Effects of climate change on oceans
Human-driven climate change is warming and raising the sea, altering ocean chemistry and circulation, and reshaping marine ecosystems.
Ocean heat content: The thermal energy stored in ocean water, integrated across a chosen area or volume. The ocean absorbs most of the excess heat trapped by human greenhouse gas emissions.
Sea-level rise: A long-term increase in the average height of the sea relative to land. Ocean warming and melting land ice raise sea level, increasing coastal flooding and erosion.
Arctic sea ice decline: The long-term reduction in the extent, thickness, and persistence of sea ice in the Arctic. Rapid Arctic warming is shrinking seasonal sea ice and changing marine habitats.
Ocean acidification: The decline in seawater pH caused chiefly by ocean uptake of atmospheric carbon dioxide. Unlike warming, acidification stems directly from carbon dioxide changing seawater chemistry.
Atlantic meridional overturning circulation: A system of Atlantic currents that transports heat, salt, carbon, and nutrients between ocean regions and depths. Its future strength and regional effects remain uncertain across climate projections.
Thermal expansion: The increase in a material's volume as its temperature rises. Warming expands seawater and contributes to global mean sea-level rise.
Coral bleaching: The loss of symbiotic algae or pigments from corals, often triggered by heat stress. Marine heatwaves can push corals beyond their thermal tolerance and trigger bleaching.
Marine heatwave in the Northeast Pacific (2013–2016): An unusually persistent region of warm water in the Northeast Pacific from 2013 to 2016, widely called the Blob. This event demonstrates how unusual ocean warmth can disrupt food webs and fisheries.
Ocean warming hiatus: A period in the early twenty-first century when the rise in global surface temperature slowed relative to previous decades. Short-term pauses in surface warming did not mean the ocean stopped accumulating heat.
Antarctic ice-sheet stability: The capacity of the Antarctic Ice Sheet to persist without rapid, self-sustaining ice loss. Ice-sheet processes create uncertainty in projections of future sea-level rise.