Sensitivity of Tidewater Glaciers to Submarine Melting Governed by Plume Locations

• Published in: Geophysical research letters 2019-10, Vol.46 (20), p.11219-11227
• Main Authors: Cowton, Tom R., Todd, Joe A., Benn, Douglas I.
• Format: Article
• Language: English
• Subjects: Ablation; Calving; Compressive properties; Glacier melting; Glacier retreat; Glacier variations; Glaciers; Ice calving; Ice sheets; Iceberg calving; Icebergs; Mathematical models; Melting; Numerical models; Ocean warming; Oceans; Sea level; Sea level rise; Spatial variations; Submarine melting; Tidewater; Width
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2019GL084215

The response of tidewater glaciers to ocean warming remains a key uncertainty in sea level rise predictions. Here we use a 3‐D numerical model to examine the response of an idealized tidewater glacier to spatial variations in submarine melt rate. While melting toward the center of the terminus causes only a localized increase in mass loss, melting near the lateral margins triggers increased calving across the width of the glacier, causing the terminus to retreat at several times the width‐averaged melt rate. This occurs because melting near the margins has a greater disruptive impact on the compressive stress arch that transfers resistance from the side walls to the body of the glacier. We suggest that the rate of terminus advance or retreat may thus be governed by the difference between ice velocity and submarine melting in the slow‐flowing zones away from the glacier center. Plain Language Summary The rapid retreat of tidewater glaciers (i.e., glaciers that drain directly into the ocean) has become an increasing source of concern in recent years. Increased melting of the submerged parts of these glaciers by warming ocean waters is thought to be an important driver of this retreat, but exactly how glaciers respond to this submarine melting remains unclear. Using a numerical model, we find that tidewater glaciers may be most sensitive to melting close to the valleysides, which reduces structural support for the central section of the glacier and so triggers an increase in iceberg calving. By better constraining the relationships between submarine melting, calving, and glacier retreat, our findings allow improved prediction of the ice loss expected from tidewater glaciers as the climate continues to warm. Key Points We use a 3‐D numerical model to examine the response of an idealized tidewater glacier to spatial variations in submarine melt rate The glacier is most sensitive to melting near the lateral margins, which triggers increased calving across the width of the terminus Terminus retreat may thus be paced by the difference between ice velocity and submarine melting across slow flowing marginal zones