The Building Blocks of Our Climate

Did you know the oceans hold more heat than the atmosphere? As climate change worsens, understanding our water will be critical.

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We know the equations that describe how water moves, but applying them to bodies of water as vast as the Earth’s oceans makes them difficult to solve, especially when the goal is to predict how they might change over many years. Our oceans are not only large and deep, they also interact with the atmosphere, with land, and with the sea ice above it. All of this adds to the complexity.

These are questions that fascinate oceanographer and mathematician Francis Poulin, professor of applied mathematics and Earth science at the University of Waterloo. He uses computers to try to solve the math that could predict the future movement of our oceans.

For instance, take the Gulf Stream: a swift and warm ocean current that brings warm water from the Gulf of Mexico across the Atlantic Ocean towards Europe. Not only does this help keep European climate warm, it also acts like a conveyor belt that helps animals and other marine life move through the ocean. Although not yet well understood, the effects of climate change put the Gulf Stream and other stable ocean currents at risk.

The Gulf Stream is important to climate and biology, but this swift and warm ocean current is threatened by climate change. Video courtesy of Kurzgesagt.

The Gulf Stream meanders and forms vortices that can span upwards of 200 kilometers, and can persist for years. Poulin wants to know how these major ocean movements form, and how they will behave over time. The ocean also holds far more heat than the atmosphere, making it an important player in the Earth’s climate, says Poulin.

One way to get more information is to break the ocean up into smaller and smaller blocks, giving more detail into what is happening on a more local scale.

“I think it’s trying to understand the basic physical questions of why are things the way that they are,” Poulin explains. “It’s really hard to understand these big ocean models that people are using to understand how things are changing in the oceans and the atmosphere if we don’t have a solid understanding of the little blocks that put these things together.”

This is only possible with more computing power, which limits how fine the grid can be. Poulin also simplifies the mathematical models, and tries to understand when these simplifications work, and also when they fail.

Poulin’s combination of mathematical models, lab experiments, and real ocean observations improve our understanding of how various actions and changes impact our oceans. This also helps put into perspective exactly what’s at stake.

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Francis Poulin is an associate professor in the Department of Applied Mathematics, and cross appointed to the Department of Earth and Environmental Sciences at the University of Waterloo. He studies the oceans, which cover two thirds of the world’s surface and act as a reservoir to store heat. They are forced at planetary scales on the order of 1,000,000 metres (examples are heating by the sun and tides generated by the moon) but the dissipation occurs at scales of 0.000001 metres. In this vast range of length scales there are many interesting dynamical processes that contribute to the transfer of energy down from the planetary scales to the micro-scales.

Understanding all of these together is an impossible task even with the world’s most powerful computers. However, Poulin approaches this problem with idealized process studies to unravel some of nature’s secrets and then piece together the different components to better comprehend what occurs in the oceans. These scientific questions are of great interest in their own right but also play an important role in understanding the ocean’s role in climate and in general how it exchanges properties with the atmosphere.