«We're trying to quantify the water flow, the water chemistry and then the vegetation that's in the basin, the species that are there, all the way from
the glacier terminus down to the ocean,» O'Neel explained.
First, it provides a compilation of global trends in
glacier terminus positions since 1600 A.D. Second, it uses this compilation to create a new estimate of global temperature change.
The glacier terminus region also had a consistent velocity of 19 meters / day (maximum of 26 m in glacier center), from season to season and year to year....
To give another, more specific example, at a typical glacier on Mt. Baker, in Washington State, a summer temperature increase of 1 °C translates to a ~ 150 m increase in the altitude of the equilibrium line (the point where annual ice accumulation = annual loss), and a resulting ~ 2 km retreat of
the glacier terminus.
The glacier terminus region also had a consistent velocity of 19 meters / day (maximum of 26 m in glacier center), from season to season and year to year, the glacier seemed to be in balance, as I noted in a 1989paper.
Their observations were that the region of lightly grounded ice at
the glacier terminus is extending upstream, and the changes inland are consistent with the effects of a prolonged disturbance to the ice flow, such as the effects of ocean - driven melting.
In commenting on their findings, the three researchers write that «the large number of stable
glacier termini and glacier advances is influenced by positive glacier mass balances in the central Karakoram during the last decade,» citing Gardelle et al. (2012, 2013) and Kaab et al. (2012), which they indicate is «induced by increasing winter precipitation and decreasing summer temperatures since the 1960s,» citing Archer and Fowler (2004), Williams and Ferrigno (2010), Bolch et al. (2012), Yao et al. (2012) and Bocchiola and Diolaiuti (2013).
That can increase the sea surface temperature and the air temperature, leading to more rapid melting and thinning at
the glacier terminus.
Multi-temporal satellite products and topographic maps were used for
glacier terminus, surface and snowline altitude (SLA) analysis from 1958 to 2011.
Multi-temporal satellite products and topographic maps were used for
glacier terminus, surface and [continue reading...]
On
each glacier the terminus location is surveyed from a fixed benchmark location beyond the terminus.
If the combination of climate and ice dynamics determines that the glacier is advancing, the advance of
the glacier terminus expands the overall glacier area.
Not exact matches
More specifically, using digital scans of paper maps based on aerial imagery acquired by the U.S. Geological Survey, along with modern - day satellite imagery from a variety of platforms, the authors digitized a total of 49 maps and images from which they calculated changes in the
terminus positions, ice speed, calving rates and ice front advance and retreat rates from 34
glaciers in this region over the period 1955 - 2015.
A small, frozen lake sits at the left - hand
terminus of the
glacier.
The exhibition also includes an image of the
terminus of the Piedras Blancas
glacier, revealing the almost lunar - like landscape of the rocky, barren ground remaining as the
glacier recedes.
Calving from the floating
termini of outlet
glaciers and ice shelves is just the beginning of an interesting chain of events that can subsequently have important impacts on human life and property.
In 2002, the 12 km (7.5 mile) long floating
terminus of the
glacier entered a phase of rapid retreat, with the ice front breaking up and the floating
terminus disintegrating and accelerating to a retreat rate of over 30 m (100 ft) per day.
The issue, as I take it, is whether or not the
glacier has dug a fairly deep submarine canyon, one which the
terminus still occupies.
In the U.S. this is perhaps most famously observed in Glacier National Park, where the
terminus of
glaciers have retreated by several kilometers in the past century, and could be gone before the next century (see e.g. the USGS web site, here, and here).
In 2001 - 2005 the
glacier retreated 7 km and accelerated from 20 m / day to 33 m / day, while thinning up to 130 meters in the
terminus region.
If the Jakobshavn effect is the key the velocity will propagate up -
glacier, the
terminus velocity will be impacted by tides, and there will be no seasonal cycle.
In 1993 the
terminus was advancing (I walked from grass - covered moraines onto the ice surface) but all the water from the snout was flowing back up -
glacier.
Equivalently, while the increase in
terminus speed and the
glaciers overall maximum speed may remain under a factor of five, as the
terminus retreats farther inland where the speeds now are comparatively slow, the relative speedup is much greater (e.g., if the
terminus retreated to M26 with a speed of 16 000 m yr − 1, this would represent a twelve-fold speedup).
If the Jakobshavn effect is the key the velocity increase will propagate up -
glacier, there will be no seasonal cycle, and thinning and acceleration would be greatest near the
terminus.
We have many temperate
glaciers that rival the size of the
terminus reach of many Greenland
glaciers and the ice is somewhat but not greatly weaker.
In a recent paper in press in the Journal of Glaciology Ian Howat and others examined changes in
terminus position, surface elevation and flow on 32
glaciers along the southeast coast of Greenland from 200-2006.
Terminus behavior and response time of North Cascade
glaciers, Washington U.S.A. Journal of Glaciology 47, 497 - 506.
The
terminus behavior and response time of North Cascade
glaciers.
The resultant
glacier thinning, particularly pronounced near the
terminus, has caused extensive
glacier retreat.
All of Norway's
glaciers completely disappeared at least once, 11,39 and Greenland's greatest
glaciers, like the Jakobshavn, remained much further inland than now observed.29 Like many northern
glaciers, Jakobshavn had only recently advanced past its present
terminus during the unprecedented cold of the Little Ice Age.
The average
terminus retreatment of analysed 29
glaciers was about 372 37 m (7.0 m a1) in 1958 to 2011 with retreat rate of 6.1 1.9 m a1 in 1958 - 75 and nearly its double in 2008 - 11.
«More than 65 % of the monsoon - influenced
glaciers that we observed are retreating, but heavily debris - covered
glaciers with stagnant low - gradient
terminus regions typically have stable fronts,» the authors write, adding that «In contrast, more than 50 % of observed
glaciers in the westerlies - influenced Karakoram region in the northwestern Himalaya are advancing or stable.»
A
glacier that is approaching equilibrium during retreat will thin mostly near the
terminus, and at some elevation above the
terminus, usually near the equilibrium line or in the lower accumulation zone, there will be comparatively little thinning (Schwitter and Raymond, 1993).
Howat and others (2008) examined changes in
terminus position, surface elevation and flow on 32
glaciers along the southeast coast of Greenland from 2000 - 2006.
We often focus on
terminus change of a
glacier which tells us how the
glacier is currently responding to recent climate.
Measurements of
glacier discharge are monitored on surface drainage basins on
glaciers and beyond the
terminus of
glaciers.
We are still left with the main cause of
glacier acceleration in Greenland resulting from dynamic thinning of the
terminus zone of the marine terminating outlet
glacier reducing the effective bed pressure, allowing acceleration — the Jakobshavn effect.
From 2000 to 2005, Kangerdlugssuaq
glacier was the fastest - moving
glacier on Greenland, retreating around eight to nine miles (13 to 14 kilometers) per year.2 The end (
terminus) of the
glacier not only retreated from the ocean but also thinned by more than 820 feet (250 meters) during that period.2
The ice sheet loses most of its mass on the perimeter, through a dozen relatively fast - moving
glaciers that have recently become thinner, significantly increased their rates of retreat, and broken up at the ocean end (the
terminus).
Scientists have recently observed major changes in these
glaciers: several have broken up at the ocean end (the
terminus), and many have doubled the speed at which they are retreating.2, 5 This has meant a major increase in the amount of ice and water they discharge into the ocean, contributing to sea - level rise, which threatens low - lying populations.2, 3,5 Accelerated melting also adds freshwater to the oceans, altering ecosystems and changing ocean circulation and regional weather patterns.7 (See Greenland ice sheet hotspot for more information.)
During the same period, the
terminus of the
glacier thinned.2 The correlation of these glacial changes with rising temperatures implies that warming influences
glacier motion almost immediately.1, 2,7,8
These
glaciers do have calving
termini, but lack the large fast flowing feeder tongues extending into the
glacier.
Each of these
glaciers is fast - flowing at the
terminus; the fast flow section extends inland into the ice sheet up a sub-glacial trough.
A small, frozen lake sits at the left - hand
terminus of the
glacier.
Like Jakobshavn Isbræ, many of Greenland's
glaciers have broken up at the ocean end (
terminus), 2 and many have doubled in speed.2, 4
2001: with Cliff Hedlund: The
terminus behavior and response time of North Cascade
glaciers.
The total area of
glacier ice left including the stagnant section by the northern
terminus is 0.9 km2 less than 30 % of the area of just 30 years ago.
Glaciers are not just retreating at the
terminus, lateral and even retreat at the head of the
glacier can also be substantial.
Terminus of
glacier and sea ice are at top left.