In what feels like a flashback to the 1990’s, chlorofluorocarbons (CFCs) are once again in the news. Scientists have found that thinning in the ozone layer over the Antarctic caused in large part by these chemicals has shifted the currents of the ocean. Subtropical intermediate waters in southern oceans have become “younger” with upwellings while circumpolar waters have gotten “older”. These changes follow the occurrence of stronger surface winds caused by a thin ozone layer. The findings were detailed in report published this week in the journal Science by a team led by Darryn W. Waugh from Johns Hopkins University.
CFCs began production in the 1930s and were widely used as refrigerants and in such products as aerosol hairsprays. Shown to cause damage to the ozone, they were phased out by the Montreal Protocol in the 1990s. Waugh and his team used measurements of CFC-12 from the early 1990s to the 2000s in the southern oceans. Knowing that the levels of CFCs increased in the waters in tandem with the atmosphere, Waugh and his colleagues were able to determine how quickly the surface waters mixed by measuring the relative levels of the chemical in the water table. They found that the “age changes” were consistent with the intensification of westerly surface winds. They believe the hole in the Antarctic ozone is primarily to blame for these alterations in ocean ventilation.
“This may sound entirely academic, but believe me, it’s not,” said Waugh. “This matters because the southern oceans play an important role in the uptake of heat and carbon dioxide, so any changes in southern ocean circulation have the potential to change the global climate.”
As the ozone begins to recover over the next 50 years, the adjustments to ocean circulation has the potential to slow or reverse. However, the impact of greenhouse gasses on the movement of the world’s oceans has yet to be factored.
Images via NASA