A latest study spearheaded by the University of East Anglia (UEA) focuses on the link between the healing of the ozone hole and carbon sequestration in the Southern Ocean, noting that while former ozone loss diminished the ocean's capacity to serve as a carbon sink, such effects can be reversed if greenhouse gas emissions are regulated. The research, published in Science Advances, evaluates the impact of the ozone layer and greenhouse gases on the ability of the Southern Ocean to absorb carbon dioxide.

The Southern Ocean plays a critical role in global climate regulation because it takes up proportionately more carbon than its proportion of size. Its wind-forced circulation allows it to extract a lot of carbon from the atmosphere. Atmospheric composition changes, specifically through ozone loss and enhanced greenhouse emissions, influence the dynamics of the circulation and the ocean's ability to store carbon.

The scientists, at the UEA and the National Center for Atmospheric Science (NCAS), analyzed patterns of ocean circulation and carbon uptake from 1950 to 2100 with the UK Earth System Model (UKESM1). The scientists conducted three simulation experiment sets: one in which there was never an ozone hole, one with current conditions that involve the 1987 Montréal Protocol credited with ozone recovery, and one in which the ozone hole is held at 1987 levels.

These runs were then coupled with two emission scenarios of greenhouse gases, a low emissions and a steady high emissions scenario. This enabled the scientists to isolate the effect of ozone depletion and GHG emissions on ocean dynamics and carbon sequestration for 150 years.

The study found that in the late 20th century, ozone depletion amplified Southern Ocean winds. Stronger winds disrupted the natural carbon sink process of carrying carbon-rich deep water to the upper ocean, rendering the ocean less efficient in sequestering atmospheric carbon. This positive feedback lessened the Southern Ocean's buffering effect against climate change.

However, the research showed that with the healing of the ozone hole, partially as a result of global controls, their detrimental impact on winds and oceanic carbon sequestration is set to decrease. On the contrary, the impact of greenhouse gas emissions will grow stronger, and high-emission cases are likely to offset the benefits of ozone recovery.

The models indicated that in the next few decades the carbon distribution in the ocean will be progressively less sensitive to changes in circulation. This is due to the fact that carbon gradient between the surface and deep ocean will diminish as carbon builds up in surface layers for long periods. Thus, wind-driven changes in ocean circulation will influence carbon absorption less than during times when ozone depletion was greatest.

One of the key discoveries made by the study is the conditional reversibility of damage to the ozone layer. The Southern Ocean may recover some but not all of its ability as a carbon sink, but this is critically dependent on the course of greenhouse gas emissions in the future. With a low-emission scenario, the reversal becomes more robust and powerful. Under continuing high emissions, though, the pressure that ocean systems will be subjected to by increasingly intense greenhouse gas-fueled winds will likely counter any benefit accruing from ozone layer healing.

The findings carry implications for world climate policy. Although global success regarding ozone depletion serves as a model to be emulated in cooperative action, the research indicates that without a similar exercise of restraint on greenhouse gas emissions, even such success might prove insufficient to stem erosion of current carbon sink capacity in the world's oceans.

Because the Southern Ocean plays such a critical role in terms of global warming absorptive activity and global warming absorption, this research marks the necessity to halt greenhouse gas emission as a method of safeguarding its global warming absorptive activity. Beyond the fact that long-term success of natural sinks relies on historical environmental harm, it also relies upon prospective policy and emission patterns.

Employing real-case, high-resolution modeling simulations and examining multiple climate variables, the research provides an integrated perspective of stratospheric ozone and anthropogenic emissions interaction to affect oceanic carbon processes. The results indicate that the declining importance of conventional carbon-climate feedbacks with shifting patterns of oceanic carbon under a changing climate.

It was written by Dr. Tereza Jarníková and co-authors of the Tyndall Centre for Climate Change Research, UEA, and makes a compelling argument for cutting global emissions to capitalize on the good news of progress in repairing the ozone layer.

Source/Credits:
Original Study: Science Advances
Research by: University of East Anglia (UEA) and National Center for Atmospheric Science (NCAS)
Published by: University of East Anglia