Hidden Water

Most of the changes scientists see on our planet are either visible to the naked eye or directly measurable.  But changes to our water systems are among the most difficult to see.  In this episode, we travel from the Antarctic ice sheet capturing over 60 percent of all freshwater on Earth, to massive groundwater aquifers that remain particularly elusive, to a freshwater system that acts as the primary economic, cultural, and environmental driver of southern Asia.  In short, we go in search of hidden water.

This episode was produced by Leslie Chang, Mike Osborne, and Miles Traer.
Additional music by Kevin MacLeod (License available here)


by Miles Traer

The Anthropocene is defined by a number of planetary transformations that we can either see with the naked eye or directly measure.  We quantify acres of grassland or forest cleared for agriculture.  We count the number of people inhabiting our megacities.  And we sample the air to determine parts per million of carbon dioxide and other greenhouse gases.  But not all changes to our planet are as easily measured or understood.  Changes to our water system are among the most difficult to capture in our new geologic age.

The Antarctic ice sheet, by far the largest in the world, currently holds over 60 percent of all the freshwater on Earth.  It occupies an area the size of the United States and Mexico combined.  And due to climate change, it’s melting.  While we’re in no danger of a Waterworld-style planet any time in the future, Antarctica will still dominate sealevel rise depending on how much and how quickly the ice melts.

Jenny Suckale is a Stanford geophysicist who studies the physics of melting ice in Antarctica.  Understanding the process by which the ice sheet melts is key for any projections of sealevel rise.  After studying the Antarctic ice sheet, Suckale came to a surprising conclusion.

“One of the things that I realized is that the mechanism through which Antarctica is melting is not what we expected it to be.  So we really don’t know how Antarctica is melting,” Suckale says.

It’s tempting to think that an ice sheet melts like a giant ice cube.  The surface of the ice warms up and the ice cube gets smaller and smaller as the ice on the outside of the cube melts.  But that’s not how Antarctica is melting.  Antarctica seems to be melting from the inside out as ice is transported by enormous ice streams from the center of the continent to the coast, explains Suckale.

In this episode, Suckale takes us to these ice streams as we try to understand their physics to better project sea level rise in the future.

We then travel from Antarctica to deep underground as Stanford groundwater researcher Rosemary Knight tries to visualize our depleting aquifers.  Throughout the western US, extreme drought conditions have placed tremendous pressure on groundwater managers to draw more and more water from aquifers to replace the water usually drawn from surface streams and reservoirs.  But, as Knight points out, we don’t have a very good picture of how much water is down there to begin with.

“We need to advance the use of earth imaging methods so that earth imaging can play the same critical role in ensuring the health of our ground water systems that medical imaging plays in ensuring human health,” says Knight.

To look hundreds of feet below ground, Knight and her colleagues actually fly hundreds of miles up and look back down from orbiting satellites.  How does this work?  Knight walks us through the amazing space technology that allows her to sneak a peek below ground and into our aquifers.

Finally, we return to the surface to speak with climate researcher Kaustubh Thirumulai, who recently returned from a massive research expedition called the International Ocean Discovery Program.  As part of the program, Kau and other scientists collected rocks and sediment from the seafloor to get a better idea of how climate change is affecting the South Asia monsoon – the primary fresh water delivery system for the Indian subcontinent.