Simulation of the Global Coupled Climate/Ice Sheet System over Millennial Timescales

• Main Author: Fyke, Jeremy
• Other Authors: Carter, Lionel, Mackintosh, Andrew
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Victoria University of Wellington 2011
• Subjects: Model; Paleoclimate; Climatic change; Antarctic; Greenland; The Antarctic; West Antarctic Ice Sheet; Antarc*; Ice Sheet; Ice Shelves
• Online Access: http://researcharchive.vuw.ac.nz/handle/10063/1932

Ice sheets are important components of the Earth system that are expected to respond strongly to anthropogenic forcing of climate. The aim of this work is to use numerical climate and ice sheet modelling to identify and understand the millennial-scale interaction between the Antarctic and Greenland Ice Sheets (AIS and GIS) and global climate. An initial modelling effort evaluated the response of ice shelves and ice sheets to future CO2 emission scenarios by quantifying the duration and magnitude of summer melt periods. A temperature threshold based on positive degree days was applied to bias-corrected University of Victoria Earth System Climate Model (UVic ESCM) output spanning 1000 years into the future. The simulations indicated that an increase in summer melting over most of the GIS, the Ross and Ronne-Filchner ice shelves, and large sections of the West Antarctic Ice Sheet (where little present-day ablation occurs) could occur if future emissions are not curtailed. This initial work highlighted the need to assess the dynamic response of ice sheets to climate change. I therefore developed an ice sheet/climate model comprised of the UVic ESCM and the Pennsylvania State University Ice Sheet Model. Coupling these models required development of new techniques, including subgrid-scale energy balance calculations that incorporate a surface air temperature (SAT) model bias correction procedure. In testing the model, I found that climate model SAT bias, meltwater refreezing and albedo variations play an important role in simulated ice sheet evolution, particularly as more of the ice surface experiences melting conditions. The model realistically reproduced the AIS and GIS, and captured the surface mass balance (SMB) distributions for both ice sheets well for the present day, including narrow GIS ablation zones. The newly developed model was used to carry out a suite of experiments designed to assess the behavior of the GIS under elevated-CO2 conditions. A deglacial SMB-based GIS stability threshold was identified ...