A rare hole has opened in the ozone layer over the Arctic. Scientists say it is the result of unusually low temperatures in the atmosphere over the north pole.
The hole, which has been tracked from space and ground in recent days, has reached record dimensions but is not expected to pose any danger to humans unless it moves further south. If it spreads further south over populated areas, like southern Greenland, people would be at higher risk for sunburn. However, based on current trends, the hole is expected to disappear completely within a few weeks.
Low temperatures in the northern polar regions led to an unusual and stable polar vortex, and the presence of ozone-depleting chemicals such as chlorine and bromine in the atmosphere, due to human activities, caused the hole to form.
"The hole is primarily a geophysical curiosity," said Vincent-Henri Peuch, director of the Copernicus Atmospheric Monitoring Service. “We monitor unusual dynamic conditions, which drive the process of chemical ozone depletion. These dynamics allowed lower temperatures and a more stable vortex than usual over the Arctic, which caused the formation of polar stratospheric clouds and the catalytic destruction of ozone ”.
The hole is unrelated to the Covid-19 shutdowns that have drastically reduced air pollution and greenhouse gas emissions. It is also too early to tell whether the unusually stable conditions of the Arctic polar vortex are linked to the climate crisis or part of normal stratospheric climate variability.
Peuch said there were no direct implications for the climate crisis. Temperatures in the region are already rising, slowing ozone depletion, and the hole will begin to recede as polar air mixes with ozone-rich air from lower latitudes. The last time similar conditions were observed was in the spring of 2011.
The hole was tracked by the Copernicus Atmospheric Monitoring Service of the European Center for Medium-Range Weather Forecasts, based in part in Reading and funded by the European commission.
While a hole over the Arctic is a rare event, the much larger hole in the ozone layer over Antarctica has been a major concern for more than four decades. Production of ozone-depleting chemicals has been drastically reduced, according to the 1987 Montreal Protocol, but some sources appear to continue to work: in 2018, unauthorized emissions were detected from eastern China.
The Antarctic ozone hole was the smallest in 35 years last November, demonstrating the success of efforts to reduce the production of harmful pollutants. The ozone layer protects the earth from harmful levels of ultraviolet radiation from the sun.
New sources of ozone-depleting chemicals were not a factor in the hole seen in the Arctic, Peuch said. “However, this is a reminder that one should not take the Montreal Protocol measures for granted, and that observations from the ground and from satellites are critical to avoiding a situation where chlorine and bromine levels in the stratosphere can rise again ”.