The Ross Ice Shelf is the largest ice shelf in Antarctica. As of 2013, it covers an area of about 500,809 square kilometers (193,363 square miles) and spans roughly 800 kilometers (500 miles) in width, which is similar in size to France. The ice shelf is hundreds of meters thick. The edge of the ice that faces the open sea is more than 600 kilometers (370 miles) long and rises between 15 and 50 meters (50 and 160 feet) above the water. However, about 90% of the ice is below the water's surface.
Most of the Ross Ice Shelf is located in the Ross Dependency, an area claimed by New Zealand. It floats over and covers a large part of the southern Ross Sea and the entire Roosevelt Island, which is in the eastern part of the Ross Sea.
The ice shelf is named after Sir James Clark Ross, who discovered it on January 28, 1841. It was originally called "The Barrier" and sometimes referred to as "The Great Ice Barrier" because it blocked ships from sailing further south. Ross mapped the ice front eastward to 160° W. In 1947, the U.S. Board on Geographic Names officially named it "Ross Shelf Ice" and included the name in the U.S. Antarctic Gazetteer. In January 1953, the name was changed to "Ross Ice Shelf," and this name was published in 1956.
Exploration
On January 5, 1841, the British Admiralty's Ross expedition, using the ships Erebus and Terror, which had specially reinforced wooden hulls, was traveling through pack ice near Antarctica in the Pacific Ocean. Their goal was to locate the South Magnetic Pole. Four days later, the ships reached open water and hoped for an easy path to their destination. However, on January 11, the crew encountered a massive ice barrier.
Sir James Clark Ross, the expedition leader, noted that the ice was so large it seemed impossible to pass, comparing it to trying to sail through the cliffs of Dover. Ross, who had previously discovered the North Magnetic Pole in 1831, spent two years searching for a sea route to the South Pole without success. Later, the ice shelf and surrounding sea were named after him, as were two nearby volcanoes.
The Ross Ice Shelf became a key starting point for future Antarctic explorers. During the Discovery Expedition (1901–1904), Robert Falcon Scott studied the shelf from a base on Ross Island. By measuring icebergs and their buoyancy, Scott estimated the ice sheet was about 274 meters (899 feet) thick. He also determined the ice was floating on water and calculated it had moved 555 meters (1,821 feet) northward over 13.5 months. These findings were shared in a lecture titled "Universitas Antarctica!" in 1911 and later published in the account of Scott's Terra Nova Expedition (1910–1913).
In 1908, Ernest Shackleton's southern party from the Nimrod expedition became the first humans to cross the Ross Ice Shelf during their failed attempt to reach the South Pole. Both Roald Amundsen and Scott later crossed the shelf to reach the Pole in 1911. Amundsen described the ice as having a flat outer edge but chaotic, ridged surfaces inside the bay. He noted a towering ridge on the horizon, which he estimated to be about 150 meters (500 feet) high.
The next day, Shackleton's team stepped onto the ice shelf. They described the connection between sea ice and the shelf as a mysterious and intimidating feature. They wondered if it would be a steep wall of ice or a dangerous crack. Amundsen wrote, "One, two, three, and a little jump, and the Barrier was surmounted!"
Composition and movement
Ice shelves are thick, flat layers of ice that form from glaciers and float on top of the ocean. These shelves help slow down the movement of glaciers, like a brake. They also help reduce melting on the glaciers' surfaces. If ice shelves are removed, glaciers can speed up because meltwater seeps through the ice or because the braking force is gone. This can cause glaciers to release more ice into the ocean than they receive as snow. Scientists have already noticed faster glacier movement in areas where ice shelves have broken apart in the past.
The Ross Ice Shelf is one of many such shelves. It extends from the north into Antarctica and covers about 520,000 square kilometers, which is nearly the size of France. The shelf is about 800 kilometers wide and 970 kilometers long. In some parts, especially the south, the ice can be as thick as 750 meters. The shelf moves outward into the ocean at a rate of 1.5 to 3 meters each day. Other glaciers add more ice to it, and freezing seawater beneath the shelf increases its thickness by 40 to 50 centimeters. Sometimes, cracks cause parts of the shelf to break off. The largest known piece that broke off was about 31,000 square kilometers, slightly larger than Belgium. In March 2000, the largest recorded iceberg, B-15, broke away from the Ross Ice Shelf.
Scientists have studied the Ross Ice Shelf for many years. Research teams have set up camps on or near the shelf, including McMurdo Station, which is built on volcanic rock next to the shelf. In the 1950s and 1960s, scientists from around the world conducted studies on the shelf, exploring glaciers and valleys. From 1967 to 1972, the Scott Polar Research Institute used a technique called radio echo sounding to measure the shelf from the air, covering much more ground than earlier methods. Between 1973 and 1978, more detailed surveys were done.
A major scientific project called the Ross Ice Shelf Project aimed to drill into the shelf to study its composition and its connection to the seafloor. This was the first time scientists drilled through an ice shelf to sample the ocean below. The project included studying the ice and drilling, with drilling beginning in 1976. In 1977, scientists successfully drilled a hole through the ice, allowing them to study the seafloor, ocean tides, and marine life. They also measured the temperature of the ice, finding it was about -2.16°C at the bottom of the shelf.
In 1979, the results of these studies were published in the journal Science. During the 1980s, weather stations were set up to monitor temperatures on the shelf and other parts of Antarctica. The University of Colorado's National Snow and Ice Data Center studied ice shelves and noted in 2002 that the Ross Ice Shelf is a major outlet for glaciers in West Antarctica, which holds enough ice to raise global sea levels by 5 meters. Scientists also stated that iceberg calving on the Ross Ice Shelf is not directly linked to its stability.
Research continues to reveal new information about the Ross Ice Shelf. In 2006, a study suggested the shelf may have collapsed in the past and could collapse again. In 2017, a New Zealand team led by glaciologist Christina Hulbe studied the central part of the shelf, finding evidence of ice re-freezing. This process is common, but the Ross Ice Shelf showed unusual variability. A recent study linked this variability to tidal mixing.
In 2019, the same team explored the grounding line of the Kamb Ice Stream, drilling through 500 meters of ice to reach an ocean cavity 30 meters deep. They used a robot called Icefin to explore the area. In 2021, the team studied an under-ice river beneath the Kamb coast, discovering a narrow channel formed by the river. They also recorded evidence of a tsunami caused by the 2022 Hunga Tonga–Hunga Ha'apai eruption.