The data revealed that
as glaciers flow faster, they stretch out and thin, which reduces their weight and lifts them farther off the bedrock.
Not exact matches
Howat and his team were able to figure this out by creating high - resolution topographic models of the
glaciers and their boundaries,
as well
as a numerical model of exactly how much water was
flowing off these coastal
glaciers and ice caps — technology that wasn't available back in 1996.
Wahlenbergbreen
glacier in Svalbard, Norway, is seen in September 2013,
as its
flow began speeding up.
Most surges, broadly defined
as a
flow at least 10 and often hundreds of times faster than a
glacier's usual pace of advance, are quieter affairs.
The broad, bright plains known
as Sputnik Planum seem to be covered by nitrogen
glaciers; these
flow gloppily, and quickly erase craters made by crashing asteroids.
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.
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
glaciers.
But now, a vulnerable
glacier on the other side of the island, part of a massive
flow of ice known
as the Northeast Greenland Ice Stream, shows that yet another region of Greenland is feeling the effects of warming oceans.
At the grounding line, the ice detaches from the bedrock and juts out into the water
as a kind of floating ledge, or ice shelf, which helps to stabilize the
glacier and hold back the
flow of ice behind it.
Nonetheless, Khazendar and his colleagues say that two of the
glaciers flowing into Larsen C have already begun to accelerate
as the ice shelf has weakened.
Glaciers around the world are melting and contributing to sea level rise, but scientists still don't quite understand how exactly glaciers give birth to icebergs as they flow into the ocean and l
Glaciers around the world are melting and contributing to sea level rise, but scientists still don't quite understand how exactly
glaciers give birth to icebergs as they flow into the ocean and l
glaciers give birth to icebergs
as they
flow into the ocean and lose ice.
All told, if the eastern and western Antarctic ice shelves were to melt completely, they would raise sea levels by
as much
as 230 feet (70 meters); the collapse of smaller shelves like Larsen B has sped up the
flow of
glaciers behind them into the sea, contributing to the creeping up of high tide levels around the world.
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.
The ordinary meter - or - two - a-year speed of the
glacier's
flow increased roughly tenfold
as it passed over the lakes.
CLIMATE CALAMITIES
As ice shelves on the Southern Antarctic Peninsula weaken,
glaciers flow faster into the sea.
But an ice shelf is thought to act
as a «cork in the bottle,» damming the
flow of the land - based
glacier that slowly feeds the shelf in the sea.
As a result, the ice shelf is likely to both thin and
flow faster, the researchers note — and eventually, that could allow the
glacier to slide into the sea.
«
As the
glacier's calving front retreats into deeper regions, it loses ice — the ice in front that is holding back the
flow — causing it to speed up,» Joughin clarifies.
On the
glacier scale, thinning is strongest in the Amundsen Sea embayment (ASE), where it is confirmed
as being localized on the fast -
flowing glaciers and their tributaries (Fig. 3 [below].
Co-author Dr Ivan Haigh, lecturer in coastal oceanography at the University of Southampton and also based at NOCS, adds: «Historical observations show a rising sea level from about 1800
as sea water warmed up and melt water from
glaciers and ice fields
flowed into the oceans.
On the other hand, if the ice shell is sufficiently thick, the less intense interior heat can be transferred to warmer ice at the bottom of the shell, with additional heat generated by tidal flexing of the warmer ice which can slowly rise and
flow as do
glaciers do on Earth; this slow but steady motion may also disrupt the extremely cold, brittle ice at the surface to produce the chaos regions.
However, if
as a consequence of shortening, the
glaciers are also
flowing faster, then we would be seeing another (small) contribution to sea level rise.
A study published in February also documented changes in the
glacier's
flow rate, indicating that little - studied ice shelves are starting to get more attention
as scientists» understanding of ice and satellite coverage improves.
As higher sea levels lifting the
glacier, then the tides would constantly flex the ice tongues breaking and releasing the ice opening up the ice
flow «cork in the bottle».
I suppose that
as the under side of the
glacier melts, the resulting fresh water mixes with the adjacent salt water, making it lighter and causing it to
flow upwards along the under side of the ice.
Pine Island
Glacier, the longest and fastest
flowing glacier in Antarctica, has calved multiple icebergs,
as can be seen in a series of photos.
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glaciers and icecaps.
Whales would surface beside our kayaks, leopard seals would ignore us
as we floated by their ice
flows, penguins would peck at our legs when we explored the sea shore and the icebergs and
glaciers were huge.
As higher sea levels lifting the
glacier, then the tides would constantly flex the ice tongues breaking and releasing the ice opening up the ice
flow «cork in the bottle».
Dr. Rignot recently proposed that unabated warming could result in three feet of global sea rise just from water
flowing off Greenland, three feet from Antarctica and 18 inches
as the remaining alpine
glaciers shrivel away.
Outflow from the ice - dammed lake is estimated to have been 11.3 million cubic meters; the additional 17.5 million cubic meters is due to frictional melting of ice
as the flood traveled in contact with the
glacier, together with an input from base
flow.»
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.
As they emphasize, this applies only in those locations where there are volcanoes, which is certainly not everywhere where fast
glacier flow and thinning is occurring.
However,
as Timothy explained in # 121, in addition to the direct sea level rise that occurs when ice shelves melt, there is a much larger secondary effect, in that ice shelves act
as a brake, greatly reducing the rate of
flow of the
glaciers behind them from the land to the sea; and when ice shelves melt, the rate of
glacier flow increases quite rapidly.
As summer neared an end in 2007, reports from Greenland indicated that the
flow of
glaciers into the sea had accelerated beyond anything glaciologists had thought possible.
A full explanation will require numerical modeling of
glacier flow, but observations to date suggest that ice shelves act
as «braking» systems on the
glaciers behind them.
Advances in
glacier ice
flow mapping using repeat satellite images, and later using interferometric synthetic aperture radar SAR methods, facilitated the mass budget approach, although this still requires an estimate of snow input and a cross-section of the
glacier as it
flows out from the continent and becomes floating ice.
In addition to a groundwater base
flow driving the current steady rise in sea level, meltwater from retreating Little Ice Age
glaciers undoubtedly contributed
as well.
Once the growth of Little Ice Age
glaciers stopped, and groundwater base
flow was no longer offset, we would expect sea levels to rise
as witnessed during the 19th and 20th centuries.
There is a potential difference between the two, in
glacier such
as most marine terminating outlet
glaciers, where the
glacier flow is rapid, acceleration results from retreat and thinning.
In fact in a dry year such
as 1998
glaciers yielded 28 billion gallons of runoff to Baker Lake, while other sources were below average, which amounted to 45 % of the total basin
flow.
In fact in a dry year such
as 1998
glaciers yielded 110 million m3 of runoff to Baker Lake, while other sources were below average, which amounted to 45 % of the total basin
flow (Pelto, 2008).
Yet
as glaciers disappear, dry season river
flow declines.
Usually, surface melt and ice
flow (
as glaciers calve into the sea) are the two ways in which Greenland (and other places, like Canada) contribute water to the ocean.
An instrument called a Vertical Microstructure Profiler — a kind of giant toilet brush that measures subtle fluctuations in the water — detected turbulence amid meltwater
as it
flowed out of a cave beneath the Pine Island Glacier, one of Antarctica's fastest melting
glaciers.
Like the rhythm of retreating and advancing
glaciers, rates of sea level rise have ebbed and
flowed as seen in this graph from the IPCC.
«We all have very nasty fears that the
flows of the Indus could be severely, severely affected by
glacier melt
as a consequence of climate change.
As these
glaciers retreat due to global warming (see Chapter 1), river
flows are increased in the short term, but the contribution of
glacier melt will gradually decrease over the next few decades.
These impressive ice cracks dropping hundreds of metres one day can be gone the next
as they fluctuate with a
glacier's
flow.