Changes in tropical glaciers in Peru between 2000 and 2016
From The Cryosphere:
“Glaciers in tropical regions are very sensitive to climatic variations and thus strongly affected by climate change. The majority of the tropical glaciers worldwide are located in the Peruvian Andes, which have shown significant ice loss in the last century. Here, we present the first multi-temporal, region-wide survey of geodetic mass balances and glacier area fluctuations throughout Peru covering the period 2000–2016.”
“Cryoconite holes are surface melt-holes in ice containing sediments and typically organisms. In Antarctica, they form an attractive system of isolated mesocosms in which to study microbial community dynamics in aquatic ecosystems. Although microbial assemblages within the cryoconite holes most closely resemble those from local streams, they develop their own distinctive composition.”
The volcano, Chimborazo, in Ecuador, is home to a glacier that like many tropical glaciers is quickly receding. When Jeff La Frenierre, a geographer at Gustavus Adolphus College, headed to the Andes, his main objective was to understand how glaciers on this particular mountain had been responding to climate change. However, in the midst of his research, he realized he couldn’t reconcile precipitation data from weather stations with changes in the area of the glacier. To resolve this data-conflict, he turned to a technique too often ignored in the sciences: he talked to people.
La Frenierre published his findings which drew from these conversations last February, illustrating the importance of synthesizing empirical data with information from other sources, like the observations of local residents, to better understand the local effects of climate change.
Chimborazo, just south of the equator, is a place where you wouldn’t expect to find glaciers, but with a nearly four-mile-high peak (6,263 meters) the temperatures remain below freezing, so snow doesn’t melt, turns to ice and can eventually form glaciers. The glaciers found on Chimborazo are extremely important to the communities that live near the mountain. For example, glacier ice-melt is used to irrigate crops and to supply households for their domestic needs. Because of this reliance on glacial water, the people living around Chimborazo took notice when their water supply changed.
Across the board, locals in the area said that they noticed a change in rainfall and surface water in the last several decades. Though meteorological records indicated there was some warming between 1986 and 2011, the precipitation records did not suggest that rainfall amounts had changed, according to La Frenierre’s findings. But this didn’t match with the observable decrease in total ice on the mountain. The increase in temperature shown in the instrumental records could only account for about half of the glacier’s ice loss, while the survey results from local residents overwhelmingly supported the ice records.
“It would’ve been very easy, and the typical thing that many scientists would do, to look at an instrumental record and say: ‘There’s my data, there’s my conclusion from that data,’” La Frenierre told GlacierHub by phone. “If I’d left that alone then I would have had one perception of what was happening here, but clearly, looking at the instrumental data alone wasn’t good enough.”
Of course, it was important to make collecting survey data from local residents rigorous. La Frenierre accomplished this in several ways, aiming to get as broad a perception of environmental change as possible. He only collected information from people who had lived in the area for at least 10 years, for example. He also randomized the sample population by going to randomly generated coordinates within the sample area and speaking with the nearest person or household, using open-ended questions. He also conducted focus groups with members of one of the major irrigation systems.
“That’s why for me, it’s really convincing,”La Frenierre said. “There’s so much ubiquity in certain responses, so the fact that there’s less precipitation, that other sources are drying up, that the vast majority, 90 percent of people, are saying the same thing, and they’re saying it without having been given the leading questions.”
Changes in glacier size and ascension were established through remote sensing techniques, compositing satellite imagery and aerial photographs from different years. This process was complicated by the volcano’s location, because there is no cold or warm season this close to the equator, making it a challenge to determine how much of the glacier is actually glacial ice versus snow. Generally, when mapping glacial extent over time (particularly in temperate regions), researchers look at the end of the warm season. After summer melt there is minimal fresh snow and it is easy to see the entirety of the landscape.
At Chimborazo, because it is so close to the equator, there wasn’t a single image that had both the least amount of snow and was free of cloud cover. Because of this, La Frenierre ended up making mosaics combining several images that were at times months apart. This means the data cannot clearly say what the glacier extent was on any given day, but it still gives a reasonable sense of what the glacier extent was like in a certain year. This data, the changes in the glacial extent and collected opinions of locals, all pointed toward a decrease in overall precipitation. Or, as La Frenierre speculates, a change in the timing of precipitation: “In the tropics, a huge control on melting ice is the surface albedo [how much sunlight is reflected off] of the glacier. A lower frequency of snowfall, even if the same amount of snowfall falls, could actually accelerate the glacier melting.” In other words, a given amount of snow would increase the reflectivity, the albedo, of the glacier if spread over a longer period of time.
La Frenierre’s paper is not the first to be published that combines both physical instrumental or observed data with public observations. The authors cite others who have also successfully used a mixed-methods approach. But, according to La Frenierre, there should be more like it. “The reality is, especially when looking at things like environmental change, your instruments can only tell you so much. And if you can find that people are experiencing something that your instruments can’t rectify, then I think we have an obligation to try to understand where that disconnect is and look for information that answers it without assuming that our instruments are right and our people are wrong.”
The people living around Chimborazo are already directly experiencing the impacts of climate change. Although there are local actions that may have contributed, most of what is happening to the glacial ice on Chimborazo is due to global actions. “The glacial retreat that we’re seeing here is a function of the amount of carbon dioxide and other greenhouse gases that the developing world put into the atmosphere,” said La Frenierre, “We’re looking at a problem for people who are on the front lines of experiencing impacts, yet they were not the ones to benefit at all from the development that we got from putting these greenhouse gases [into the atmosphere].”
In South America, the tropical glaciers of the Andes have been shrinking at an alarming rate, leaving the local communities at risk of losing an important water source. In Bolivia, for example, an Andean glacier known as the Chacaltaya Glacier disappeared completely in 2009, cutting off a valuable water resource to the nearby city of La Paz during the dry season.
In total, the Andes Mountains are home to nearly 99 percent of the world’s tropical glaciers, with 71 percent located in Peru’s Cordillera Blanca and 20 percent in Bolivia, according to UNEP. Other tropical glaciers are found in the equatorial mountain ranges of Venezuela, Colombia and Ecuador. Over the past 30 years, scientists estimate that the glaciers of the tropical Andes have shrunk by 30 to 50 percent. This rate of decline predicts that within 10 to 15 years many of the smaller tropical glaciers will have completely disappeared.
Take a look at GlacierHub’s collection of images of the rapidly retreating Andean glaciers.