Human-induced change could affect as much as half of the world’s oceans

18 August 2020 

Human-induced change may have affected as much as half of the Atlantic, Pacific and Indian Oceans, a new study has revealed.

A new article in Nature Climate Change predicted through climate modelling that 20 to 55 per cent of the Atlantic, Pacific and Indian basins would have an “emergent anthropogenic signal” in 2020 and that figure would climb to between 40 and 65 per cent by the middle of this century. 

The current model projects that the percentage will fall between 55 and 80 per cent in 2080. 

Oceanic change as a result of the climate crisis affects both temperature and salinity, which results in “widespread and irreversible impacts”, according to the authors of the study. 

While the most pronounced change is found in the upper ocean, research has indicated that changes in water masses at depth have been identified and “will probably strengthen in the future”, they added. 

The first indications of global ocean heat content change was identified in the early 2000s and studies have continued to investigate trends ever since.

Anthropogenic change remains undetected in “vast regions of the World Ocean”, according to the study, but the authors note that the lack of recorded change could be due to poor observational coverage. 

Further maintenance and augmentation of an ocean observing system capable of detecting and monitoring persistent anthropogenic changes therefore is needed in order to monitor the ocean, the study concluded. 

The effects of a changing ocean 

Oceans currently account for 70 per cent of the earth’s surface and have absorbed approximately 93 per cent of excess planetary warming to date. 

The ocean has also taken in 30 per cent of CO2 emissions, which according to Dr. Ayana Elizabeth Johnson, has led to ocean acidification. 

When CO2 is absorbed by the ocean, it changes into carbonic acid and thus lowers the pH of the ocean, making it more acidic. 

To date, the ocean on the pH scale has become more acidic, moving from a 8.2 to 8.1 classification.

The ocean is notably not yet classified as acidic, as that would require the figure to fall under 7 on the pH scale, but it is more acidic than previously recorded. 

The ocean itself is also heating up due to climate change, and threatens coastal communities with sea level rise, which is attributable to both water expanding when warmed and the additional water produced by melting glaciers. 

Melting ice also poses a risk to salinity, as its freshwater runoff reduces the salinity of the ocean it melts into. 

The degree of salinity and temperature of the ocean affects global currents, which in turn control various elements of weather and climate. 

For example, Ireland’s climate is largely determined by the Gulf Stream, a current that brings warmer water to its shores. 

A changing current would greatly impact Ireland and potentially see a drastic shift away from its current temperate climate. 

About the Author

Kayle Crosson