Rainfall could increase in amount, frequency and intensity over the next 80 years along the coast of Antarctica, a new studypredicts. By 2100, if greenhouse gases continue to be released at a high level, rain might increase by 240% on average across the continent. The increase in precipitation could promote the melting of some large ice sheets on the southern continent. This would consequently contribute to a rise in sea levels around the globe.
Rain can also have dramatic consequences for emperor and Adélie penguin chicks. Since chicks’ feathers aren’t yet waterproof, they can freeze when the wet weather subsequently cools and winds pick up. The breeding season of one of the biggest colonies of Adélie penguin colonies around the Dumont d’Urville research station in southeast Antarctica saw complete failure in the 2013-2014 season due to rainfall.
“We expect not only more frequent rain events but also more intense rain events,” said Etienne Vignon from the French National Center for Scientific Research and Sorbonne University in Paris. Vignon is first author of the new study, published in Geophysical Research Letters, and is currently working in the laboratory of study leader Professor Alexis Berne at the EPF Lausanne in Switzerland.
Most of the precipitation in Antarctica is snow. Rain is uncommon and when it does occur, it is usually found on the coasts of the continent. The new study estimates that rain falls an average of up to four days per year over the coast of eastern Antarctica and an average of more than 50 days over the northwestern Antarctic Peninsula.
But this may be changing. Vignon and his coauthors set out to measure and predict future rain on the continent after researchers noted an uptick in rain events.
The researchers wanted to learn how common rain was in Antarctica, and how it might be affected by climate change. However, traditional climate tracking systems aren’t good at predicting rainfall due to the extreme weather. “It’s still a challenge to measure precipitation in Antarctica,” Vignon said.
Vignon and his co-authors gathered information about rain from several decades of observation reports from 10 research stations spread around the continent. Vignon and his co-authors gathered information about rain from several decades of observation reports from 10 research stations spread around the continent. They matched these reports, based on ground observations, with what they call atmospheric re-analysis—a combination of model simulations and various kinds of observations from sensors like radiosounding, radar and radiometers at ground level or onboard satellites—to attempt to find a type of signature that indicates rain in the harsh continent.
They came up with a climatology of rainfall occurrence over the past 50 years covering all of Antarctica, beyond the areas immediately surrounding the 10 research stations.
Most of the rain happened along the coasts and the Antarctic Peninsula, the area where penguin colonies come ashore for breeding. “On average rain almost never occurs on the high plateau because the temperature is too cold,” Vignon said.
Overall, rainfall increased over the peninsula between 1955 and 1999. Surprisingly, the increasing trend reversed from 2000 to 2015, actually decreasing for a period. Vignon said this likely has to do with large natural variability of the climate in this region.
Forecast calls for rain
But the researchers also wanted to see what would happen in the future. They combined this climatology of past rainfall with seven available future climate scenarios outlined in the CMIP6 by theWorld Climate Research Programme, an international program that helps to coordinate global climate research. The results showed how rainfall might change in the different scenarios through 2100. No matter which scenario they ran, the models showed the same trend.
Increasing rain could have dire consequences for the penguins that nest along the coasts. But it could also impact sea level rise, as rain might enhance the melting and breakup of ice shelves, particularly the Ronne and Ross ice shelves in western Antarctica. “Rainfall can enhance the melting of the snowpack,” Vignon said.
Heiner Kubny, PolarJournal