Editing Cryosphere Dynamics (section)

=== Albedo and Thermohaline Circulation ===
Sea ice plays two critical roles in the Earth System. First, it dictates the polar '''albedo'''. Brilliant white sea ice reflects a massive majority of incoming shortwave solar radiation back into space. When sea ice melts, it exposes dark ocean water, which absorbs the heat, warming the local environment and causing further ice melt—a powerful positive feedback loop.

Second, sea ice formation drives global ocean circulation. When seawater freezes, the ice crystal structure cannot easily accommodate salt ions. The salt is expelled into the surrounding ocean water through a process called '''brine rejection'''. This creates intensely cold, highly saline, and exceptionally dense water that sinks to the ocean floor, driving the deep-water thermohaline circulation (the global ocean conveyor belt).

Crucially, because sea ice is already floating in the ocean and displacing its own weight in water, the melting of sea ice does ''not'' directly contribute to global sea-level rise, much like a melting ice cube does not overflow a glass of water.