Two new papers examine historical and projected Antarctic glacier behavior. The research is illuminating. Some of the commentary about it is downright confusing. I’ll sort it out in this post.
From the source: West Antarctic Ice Sheet Is Collapsing at the highly respected journal Science. This news intern’s article references a paper published in Science this week, “Marine Ice Sheet Collapse Potentially Under Way for the Thwaites Glacier Basin, West Antarctica.” You can already see where some confusion arose: the actual science article itself used the key work “potentially” while the news piece trumpeting the article used the word “is”. Potentially implies there is a chance the marine ice sheet may not collapse. The news article headline completely misses that critical descriptive adverb.
Just as importantly, the news headline misses the operative time scale, which is of course of great importance. The decision to not include the time scale leads casual readers to assume this collapse will happen soon. Well, what is soon? It depends on one’s perspective. I think the time scale omission was purposeful, so as to boost readership. Because if the headline had included the article’s values, few people would have paid much attention to it: 200 to 900 years. Based on a computer model simulation, the authors suggest that the Thwaites Glacier may finish its collapse in two to nine centuries – nowhere near the operative time frame that people think about. The article dances around the issue a bit in the first three paragraphs – long enough for the author to come out and report on what the paper actually said in my opinion.
What is not in question is the science results. The glacier is indeed melting faster than snowfall can replenish it, and this is increasingly due to human influence. Once the edge of the glacier recedes past a ridge, the glacier’s melt will accelerate. As most sea-based glaciers do, Thwaites holds back land-based ice. As this ice melts, sea level rises. Thus, the rate of sea level rise could increase from <0.25mm per year to >1mm per year due to all melting land-based glaciers.
The second paper, published in Geophysical Research Letters, Widespread, rapid grounding line retreat of Pine Island, Thwaites, Smith and Kohler glaciers, West Antarctica from 1992 to 2011, the authors report on satellite data analysis showing that
Pine Island Glacier retreated 31 km at its center, with most retreat in 2005–2009 when the glacier un-grounded from its ice plain. Thwaites Glacier retreated 14 km along its fast-flow core and 1 to 9 km along the sides. Haynes Glacier retreated 10 km along its flanks. Smith/Kohler glaciers retreated the most, 35 km along its ice plain
Upstream of the 2011 grounding line, there remain no more physical obstacles (higher sea bed regions) that will hold back the glaciers. Thus nothing remains to stop further melting of the basin. These results are an independent corroboration of the Science paper results and build the body of literature on Antarctic glaciers. Once Thwaites melts, the rest of the West Antarctic ice sheet is at risk of melt. There are other researchers who think the 200-900 year timeline is too slow because important feedbacks are not properly modeled. But so far no evidence suggests the time scale is off by an order of magnitude (i.e., not 20-90 years).
Absent significant climatological shifts away from anthropogenically forced climate change, West Antarctic and Greenland ice sheets will continue to melt for centuries. Sea levels will rise, probably at a faster rate than what we’ve seen historically.
But the presentation of these studies is disappointing. Here are some places that covered this news. I found probably the best headline at Slate: “Huge Antarctic Glacier Slow-Speed Collapse May Now Be Past Point of No Return“. That gives the reader all the critical information. Thwaites is huge, it will undergo slow-speed collapse, and that process is likely now irreversible. Good on Slate. The normally staid Jeff Masters’ somewhat less accurate headline: “Slow-Motion Collapse of West Antarctic Glaciers is Unstoppable, 2 New Studies Say“. This is better than Science’s own headline, but notice the “is” in this one. Again, I don’t think we can justifiably conclude based on science to date that the collapse is definitely unstoppable, as this headline claims. Is it likely? Yes, it is. This headline doesn’t convey that.
And now the worst example, from an Environment America fundraising email: “Antarctica to melt completely”. What?! These two studies do not say Antarctica will melt completely; such an event will take at least thousands of years, even under the highest GHG emissions scenarios. And again, there is no mention of any time line in the email header. The email includes this nonsense: “The melting of the West Antarctic ice sheet is now unstoppable – but we can still prevent even worse disasters, and President Obama is taking action right now.” I’m not sure what they consider a worse disaster than the entire Antarctic ice sheet melting (they certainly don’t make a specific claim in their fundraising request). They go on to include the worst type of messaging: “This is the nightmare scenario”. Fantastic – shut down everybody’s response mechanisms with the worst possible language. Moreover, if this is the nightmare scenario, what is the “worse disaster” they can prevent if only I send them money? The email continues “As bad as this news is, we simply don’t have time for despair.” Then why use language that causes despair?
This is exactly what the Science news piece tried to generate, and it worked. Unfortunately, that’s where the working stops. People that know about Antarctic glaciers melting are already taking action. People that don’t won’t do so just because of this email. It operates from the wrong frame and doesn’t engage alternative values. It doesn’t engage and it doesn’t present opportunities. But it’s what prominent environmental groups do and it’s why there has been polarization and inaction surrounding the issue. They continue to squander time and resources.