enlarge picture Jang Chae-won, a researcher at the Polar Research Institute
Last month, I received an email from the research center telling me about a treasure hunt as part of the department’s sports festival. Reading the email brought back memories of treasure hunting as a child. With a map of the park in hand, I looked for pieces of paper with numbers written on them, with just one clue that there were hidden treasures throughout the park. Don’t know if a smaller number is better or a bigger number is better.
An exciting treasure hunt is also underway in Antarctica. It’s called ‘1.5 million year old glaciers discovered in Antarctica.’ This research is an important scientific challenge to solve the mysteries of climate change. To date, 800,000 years of climate data have been restored through Antarctic ice cores. This can be further extended using marine sediment data. Looking at the climate over the past 3 million years reconstructed from Antarctic ice cores and marine sediments, we saw that the climate cycle was as short as about 41,000 years 1.25 million years ago, but changed to a 100,000-year cycle from about 700,000 years ago. .
The sun is the source of energy outside the Earth. These long-term climate variations are related to changes in the Earth’s orbit and axis of rotation. This is because these changes change the amount of energy and the distribution that the Earth receives from the Sun. This is related to the ‘Milankovitch’ circle. The Milankovitch cycle is an important theory that explains the cycles of glacial and interglacial periods.
There are three main factors in the Milankovitch cycle: First, the Earth’s orbit changes periodically between elliptical and circular with a cycle of about 100,000 years. Second, the Earth’s axis of rotation is tilted by about 23.5 degrees, and the axis of rotation goes through a ‘precession’ movement in which the axis of rotation wobbles every 26,000 years. Third, the tilt of the Earth’s axis of rotation changes between about 22.1 degrees and 24.5 degrees every 41,000 years. This astronomical effect resulted in a long-term climate cycle. However, between 1.25 million and 700,000 years ago, the climate cycle changed from 41,000 to 100,000 years. To find out the reason for the cycle variations, research teams from around the world decided to find 1.5 million year old glaciers in Antarctica. Decades of radar studies analyzing the vertical structure of ice sheets have informed scientists that they are likely to find older glaciers in the center and edges of East Antarctica.
At the edge of the ice sheet, there is ‘blue ice’, which has a distinctive blue colour. In general, there is a series of old glaciers at the bottom of the ice sheet and recently snow has accumulated at the top. However, as the glacier moves from the center to the edge by gravity, the old glacier at the bottom is exposed to the surface and takes on a blue color, called new ice.
In general, continuously formed glaciers are found by drilling directly into an ice sheet. When drilling glaciers in areas where there is fresh ice, only glaciers that were formed at a specific time are found. However, there is an advantage in that very old glaciers are easily accessible in large quantities. Recently, American scientists received new ice from Antarctica that is 5 to 6 million years old.
To bring back continuous climate data, we need to go deep into the interior of East Antarctica. To get continuous climate data for 1.5 million years, we need to find a place that is very cold and with little snow cover, so that snow has accumulated over a long period of time and glaciers have formed. Europe, Korea, Japan, China, the United States, and Russia have started a deep glacier drilling project to find the ‘treasure’ of ancient glaciers in Antarctica. Europe is the first country to start drilling, which plans to complete drilling to the target depth in the ‘Little Dome C’ area during this Antarctic summer season (Northern Hemisphere winter season). However, recent research suggests that the age of glaciers in this area may be younger than expected and that they may be less than 1.5 million years old.
Just like you didn’t know the meaning of the numbers written on the paper while you were hunting for treasure, you don’t know how old the glacier you found in Antarctica is until you examine it. Can we find 1.5 million year old glaciers in Antarctica? I wonder which country will win this time. In the center of the Antarctic ice there are still unsolved climate mysteries. I hope that we will learn about the causes of variations in the climate system that we did not know about, and I would like to encourage someone to find this treasure.
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