How Climate Change is Affecting Our Oceans
Our oceans play an integral role in global climate and weather patterns. Nevertheless, they are also vulnerable to the effects of climate change.
Warming oceans have been linked to ice-melting, sea level rise and ocean acidification. These impacts are causing unprecedented cascading effects.
As Earth warms, the ocean absorbs more heat, affecting our weather and climate. This is largely caused by human activity, but natural sources also contribute to global warming.
Scientists estimate that the amount of heat stored in the ocean has increased since the 1950s. As a result, ocean temperatures have been rising around the world for several decades.
This is especially true in the tropics, where warmer water encourages more intense hurricanes and storms. Sea level is also rising globally, adding to concerns for coastal communities.
Our oceans have absorbed about 90 percent of excess heat in the climate system over the past century and 20 to 30 percent of CO2 emissions, which is changing our ocean’s chemical composition (causing ocean acidification). This poses a serious threat to the marine environment, particularly creatures with calcified shells or skeletons like oysters, clams and coral.
As the ocean expands and melts, it raises sea level, which can increase flooding of homes and roads by storm surges. Rising sea levels also affect critical marine habitats, such as coral reefs and mangrove forests, by delaying their migration into shallower waters where they can thrive.
Scientists have better understanding of how sea level changes around the world because of satellites, which measure sea level continuously and are more precise than tide gauges. The first satellite altimeter was Topex/Poseidon launched in 1992 and subsequent satellites, such as Jason-1 and Jason-2, have helped to monitor global sea level change more accurately.
In the past, sea level has risen and fallen dramatically in our planet’s glacial cycles, but it’s been accelerating since 1850 due to greenhouse gas emissions. These changes are projected to continue and may be much more severe in the future.
As a global heat sink, the ocean absorbs energy from carbon dioxide (CO2) dumped into the atmosphere by burning fossil fuels. But the seas have a limit to how much heat they can absorb.
Climate scientists are now tracking the way our oceans are changing, in particular how salty areas of the sea are getting saltier and fresher areas are getting fresher. That is affecting the water cycle and making it turn over faster, increasing the likelihood of extreme precipitation in dry places and flooding in wet ones.
Salinity changes can be a good indicator of water cycle change because they very sensitively reflect the net exchange of freshwater between the ocean and the atmosphere. Evaporation takes freshwater into the ocean, reducing its saltiness, while precipitation puts it into the atmosphere, enhancing its salinity.
As the carbon dioxide from burning fossil fuels dissolves into ocean water, it lowers the pH of that water. This change can be harmful to sea creatures that rely on carbonate ions for their shells and skeletons.
Corals, oysters and other commercially important marine organisms will have a harder time building their shells. Fish will also take in carbonic acid from the ocean, changing the pH of their blood and affecting their health.
Scientists are doing experiments to test the effects of ocean acidification on different species and their ability to adapt to new conditions. For instance, scientists in the Biological Impacts of Ocean Acidification (BIOACID) project are testing how plankton react to more acidic seawater.
Despite these challenges, we can help ensure that our oceans stay healthy by taking action now to reduce our global carbon emissions. If you want to learn more about how to do that, sign up for Climate Reality’s email activism list!