iceshelf

An ice shelf is a thick, floating platform of ice that forms where glaciers or ice sheets flow down to a coastline and extend over the ocean surface. Although it floats, it remains connected to land-based ice and is part of the same ice system. Ice shelves are most extensive in Antarctica and Greenland.

They form when glacier ice reaches the sea and becomes buoyant, displacing seawater. Ice shelves vary in thickness from tens to several hundreds of meters and can extend hundreds of kilometers from the coastline. The floating portion is held in place by contact with the land along its edges, but it undergoes processes such as calving, basal melting, and surface fracture.

The shelf acts as a buttress for the upstream glacier, helping to slow ice flow toward the sea. If shelves thin or collapse due to ocean warming, atmospheric warming, or increased calving, the inland ice can accelerate, potentially increasing sea-level rise. Calving produces icebergs, while warm ocean water beneath the shelf promotes basal melting. Surface water can cause hydrofracturing that weakens the structure. Because floating ice displaces water, melting of the shelf itself does not directly raise sea level; however, loss of the shelf reduces buttressing, which can lead to greater discharge of grounded ice and contribute to sea-level rise.

Examples include the Ross Ice Shelf in Antarctica, the Amery Ice Shelf, and the Larsen Ice Shelf series (A, B, C) in the Antarctic Peninsula. Monitoring relies on satellite imagery, radar, ocean measurements, and climate models. Ice shelves are a major focus in studies of the cryosphere and climate change due to their influence on glacier dynamics and sea-level projections.