How Climate Change is Altering Ocean Chemical Makeup
How does climate change affect the oceans, and what is the role of the oceans in our climate ecosystem? Oceans are a global force of nature, and the foundation of the Earth on which we live. These natural forces cover just over 70% of our planet’s surface and make up 95% of the space available to all living creatures. They are a life-support system for Earth and a global commons that provide us with a myriad of resources, from the food we eat to the oxygen we breathe. Oceans also regulate the global climate: they mediate temperature and drive the weather, determining rainfall, droughts, and floods. On top of that, in recent decades they’ve absorbed over a quarter of human-caused CO2 -38,000 billion tonnes of carbon in total- and around 90% of the excess heat produced, making them the largest active carbon reservoir on the planet, where an estimated 83% of the global carbon cycle is circulated through marine waters.
But as the climate responds to decades of increasing carbon emissions, the amount of energy and heat absorbed from the atmosphere and stored starts to build up. If we reach a tipping point, we will likely see more extreme weather events, a change in ocean currents, the rising of sea levels and temperatures as well as the melting of sea ice and ice sheets. All of these would aggravate the negative impacts of ongoing practices which already contribute to deteriorating ocean heath, such as overfishing and illegal fishing, pollution, and habitat degradation.
However, perhaps of greatest concern is that the basic chemistry of the oceans is changing faster than it ever has over the past 65 million years. The continual absorption of CO2 increases acidity levels, and when combined with the warming of our oceans, it causes more coral reefs to die off and become unable to offer a healthy ocean habitat for the species that rely on them for food and protection. Scientists estimate that if the current rates of temperature increase continue, the oceans will become too warm for coral reefs by 2050. But how does this happen anyway? Ocean acidification is a chemical reaction in which the ocean absorbs CO2 from the atmosphere. Once dissolved, the carbon dioxide reacts with seawater, lowering the pH level and making the water more acidic. Because of excess carbon dioxide emissions in our atmosphere, the absorption of the gas has increased drastically in recent decades, making the ocean more and more acidic. This presents a huge threat to marine life: marine species can cope with short-term variations to ocean pH, however with an increasingly acidic ocean many may lose their ability to adapt. For example, ocean acidification reduces the concentration of carbonate in sea water. Marine organisms such as coral, shellfish, and some plankton use carbonate to build their shells; less carbonate in the water makes it harder for them to form their shells and skeletons. Existing shells may also start to dissolve. Because of this, populations of species such as baleen whales and birds that feed on calcifying organisms would decrease. This could also result in fewer predators at the top of the food chain, such as dolphins and seals.
Another way human beings have altered ocean chemistry is by making oceans more stable. In the ocean, when water tends to stratify with warmer, less dense water sitting atop colder, more dense water, it creates what is referred to as “stability”. Basically, the increase of temperature at the surface makes the distinction between different temperatures at different levels of depth more marked, making it easier for the different layers to stay separate and stratify distinctly, composing a stable configuration.
A new study published in the journal “Nature Climate Change” shows that the stratification of the oceans is increasing. In other words, oceans are losing the “up-and-down” movements that usually characterize them. The study has shown that the ocean stability has increased by 5.36% in the upper 6,310 metres (20,700ft) of the oceans over the past 50 to 60 years. This paper also shows that some of the increased stability of the oceans is due to a warmer ocean surface which is in turn caused by greenhouse gas emissions and human-caused global heating.
Now, where is the problem in the fact that oceans are becoming more stable and does a more stable ocean matter for humans? It does, and we will feel the effects. First, when warm waters sit at the ocean surface, they affect weather, particularly typhoons and hurricanes. In fact, warm ocean surface water provides the fuel for these large storms. Furthermore, a warmer ocean, especially at the surface, is less able to absorb carbon dioxide from the atmosphere; consequently, more of the carbon dioxide we emit will remain in the atmosphere, which will lead to even more warming. In addition, a more stable ocean is less efficient at moving nutrients through its waters. This means animals that require the flow of nutrient-rich waters could be at risk.
There is good news though. Nowadays, we know why the climate is changing and we know how the oceans are responding. We can do something about this problem – we not only have the ability to slow down climate change but to possibly eradicate it. We just lack the will and leadership and if 2020 has shown us anything, it has revealed that humans can change and adapt quickly to situations. There is hope that we can navigate the challenges resulting from an ocean with altered chemistry, but we must start immediately.
Written by Beatrice Bos