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La Niña could become the Australian norm

climate change deceleration A conveyor belt of ocean currents that carries warm water from the tropics to the North Atlantic.

our researchpublished today nature climate changenotes that a complete collapse of this Atlantic conveyor would have severe consequences for global climate.

The collapse of this system, called the Atlantic Meridional Reversal Circulation, could make the Earth’s climate more La Niñastate of yours. This means more flooding in eastern Australia and a worsening drought and wildfire season in the southwestern United States.

East Coast Australians know what a relentless La Niña looks like. Climate change has brought moist air to our atmosphere, Two Summers of La Niña warmed the seas north of Australia. Both caused record-breaking floods in New South Wales and Queensland, bringing wet conditions never experienced before.

On the other hand, in southwestern North America, Record drought and severe wildfires The 2021 fires alone will put a huge strain on emergency services and agriculture. It is estimated to have cost at least $70 billion (USD).

The Earth’s climate is dynamic, variable, and constantly changing. But the current trajectory of declining greenhouse gas emissions is giving the whole system a huge kick with uncertain outcomes. As a result, textbook explanations of the Earth’s ocean circulation and its effects will be rewritten.

What is the Atlantic that turns the meridional circulation upside down?

The Atlantic Overturning Circulation consists of a large flow of warm tropical waters into the North Atlantic, giving the tropics a chance to lose excess heat while keeping Europe’s climate mild. Comparable capsize in Antarctic waters It is found in the Southern Hemisphere.

climate record Going back 120,000 years ago, it became clear that the Atlantic circulation turned off or slowed down dramatically during the Ice Age. During so-called ‘interglacials’, when the global climate becomes warmer, European climates switch on and soothe.

Atlantic overthrows have been relatively stable since human civilization began about 5,000 years ago. but, Deceleration of past decades detectedand this worries scientists.

What is the reason for the slowdown? One of the obvious consequences of global warming is the melting of the polar ice caps of Greenland and Antarctica. As these ice caps melt, they release large amounts of freshwater into the ocean, making the water more buoyant and reducing subsidence of dense water at high latitudes.

Around Greenland alone, huge 5 trillion tons The amount of ice that has melted in the last 20 years. That’s the equivalent of 10,000 Sydney harbors of fresh water. This melt rate is set to increase over the next few decades if global warming continues.

Disruption of the overlying circulation of the North Atlantic and Antarctic would greatly alter the structure of the world’s oceans. It makes them fresher at depth, depriving them of oxygen and starving the upper oceans from the upwelling of nutrients provided when the deep sea resurfaces from deep water.

Melting of Greenland’s ice is already underway, scientists estimate the Atlantic Ocean is upside down Weakest for at least the last 1000 yearsthere are projections of a future collapse in the next few centuries if greenhouse gas emissions are not curbed.

Deceleration effect

in our research, used a comprehensive global-scale model to examine what the Earth’s climate would look like under such a collapse. We turned off Atlantic overthrow by applying a large meltwater anomaly to the North Atlantic and compared this to a comparable run without applying meltwater.

Our focus was to see how the Earth’s climate changes in remote areas as far as Antarctica, beyond the well-known regional influences around Europe and North America.

The model’s simulations first revealed that if the Atlantic Ocean did not turn over, it would accumulate a large amount of heat just south of the equator.

This excess tropical Atlantic heat pushes warmer, moist air into the upper troposphere (about 10 kilometers into the atmosphere) and causes dry air to descend into the eastern Pacific.

The downdraft strengthens the trade winds and pushes warm water towards the Indonesian sea. And this will help bring the tropical Pacific into La Niña-like conditions.

Australians may think of La Niña summers as cool and wet. But under the long-term warming trend of climate change, their worst impact will be flooding, especially in the east.

It also shows that the upending shutdown of the Atlantic Ocean can be felt as far south as Antarctica. Warm air rising over the western Pacific causes wind changes that propagate to Antarctica. This could deepen the Amundsen Sea low-pressure system west of Antarctica.

This low pressure system is known to affect Ice sheets and ice shelves meltNot only that, ocean circulation and sea ice extend westward to the Ross Sea.

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Never in Earth’s history, aside from giant meteorites and giant volcanoes, has our climate system been perturbed by changes in atmospheric gas composition that are imposed today by the constant burning of fossil fuels.

The oceans are the flywheels of Earth’s climate, slowing the pace of change by absorbing large amounts of heat and carbon. But there are payoffs, including sea-level rise, ice melt, and a significant slowdown in Atlantic circulation projected for the rest of the century.

We now know that this slowdown will affect not only the North Atlantic region, but also as far afield as Australia and Antarctica.

Growing a new low-carbon economy can prevent these changes. In doing so, for his second time in less than a century, the course of Earth’s climate history will change. For the better this time.

Matthew England Professor of Science and Deputy Director, ARC Australian Center for Antarctic Science and Research (ACEAS).

Andrea S. Taschet He is Associate Professor at the Climate Change Research Center (CCRC) at the University of New South Wales (UNSW) and Principal Scientist at the Australian Research Council (ARC) Center of Excellence for Climate Extremes.

briam orihuela pinto PhD Candidate at the University of New South Wales.

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La Niña could become the Australian norm

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