Glaciers are large bodies of ice that exist year-round in high mountains and the polar regions, where they can also be known as ice-sheets or ice-caps.
Throughout Earth’s history, glaciers have grown and shrunk depending on the planet’s overall temperature. In recent years, human activities are argued to have elevated the Earth’s temperature through the greenhouse effect which has been blamed for the shrinking of glaciers around the world. Glaciers shrink when the rate of melting surpasses the rate of formation from snowfall.
Although some glaciers are growing in mass and extent, the vast majority are shrinking and in retreat. For example the Columbia Glacier in Alaska has retreated steadily between 1989 and 2008.
Glacial melt can have global and local effects. Globally, it can lead to rising sea levels and with that, flooding. According to the National Snow and Ice Data Center, if all land ice melted, global sea levels would rise approximately 70 meters.
Additionally, glaciers and permafrost (frozen soil) hold methane gas bubbles, a major greenhouse gas. As melting increases, this methane is released which further increases the concentration of greenhouse gases.
Locally, glacial melt disrupts water flow to rivers. In the short term, the increased melting could lead to erratic water levels. In the long term, as glaciers melt, the amount of water flowing into rivers dependent on glaciers would decrease. According to the Inter Press Service, 200 million people worldwide depend on glaciers for their source of water.
Glacial melt also poses more immediate threats such as a glacial lake outburst flood (GLOF). 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. When the walls collapse, a huge quantity of water is released and can form a tsunami. When this happened in Iceland in 1996, the tsunami was four meters high and 600 meters wide. The flood carried ice flows that weighed up to 5000 tons.
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 are found worldwide 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. Additionally, glaciers have different scopes of impact and it is important to recognize the degrees of impact when reporting.
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.
National Snow and Ice Data Center
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