Image: Edge of Ross Ice Shelf
Michael Van Woert / NOAA
This view of the seaward edge of Antarctica’s floating Ross Ice Shelf shows a region where the ice is cracking and may produce an iceberg.
updated 7/3/2011 8:19:36 PM ET 2011-07-04T00:19:36

Ice sheets simmering in warmer ocean waters could melt much quicker than realized. New research is suggesting that as oceans heat up they could erode away the ice sheets much faster than warmer air alone, and this interaction needs to be accounted for in climate change models.

"Ocean warming is very important compared to atmospheric warming, because water has a much larger heat capacity than air," study researcher Jianjun Yin of the University of Arizona said in a statement. "If you put an ice cube in a warm room, it will melt in several hours. But if you put an ice cube in a cup of warm water, it will disappear in just minutes."

The researchers studied 19 state-of-the-art climate models and saw that subsurface ocean warming could accelerate ice-sheet melting over the next century, resulting in greater sea level rise that could exceed 3 feet (1 meter). Glaciers in Greenland and Antarctica will melt at different rates, though. [In Photos: Glaciers Before and After]

Different strokes for different coasts
Given a midlevel increase in greenhouse gases, the ocean layer about 650 to 1,650 feet (200 to 500 meters) below the surface would warm, on average, about 1.8 degrees Fahrenheit (1 degree Celsius) by 2100, the researchers found.

The actual warming in different regions could differ significantly, though. They found that temperatures of subsurface oceans along the Greenland coast could increase as much as 3.6 degrees F (2 degrees C) by 2100, but along Antarctica would warm less, only 0.9 degrees F (0.5 degrees C).

"No one has noticed this discrepancy before — that the subsurface oceans surrounding Greenland and Antarctica warm very differently," Yin said. The discrepancy is caused by different currents in the ocean: The Gulf Stream will send warmer waters toward Greenland, while the Antarctic Circumpolar Current blocks some of the warmer waters from reaching Antarctica.

Warmer waters = melting ice
This drastic increase in ocean warming will have a substantial impact on how quickly the polar ice sheets melt, as warmer waters will erode away the ice sheets below the surface. This is on top of increased melting from warmer air in the region. As the glaciers' underwater support structures melt, they lose chunks of ice, which become icebergs.

"This does mean that both Greenland and Antarctica are probably going melt faster than the scientific community previously thought," study researcher Jonathan Overpeck, also of the University of Arizona, said in a statement. "We could have sea level rise by the end of this century of around 1 meter [more than 3 feet] and a good deal more in succeeding centuries."

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Previous estimates had projected sea levels to rise by anywhere between 1.5 and 6.5 feet (0.56 and 2 meters), and in 2011 a study by Eric Rignot, of the University of California at Irvine, and others projected that sea level rise would reach 12.6 inches (32 centimeters) by 2050 alone. Overpeck and Yin's study adds to the evidence that sea level rise by the end of the century will be near the high end of these projects.

The study was published Sunday in the journal Nature Geoscience.

You can follow LiveScience staff writer Jennifer Welsh on Twitter @microbelover. Follow LiveScience for the latest in science news and discoveries on Twitter@livescienceand on Facebook.

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Photos: Flagship species

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  1. Polar bears get most of the attention when it comes to warming and endangered species, but they're not alone. Even clownfish are in danger, according to a report released Monday by the International Union for the Conservation of Nature, the largest association of species experts in the world.

    The 10 "flagship species" listed in the report are shown here. In the case of clownfish, aka the Nemos of the underwater world, their coral reef habitats are under severe threat from warmer waters that can bleach, and then kill, coral. Moreover, acidification of sea waters due to higher carbon dioxide levels prevents coral and some other skeletal-based organisms from forming shells.

    Flagship for: Impacts of coral reef degradation due to warming seas and increasing ocean acidification (Tarik Tinazay / AFP-Getty Images) Back to slideshow navigation
  2. Emperor penguins "are predicted to lose sea ice platforms for breeding and face changes in food availability," the IUCN states. Less sea ice could make it easier for penguins to reach water, but it also means growing chicks still without their waterproof feathers could drown by falling through thinner ice. As for food, less sea ice is projected to reduce krill, the shrimplike invertebrates that penguins rely on.

    Could Emperor penguins adapt by moving to dry land? Two colonies do live on land and have remained stable over 20 years, the IUCN says, so "potentially" that's doable if they find suitable food inland.

    Flagship for: Impacts of rising sea temperatures and melting sea ice (Ty Hurley / IUCN) Back to slideshow navigation
  3. Koalas' reliance on Eucalyptus leaves for food could mean mass malnutrition, the IUCN says, since increasing CO2, while allowing plants to grow faster, "also reduces protein levels and increases tannin levels in plants' leaves. As CO2 levels continue to rise, Koalas and other browsers will need to cope with increasingly nutrient-poor and tannin-rich Eucalyptus leaves."

    Global warming models also predict more wildfires and longer, more severe droughts in places like Australia. Koalas are vulnerable to both. Koalas do not have great potential for adapting, the IUCN says, "as changes are occuring faster than koalas are likely to have experienced in the past."

    Flagship for: Effects of elevated CO2 levels on plants and on the animals that rely on them for food (Greg Wood / AFP-Getty Images) Back to slideshow navigation
  4. Arctic foxes "face habitat loss, competition and predation from red foxes" as higher temperatures warm the tundra, the IUCN says. "The encroachment of red foxes into more northern areas has already been documented."

    Moreover, arctic foxes prey largely on lemmings and voles. "Milder and shorter winters are predicted to cause declines in the regularity of these rodents’ population cycles, as well as decreases in their overall numbers," the IUCN says. Because their habitat area is shrinking, the IUCN says, the number of arctic foxes "that can be supported worldwide is likely to decrease."

    Flagship for: Disruptive effects on the balance among species (Bill Pugliano / Getty Images) Back to slideshow navigation
  5. Ringed seal reproduction is being disrupted by Arctic summer sea ice that is melting earlier each year, the IUCN says. "Both ice and snow must be stable enough in the spring season to successfully complete the six week period of lactation. If the landfast ice breaks up too soon, pups may be separated prematurely from their mothers, resulting in high pup mortality."

    Moreover, insufficient snow early in the breeding season as well as "spring rains or warm spring temperatures can cause the roofs of lairs to prematurely collapse, leaving ringed seals unsheltered and exposed to predators." As for adapting by moving, the IUCN says "their already high-latitude distribution range limits their potential for pole-ward migration."

    Flagship for: Impacts of reduced Arctic summer sea ice (Kit Kovacs, Christian Lydersen / IUCN) Back to slideshow navigation
  6. "Belugas are increasingly at risk from vessel and industrial noise, ship strikes and toxin exposure," the IUCN says. "As Arctic ice cover rapidly declines and the passages across northern landmasses become more navigable, humans will gain easier access to formerly pristine areas that have long served as refuges for Belugas and other marine mammals."

    As for adapting, the IUCN notes belugas' "resilience has already been compromised by the historical reductions in population sizes and ranges."

    Flagship for: Indirect effects of climate worsening existing threats from people (Laura Morse / NOAA / Reuters) Back to slideshow navigation
  7. Staghorn corals are the collective name for some 160 species representing one-fifth of Earth’s reef-building corals, the IUCN says. These corals are very sensitive to higher sea temperatures, which can bleach and then kill coral, as well as to increased ocean acidity from higher CO2 levels.

    "‘Mass’ coral bleaching is a new phenomenon dating back to the 1980s," the IUCN says, "and is now the main cause of coral mortality and reef deterioration globally." A third of all coral species are already listed as threatened on the IUCN Red List.

    "Adaptation (for corals) is very slow and unlikely to be able to keep up with" with the warming trend, the IUCN adds.

    Flagship for: Impacts of rising sea temperatures and increasing ocean acidification (Melanie Stetson Freeman / Christian Science Monitor via Getty Images) Back to slideshow navigation
  8. Leatherback sea turtles lay their eggs on beaches but warming sand can actually alter their gender balance, the IUCN says. Over time, the species could see "an increase in the number of females relative to males," threatening its population stability. "Increases in temperature have also been shown to lead to hatchling abnormalities and developmental and other health problems."

    Beach erosion and changing ocean currents are also obstacles. While leatherbacks have adapted to past climate shifts the current warming trend is "believed to be faster than anything leatherbacks and other marine turtle species have encountered previously," the IUCN says.

    Flagship for: Impacts of warming temperatures, rising sea levels and changing ocean currents (Brian Hutchinson / IUCN) Back to slideshow navigation
  9. Quiver trees, members of the Aloe family, appear to be responding to warming temperatures by shifting their range in southern Africa's Namib Desert to higher latitudes and altitudes.

    This shift shows adaptation is possible if warming does not happen too suddenly. But scientists have found new colonies of Quiver trees are slow to develop, raising the question of whether humans should help out by planting seeds. That question reflects "some of the challenges climate change brings to traditional scientific approaches and conservation practices," the IUCN says.

    Flagship for: Difficulties that all plants and slow-moving species face in keeping up with rapidly accelerating climate change (Wendy Foden / IUCN) Back to slideshow navigation
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