Causes of melting tropical glaciers identified

Jun 20, 2011
Photograph of the Telata glacier (5190 m, Bolivia, Cordillera Real) in 2008, with the many moraines that were used to reconstruct the history of the glacier over the past 10 000 years. Credit: Vincent Jomelli

The causes of melting of tropical glaciers over the past 10 000 years have at last been unveiled by a team of French researchers from CNRS, CEA, IRD and Universite Joseph Fourrier, together with a US researcher from the University at Albany (State University of New York). They have shown that the retreat of the Telata glacier in Bolivia over that period is mainly linked to a 3 C rise in air temperature and to the warming of the tropical Pacific Ocean in response to an increase in insolation. Their work was published on 09 June 2011 on the website of the journal Nature.

In the collective imagination, "tropical glacier" seems to be a contradiction in terms. And yet tropical do exist, mainly in the . To identify the causes of their retreat, it is necessary to understand their recent history. 

The team of researchers studied one of the high-altitude glaciers in the Cordillera Real range in , called the Telata. The moraines (rocks deposited by the glacier, marking its earlier positions) from the Telata, which are numerous and very well preserved, make this a unique site in tropical regions. This is because they provide an almost unbroken record of successive glacial stages. The moraines were dated by measuring the concentration of certain elements in the rocks, thus making it possible for the first time to reconstruct the history of the glacier during the Holocene, in other words over the past 10 000 years.  During that period, the surface area of the glacier decreased and its front retreated by 3 km. The glacial retreat, which was initially slow, has accelerated since the beginning of the 19th century, retreating by 2 km since 1820.

The researchers from the various laboratories involved studied the possible link between the glacial volume and the prevailing temperature and precipitation values for different positions of the glacier in the past.  Calculations show that the glacier's retreat is mainly linked to warming of around 3 °C over the whole Holocene period. The very gradual increase in solar radiation at the Earth's surface affected the surface temperature of the tropical as well as the climate in the vicinity of the glacier. The increase in temperatures modified the behavior of the glacier and explains why it has retreated. However, numerical simulations with climate models show that variation in precipitation over the past 10 000 years was insufficient to affect the evolution of the glacier.

This is the first time that a study shows that the melting of these glaciers during the Holocene was closely connected to variations in surface temperatures of the Ocean. The research therefore confirms the exceptional nature of the rapid melting observed since the industrial revolution. Melting since 1820 is not linked to variations in insolation but to other mechanisms. This work shows the extreme vulnerability, over the next decades, of these tropical glaciers, which are located at high altitude in an area where warming in the 21st century is predicted to be at its highest (4-5 °C in the Telata region).

Explore further: Scientists make strides in tsunami warning since 2004

More information: Irregular tropical glacier retreat over the Holocene epoch driven by progressive warming, Vincent Jomelli, et al.,Nature, 09 June 2011.

add to favorites email to friend print save as pdf

Related Stories

2 more glaciers gone from Glacier National Park

Apr 07, 2010

(AP) -- Glacier National Park has lost two more of its namesake moving icefields to climate change, which is shrinking the rivers of ice until they grind to a halt, a government researcher said Wednesday.

Swiss glacier finely tuned to climate changes

Jun 06, 2011

(PhysOrg.com) -- During the last ice age, the Rhone Glacier was the dominant glacier in the Alps, covering a significant part of Switzerland. Over the next 11,500 years or so, the glacier, which forms the ...

Scientists expect increased melting of mountain glaciers

Jan 20, 2006

Sea level rise due to increased melting of mountain glaciers and polar ice caps will be much lower in the 21st Century than previously estimated. However, decay of mountain glaciers in due to global warming will be much more ...

Do Atlantic currents affect Alpine glacier melting?

Jun 15, 2010

Natural climate fluctuations such as variations in the Atlantic currents probably influenced glacier retreat in the Alps in the last century more than we first thought: they correlate with times of particularly ...

Recommended for you

Scientists make strides in tsunami warning since 2004

9 hours ago

The 2004 tsunami led to greater global cooperation and improved techniques for detecting waves that could reach faraway shores, even though scientists still cannot predict when an earthquake will strike.

Trade winds ventilate the tropical oceans

9 hours ago

Long-term observations indicate that the oxygen minimum zones in the tropical oceans have expanded in recent decades. The reason is still unknown. Now scientists at the GEOMAR Helmholtz Centre for Ocean Research ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

frenchie
5 / 5 (3) Jun 23, 2011
I can't believe no one has yet posted about how this research is clearly bogus and another AGW plot to take over the world.

Because everyone knows the French want to make others eat fries with Mayonaise and love socialism !!

But then again, it's hard to attack a renowned research center isn't it? Ah the irony oozing from these forums.

--------

More on point, an interesting article although more information from the paper itself would be nice.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.