Ice sheet collapse: The greatest unknown in climate science

New videos DAILY: https://bigth.ink

Join Big Think Edge for exclusive video lessons from top thinkers and doers: https://bigth.ink/Edge

----------------------------------------------------------------------------------

The science of glaciology and ice sheets is quite new, as methods to measure melting glaciers were only realized with the advent of aviation and lasers.

The world's sea levels are rising 3mm per year, and of that Greenland's ice sheet contributes 1mm – it is losing between 250 to 300 billion tons of ice per year. Three millimeters total is not much, but ice sheets don't always operate in a linear fashion.

No human has ever witnessed an ice sheet collapse. It is also such a rare event that models cannot accurately predict what the effect will be. Can we halt global warming before we reach that tipping point?

----------------------------------------------------------------------------------

JON GERTNER

Jon Gertner is a journalist and historian whose stories on science, technology, and nature have appeared in a host of national magazines. Since 2003 he has worked mainly as a feature writer for the New York Times Magazine. His first book, The Idea Factory: Bell Labs and the Great Age of American Innovation, was a New York Times bestseller.

----------------------------------------------------------------------------------

TRANSCRIPT:

JON GERTNER: For scientists who study climate change, one of the great challenges has been trying to figure out if these great ice sheets, these old remnants of the ice age in Greenland and Antarctica, are shrinking or growing. And we're used to, I think now, all the news stories, you know, that Greenland's losing ice, and Antarctica is melting, and that this glacier seems unstable. But really this was a kind of epic discovery of how to do it. And a lot of the ways we figured it out are through satellites and other kinds of airborne observational tools, such as laser altimeters that read the ice by sending laser bursts down and trying to measure decreases in the altitude of the ice. And, at least in Greenland, what we've discovered is that since, really, the early 1990s this ice sheet has been losing mass.

So that ice that's on top of Greenland, the frosting on the cupcake, is slowly moving into the ocean. And it moves into the ocean two ways: It melts on the surface in the summertime, and that's when you see these beautiful azure beads of lakes on the surface that eventually drain into the ocean and meltwater rivers, too. It also at the edges has these glaciers that reach into the ocean, and they break off as these huge icebergs that in turn float away and melt also. And those all raise sea levels.

The bigger picture is that, at the moment, our ocean sea levels are rising by about three millimeters per year, which is actually a pretty small amount. And the reasons that it's melting are, one, as the earth gets warmer there's something called thermal expansion, which means that the oceans literally expand, just as hot water expands, [it] gets larger and higher. The other reason is that there are mountain glaciers all over the world in the Himalayas and Canada and Alaska, and those, too, are draining into the water and they make a contribution. And the third reason is that Greenland and Antarctica are losing ice, both through -- especially Greenland's -- surface melting and through these glaciers that break off into icebergs, and they're raising sea levels.

At the moment, Greenland's contribution is one millimeter per year. And we could maybe put that aside, and say, well one millimeter a year isn't very much, but that's accelerating. What we also know is that things don't necessarily move in a linear way with ice sheets. A lot of the science of glaciology and ice sheets is pretty new. It's not like we can go back 100 years and try and sort of figure out -- or that we knew at that point how ice sheets work. In fact, we can look at an ice sheet now in Greenland or in Antarctica, in West Antarctica, for instance, and we know that no human being has ever seen what we're seeing now. Nobody's ever really witnessed the collapse of an ice sheet. There's nothing in recorded history that explains how an ice sheet collapses in warmer temperatures.

So we're in this place now where what we know is that the climate is warming dramatically. We know the ice sheets become more unstable in warmer temperatures. We know they have vulnerabilities. We also don't know precisely how the physics of big ice sheets work. And we try and create models, scientists do try and create models, but those models aren't necessarily as good as some other models that predict, say, future temperatures. We've heard, well, if the earth, you know, if we put so much CO2 into the air we're going to war...

For the full transcript, check out https://bigthink.com/videos/ice-sheet-collapse-the-greatest-unknown-in-climate-science