# Introduction to ice sheet modeling

## Is there a theoretical basis for ice-sheet modeling?

There are 3 answers to this question: yes, no, maybe. "Yes" applies to the fact that ice-sheet modeling (for the most part) is based on a physical description of nature that is amenable to simulation with computers. A physicist will explain that ice sheets, and all the phenomena they display, can be described by simple conservation laws, such as those which describe how the temperature of the ice changes with time, or how water flows at the base of the ice sheet. Computational continuum mechanics provides a ready framework for describing how these laws evolve in particular domains via particular forcing schedules. These two facts: the existence of conservation laws and the amenability of computation as a means to understand those laws motivate the notion of a *theoretical* basis to ice-sheet modeling.

But, "No"! A theoretical basis is not sufficient in the natural sciences. Nature poses phenomena that are only partially knowable through the mechanisms of conservation laws and computation; this is because "observation" is the unstated action that the knower of laws and performer of computations must do in order to evaluate the meaning of ice-sheet modeling. Without observation as a means of igniting the *trial and error* process that makes ice-sheet modeling meaningful, ice-sheet modeling cannot exist as a scientific enterprise.

Even so, even with the deeply seated understanding of conservation laws, the incredible skill and power of computational continuum mechanics, and the wisdom imparted by decades of ice-sheet observation, one must doubt the notion that ice-sheet modeling is an enterprise that has a basis. This is because the motivation for ice-sheet modeling, at least within the context of this summer school, is the notion of prediction, and this is primarily a sociological notion. Is the sociological benefit of prediction a sufficient basis for ice-sheet modeling? Maybe. The answer to this question is unknown, as it depends on you, the student, on what you think, what you do and what you learn.

*Ice-sheet Modeling?! This secret is an insult to the Creation! It ravages the many tongues of Assur! It disturbs the order of heavenly spheres and breaks the Nine Schools of snow-flake geometry! It makes the Sixteen Predicaments, the Eighteen Sciences and the Fourty-Two Unresolved Glaciological Issues seem like mere promiscuities! What I shall do is conceive of a great enchantment.* -- Snowman Rusdown, from *The Satanic Flowlaw.*

## Ice sheet models

Start with laminar flow, the "backbone" of all models. How do we go from simple ice flow to getting a computer model?

## What's my first job? Learn how to program!

Here is a Fortran program statement:

Fortran1: Fortran for beginners. This is friendly introduction to Fortran and will guide you from **writing your first program** through to using more advanced data-types, such as **arrays**. Along the way, you will encounter Fortran's **intrinsic data types**, logic such as **conditionals** and **loops**, program structure and **subroutines** all the while providing pointers to **good style** and **bug avoidance** techniques.