What is the main cause of the observed acidification of the ocean?

The main cause of the observed acidification of the ocean is the absorption of excess carbon dioxide (CO2) from the atmosphere into seawater. Ocean acidification refers to the decrease in the pH of the ocean, making it more acidic. Since the beginning of the industrial revolution, human activities, primarily the burning of fossil fuels, have significantly increased the concentration of CO2 in the atmosphere. The ocean absorbs a substantial portion of this excess atmospheric CO2. When CO2 dissolves in seawater, it reacts with water to form carbonic acid (H2CO3). Carbonic acid then dissociates into bicarbonate ions (HCO3-) and hydrogen ions (H+). The increase in hydrogen ion concentration lowers the pH of the ocean, making it more acidic. This process reduces the availability of carbonate ions (CO32-), which are essential for marine organisms, such as shellfish and corals, to build their shells and skeletons. Ocean acidification poses a serious threat to marine ecosystems and the services they provide, such as food security and coastal protection. The absorption of CO2 by the ocean is a natural process that helps regulate the Earth's climate, but the rate at which the ocean is absorbing CO2 is now much faster than it has been in the past, leading to significant changes in ocean chemistry and pH.