Modelling the surface mass balance of the Greenland ice sheet and neighbouring ice caps: a dynamical and statistical downscaling approach
The Greenland ice sheet (GrIS) is the world’s second largest ice mass, storing about one tenth of the Earth’s freshwater in the form of snow and ice. If totally melted, global sea level would rise by 7.4 m, affecting low-lying regions worldwide. Since the mid-1990s, increased atmospheric and oceanic...
| Main Author: | |
|---|---|
| Other Authors: | , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
| Published: |
Institute for Marine and Atmospheric reseacher Utrecht (IMAU)
2018
|
| Subjects: | |
| Online Access: | https://orbi.uliege.be/handle/2268/302210 https://orbi.uliege.be/bitstream/2268/302210/1/PhD-thesis-BNoel.pdf |
| Summary: | The Greenland ice sheet (GrIS) is the world’s second largest ice mass, storing about one tenth of the Earth’s freshwater in the form of snow and ice. If totally melted, global sea level would rise by 7.4 m, affecting low-lying regions worldwide. Since the mid-1990s, increased atmospheric and oceanic temperatures have accelerated GrIS mass loss through increased meltwater runoff and ice discharge across the grounding line of marine-terminating outlet glaciers. To understand the causes of recent GrIS surface-driven mass loss, we use the Regional Atmospheric Climate Model (RACMO2) to dynamically downscale climate. This meteorological model, coupled to a multi-layer snow model, simulates the evolution of the surface mass balance (SMB), i.e. the difference between snowfall accumulation and ablation from sublimation, drifting snow erosion and meltwater runoff. In this thesis, we show that RACMO2 realistically simulates the extent of the elevated inland accumulation zone, where the GrIS gains mass at the surface as snowfall exceeds sublimation and runoff, as well as the narrow ablation zone along the low-lying margins where mass is lost through runoff of meltwater exceeding snowfall. Separating these two areas is the equilibrium line, where accumulation and ablation cancel (SMB = 0). In order to cover a large domain at reasonable computational cost, RACMO2 is run at a relatively coarse horizontal resolution of 11 km (1958-2016). At this spatial resolution, the model does not well resolve small glaciated bodies, such as narrow marginal glaciers, typically only a few km wide, and small peripheral ice caps (GICs), detached from the main ice sheet. To address this issue, we developed a statistical downscaling algorithm that reprojects the original RACMO2 output on a 1 km ice mask and topography derived from the high-resolution Greenland Ice Mapping Project (GIMP) Digital Elevation Model (DEM). Correcting for surface elevation and ice albedo biases over the topographically complex GrIS margins, the downscaling procedure ... |
|---|