Snow, ice and permafrost

Posted: 1 April 2009

Regions on Earth where water is either in snow or ice form are called the cryosphere. The cryosphere includes snow, ice, sea ice, glaciers, ice shelves and icebergs, and permafrost. If current warming trends continue, sea levels could rise by 9 and 88 centimetres within 80 years depending on human action to reduce greenhouse gas emissions in the near future.. A sea level rise of 50 cm would represent an increase of 1.5 to 3.5 times on the historic rate of sea level rise occurring without man's interference.

Glacial melt from the Chacaltaya Glacier in Bolivia provide the city of La Paz with water, and this glacier was the highest point in the world for skiing. In 1940, this small glacier had an area of 0.22 km2. In 2005, it was less than 0.01 km2. The region surrounding the glacier has seen more glacial melt, or run-off, in the past few decades and constant or slightly decreasing levels of precipitation. The increased run-off is mostly a result of glacial retreating, and as the glacier continues to shrink, water supplies will diminish. By 2010, scientists estimate that this glacier will have disappeared.

  • Lake Tsho Rolpa, located in the Himalayas in Nepal, is a glacial lake, meaning the source of its water is glacial melt. Between 1957 and 1997, it has expanded in area from 0.23 km2 to 1.65 km2, a result of warming.
  • During the last decade, the Arctic Ocean has seen more than a 40 per cent thinning of sea ice over a large area between Fram Strait and the North Pole. Scientists believe the thinning is a result of two causes. Rising air temperatures, possibly the consequence of global warming, are melting the ice from above. And warmer water is also rising from the depths to attack the ice from below.

    • The Quelccaya ice cap in Peru are the largest tropical body of ice and have been long considered a reliable source for ice core records, but that is changing, as more recent ice is percolating down into the deeper and older layers of ice.
    • In the Alaskan tundra, the number of days in which vehicles for oil exploration can travel on frozen roads has decreased from 220 days in 1971 to 130 days in 2003.
    • Over the last 30 to 50 years, ski resorts at lower altitudes have seen a gradual decrease in annual snowfall. This has resulted in a decrease from 58 to 17 ski areas in northeastern United States, decreases in snow depth in the Swiss Alps and French Pre-Alps near the French Alps , and raising the elevation at which ski lifts begin in the central Andes in Chile.

      Sea ice

      Sea level rise 1870-2006
      Sea level rise 1870-2006
      Observed sea level rise from 1870 to 2006. Source: UNEP/GRID-Arendal. Click on image to enlarge
      Arctic sea-ice draft (the thickness of the part of the ice that is submerged under the sea) in the 1990s was over a metre thinner than two to four decades earlier. The main draft has decreased from over 3 metres to less than 2 metres, and the volume is down by some 40 per cent. NASA satellite imagery suggests that Arctic sea ice is shrinking from the edges by 2.9 per cent a decade.
    • Arctic sea ice has been in decline over the past 3 decades. Perennial ice now covers 30 per cent of the Arctic, whereas it used to cover 50 to 60 per cent.
    • The overall annual loss of Greenland's ice sheet mass has more than doubled from 90 cubic kilometres a year in 1996 to 224 cubic kilometres per year in 2005. As the ocean water warms, ice shelves connected to ice sheets melt, causing the ice sheets to melt as well. And as the water has melted it has lubricated the interface between glaciers and the rocks below, speeding the glaciers' march into the ocean. Summer melting accounts for the other half of the annual loss. Greenland is estimated to contribute 0.57 mm per year to global sea level rise - out of an estimated total of 3mm.
    • Storm surges could become more damaging and dangerous as a result of climate change. Model-based studies suggest that the number of people flooded each year by "super storm surges" could increase five-fold by 2080.
    • Rising sea levels increase the risk of coastal flooding and may necessitate population displacement. More than half of the world's population now lives within 60 km of the sea. Some of the most vulnerable regions are the Nile delta in Egypt, the Ganges-Brahmaputra delta in Bangladesh, and small islands such as the Maldives, the Marshall Islands and Tuvalu.
    • The 22 countries and territories in the Pacific Ocean have contributed under 0.06 per cent to global greenhouse gas emissions. Two small islets have already disappeared in Kiribati and many low lying islands are experiencing accelerated coastal erosion.

    GlaciersLatest findings (March 2008) from the World Glacier Monitoring Service show that the average rate of glacier melt around the world doubled in the years between 2004/5 and 2005/6 as a result of climate change.

  • Highlights of impacts from glacial retreat that can be expected in the coming decades by region (IPCC, 2007):

    Himalayas

    Glacier, Himalayas© DEP Kumar/UNEP/Topham
    Glacier, Himalayas© DEP Kumar/UNEP/Topham
    Glaciers are melting in the Himalayas© DEP Kumar/UNEP/Topham
    • Himalayan glaciers are receding in a similar way as glaciers in other mountain ranges at low latitudes. Many glaciers in these areas could, at current rates of global warming, disappear within the coming decades.
    • Half a billion people in the Himalaya-Hindu-Kush region and a quarter billion downstream rely on glacial melt waters and are expected to be seriously affected.
    • The current trends in glacial melt suggest that the Ganges, Indus, Brahmaputra and other rivers that cross the northern Indian plain may become seasonal rivers in the near future as a consequence of climate change with important ramifications for poverty and the economies in the region.
    North America
    • A two degree Celsius warming by the 2040s is likely to lead to sharply reduced summer flows coinciding with sharply rising demand.
    • Water systems that are dependent on snowmelt runoff and are nearly completely allocated and based on historic flows, like the Columbia River in the western United States and Canada are particular vulnerable to changes in the climate system which will affect snowfall and precipitation.
    • The report estimates that Portland, Oregon will by then require over 26 million additional cubic metres of water as a result of climate change and population growth.
    • This will coincide with a fall in summer supplies from the Columbia River by an estimated five million cubic metres.
    • Just over 40 per cent of the supply to southern California is likely to be vulnerable by the 2020s due to warming triggering losses of the Sierra Nevada and Colorado River basin snow pack.
    Latin America
    • Most tropical glaciers will have completely melted in the near future (2020-2030).
    • The glacier retreat trend reported in the Third Assessment Report of the IPCC is continuing and reaching critical conditions in Bolivia, Peru, Colombia and Ecuador.
    • Recent studies indicate that most of the South American glaciers from Colombia to Chile and Argentina (up to 25ºS) are drastically losing their volume at an accelerated rate.
    • Changes in temperature and humidity are the primary cause for the observed glacier retreat during the 2nd half of the 20th century in the tropical Andes.
    • Inter-tropical glaciers are very likely to disappear in the next 15 years, affecting freshwater availability and hydropower generation.
  • Permafrost thawing
    Permafrost thawing
    Permafrost thawing caused differential settlement in the foundation of this apartment building in the Russian republic of Yakutia. The building partially collapsed only days after the first cracks appeared in the walls. Photo © UNEP/V. Romanovsky
    Permafrost
    • "Permafrost, or permanently frozen ground, is soil, sediment, or rock that remains at or below 0°C for at least two years. It exists both on land and beneath offshore Arctic continental shelves, and its thickness ranges from less than 1 metre to greater than 1,000 metres. Seasonally frozen ground is near-surface soil that freezes for more than 15 days per year. Intermittently frozen ground is near-surface soil that freezes from one to 15 days per year," according to the U.S. National Snow and Ice Data Center.
    • The Northern Hemisphere has nearly 22.8 million square kilometres of permafrost, or 24 percent of exposed land.
    • By 2100, all but 1 million square kilometres of near-surface permafrost might melt, increasing flows into the ocean by 28 per cent.
    • Permafrost regions have been a large carbon reservoir, falling in carbon sink size between soil and vegetation.
    • The permafrost holds an inordinate amount of methane that, if released, could have dire impacts on the climate. One study estimated the amount of methane held in permafrost to be 970 gigatonnes. Methane has about 25 times the effect on trapping heat as carbon dioxide.
    • Analyses found that permafrost has been resilient in the face of previous glacial and interglacial periods. The Pleistocene was a much warmer time than now, and the permafrost survived.

    Related links:

    Scott Polar Research Institute

    NOAA's Arctic page

    Norwegian Polar Institute

    US National Snow and Ice Data Center