The first recorded summer to melt virtually all floating sea ice in the Arctic could have occurred as early as the 1930s. new scientific study — about a decade earlier than researchers previously predicted.
The revised findings, published on Tuesday, also show that this climate change milestone could materialize even if nations manage to cut greenhouse gas emissions more decisively than they currently do. Earlier projections found that stronger action to slow global warming could be enough to preserve summer ice. The latest research suggests that when it comes to Arctic sea ice, only a steep and sharp reduction in emissions could reverse the effects of the warming already underway.
“We are going to lose the Arctic summer sea ice very quickly, basically regardless of what we do,” said Dirk Notz, a climate scientist at the University of Hamburg in Germany and one of five authors of the new study. “We’ve been waiting too long to do something about climate change to still protect the remaining ice.”
As sea ice has been shrinking in recent decades, communities, ecosystems and economies around the world are dealing with the consequences. However, the effects extend far beyond the region.
Sea ice reflects solar radiation back into space, so the less ice there is, the faster the Arctic warms. This causes the Greenland ice sheet to melt faster, contributing to global sea level rise.
The temperature difference between the North Pole and the equator also affects storm tracks and wind speeds in the mid-latitudes, meaning that a warming Arctic could affect weather events such as extreme precipitation and heat waves in temperate parts of North America, Europe and Asia.
For the past four decades it has already been in the far north it was getting warmer four times faster than the global average, a phenomenon scientists call Arctic Amplification.
“Our result suggests that Arctic intensification will be faster and stronger,” said Seung-Ki Min, a climate scientist at Pohang University of Science and Technology in South Korea and another author of the new paper. “That means the related impacts will also come faster.”
Over the course of each year, the surface water of the Arctic Ocean freezes and melts according to the seasons. The amount of ice increases in winter, peaks around March, then decreases to an annual minimum, usually in September.
September lows have been falling since continuous satellite measurements began in 1979, leading researchers to try to predict when the ocean might experience its first summer when it effectively melts all the floating ice.
That doesn’t mean there will be zero ice on the water – patches of ice are expected to remain in certain corners of the Arctic for some time to come. Instead, the limit scientists use is 1 million square kilometers of ice, or about 386,000 square miles. That’s less than 15 percent of the seasonal minimum of Arctic ice cover in the late 1970s.
Looking at satellite measurements of ice cover and computer models of global climate, scientists predict that sea ice is likely to drop below this level for the first time before 2050. But the exact timing has been hard to predict, in part because computer models generally underestimate the loss of sea ice recorded by satellites .
Authors from latest study, which was published in the journal Nature Communications, explained the problem by first adjusting climate models to better match satellite observations. They then used the modified models to project future changes in sea ice under four possible scenarios for greenhouse gas emissions in the coming decades.
Under three of these scenarios, which represent moderate to large increases in emissions, September ice would first fall below the critical threshold as early as the 2030s, roughly a decade earlier than previously estimated.
But the study also found roughly similar timing in a fourth scenario, in which humanity stops pumping more heat-trapping gases into the atmosphere around 2070, something nations’ policies are not on track to achieve. Earlier research suggested that September could remain abundantly icy in this scenario.
The Arctic Ocean’s first unfrozen September, if and when it arrives, will be an important scientific benchmark, but it won’t be a tipping point, said Mark C. Serreze, director of the National Snow and Ice Data Center at the National Snow and Ice Data Center. University of Colorado Boulder. The Arctic began to transform into a bluer ocean decades ago, triggering massive changes polar bear population, shipping routes, access to natural resources and geopolitics.
“It’s already happening,” said Dr. Serreze, who was not involved in the new research. “And as the Arctic continues to lose its ice, those impacts will grow and grow and grow.”