September 6, 2019

This summer, unusually warm air temperatures have caused record ice melt in the North Atlantic Ocean island of Greenland. During the month of July alone, the island lost more ice than it normally does in an entire year. In just a five-day period, from July 30 to August 3, the island lost about 90 percent of the surface of its ice sheet (a massive glacier)—an estimated 55 billion tons (50 billion metric tons) of ice. The record ice loss is a result of global warming and climate change.

A Danish meteorological team travels across submerged sea ice in Greenland’s Inglefield Bredning fjord on June 13, 2019. The area is normally covered with ice and snow. Credit: Steffen M. Olsen, Danish Meteorological Institute

At the highest point of the Greenland Ice Sheet, 10,550 feet (3,216 meters) above sea level, temperatures topped freezing (32 °F or 0 °C) for more than 16 hours during July 30 and 31, melting some 12.5 billion tons (11.3 billion metric tons) of ice during that brief period. It was the first time ice had melted at that high point since July 2012, and it was just the third such ice melt there in the last 700 years.

Click to view larger image. Greenland, a self-governing territory of Denmark, stretches from the Arctic to the North Atlantic Ocean. Credit: WORLD BOOK map

The ice sheet that covers Greenland is about the size of Alaska, and it contains enough ice to raise global sea levels by more than 20 feet (6 meters). During an average summer, Greenland will lose some ice from meltwater and from icebergs that calve (break off) into the ocean. But the ice loss typically happens at the sheet’s edges at sea level—not at the highest and coldest points. The amount of ice loss is also normally much less. From 1981 to 2010, the average ice melt from July 30 to August 3 was 15 billion tons (13.6 billion metric tons).

Huge icebergs form where the Jakobshavn Glacier flows into the sea near Ilulissat, Greenland. Credit: © Radius Images, Getty Images

The drastic summer ice melt in Greenland is a continuation of an alarming and worsening trend. In 1972, Landsat satellites (a project then known as the Earth Resources Technology Satellite) began photographing and mapping Greenland’s ice sheet. Landsat, a joint mission of NASA and the United States Geological Survey, uses a series of satellites to produce detailed images of Earth from space.

From 1979 to 2006, satellite images showed a 30 percent rise in the amount of Greenland ice that melts each summer, and the ice loss continues to increase. Greenland’s ice fronts have drastically retreated, rocky peaks have become exposed, and the size and shape of the island’s many fiords have changed significantly. In August 2019, Landsat images showed wet snow and melt ponds at Greenland’s higher elevations, and large parts of the island’s shrinking glaciers appeared brownish grey. The color indicates that the surface has melted, a process that concentrates dust and rock particles and leads to a darker recrystallized ice sheet surface.

Greenland is not the only site of rapidly increasing ice melt. Warmer global temperatures are reducing glaciers and ice fields in the Arctic and Antarctica, as well as in Iceland, the Alps, the Andes, the Himalaya, the Rockies, at Kilimanjaro in Tanzania, and in the Sudirman Range in Indonesia.

July 3, 2013

Weather extremes unprecedented in records kept since 1850 pummeled Earth during the decade of 2001-2010, the World Meteorological Organization (WMO) reported today. The decade was the warmest for both hemispheres and for both land and ocean surface temperatures. The year 2010 was the warmest ever recorded, with an average temperature estimated at 1 Fahrenheit degree (0.54 Celsius degree) above the long-term average during the 1961-1990 base period. More national temperature records were reported broken than in any previous decade.

Extreme heat waves, particularly in Europe in 2003 and in Russia in 2010, caused a record number of deaths. The record high temperatures were accompanied by the rapid melting of Arctic sea ice, Antarctic ice sheets, and Greenland glacier ice. As a result, global mean sea levels rose during the 2001-2010 decade by 1/8 inch (3 millimeters) per year–about double the average rise of 1/16 inch (1.6 millimeters) during the 20th century.

Scientists believe that higher ocean temperatures are generating hurricanes of greater severity. (AP/Wide World)

The authors of the report analyzed trends, both global and regional, and such extreme events as Hurricane Katrina, floods in Pakistan, and droughts in the Amazon, Australia and East Africa. They noted that the decade of 2001-2010 was also the second wettest since 1901 and that 2010 was the wettest year ever recorded. They attribute the unprecedented weather extremes mainly to greenhouse gases generated by human action.

Additional World Book articles:

• Global warming
• Australia 2008 (a Back in Time article)
• Australia 2009 (a Back in Time article)
• Australia 2010 (a Back in Time article)
• Europe 2003 (a Back in Time article)
• Russia 2010 (a Back in Time article)
• Twisted–More Terrible Storms (a special report)

December 28, 2012

The West Antarctic Ice Sheet is warming significantly faster than scientists had estimated, according to a study published in the journal Nature Geoscience. The authors of the study revealed that the average temperature at a research station in the middle of West Antarctica has risen by 4.3 Fahrenheit degrees (2.4 Celsius degrees) since 1958–roughly twice as much as scientists previously believed and three times the overall rate of global warming. Particularly surprising was the discovery that although most of the Antarctic warming took place as expected in the spring (September, October, and November in the Southern Hemisphere), some warming occurred in the summer (December, January, and February). Scientists had thought that temperatures in the Antarctic remained relatively stable during the summer.

This alarming report follows another recent study, which found that melting in West Antarctica has accelerated by about 50 percent since 1992. That study, published in November by 47 climate scientists from 26 labs around the world, also found that Greenland’s ice sheets are melting at a rate five times faster than they were in the 1990’s.

Ice and snow cover 98 percent of Antarctica, the world's coldest region. (© Rod Planck, Photo Researchers)

The West Antarctic Ice Sheet is the part of Antarctica that lies west of the Transantarctic Mountains and is mainly in the Western Hemisphere. Because of the enormous weight of the ice there, the terrain under the ice sheet is an average of 3,300 feet (1,000 meters) below sea level. At the ice sheet’s edge near the Southern Ocean, broad, flat, floating ice shelves fill several of Antarctica’s bays and channels. Those ice shelves, along with the ice in the interior, comprise about 90 percent of the world’s ice. Scientists have calculated that if all of Antarctica’s ice melted, Earth’s oceans would rise nearly 230 feet (70 meters), flooding coastal cities around the world. The November study of ice sheets in both polar regions found that the melting there has caused nearly a ½ inch (11 millimeters) rise in in sea level since 1992, or about 20 percent of the overall rise.

One of the scientists involved in the new study, Andrew J. Monaghan of the Colorado-based National Center for Atmospheric Research, noted “When you see this type of warming, I think it’s alarming.”

Additional World Book articles:

• Exploration (the Exploration of Antarctica)
• Glacier
• Global warming (2009) (a Back in Time article)
• The Great Meltdown (a special report)
• Science in Antarctica (a special report)

July 25, 2012

A rapid warm-up in Greenland in mid-July caused melting at or near the surface over nearly 97 percent of the island’s massive ice sheet, data from three Earth-orbiting satellites have revealed. The speed and scale of the melt was so extraordinary that the scientist who discovered the event questioned the accuracy of the data. Such islandwide melting has not occurred since 1889. However, scientists are unsure whether the July event was a rare though natural occurrence or is related to the rise in global temperatures linked to human activity.

Normally, about 55 percent of Greenland’s surface ice cover melts to some degree by mid-summer. Measurements taken on July 8 showed thawed ice over about 40 percent of Greenland. But four days later, that area had increased dramatically to 97 percent. The melting affected even Summit station, the thickest, coldest point on the ice sheet, which sits about 2 miles (3.2 kilometers) above sea level. “Ice cores from Summit show that melting events of this type occur about once every 150 years on average. With the last one happening in 1889, this event is right on time,” said glaciologist Lora Koenig, a member of the research team analyzing the satellite data. “But if we continue to observe melting events like this in upcoming years, it will be worrisome.”

Melting at or near the surrface of Greenland's ice sheet rapidly expanded from 40 percent on July 8 to nearly 97 percent on July 12. (Credit: Nicolo E. DiGirolamo, SSAI/NASA GSFC, and Jesse Allen, NASA Earth Observatory)

The dramatic melt was first spotted by Son Nghiem of NASA’s Jet Propulsion Laboratory in Pasadena, California, while analyzing data from a satellite launched by the Indian Space Research Organisation (ISRO). Data from NASA’s TERRA and Aqua satellites and a United States Air Force weather satellite confirmed Nghiem’s finding. An unusually strong ridge of warm air that stalled over Greenland on about July 11 may have caused the thaw. This heat dome was one of a number that have dominated weather on Greenland since May.

Additional World Book articles:

• Ice formation
• Intergovernmental Panel on Climate Change
• Global warming 2009 (a Back in Time article)
  
• The Great Meltdown (a Special Report)