Glacial melt provides strong evidence for climate change and poses serious threats to vulnerable communities.
Glaciers are large bodies of ice that exist year-round in high mountains and the polar regions, where they can be termed ice-sheets or ice-caps.
Throughout the Earth’s history glaciers have grown and shrunk with variation in the planet’s overall temperature.
But in recent years, human activities are thought to have artificially elevated the temperature through the greenhouse effect, and this has been blamed for a marked melting of glaciers around the world.
Although some glaciers are growing in mass and extent, the vast majority are shrinking and in retreat, as seen in this image of the Columbia Glacier, which has retreated steadily between 1989 and 2008.
As glaciers melt they increase the flow of water downstream and so raise the risk of flooding and contribute to rising sea levels.
Over the longer term, glacial melt will reduce river flows and limit supplies of freshwater if the ice melts faster than fresh snow can replace it.
Glacial melt also poses more immediate threats. As glaciers retreat, the masses of earth, boulders and other debris that they had been pushing downwards can form a wall that traps melting water and form a lake.
These lake walls are highly unstable and can collapse suddenly if too much water accumulates behind them or if there is a landslide or earthquake.
This triggers a glacial lake outburst flood (GLOF) that can cause catastrophic damage. The huge quantity of water that such a flood releases can form a tsunami.
When this happened in Iceland in 1996, the tsunami was four metres high and 600 metres wide. The flood carried ice flows that weighed up to 5000 tonnes.
The Intergovernmental Panel on Climate Change (IPCC) concluded in 2007 that: “Widespread mass losses from glaciers and reductions in snow cover over recent decades are projected to accelerate throughout the 21st century, reducing water availability, hydropower potential, and changing seasonality of flows in regions supplied by meltwater from major mountain ranges (e.g. Hindu-Kush, Himalaya, Andes), where more than one-sixth of the world population currently lives.”
However, the IPCC made a serious error in its 2007 report when it included a projection that the Himalayan glaciers could disappear by 2035 (instead of 2350).
In January 2010, the IPCC issued a statement [pdf] in which it defended the bulk of what it had said about glacial melt in its Fourth Assessment Report (2007) but acknowledged the error about projected date for the disappearance of Himalayan glaciers.
In its assessment of the rate of sea level rise, the IPCC deliberately did not include any increase from melting ice caps and glaciers, which has led some critics to say the IPCC has underestimated the scale of that threat.
The most effective way to minimize the risks from glacial melt would be a rapid and deep reduction in global emissions of the greenhouse gases that contribute to rising temperatures.
In the absence of this — and because the Earth is already committed to some additional warming from past emissions — there are a number of things that governments, scientists, communities and others can do to lessen the threats that glacial melt poses.
These include more and better research on the state of glaciers. This will need automated monitoring systems, satellite imaging, and ground level surveys — as well as a better understanding of the traditional knowledge of local communities.
This 2010 report from the International Centre for Integrated Mountain Development describes, for instance, a methodology for mapping glacial lakes and identifying those that may be at risk of forming dangerous floods.
Such mapping can allow planners to locate new facilities – such as hydro-power dams – in safer areas. Other ways to adapt to glacial melt include creating early warning systems to warn of imminent floods.
Glaciers vary greatly according to their regions, altitudes and other local factors, so it is important to avoid basing conclusions about one area’s glaciers on information from somewhere else.
Some glaciers are advancing, not retreating, and this brings a different set of risks. For others, their rate of change has been grossly exaggerated, while for many more there is simply not enough information available yet.
This article [pdf], by glaciologist Kenneth Hewitt, explains some of the pitfalls that journalists may encounter when reporting on glacial melt.
Another good source is Global Glacier Changes: facts and figures, a joint report by the UN Environment Programme and the World Glacier Monitoring Service.
The Extreme Ice Survey has information and photographs from glaciers it has been monitoring around the world for more than two years.
CASE STUDY – The Third Pole
The Tibetan Plateau is the world’s largest store of ice after the poles but that ice is melting fast – most of the plateau’s glaciers are retreating.
The plateau has warmed by 0.3 degrees Celsius every ten years for the last 50 years. This increase is three times faster than the global average.
Why does this matter? First, because people live there and they depend heavily on nature. Their livelihoods and their health will be hit hard by climate change.
But it is not only local people who will be affected. Runoff from the region’s mountains feeds the largest rivers across Asia, including the Yangtze, Yellow, Mekong, Ganges and Indus rivers. More than a billion people – a fifth of the world’s population – depend on such rivers for their water supplies.
But ice is melting faster than it is being replaced by fresh snow, meaning that the water supply for drinking, bathing and farming will diminish.
For more information, visit ChinaDialogue which has set up a website dedicated to news about viewa about the Third Pole, in partnership with Internews’ Earth Journalism Network.
Formation of Glacial Lakes in the Hindu Kush-Himalayas and GLOF Risk Assessment (2010)
The Waters of the Third Pole: Sources of threat, sources of survival [PDF]
World Glacier Monitoring Service
World Bank – Bolivia, Ecuador, and Peru: Adaptation to the Rapid Glacier Retreat in the Tropical Andes Project
Glacier Retreat: Reviewing the Limits of Human Adaptation to Climate Change