How do ice cores show climate change?

Ice cores show climate change by trapping ancient air bubbles and particles, revealing past atmospheric conditions and temperatures.

Ice cores are cylindrical samples drilled from ice sheets or glaciers, often in polar regions like Antarctica and Greenland. These cores contain layers of ice that have accumulated over thousands to hundreds of thousands of years. Each layer represents a year or even a season of snowfall, much like the rings of a tree. By examining these layers, scientists can gather a wealth of information about past climates.

One of the most important features of ice cores is the tiny air bubbles trapped within the ice. These bubbles contain samples of the Earth's atmosphere from the time the ice formed. By analysing the gases in these bubbles, particularly carbon dioxide (CO₂) and methane (CH₄), scientists can determine the concentration of greenhouse gases in the past. Higher levels of these gases are associated with warmer periods, while lower levels correspond to colder periods.

In addition to gases, ice cores also contain particles like dust, ash, and pollen. These particles can provide clues about past environmental conditions. For example, higher levels of volcanic ash in a particular layer might indicate a volcanic eruption, which could have influenced the climate by blocking sunlight and cooling the Earth. Similarly, the presence of certain types of pollen can reveal information about past vegetation and, by extension, climate conditions.

Scientists also measure the isotopic composition of the water molecules in the ice. The ratio of heavy to light oxygen isotopes (Oxygen-18 to Oxygen-16) can indicate past temperatures. During colder periods, the ice contains less Oxygen-18, while warmer periods have more. By studying these isotopic ratios, researchers can reconstruct temperature changes over time.

Overall, ice cores provide a detailed and continuous record of past climates, helping scientists understand how the Earth's climate has changed and how it might change in the future.