Monday, August 6th 2012, 5:57 AM EDT
In July, the global warming hot lines were glowing red with shocking news: NASA scientists were stunned as images from three satellite showed “unprecedented” thawing at or near the surface over most of Greenland’s ice sheet. The event began on July 8, and lasted four days before refreezing. NASA ice scientist Tom Wagner observed, “You literally had this wave of warm air wash over the Greenland ice sheet and melt it.”
While normally about half of the Greenland ice sheet sees surface melting over the summer months, this time the thaw area jumped from 40% to 97%. Some surface melting extended to the Summit Station at the high altitude of two miles above sea level. And to make this even more exciting, that happened only a few days after a giant iceberg broke off from the Petermann Glacier in northern Greenland.
So all of this is really unprecedented, right? Ummm… not entirely. Based upon Summit Station ice core records, this occurs about every 150 years. According to Lora Koenig, a glaciologist from NASA’s Goddard Space Flight Center in Maryland, “With the last one happening in 1889, this event is right on time.”
And why did it happen? As University of Georgia climatologist Thomas Mote commented, “[This] summer in Greenland has been freakishly warm so far. That’s because of frequent high pressure systems that have parked over the island, bringing warm clear weather that melts ice and snow.”
He and others observed that it was similar to high pressure systems that have parked over the American Midwest, bringing record-breaking warmth and drought. These conditions were caused by natural La Niña sea surface temperature cooling in the equatorial Eastern Central Pacific Ocean that shifted the jet stream on a more northward path than usual. That shift has brought drier conditions across the central and south-central states, and has also blocked cooler arctic air from moving south into the American mid-section.
Tom Wagner further explained, “The Greenland ice sheet has a vast area with a varied history of change. This event, combined with other natural but uncommon phenomena, such as the large calving event last week on Petermann Glacier, are part of a complex story. Satellite observations are helping us understand how events like these may relate to one another as well as to the broader climate system.” Then he added, “We have abundant evidence that Greenland is losing ice, probably because of global warming, and it’s significantly contributing to sea level rise.”
So it’s really about global warming after all? And it’s our fault? And the oceans are likely to rise to perilous heights? And it’s all really, really scary?
Well it seems that maybe those melting Greenland glaciers aren’t all rushing to the sea nearly quite so rapidly as breathlessly advertised in the media. A study reported in the May issue of Science titled “21st Century Evolution of Greenland Outlet Glacier Velocities”, examined 200 of them across that continent over a period between 2000-2010 using radar data collected from synthetic aperture satellites. The research found that their individual flow rates were complex and varied, both in location and time.
Glaciers with growth rates that were found to be accelerating during a few years, decelerated in others. Some accelerating glaciers were in proximity to others that were decelerating. The authors hypothesized that a variety of local factors controlled their individual behaviors, including: fjord, glacier, and bed geometry; local climate; and small-scale ocean water flow and terminus sea ice conditions.
Glaciers in the northwestern portion of Greenland typically showed accelerations throughout the study period, while those in southeastern Greenland showed speed-up from about 2000-2005, then remained fairly steady rates from 2006-2010. Overall, the speed-ups across Greenland were much lower than the UN Intergovernmental Panel on Climate Change projections based upon climate models made them out to be.
The IPCC has asserted that globally, “…the late 20th century glacier wastage likely has been in response to a post-1970 warming.” Here, they emphasize that “Because of the corresponding large areas, the largest contributions to sea level rise came from Alaska, the Arctic and the Asian high mountains. Taken together, the ice sheets in Greenland and Antarctica have very likely been contributing to sea level rise over 1993 to 2003 [italics in the original].”
So then, of course, even if we aren’t necessarily responsible for causing Greenland to melt, we certainly can’t escape guilt for those accelerating West Antarctica ice losses. Otherwise, why would Al Gore take more than 100 of his feverishly overheated friends there last January to focus attention on the threat climate change we are causing poses to the world’s ice sheets and glaciers?
But wait! There is some new information to suggest that maybe we’re not entirely at fault for causing this either!
In July, experts from the University of Aberdeen and British Antarctic Survey reported that a that a huge one mile deep rift valley, (the “Ferringo Ice Stream”) located beneath the ice in West Antarctica, may be largely responsible causing melting in this region to occur more rapidly than in any other part of the continent. That previously hidden ice-filled basin about the size of the Grand Canyon directly connects with the warmer ocean.
Incidentally, the ocean has very likely been warming since the “Little Ice Age” ended in the mid-1800s (before the Industrial Revolution began). Research reported by the Scripps Institution of Oceanography at UC San Diego and the UK-based National Oceanography Center in the April on-line edition of Nature Climate Change, shows that the magnitude of temperature change since the 1870s is twice that observed over the past 50 years. The authors believe this implies that “…the time scale for the warming of the ocean is not just the last 50 years but at least the last 100 years.” That total increase has been largest at the ocean surface (1.1 degree F), decreasing to .22 degree F at about 3,000 feet depth (still above the level of the one-mile deep rift valley.)
The rift valley was first discovered by University of Aberdeen glaciologist Robert Bingham in 2010, who reported: “Over the last 20 years we have used satellites to monitor ice losses from Antarctica, and we have witnessed consistent and substantial ice losses from around much of its coastline. For some glaciers, including Ferringo Ice Stream, the losses are especially pronounced, and, to understand why, we needed to acquire data about conditions beneath the ice surface.”
It wasn’t easy to find. The team gathering the data had to tow an ice-penetrating radar system behind a skidoo 1,500 miles over ice before finding it lying about a mile deeper than the surrounding flat landscape. Dr. Bingham said, “This is at odds with the flat surface that we were driving across…without these measurements we would never have known it was there.”
So gosh, that appears to be a pretty big discovery, not to mention the welcome news that the “unprecedented” Greenland thaw this summer had occurred many times before Henry Ford acquired his first wrench. And given all the attention and concern we have been hearing about melting Antarctic and Greenland glaciers causing oceans to rise faster than our national debt, wouldn’t you expect to hear these glad tidings trumpeted by an exuberant mainstream media?
Well, on second thought…probably not.