Climate change: Now in high resolution

To truly understand how something works, you need to take it apart and examine each component.

This is why Dr Andy Hogg from the ANU Research School of Earth Science has cut up the ocean into 500 million pieces.

Dr Hogg is part of a national team of collaborators who are studying ocean models to better understand the rate and scale of climate change.

Based on observations from the Southern Ocean, one of the world’s most important—yet least studied—oceans, Dr Hogg has used complex equations, satellite observations, and the largest supercomputer in the southern hemisphere to devise a new, more detailed ocean model.

Ocean models consist of virtually ‘cutting’ the ocean into small pieces or grid squares, then solving mathematical and physical equations for what is believed to happen in each little square. By then piecing this information together as whole, we get a fully-formed idea of the circulation of the ocean, and how it is responding to climate change.

The ‘pieces’ involved in Dr Hogg’s model are roughly 500 million grid points, requiring the computational equivalent of 5000 laptop cores to compute. (Don’t try that at home, unless your home is the National Computational Infrastructure, home to Australia’s most powerful supercomputer.)

“This model is at pretty much the highest resolution global model that anyone is using in Australia,” says Dr Hogg.

Dr Hogg’s collection of high-res puzzle pieces is providing answers to a critically important question in the study of climate change. And the answers are blowing in the wind.   

“Over the last 30 to 40 years, the winds in the Southern Ocean have increased substantially,” Dr Hogg explains. “And we think this is partly the effect of the ozone hole forming in the southern hemisphere, and partly the effect of global warming.”

“Now we have finally been able to use observations and models together to understand some of the impacts that those changing winds have had on the ocean.”

One impact is that increasing wind speeds over the Southern Ocean are putting more energy into the system. This energy quickly becomes turbulence, or little water vortices called ‘eddies’.

Eddies are important for more than being the most endearingly-named aspect of the ocean system.

They are responsible for the transport of nutrients, heat, and carbon dioxide (stored in deep layers of the ocean) to far-reaching parts of the ecosystem.

We know that the Southern Ocean is eddy-rich and, theoretically, as rising wind speeds cause the eddies to increase in strength, they transport faster and have a more rapid impact on the oceanic ecosystem and the global climate.

A detailed understanding of eddies, and the way they behave in the Southern Ocean in particular, has important implications. This information contributes to weather forecasting, mapping fuel-efficient shipping routes (knowing which way is downstream), and our understanding of the potential pathways of nutrients, important when applied to oil-spills and pollution from flooding.

In the long term, being able to predict the behaviour of eddies may also allow us to get an accurate picture of how quickly heat is being carried to Antarctica, and consequently, the rate at which sea levels are rising.

But when it comes to fixing that sea-level rise, it’s only the behaviour of another kind of Eddy—all the humans with that name, not to mention the rest of us—which can offer a solution, and not in high-res, but in real-life.

Image courtesy of Wayne Butterworth on Flickr