Glacier retreat means that glaciers are getting smaller over time. The ice is melting and shrinking, causing the glacier to move back and get smaller.
Full definition
Over long periods, glacial response to climate change becomes obvious
as glaciers retreat and, in some cases, disappear.
But Chinese scientists warn that global warming is main cause
of glacier retreat and the tourism ban will do little to reverse the trend.
Those who legitimately question the case for man - made global warming (AGW) do not question
whether glacier retreat is evidence of global warming.
In the long run
glacier retreat simply results in the reduction of runoff in the summer, when other runoff sources are also depleted.
Global warming must be the primary cause
of glacier retreat, which is occurring on a global scale, but observed rapid melt rates suggest that other factors may be involved.
As glaciers retreat, the ground loses its insulation and becomes more vulnerable to the climate.
According to a recently published paper in the journal Science, (Cook et al., 2016, «Ocean forcing of
glacier retreat in the western Antarctic Peninsula»), between 1945 and 2009 the mean ocean temperature warmed at depths of 150 to 400 meters for about 3 / 4ths of the waters surrounding the western Antarctic Peninsula (AP).
When glaciers retreated thousands of years ago, they trapped relic salt water in depressions that are now high - salinity lakes such as Ace Lake.
Himalayan
Glaciers Retreating at Accelerated Rate in Some Regions but Not Others; Consequences for Water Supply Remain Unclear, Says New Report
But in the Alps, the Industrial Revolution has driven
glacier retreat by an additional mechanism: soot.
Kaser G, Hardy DR, Mölg T, Bradley RS, and Hyera T 2004: Modern
glacier retreat on Kilimanjaro as evidence of climate change: Observations and Facts.
The analysis found three trends: 63 percent of
glaciers retreated from 1974 to 1990, when it was warmer; 72 percent advanced from 1990 to 2000, when it was cooler; and 58 percent advanced from 2000 to 2010, a period that experienced phases of warming and cooling.
He says: «However, as far as the mid-19th century is concerned, forcings due to GHG concentrations are insignificant so we are only left with natural forcings (or causes) as an explanation
for glacier retreat.»
The cave system had been sealed for hundreds of thousands of years, but an opening called the Aach spring made it accessible when
Alpine glaciers retreated northward around 16,000 to 20,000 years ago.
In general,
glaciers retreat due to a combination of rising temperatures and declining precipitation, but the temperature and precipitation records from the Alps indicated that glaciers should have continued advancing until around 1910.
The trend in mass balance is becoming more negative which is fueling
more glacier retreat and thinning note figure at right.
Some argue that the combined increase in temperature and humidity is the major reason for accelerated
tropical glacier retreat in the Andes toward the latter half of the twentieth century.2
Past studies of Antarctica's
accelerated glacier retreat focused on regional trends, a new study now finds continental trends of over ten percent of marine terminating glaciers moving inland.
The Heartland Institute's propagation of the notion that the
Kilimanjaro glacier retreat has been proved to be due to deforestation is even more egregious.
Anthropogenic forcing has likely contributed substantially to widespread
glacier retreat during the 20th century.
In WG1, the statements about
continued glacier retreat are much more general and the rules on citation of non-peer reviewed literature was much more closely adhered to.
And why did
glacier retreat occur more than 3 times faster from the 1860s to 1940s as it has from the 1940s to 2000s?
Before the 20th century, the fastest rate of
glacier retreat reflected in the core was about 8,500 years ago, at a time when the Earth's position relative to the sun resulted in more summer sunlight in the Arctic.
The bold shading in the maps below shows the likelihood of
glacier retreat across the different regions by 2100 (upper map) and 2200 (lower map).
Qualitative indicators like sea ice coverage, spring thaw dates, and melting permafrost provide strong additional evidence that trends have been positive at middle and high northern latitudes, while
glacier retreat suggests warming aloft at lower latitudes.
Dear Kenneth, when it warms,
glaciers retreat until either a new equilibrium between ablation and accumulation is found or until they disappear.
The north - south gradient of
increasing glacier retreat was found to show a strong pattern with ocean temperatures, whereby water is cold in the north - west, and becomes progressively warmer at depths below 100m further south.
As a consequence of temperature increases, the trend in
glacier retreat reported in the Third Assessment Report is accelerating (very high confidence).