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December 27, 2011

Internal erosion of a glacier

                                   Conductos de un glaciar

The glacier in Nepal Ngozumpa winds away from the sixth highest mountain in the world, Cho Oyo.

It is far from being the most beautiful glacier viewing. On the contrary. Is flattened into a layer of rocky debris falling from the cliffs that surround it, giving it an appearance very gray and dirty.

However, much interest is generated Ngozumpa scientist at this time.

The Nepalese Himalayas have been warming at a rate much higher than the global average temperature in recent decades.

Glaciers in most of the region are showing signs of shrinking, reducing its thickness and back, and this is causing a lot of ice melted.

In Ngozumpa of this water collects in puddles on the surface and runs off a series of streams and caves to the lowest point of the glacier.

There, 25 km from the mountain, a huge lake growing behind a mound of fallen rock fragments.

This lake called Spillway, potentially could have 6km long, 1km wide and 100 feet deep.

What is feared is that this large body of water finish opening a breach in the dam of debris and speed ride down the valley, sweeping away the villages on their way to the Sherpa. The threat is not immediate, but it is a situation that warrants monitoring scientists say.

Spy Cameras

One of the researchers working in Ngozumpa is Ulyana Horodyskyj the Cooperative Institute for Research in Environmental Sciences (CIRES, for its acronym in English) at the University of Colorado at Boulder, USA

Horodyskyj is placing remote cameras to monitor surface water or ponds that are supraglaciales over Ngozumpa. Some gaps are small, some large as the size of several football fields.

Horoduskj and was able to establish the dynamic changes that can fill these waters to dry up and fill up quickly.
Volumes can become enormous. On one occasion, cameras spied a lake supraglaciar which lost more than 100,000 cubic meters of water in just two days.

Within five days the lake had recovered more than half of its volume, fueled by the higher waters of the glacier.
"Let's say if I came a week before and one after the lake was dry I would not notice that something had happened because the lake level appeared to be the same,"

"But my photographs I say that something happened. The equivalent of 40 Olympic swimming pools slid down the glacier."

CIRES researcher wants to understand the role these lakes "supraglaciales" in Ngozumpa erosion.

The debris-covered glaciers do not melt the same way that glaciers clean. Overlying rocks, depending on its depth, ice insulated solar radiation. However, if they are removed - as in these lakes swing - the pace of melting will increase.
"The increase in the melting begins in the walls are exposed ice on the lakes," he explains.

"The pace of melting below the debris layer is 2 cm per day, but in these walls is 4 cm per day. As the lake dries exposes the walls that can then be separated"

Horodyskyj means that many of the lakes on the surface of Ngozump are directly connected and while one is empty, maybe another lower elevation lake is being filled. However, the routes followed by the plumbing system are not always obvious.

Within the channels

This is being investigated by Doug Benn of the University Center in Savalbard (UNIS) in Norway.

Benn has been climbing through the vast network of channels divided by the water that flows into Ngozumpa. Some of these "ice pipes" give way to spectacular caves.

"Is that glaciers in this region are melting as a result of global warming, but what is not known which are also being eroded from within as well," he says.

"These glaciers are turning into Swiss cheese, so everything is happening faster than it seems when looking at the surface only."

Dr Benn visits the ducts after the season when the ice melts, when the water stopped flowing. It would be very dangerous to enter the channels in midsummer.

It seems that the channels control the location of some ponds and lakes formed on the surface. It is as if the ducts were the templates.

"There are cracks. As the glacier melts, the roofs of the tunnels in and the ice fall is exposed," said Dr. Benn. "The remains of rocks on its surface melting usually decrease, but the existence of these cracks within Ngozumpa cause it to open and melt faster."

One of his students, Sarah Thompson, is focusing his study on the lowest point of the glacier. This is the place where the water goes down the Ngozumpa joins in the growing Lake Spillway.

It is limited by the moraine, a huge pile of granite fragments dropped by the glacier for millennia.
At this point the glacier remains stationary, not moving. Again the ice walls that line the Lake Spillway becoming separate water and increasing its level.

"We have a fairly short time period - the last 10 years - but it's an exponential growth area," said Thompson, referring to the size of Spillway. "And when we look at other similar lakes in the region, Spillway is about the same kind of path to development. "

"The expansion is far beyond what one would expect the rate of melting ice, glacial ablation and even the separation of icebergs."

"We need to understand the process early so that we can predict quite some time what will likely happen and, if necessary, enter and mitigate its effects before it becomes a danger of importance."

"In my work I try to identify where there may be weaknesses in the moraine dam and have identified a few areas where the future will need to take action."

Spillway is not expected to overflow the short term. It may take two decades or more before it fills up a space for 6km. However, the difficulty of working in the region and to bring heavy equipment to the area means that it is essential to have a long-term strategy for managing the evolution of the lake.

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