Determine the melting point of tropical glaciers in the last ice age

In a Dartmouth study in Hanover, New Hampshire, USA, tropical glaciers in Africa and South America began to melt in the last ice age about 20,000 years ago.

The discovery of glacial retreat in the global tropics makes it clear how low latitudes change in one of the world's most extreme climate change events and can help predict about our climate future today.

The study, published in the journal Science Advances , supports the general scientific consensus on the role of carbon dioxide in causing global climate change, but adds complexity to understanding the system. Earth's climate and how quickly the ice age ends. This result also increased the understanding of the glacier melting sequence between the tropics and the polar regions at the time.

The glaciers in the Rwenzori mountain range confirm one of the most extreme climate change events on earth and can help predict our future climate today.

Associate Professor Meredith Kelly, Department of Earth Sciences at Dartmouth, and senior researcher in this study said: " Carbon dioxide is the cause of the Earth's escape from the last ice age. But there are also processes. Getting started before the carbon dioxide rise is also an important contributor to the end of the ice age, and that's what we want to learn about.

According to Dartmouth University research, glaciers in tropical Africa and South America reached their maximum levels about 29,000-21,000 years ago and then began to melt. This regression earlier than the significant increase in atmospheric carbon dioxide was recorded about 18,200 years ago.

These findings show a trend of increasing tropical temperatures across the planet and suggest that warming may have been caused by a difference in heat difference between polar and tropical regions.

At the end of the last Arctic ice age, small changes in the Earth's orbit made more solar radiation and warmer temperatures, causing melting of the ice sheets in the northern part. bridge. In Antarctica, changing the planet's tilt angle to the sun makes the summer longer. The decrease in temperature slope between the polar and tropical regions slows the temperature movement out of the low latitudes to the north and south poles, making the tropics warmer and resulting in glaciers. in this area disappears faster.

Once changes in ocean and atmospheric circulation patterns and the increase in carbon dioxide take place, the planet seems to be caught in an overheated spiral that melts near polar poles and eliminates ice. remove glaciers in the tropics.

"Only a few thousand years can make all the difference in our understanding of past and present climate change events , " said Margaret Jackson, who was the lead author of the study. while being a PhD student at Dartmouth said. "This study shows that glaciers responded to warming even before the thawing increased while carbon dioxide pushed the planet to the edge to end the last ice age."

Dartmouth research recalculates previously defined data taken from locations across tropical South America and extends findings to tropical East Africa to prove that river loss ice during this period was a tropical phenomenon.

"From our previous work, we knew that the tropical glaciers in South America may have retreated early, but we don't know how this phenomenon expanded. The Rwenzori Mountains has been identified as a laboratory." The perfect outdoors to confirm the time of climate change in the tropics in the past , " Jackson said.

While ice cores collected from the tropics are available to researchers, the interpretation of past climate information from them can be complicated. Because the tropics are far away from direct cooling of high latitude ice sheets, this area can be used to better understand global temperatures during the last ice age and help provide Clues on how the Earth's temperature changes over time.

The study also helps researchers understand how temperature gradient, greenhouse gas, atmospheric circulation and ocean circulation all work together to make the planet "flip" between the cold and warm periods.

"Today, the planet is entering a new kind of climate unprecedented for millions of years," Mr. Kelly said. "Models of past change events can help us predict the future and our fuller understanding of the tropics as a key piece of the puzzle."