Triple Threat from Tripled Rate of Ice Melt

By Judith Stapleton

antarctic iceberg

The rate of Antarctic ice melt has tripled in just the last five years, and the impact of this exponential change in the rate of ice melt ripples through all earth’s life systems, creating an echo chamber of danger and unpredictability. One thing is certain, however: the seas are rising faster than our preparations.

We have known this was likely to happen. In the three decades since James Hansen, then of NASA, warned of the effects of increasing amounts of CO2 in our atmosphere,

nearly half of the Arctic ice cap has disappeared, all the oceans have acidified, drought conditions have made normal life impossible, much of the North American West has caught fire, lower Manhattan, South Florida, Houston, and New Orleans have flooded by inundation of the sea, and average temperatures have continued to climb. As I write these words, the Mauna Loa Observatory reports the CO2 levels today are higher than life can tolerate, at 410.97 ppm.

The journal Nature recently published a report titled “Mass balance of the Antarctic ice sheet from 1992-2017.” The research is a collaboration of several agencies that contribute to assessment reports of the Intergovernmental Panel on Climate Change, the IPCC. The IPCC is a group of thousands of scientists working on climate change under the auspices of the United Nations.

The report’s lead author, Andrew Shepherd, of Leeds University Institute for Climate and Atmospheric Science, finds that the increased rate of melt over the last few years means that over 200 billion tons of ice are melting into the oceans annually now, and this fresh water addition to oceans will contribute to at least six inches of sea level rise in the coming decades. Already, since 1992, three trillion tons of ice have disappeared from Antarctica.

The point about a change in the rate of melt is significant, says Professor Shepherd. The last survey of Antarctica was five or six years ago, and at that time, the ice was melting at a fairly steady rate—about the same each year. Now we are concerned about the future contribution to sea levels and salinity.

Satellite imagery allows us to compare prior and present measurements, and there is no question that West Antarctica, which holds enough ice to raise sea levels by four metres (over 13 feet), is increasingly losing its glaciers as they hit the warming ocean. As the front end of the glaciers disappear into the water in enormous fractures, like quakes in a mountainside, nothing is left to hold back the remaining glacier ice, and eventually it too will pour into the sea.

The more ice falls into the oceans, the fresher they become, and that changes the circulation patterns that move heat from the equator to the poles and back again, creating the thermal winds in which both birds and planes fly, and which have brought the seasonal variations of warm and cold and wet, which shape life everywhere.

Ice loss at the South Pole causes global sea levels to rise more in the northern hemisphere than in the southern half of the globe because of the way that gravity balances out the load. In the northern hemisphere, says Shepherd, “we should expect more than 15 centimetres [about half a foot] if the ice losses continue as they are today.” That should cause people to think about the frequency of flooding in a different way.

In other words, worldwide, low lying regions will flood whenever weather conditions are extreme, and because the freshening of the oceans directly affects weather, this fact ought to motivate a kind of habitat planning we have never done before. Higher sea levels mean more flooding, and there are expensive defences to plan if people are going to stick it out where they live now.

It is not only melting polar ice that contributes to sea level rise. The temperatures of the water have been increasing as the sunlight is no longer reflected back into space by the albedo effect, and this penetration of radiant sunlight into the depths of the oceans causes an expansion in the volume of water. Shepherd’s study estimates that half of the sea level rise [up to two feet] will come from the expansion of the oceans.

Another source is the loss of the Greenland ice sheet—a well-documented concern that has, as a result of this report, been supplanted as the most significant source. Says Shepherd, “We think that Antarctica could easily take over.”

He also points to the contributions made by melting mountain glaciers on every continent, as well as changes in our methods of storing water, which affect how much gets returned to the sea.

But the biggest uncertainty now is sea level rise from Antarctic ice melt, and until now, our predictions have been on the low side.

Nothing can change this momentum except a lowering of ocean temperatures. For the lead author in this IPCC report, this is unlikely.  “I don’t know that many people expect the ocean temperatures to cool anytime soon, and so we have to, perhaps, adapt and expect some sea level rise. And the sooner people believe that the sea level rise will come, irrespective of what caused the changes in the first instance…people should trust us on that, and then start asking their politicians what they’re going to do about it.”

Climate warming poses ever-increasing risks. If we search for a metaphor, this report says the evidence now is more like a fire alarm sounding off in a building whose occupants have been locked in.

“Thirty years ago, we may have seen this coming as a train in the distance,” Deke Arndt, the chief of climate monitoring at the National Oceanic and Atmospheric Administration centre in Asheville, North Carolina, recently told the A.P. “The train is in our living room now.”

Professor Shepherd’s best advice is, “it’s best to work on the assumption that if things stay as they are today, the sea level rise will come. And on that basis, every coastal city should have a very clear and transparent, and actually broadcast to the citizens, coastal flood protection policy and what they’re going to do in the next 50 years. If you want to raise San Francisco’s or Vancouver’s riverfront by 50 or 100 centimetres [20-40 inches], that’s going to require some thought. It’s not by any stretch of the imagination impossible to do. It can be done. But none of those cities will want a wall around their coastlines, because this is a major attraction, and it is also for the residents a beautiful thing.”

He goes on to say, “this causes disruption and money, and they should be fully costed plans. And people should see those plans, and the policy makers and town planners should present them now.”

We have known this was likely to happen. The term “greenhouse effect” first appeared in public in 1965 in a report to President Lyndon Johnson, predicting “measurable and perhaps marked changes in climate” in the decades to follow. This was the first warning to receive national, and then international, news coverage. The Times ran the story at the top of the front page, with a graph showing a long-term rise in average global temperatures.

The scientific focus turned ever more directly towards the elements of global warming, but the four pillars of democracy have been playing with the evidence ever since. [The Pillars are: the legislature, executive, judiciary, and the media].

In her retrospective interview with James Hansen this June, Pulitzer Prize-winner Elizabeth Kolbert asked the scientist if he had a message for young people today. He said, “The simple thing is, I’m sorry we’re leaving such a fucking mess.” 

 

Publishers Notes:

Elizabeth Kolbert has been a staff writer at The New Yorker since 1999. She won the 2015 Pulitzer Prize for general nonfiction for “The Sixth Extinction: An Unnatural History.”  

Judith Stapleton is a writer in the fields of science and medicine.