Human World

World’s largest tropical ice sheet is shrinking

Lonnie Thompson: I talk about Peru because 70% of the tropical ice sheet on Earth are in Peru, so, in many ways, its going to be on the frontlines of the impact of the loss of ice from mountaintops

Glaciologist Lonnie Thompson is talking about the Quelccaya ice cap in Peru’s Andes mountains. It’s the largest tropical ice mass the world – bigger than 10 thousand football fields – but it’s shrinking.  Dr. Thompson told us that Quelccaya has nearly 25% less ice than 50 years ago. He said the first aerial photos were taken in 1963.

Lonnie Thompson: The ice cap in the first aerial photographs covered 56 square kilometers, but in the latest satellite images, it now covers less than 44 square kilometers.

The shrinking ice cap means less river water.  Rivers in Peru depend on melting ice from the mountains to maintain their flow.

Lonnie Thompson:  Peru is unusual country. It produces 76% of its electricity from hydropower. That means they depend on water from rivers to generate their power.

Thompson told us that the people of Lima, Peru are currently grappling with decreased river flow. Peru’s capital city has 8 million residents – 55% of Peru’s population. The city receives little rainfall, and relies on the flow of local rivers for both electricity and drinking water.

Lonnie Thompson:  Any reduction due to the loss of the glaciers will impact people’s ability to survive.

Thompson said that in order to cope with less water in its rivers and changing water flow resulting from changes to its glaciers, the Peruvian government is building new tunnels through the Andes mountains.

Lonnie Thompson: And building fuel-burning power plants to keep power on the grid. Of course you get into this vicious cycle of ‘what’s driving the loss of the ice to start with?’

He said that city dwellers are feeling the impact of the melting Quelccaya ice mass, but the indigenous people who subsist on the land – Peru’s Quechua people – have been even more immediately and deeply affected.  In 1991, a huge lake formed in front of the Qori Kalis glacier (an offshoot of the larger Quelccaya ice field).

Lonnie Thompson:  In March of 2006, there was an avalanche that came off the top of the big ice cap, Quelccaya, above, fell into the lake, and created a mini-tsunami that flooded the valley down below, and killed Alpaca and the like.

Quechua depend on Alpaca for their survival.

Lonnie Thompson:  This is a new geologic hazard that the people who live next to the glacier have to deal with in today’s world.

He said that climate change caused glacier melt has also rerouted streams that have been in the same spot for dozens of years, if not centuries, which also has an impact on where Quechua can subsist and take their Alpaca to graze. Thompson reiterated that climate change is real, and being experienced by Peruvians on a day to day basis.

Lonnie Thompson:  Every reporter we’ve ever taken into the field comes away with a new vision of what climate change means, because once you see it, you can’t walk away from it.

In early 2009, the World Bank released a report about the melting of the glacier of the Andes, a mountain chain in South America. If warming trends continue, the study concluded, many of the Andes’ tropical glaciers will disappear within 20 years, threatening the water supplies of 77 million people in the region. He expanded on the the idea that global warming is causing Quelccaya to melt. He talked about the history contained in the ice, which he’s accumulated from samples dating back to the 1990s.

Lonnie Thompson: There’s a wonderful history going back to 315 AD. It’s a history of temperature, through the isotopes. It’s a history of precipitation, through the layers of thicknesses. At the same time temperatures have been increasing, precipitation has also been increasing. The glacier is not only retreating, but the rate of ice loss is accelerating. That points to temperature as being the driver for the loss of ice on this largest tropical ice cap on Earth.

November 1, 2010
Human World

Like what you read?
Subscribe and receive daily news delivered to your inbox.

Your email address will only be used for EarthSky content. Privacy Policy
Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.

More from 

Beth Lebwohl

View All