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Although the world's oceans may appear virtually limitless, the rapid and unprecedented rise in atmospheric CO2 levels since the Industrial Revolution are pushing these vast bodies of water to their physiological limits. The burning of fossil fuels, deforestation, and other human-activities that contribute to climate change dramatically alter Earth's oceans, and these changes will continue to intensify. Oceans cover two-thirds of the world's surface area and support the greatest diversity of life on Earth. Coastal and island tribal communities rely on oceans and marine wildlife for subsistence and ceremonies, yet these tribes are also at the highest risk for storm surges, sea level rise, and erosion, and are often on the forefront of battling climate change.

Warming oceans
According to the Intergovernmental Panel on Climate Change (IPCC), the same forces that contribute to surface temperature increases are likewise warming the oceans. Over the past 100 years, the average global sea surface temperature has increased by approximately 0.13° C per decade.1 This change represents an average across the entire ocean, so both regional and temporal variations exist. For example, the IPCC has concluded that the Atlantic Ocean accounts for the most significant change, as warmer ocean temperatures lead to more intense tropical storms and hurricanes. Oceanic temperature extremes are increasing as well, such as marine heat waves (MHWs). MWHs are drastic increases in the ocean’s temperature that are relatively short-lived and are highly localized.2 MHWs can negatively impact marine wildlife, and in turn, marine birds that consume fish and other sea creatures. MHWs are a relatively new phenomenon and the causes and impacts they carry are still being understood.

One major and alarming consequence of ocean warming is clear. Coral reefs are dying all over the world, in a process known as "coral bleaching." Corals are tiny animals that live in immense colonies and harvest nutrients from a particular type of algae that inhabits their cells. Together, coral and algae create limestone reefs that provide habitat and food for a vast array of life; they make up one of the most productive ecosystems on Earth. The symbiotic relationship between coral and algae, however, is highly sensitive to temperature fluctuations. If temperatures rise above the coral's physiological thresholds, the algae die, leaving the coral without color or its source of nutrients. Corals can recover from short-term bleaching, but extended bleaching ultimately leads to mortality. In 2021, when the warmest ocean temperatures on record were measured, the oceans also experienced a massive coral die-off.3 Dead coral reefs will take decades or even centuries to recover, if they can recover. Dying coral communities are accompanied by losses in marine biodiversity, shoreline protection, fisheries, and medicinal products. Native cultures and peoples in Hawai`i are threatened by the loss of coral reefs, as they rely on the reef for their traditions and food systems, and the health of coral reefs reflects the overall health of the surrounding ocean.4

Coastal dead zones
In addition to the fisheries lost as an impact of coral bleaching, fisheries are disappearing in other regions due to an increase in ocean "dead zones," another phenomenon linked to climate change. Earth is experiencing more intense winds, which cause an upwelling in nutrient-rich waters from the deep sea. When this nutrient-rich water reaches the sunlight, ocean plants known as phytoplankton bloom in great numbers. These tiny plants exist at the bottom of the food chain and provide food for small fish and shellfish. Yet when more phytoplankton bloom than fish can consume, they die and drift to the ocean floor, where bacteria decompose them. The process of decomposition causes hypoxia, or oxygen depletion in the water.5 Fish and shellfish that cannot escape hypoxic water suffocate from lack of oxygen and die. While ocean dead zones have been documented since at least the mid-nineteenth century, studies suggest their frequency and duration are increasing, and new regions are experiencing the phenomena. The largest dead zones are off the Gulf of California and the coast of Peru, areas once renowned for their fisheries.6 Former fishers in these regions are now struggling to keep their businesses running and have had to turn to other work, some of whom have been upholding traditional fishing methods for millennia.

Ocean acidification
In addition to raising ocean water temperatures, global warming is also causing the rapid and unprecedented acidification of Earth's oceans. Between 30 and 50 percent of the carbon emitted from the burning of fossil fuels and other anthropogenic activities over the last 200 years now resides in our oceans.7 This massive carbon influx has not occurred without consequences. When carbon dioxide is taken up by seawater, carbonic acid is formed. Some of this carbonic acid is neutralized by other components of seawater; however, the overall effect is acidification. Since the Industrial Revolution in the eighteenth century, the pH of surface seawater has decreased 0.1 units, equivalent to a 30 percent increase in hydrogen ions.8 This change represents a considerable acidification of the oceans and decreases seawater's subsequent ability to absorb more carbon in the future. Ocean acidification will adversely affect the process of calcification, the process by which animals such as corals and mollusks form plates and shells from calcium carbonate. Because such creatures are near the bottom of the food chain, their survival is fundamental to the overall health of Earth's oceans. This will also disrupt a primary human food source, leading to famine and potential malnutrition in certain parts of the world.9

Marine wildlife in the Pacific Northwest is already being impacted by ocean acidification, and Tribes who rely on this wildlife for subsistence and cultural purposes are subsequently being affected. The Swinomish Tribe in Washington rely on clams, oysters, and salmon for their food systems, which are all species that are negatively impacted by ocean acidification. As Olympia oyster populations decline due to ocean acidification, overcrowding, and competition from Pacific oysters, the Swinomish have relocated some Olympia oysters to beaches with less competition, and where ocean pH can be better monitored.10 The Swinomish are also constructing modern clam gardens, which replicate clam harvesting practices their ancestors utilized for millennia. These clam gardens have the potential to stabilize clam populations for the Swinomish to harvest, even as wild populations decline. They are hopeful that results from the clam garden can be replicated for nearby salmon populations.

The world's oceans are its most important storehouses of CO2, sequestering an estimated total of 38,000 gigatons (one billion metric tons) of the greenhouse gas.11 This natural capacity is truly extraordinary, especially given that the atmosphere and landmass combined sequester approximately 300 gigatons. Geoengineers are examining the potential of the oceans to sequester additional CO2 from the atmosphere, which may provide a solution to warming global temperatures, but carries the potential to increase the acidity of the ocean. Geoengineering is highly controversial as it may have unintended consequences that are ultimately more detrimental than beneficial. Ocean-based carbon-removal strategies include fertilizing the ocean to boost the growth of photosynthetic organisms that sequester CO2; changing the chemistry of seawater to absorb more greenhouse gases; and sending electrical currents through the water to break apart molecules and increase the ability of CO2 sequestration.12 The impacts of this on ocean life and the overall chemistry of the ocean are currently unknown. Other geoengineering approaches to the ocean have been proposed and countless others are being researched.

While geoengineering could aid in achieving net zero carbon emissions, there are natural solutions which could achieve the same result, such as any projects that mitigate and sequester carbon. For more information on one such example, see ITEP’s Forests Basic Information Page. These natural solutions should be held with the same value and consideration as geoengineering.

Sea level rise
One of the most widely known and well-documented consequences of a shifting climate is sealevel rise — an impact already apparent in many Alaskan coastal villages. Sea-level rise is the result of thermal expansion (water expands as it warms) and the loss of land-based ice, including glaciers and permafrost, as temperatures rise. The global mean sea level has risen between 8 and 9 inches since the beginning of the Industrial Revolution.13 This rate is not uniform across all regions; in fact, sea levels are projected to decline in some regions. For example, the U.S. Environmental Protection Agency (USEPA) reports that Atlantic Coastal water rose five to six inches above the global average.14 Alaska, too, is experiencing dramatic land loss. Higher seas erode shorelines; cause saltwater encroachment into inland water sources, including aquifers and creeks; and result in more frequent flooding. The IPCC suggests that rising sea levels could convert roughly one third of Earth's wetlands to open water-destroying a key ecosystem for many plant and animal species, along with nutrient uptake and water filtration capacity.15 Scientists suggest that storm surges will become more severe as the climate changes. This impact will be exacerbated by the eroded shorelines.

Changes in the world's oceans will have serious and likely devastating effects on low-lying coastal communities around the world. The plight of Native Alaskans of the tiny communities of Newtok and Kivalina has garnered worldwide attention. Yet the residents of Newtok, Kivalina, and other Alaskan Native villages are certainly not the only people at risk of the effects of climate change. The Florida coasts are renowned for their extensive, gently sloping beaches that create wide expanses of white sand. Yet models predict that sea levels could rise 8 to 30 inches in the region, which would result in a shoreline loss of hundreds of feet. This encroachment would extend beyond the beach and have severe effects for the region's tourism and agricultural industries.

Further, saltwater encroachment into low-lying areas would likely seep into underground aquifers and contaminate water used for municipal, commercial, and agricultural uses. Both the Hollywood and Big Cypress reservations of the Seminole Tribe, as well as Miccosukee Tribal lands, are located in the Everglades region, where land elevation averages about one foot above sea level. This region is likely to be affected by rising seas and is at great risk for severe flooding, both from the rise itself and from intense storm surges. Sea level and weather changes, as well as saltwater encroachment, also threaten the plants and animals on which these tribes rely for their traditional lifestyles.

Earth's hydrologic cycle creates a close bond between the sea and freshwater sources. Changes in the ocean will impact the availability of potable water for tribal communities throughout the United States. Oceanic impacts will not be confined to coastal areas, though communities along our coasts will be the first to experience the impacts of these changes. Tribes who rely on marine mammals, fish, and shellfish for subsistence, and who are most at-risk for severe storm surges, erosion, and sea-level rise, will be forced to confront some of the most immediate, severe, and abrupt impacts of Earth's changing climate.

  1. National Oceanic and Atmospheric Administration. November 2022. "Global Time Series." National Oceanic and Atmospheric Administration. Available online at [accessed 29 November 2022].
  2. National Oceanic and Atmospheric Administration. October 2019. "So What Are Marine Heat Waves?" National Oceanic and Atmospheric Administration. Available online at [accessed 6 April 2023].
  3. Ramirez, R. January 11, 2022. "Oceans were the warmest on record in 2021, for the 3rd year in a row." CNN. Available online at [accessed 29 November 2022].
  4. USGS Communications and Publishing. March 2015. "Climate Change, Coastal Tribes and Indigenous Communities." USGS. Available online at [accessed 6 April 2023].
  5. National Oceanic and Atmospheric Administration. January 2023. "What Is a Dead Zone?" National Oceanic and Atmospheric Administration. Available online at [accessed 6 April 2023].
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  7. GDRC. "Oceans and the carbon cycle". GDRC. Available online at [accessed 29 November 2022].
  8. National Oceanic and Atmospheric Administration. November 2022. "Ocean Acidification." National Oceanic and Atmospheric Administration. Available online at,fallen%20by%200.1%20pH%20units [accessed 29 November 2022].
  9. Falkenberg, L., Bellerby, R., Connell, S., Fleming, L., Maycock, B., Russell, B., Sullivan, F., & Dupont, S. 2020. "Ocean Acidification and Human Health" International Journal of Environmental Research and Public Health 17, no. 12: 4563. Available online at [accessed 29 November 2022].
  10. Jones, N. February 2020. "How Native Tribes Are Taking the Lead on Planning for Climate Change." Yale Environment360. Available online at [accessed 6 April 2023].
  11. Brewer, P., Baixin, C., Haugan, P., Iwama, T., Johnston, P., Kheshgi, H., Li, Q., Ohsumi, T., Pörtner, H., Sabine, C., Shirayama, Y., & Thomson, J. 2005. "Oceans." In Carbon Dioxide Capture and Storage: Special Report of the Intergovernmental Panel on Climate Change. Available online at [accessed 29 November 2022].
  12. Kaplan, S. December 2021. "Is ‘hacking’ the ocean a climate change solution? U.S experts endorse research on carbon removal strategies." The Washington Post. Available online at [accessed 9 January 2023].
  13. Lindsey, R. April 19, 2022. "Climate Change: Global Sea Level." National Oceanic and Atmospheric Administration. Available online at [accessed 29 November 2022].
  14. Ibid.
  15. Hiraishi, T.,Krug, T.,Tanabe, K., Srivastava, N., Jamsranjav, B., Fukuda, M., & Troxler, T. 2013. "2013 Supplement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories: Wetlands." Intergovernmental Panel on Climate Change. Available online at [accessed 29 November 2022].