Evidence of Recent Change

Some regions that usually receive snow are receiving less snowfall and do not have as much snow on the ground. Glaciers in the United States and around the world have generally shrunk, and the rate at which they are melting appears to have accelerated over the last decade. Additionally, the amount of ice in the Arctic Ocean has decreased, and many lakes are freezing later in the fall and melting earlier in the spring. Although the natural variability of this complex system is large, the direction of change is clear and the rate of change has taken scientists by surprise. —Environmental Protection Agency

In this lab, you will explore evidence of recent change in the cryosphere. In Part A, you will use an online interactive to visually explore how six Alaskan glaciers have changed over the last hundred years. You will also use image processing software to measure how much area a glacier in the Himalayas has lost over time due to rising temperatures. In Part B, you will study recent trends in Arctic sea ice extent. In Part C, you will explore the ice-albedo feedback effect and think about causal connections between climate and the cryosphere.

After completing this investigation, you should be able to:

• describe evidence of recent changes observed in glacial ice;
• measure changes in glacial area and extent using ImageJ;
• describe recent trends in sea ice extent;
• explain how the ice-albedo feedback loop works; and
• explain the difference between positive and negative feedback mechanisms.

Keeping track of What You Learn

In these pages, you'll find two kinds of questions.

• Checking In questions are intended to keep you focused on key concepts. They allow you to check if the material is making sense. These questions are often accompanied by hints or answers to let you know if you are on the right track.
• Stop and Think questions are intended to help your teacher assess your understanding of the key concepts and skills. These questions require you to pull some concepts together or apply your knowledge in a new situation.