Global Warming in Antarctica

Antarctica contains 90 percent of the world’s ice and 75 percent of its freshwater. If a rise in the planet’s temperature were to cause this store of ice to melt completely, it would result in the world’s sea levels rising by approximately 60 meters.

Background

Antarctica, located at and around the South Pole, is the world’s fifth-largest continent, with a surface area of 12.4 million square kilometers. Approximately 5,500 kilometers wide at its broadest point, it is surrounded by the southern portions of the Atlantic, Pacific, and Indian Oceans. This immense landmass is covered with an ice sheet larger than the continent itself. At its maximum winter extent during the month of July, the ice sheet measures about 14 million square kilometers and contains 30 million cubic kilometers of ice.

The Antarctic Ice Sheet: Unevenly Divided

Approximately 97.6 percent of Antarctica is covered with ice of an average thickness of about 2,100 meters. Most of the remaining percent of the continent not covered by ice is in the Antarctic Peninsula. The Antarctic ice sheet reaches a thickness of almost 5,000 meters at its highest point. From a geologic standpoint, Antarctica is made up of two structural provinces, East Antarctica and West Antarctica. East Antarctica is a stable shield separated from the much younger Mesozoic and Cenozoic belt of West Antarctica. The contact zone between these two provinces is the Transantarctic Mountains and the depression separating the Ross Sea and the Weddell Sea.

The Transantarctic Mountains divide the ice-covered continent into two ice sheets, the largest masses of ice known on Earth. The East Antarctic ice sheet, which is mostly situated in the Eastern Hemisphere, comprises 90 percent of the Antarctic ice. It is surrounded by the southern Atlantic Ocean, the Indian Ocean, and the Ross Sea. The South Pole is located in the East Antarctic ice sheet. The East Antarctic continental landmass on which it rests is close to sea level. Besides its ice sheets, Antarctica has many glaciers, ice streams, and ice shelves. While the East Antarctic ice sheet is dome-shaped, the West Antarctic ice sheet is more elongated along the mountains in the center of the peninsula.

As its name implies, the West Antarctic ice sheet is located in the Western Hemisphere. The northernmost part of the West Antarctic ice sheet protrudes in a peninsula that ends beyond the Antarctic Circle, south of South America; this peninsula is often considered a third, distinct ice sheet, the Antarctic Peninsula ice sheet. The backbone of the peninsula is composed of high mountains, an extension of the Andes mountain range, reaching about 2,800 meters. The northernmost latitude of the peninsula is 63 degrees and 13 minutes south. The largest part of the West Antarctic ice sheet along the Amundsen Sea flows into the Ross Ice Shelf, a platform of floating ice on which the American research station McMurdo is located.

The peninsula glaciers drain into the Weddell and Bellingshausen seas and the Ronne and Filchner ice shelves. Unlike the East Antarctic ice sheet, the West Antarctic ice sheet sits on a continental platform that in some places is 2,500 meters below sea level. It is therefore more influenced by changes in ocean temperatures than is the East Antarctic ice sheet. The West Antarctic ice sheet experiences warmer temperatures than the East Antarctic ice sheet, both because it has a lower average elevation and because the Antarctic Peninsula extends into lower latitudes. It is therefore more vulnerable to the effects of global warming.

Measuring Temperature Change in Antarctica

Because of its high latitude and high elevation, Antarctica is the coldest continent on Earth. The ice that covers Antarctica results from the transformation of snow into ice. The amount of precipitation that Antarctica experiences is not uniform over the entire continent; the coasts, with lower elevation and higher temperatures, record about six times more annual snow accumulation than does the much higher and colder interior, which receives less than three centimeters of water-equivalent precipitation annually. The lowest temperature ever recorded on Earth (-89.2 degrees Celsius) occurred in 1983 at Vostok, a Russian research station in the middle of the East Antarctic ice sheet, where only 166 millimeters of precipitation is received on average per year. (A lower temperature of -93.2 degrees Celsius was recorded in East Antarctica in 2010, but because it was measured by satellite rather than on the ground, the record is not official; in 2018, scientists reported a satellite measurement of approximately -98 degrees Celsius.)

As Antarctic snow layers are progressively transformed into ice, they preserve evidence of the temperature at the time the snow fell in the form of isotope ratios within the ice. As a result, ice cores may be drilled from the Antarctic ice and examined to obtain a chronology of Antarctic temperatures. Antarctic weather stations, moreover, have been recording temperature and measuring precipitation since the early twentieth century, albeit not in a continuous manner. During and after the International Geophysical Year (1957–58), weather stations were systematically installed at the forty-eight bases created in Antarctica by twelve countries. One of the most challenging tasks that these stations have faced has been the physical maintenance of the devices measuring such a harsh environment. Anemometers, which measure wind speed, are particularly vulnerable to the ferocious katabatic winds that sweep the continent, sublimating the surface ice and damaging the devices that measure them.

Effects of Global Warming in Antarctica

Antarctica plays an important role in assessing climatic changes. Its ice reveals the variation of temperature of the continent over 800,000 years. It is also the perfect laboratory for studying the effects of human activities on Earth’s atmosphere. Considered hostile to humans and unexplored until the beginning of the twentieth century, Antarctica came into the spotlight when the ozone hole above it was discovered and when the world’s longest ice core was retrieved at Vostok. The ozone hole threatens the planet by allowing short-wavelength ultraviolet radiation to penetrate the lower atmosphere.

Scientists are concerned over the potentially calamitous effect of the melting of Antarctic ice. In 2018, the Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE)—an international collaboration of polar scientists—computed that Antarctica had lost 2,720 ± 1,390 billion tons of ice from 1992 to 2017. This would result in a rise in sea level of about 7.6 ± 3.9 millimeters. The loss had increased from the 102 billion metric tons recorded in 1996. From 1996 to 2006, some glaciers in the west began moving more rapidly toward the sea and thus produced more icebergs, as their terminuses have collapsed into the sea. In 2020, measurements reported from an advanced satellite fit with a laser altimeter launched in 2018 by the National Aeronautics and Space Administration (NASA) allowed scientists to conclude that between 2003 and 2019, the continent's ice sheet had lost around 118 gigatons of ice each year. These findings indicated that the loss of ice in both Antarctica and Greenland during that period contributed to a sea level rise of about 14 millimeters.

In addition, temperatures in Antarctica have notably been increasing in the twenty-first century. By 2019, the climate in the Antarctic Peninsula had warmed by 3 degrees Celsius since the 1950s. Moreover, a record high of 18.3 degrees Celsius (64.9 degrees Fahrenheit) was recorded at the tip of the Antarctic Peninsula in February 2020 by an Argentine research base. Also in 2020, additional studies showed that Antarctica's ice shelves had lost significant amounts of mass since the mid-1990s due to warmer ocean temperatures; as the ice shelves hold back interior ice flow toward the ocean, scientists found this information particularly concerning in regard to sea level rise. Research published in the science journal Nature in 2016 predicted more dire consequences if global emissions remained at high levels, causing higher temperatures that would intensify the rate of disintegration of the West Antarctic ice sheets. Sea levels would then rise to dangerous levels, with an estimated rise of five to six feet by the year 2100. Indeed, severe heatwaves in Antarctica in 2022 led to record-breaking surface ice melt, and in 2023 scientists recorded the lowest levels of Antarctic sea ice coverage in history.

In a study published in the journal Current Biology in 2017, Matthew Amesbury and colleagues reported that Antarctica is "greening" as a result of increasingly rapid moss growth, caused by rising temperatures and increased meltwater from glaciers. On the northernmost part of Antarctica's mainland, the researchers discovered that in the past fifty years, the two dominant moss species had been growing more than three times faster than before—an average of three or more millimeters per year, compared to previous average annual growth of one millimeter or less. New research published in 2024 revealed the greening of Antarctica was occurring at an even more accelerated rate than scientists originally thought. Satellite imagery showed that plant cover had expanded more than twelve times since the late twentieth century, and that it had increased by 30 percent between 2016 and 2021 alone. As snow and ice cover decreases and vegetation cover increases, more and more heat is absorbed into the ground, which in turn spurs even faster growth.

Future warming could lead to a major ecosystem shift that would cause Antarctica to resemble the warmer and greener Arctic. By the early twenty-first century, the change in climate and ice loss had begun to affect the various species that live on the continent. This included a decrease in penguin and krill populations.

Measuring Ice Losses

To understand and compute the mass balance of the ice in Antarctica, one must determine when and whether the continent loses or gains mass. Antarctica gains mass when snow falls. The entire continent, which is about 1.5 times the size of the United States, contains only about one hundred weather stations, so it is not easy to estimate with a great degree of certainty how much snow accumulates on it, and the error margin is likely to be high. Melting is rare in Antarctica, because the temperature tends to remain below the freezing point year-round. In 2008, Eric Rignot, a professor at NASA's Jet Propulsion Laboratory at the California Institute of Technology who studied Antarctic ice shelves, estimated that 99 percent of the ice lost in Antarctica forms icebergs. However, the total picture of ice loss is not completely uniform; while Antarctica is losing ice at a greater rate and the area covered by sea ice in the Arctic has steadily decreased, sea ice in Antarctica has slightly increased, particularly along the East Antarctic ice sheet’s coast, a condition to which many climate change skeptics have pointed to support their claims. A report published in May 2016 by a team of physicists and NASA scientists indicated, however, that the Antarctic's very cold winds, consistently colder temperatures, thicker snowpack, and the surrounding terrain of the Antarctic Sea and its powerful, circular current all contribute to the growth of Antarctic sea compared to the decrease in Arctic sea ice.

Knowledge of the processes by which the great ice masses of Antarctica grow and shrink is not yet perfect. Improving that knowledge will be of increasing importance, and understanding the climatological mechanisms at work on the continent will be crucial in assessing the impact of human activity on the health and stability of the Earth.

Key Concepts

• Antarctic Peninsula: a peninsula stretching northward toward South America that contains about 10 percent of the ice of Antarctica
• East Antarctic ice sheet: ice sheet located east of the Transantarctic Mountains that stores over 60 percent of the world’s total freshwater
• glacier: a mass of ice that flows downhill, usually within the confines of a former stream valley
• ice sheet: a mass of ice covering a large area of land
• ice shelf: a platform of freshwater ice floating over the ocean
• mass balance: the difference between the accumulation of snow and the ablation of ice on a given glacial formation
• sea ice: frozen ocean water
• West Antarctic ice sheet: the smallest, but no less significant, ice sheet in Antarctica, located west of the Transantarctic Mountains

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