January 22, 2013
Unprecedented Glacial Melting In Andes Blamed On Global Warming
Alan McStravick for redOrbit.com - Your Universe Online
Only four months ago and a continent away, researchers were looking into the varying degrees of ice accumulation and ablation within the Himalayan glacial system. In that report, published by the National Research Council (NRC), the team concluded that glacial melt could pose significant issues for the native populations that depend on the water runoff from these glaciers for their day-to-day lives.
An international team of scientists from Europe, South America and the U.S. has turned its focus to glacial melting in the tropical Andes, and their conclusions indicate that the situation is even more dire than originally suspected. Globally, glacial melt has been observed as occurring at a moderate rate as a result of natural warming after the peak of the Little Ice Age.
The Little Ice Age was a cold period that lasted from approximately the sixteenth to the nineteenth century. What drew this team to the Andes, however, was the alarming rate at which melting in this region has been observed over just the past few decades. Their report, published in the open-access journal The Cryosphere, was released today.
After completing the most comprehensive review of Andean glaciers to date, the researchers lay the blame for this unprecedented rate of ablation squarely at the feet of the rising temperatures in the region. Over the last 60 years, the tropical Andes have seen an average temperature rise of approximately 1.25°F. While this increase may seem negligibly small, the team estimates that the temperature rise is responsible for a total glacial shrinkage of anywhere from 30 to 50 percent since the 1970´s. Moreover, the glacial retreat caused by this increase may very well affect the general water supply to Andean populations in the very near future.
According to Antoine Rabatel, researcher at the Laboratory for Glaciology and Environmental Geophysics in Grenoble, France and lead author of the study, the retreat of glaciers has been noted everywhere in the tropical Andes but is far more pronounced for the smaller glaciers that are found at lower altitudes. Glaciers found at altitudes under 3.5 miles above sea level have lost an approximate 4.5 feet of thickness per year since the late 1970´s. This loss is extraordinary as it represents a thickness loss that is twice the rate of the larger, higher-altitude glaciers.
"Because the maximum thickness of these small, low-altitude glaciers rarely exceeds 40 metres [131 feet], with such an annual loss they will probably completely disappear within the coming decades," says Rabatel.
In their research, the team also took into account the annual rainfall amounts. They determined that there was little to no change in this variable over the past few decades. Average rainfall, they claim, cannot be factored into account for the changes noted in glacial retreat. The team´s contention is that climate change is singularly to blame for the glacial melt in the tropical Andes. In the period between 1950 and 1994, the temperatures in this region saw an increase of approximately .25°F per decade.
"Our study is important in the run-up to the next IPCC report, coming out in 2013," says Rabatel. The Intergovernmental Panel on Climate Change (IPCC) has previously noted that tropical glaciers, like those being observed in the Andes, are important indicators of climate change because they are particularly sensitive to temperature changes. The Andes are home to some 99 percent of all of the planet´s tropical glaciers, the majority of which are located in Peru.
The alarm bell the researchers hope to sound is directly related to the regional crisis we may soon see as a result of the loss of these tropical glaciers. Their research is important for monitoring the future behavior of Andean glaciers and the impact the accelerated melting may pose for the region and its inhabitants.
“The ongoing recession of Andean glaciers will become increasingly problematic for regions depending on water resources supplied by glacierised mountain catchments, particularly in Peru,” explained the researchers. They claim that should this melt continue with no change in precipitation patterns, the entire region can expect to face a water-shortage crisis in the near future.
Perhaps most heavily affected will be the Santa River valley in Peru. This valley is home to hundreds of thousands of inhabitants whose lives and livelihoods depend upon tropical glacier runoff for agriculture, domestic consumption and hydropower. Perhaps even more troubling, the larger cities of the region — like the Bolivian capital La Paz — could also experience crippling water shortages. “Glaciers provide about 15 percent of the La Paz water supply throughout the year, increasing to about 27 percent during the dry season,” according to Alvaro Soruco, a research team member from Bolivia.
To arrive at their conclusion, the team integrated data that had been collected over several decades, some dating as far back as the 1940s. “The methods we used to monitor glacier changes in this region include field observations of glacier mass balance, and remote-sensing measurements based on aerial photographs and satellite images for glacier surface and volume changes,” explained Rabatel.
Glacier mass balance, as referenced above, is a measurement of the difference between ice accumulation and ablation in a glacier. Typically, scientists express the annual mass balance in meter water equivalent (m.w.e).
This comprehensive study examined data collected for glaciers across the region in the countries of Columbia, Ecuador, Peru and Bolivia. This undertaking covered a total of almost 625 square miles. This coverage area is representative of approximately 50 percent of the total area covered by glaciers in the tropical Andes in the early 2000s.
The intent of the team´s published findings was to provide the scientific community with a comprehensive overview of the status of glaciers in the tropical Andes. The team wanted to definitively determine the rate of glacial retreat and identify the causes for it. But Rabatel and his co-authors are hoping their findings will find much wider resonance.
"This study has been conducted with scientific motivations, but if the insight it provides can motivate political decisions to mitigate anthropogenic impact on climate and glacier retreat, it will be an important step forward," he concluded.