Science & Tech

Arctic hit by global warming first

5 min read

Effects on poles will be felt at lower altitudes

Scientists from the eight nations bordering the Arctic recently enlisted representatives of the region’s native peoples to help assess climate change there. What they found put a human face on a debate often involving distant projections and abstract numbers.

Less snow, less sea ice, freezing rain in winter, and the appearance of mosquitoes and robins, creatures so foreign the native residents have no word for them.

The experience of the Arctic peoples is a harbinger of things to come, according to James McCarthy, the Alexander Agassiz Professor of Biological Oceanography.

“It’s the canary in the mine, a glimpse of what’s going to happen at lower latitudes,” McCarthy said.

McCarthy spoke about the impact of climate change on the world’s poles Tuesday (Feb. 6) at the Geological Lecture Hall as part of the Harvard Museum of Natural History’s lecture series marking International Polar Year, which officially begins in March.

McCarthy’s talk came just days after the Intergovernmental Panel on Climate Change (IPCC) released its latest report, concluding that the world is warming and it is a near certainty the warming is caused by human activity.

In his hour-long speech, McCarthy took the audience on a tour of climate change basics, with the added perspective of research too recent to have been included in the IPCC’s report.

One glaring omission in the report, McCarthy said, is that the IPCC’s projections of sea-level rise are based merely on the expansion of existing seawater due to warmer temperatures. Left out because the data was too recent, he said, was additional information that melting glaciers and land-based ice would likely significantly contribute to rising seas. McCarthy cited one study that projected a sea level rise of between a half a meter and 1.4 meters by 2100.

The melting of land-based ice can have a considerable impact on sea levels, McCarthy said, because of the sheer volume still locked up in glaciers on Greenland and Antarctica. An estimated 85 percent of the Earth’s surface fresh water is frozen in Antarctica, McCarthy noted, with an additional 10 percent of the world’s fresh water frozen in Greenland’s glaciers.

McCarthy emphasized that no one is predicting that all of Greenland’s ice will melt, but if it did, it alone would cause global sea levels to rise 21 feet.

Although nobody is predicting a total collapse of Greenland’s glaciers, they’re less sure what exactly will happen there, McCarthy said. It has become apparent in recent years that Greenland is melting much more rapidly than previously thought and the process seems to be accelerating.

The sudden collapse of the Antarctic’s Larsen B ice shelf in 2002 illustrated that the melting of glaciers and other global ice does not occur as one would expect by watching an ice cube at room temperature. More than 3,000 square kilometers – an area larger than the state of Rhode Island – of the Larsen B ice shelf, which scientists believed existed for somewhere between 400 and 12,000 years, broke apart into thousands of icebergs in just 35 days.

Scientists therefore are focusing their attention on the dynamics of global ice melt, trying to understand the forces at work, so they can better predict what to expect in the coming years.

The Arctic appears to be warming faster than the Antarctic, McCarthy said, largely because the Antarctic is the world’s highest continent and the altitude further contributes to its cooling. The Arctic, on the other hand, is largely at sea level and, as sea ice melts, it switches from reflecting the sun’s energy to absorbing it. Ice and snow reflect 85 to 90 percent of the sun’s energy while dark water and land absorb 90 percent. It’s easy to see, McCarthy said, how the change from ice to water creates a feedback loop that further warms the waters, further thins the ice, and leads to further warming.

The warming Arctic has the potential to completely reshape the ecosystem there, McCarthy said. Oceanic algae form the basis of the oceanic ecosystem, feeding fish that are eaten by seals that are eaten by polar bears.

McCarthy presented several images illustrating the plight of polar bears, showing them swimming in ice-free seas and stranded on small rocky islands far from the ice. Polar bears normally feed on seals that come up to breathe at holes in the ice, staking out the holes and pouncing on the seals when they poke their heads up. Without ice, however, the bears, though proficient swimmers, are no match for seals in the water, leaving them increasingly hungry during ice-free months.

McCarthy said he hoped the IPCC report will help persuade elected leaders to enact changes to meet the challenge. By stating more forcefully what many already believed, McCarthy said the report should dampen some of the arguments of global warming doubters.

“Hopefully, the contrarians and doubters will have less wind in their sails after this report,” McCarthy said.