The glacier extends through the Illulisat Icefjord, surrounded by mountains. Icebergs calve off from the main glacier, pile up and block the fjord before being released into Qeqertarsuup Tunua (Disko) Bay and Davis Strait. The whiter areas in the fjord are piledup icebergs and the “real” glacier ends where the greyish striped section ends – showing that this image is from 2001. The graph shows glacier-velocity profiles for 1985 to 2006. During th...

Passive microwave sensors on satellites have monitored the extent of the sea ice cover since 19782. This technique is widely used to investigate fluctuations in ice extent over the seasons, variability between years, and longterm trends. The seasonal variation of ice extent is much greater in the Antarctic where there is about six times as much ice in winter as in summer. Currently, in the Arctic, ice approximately doubles from summer to winter. ...

The lines represent IPCC Special Report on Emissions Scenarios (SRES) based on different world views. The differences in impacts between the SRES scenarios for the same amount of sea-level rise and protection response reflect differences in exposure (population) and ability to adapt (wealth). The solid lines represent a level of 'constant' (no additional) protection response. The dashed and dotted lines represent the addition of protection respon...

Feedback refers to the modification of a process by changes resulting from the process itself. Positive feedbacks accelerate the process, while negative feedbacks slow it down. Part of the uncertainty around future climates relates to important feedbacks between different parts of the climate system: air temperatures, ice and snow albedo (reflection of the sun’s rays), and clouds. An important positive feedback is the ice and snow albedo feedback...

Temperature monitoring in Canada indicates a warming of shallow permafrost over the last two to three decades. Since the mid-1980s, shallow permafrost (upper 20-30 m) has generally warmed in the Mackenzie Valley. The greatest increases in temperature were 0.3 to 1°C per decade in the cold and thick permafrost of the central and northern valley. In the southern Mackenzie Valley, where permafrost is thin and close to 0°C, no significant trend in pe...

The global conveyor belt thermohaline circulation is driven primarily by the formation and sinking of deep water (from around 1500m to the Antarctic bottom water overlying the bottom of the ocean) in the Norwegian Sea. When the strength of the haline forcing increases due to excess precipitation, runoff, or ice melt the conveyor belt will weaken or even shut down. The variability in the strength of the conveyor belt will lead to climate change in...

The most recent geological history, in the last hundred thousand years, has been characterised by cycles of glaciations, or ice ages. The historic temperatures, through these times, have been low, and continental ice sheets have covered large parts of the world. Through ancient air, trapped in tiny bubbles in the Antarctic ice, we have been able to see what the temperature cycle was at that time, and also the concentration of carbon dioxide (CO2)...

Major glacier hazard locations

The red line indicates the median minimum extent of the ice cover for the period 1979–2000. This figure compares the Arctic sea ice extent in September for the years 1982 (the record maximum since 1979), 2005 and 2007 (the record minimum). The ice extent was 7.5 million km2 in 1982 and only 5.6 million km2 in 2005 and down to 4.3 million km2 in 2007. As has been observed in other recent years, the retreat of the ice cover was particularly pronoun...

Warming is widespread, generally greater over land than over oceans, and the largest gains in temperatures for the planet are over the North American Arctic, north central Siberia, and on the Antarctic Peninsula. These recent increases in temperature are confirmed by changes in other features: loss of sea ice, shift of tundra to shrub vegetation, and migration of marine and terrestrial ecosystems to higher latitudes.

Ringed seals are the 'classic' Arctic seal in many regards, being found as far north as the Pole because of their ability to keep breathing holes open in ice that can reach 2 metres in depth. This species is certainly one of the most vulnerable of the high-Arctic seals to the declines in the extent or quality of sea ice because so many aspects of their life-history and distribution are tied to ice. Ringed seals also require sufficient snow cover...

Mass-balance estimates for Greenland show thickening at high elevations since the early 1990s at rates that increased to about 4 cm per year after 2000, consistent with expectations of increasing snowfall in a warming climate. However, this mass gain is far exceeded by losses associated with large increases in thinning of the ice sheet near the coast. Total loss from the ice sheet more than doubled, from a few tens of billions of tonnes per year ...

Thirty reference glaciers with almost continuous mass balance measurements since 1975 show an average annual mass loss of 0.58 m water equivalent for the past decade (1996–2005), which is more than twice the loss rate of the period 1986–1995 (0.25 m), and more than four times the rate of the period 1976–1985 (0.14 m). The results from these 30 continuous mass balance series correspond well to estimates based on a larger sample of more tha...

Limited by the availability of detailed observations, most historical evaluations of changes in freshwater ice have focused on relatively simple characteristics, such as the timing of autumn freeze up and spring break up, and maximum ice-cover thickness. Based on 27 long-term (about 150-year) records from around the Northern Hemisphere, Magnuson and others (Figure 8.1) discovered that freeze up has been delayed by approximately six days per hundr...

By far the largest area of glaciers and ice fields are found in Canada (about 201 000 km2), followed by Alaska (about 75 000 km2) with about 700 km2 in the rest of the USA. Glaciers and ice fields are concentrated in the High Arctic and western cordillera. The total area of glaciers and ice caps, without the ice sheets and surrounding glaciers and ice caps in Greenland and Antarctica, sums up to 540 000 km2.

Measurements on this valley-type glacier in the North Chuyskiy Range show a slightly negative annual mass balance trend culminating in an ice loss of about 4 m water equivalent over the period 1964–2005.

Data from satellite monitoring from 1966 to 2005 show that mean monthly snow-cover extent in the Northern Hemisphere is decreasing at a rate of 1.3 per cent per decade. For the calendar year of 2006 average snow-cover extent was 24.9 million km2, which is 0.6 million km2 less than the 37-year average. In the Northern Hemisphere, spring and summer show the strongest decreases in snow-cover extent. Satellite observations of snow-cover extent show a...

Projected Arctic annual land temperature increases for the first half of the 21st century relative to the average temperature for 1980–99. The average of the IPCC models (the blue line) shows an increase of 3ºC by 2050. The averages of the runs from each of the 12 models show increases from 2–4ºC, the range of uncertainty in these model projections.

Evidence from tree rings and other temperature proxies suggests that during the previous 500 years global temperatures were 1.0ºC cooler than those of the 20th century during a period roughly from 1300 to 1870 – known as the Little Ice Age. While overall temperatures during the Little Ice Age were cooler than now, there was much year-to-year variability and some warm periods. The coldest part of the Little Ice Age, from 1645 to 1715, was also a t...

The figure shows rates at which the ice-sheet mass was estimated to be changing based on radar-altimeter data (black), mass-budget calculations (red), and satellite gravity measurements (blue). Rectangles depict the time periods of observations (horizontal) and the upper and lower estimates of mass balance (vertical). Measurements by satellite techniques based on gravity indicate mass loss at a rate of 138 ± 73 billion tonnes per year during 200...