Why does the ocean appear different colors from space?

The answer

The ocean's color as seen from space depends primarily on what is in the water. Pure deep ocean water appears dark blue because water molecules absorb red wavelengths and scatter blue light. Phytoplankton-rich waters appear green because chlorophyll absorbs blue and red light, reflecting green. Sediment-laden coastal waters can appear brown or tan, while shallow tropical waters over white sand appear turquoise. NASA's satellites use ocean color data to map phytoplankton distribution globally, as changes in ocean color can signal shifts in marine productivity, algal blooms, and ecosystem health. A 2023 study found that over 56% of ocean surface area has shifted color in the past two decades, likely due to climate change.