Saturday, September 12, 2015
First pick your glacier
Sarah Palin pointed out that Obama had picked out one of the Alaskan glaciers that seem to be shrinking while ignoring others that are growing. The story below is a reply to that.
In the reply, however, they made a crucial and damaging admission: Glacier mass is primarily a function of precipiation (snowfall, mainly) rather than of changes in air temperature. So much so that glaciers can in fact GROW amid a warming climate.
That makes their chart below doubly amusing. It shows that glaciers have overall been losing mass right up to the present time. Since there has been no global warming during the last 18 years of that time, the chart proves that overall glacial mass proves NOTHING about global warming. The shrinkage is due only to reduced snowfall/rainfall.
But why would precipitation be reducing? Hard to say for sure. But there is one easy answer: Reduced precipitation is due to COOLING. Cooling reduces evaporation off the sea and so there is less moisture to come down as rain/snow. So the seas in most areas adjacent to glaciers are likely COOLING! Logic is pesky stuff, is it not? -- JR
Glaciers normally grow through snow accumulation in the winter and then recede by melting in the summer. But lower levels of snow accumulation or higher temperatures will lead to an imbalance in that process and the glacier will retreat and lose mass over time.
But Palin pointed out that not all glaciers are losing ice. In a post on the opinion website IJ Review, she highlighted the Hubbard Glacier in Alaska. According to NASA, the Hubbard has indeed been advancing since measurement of the glacier began in 1895, at rates ranging from 13 meters to 36 meters per year. Here is how Leigh Sterns, a glaciologist at the University of Kansas, explained the glacier’s growth for NASA: “Hubbard’s advance is due to its large accumulation area; the glacier’s catchment basin extends far into the Saint Elias Mountains. Snow that falls in the basin either melts or flows down to the terminus, causing Hubbard to steadily grow.”
In short, regional variations and increasing snowfall thanks to climate change could cause some glaciers around the world to grow, even as global temperatures rise. In fact, the pace of the Hubbard Glacier’s advance has increased since 1984, which coincides with a period of increased precipitation rates.
Just as overall global temperatures are more relevant than what happens in individual areas, the overall trend for glaciers is more relevant, too. The global and Alaskan glacial trends are toward massive loss of ice as the world has warmed. The World Glacier Monitoring Service, which runs under the auspices of the United Nations Environment Programme, the World Meteorological Organization and other partners, reports that the latest data continue “the global trend in strong ice loss over the past few decades.” This general trend is apparent in the chart below, from the WGMS.
On CNN, Tapper pushed back at Palin, saying that “90 percent of glaciers, according to scientists, 90 percent of them are—are shrinking, are melting.” According to the National Snow and Ice Data Center, based at the University of Colorado at Boulder, that’s true for alpine glaciers, which are most susceptible to retreat: “Over 90 percent of the measured alpine glaciers in the world are retreating, in almost every major glaciated region.” The NSIDC explains that the causes are “varied,” but “the underlying primary causes are a warming climate and the effects of increased soot and dust in areas of higher agricultural and industrial activity.” Both the Exit and Hubbard glaciers are alpine, of differing types—the former is a valley glacier, with its flow confined by valley walls and the latter is a tidewater glacier, which terminates into the ocean.
According to the most recent WGMS data, only 22 of the 126 glaciers it analyzed were adding mass, while 104—about 83 percent—were losing mass.
In spite of that trend, a minority of glaciers, such as the Hubbard, will likely continue to expand even with warmer temperatures. For example, a study published in 2014 in Nature Geoscience described the stable or growing glaciers of the Karakorum region in Asia. The reason for those glaciers’ deviation from the global trend has to do with localized changes to winter precipitation—snowfall, essentially, helps the glaciers stay stable or grow. The authors concluded that “[o]ur findings suggest a meteorological mechanism for regional differences in the glacier response to climate warming.” In other words, local weather patterns play a role in how glaciers respond to climate change.
Most glaciers in Alaska and around the world are losing ice as the world warms. Palin suggested that Obama was cherry-picking his glacier to make a point, but she was guilty of that trick herself.
Posted by John J. Ray (M.A.; Ph.D.).