Oceanography Cheat Sheet

The core ideas of Oceanography distilled into a single, scannable reference — perfect for review or quick lookup.

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Quick Reference

Thermohaline Circulation

The large-scale, density-driven circulation of the global ocean, often called the Great Ocean Conveyor Belt. It is powered by differences in water temperature and salinity, which affect density and cause water masses to sink or rise, driving a continuous loop of deep and surface currents that redistributes heat around the planet.

Ocean Acidification

The ongoing decrease in the pH of the Earth's oceans caused by the uptake of atmospheric carbon dioxide. When CO2 dissolves in seawater it forms carbonic acid, lowering pH and reducing the availability of carbonate ions that marine organisms need to build shells and skeletons.

Upwelling

A process in which deep, cold, nutrient-rich water rises to the ocean surface, typically driven by wind patterns and the Coriolis effect pushing surface water away from a coastline. Upwelling zones are among the most biologically productive areas in the ocean.

El Nino-Southern Oscillation (ENSO)

A periodic climate pattern involving fluctuations in sea surface temperature and atmospheric pressure across the tropical Pacific Ocean. ENSO alternates between warm phases (El Nino), cool phases (La Nina), and neutral conditions, with profound impacts on global weather, fisheries, and ecosystems.

Tidal Forces

The gravitational pull exerted primarily by the Moon and secondarily by the Sun on Earth's oceans, causing the regular rise and fall of sea levels known as tides. The relative positions of the Moon, Sun, and Earth determine whether tides are especially strong (spring tides) or weak (neap tides).

Hydrothermal Vents

Openings on the ocean floor where geothermally heated water erupts into the surrounding seawater, often at mid-ocean ridges. These vents support unique chemosynthetic ecosystems that derive energy not from sunlight but from chemical reactions involving hydrogen sulfide and other compounds.

Salinity

The concentration of dissolved salts in seawater, typically expressed in parts per thousand. Salinity varies geographically and with depth, influenced by evaporation, precipitation, freshwater runoff, and ice formation, and it plays a key role in determining water density and driving ocean circulation.

Continental Shelf

The gently sloping underwater extension of a continent, stretching from the shoreline to the shelf break where the seafloor drops steeply toward the deep ocean. Continental shelves are shallow, sunlit, nutrient-rich areas that support the majority of the world's commercial fisheries.

Marine Food Web

The complex network of feeding relationships among organisms in the ocean, beginning with primary producers such as phytoplankton and extending through multiple trophic levels to apex predators. Energy and nutrients flow through the food web, with each level supporting the next.

Sea-Level Rise

The increase in the average level of the world's oceans over time, driven primarily by thermal expansion of warming seawater and the melting of land-based ice sheets and glaciers. Sea-level rise threatens coastal communities, infrastructure, and ecosystems globally.

Key Terms at a Glance

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

Upwelling: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.

Ocean Acidification: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.

Salinity: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.

Phytoplankton: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.

Thermocline: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.

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

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

Coriolis Effect: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.

Ocean Gyre: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.

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

Abyssal Plain: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.

Ekman Transport: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.

Biological Pump: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.

Coral Bleaching: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.

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