The relatively small glaciers that drape the planet's mountains will play an important role in future sea level rise, according to a new study that estimated glaciers' collective size.
Researchers calculated the ice thickness for 171,000 glaciers worldwide, excluding the Greenland and Antarctic ice sheets, which hold the bulk of Earth's frozen water. Through a combination of direct satellite observations and modeling, they determined the total volume of ice tied up in the glaciers is nearly 41,000 cubic miles (170,000 cubic kilometers), plus or minus 5,000 cubic miles (21,000 cubic km).
If all the glaciers were to melt, global sea levels would rise almost 17 inches (43 centimeters), the scientists found.
The study, published in the Oct. 11 issue of the Journal of Geophysical Research, is an improvement on previous estimates of the global ice volume because it uses a physical approach, said lead study author Matthias Huss, a glaciologist at the University of Fribourg in Switzerland.
The glacier count comes from the recently released Randolph Glacier Inventory and global topography from NASA satellite data.
"To date, the volume of glaciers was only estimated using very simple empirical equations with high uncertainties," Huss told OurAmazingPlanet in an email interview. "Our new method not only provides an estimate of the ice volume, but allows calculating local ice thickness on a fine grid for each of the 200,000 glaciers worldwide," he said. [Image Gallery: Glaciers Before and After]
If all of the ice in Earth's mountain glaciers (excluding the Antarctic and Greenland Ice Sheets) were smushed together, it would form a cube that measures more than 34 miles (55 kilometers) on each side.
Predicting sea level rise
Compared with the potential sea level rise from the Greenland and Antarctic ice sheets, the volume of land-based glaciers is relatively small, Huss said. For example, completely melting the Greenland ice sheet would add 23 feet (7 meters) to the average global sea level, according to a 2007 report by the Intergovernmental Panel on Climate Change (IPCC).
But mountain glaciers are still a concern because they "react very fast to higher temperatures and a considerable retreat is very likely in the next decades," Huss said.
Knowing the thickness and total volume of glaciers worldwide is essential for modeling the response of glaciers to climate change, said Valentina Radic, a glaciologist at the University of British Columbia who was not involved in the study. "This study helps to improve our projections of what will happen to the glaciers in the near future," Radic told OurAmazingPlanet in an email interview.
However, Radic notes that less than 1 percent of glaciers in the world have measured ice thicknesses, so it's hard to validate the study's estimates. (Huss calibrated his method in the European Alps, where scientists surveyed the ice by dragging a radar instrument over the glacier's surface to help determine the ice's thickness.)
"One needs to keep in mind that each glacier is unique – so a model that works well in one region may not be applicable in the other. It is hard to say how correct the estimates are, but the method is much more physically-based than any method so far applied on a global scale," Radic said.
Huss and his colleagues plan to next apply their model to predicting how the thousands of glaciers will react to future global warming.
- Ice in Perspective: Earth's Mountain Glaciers (Infographic)
- 8 Ways Global Warming is Already Changing the World
- Ice World: Gallery of Awe-Inspiring Glaciers
Copyright 2012 OurAmazingPlanet, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
Also on HuffPost:
This astronaut photograph taken on Nov. 27, 2010, provides a view of tidal flats and channels near Sandy Cay, on the western side of Long Island, and along the eastern margin of the Great Bahama Bank, on the islands of Bahamas. The continuously exposed parts of the island are brown, a result of soil formation and vegetation growth. To the north of Sandy Cay, an off-white tidal flat composed of carbonate sediments is visible; light blue-green regions indicate shallow water on the tidal flat.
Egypt's Lake Nasser was photographed in January 2005 from the International Space Station.
Tassili n'Ajjer National Park, part of the Sahara Desert, has a bone-dry climate with scant rainfall, yet it doesn't blend in with Saharan dunes. Instead, the rocky plateau rises above the surrounding sand seas. This image from 2000 was made from multiple observations by the Landsat 7 satellite, using a combination of infrared, near-infrared and visible light to better distinguish among the park's various rock types.
Hydrogen Sulfide and Dust Plumes on Namibia's Coast
Cloudless skies allowed a clear view of dust and hydrogen sulfide plumes along the coast of Namibia in early August 2010. Multiple dust plumes blow off the coast toward the ocean, most or all of them probably arising from stream beds. Unlike the reddish-tan sands comprising the dunes directly south of the Kuiseb River, the stream-channel sediments are lighter in color. Wind frequently pushes dust plumes seaward along the Namibian coast.
The Nile River and its delta look like a brilliant, long-stemmed flower in this astronaut photograph of the southeastern Mediterranean Sea, as seen from the International Space Station on Oct. 28, 2010. The Cairo metropolitan area forms a particularly bright base of the flower.
Islands of Four Mountains
The snow-capped volcanoes composing the Islands of the Four Mountains in Alaska's Aleutian Island chain look suspiciously like alien worlds in this August 2010 image from the ASTER camera aboard NASA's orbiting Terra satellite.
This NASA image shows the aurora australis observed from the International Space Station on May 29, 2010. This aurora image was taken during a geomagnetic storm that was most likely caused by a coronal mass ejection from the sun on May 24.
Astronauts at the International Space Station captured this striking view of the Sarychev volcano on Russia's Kuril Islands in an early stage of eruption on June 12, 2009. Sarychev Peak is one of the most active volcanoes in the Kuril Islands chain.
NASA's Terra satellite was rounding the top of the globe -- making its way from the eastern tip of Siberia and across the Arctic Ocean toward northwest Russia -- when it captured this unique view of a total solar eclipse on Aug. 1, 2008. In the area shown in the image, the sun was obscured for about two minutes. As Earth rotated, the shadow moved southeast across the surface. At the same time, the satellite crossed the Arctic with its path nearly perpendicular to the eclipse.
The Advanced Land Imager on NASA's Earth Observing-1 satellite shows a snowy blanket over Fargo, N.D., on Dec. 12.
Astronauts captured this image highlighting the northern entry to Mount Everest from Tibet on Jan. 6. Climbers travel along the East Rongbuk Glacier, shown on the lower left, to camp at the base of Changtse mountain.
The south end of Eleuthera Island in the Bahamas shimmers in turquoise waters in this 2002 photo from the International Space Station.
A massive sandstorm sweeps over Qatar as it races south toward southeastern Saudi Arabia and the United Arab Emirates on Feb. 15, 2004. A major upper-level, low-pressure system over southwestern Asia led to a series of storms sweeping through the area. The crew of the International Space Station captured this image with a digital camera using a 50-millimeter lens.
Lake Naivasha, Kenya
Flowers grow year round in sun-drenched Kenya, and nowhere are they more plentiful than Lake Naivasha, shown here. In this view from space, bright white squares mix with fields of green, tan and purple along the shores of the lake. Sunlight glints off the long rows of glass greenhouses, turning them silvery blue and white. Fallow fields are tan and pink, while growing plants turn the ground bright green. Roses, lilies and carnations are the most common flowers grown in the greenhouses and fields scattered around the lake.
Cumulonimbus Cloud Over Africa
High above the African continent, tall, dense cumulonimbus clouds, meaning "cloud heap" in Latin, are the result of atmospheric instability. The clouds can form alone, in clusters or along a cold front in a squall line. The high energy of these storms is associated with heavy precipitation, lightning, high wind speeds and tornadoes.
NASA Released New Images of Earth at Night
The new images were taken over 22 days by a satellite imaging system and provide the most detailed look yet at the world's night lights.