Saturday, June 7, 2014

West Antarctic Ice “Fuse Is Blown”: Where Can We Stop Rising Seas?

This is the blog post I hate to write.

Because it’s about worst nightmares coming true.

About tipping points and points of no return. 

We’re there.

Polar ice sheet doomed, the headline read. West Antarctic Ice Shelf on a path to disintegration - 13 more feet of water in the oceans. 

Anyone following polar ice science has seen the trend for years.  Accelerating glacier flow.  Ice shelf break-up. Going on since the 1990s, and intensifying since 2000. Arctic summer sea ice has been fading at an unexpected rate as well.  But sea ice is in the sea so it does not raise sea levels.  Antarctica and Greenland ice above sea level does. 

How far can seas rise?  Consider the Eemian, the warm period before the last ice age.  In the must-read “Assessing ‘Dangerous Climate Change’” published in December, climate scientist James Hansen and his team note that the Eemian saw global warming of at most 3.6˚F above temperatures around 1920.  Since then the planet has heated 1.1˚F.  On the current trajectory global warming will exceed 3.6˚F by the end of this century. 

What did Eemian sea levels look like?  At their peak, they were 30 feet higher than today’s.  The rise did not occur gradually.  Hansen et al note that at least 10 feet rapidly piled on in the late Eemian, “suggesting the possibility that a critical stability threshold was crossed that caused polar ice sheet collapse.”  In other words, high temperatures eventually crack and rapidly dissolve ice sheets.

That is the greatest danger posed by the West Antarctic Ice Shelf (WAIS). The study in the news was from a scientific team led by Eric Rignot of NASA.  They examined retreat of the largest WAIS glaciers.  Scientists found that the process has now become unstoppable. The shelf is in the ocean’s realm anchored to the seabed. But warm ocean waters and increased winds are undermining the grounding from the bottom.

 “. . .  we have witnessed glacier grounding lines retreat by kilometres every year, glaciers thinning by meters every year hundreds of kilometres inland, losing billions of tons of water annually, and speeding up several percent every year . . . “

Loss of those big glaciers “will likely trigger the collapse of the rest of the West Antarctic ice sheet, which comes with a sea level rise of between three and five meters (10-16 feet). Such an event will displace millions of people worldwide.”

At current rates the big glaciers would be gone in 200 years.  But rates are accelerating and rapid ice sheet collapse is in the cards.  Our children’s generation could well see WAIS go into its death spiral, maybe even some of the younger members of this generation. 

Cry for the melting cryopshere, and for low-lying coastal cities from Venice to New Orleans.

Ice disintegration doesn’t stop with West Antarctica, but moves into the big daddy of ice sheets, East Antarctica.  Go a little further back in time to around three million years ago when temperatures were 5.4˚F above the current geologic era, a point the Earth could reach in a century.  Sea levels were elevated 50-80 feet over those of today. 

Hansen et al write, “Such sea level rise suggests that parts of East Antarctica must be vulnerable to eventual melting with global temperature increases of only a few degrees Celsius.  Indeed, satellite gravity data and radar altimetry reveal that the Totten Glacier of East Antarctica, which fronts a large ice mass grounded below sea level, is now losing mass.”   

Rignot notes that Totten alone contains the equivalent of 22 feet of sea level.  Our coming generations are facing radically higher sea levels.

Can we stop this somewhere? 

I caught up with Rignot the other day to pose a question: Assume a global political-economic miracle spurred by findings such as that of your group. The world wakes up, finally, and declares an effort on the scale of World War II.  We do what Hansen et al prescribe in their December article. We begin six percent annual reductions in carbon emissions, hold total industrial era emissions to 500 billion metric tons, and pull another 100 billion of the atmosphere into vegetation and soils.  Does this avoid the eventual deterioration of WAIS?  Or is this already baked into the cake?

Eric responded, “We have already blown the fuse but the dismantling of West Antarctica could go faster if we keep heading this way. A slow down of warming would likely help get there slower.”

So there it is.  We can at best slow the disintegration of the WAIS.  With a campaign of radical carbon reduction we can give our coming generations a fighting chance to achieve a managed retreat to higher ground.

But can we stop the disintegration of Greenland and East Antarctica?  A new study shows that Greenland glaciers are more vulnerable to melting than we thought. Valleys underlying the glaciers are beneath the level of warming seas further inland than was previously known.   Greenland ice equals 20 feet of sea level, East Antarctica around 190.

How long before we read the news we’ve “blown the fuse” on substantial parts of these ice sheets?  We don’t know. But the evidence from the way this planet looked when temperatures were only a few degrees warmer says we are perilously close.

This all points to an undeniable conclusion that a dramatic carbon reduction effort is needed on the order of what Hansen et al prescribe in their article.  It may seem completely beyond the realm of political and economic possibility to move to carbon cuts of six percent annually.  It also seemed wild when Franklin Delano Roosevelt in 1940 called on the U.S. to build 50,000 planes a year when we were only making a few hundred.  By 1942, the nation reached FDR’s target. 

It’s going to take leadership.  To stay relevant in the face of ever worsening climate impacts the climate movement needs to start advancing climate solutions equal to the perilous challenges we face. Elected leaders need to step up, honestly address the desperate climate situation and forward the global carbon reduction campaign that must be undertaken.

We are already leaving our kids and their coming generations with some deeply dangerous legacies.  If we are to redeem our memory in the eyes of those who come after us, we need to act now in proportion to the immensity of the challenge. 

I close with the words of Martin Luther King Jr. addressing Riverside Church in April 1967 when he broke silence and took an active stand against the Vietnam War. His words could not be more fitting to our generation’s challenge:

“We are now faced with the fact, my friends, that tomorrow is today. We are confronted with the fierce urgency of now. In this unfolding conundrum of life and history, there is such a thing as being too late. Procrastination is still the thief of time. Life often leaves us standing bare, naked, and dejected with a lost opportunity. The tide in the affairs of men does not remain at flood -- it ebbs. We may cry out desperately for time to pause in her passage, but time is adamant to every plea and rushes on. Over the bleached bones and jumbled residues of numerous civilizations are written the pathetic words, ‘Too late.’ There is an invisible book of life that faithfully records our vigilance or our neglect. Omar Khayyam is right: ‘The moving finger writes, and having writ moves on.’”

p.s. Here’s a great video explaining why WAIS is on the way out.

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