Effects of climate change on oceansThere are many effects of climate change on oceans. One of the main ones is an increase inocean temperatures. More frequent marine heatwaves are linked to this. The rising temperature contributes to a rise in sea levels. Other effects include ocean acidification, sea ice decline, increased ocean stratification and reductions in oxygen levels. Changes to ocean currents including a weakening of the Atlantic meridional overturning circulation are another important effect. All these changes have knock-on effects which disturb marine ecosystems.
Ocean temperatureThe ocean temperature varies by depth, geographical location and season. Both the temperature and salinity of ocean water differs. Warm surface water is generally saltier than the cooler deep or polar waters; in polar regions, the upper layers of ocean water are cold and fresh. Deep ocean water is cold, salty water found deep below the surface of Earth's oceans. This water has a very uniform temperature, around 0-3 °C. The ocean temperature also depends on the amount of solar radiation falling on its surface.
Coral bleachingCoral bleaching is the process when corals become white due to various stressors, such as changes in temperature, light, or nutrients. Bleaching occurs when coral polyps expel the zooxanthellae (dinoflagellates that are commonly referred to as algae) that live inside their tissue, causing the coral to turn white. The zooxanthellae are photosynthetic, and as the water temperature rises, they begin to produce reactive oxygen species. This is toxic to the coral, so the coral expels the zooxanthellae.
Ocean heat contentOcean heat content (OHC) is the energy absorbed and stored by oceans. To calculate the ocean heat content, measurements of ocean temperature at many different locations and depths are required. Integrating the areal density of ocean heat over an ocean basin, or entire ocean, gives the total ocean heat content. Between 1971 and 2018, the rise in OHC accounted for over 90% of Earth’s excess thermal energy from global heating. The main driver of this OHC increase was anthropogenic forcing via rising greenhouse gas emissions.
Marine ecosystemMarine ecosystems are the largest of Earth's aquatic ecosystems and exist in waters that have a high salt content. These systems contrast with freshwater ecosystems, which have a lower salt content. Marine waters cover more than 70% of the surface of the Earth and account for more than 97% of Earth's water supply and 90% of habitable space on Earth. Seawater has an average salinity of 35 parts per thousand of water. Actual salinity varies among different marine ecosystems.
OceanThe ocean (also known as the sea or the world ocean) is a body of salt water that covers approximately 70.8% of the Earth and contains 97% of Earth's water. The term ocean also refers to any of the large bodies of water into which the world ocean is conventionally divided. Distinct names are used to identify five different areas of the ocean: Pacific (the largest), Atlantic, Indian, Southern, and Arctic (the smallest). Seawater covers approximately of the planet.
