By: Lena Wang
Accounting for roughly 71% of Earth's surface, the world’s oceans play a major role in sustaining all life on earth (1). These diverse ecosystems produce over 50% of earthly oxygen, regulate global weather patterns and climate, and provide humans with a source of food, recreation, and economic opportunity (2). Yet this human activity has been the source of devastation for these magnificent bodies of water, bearing consequences of increased greenhouse gas release since the start of the industrialized era.
Into Hot Water
Oceans are able to absorb large amounts of heat from the atmosphere without significant changes in water temperature. This characteristic gives them an integral role in stabilizing Earth’s climate system, managing moisture and climate with global currents. This heat, primarily supplied by the sun, remains in the upper 700 meters of the ocean until it eventually spreads from warmer to cooler latitudes and to deeper depths by currents (3). Yet when greenhouse gas imbalances are added to the picture, heat is trapped in the atmosphere and increased quantities are absorbed by the water. In fact, more than 90 percent of the warming on Earth over the past 50 years has occurred in the ocean (3), and there is a notable upwards trend in ocean heat content as the years go by (figure 1).
Higher ocean temperatures can open a Pandora’s box of other problems. As climate regulators, changes in temperature can result in significant changes in weather patterns, including a higher prevalence of bigger, stronger hurricanes hitting coastal cities (4). The heating of the ocean is also not balanced, nor are the effects experienced by the global population. The resultant natural disasters have a tendency to form in the tropics, where the concentration of developing nations makes them the least prepared to respond and recover from the higher frequency of disasters (4).
Creatures such as fish, seabirds, and marine mammals also rely on specific temperature conditions and now face higher mortality rates, loss of breeding grounds and abnormal migrations in the search for better environmental conditions. Additionally, coral reefs have experienced bleaching as a result of ocean temperature increase (5).
The Ocean on the Come-up
Rising sea levels go hand-in-hand with ocean heating and the greenhouse effect. Primarily, it is caused by a combination of melting glaciers and ice sheets, as well as the thermal expansion of water as it warms (6). Atmospheric warming has particular impacts on glacial and ice meltage; thermal expansion and ice meltage historically had equal contributions to sea level rise, but climate change has accelerated the melting of glaciers and ice sheets. These factors together resulted in a 2020 global mean sea level 3.6 inches above the 1993 average, making it the highest annual average in the satellite record (7).
Furthermore, sea rise presents big problems to humans. As of 2014, nearly 40% of the global population lives along coasts (8). Higher sea levels in conjunction with changing weather patterns mean that destructive storm surges push farther inland than before, which also means more frequent flooding. Tidal flooding, also known as low-level “nuisance flooding”, is estimated to be from 300 to 900 percent more frequent within U.S. coastal communities than it was 50 years ago, and if humans continue without adaptation or mitigative measures, with the rising water will come rising financial costs (9).
Carbon, Chemistry, and Creatures
Carbon dioxide naturally exists in our atmosphere, but a fine balance must be maintained between the natural carbon cycle and human contributions. Under normal conditions, carbon dioxide dissolves into the water and reacts to form carbonic acid, which then dissociates into hydrogen ions and bicarbonate (10). Yet because of excessive human-induced CO2 emissions, there is a surplus of it dissolving into the ocean, decreasing oceanic pH. There has been about a 0.1 drop in pH since the start of the Industrial Revolution, and while that may not seem significant, it certainly is. The pH scale is logarithmic, so it means that the water is about 28 percent more acidic than it was before, with a concerning fact that this change is happening faster than any other time in geologic history (11).
This rapid change in pH poses significant problems to marine organisms. Ocean acidification is already impacting many species, especially creatures like oysters and corals that make hard shells and exoskeletons by combining calcium and carbonate from seawater. As ocean acidification increases, available carbonate ions bond with excess hydrogen, resulting in fewer ions available for calcifying organisms (10). If the pH gets too low, shells and exoskeletons can even begin to dissolve.
So what can we do?
Limit greenhouse gas emissions
Protect and restore marine and coastal ecosystems
Improve human adaptation strategies and infrastructure
Invest in carbon capture technology
Strengthen and invest in scientific research
References
Exploring how climate change relates to oceans [Internet]. World Wildlife Fund. [cited 2021 Nov 24]. Available from: https://www.worldwildlife.org/stories/how-climate-change-relates-to-oceans
US Department of Commerce NO and AA. Why should we care about the ocean? [Internet]. [cited 2021 Nov 24]. Available from: https://oceanservice.noaa.gov/facts/why-care-about-ocean.html
Dahlman L, Lindsey R. Climate Change: Ocean Heat Content [Internet]. Climate.gov. 2020 [cited 2021 Nov 24]. Available from: https://www.climate.gov/news-features/understanding-climate/climate-change-ocean-heat-content
Nations U. Economic Recovery after Natural Disasters [Internet]. United Nations. United Nations; [cited 2021 Nov 24]. Available from: https://www.un.org/en/chronicle/article/economic-recovery-after-natural-disasters
Ocean warming [Internet]. IUCN. 2017 [cited 2021 Nov 24]. Available from: https://www.iucn.org/resources/issues-briefs/ocean-warming
Change NGC. Sea Level | NASA Global Climate Change [Internet]. Climate Change: Vital Signs of the Planet. [cited 2021 Nov 24]. Available from: https://climate.nasa.gov/vital-signs/sea-level
Lindsey R. Climate Change: Global Sea Level [Internet]. Climate.gov. 2020 [cited 2021 Nov 24]. Available from: https://www.climate.gov/news-features/understanding-climate/climate-change-global-sea-level
US Department of Commerce NO and AA. What percentage of the American population lives near the coast? [Internet]. [cited 2021 Nov 24]. Available from: https://oceanservice.noaa.gov/facts/population.html
US Department of Commerce NO and AA. Is sea level rising? [Internet]. [cited 2021 Nov 24]. Available from: https://oceanservice.noaa.gov/facts/sealevel.html
Ocean acidification | National Oceanic and Atmospheric Administration [Internet]. [cited 2021 Nov 24]. Available from: https://www.noaa.gov/education/resource-collections/ocean-coasts/ocean-acidification
Ocean acidification facts and information [Internet]. [cited 2021 Nov 24]. Available from: https://www.nationalgeographic.com/environment/article/critical-issues-ocean-acidification
Ocean acidification | National Oceanic and Atmospheric Administration [Internet]. [cited 2022 Jan 10]. Available from: https://www.noaa.gov/education/resource-collections/ocean-coasts/ocean-acidification. Image 1. Ocean acidification. N/A.
US EPA O. Climate Change Indicators: Ocean Heat [Internet]. 2016 [cited 2022 Jan 10]. Available from: https://www.epa.gov/climate-indicators/climate-change-indicators-ocean-heat. Figure 1. Heat Content in the Top 700 Meters of the World’s Oceans, 1955–2020. N/A.
Plumer B. Rising Seas Could Menace Millions Beyond Shorelines, Study Finds [Internet]. The New York Times. 2020 [cited 2022 Jan 10]. Available from: https://www.nytimes.com/2020/07/30/climate/sea-level-inland-floods.html. Image 1. Bangladesh, above, is particularly at risk, along with Virginia and North Carolina in the United States, and parts of France, Germany, India and China. N/A.
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