arguably though, Scott’s expedition came to be the more famous because of the ultimate fate of its members.
Returning to base camp after their trip to the South Pole, Scott and his team missed a rendezvous where they would have been resupplied. Captain Oates made his famous departure from the expedition tent to certain death, hoping that this might leave enough supplies for the others. But the three remaining men, including Scott, all died.
Today, some tens of thousands of tourists visit Antarctica during the summer months, and a few thousand scientists spend tours of duty on the continent each year. But Antarctica is still a place that can be fraught with danger, even for well-equipped scientific expeditions and bases.
One of the most sophisticated of the Antarctic scientific bases, the British Halley VI, well illustrates the dangers of this isolated continent. Halley VI is designed to be moved, comprising independent, linked units mounted on sleds. In 2015 the station was indeed moved some 14 miles because of the perceived threat presented by a large crack that had appeared on the ice sheet where it was located.
But despite this move, the station had to remain unstaffed for the winter months for two seasons after that. So scientific exploration of the Antarctic remains a highly risky and difficult pursuit. But one team of scientists from NASA has come up with fascinating new information by using a clever combination of existing knowledge and data from other parts of the world, including Hawaii and Yellowstone National Park.
The NASA scientists have been studying an area called Marie Byrd Land, which is in west Antarctica. Their interest was in exploring the possibility that underneath this territory lies a massively hot geothermal phenomenon known as a mantle plume, causing volcanic activity. Such a plume exists beneath Yellowstone National Park and is the source of the intense geothermal activity there.
In fact, it was theorized as long as 30 years ago that there might be a mantle plume beneath Marie Byrd Land causing volcanic activity. But scientist Hélène Seroussi said on the NASA website that when she first heard about the theory, “I thought it was crazy. I didn’t see how we could have that amount of heat and still have ice on top of it.”
Seroussi and her NASA Jet Propulsion Laboratory colleague Eric Ivins knew that there were few actual measurements of what was happening under the ice. So they opted to use a modeling technique for their study. They refined and developed an existing tool called the Ice Sheet System Model for the purposes of their study.
As a reality check, the scientists compared their results with actual measurements of ice melt made by a NASA satellite and an airborne operation. Their findings indicated that the heat generated by the mantle plume must be about 150 milliwatts per square meter. For comparison, the Earth’s crust generates about 40 to 60 milliwatts in places with no volcanic activity. Yellowstone Park averages 200 milliwatts.
The diagram here shows the complex pattern of rivers and lakes that run beneath the ice at Marie Byrd Land. Lakes are denoted by blue dots, while the lines represent rivers. The scientists now believe that much of this activity under the ice is caused by the heat emanating from the mantle plume.
This plume is a result of a rupture in the Earth’s crust that allows molten magma to flow beneath the ice. This type of rift is similar to that which lies below the Great Rift Valley in Africa and is also present under Yellowstone and Hawaii.
The rift beneath Marie Byrd Land appeared some time between 50 million and 110 million years ago. This was time when the Antarctica land mass was not covered in ice. Now the ice sheet that is there is greatly affected by the thermal activity beneath. Crucially, the very stability of the ice sheet depends on the amount of liquid water at its base.
We know that the Antarctic lost much of its ice sheet 11,000 years ago as the last ice age ended. Increasing temperatures then caused substantial sea level rises. The question now is, what will global warming combined with thermal activity do to the ice sheet? Don’t forget that figure of a 230-foot sea level rise if all of the Antarctic’s ice were to melt. Only time will tell how much we need to worry.