Cryosphere-atmosphere interactions in the global climate system
Steen, Robert Samuel
Ledley, Tamara Shapiro
Doctor of Philosophy
The climate system exhibits behavior on a wide range of time and spatial scales. Computer models that simulate climate must be faithful to these matters of scale in order to achieve meaningful results. This study involves the coupling of two models: a model that simulates the seasonal fluctuations of the atmosphere and ocean with a time constant on the order of one day and a continental ice sheet model designed to simulate the behavior of ice sheets over tens of thousands of years. These models are asynchronously coupled in both time and space because computational requirements limit the minimum grid size and time step size. Experiments are presented which examine the long time constant of the continental ice sheet and the fast approach to quasi-equilibrium of the seasonal model. Simulations of present day conditions from the coupled model are compared with climate observations and simulations of other climate models. These studies also show the sensitivity of model simulations of past climate to albedo changes, differing ice flow parameters, aerosol dust, lapse rate changes, and changes in carbon dioxide. The coupled model is then used to simulate a 120,000 year ice age cycle and mechanisms important over long time scales are discussed.
Physical geography; Atmospheric sciences