Over thousands of years, the layers of snow build up, forming
a flowing sheet of ice thousands of feet thick and tens to thousands of miles across.
Not exact matches
Stewart Jamieson from Durham University in England and his colleagues made the discovery by looking for subtle changes in the
ice sheet's surface shapes, developed as a result
of ice flowing over diverse topography.
Studying surging glaciers could also offer insights into grander - scale
ice flows with global consequences: the movements
of the
ice sheets in Antarctica and Greenland, which can change abruptly, altering the
ice discharges that affect sea level.
The ebb and
flow of lakes such as Whillans are thought to influence the movement
of the overlying
ice sheet.
Lacking many
ice shelves to stem its flow, the glacier is particularly vulnerable to warming, part of the so - called weak underbelly of the West Antarctic Ice She
ice shelves to stem its
flow, the glacier is particularly vulnerable to warming, part
of the so - called weak underbelly
of the West Antarctic
Ice She
Ice Sheet.
The shelves act as a buttress to the «grounded»
ice, helping slow the
flow of the
ice sheet's glaciers into the ocean.
As an example, Howat pointed to the portion
of the mosaic showing Jakobshavn Glacier, the fastest -
flowing glacier in the Greenland
Ice Sheet.
«In that crack you have strong tidal
flow, so it would be interesting to see what a real
ice sheet does in an environment that's analogous in terms
of the amplitude
of the stresses and the temperatures
of the
ice,» Kite said.
The digitized data extend the record
of changes at the bottom
of the
ice sheet, such as the formation
of channels as Antarctica's
ice flows, by more than two decades.
Today, as warming waters caused by climate change
flow underneath the floating
ice shelves in Pine Island Bay, the Antarctic Ice Sheet is once again at risk of losing mass from rapidly retreating glacie
ice shelves in Pine Island Bay, the Antarctic
Ice Sheet is once again at risk of losing mass from rapidly retreating glacie
Ice Sheet is once again at risk
of losing mass from rapidly retreating glaciers.
A hundred kilometers wide, this
ice sheet, unlike most
of its peers, is actually growing instead
of melting, because it has slowed its
flow toward the sea in recent decades.
«This new, huge data volume records how the
ice sheet evolved and how it's
flowing today,» said Joe MacGregor, the study's lead author, a glaciologist at The University
of Texas at Austin Institute for Geophysics (UTIG), a unit
of the Jackson School
of Geosciences.
«Very old
ice probably exists in small isolated patches at the base
of the
ice sheet that have not yet been identified, but in many places it has probably melted and
flowed out into the ocean.»
the south - bound expedition had cleared that vast plain
of floating
ice which
flows down from the great mountains
of the interior and covers the southern part
of Ross Sea throughout an area above 20,000 square miles with an
ice sheet approximately 800 feet in thickness, and had begun to climb the heights which form the mountainous embayment at the head
of Ross Sea.
The way in which water
flows beneath the
ice sheet strongly influences the speed
of ice flow, so the existence
of other lakes will have implications for the future
of the
ice sheet.
Because the way in which water moves beneath
ice sheets strongly affects
ice flow speeds, improved understanding
of these lakes will allow us to predict more accurately how the
ice sheet will respond to anticipated future warming.»
Subglacial lakes are likely to influence the
flow of the
ice sheet, impacting global sea level change.
These two glaciers have been described as the «weak underbelly»
of the
ice sheet because surges in the
ice flow there could theoretically cause the rapid disintegration
of the entire West Antarctic
ice sheet.
In fact, learning about the lakes and rivers could shed light (albeit from a very dark place) on weighty matters ranging from
ice -
sheet stability — how much do the lakes enhance the
flow of ice toward the sea?
«Modelers need an estimate
of the heat
flow, and they need to know something about the geological conditions at the bottom
of the
ice sheet in order to estimate drag.
When the Gravity Recovery and Climate Experiment (GRACE) satellites began measuring gravity signals around the world in 2002, scientists knew they would have to separate mass
flow beneath the earth's crust from changes in the mass
of the overlying
ice sheet.
Hawkings and his collaborators spent three months in 2012 and 2013 gathering water samples and measuring the
flow of water from the 600 - square - kilometer (230 - square - mile) Leverett Glacier and the smaller, 36 - square - kilometer (14 - square - mile) Kiattuut Sermiat Glacier in Greenland as part
of a Natural Environment Research Council - funded project to understand how much phosphorus, in various forms, was escaping from the
ice sheet over time and draining into the sea.
The continually dropping slope helps explain why northern Greenland, unlike Antarctica, has no large subglacial lakes: Meltwater that either forms at the base
of Greenland's
ice sheet or ends up there after draining from the
ice sheet's upper surface
flows away uninterrupted.
The team found layers
of sediment and rocks that built up over time, recording the
flow of the
ice sheet and reflecting climate change.
Researchers also found that the young
ice sheet was much wetter than it is today, with meltwater from the surface
flowing into a network
of channels beneath the
ice.
In a finding offering another sea - level rise warning, scientists yesterday reported the existence
of deep, canyon - like valleys in the bedrock underneath the Greenland
ice sheet that could facilitate the extensive
flow of ice into the ocean.
Not only are
ice sheets in Greenland and Antarctica breaking up faster than scientists expected, but more
of their melt water is
flowing into oceans, he said, which will raise sea levels by 3.3 feet (1 meter) by 2100.
Increased
ice flow in this region is particularly troubling, Khan said, because the northeast
ice stream stretches more than 600 kilometers (about 373 miles) into the center
of the
ice sheet, where it connects with the heart
of Greenland's
ice reservoir.
The pressure
of the
ice sheet constrains the lava
flow, and glacial meltwater chills the erupting lava into fragments
of volcanic glass, forming mounds and ridges with steep sides and flat tops.
Since so much
of the
ice sheet is grounded underwater, rising sea levels may have the effect
of lifting the
sheets, allowing more - and increasingly warmer - water underneath it, leading to further bottom melting, more
ice shelf disintegration, accelerated glacial
flow, and further sea level rise, and so on and on, another vicious cycle.
One 2004 NASA - led study found that most
of the glaciers they were studying «
flow into floating
ice shelves over bedrock up to hundreds
of meters deeper than previous estimates, providing exit routes for
ice from further inland if
ice -
sheet collapse is under way.»
Based on a model that excludes
ice sheet flow due to a lack
of basis in published literature, it is estimated that sea level rise will be, in a low scenario, 18 to 38 cm (7 to 15 inches) and in a high scenario, 26 to 59 cm (10 to 23 inches).
Either the glaciers would have to
flow into the ocean at unrealistic rates, or rapid melting would have to be triggered over a much larger area
of the
ice sheet than current evidence suggests.
Hindmarsh, R.C.A., Influence
of channelling on heating in
ice -
sheet flows, Geophysical Research Letters, 2001.
But the IPCC specifically excluded the mechanism able to produce the biggest amounts
of water quickly - acceleration in the
flow of ice from the Greenland and Antarctic
ice sheets, the world's two major
ice masses that would between them raise sea levels by about 70m if they completely melted.
Changes in the configuration
of ice stream flow from the West Antarctic Ice Sheet, Journal of Geophysical Research, 101 (B3), p. 5499 - 55
ice stream
flow from the West Antarctic
Ice Sheet, Journal of Geophysical Research, 101 (B3), p. 5499 - 55
Ice Sheet, Journal
of Geophysical Research, 101 (B3), p. 5499 - 5504.
Changes in the configuration
of ice stream flow from the West Antarctic Ice She
ice stream
flow from the West Antarctic
Ice She
Ice Sheet.
Changes in the configuration
of ice stream
flow from the West Antarctic
ice sheet.
Major increases would have to be fuelled by a faster
flow of glaciers on the Greenland or Antarctic
ice sheets.
Anandakrishnan, S., R.B. Alley, R.W. Jacobel and H. Conway, The
flow regime
of ice stream C and hypotheses concerning its recent stagnation, in R.B. Alley and R.A. Bindschadler, eds., The West Antarctic Ice Sheet: Behavior and Environment, American Geophysical Union, Antarctic Research Series, v. 77, p. 283 - 296 (200
ice stream C and hypotheses concerning its recent stagnation, in R.B. Alley and R.A. Bindschadler, eds., The West Antarctic
Ice Sheet: Behavior and Environment, American Geophysical Union, Antarctic Research Series, v. 77, p. 283 - 296 (200
Ice Sheet: Behavior and Environment, American Geophysical Union, Antarctic Research Series, v. 77, p. 283 - 296 (2001).
A new numerical model
of coupled inland,
ice stream, and
ice shelf
flow and its application to the West Antarctic
ice sheet, JGR.
Caption: Visualisation
of ice flow in the Antarctic
ice sheet model PISM - PIK.
Dan, I know virtually nothing about
ice sheet dynamics but even I can understand that, even assuming no lubrification or sliding at the base, lateral
ice flow is not going to be caused by the weight
of the
ice at the center.
They are based on computer simulations
of the Antarctic
ice flow using improved data
of the ground profile beneath the
ice sheet.
We suggested that, given the documented
flow of water beneath the
ice sheet, perhaps sub-glacial rivers carried in the microbes, and Tranter responded, «People would have laughed at you a decade ago, but there is a river system under the
ice sheet.
«Most
ice cores are collected from the middle
of the
ice sheet where it rarely ever melts, or on the
ice sheet edge where the meltwater
flows into the ocean,» Karina Graeter, the lead author
of the study as a graduate student in Dartmouth's Department
of Earth Sciences, said in a statement.
Dupont T, Alley R. Assessment
of the importance
of ice ‐ shelf buttressing to
ice -
sheet flow.
The MISI is based on a number
of studies that indicated the theoretical existence
of the instability... The most fundamental derivation, that is, starting from a first - principle
ice equation, states that in one - dimensional
ice flow the grounding line between grounded
ice sheet and floating
ice shelf can not be stable on a landward sloping bed.
Holocene accumulation and
ice flow near the West Antarctic Ice Sheet Divide ice - core site, Journal of Geophysical Research: Earth Surface, 121, p. 1 -
ice flow near the West Antarctic
Ice Sheet Divide ice - core site, Journal of Geophysical Research: Earth Surface, 121, p. 1 -
Ice Sheet Divide
ice - core site, Journal of Geophysical Research: Earth Surface, 121, p. 1 -
ice - core site, Journal
of Geophysical Research: Earth Surface, 121, p. 1 - 18.
A
flow cytometric method to measure prokaryotic records in
ice cores: an example from the West Antarctic Ice Sheet Divide drilling site Journal of Glaciology, in press, p. 1 -
ice cores: an example from the West Antarctic
Ice Sheet Divide drilling site Journal of Glaciology, in press, p. 1 -
Ice Sheet Divide drilling site Journal
of Glaciology, in press, p. 1 - 19.