Glaciology

Glaciology is the study of the formation and movement of glaciers and their response to climate change. It includes studying the past positions of glacial ice, monitoring changes in present-day ice, and forecasting the future behavior of the world’s glaciers and ice sheets. Because glaciers respond directly to changes in air temperature, they are one of the key indicators of climate change on the planet. Understanding the behavior of glaciers is important to understanding the effects of climate change. Although climate change is a central focus of glaciology, this discipline also incorporates aspects of geophysics, geology, climatology, hydrology, and geomorphology.

Glaciers as Tools to Reconstruct the Past The landscapes left behind by retreating glaciers can be valuable tools for glaciologists to reconstruct the past positions and characteristics of glacial ice. End moraines, for example, are formed when sediment that is eroded and transported by glacial ice is deposited at the front of the glacier in piles of rock and soil. These moraines usually mark the maximum extent of the glacial terminus, or snout. Often, glacial valleys contain numerous sets of end moraines that correspond to either the last ice age or smaller, more recent advances, such as the Little Ice Age that ended in the mid-1800s. Wood that is buried in these moraines can be carbon dated to help scientists determine the age of these landforms.

Glaciers also retain evidence of past climates within layers of accumulated ice. Because snow in the accumulation zone is progressively buried, glacial ice is older toward the bed of the glacier. Glaciologists drill cores through glaciers and ice sheets to sample ice of different ages. They measure the ratios of the isotopes of oxygen and hydrogen in the ice to gain information about past atmospheric temperatures. They also extract ancient air that is trapped in small bubbles deep within the ice. This can tell scientists about concentrations of greenhouse gases, such as carbon dioxide, in past climates. The levels of methane also reveal information about the level of biological productivity in the past, while traces of sulfur are indications of volcanic activity. If the time of the eruptions is known, these layers of volcanic material can be used to help date ice cores.

The oldest ice exists deep within polar ice sheets, and many ice cores have been drilled in Antarctica and Greenland. The Vostok ice core from central Antarctica, for example, dates back more than half a million years and has provided a wealth of information about past atmospheric conditions. Ice cores from alpine glaciers in the world’s major mountain ranges are not as old because this ice tends to flow more quickly and is much shallower than ice in polar ice sheets. 

These cores however, have provided glaciologists with a wealth of information about past climate change at lower latitudes (closer to the equator). This information is invaluable because it provides proxy climate records for many centuries prior to the first recorded measurements of atmospheric conditions.