Ozone holes affect ocean patterns

Hopkins scientists found that the thinning of ozone in our atmosphere has been responsible for changes in the ocean circulation, bringing “old” water to the surface of the ocean. This has had a significant impact on the amount of carbon dioxide in the air.

It is commonly known that human activities have significantly increased the amount of carbon dioxide in the air. However, the greenhouse gas effect has been alleviated by the dissolving of carbon dioxide in ocean water, which effectively reduces its atmospheric concentration. However, scientists discovered that the rate of this phenomenon is slowly decreasing due to the damages in our atmosphere.

A recent study shed light on how the destruction of the Antarctic ozone has had a dramatic impact on the circulation of water in the South Pacific.

The implications of sea circulations is vast. For one thing, it can significantly influence the rate at which carbon dioxide is absorbed from the atmosphere. Therefore, studying the circulation of ocean water, and thus the consequent absorption of gases, is essential to understanding the climate.

The waters in the southern oceans are responsible for 40 percent of the uptake of carbon dioxide from the atmosphere. However, due to the changes in sea movements within this region, the rate at which carbon dioxide is being absorbed is rapidly changing.

Darry Waugh, a earth scientist at Hopkins, and his team explained in their research published in Science that the subtropical waters appear to be becoming “younger” and upwelling, while circumpolar waters are becoming “older.” In other words, surface water near the pole is being sent to intermediate depths faster than it used to be. Simultaneously, waters around Antarctica are pushing the older and deeper water up to the surface.

This could be a problem since the deeper water, which can be up to hundreds of years old, already contains more carbon dioxide than surface water. As a result, the amount of carbon being absorbed is reduced, forcing carbon dioxide to remain in the atmosphere as a greenhouse gas.

Waugh’s team has been measuring the levels of a chemical compound called chlorofluorocarbon-12 (CFC-12) in the southern oceans between the early 1900s and the late 2000s. CFC-12 was produced commercially during the 1930s, and high levels existed in the atmosphere until the 1990s, when the Montreal Protocol was implemented to regulate the amount of ozone-depleting compounds released into the air.

The concentration of CFC-12 at the surface of the ocean is correlated with its concentration in the atmosphere. Therefore, high concentration in deeper waters suggests that those waters were recently at the ocean surface. They found that the CFC-12 concentrations in deep water were higher than they anticipated in subtropical water, due to an increased amount of surface water during the past years. The opposite was true for Antarctic water due to an increase in upwelling.

Those results are further supported by the observation of intense westerly winds that have been recorded by scientists. Such winds are caused mainly by the Antarctic ozone hole, implying that the changes in ocean ventilation, the movement of ocean waters from the surface into the ocean depths, are strongly correlated with the stratospheric ozone depletion.

The thinning of the ozone layer has thus affected the depth of the ocean by altering the movement of the ocean surface into deep water, which impacts the ocean’s uptake of heat, oxygen and carbon from the atmosphere. Scientists hope that if the stratospheric ozone is able to recover over the next 50 years, the ocean ventilation could slow or even reverse.

Although it is well known that fluorine and bromine compounds continue to widen the ozone hole, other factors must be studied. As we study the impact of the continuous increase in greenhouse gases in the atmosphere and other human actions that affect the climate, it is important to remember that the seemingly serene waters of the ocean are actually directly involved in the environmental changes that we are concerned about today.