The Strongest Model Response Came From the Hardest Cracks to Observe
Satellite radar records fracture patterns across the surface of West Antarctic ice shelves. The crevasses that open from underneath have no comparable continental-scale map. In a new modeling study, surface damage generally matched the available satellite pattern more closely, while basal damage produced the larger simulated ice loss.
Ice shelves already float, so their own melting contributes little directly to sea level. Their mechanical role is to restrain grounded ice upstream. Fractures soften a shelf, faster flow changes the stress field, and the new stress field can deepen more fractures.
The Model Let Damage Evolve With the Ice
The researchers represented fracture damage as the combined modeled depth of surface and basal crevasses divided by total ice thickness. Damage reduced the ice’s effective viscosity. Flow, stress, fracture depth, transport, and healing were recalculated as each simulation advanced.
They ran 50-member ensembles from 2015 to 2300 under constant present-day conditions and under an idealized ocean-warming experiment. The ensemble sampled two parameters and carried no assigned probability. The calving front remained fixed, and the model excluded hydrofracture, melt-elevation feedback, and glacial isostatic adjustment.
Amundsen Sea Embayment ensemble means for three fracture treatments.
Blasco et al., Supporting Information, Table S1
Under idealized warming, undamaged ice produced a mean contribution of 54 millimeters. Holding the present-day damage field fixed raised the mean to 125 millimeters. Allowing damage to evolve raised it to 235 millimeters, with a full ensemble range of 88 to 320 millimeters.
Basal Damage Carried More Weight
The surface-only experiment produced a mean of 170 millimeters. The basal-only experiment produced 207 millimeters, compared with 235 millimeters when both forms of damage evolved. These interacting tests do not add cleanly, but they show the model’s greater sensitivity to fractures beneath the shelves.
Healing Changed the Projection Too
Compression and gravitational pressure can close crevasses. Removing those mechanical healing terms raised the warming mean from 235 to 346 millimeters. The authors described the resulting damage inside shelf interiors as unrealistic, making healing part of the governing result rather than a minor detail.
The Missing Map Sits Under the Ice
The study identifies a precise observational need. Researchers can compare modeled surface patterns with satellite imagery, while the basal crevasses that drive the strongest response remain sparsely measured. Direct maps of their depth and distribution would test the central mechanism where the current evidence is thinnest.