Proceedings of the National Academy of Sciences, 8 May 2023<\/p>\n
Warm seawater can flow many kilometers underneath glaciers as tides periodically lift the ice off the seafloor, exposing its vulnerable underside to warm ocean waters. This newly observed ice-ocean dynamic suggests that current models may underestimate the potential rate of future sea level rise from some parts of Greenland and Antarctica. Ice shelves extend from land-based glaciers to float on the surface of the ocean, where rising and falling tides cause them to pull the base of the ice away from the ground. This motion transforms a semi-stable \u201cgrounding line\u201d where glaciers meet the ocean, into a multi-kilometer \u201cgrounding zone\u201d where some of the highest rates of melting occur. In this study, researchers found that the large Petermann glacier in NW Greenland, which drains a major portion of the ice sheet, has a grounding zone that migrates between 2-6 kilometers daily as tides come in and out, creating a huge cavity in the bottom of the glacier. These findings dispel the notion that grounding lines are invulnerable to tidal cycles, and make clear that tides can produce rapid ice loss, with serious implications for the future stability of some Greenland and Antarctic glaciers.<\/p>\n