In Our Backyard No. 5 (bonus): Melting icebergs are the least of your worries when it comes to rising seas. Satellites prove it

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This is a special fifth bonus episode to In Our Backyard EP5: Sea level rise means life on California’s beaches is ending up on the rocks.

Rising seas got you confused? Severine Fournier from NASA’s Jet Propulsion Lab  explains the basics of our warming ocean as a result of climate change. What she’s got to say might melt your brain. 

Read the full episode transcript below:

WARREN: There’s a lot of talk for a lot of good reasons about the sea level rise. But, have you ever wondered why the ocean is eating away at the coast? Melting glaciers was the first thing that came to mind … ‘til we started this podcast. So let’s get a little science-y with Severine Fournier. She’s an oceanographer and research scientist at NASA’s Jet Propulsion Lab.

Severine: I mostly work on observing the oceans from space. 

WARREN: Okay. VERY science-y.

Severine: We have a lot of satellites that are measuring. They're observing the Earth. And what is great about satellites, that they're really giving a big picture of the Earth. Depending on the satellite. But like, for example, altimetry gives a map of the height of the ocean every 10 days. And that help us to monitor sea level rise and to be able to look at changes that are happening month after month, years after years, and we've been doing that for the last 30 years.

WARREN: JPL also has satellites that can measure sea ice, documenting the melting of ice on Greenland and Antarctica. All of which is to say, there’s definitive proof.

Severine: Sea level are rising about 3.3 millimeters a year, according to the data that we have collected from space for the last 30 years. So the two main two main causes are the ice sheets and the glaciers are melting all around the globe and they’re adding more water to the ocean. So this causes sea level to rise. And another reason is that the earth has been warming in the past decades and more than 90 percent of the heat has been absorbed by the ocean. And when the water warms up, the volume of this water tends to increase and expands so that we call that thermal expansion. And that causes sea level to rise when the volume of the ocean is just rising and is increasing. So the sea level is rising. 

WARREN: So thermal expansion actually accounts for about one-third of the total sea level rise. And, that other two-thirds -- the melting glaciers -- well, here’s an interesting note.

Severine: In the ocean, there is a lot of like, especially in the Arctic, there is a lot of sea ice, icebergs, but when these are melting, they're not really increasing the volume of the ocean. It's like having a glass of water with some ice in it. When the ice melts, it doesn't really increase the volume because the weight of the ice is already in the water. What's really causing sea level rise is the melt of glaciers and ice sheets that are on land and they're bringing more water to the ocean. 

WARREN: Thermal expansion and melting glaciers are the main causes of sea level rise. And, you may be thinking: well, can’t those cold ass glaciers cool down the hotter oceans?

Severine: No, that's not really how it works. There is so much heat that the oceans are absorbing that this is not something that is actually happening. And actually, when the ice is melting, then it's going to be warmed up in the ocean. 

WARREN: Weirdly enough though, sea level rise won’t impact everyone the same. Here’s why.

Severine: So the regional differences are due to different mechanisms. So there are ocean currents that are not the same everywhere, and ocean currents are actually moving the heat along, transporting heat to some places. So that has an impact. Some places are going to rise more than others due to that reason. There's also what we call the glacial isostatic adjustment, which is actually due to the last Ice Age. So it's about like 16,000 years ago, most of the Northern Hemisphere was covered by ice and these ice sheets melted. And the earth is still recovering from this, so that weight that is out of the Earth of the land now, the earth is still adjusting. So, the land is actually rising all everywhere there used to be ice. 

WARREN: If you couldn’t follow that one, here’s a nice metaphor.

Severine: If you're putting a heavy object on a mattress and then you take it out, what used to be covered by that object, the mattress is going to rise slowly. And around the regions that were covered by the object, they're going to slowly rising to kind of find the balance again. So this is kind of what has been happening for the last 16,000 years. 

WARREN: Because of this Ice Age quirk, along with other geological phenomena like land subsidence, some coastal areas are actually increasing their elevation. Does this mean that there is a chance that sea level rise will slow down?

Severine: No, no, no. Because even if in some places sea level is declining, it's only due because the earth is still recovering from this loss of weight on land, but warming and the ice melting is not something that is going to stop anytime soon. Even if we're actually decreasing the release of greenhouse gases in the atmosphere it’s going to take a while to recover from all the warming that is happening right now and that has happened in the past decades. So, no, it's not it's not going to stop anytime soon. No. 

WARREN: Now, this doesn’t mean we just throw our hands up and say forget it. Because even if we can’t stop the rising tides, if we don’t stop greenhouse emissions things could be much, much worse.

Severine: So we have a pretty good idea for the future projections, how the heat that is absorbed by the ocean is going to evolve and what's going to be the impact on sea level. But actually the water that is added due to glaciers melting and ice sheets melting, it's not very well understood. So it's very hard to make projections for that reason. But like, for example, Greenland has enough ice to raise the ocean by 25 feet globally. So that's a huge amount of ice and we've seen Greenland melting a lot for the past 20 years now. And this can accelerate. And we don't really know about that. So there's definitely a lot of ice in Greenland and Antarctica because Antarctica has been melting also quite, quite fast in recent years. And so. So, yeah, even if we are not sure and we are not very capable right now to really have good predictions there, there's definitely things that can change quite quickly. 

WARREN: Alright, so, let’s get it together! Or, else we’ll be swimming with the fishes.




Warren Olney


Julie Carli