Year

2024

Degree Name

Master of Philosophy

Department

School of Physics

Abstract

Earth experienced a large reduction in temperature variability in the transition from the Last Glacial Maximum (21,000 years ago) to the Holocene (11,000 years ago) as evidenced by the paleorecord. The aim of this thesis is to examine the role of ice sheets in this reduction of temperature variability through the development of a one dimensional Energy Balance Model of Earth’s climate. In addition, an analysis of current global climate data is completed to study the present state of Earth’s energy balance.

A one dimensional Energy Balance Model is developed to simulate past and present temperature variability. The simple model allows for computational integration over millennial time scales with annual resolution. As the ice line expands and retreats throughout glacial and interglacial periods the main descriptor used to define them is the latitude of their ice line. As such, the dimension chosen for the simple model is latitude and all climate parameters are made a function of this. Analysis of the most recent satellite data and evidence from literature is used in the model parameters to simulate each component of the model and determine initial conditions. Tuning of these parameters via a least squares method is done in order to ascertain realistic results for Earth’s current climate equilibrium. Following this, adjustments were made to simulate an equilibrium state with the increased ice line observed 18,000 years ago. Finally, the equilibrium state of current and past ice line equilibria underwent a process of forcing with a random and periodic function to measure their stability by calculating the variance in mean global temperature.

Simulations using the one dimensional Energy Balance Model show an increase in variability for the global mean temperature when ice sheets are extended from the present  72 N to the Last Glacial Maximum value of  60 N. These results are invariant to the method chosen to simulate the past ice line, either through changes in insolation or latitudinal energy transport. Calculations of the temperature variance show Earth’s climate experiences less variability with a smaller polar ice caps, as is observed in the paleorecord.

In the modern context, these results indicate that an observed contraction of the polar ice caps will play a key role in future climate stability.

FoR codes (2008)

0204 CONDENSED MATTER PHYSICS

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.