Editing Cryosphere Dynamics (section)

== Mechanisms of Global Sea-Level Rise ==

Global sea-level rise is driven by two primary mechanisms: '''thermal expansion''' (as ocean water warms, it becomes less dense and physically expands) and the '''addition of new mass''' from the cryosphere.

Only the melting of grounded land ice—ice sheets and mountain glaciers—adds new water to the ocean basin. 
* '''Mountain Glaciers:''' While containing only a fraction of the total land ice, the rapid melting of alpine glaciers in regions like the Himalayas, the Andes, and the Alps is currently a major contributor to sea-level rise.
* '''The Greenland Ice Sheet:''' Experiencing extensive surface melting and rapid calving of marine-terminating glaciers, Greenland is the largest current contributor of new mass to the global ocean.
* '''The Antarctic Ice Sheet:''' Antarctica holds enough frozen water to raise global sea levels by nearly 60 meters. A major focus of physical glaciology is the '''Marine Ice Sheet Instability (MISI)'''. In areas where the bedrock slopes downward toward the interior of the continent, the point where the glacier lifts off the bedrock and begins to float (the grounding line) can retreat rapidly. As the grounding line retreats into deeper water, the flow of ice inevitably accelerates, potentially leading to irreversible, runaway ice loss over centuries.

Understanding the physics of the cryosphere is essential for forecasting both the near-term impacts of climate change and the long-term, multi-century trajectory of global coastlines.