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Seasons of Change: Evidence of Arctic Warming Grows

NASA's Earth scientists think ice is hot - a hot topic, that is. Two percent of the world's water, about 7 million trillion gallons, exists as the solid, frozen form, second only to the amount in the oceans. NASA wants to know what's happening to our planet's ice, as even small changes in ice could mean big impacts on the water cycle and ultimately the global climate.

Arctic sea surface temperature anomalies

This animation shows surface temperature anomalies in the Arctic for each year from 1981 through 2002. The orange and red colors represent an increase of 0 to 7 degrees C, while the blue colors represent a decrease of 0 to 7 degrees. The data used to create images 5, 6, and 7 were collected by the AVHRR instruments onboard the NOAA POES satellites. Credit: NASA

Polar ice reflects a great deal of the Sun's energy that falls on it back into space, helping regulate the amount of energy arriving on Earth, which drives weather and all the other atmospheric activities. Even a few percent more acres of open water absorbing energy could tip the scales of Earth's energy balance, adding more energy to the atmosphere, altering short- and long-term weather patterns.

Already, scientists have seen differences in Earth's ice cover over time. But it takes time before they can draw any conclusions about possible causes of change: "The first step in understanding why things happen is observing what is happening," says Dr. Waleed Abdalati, NASA scientist and ice researcher.

For more information, movies, and images see: Recent Warming of Arctic May Affect Worldwide Climate and Disappearing Arctic Ice

Space Advantage

Ice Flow

Ice Flow in the Arctic. Short video on Seasons of Change: Evidence of Arctic Warming Grows. (3.59 MB)Credit: NASA

NASA and partner organizations such as NOAA and the Department of Defense use satellites to make daily observations over the entire globe, creating a thorough record through both time and territory. Satellites also don't face the physical obstacles that humans seeking to place ground-based sensors do. This aids in ice research in particular as "the Arctic is a very inaccessible area," notes Dr. Josefino "Joey" Comiso, author of recent studies of Arctic sea ice.

With the aid of satellites, Comiso found the Arctic lost about 10 percent of its perennial sea ice per decade since 1980. The extent of Arctic sea ice that remains frozen all year reached record lows in 2002 and 2003.

Sea ice thickens and expands during the cold, dark winter months and melts somewhat when the Sun returns in spring and summer. The ice that remains even through the warmest, brightest summer days stays frozen year-to-year, known to scientists as perennial sea ice. It's as if the Arctic grows a "winter coat" like a cat's, then sheds it when the weather's warm - the cat never loses all its fur, and the Arctic has never lost all of its ice. But the smaller-than-ever before sizes observed in the past two years signaled a change and have scientists questioning what has changed. That's where satellite observations come in.

Puzzle Pieces

Arctic Pole

This animation (360KB) shows the annual minimum sea ice extent and concentration for 24 years, from 1979 to 2003. The year 2002 showed lowest level of sea ice on record. Credit: NASA

This year, satellite data revealed another piece of the puzzle to Comiso, as he studied temperatures in the Arctic region. Oceans and the surrounding lands in the Arctic region warmed up as much as two degrees Fahrenheit in the last decade. Scientists know that the warming leads to even more melting, as the two processes become a cycle. Open water absorbs more of the sun's energy than ice does, leading to warmer waters, which results in more melted ice, and thus more open water. Comiso noticed the yearly melting of the ice from spring to fall starts earlier and ends later than it did ten years ago: this "melt season" lengthened by at least a week and a half, on average, per decade since 1980. The seasonal melting expanded as much as 17 days over North America in that period.

For more information, movies, and images see: Recent Warming of Arctic May Affect Worldwide Climate and Disappearing Arctic Ice

New Tools, New Observations

NASA's Ice, Cloud and land Elevation Satellite (ICESat)

ICESat is the first polar-orbiting satellite to directly measure the heights of clouds and aerosols.

Launched late last year, the Ice, Clouds, and land Elevation Satellite (ICESat) began returning its first observations of the topography of Earth's ice sheet this year. ICESat will map the height of ice around the globe, focusing on Antarctica and Greenland, allowing scientists to monitor ice thickness. The satellite will also measure aerosol and cloud properties that affect that thickness, such as the moisture content of clouds and concentrations of various aerosols that influence cloud formation. Clouds, of course, store water as water vapor, the gaseous form of water on Earth, and the third part of the water cycle.

For more information, see Ice, Clouds, and land Elevation Satellite (ICESat).

New Maps

Antarctica, too, has long fascinated NASA and other scientists. NASA teamed with the Canadian Space Agency to map the continent with their RADARSAT satellite, producing the first high-resolution map in 1999, able to pinpoint a research bungalow on an iceberg. Such maps would be extremely time consuming, if not physically impossible, to figure out through human expeditions. Researchers continue to watch shifts in the ice around the South Pole. Over the last few years, several large ice shelves broke off from the mainland. One of these, designated B-15, got caught in the Ross Sea and restricts access to McMurdo Station. Scientists stationed at McMurdo have had trouble readily getting supplies through their normal routes. At the start of October 2003, B-15 split in two but continues to block shipping access in the Ross Sea.

B-15A iceberg split

100-mile long iceberg in the Ross Sea, known as B-15A. This animation shows the iceberg splitting. Credit: NASA.

For more information, movies, and images see: NASA Goddard Space Flight Center

Positive Changes

While some of the latest changes to Earth's ice cover may seem to complicate life, in a few instances, these changes have improved things. In the Antarctic, some changes produce new habitats for microscopic plant life and the larger sea life that feed on it up the food chain.

Adelie Penguins

Adelie Penguins. Click image to see larger picture.
Credit: NOAA Corps Collection

Sometimes, when strong winds blow ice away from the coast or floating pieces of ice get stuck when they run into something, open ocean areas, called polynyas, result. These oasis-like bodies of water surrounded by ice can be as small as one-third the size of Rhode Island (about 400 square miles), or as large as the state of Montana (nearly 150,000 square miles).

The resulting open waters absorb more sunlight than the surrounding ice-covered areas. The combination of sunlight and rich nutrients in the Antarctic waters previously blocked by the ice cover allows phytoplankton to thrive. Tiny shrimp-like animals called krill feed on the microscopic phytoplankton, and penguins, sea birds, and seals in turn eat the krill.

For more information, see Black Tie Only-Antarctic Penguins Thrive in Ocean "Oasis"

Solid Future

Besides all these, ice has its fingers in many other areas of Earth Science research. Take volcanoes: the swirling ash and smoke from Mt. Pinatubo's 1991 eruption allowed scientists to test theories on the winds in the Arctic atmosphere, which are greatly influenced by the chilly temperatures of the pole. Or take ozone: temperatures and polar winds affect the amount of thinning our protective ozone layer experiences each year in the Antarctic.

If scientists can say one thing for certain, it's that more changes still lie ahead. Ice ultimately can't be considered as a separate system; everything from the moon's pull through tides to the Earth's own gravitational pull can impact the balance of ice, water, and water vapor that makes our planet so unique. NASA's Earth Science Enterprise aims to understand the Earth as a whole system. Many of its instruments, including ICESat, provide information about not only ice but also the air, water, land, and life flowing around that ice.

Katie Stofer
NASA Goddard Space Flight Center