- continuous body of salt water covering 71% of Earth’s surface
- five oceans: Pacific, Atlantic, Indian, Southern, Arctic
- primary driver of climate through heat distribution, water cycle, and carbon cycle absorption
- thermohaline circulation moves heat from equator to poles as a global conveyor belt
- hosts the majority of planetary biomes by volume, from abyssal plains to coral reefs
- dissolved CO2 sink: absorbs ~30% of anthropogenic carbon
- source of energy: tidal, wave, thermal gradients
- plate tectonics creates mid-ocean ridges and deep trenches at subduction zones