Antarctic glaciers record millions of years of Earth’s climate change and atmospheric composition, and analyzing them is crucial to understanding past environments and developing responses to the current climate crisis.
Antarctic glaciers vividly preserve fundamental data on past changes in Earth’s atmospheric composition and temperature. They contain millions of years of Earth’s history in layers, acting as a time capsule for scientists. Each layer of the glacier records atmospheric and climatic conditions at the time of the snowfall, providing essential data for studying global environmental change. By analyzing glaciers, scientists are gaining important information about global warming and other issues facing the planet. In particular, analyzing past atmospheric composition is helping us understand current climate change and improving the accuracy of future prediction models.
The snow on the surface of Antarctica is buried deeper and deeper as it is covered by the ongoing snowfall, and the density of the snow gradually increases. At a certain depth, the pressure exerted by the snow on top causes the snow below to transform into ice. The air between the snow particles becomes trapped in the ice, and as the ice thickens and the pressure exerted by the ice above increases, clathrate hydrate is formed. Clathrate hydrates are crystals that contain small molecular weight gases such as methane, carbon dioxide, and nitrogen in the voids created by the bonding of water molecules under conditions of high pressure and low temperature. The bubbles in these crystals have the same gas composition as the atmosphere at the time. When the ice containing the bubbles is drilled and melted, it changes back to its original state, and the gas composition is analyzed using precise instruments such as gas chromatography. This process can reveal the composition and concentration of Earth’s atmosphere in the past, such as carbon dioxide and methane.
Air trapped in glaciers doesn’t just tell us about the composition of the atmosphere, it also provides important clues about the Earth’s ecosystem. For example, changes in the concentration of certain gases can reflect the effects of natural disasters such as changes in vegetation, volcanic eruptions, or large forest fires. As such, glaciers contain a comprehensive record of the global environment at that time.
However, the atmospheric composition of air bubbles in glacial ice can only tell us so much about the temperature at that time. A common way to investigate past temperatures is to look at the isotopic composition of the oxygen or hydrogen in the water molecules that make up glaciers. Isotopes are elements with the same atomic number but different atomic weights, such as oxygen (16O), which has an atomic weight of 16, and oxygen (18O), which has an atomic weight of 18. The oxygen isotope consumption (18O/16O) of water molecules in Antarctic glaciers increases or decreases in response to changes in temperature at the time of snowfall, with a distinct difference between summer and winter, and a yearly cycle. Today’s experiments show that the increase or decrease in oxygen isotope consumption is almost directly proportional to temperature change. This relationship can be applied to determine the temperature at the time the glaciers were formed.
Recent studies of glaciers have shown that not only isotopic consumption of oxygen, but also changes in the concentration of carbon dioxide or methane are closely related to temperature changes. For example, changes in the concentrations of carbon dioxide and methane found through glacier drilling clearly reveal the impact of fluctuations in atmospheric greenhouse gas concentrations on temperature. Increasing concentrations of these gases have been found to increase temperatures, and conversely, decreasing concentrations have been found to decrease temperatures. Compared to the historical variations in carbon dioxide and methane concentrations that we know from glaciers, today’s concentrations are showing a worrying upward trend. This is an important piece of evidence that makes us more aware of the impact of human activity on climate change in the modern world. Based on these data, scientists are warning that we need to take urgent action to address the current climate crisis.
