Catalog / Oceanography Cheatsheet
Oceanography Cheatsheet
A quick reference guide to the key concepts, processes, and features in oceanography, covering ocean properties, dynamics, marine life, and human impacts.
Ocean Properties
Seawater Composition
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Salinity |
Measure of dissolved salts in seawater (typically expressed in parts per thousand, ‰). Average ocean salinity is around 35‰. |
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Major Ions |
Chloride (Cl⁻), Sodium (Na⁺), Sulfate (SO₄²⁻), Magnesium (Mg²⁺), Calcium (Ca²⁺), Potassium (K⁺). |
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Density |
Determined by temperature, salinity, and pressure. Density increases with decreasing temperature and increasing salinity/pressure. |
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pH |
Seawater is slightly alkaline, with a typical pH range of 7.5 to 8.5. |
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Gases |
Dissolved gases include oxygen (O₂), carbon dioxide (CO₂), and nitrogen (N₂). Oxygen is vital for marine life, while CO₂ influences ocean acidity. |
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Nutrients |
Nitrates, phosphates, and silicates are essential nutrients for phytoplankton growth. |
Temperature Profiles
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Thermocline - Layer of rapid temperature change with depth. Separates the warm surface waters from the cold deep waters. |
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Isothermal - Having a uniform temperature. Polar regions often exhibit isothermal conditions. |
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Mixed Layer - Surface layer with relatively uniform temperature due to wave action and wind mixing. |
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Deep Ocean - Cold and relatively stable temperatures, typically around 2-4°C. |
Light Penetration
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Euphotic Zone |
Upper layer of the ocean where sufficient light penetrates for photosynthesis (typically down to 100-200 meters). |
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Disphotic Zone |
Also known as the twilight zone, where light is minimal and insufficient for photosynthesis. |
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Aphotic Zone |
Deep ocean zone where no light penetrates. |
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Factors Affecting Penetration |
Water clarity, suspended particles, and dissolved substances. |
Ocean Dynamics
Ocean Currents
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Surface Currents |
Driven by wind patterns and influenced by the Coriolis effect. Important for heat distribution around the globe. |
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Deep Ocean Currents |
Driven by density differences (thermohaline circulation). Critical for nutrient transport and climate regulation. |
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Gyres |
Large circular currents formed by wind patterns and the Coriolis effect (e.g., North Atlantic Gyre). |
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Upwelling |
Process where deep, nutrient-rich water rises to the surface, supporting high biological productivity. |
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Downwelling |
Process where surface water sinks, transporting oxygen and nutrients to deeper layers. |
Waves and Tides
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Waves |
Generated by wind. Wave height, wavelength, and period are key characteristics. Breakers occur when waves approach the shore. |
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Tides |
Periodic rise and fall of sea level caused by the gravitational forces of the Moon and Sun. |
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Spring Tides |
Occur during new and full moons when the Sun, Earth, and Moon are aligned, resulting in higher high tides and lower low tides. |
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Neap Tides |
Occur during first and third quarter moons when the Sun, Earth, and Moon form a right angle, resulting in lower tidal ranges. |
Ocean-Atmosphere Interactions
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El Niño-Southern Oscillation (ENSO) - Periodic climate pattern involving changes in sea surface temperatures in the central and eastern tropical Pacific Ocean. Affects global weather patterns. |
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La Niña - Opposite phase of El Niño, characterized by cooler-than-average sea surface temperatures in the central and eastern tropical Pacific. |
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Hurricanes/Typhoons - Intense tropical cyclones that form over warm ocean waters. Transfer heat and energy from the ocean to the atmosphere. |
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Ocean Acidification - The ongoing decrease in the pH of the Earth’s oceans, caused by the uptake of carbon dioxide (CO₂) from the atmosphere. |
Marine Life and Ecosystems
Marine Organisms
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Phytoplankton |
Microscopic algae that form the base of the marine food web. Perform photosynthesis. |
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Zooplankton |
Microscopic animals that feed on phytoplankton and other zooplankton. |
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Nekton |
Actively swimming organisms, such as fish, marine mammals, and squid. |
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Benthos |
Organisms that live on or in the seafloor, such as crabs, worms, and sea stars. |
Marine Ecosystems
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Coral Reefs - Highly diverse ecosystems found in warm, shallow waters. Built by coral polyps. Threatened by bleaching and ocean acidification. |
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Kelp Forests - Underwater ecosystems dominated by kelp. Provide habitat and food for many marine species. |
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Estuaries - Coastal areas where freshwater rivers meet the ocean. Highly productive due to nutrient input. |
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Deep-Sea Vents - Hydrothermal vents that release chemicals from the Earth’s interior. Support unique chemosynthetic communities. |
Ecological Interactions
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Food Webs |
Complex networks of organisms that transfer energy and nutrients through feeding relationships. |
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Symbiosis |
Close ecological relationship between two different species (e.g., mutualism, commensalism, parasitism). |
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Predation |
One organism (the predator) consumes another organism (the prey). |
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Competition |
Occurs when organisms compete for limited resources (e.g., food, space). |
Human Impacts on the Ocean
Pollution
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Plastic Pollution - Accumulation of plastic waste in the ocean. Harms marine life through entanglement, ingestion, and habitat destruction. |
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Chemical Pollution - Introduction of harmful chemicals (e.g., pesticides, heavy metals) into the ocean. Can lead to bioaccumulation and biomagnification in the food web. |
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Nutrient Pollution - Excessive input of nutrients (e.g., nitrogen, phosphorus) from agricultural runoff and sewage. Can cause eutrophication and harmful algal blooms. |
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Oil Spills - Release of crude oil into the ocean. Devastating to marine ecosystems and wildlife. |
Overfishing
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Definition |
Harvesting fish at a rate faster than they can reproduce, leading to population declines. |
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Impacts |
Disrupts marine food webs, reduces biodiversity, and affects livelihoods of coastal communities. |
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Sustainable Practices |
Implementing fishing quotas, protecting marine reserves, and promoting responsible aquaculture. |
Climate Change
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Ocean Warming - Increasing ocean temperatures due to global warming. Leads to coral bleaching, shifts in species distributions, and altered ocean currents. |
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Sea Level Rise - Rising sea levels due to thermal expansion of water and melting of glaciers and ice sheets. Threatens coastal communities and ecosystems. |
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Ocean Acidification - The ongoing decrease in the pH of the Earth’s oceans, caused by the uptake of carbon dioxide (CO₂) from the atmosphere. |
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Changes in Ocean Currents - Altered circulation patterns can affect heat distribution, nutrient transport, and marine life. |