Not All That It's Cracked Up To Be

One article in the scientific journal Geophysical Research Letters; three different takes on what it all means.

“The largest ice shelf in the Northern Hemisphere has broken in two, draining a freshwater lake beneath the ice and providing further evidence of climate change in the Earth’s Arctic reaches...” — The Washington Post.

“The scientists who report the break-up in the journal Geophysical Research Letters (GRL) say it is further evidence of ongoing and accelerated climate change in the north polar regions.” — BBC News.

“I am not comfortable linking it to global warming. It is difficult to tease out what is due to global warming and what is due to regional warming.” — Study coauthor Derek Mueller, in an interview on MSNBC.

This story has its roots in research by Warwick Vincent and Derek Mueller (scientists from Laval University in Quebec City, Canada) along with Martin Jeffries of the University of Alaska- Fairbanks. They monitor the Ward Hunt Ice Shelf on the north coast of Ellesmere Island on Canada’s Arctic coast using satellite-based radar imagery and helicopter overflights. This particular ice shelf “dams” a freshwater lake in the Disraeli Fjord. Or at least it used to. The dam began its break-up with a crack that developed in April 2000. Since then, the crack has become so large that the freshwater lake has drained into the Arctic Ocean.
      “So what,” you ask? The break up signals a major change in the area’s ecosystem and there is a question if global warming, which is anticipated first to be signaled by warming of the Arctic climate, is the cause.
      If the locale for this change was the Antarctic, the cute and lovably awkward penguin would be the poster child for this crisis. But with no penguins in the Arctic, the best the ecosystem’s champions can do is to feature a rare alga. According to Jeffries in the BBC report, “These are very rare and unusual ecosystems, and they have been studied as possible analogues for life on a colder Earth and life on the planets. And if we are losing them, we are losing the opportunity to study life earlier in Earth history and elsewhere in the Solar System.”
      If Earth is hurtling toward a globally-warmed future, why would anyone care about analogues for what life is like when it is colder? The key is in those words about “other planets.” A popular motif in science fiction is humankind abandoning Earth for colder planets because humankind has so polluted our atmosphere, that we have created a runaway greenhouse effect. In that case, we’ll need to know about the algae we will encounter, there. Or, if we find such algae in advance, it perhaps will suggest potential for terra-forming. Or it might suggest the place could eventually become more earth-like, naturally. Whatever.
      What of the temperature angle, then? It is assumed the Ward Hunt ice sheet has existed for 3,000 years in fairly stable condition. Nevertheless, by 1982 ninety percent of the ice shelf had disappeared. Then, confoundingly, its breakup stabilized over the course of the next two decades.
      Was there anything special about the pattern of Arctic temperature heading into 1982? No, not much. Figure 1 depicts summer temperatures over the Arctic as published by Serreze et al in 2000. Not only was 1982 not noteworthy, the warm spell in the late 1990s was comparable to a similar period in the 1930s. Linking changes in temperature in the alga’s ecosystem to the dam’s break-up may not be so simple after all.
      Much to its credit, MSNBC’s coverage emphasizes the angle of local warming. “Local warming of the climate is to blame...[the authors] did not have the evidence needed to link the melting ice to the steady, planet-wide climate change known as global warming,” is how the network encapsulated its coverage of this breaking news.
      In their soon-to-be-published Geographical Research Letters paper, the authors note that, in recent years, July temperatures on the Ward Hunt Shelf have increased to slightly above freezing. The resulting puddles change solar radiation absorption on the surface, thereby accelerating the melting rate, according to National Center for Atmospheric Research’s Kevin Trenberth as quoted in staff writer Guy Gugliotta’s article for The Washington Post.
      According to Gugliotta’s reporting far down his inverted pyramid, even Trenberth (who is renowned for his apocalyptic perspective on the prospect of global warming) notes how these High Arctic events probably have little to do with greenhouse gas increases.
      Other explanations for the break-up abound. It may be due to differing freeze-thaw cycles or changes in winds and tides. It may be due to differences in temperature, salinity, and circulation patterns in the Arctic Ocean. Who knows?
      Although reporting the study’s co-author reluctance to attribute the ice shelf cracking to global warming, the Post’s headline writers opine “Ice Shelf Break in Arctic Attributed to Climate Warming.” Come to think of it, that’s actually pretty clever headline writing. It’s not global warming that’s to blame, it is climate warming (which could, in fact, be local). How many of the Post’s readers do you think picked up on that subtle distinction?
      This leads us to a simple, admittedly rhetorical, question: Whenever someone (whether they be an average reader, media watchdog, or scientist) accuses the Post of biased reporting on climate change research, why does it even bother to deny the charge?

Reference:
Serreze, M.C., et al., 2000, Observational Evidence of Recent Change in the Northern High-Latitude Environment. Climatic Change, 46, 159–207.

Figure 1. Annual and seasonal Arctic temperature histories published by Serreze et al. Temperatures in the late 1990s are not much different than those of the mid-1930s.

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