Climate Analysis

Once students understand how glaciers store ice that can be thousands or millions of years old, they examine how glaciers store a record of past climate changes in their ice. Scientists use glacial ice core stratifications to analyze Earth’s past climate changes, and have learned that Earth has experienced at least five ice ages since it first formed.

• Glaciers hold clues to Earth’s past climate.
• Ice cores are like a weather report over hundreds or thousands of years, providing scientists with information about Earth’s changing temperature, climate, atmosphere, and biological activity.
• Earth’s climate has not always been the same as it is now. Scientists believe we are currently living in the warm period of Earth’s fifth ice age, which began about 10,000 years ago.
• Ice ages occur when Earth’s average temperature decreases, which is related to how the sun’s energy reaches Earth.
• The position of Earth relative to the sun is believed to be the most important factor in influencing climate because it causes uneven heating of the planet.
• Climate is very complex because it is affected by many different things. There are different possible causes for Earth’s dramatic changes in climate throughout the planet’s history.

• How can glacial ice provide scientists with information about past changes to Earth’s climate?
• Why do scientists think we are currently living within a warm period of an ice age?
• What would likely happen to the distribution of water on Earth during the coldest part of an ice age?
• How would you explain the relationship between Earth’s tilt, its curved shape, and the general climate in Antarctica?
• How can scientists use ice cores to determine different seasons, as well as the length of a climate period?
• What are some longer-term causes of Earth’s climate changing in the past?
• Why do scientists believe the climate changes we are seeing today are a direct result of human activities?
• How would you explain the relationship between Earth’s temperature, glaciers, and ocean levels to analyze one effect of a changing climate on people?

Misconception: The Ice Age happened in the past.

Fact: We are currently in a warmer period within an ice age, and Earth has experienced multiple ice ages since it first formed.

Climate : the average weather in a location over 30 years or more

Ice age : a global climate marked by long periods of cold temperatures that cause glacial formation and expansion

Ice Core : cylinder of ice drilled out of glaciers that contains layers of snow, dust, volcanic ash, atmospheric gasses, and microbes from past time periods

Weather : the conditions of the atmosphere (temperature, humidity, wind speed, air pressure, and precipitation) at a particular place and time

Storing Ice

The National Ice Core Laboratory in Colorado is not your typical science laboratory. Scientists inside the lab wear ski parkas, insulated gloves, and boots as they work. They need to dress warmly because the lab is kept at -23 degrees Celsius (-10 degrees Fahrenheit).

And the sound of saws buzzing is a common sound. This is because scientists measure and cut pieces of Antarctic glacier ice from massive ice cores stored in the laboratory. An ice core is a cylinder of ice drilled out of glaciers that contains layers of snow, dust, volcanic ash, atmospheric gasses, and microbes from past time periods.

Scientists from all over the country come to the National Ice Core Laboratory to study pieces of ice cores that are stored there. The laboratory holds ice cores from glaciers around the world. For example, one project includes ice cores from a giant, ancient Antarctic ice sheet that is more than 70,000 years old. A team of scientists traveled to Antarctica to drill the ice cores, and then sent them back to the laboratory.

Ice cores are important for scientists who want to learn about Earth’s changing climate. Climate is the average weather in a location over 30 years or more. Weather is the conditions of the atmosphere (temperature, humidity, wind speed, and precipitation) at a particular place and time. Dust, volcanic ash, air bubbles, and sediment trapped in glacial ice can reveal information about the climate on Earth at the time they were trapped in ice.

An Icy ‘Weather Report’

Scientists believe that Earth is 4.5 billion years old. During Earth’s history, the planet has been without glaciers longer that it has been with glaciers. Glaciers only form when the planet does not receive enough solar energy for snowfall to completely melt over the summer.

Scientists use scientific instruments to read ice cores like a weather report that includes weather data from year to year, going back hundreds or thousands of years. This is possible because ice cores contain evidence of past changes. Air bubbles contain atmospheric gasses from hundreds or thousands of years ago. Volcanic ash reveals volcanic activity. The composition of the snow in a particular layer can reveal the temperature.

Scientists can also look for patterns in the ice cores. Summer layers in an ice core are lighter than winter layers. Thicker bands indicate a longer climate period, while narrower bands indicate a shorter climate period. Warmer temperatures are often followed by increased biological activity because living things need a certain temperature to survive.

Because of ice cores, scientists know that in Earth’s history, there have been several ice ages—global climates marked by long periods of cold temperatures that cause glacial formation and expansion. Glaciers expand during the cold periods of an ice age. At the height of the last cold period, about 100,000 years ago, glaciers reached down to the city of Chicago and up to the middle of South America. This last cold period was called the Great Ice Age.

Scientists believe we are currently living in the warm period of Earth’s fifth ice age, which began about 10,000 years ago. It is a warm period because glaciers are present but retreating. There are complex variables that influence the climate at any given time and can cause it to change. For example, sudden events such as a volcanic eruption or a forest fire can impact the climate. Volcanic eruptions send ash particles into the environment, blocking sunlight from reaching Earth’s surface. This contributes to Earth’s cooling. However, volcanoes also release carbon dioxide, which causes warming over millions of years because it traps thermal energy from the sun. For this reason, carbon dioxide, along with water vapor and methane are called greenhouse gasses.

Forest fires release carbon dioxide into the atmosphere. But if a forest re- grows after the fire, the trees and other plants will remove about the same amount of carbon dioxide as was released into the environment during the burning.

Other changes can be more long-term. For example, the path of Earth’s orbit around the sun has changed over time, as has the way Earth tilts toward the sun. Both of these factors influence how much thermal energy from the sun Earth absorbs, which in turn affects Earth’s temperature and climate.

In this lesson, students create glacial ice core stratification models to investigate how ice cores form and how scientists use them to analyze climate data. Students use their observations to explain how ice core samples are extracted from ice sheets and how the ice layers can provide evidence of past climate events (volcanic eruptions, warm periods, cold periods, etc.).