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What is our Focus Group About?
What is our Focus Group About?
Focus Group Statement
Focus Group Statement
The processes acting at the boundary between the Greenland Ice Sheet and the adjacent ocean represent a strong influence on the ice sheet’s contribution to sea level rise. These processes include iceberg calving and the melt of ice by relatively warm ocean waters that travel from the open ocean to the ice sheet margin. The Greenland ice-ocean focus group will develop and provide the ocean boundary conditions that meet the need of ice sheet modelers in incorporating these processes in their projections. Specific activities of this focus group include first, combining ocean observations with high-resolution ocean hindcasts to obtain our best estimate of how the ocean has changed over the past few decades. This will be used in calibration of the ice sheet models and to inform how we best use the lower-resolution global ocean projections. Second, we will create a mapping of ocean properties from the open ocean to the ice sheet margin, which is located at the head of narrow fjords. Third, we will update parameterizations for the melt of ice by warm ocean waters. Fourth, we will coordinate a consistent approach to the representation of iceberg calving in ice sheet models of diverse capabilities. Ultimately, from a given projection of coarsely-resolved global climate, we will develop the protocol to generate the glacier-by-glacier ocean boundary conditions needed to undertake projections of mass loss from the Greenland Ice Sheet.
ISMIP7 Greenland ocean protocol:
ISMIP7 Greenland ocean protocol:
1. Open ocean to fjord mouth
2. Fjord mouth to submarine properties
3. Submarine properties to frontal ablation
Open Ocean to Fjord Mouth:
Open Ocean to Fjord Mouth:
The goal is to retrieve ocean properties at each of Greenland’s fjord mouths more effectively than in ISMIP6.
Use CMIP model output (similar to ISMIP6)
Improved sampling locations, guided by Verjans et al., 2023
Increase resolution: monthly sampling instead of annual
Submarine properties to frontal ablation:
Submarine properties to frontal ablation:
This stage focuses on improving frontal ablation modeling beyond the ISMIP6 retreat parameterization.
Open Approach: Provide ocean forcing fields (m, TF, Q) and a calibration dataset
Floor: A suggested default parameterization for frontal ablation
Models can simulate frontal ablation using one of three paths:
Use Existing Parameterizations
If the model already includes calving/submarine melt parameterizations that depend on TF and Q
Develop a Custom Approach
Create a new parameterization as a function of thermal forcing and runoff if not already included
Adopt the Suggested Method - May come in two forms
Calving rate as a function of ice thickness + our submarine melt scheme
Thickness-threshold based calving + our submarine melt scheme
Fjord Mouth to Submarine Properties:
Fjord Mouth to Submarine Properties:
Ocean conditions are extrapolated from fjord mouths into the fjords, incorporating bathymetry while simplifying other fjord processes (e.g., Hager et al., 2024).
Subglacial discharge (Q) is calculated by summing runoff over glacier drainage basins
Submarine melt parameterizations (e.g., Sutherland et al., 2019; Jackson et al., 2022; Zhao et al., 2024) are being updated
Final goal: Provide monthly, 1 km x 1 km resolution fields:
Submarine melt rate
Ocean thermal forcing
Subglacial discharge
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