Oceanography Glossary

The vast, flat areas of the deep ocean floor lying between approximately 4,000 and 6,000 meters depth, covered in fine sediment and representing the largest habitat on Earth.

The measurement and mapping of the depth and topography of the ocean floor, analogous to topography on land, using techniques such as sonar, satellite altimetry, and multibeam echosounders.

The suite of biological processes that transfer carbon from the sunlit ocean surface to the deep sea through the sinking of organic particles, fecal pellets, and dead organisms.

The shallow, gently sloping submerged edge of a continent extending from the shoreline to the continental slope, typically to depths of about 200 meters.

The loss of symbiotic zooxanthellae algae from coral tissue, typically caused by prolonged elevated sea temperatures, leaving the coral white and at risk of starvation and death.

The apparent deflection of moving objects caused by Earth's rotation, which deflects ocean currents and winds to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

The net movement of surface water at a 90-degree angle to the prevailing wind direction, caused by the combined effect of wind stress and the Coriolis effect on successive layers of water.

The warm phase of the ENSO cycle, characterized by above-normal sea surface temperatures in the central and eastern tropical Pacific, which disrupts normal atmospheric circulation and global weather patterns.

A partially enclosed coastal body of water where freshwater from rivers and streams meets and mixes with saltwater from the ocean, creating a highly productive and ecologically important transitional habitat.

The uppermost layer of the ocean, extending to approximately 200 meters depth, where sufficient sunlight penetrates to support photosynthesis and primary production.

A layer in the ocean where salinity changes rapidly with depth, creating a density gradient that can inhibit vertical mixing between water masses of different salinity.

An opening in the seafloor at a tectonically active area where geothermally superheated, mineral-laden water is discharged into the ocean, supporting chemosynthetic ecosystems.

A continuous shower of mostly organic detritus falling from the upper layers of the ocean to the deep sea, consisting of dead organisms, fecal material, and other biological particles.

An underwater mountain range formed at divergent tectonic plate boundaries where magma rises to create new oceanic crust through seafloor spreading.

The decrease in ocean pH caused by the absorption of atmospheric CO2, which forms carbonic acid in seawater and reduces the availability of carbonate ions for calcifying organisms.

A large system of rotating ocean currents driven by wind patterns and the Coriolis effect, with five major gyres circulating in the Atlantic, Pacific, and Indian Oceans.

Microscopic photosynthetic organisms that drift in the sunlit upper ocean, forming the base of most marine food webs and producing roughly half of global atmospheric oxygen.

A layer of water where density increases rapidly with depth, typically resulting from combined changes in temperature and salinity, acting as a barrier to vertical water mixing.

The total concentration of dissolved inorganic salts in seawater, typically measured in parts per thousand (ppt), with an average value of about 35 ppt in the open ocean.

The geological process by which new oceanic lithosphere is created at mid-ocean ridges as tectonic plates diverge and magma rises to solidify into new crust.

A distinct layer in the ocean where water temperature drops rapidly with increasing depth, separating the warm surface mixed layer from the cold deep ocean.

The global-scale ocean circulation driven by density differences resulting from variations in temperature and salinity, redistributing heat from the equator toward the poles.

A series of large, long-wavelength ocean waves generated by sudden seafloor displacement from earthquakes, volcanic eruptions, or submarine landslides, capable of devastating coastal areas.

The vertical movement of cold, nutrient-rich water from the deep ocean to the surface, driven by wind patterns and the Coriolis effect, supporting high biological productivity.

Small heterotrophic organisms that drift in the ocean and feed on phytoplankton and other particles, forming a critical link between primary producers and higher trophic levels in the marine food web.