The 25 Million Sq Km Ozone Hole Over Antarctica Is Record-Low; Thanks To Reduced Chlorine Use

The annually recurring hole in the ozone layer over the Antarctic has reached massive proportions this year and will last well into November. Scientists at NOAA and NASA blame this on the polar vortex, the persistent cold temperatures and strong circumpolar winds.

In a recent report, NASA highlights that the Antarctic ozone hole reached a peak size of about 24.8 million square kilometres back in September this year. At this measurement, the hole was roughly three times the area of the continental United States.

NASA mentions that this is the ¡°12th largest ozone hole by area in 40 years of satellite records,¡± in a recent release. In terms of ozone concentration, the hole resulted in the 14th lowest amount of ozone in 33 years.

(Image: NASA's Goddard Space Flight Center/Scientific Visualization Studio)

While the depletion in the ozone layer is of a considerable proportion, the good news is that it is not as worse as it could have been. Had it not been for the Montreal Protocol preventing the use of ozone-depleting chemicals, these levels of ozone depletion would have been substantially more in comparison.

¡°From the year 2000 peak, Antarctic stratosphere chlorine and bromine levels have fallen about 16% towards the natural level,¡± said Paul A. Newman, chief scientist for Earth Sciences at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "We have a long way to go, but that improvement made a big difference this year. The hole would have been about a million square miles larger if there was still as much chlorine in the stratosphere as there was in 2000.¡±

The annual depletion

The ozone hole over Antarctica forms every year during the Southern Hemisphere¡¯s late winter. At this time, ozone-depleting reactions start taking place due to the returning Sun¡¯s rays as well as the cold winter temperatures, leading to the formation of the ¡°hole¡± in the ozone layer.

These ozone depletion reactions involve chemically active forms of chlorine and bromine, which are derived from man-made compounds. The total chlorine levels in the stratosphere are measured each year by the Microwave Limb Sounder aboard NASA¡¯s Aura satellite.

(Representative Image: Reuters)

In addition, several other instruments are used to detect the presence of ozone in the region. These include satellite instruments like the Ozone Monitoring Instrument on Aura satellite, the Ozone Mapping Profiler Suites on the NASA-NOAA Suomi National Polar-orbiting Partnership satellite as well as the NOAA-20 polar satellite.

Interestingly, ozone measurements taken this year were consistent with record lows. NASA¡¯s Ozone Watch reported the lowest daily value for 2020 to be 94 Dobson Units on October 6 over Antarctica.

Bryan Johnson, a scientist with NOAA¡¯s Global Monitoring Lab, said ¡°It¡¯s about as close to zero as we can measure.¡± He mentioned that the rate of ozone depletion has slowed compared with 20 years ago, which is consistent with there being less chlorine in the atmosphere.