17 February 2012

Glaciers at your feet

© RTimages - Fotolia.com
Piscola is one of the national drinks in Chile. It is a mix of the aromatic spirit Pisco and cola! Now let’s have an experiment : fill a glass with ice cubes, add Pisco and cola, up to the top of the glass and wait one hour. Observe : the ice disappeared however the glass has not overflew. Why? Because the volume of ice water is quite the same as liquid water.

So does it mean that sea level is not rising because of melting Arctic, which is a big ice cube floating on the Arctic ocean? Basically yes. The contribution from its melting is minor to sea level rise.

However reducing ice masses which are on land do impact sea level…

The glaciers as indicators

Tongue of the glacier Viedma, one of the
biggest glaciers in Argentinian Patagonia.
Glaciers provide among the most visible indications of the effects of climate change. The volume of a glacier is clearly determined by the climate. As the local temperatures increase, the volume of the glacier decreases.

All around the world, the retreat of the glaciers has accelerated during the last decades. Strongest mass losses are observed in Patagonia, Alaska, northwest USA and southwest Canada. In France, half the glaciers of Pyrénées Mountains disappeared during 20th century. In 1930 Colombia had 14 glaciers ; today 8 of them have disappeared. Actually most inter-tropical glaciers are very likely to disappear by 2025 (Ramírez et al., 2001).


 A 30 meters high block of ice 
detaches from the glacier 
Perito Moreno (Argentinian Patagonia).
In few words, a glacier retreats when
more ice is lost at the front of the glacier than created at the top. 

Southern Patagonian icefield, one of the largest fields of ice on the planet

When we met Dr. Juan Carlos Aravena, he was about to take an airplane to Antarctica, the day after. Juan Carlos works at the institute CEQUA (Centro de Estudios del Cuaternario), as researcher in glaciology and paleoecology. The institute is a governmental research office, dedicated to study environment evolution in the southern part of South America and in Antarctica.
We met Juan Carlos Aravena on February the 1st
at CEQUA office, in Punta Arenas, Chilean Patagonia.
Click to enlarge
(Picture : Rivera et al., 2012)
Juan Carlos explains : “the Southern Patagonian icefield is one the biggest ice masses on Earth, after Antarctica and Greenland". As an example he adds : “the glacier Jorge Montt, located in Southern Patagonian icefield, has shown a dramatic retreat during the last century. It is one of the glaciers that is the most studied in the region. During 2011 the Chilean Centro de Estudios Cientificos (CECS) installed a camera there taking 6 pictures a day, and from to time to time a scan of the glacier is performed with laser, from a plane”. The following picture shows the evolution of the front of the glacier, since 1898.

Stored before on land, going down to the sea…

The Southern Patagonian icefield
(Google Maps)
There are several consequences to the volume decreasing of the glaciers. One of them is the water storage and supply – we talked about water availability in a previous article. “Another key consequence is the contribution to sea level rise”, says Juan Carlos. Patagonian icefields are considered to be amongst the glaciated areas which have contributed the largest proportion of melt water to sea level rise in the second part of the 20th century (Rignot et al., 2003).

Two main factors contribute to observed sea level rise. The first is thermal expansion : as ocean water warms, it expands. The second is from the contribution of ice based on land, due to increased melting. And the major store of water on land is found in Antarctica, Greenland and glaciers.

Between 1930 and 2010, a sea level rise of 18 cm was observed, and the rate of rise has clearly been higher compared to before 1850. According to the 2007 report of the Intergovernmental Panel on Climate Change (IPCC), the sea level rise could be up to 59cm by the end of 21st century. However less conservative recent studies bring more worrying conclusions : 80cm according to W.T. Pfeffer for instance (Pfeffer et al., 2008).
Sea level in the past and as projected for the future.
Over many centuries, sea level could rise by several meters. (IPCC, 2007)
Maldives buying new land

As the oceans rise, low-lying coastal areas will disappear and flooding of these areas will become more common. Loss of land and flooding will have substantial impact on local wildlife, and on humans of course : migrations of populations, social impacts, effects on health, agriculture, tourism for instance. 

More than half of the world's population currently lives in a coastal region. The delta regions are particularly vulnerable. Only 50 cm sea level rise by 2100 will hit one in ten humans around the world. China, USA, India, Bangladesh and Japan will be ones of the most concerned countries (McGranahan et al.,2007).
Relative vulnerability of coastal deltas as shown by the
indicative population potentially displaced by current sea-level trends to 2050 :
Extreme =>1 million ; High = 1 million to 50 000; Medium = 50 000 to 5 000
(Ericson et al., 2006)
As small Pacific Islands are the subject of much concern in view of their vulnerability to sea level rise, several archipelagos - like Tuvalu - have started to be very active these last years in order to warn the international community. 

In Maldives, the highest point of the country is at 3 meters above sea level. End of 2008, one of the first decisions of recently elected President Mohamed Nasheed was to create a sovereign fund with the purpose of adapting to climate change. The fund is supplied from taxes on tourism benefits. Part of it is used to buy land in Sri Lanka and India as anticipation to possible migration of population…


Few meters 
and Manhattan would not look the same!
New York City will adapt probably by building walls and dikes.
(Picture : Heidi Cullen)



  1. I liked this article, really interesting and I remember my work about the increasing of the temperatures in the low troposphera, I told you about, well, I leave the link to see the article


    Good job guys