Oceans & Seas

Oceans cover 71% of Earth, connecting continents, moderating climate, and hosting diverse ecosystems from sunlit shelves to abyssal trenches. Understanding their circulation, chemistry, and biology is central to grasping global change.

Basins, Shelves, and Margins

Continental shelves form productive shallows; slopes drop to abyssal plains punctuated by mid-ocean ridges and trenches like the Mariana Trench. Passive margins accumulate sediments; active margins pair with arcs along the Ring of Fire.

Circulation and Heat Transport

Surface gyres and boundary currents move heat poleward, while the thermohaline circulation—detailed in Ocean Currents—moves dense water globally. Upwelling zones (Humboldt, California) fuel fisheries and carbon cycling.

Marine Ecosystems

Coral reefs, kelp forests, seagrass meadows, and open-ocean gyres form distinct biomes outlined in Biomes and Ecosystems. Productivity peaks where light and nutrients align—coasts, upwelling zones, and some high-latitude seas.

Chemistry and Carbon

Oceans absorb ~25% of anthropogenic CO2, buffering climate but driving acidification that threatens calcifiers. Oxygen minimum zones expand with warming, altering habitat ranges and biogeochemical cycles.

Hazards and Change

Sea-level rise, marine heatwaves, and deoxygenation reshape coasts and fisheries. Tsunamis from subduction earthquakes link to geological processes. Polar sea-ice loss feeds back on circulation and climate (Polar Regions).