Many Glacier is considered the heart of Glacier National Park in Montana. Massive mountains, active glaciers, sparkling lakes, hiking trails and abundant wildlife make this a favorite of visitors and locals alike. Photo from last summer at Swiftcurrent Lake courtesy of Tiffany Nguyen.
This part is the “Many Glacier” area of Glacier National Park. The opening frame is Chief Mountain - a Klippe, a type of outcrop that was uplifted on a fault but where almost all the surrounding rocks have eroded away. This clip provides some great zoomed in views of the sedimentary rocks that make up the fault. The big mountains are part of the Belt Supergroup, a huge deposit of Precambrian Aged Sediments that formed in a rift basin about a billion years ago. Those sediments were uplifted along a structure called the Lewis Thrust as the Rocky Mountains grew during the Jurassic and Cretaceous. There’s one really good shot of the Lewis Thrust in this clip - it’s a horizontal line where the rocks above and below look distinctly different (they are, they’re different in age by about a billion years).
A few years ago, James Hansen, the godfather of global-warming science, told me that he believed the IPCC estimates were far too conservative and that the waters could rise as much as 10 feet by 2100. For Hansen, the past is prologue. Three million years ago, during the Pliocene Epoch, when the level of CO2 in the atmosphere was about the same as it is today, and temperatures were only slightly warmer, the seas were at least 20 feet higher. That suggests there is a lot of melting to come before the ice sheets reach a happy equilibrium. Mountain glaciers could contribute a little bit, as would the thermal expansion of the oceans as they warmed, but to get to more than 20 feet of sea-level rise, Greenland and Antarctica would both have to contribute in a big way.
But in recent years, things have gotten weird in Antarctica. The first alarming event was the sudden collapse, in 2002, of the Larsen B ice shelf, a vast chunk of ice on the Antarctic Peninsula. An ice shelf is like an enormous fingernail that grows off the end of a glacier where it meets the water. The glaciers behind the Larsen B, like many glaciers in both Antarctica and Greenland, are known as “marine-terminating glaciers,” because large portions of them lie below sea level. The collapse of ice shelves does not in itself contribute to sea-level rise, since they are already floating (just like ice melting in a glass doesn’t raise the level of liquid). But they perform an important role in buttressing, or restraining, the glaciers. After the Larsen B ice shelf vanished, the glaciers that had been behind it started flowing into the sea up to eight times faster than they had before. “It was like, ‘Oh, what is going on here?' ” says Ted Scambos, lead scientist at the National Snow and Ice Data Center in Boulder, Colorado. “It turns out glaciers are much more responsive than anyone thought.”
One day, Alley was thinking about a problem that Dave Pollard, a colleague at Penn State, and Rob DeConto, a climate scientist at the University of Massachusetts, Amherst, had been having with their climate model. DeConto and Pollard had been collaborating for years to develop a sophisticated model to help them understand the impact of warming from fossil-fuel pollution on Greenland and Antarctica. Climate models are computer programs that try to capture fundamental physics of the natural world, such as, if the temperature warms one degree, how much will the seas around the world rise? It is not a simple question, and requires calculating everything from changes in how much sunlight the ice reflects to how much one degree of heat causes the Atlantic Ocean to expand. Models have gotten a lot better in the past few decades, but they still can’t simulate all the processes in the real world.
One way that scientists test how well a model might predict the future is by seeing how well it recreates the past. If you can run a model backward and it gets things right, then you can run it forward and trust that the results might be accurate. For years, DeConto and Pollard have been trying to get their model to re-create the Pliocene, the era 3 million years ago when the CO2 levels in the atmosphere were very close to what they are today, except the seas were 20 feet higher. But no matter what knobs they turned, they couldn’t get their model to melt the ice sheets fast enough to replicate what the geological record told them had happened. “We knew something was missing from the dynamics of our model,” DeConto tells me.
Alley suggested they plug in his new understanding of ice physics, including the structural integrity of the ice itself (or lack thereof), and “see what happens.” They did, and lo, their model worked. They were able to get the Pliocene melt just about right. In effect, they found the missing mechanism. Their model was now road-tested for accuracy.
The next thing that DeConto and Pollard did, of course, was run the model forward. What they found was that, in high-emissions scenarios – that is, the track we are on today – instead of virtually zero contribution to sea-level rise from Antarctica by 2100, they got more than three feet, most of it from West Antarctica. If you add in a fairly conservative estimate of the contribution to sea-level rise from Greenland in the same time frame, as well as expansion of the oceans, you get more than six feet – that’s double the high-end IPCC scenario.
For anyone living in Miami Beach or Brooklyn or Boston’s Back Bay or any other low-lying coastal neighborhood, the difference between three feet of sea-level rise by 2100 and six feet is the difference between a wet but livable city and a submerged city – billions of dollars worth of coastal real estate, not to mention the lives of the 145 million people who live less than three feet above sea level, many of them in poor nations like Bangladesh and Indonesia. The difference between three feet and six feet is the difference between a manageable coastal evacuation and a decades-long refugee disaster. For many Pacific island nations, it is the difference between survival and extinction.
In any case, the threat is clear. In a rational world, awareness of these risks would lead to deep and rapid cuts in carbon pollution to slow the warming, as well as investment in more research in West Antarctica to get a clearer understanding of what is going on. Instead, Americans elected a president who thinks climate change is a hoax, who is hellbent on burning more fossil fuels, who installs the CEO of the world’s largest oil company as secretary of state, who wants to slash climate-science funding and instead spend nearly $70 billion to build a wall at the Mexican border and another $54 billion to beef up the military.
In the end, no one can say exactly how much longer the West Antarctica glaciers will remain stable. “We just don’t know what the upper boundary is for how fast this can happen,” Alley says, sounding a bit spooked. “We are dealing with an event that no human has ever witnessed before. We have no analogue for this.” But it is clear that thanks to our 200-year-long fossil-fuel binge, the collapse of West Antarctica is already underway, and every Miami Beach condo owner and Bangladeshi farmer is living at the mercy of ice physics right now. Alley himself would never put it this way, but in West Antarctica, scientists have discovered the engine of catastrophe.
A iceberg covered with volcanic ash in the glacial lagoon Jökulsárlón on ring road #1 on Iceland’s south coast. In June 2010, many glacier pieces were covered with the ashes of the
In this week’s Spotlight essay, Exploring Alaska’s Roadside Glaciers, Emily Epstein features Anchorage-based photographer Mark Meyer, who races against climate change to photograph as many of Alaska’s glaciers as possible.
A hiker photographs the opening of a moulin—a tunnel that courses though the glacier—in the ceiling of a cave under the Mendenhall Glacier, June 16, 2014. Glacial caves are constantly changing; this cave collapsed a few weeks after this photograph was taken. (Mark Meyer)
An ice wall and exposed crevasse in the Matanuska Glacier, July 22, 2016. (Mark Meyer)
Early morning in front of the Worthington Glacier near Valdez, July 3, 2016. This is the view from an observation deck that is just a short walk from a parking lot and a paved trail. (Mark Meyer)
Ice climbers near the bottom of the ice falls on the Matanuska Glacier, July 22, 2016. During the summer months, guided ice-climbing trips—ranging from simple introductions to the sport to all-day, intensive courses—are available from local guides. (Mark Meyer)
The glaciers don’t crush all the rocks they transport. Those that remain intact are deposited as the glacier retreats and are known as “erratics.” Erratics can range in size from enormous boulders the size of buildings to small boulders, like this one near the terminus of the Matanuska Glacier, July 29, 2009. (Mark Meyer)
A climber scales the face of one of the Matanuska Glacier seracs, July 22, 2016. (Mark Meyer)
An ice “beach” along a supra-glacial lake on the Matanuska Glacier, July 2009. Lakes of melt water often form on glaciers; they can be stable and last for years or ephemeral, quickly draining when crevasses open under the surface. (Mark Meyer)
A guide uses crampons to climb over a moulin on the Mendenhall Glacier, June 16, 2014. Moulins form when melt water and runoff find small cracks and depressions in the glacial surface and erode the ice, creating tunnels. The moulins can be dangerous and extremely deep, leading into the internal plumbing of the glacier. (Mark Meyer)
A hiker (bottom right) is dwarfed by the massive, heavily crevassed ice fall where the Harding Icefield begins its descent into Exit Glacier, August 27, 2016. (Mark Meyer)
Helicopters ferry tourists above the Mendenhall Glacier for aerial views, July 26, 2012. Although several vistas are reachable by foot, many visitors opt to go up in helicopters—a quicker, if more expensive, option. (Mark Meyer)
Jessica Taft pauses above the Harding Icefield, August 27, 2016. The ice field is thousands of feet thick, but it does not completely cover the mountains; those peaks that stick through are called “nunataks,” from the Inuit word for “lonely peak.” (Mark Meyer)