The Arctic has not been so warm for 3 million years | Earth

An ice floe drifting in Svalbard, Norway. Image via Sven-Erik Arndt/Arterra/Universal Images Group/ Getty images

to Julie Brigham-Gret, University of Massachusetts Amherst and Steve fetch, University of Massachusetts Amherst

Each year, sea ice in the Arctic Ocean shrinks to a low in mid-September. This year, it is only 3.44 million square miles (3.7 million square kilometers). Second lowest value Today, 42 years after satellites began measuring, ice is 50% of the area 40 years ago In late summer.

This year’s minimum ice coverage is the lowest in a 42-year-old satellite record excluding 2012, reinforcing the long-term downward trend in the Arctic ice cover. Summer sea ice has declined on average over the past 40 years. Image via NSIDC/ Conversation

As the intergovernmental panel on climate change shows, the level of carbon dioxide in the atmosphere Higher than ever in human history. Finally, when the CO2 concentration in the atmosphere reaches today’s level About 412ppm – It was 3 million years ago. During the Pliocene Epoch. That said, the Arctic has not been so warm for 3 million years.

As a researching earth scientist Earth’s climate evolution and How to create life conditions, We see the changing conditions in the Arctic as an indicator of how climate change can change the planet. Continued increase in global greenhouse gas emissions could bring the planet back to the Pliocene state, where sea levels are higher, weather patterns change, and conditions have changed in both places. Natural world and Human society.

Pliocene Arctic

We are part of a team of scientists who analyzed the sediment core. El Giggin Lake In 2013, in northeastern Russia, we understood the Arctic climate with high levels of atmospheric carbon dioxide. Fossil pollen preserved in this nucleus shows that Pliocene Arctic is very different from its current state.

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Today the Arctic is a treeless plain and Tundra plants, Such as grass, sedge and some flowering plants. In contrast, the Russian sedimentary nucleus Pollen from trees such as larch, spruce, fir and hemlock. this is Boreal forestToday, it reached the Arctic Ocean across most of Arctic Russia and North America, ending hundreds of miles further south and west of the Arctic Circle in Russia and Alaska today.

The Arctic was much warmer in Pliocene, so the Greenland Ice Sheet did not exist. The small glacier along the mountainous eastern coast of Greenland was one of the few places in the Arctic with ice all year round. On Earth Pliocene there was ice only at one end of Antarctica, and that ice Less broad and more susceptible to melting.

Northern forest near Lake Baikal in Russia. Three million years ago, this forest extended hundreds of miles northward than it reaches today. Through the image Christophe Meneboeuf/Wikipedia

Because the seas were warmer and there were no large ice sheets in the northern hemisphere, sea levels were 9 to 15 meters higher worldwide than today. The coastline was inland, far from its current location. Today, California’s Central Valley, the Florida Peninsula, and the Gulf Coast region were all underwater. The same was true of the land where major coastal cities such as New York, Miami, Los Angeles, Houston and Seattle stood.

Winters in the western United States are now warmer. It supplies a lot of water in this area.. Today’s Midwest and the Great Plains are much warmer and drier to grow corn or wheat there would have been impossible.

Why was there so much CO2 in Pliocene?

How did the CO2 concentration during Pliocene reach levels similar to today? Humans will not appear on Earth for at least a million years, and our fossil fuel use is much more recent. The answer is that some natural processes on Earth release CO2 into the atmosphere, while others consume it. The main system that balances these dynamics and controls the Earth’s climate are natural Earth thermostats controlled by rocks. Chemically reacts with CO2 Take it out of the atmosphere.

The greenhouse effect increases surface temperature and in some areas rainfall. Together, these accelerate silicate rock weathering. Faster weathering removes more CO2 from the atmosphere (yellow arrow). The intensity of the greenhouse effect depends on the atmospheric CO2 level. Image via Gretashum/Wikipedia/ Conversation

Certain rocks in the soil are constantly broken down into new substances in reactions that consume CO2. These reactions tend to accelerate when temperatures and rainfall are higher. It exactly matches the climatic conditions that arise when the concentration of greenhouse gases in the atmosphere rises.

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But this thermostat has built-in control. As CO2 and temperature rise and rock weathering accelerates, it draws more CO2 from the atmosphere. When CO2 starts to drop, temperatures cool down, rock weathering slows globally and emits less CO2.

Rock weathering reactions can work faster even where the soil contains a lot of newly exposed mineral surfaces. For example, it includes areas of heavy erosion or periods when Earth’s crust processes push the ground upwards, creating a major mountain range with a steep slope.

Rock weathering thermostats operate at a geologically slow rate. For example, at the end of the dinosaur era about 65 million years ago, scientists estimate that atmospheric CO2 levels are between 2,000 and 4,000 ppm. It took over 50 million years to naturally reduce to about 400 ppm in Pliocene.

As natural changes in CO2 levels occurred very slowly, periodic changes in the global climate system were also very slow. Ecosystems have taken millions of years to adapt, adjust and respond slowly to changing climates.

Summer heatwaves transform northern Siberia, melt permafrost and create conditions for massive wildfires.

Future like Pliocene?

Human activity today overwhelms the natural process of releasing carbon dioxide from the atmosphere. At the dawn of the industrial era in 1750, atmospheric CO2 is about 280ppm. It took only 200 years for humans to completely reverse the orbit that started 50 million years ago and return the Earth to levels of CO2 that have not been experienced in millions of years.

Most of these changes have occurred since World War II. Currently, 2-3 ppm annual increases are common. In response, the planet is warming at a rapid pace. Since about 1880 the Earth has 2 degrees Fahrenheit (1 degree Celsius) – Many times faster than any warming event in the last 65 million years of Earth’s history.

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In the Arctic, this warming was amplified to 9F (+5C) due to the loss of reflected snow and ice. As a result, the Arctic sea ice range in summer is getting lower. Scientists say that the north pole No ice at all in summer Within the next 20 years

This is not the only evidence of extreme arctic warming. Scientists Dissolution rate in extreme summer Across the Greenland Ice Sheet. In early August, on the territory of Nunavut, Canada’s last remaining ice shelf Fell into the sea. ~ once Arctic siberia and SvalbardThe group of Norwegian islands in the Arctic Ocean has reached record highs this summer.

When this planet returns to the Pliocene CO2 world, the water supply of coastal cities, agricultural crater areas and many communities will all be radically different. This future is not inevitable. However, to avoid this, big steps are needed to reduce the use of fossil fuels and lower the global thermostat.

Julie Brigham-Gret, Professor of Earth Science, University of Massachusetts Amherst and Steve fetch, Associate Professor of Earth Science, University of Massachusetts Amherst

This article has been republished at: Conversation Under Creative Commons license. read Original article.

Bottom Line: The Arctic has not been so warm for 3 million years. These geoscientists discuss what’s going on in the Arctic and how it will affect the rest of the world.


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