The loss of sea ice in the Arctic is popularly attributed to man-made climate change, but findings of a new study have revealed that natural changes in the environment are still a significant factor that contribute to this phenomenon.
Natural Factors
Researchers of the new study found that a considerable chunk of summer ice loss in recent decades can be blamed on natural variability in the atmosphere over the Arctic Ocean.
Qinghua Ding, from the University of California Santa Barbara, and colleagues used model simulations of different climate conditions in a bid to quantify the contributions of nature and humans to the dramatic decline of sea ice in the region.
In 2013, a United Nations panel of climate scientists, which said that ice may disappear by the middle of the century if carbon emissions keep rising, only said that human influence likely contributed to sea ice loss without estimating how much. The new study finally pinned down the relative share of natural and human influences in the loss of ice.
The research, which was published in the journal Nature Climate Change on March 13, suggests that natural changes in the environment are to blame for about 40 percent of Arctic sea ice loss. The rest can be blamed on human activities.
The study builds on an earlier work of Ding and colleagues who found that in recent decades, the tropical Pacific Ocean has created a "hot spot," a large region over Greenland and the Canadian Arctic marked by higher pressure where air tends to pack together so it gets warmer and can hold more moisture. This hot spot can bring more heat and cause melting in the sea ice below.
In an earlier study, NASA scientists have said that the level of sea ice in the Arctic shows no sign of significant recovery. Based on the results showing natural causes as a significant contributor, the Ding and colleagues said that an ice-free Arctic Ocean, which could happen in just a few years, may be delayed if nature swings back to a cooler mode.
"If this natural mode would stop or reverse in the near future, we would see a slow-down of the recent fast melting trend, or even a recovery of sea ice," Ding said.
Man-Made Influences
The findings, however, do not discount the importance of man-made contributions to the melting of the sea ice particular. Researchers said that the buildup of Earth-warming greenhouse gases could become a more overwhelming factor.
In a 2016 study, researchers said that 3 square meters of Arctic summer sea ice is lost for each ton of carbon dioxide produced in the planet. Climate scientists are concerned that since ice cover in the summer has already shrunk by half over the past four decades, there is possibility that the remaining half will also vanish by mid-century.
"Anthropogenic forcing is still dominant -- it's still the key player," Ding said. "But we found that natural variability has helped to accelerate this melting, especially over the past 20 years."
