Climate Impacts

three photos show a bleaching event that occurred over three months
Impacts from climate change can include (left to right) sea level rise and flooding as shown in Port Arthur, Texas after Hurricane Harvey; more powerful hurricanes including the Category 4 Hurricane Michael that struck the Florida panhandle; and coral bleaching as seen here in National Marine Sanctuary of American Samoa. Photos: D.J. Martinez and NOAA

We are beginning to see climate-related impacts in many national marine sanctuaries and in the surrounding communities. The impacts include the following. For more information on climate science, visit

Rising Sea Level

map of weekly average sea surface temperatures from 2016
Sea level rise is making low-lying coastal areas like Tybee Island, Georgia, more vulnerable to frequent and widespread flooding. Since 1935, as measured by a local NOAA tide gauge, the beach community has experienced 10 inches of sea level rise. Sanctuaries help educate local communities about climate science. Photo: J. Evans

The melting of ice sheets and glaciers, combined with the thermal expansion of seawater as the ocean warms, is causing sea level to rise. Seawater is increasingly flooding low-lying land, submerging coastal habitats, facilities, and roads, and contaminating coastal freshwater habitats and sources. Sea level rise increases the risk of damage to homes and buildings from storm surges, such as those that accompany hurricanes.

  • Rising sea level will encroach upon shorelines, narrowing beaches, increasing erosion, and affecting coastal ecosystems in our national marine sanctuaries, including nesting habitat for seabirds and marine mammal haul-out sites.

  • Rising sea level may damage docks, boat houses, and other coastal structures, as well as those owned and operated by individuals and companies that use sanctuary resources (e.g., fishermen, whale watch companies, divers).

  • Coastal flooding from rising sea level mobilizes pollutants and fertilizers that drain into the ocean, creating harmful algal blooms and ocean dead zones.

Ocean’s Influence on Weather and Climate

tropical storms in the atlantic ocean wide view
Rising ocean and air temperatures provide fuel for more powerful hurricanes. These tropical weather systems were observed with the GOES-16 satellite on September 9, 2018 over the northwest Atlantic Ocean. Shown (right to left) are Tropical Storm Helene, Tropical Depression Nine, Hurricane Florence, and an unnamed low pressure system over the Florida peninsula. Photo: NOAA

Covering 70 percent of Earth’s surface, the ocean exerts major control on climate by dominating Earth’s energy and water cycles. It absorbs vast amounts of solar energy. Heat and water vapor are redistributed globally through ocean currents and atmospheric circulation. Changes in ocean circulation caused by movements in Earth’s crust or large influxes of fresh water from melting polar ice can lead to significant and even abrupt changes in climate, both locally and on global scales.

  • Increased storm frequency and intensity, coupled with higher wave heights, are increasing impacts to national marine sanctuary habitats, coastal infrastructure, and communities.

  • Changes in upwelling regimes have large biological effects on national marine sanctuaries along the West Coast of the United States. Persistent and warmer sea surface temperatures could lead to long-term changes in the magnitude and timing of ocean upwelling.

  • The direct and indirect effects of climate change on oceanographic processes, such as ocean circulation, are already affecting marine and coastal ecosystems.

Ocean Acidification

sorting the catch
A recent study suggests that future ocean acidification conditions may result in long-term decline of the $500 million annual Atlantic sea scallop fishery, despite increased management. Photo: NOAA

Ocean acidification changes the chemistry of the ocean and has been called “osteoporosis of the sea.” It prevents some plants and animals at the base of the food web, as well as many larger organisms like shellfish and corals, from building and maintaining the protective skeletons or shells they need to survive. Ocean acidification also affects the behavior of marine organisms, such as settlement in corals and fish and the ability to locate prey in fish. This has the potential to fundamentally change marine ecosystems, food webs, and habitats globally, including national marine sanctuaries. Research provides a baseline for monitoring change in sanctuary ecosystems and will help us better understand and respond to these emerging threats. Learn more about ocean acidification and NOAA’s work to understand and address it here.

Changing Climate, Changing Species

black mangrove trees encroaching into a saltmarsh cordgrass wetland
Black mangrove trees encroaching into a saltmarsh cordgrass wetland near the northern edge of mangrove range limits, Guana Tolomato Matanzas National Estuarine Research Reserve, Florida. Photo: J. Parker. Right: Tropicalization of seagrass meadows is occurring in the northern Gulf of Mexico, where species such as this stoplight parrotfish (typically associated with coral reefs) can now be observed that were absent from surveys in the 1970's. Photo: Adona9

Globally, species are on the move due to climate impacts. In the ocean, many species are moving toward the poles or into deeper water. In the Northeast Atlantic, for example, species have moved north and into deeper waters seeking preferred temperatures.