Scientists study ancient coastlines in order to accurately predict how climate change will affect glacier melt and sea level rise. One recent group of researchers and journalist Daniel Grossman trekked across the Australian outback searching for fossils on land that was covered by water back in the Pliocene era, Earth’s last great warm period. The Pliocene is generally seen as a good indication of how sea level will change due to global warming, since the period was slightly warmer than the Earth today.
We spoke with Grossman to learn about his experience with environmental reporting and glacial melt.
Your book Deep Water details your journey across Australia with several scientists studying the Pliocene era. How did you get involved with that project?
It was a long process. The trip was actually in 2009, so it’s been a little while. Part of the reason why it took that long was because there was a lot to learn after the trip.
I had actually met Maureen Raymo, the lead scientist, a few years before the trip. We got together every once in a while and chatted about climate issues. One day, she told me she was going to Australia, and said she thought it might be interesting for me to come along. We figured out a way where it would be worthwhile for me to do that by getting a grant together from the National Science Foundation, which paid for me to produce some videos about her work.
We’re working on three videos. The first is about the process of finding samples in Australia, called “In the Field.” The second is the process of finding out how old those samples are, called “In the Lab.” And the third one is making sense of it all, once they figure out they have samples from the right age, so it’s more about the theory.
A lot of people probably have a hard time wrapping their minds around sea level rise not being uniformly spread out. Could you explain why water does not rise equally across the globe?
If this planet was only water — a complete round sphere with a layer of water around the planet — that water would be thick. And if you brought a pipe in and added more water, it would get even thicker. Now, if you stick a couple continents on there that are a fixed distance from the center of the planet, the water would go up and down on those shorelines. The land moves up and down with respect to the center of the planet, and the water is also moving up and down.
There are many reasons why the land moves up and down, and those movements happen on many different scales. We know certain parts of the world, like the area around New Orleans, is actually sinking fairly fast. It’s sinking fast because the sediment is compacting, which is brought down by the Mississippi River. Under normal circumstances, that sediment would be replenished by more sediment from the river, but the levees prevent that from happening. In comparison to other parts of the United States, sea level is rising faster there because the land is sinking. If you’re standing on a sinking piece of land, you’ll notice the ocean is rising.
There are parts of the world where land is going up. It’s most exaggerated in Hudson Bay in Quebec. It was covered by an ice sheet in the last ice age. The enormous weight of the ice sunk into the land, and then when it melted the land began to rise back up. Because the mantle is not very supple, it takes tens of thousands of years for the crust under where the ice sheet was to rise back up. In those areas, sea level can actually fall even if it’s rising elsewhere in the world.
We hear a lot about general glacial melt, but your book clearly separates the Greenland and West Antarctic Ice Sheets from the East Antarctic Ice Sheet. What makes the Eastern sheet so different?
The Eastern Antarctic Ice Sheet is different from the Western Antarctic Ice Sheet because most of the Western sheet is grounded underwater. If you look at a picture of Antarctica, it looks like one giant white mass, and you can also see the Transantarctic Mountains. If you picked up the East Antarctic Ice Sheet, you would see land underneath. But if you removed the western side of Antarctica, you’d mostly see a bunch of islands with water in between. The sea is relatively shallow there, and the ice sheet is mostly sitting on the floor below sea level. It’s like if you put an ice cube in a bowl and several inches of water, it will just float on the top. But if you put a big chunk of ice in the bowl, it will sit on the bottom. Sitting on the ocean floor is what makes the Western Antarctic Ice Sheet much more prone to collapsing and getting disrupted.
Last month we saw Greenland’s ice melt at an incredibly fast rate. Where is all of that water going?
I’m not really sure where it’s all going, but there are two main factors to take away from that event. One is that a lot of the surface area melted, but it’s not a lot of water. What’s disconcerting about this is not that all of a sudden Greenland produced a lot of water. What’s important is that it is widely believed the water on the surface of Greenland and Western Antarctica plays a very important role in how ice streams move. The theory is that a glacier is defined as permanent ice that flows. The ice is always flowing, but it’s solid ice that’s flowing. It moves very slowly from the interior of the ice sheet out to the sea. Scientists are not entirely clear on how fast it could flow in the future, but they agree that it speeds up when water drops to the base of the ice sheet and makes the bottom more slippery, allowing the ice to move faster. It flows through cracks in the ice sheet, so when you have 97 percent of the Greenland Ice Sheet above freezing temperatures, that means more water will flow through these cracks to the base, making it more likely these glaciers will speed up.
The Greenland Ice Sheet has progressively had more water on the surface during the melt season since its been monitored. This was a highly unusual event, but it’s just part of a larger picture, which is that Greenland is melting more each summer. The amount of dripping from the surface or through cracks really matters because of how it affects ice streams. What will cause sea level to rise is if the ice streams flow faster, which break off into the sea and eventually melt. These ice streams, if we set them in motion, will add a large amount of potential water to the ocean.
Note: Lisa invited Grossman to create and answer his own question here.
How about you ask me if reporting on all this makes me depressed and lack hope?
It’s sometimes depressing to report on these issues because much of the public seems to believe the science is controversial, even though the basic science of climate change is so clear. Although there are many questions that need to be answered, like how fast sea level could go up this century, the basic shape of what’s going on is clear. Carbon dioxide is increasing, the planet is warming, and all sorts of things are being caused by that. To look around and have so little attention paid to this subject, and to see the motivations of dedicated scientists questioned, and hear it all called a hoax — that’s depressing. It’s possible things are set in motion right now that will be unstoppable in the future. We can’t be leisurely about it. The public needs to come to grips with the fact that this is the crisis of our century, and that something needs to happen.
Europe uses half as much energy as America. They come here and like coming here to indulge, perhaps in an SUV on a road trip because our gas is cheaper. It’s like someone with a healthy diet going to a steakhouse. It’s kind of nice to indulge sometimes, but they live comfortable and satisfying lives from what I can tell. We can too, because there are models to cut significantly back in terms of transportation, how we heat our homes, and how energy can be used. I hope we’ll adopt existing technologies and make advancements to help us confront this, and not put us back to another era. It’s going to cost money, and we would have to live a less lavish lifestyle. I suspect when my kids are my age, they won’t be flying in airplanes as often and with as little forethought as I do. The point is, it’s technically feasible, and it could be done without going back to pre-industrial society.
What needs to happen now?
I would never dissuade anyone from conserving energy personally or trying to encourage alternative energy, but I think the scale of this problem is large enough that we can’t leave it to the goodhearted people of the world to solve. Their efforts will be overwhelmed by people who have huge carbon footprints. I wouldn’t discourage anyone from taking those measures, but I don’t think anyone should be comforted by taking those measures.
This has got to happen on a governmental level. For example, I may choose not remodel my house with better insulated windows, but I’d vote in favor of a policy that made energy so expensive that it would make economic sense for me to put those windows in. We need policies that encourage us to do things to reduce our carbon footprint. We have to make dirty, carbon-dioxide-producing sources of energy — like oil and gas — more expensive, and subsidize clean kinds of energy — like wind and solar. It’s has to happen at a governmental level. But there’s hardly any movement in that direction today. That’s partly because responding to climate change has become a partisan issue. That’s unfortunate, because we need to get our act together. I didn’t used to be think that monetary incentives are the way to go. But I realized everyone has a price they’re willing to spend to do some good. If you change the price structure of things, people can be influenced to adopt green kinds of energy and to use energy more efficiently.
Image credits: Dan Grossman
Video credit: Maureen Raymo