Ocean and Climate

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Changing climate influences many aspects of the ocean, from warming surface waters and altering ocean chemistry to affecting ecosystem function and health. The ocean and its circulation patterns are critical drivers of Earth’s climate and weather patterns.

With the ocean covering more than 70% of the Earth, it plays a large role in controlling the planet’s temperature. The ocean absorbs an enormous amount of heat from the sun—in fact, the top few meters alone store as much heat as the Earth’s atmosphere! As water is very good at storing heat, it spreads the heat around the planet through circulating currents driven by temperature and density differences. These global circulation patterns affect our daily weather and influence long-term climate patterns.  

A Changing Ocean

As water heats up, it also expands in volume—a process known as thermal expansion—which causes sea levels to rise. As the Earth warms and cools, the volume of the ocean changes, affecting the volume of ice and land areas covered with ocean or ice. These changes can occur abruptly, such as during transitions from glacial to interglacial conditions, or over long periods of time. Learn more about sea level rise research here. 

Changes in water temperatures, salinity and other chemical properties, can alter related circulation patterns. Altogether, these changes can also affect the behavior and physiology of many species by having profound impacts on the timing and availability and timing such as changing food webs, of food, reproduction and migratory patterns.  Coral bleaching is one way corals respond to warming sea water temperatures.

The ocean also absorbs gases, which can affect its chemical properties. For example, as carbon dioxide in the atmosphere is absorbed by the ocean, it causes the pH to lower in a process called ocean acidification. Ocean acidification can lead to dissolution of the shells and skeletons of many marine organisms—including economically important shellfish in the seafood industry and ecologically important corals that support biodiversity. It can also dissolve carbonate sediment and alter seafloor elevation and form. USGS monitors the effects of ocean acidification on coastal and marine ecosystems to help inform efforts to mitigate these impacts.  

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USGS Ocean and Climate Research

Ocean science is critical to improving the understanding of Earth's inner workings. From remote-sensing to marine geology and paleoclimate analyses, USGS is an important partner with other federal agencies and international experts working to expand our knowledge about Earth's climate history, especially as related to current conditions. This science improves our ability to understand the factors that affect climate change as well as forecast future climate conditions, their potential impacts and how best to mitigate or adapt to them. 

With remote-sensing technology, for example, cameras on satellites can make images of temperature shifts in the open ocean or monitor changes in the formation of sea ice at the poles. Remote-sensing also includes sonar systems on ships, which can be used to create images of the ocean floor and uncover clues about past climatic conditions: USGS researchers studying iceberg tracks, or scours, on the Atlantic seafloor found that during the Last Glacial Period 30,000 years ago, icebergs perhaps as tall as the Eiffel Tower drifted south along the Atlantic coast of North America, ferried along by cold-water currents created during periods of catastrophic glacial melting. 

The USGS develops and uses innovative methods to measure climatic and oceanic conditions throughout Earth’s history including sea surface and bottom water temperatures, salinity, relative sea level, precipitation patterns, oceanic productivity, and terrestrial inputs to the ocean system. Data on past climatic conditions in the oceans—the study of geologic records known as paleoceanography—can be combined with data on current conditions to try to predict how our ocean will affect Earth’s future climate patterns. 

In order to understand the past, USGS scientists analyze “proxies” which serve to indicate past conditions through biological or geological evidence. Some proxies include marine sediment and organisms that secrete their shells from seawater such as plankton, clams, and corals. Proxies for seawater geochemistry reflect the environmental conditions when and where they were formed. These proxies obtained in geologic deposits serve as archives that can be used to reconstruct Earth’s historic conditions so we can better predict what changes might occur in the future. 

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