West Antarctic Ice Sheet Has Begun to Collapse
The West Antarctic ice sheet has long been considered at risk due to global warming, and today, two studies report, the melting has begun.
The West Antarctic ice sheet has long been considered at risk due to global warming, and today two studies report, based on new evidence, an unstoppable retreat has begun. The ice sheet holds enough water to raise sea level by several feet.
The glacier's slow degradation would have a destabilizing effect on the rest of the ice sheet, which holds enough ice to raise global sea level by 10 to 13 feet, according to researchers.
The "grounding line" between the ice sheet and ocean is retreating inward based on airborne and satellite data, said Eric Rignot, lead author of a study published in Geophysical Research Letters, at a press conference held by NASA.
"Today we present observational evidence that the [ice sheet] has gone into irreversible retreat," Rignot said. "It has reached the point of no return."
The sea-level rise projections from the Intergovernmental Panel on Climate Change will likely need to be revised upward, based on these findings, said Sridhar Anandakrishnan, professor of geosciences at Pennsylvania State University, University Park. Anandakrishnan spoke at the NASA press conference, but was not involved in the study.
"The authors have shown that part of Antarctica is undergoing enormous change," Anandakrishnan said. "That ice has nowhere to go but in the ocean. This results in a rise in sea level around the globe."
Researchers from the University of Washington, using computer modeling, also report that the West Antarctic ice sheet is collapsing.
"Our simulations provide strong evidence that the process of marine ice-sheet destabilization is already under way on Thwaites Glacier, largely in response to high subshelf melt rates," the authors wrote in the study, to be published May 16 in Science. "Similar behavior also may be under way on neighboring Pine Island Glacier."
If there is good news, the scientists say, it's that the collapse could take anywhere from 200-900 years. However, once started, it's unlikely to stop.
"One potential way in which the retreat of these glaciers could be stabilized would be if during its retreat the grounding line -- the boundary between floating and grounded ice -- were to reach a region of the ice-sheet bed where the bed slopes towards the ocean," said glaciologist Jonathan Kingslake of the British Antarctic Survey, who wasn't involved in either study. "The authors show that almost no regions of such stabilizing bedrock exist in this region behind the current grounding line. Hence, they conclude, the retreat is likely to continue unstably for decades to come."
The idea that the glacier's retreat once started could not be stopped has been discussed since the 70s, Anandakrishnan said. "We've crossed a critical threshold. We finally have enough observations to put it all together and say 'We're finally in this state.'"
In this graphic, the red regions are areas where temperatures have increased the most during the last 50 years, particularly in West Antarctica. The dark blue regions have had a lesser degree of warming.
The effects of global warming are frequently projected decades into the future, but two recent reports -- one from the
U.S. Global Change Research Program
and the other
-- put into sharp focus visible consequences of our warming planet. An increase in temperature, extreme weather, loss of ice and rising sea level are just a few of changes we can measure right now. Let's take a look at some of the most concerning trends.
Glaciers are shrinking worldwide and permafrost is thawing in high-latitude and high-elevation areas, reports this year's Fifth Assessment Report from the Intergovernmental Panel on Climate Change.
Only a few extinctions are attributed to climate change, reports the IPCC, but climate change that occurred much more slowly, over millions of years, caused major ecosystem shifts and species extinctions. Land and sea animals are changing their geographic ranges and migratory patterns due to climate change.
Sea level around the world has increased by about 8 inches since 1880, reports the 2014 National Climate Assessment, which projects a 1 to 4 foot rise by the end of the century.
Excess CO2 is dissolving in the ocean and decreasing the pH of seawater. The ocean is about 30 percent more acidic than it was in pre-industrial times. More acidity in the oceans makes it harder for animals to form calcium carbonate shells and skeletons and erodes coral reefs.
The probability of a Sandy-like storm deluging New York, New Jersey and other parts of the East Coast has nearly doubled compared to 1950, according to the American Meteorological Society. Even weaker storms will be more damaging now than they were 10 years ago because of rising sea levels. Superstorm Sandy cost the nation $65 billion, according to the 2014 National Climate Assessment, and 2012's Hurricane Isaac cost $2.3 billion.
The global sea level rises along with the temperature for two major reasons. For one, heat causes water to expand, which causes the existing water to take up more space and encroach on the coast. At the same time, ice at the poles and in glaciers melts and increases the amount of water in the oceans.
Across the United States, heavy downpours are on the rise, especially in the Northeast and Midwest. Increases in extreme precipitation are expected for all U.S. regions, reports the 2014 National Climate Assessment.
The most recent IPCC report states with "very high confidence" that current climate-related extremes like heat waves, droughts, floods, cyclones and wildfires are showing that countries around the world, at all development levels, are significantly unprepared. The American Meteorological Society estimates that approximately 35 percent of the extreme heat in the eastern United States between March and May 2012 resulted from human activities' effects on climate. The AMS warned that deadly heat waves will become four times more likely in the north-central and northeastern United States as the planet continues to warm.