Pine Island Glacier (PIG)
Pine Island Glacier (PIG) is a significant ice stream located in Western Antarctica, part of the West Antarctic Ice Sheet. Characterized by its rapid movement in channels of ice, PIG has been experiencing a continuous reduction in size since the mid-20th century, with accelerated melting observed since the 1990s. Notably, it has become the fastest-melting glacier globally, with a series of calving events—where chunks of ice break off—resulting in substantial mass loss, including a notable event in 2020. The glacier's base lies below sea level, making it inherently less stable and more vulnerable to climate change impacts, such as warm ocean waters that contribute to its thinning.
PIG is closely studied alongside Thwaites Glacier, another significant ice stream in the region, as both glaciers are crucial to understanding potential contributions to sea level rise. Scientists warn that the collapse of PIG and Thwaites could lead to sea levels rising by up to 9.8 feet (3 meters) over the coming centuries, which would have irreversible consequences. Research on PIG has become more sophisticated with advancements in satellite and radar technology, allowing for better monitoring of this remote and challenging region. The glacier's dynamics and interactions with its environment continue to be a focus for scientists studying the broader implications of global climate change.
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Pine Island Glacier (PIG)
Pine Island Glacier (PIG) is a large glacier in Western Antarctica and part of the West Antarctic Ice Sheet. It is a type of glacier known as an ice stream, meaning the ice moves primarily as channels of ice that move faster than the surrounding ice walls. Its base is below sea level. It has steadily decreased in size since the middle of the twentieth century, with significant acceleration beginning in the 1990s. A series of calving events in the 2010s led a large chunk (about 20 percent) to break off. Another calving event occurred in 2020. Calving occurs when a glacier cracks and loses a sizable portion of its ice. The glacier experiences greater loss than any other glacier on the planet. The West Antarctic Ice Sheet is the largest source of ice to the oceans as it flows into Amundsen Sea.
Background
Glaciers form when snow falls on land and turns to ice. Some of the ice remains frozen until the following winter, when more snow arrives. Various factors, including atmospheric conditions and ocean temperatures, can cause a glacier to take on more or less year each year, causing glaciers to fluctuate in size. Glaciers shrink when more ice melts than forms over the course of a year. As glaciers shrink, sea levels begin to rise. Pine Island Glacier is more susceptible to loss and faces greater difficulty in recovery than other parts of the Antarctic ice sheets. Since the 1990s, scientists have observed thinning, cracking, and calving that has not only caused significant mass loss but is also predicted to affect the rest of the West Antarctic Ice Sheet and cause a consequential rise in sea levels.
Expeditions by British explorer Captain James Cook (1728–1779) came near the area in the 1770s but did not reach Antarctica. The continent was first sighted in 1820 and expeditions commenced into the early twentieth century. Pine Island Bay was discovered in 1947 during the US Navy Antarctic Developments Program, also known as Operation Highjump. The bay and the glacier take their name from the USS Pine Island, which, in addition to its participation in Operation Highjump, conducted seaplane operations during World War II (1939–1945), the Korean War (1950–1953), and the Vietnam War (1955–1975). Researchers have maintained some level of observation over the area since its discovery, but the terrain and climate present challenges in collecting data and mapping the region. As technology has advanced, mapping of the area, including the ice and land below, has steadily improved.
Studying Pine Island Glacier is difficult because of its remote location and weather conditions. For decades, humans could only reach the area by plane on short trips or observe it from the sky. To counter this, scientists have made wide use of satellite and radar technology. During the 1970s, the National Aeronautics and Space Administration (NASA) and the US Geological Survey (USGS) launched the Landsat Program to use satellites to observe the planet from space. The program produced the first multispectral images of the glacier. Study of the area has involved international cooperation, though no country has claimed the glacier’s territory because it is so remote. The European Space Agency (ESA) produced the first images of Pine Island Bay using radar interferometry in the 1990s. As scientists began to amass more data, they gained a stronger understanding of how Pine Island Glacier interacts with its environment.
Overview
Geologists often discuss Pine Island Glacier in relation to the nearby Thwaites Glacier, which has received the nickname the doomsday glacier, and the West Antarctic Ice Sheet (WAIS). The ice sheet rests upon bedrock that is below sea level, meaning it is a marine ice sheet. Marine ice sheets are much less stable than those that rest on land above sea level. PIG’s base is likewise below sea level and slopes downward inward. PIG and Thwaites Glacier together account for about 5 percent of the continental ice sheet’s drainage. When these two glaciers move ice and other sediment from WAIS, the discharge flows into the Amundsen Sea, and it becomes easier for small pieces to break off. Scientists have warned that the collapse of both glaciers could cause sea levels to rise as high as 9.8 feet (3 meters). Such an outcome would likely take several centuries, though some researchers say it could happen by 2100 and more optimistic scientists propose this could take as long as two thousand years. Such damage would be irreversible. Recovery will be difficult because the glacier is thinning from below as global climate change alters wind patterns, pushing warm water under WAIS. It is almost impossible for the glaciers to accumulate more ice than they lose without a dramatic drop in temperatures.
Since the 1970s, scientists have observed that PIG is moving faster. However, they believed that the glacier was amassing sufficient ice to maintain its size because they could not see what was happening below the ice sheet. From 1996 to 2006, the rate of mass loss of PIG and Thwaites Glacier doubled, causing the largest recorded ice loss on the continent. As the ice sheet thins, the glaciers become increasingly unstable and prone to calving events.
To the east, PIG is supported by a large ice shelf, which props it up and keeps it from sliding quickly into the ocean. Continued thinning of this ice shelf is problematic because the glacier has no other areas of support. To the west, the glacier faces the Amundsen Sea. As a marine ice sheet, the land beneath the glacier is below sea level; warm waters have caused reductions of the ice between the glacier and the land. The grounding line is the point between grounded ice and the ocean where the ice becomes afloat. Between 1991 and 2011, scientists believe Pine Island Glacier’s grounding line receded by about 0.62 miles (1 km) annually.
Research suggests that major calving events would naturally occur at Pine Island Glacier every four to six years. However, scientists report observing such events as a near annual occurrence. A major calving event in 2018, for example, was followed by one in February 2020. Both Pine Island Glacier and Thwaites Glacier discharged large icebergs during both events. The increased frequency of calving events prevents the glaciers’ recovery as they lose mass.
Bibliography
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