Decadal Evolution of Ice‐Ocean Interactions at a Large East Greenland Glacier Resolved at Fjord Scale With Downscaled Ocean Models and Observations

• Published in: Geophysical research letters 2024-04, Vol.51 (7), p.n/a
• Main Authors: Wood, M., Khazendar, A., Fenty, I., Mankoff, K., Nguyen, A. T., Schulz, K., Willis, J. K., Zhang, H.
• Format: Article
• Language: English
• Subjects: Ablation; Accelerated flow; Annual variations; Circulation; Continental shelves; Fjords; Glaciation; Glacier flow; Glacier ice; Glacier melting; Glacier retreat; Glaciers; Greenland glaciers; Greenland ice sheet; Ice; Ice sheets; ice‐ocean interactions; Interannual variations; Ocean models; Ocean temperature; Ocean temperature variability; Oceans; regional ocean modeling; remote sensing; Satellite observation; Scale models; sea level rise; Shelf dynamics; Simulation; Temperature variability; Variability
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2023GL107983

In recent decades, the Greenland ice sheet has been losing mass through glacier retreat and ice flow acceleration. This mass loss is linked with variations in submarine melt, yet existing ocean models are either coarse global simulations focused on decadal‐scale variability or fine‐scale simulations for process‐based investigations. Here, we unite these scales with a framework to downscale from a global state estimate (15 km) into a regional model (3 km) that resolves circulation on the continental shelf. We further downscale into a fjord‐scale model (500 m) that resolves circulation inside fjords and quantifies melt. We demonstrate this approach in Scoresby Sund, East Greenland, and find that interannual variations in submarine melt at Daugaard‐Jensen glacier induced by ocean temperature variability are consistent with the decadal changes in glacier ice dynamics. This study provides a framework by which coarse‐resolution models can be refined to quantify glacier submarine melt for future ice sheet projections. Plain Language Summary Over the past several decades, the Greenland ice sheet has been losing ice and contributing to sea‐level rise. About half of this ice loss is induced by melt that occurs where glaciers meet the ocean. Using coarse‐scale ocean models that simulate circulation around the globe, previous studies have noted a strong link between ocean temperature and enhanced glacier ice loss. However, due to the small scale of Greenland's fjords, coarse models are unable to directly quantify circulation in these fjords and melt on submerged glaciers. In this study, we develop a new framework to “zoom in” on a fjord, using high‐resolution models driven by larger coarse‐resolution models. In this approach, we simulate melt on one of Greenland's biggest glaciers and find that periods of higher melt coincide with more ice loss as observed from satellites. Since this framework is adaptable to other regions, it could also be used to simulate melt on other glaciers and support estimates of future sea‐level rise. Key Points Subsurface temperature variability is simulated in a narrow fjord network using regional models downscaled from a global state estimate Modeled increases in ocean melt at Daugaard‐Jensen glacier coincide with the onset of acceleration in 2005 and retreat and thinning in 2011 Model variations in shelf‐to‐fjord ocean properties match with observations, providing a basis to estimate ocean forcing in ice projections