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🔬 "The Sea also Rises"

What About Water?

Photo by Mathis Jrdl / Unsplash

Host: Jay Famiglietti
Guest: Steve Nerem | Principal Investigator | NASA’s Sea Level Change Team
Category: 🔬 Research

Podcast’s Essential Bites:

[2:00] “The main goal [of TOPEX] was to measure the ocean circulation. So measuring sea level change was really not part of the original mission goals for TOPEX.”

[3:29] “You have a radar onboard of a satellite, and you fire a radar pulse at the ocean surface, it bounces off the ocean surface, goes back to the satellite. The satellite measures how long it took for that pulse to go down and come back. And from that, we can determine how high the satellite is above the ocean surface. Of course, that doesn't give us what we need yet. Because we want to know what the height of the ocean surface relative to the center of the earth. And so that's where this field of orbiter termination comes in. […] We can determine the orbit of that satellite to an accuracy of a centimeter or two. […] And so by taking the height of the satellite relative to the center of the Earth, and subtracting off that radar measurement, that gives us the height of the ocean surface. […] You can determine global average sea level to a few millimeters.

[5:57] “In the past couple of years, we finally have enough data that we can see the impacts of greenhouse gases on [the ocean] map. And what it tells us is that sea level rise is not the same everywhere. Since TOPEX launched in 1982, global average sea levels have gone up about nine centimeters during that time. But there's been a lot of variability. There's some places where sea levels have fallen a little bit, like down or near Antarctica. And then other places like in the western Pacific, where it's gone up twice that amount, so it's gone up 16-17 centimeters. That's kind of the pattern of how the ocean stores its heat mainly. And so we're studying that very carefully, because we feel like, it's definitely telling us something about what the future patterns of sea level will look like.”

[7:07] “When TOPEX launched it was about two millimeters per year of global average sea level rise, but it's accelerating. And so the rate increases about 0.1 millimeters per year, every year. […] Over 30 years, that means we're starting to approach five millimeters per year.”

[8:36] “Looking at the trajectory, […] you get about 21 centimeters or so by 2050 and about 65 centimeters of sea level rise by 2100. You're heading up towards that meter type sea level change.”

[10:08] “There's […] two main sources [for the sea level rise]. One is thermal expansion. The oceans are absorbing more than 90% of the heat from climate change, which is great for us. […] But the ocean water absorbs heat and expands […] and sea level goes up. So that's one major effect. Then, of course, the other one is […] the exchange of water between the continents and the oceans. And the one we worry about the most is the melting of ice […] in Greenland, Antarctica, mountain glaciers. Because it's very hard to put the ice back up onto the continents. Once it melts and goes in the oceans, it's hard to reverse that process.”

[16:01] “[From the] warming that we have today, we're going to see that sea level change 100 years later or more. […] The term that's used in science is sea level commitment. What have you committed to in the future by the changes you made today? If we can keep warming to one and a half degrees centigrade, then we can probably keep sea level to two to three meters sea level rise. […] While we can't stop, a meter or more sea level change, we can, if we get active and reduce our greenhouse gasses, we can head off some of these huge numbers that you see later.

[16:53] “Greenland has approximately six meters of sea level locked up in its ice. Antarctica has 60 meters. […] We're not going to melt all that ice, but you start melting even a fraction of that ice and you get to catastrophic numbers that for the cities along the major cities on the coasts would be really bad news.”

Rating: 💧💧💧💧

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🕰️ 30 min | 🗓️ 02/02/2022
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