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Posts tagged with "glaciers"

Land of Ice & Fire, Jökull & Eld

Thursday, November 4, 2010 5:32:56 PM

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A few Icelandic words have turned up in the news this year. I happen to understand few of them, but don’t ask me questions about the grammar. Fjall, jökull, vatn and hlaup (mountain, glacier, lake and run/flood) are probably among the better known. Oddly enough the Icelandic word for volcano is seldom seen in non-Icelandic media - eldfjall, meaning mountain of fire. The word for crater might also be a candidate for wider use: gígur (pl.: gígar). USGS has a useful list of Icelandic geoscience terms.



Vatnajökull is the largest glacier in Iceland. Vatna is a form of vatn, in which we recognise the English word water, but it also means lake. In the plural vatn becomes vötn in nominative and accusative, vötnum in dative, and vatna in genetive (of lakes). So Vatnajökull means Glacier of Lakes. Vatnajökull is located in the south-east of the island, covering more than 8% of the country. With an area of 8,100 km², it is the largest ice cap in Europe by volume (3,100 km³) . On 7 June 2008, it became a part of the Vatnajökull National Park (marked as “Vatnajokulsthjodgardur”, its Icelandic name, on the Google map at the bottom of this post. The average thickness of the ice is 400 m, with a maximum thickness of 1,000 m. Iceland's highest peak, Hvannadalshnúkur (2,109.6 m), is located in the southern periphery of Vatnajökull, near Skaftafell National Park.



Seven volcanoes are situated underneath the Vatnajökull ice-cap and most of them are active volcanoes. Grimsvötn volcano is together with Hekla, Iceland's most active volcano since the Middle Ages. Grimsvötn last erupted in 1996, in 1998 and yet again in 2004 - there are sign that it will erupt again this year (2010). You have by now noubt realised that Grimsvötn are lakes. In fact Vtanajökull covers several sub-glacial lakes (hence the name). Grímsvötn are situated in a caldera, where only the southern rim of the 6 x 8 km caldera is exposed. The mountain is known as Grímsfjall (Grims mountain), and the volcano is also known under this name (Grímsfjall) The geothermal area in the caldera causes frequent jökulhlaups.



Jon Frimann is closely following the evolution on his blog Iceland Volcano and Earthquake Blog. Some of you may have noticed that he once referred to the situation with this heading “Glacier flood has started from Gímsvötnum”, where he indeed uses the dative (plural): vötnum.

If it comes to a jökulhlaup it will run southwards through an unpopulated area with extremely low risk of any personal damage. It may however destruct bridges and seriously damage the east-west road visble on the Google map below. An eruption will probably only emit ashes into the air, and unless abnormal weather situations should arise, it should not disturb the international air traffic.


Location of Grímsvötn = 64° 25′ 12″ N, 17° 19′ 48″ W



In Danish:
http://borsen.dk/nyheder/oekonomi/artikel/1/194616/vulkanudbrud_kan_vaere_paa_vej_i_island.html
http://www.dr.dk/Nyheder/Udland/2010/11/01/181038.htm
http://ing.dk/artikel/113574-den-islandske-vulkan-grimsvtn-taet-paa-udbrud



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Climate Change and Asian Water

Monday, June 14, 2010 9:51:37 AM

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Global warming is expected to shrink glaciers in the Tibetan plateau and adjacent mountain ranges, including the Himalayas, in Central Asia. This area is the source area of the five major rivers of Asia: the Indus, Ganges, Brahmaputra, Yangtze, and Yellow rivers. More than 1400 million people (roughly a fifth of humanity) depend on water from these rivers.



A study published in the 11 June 2010 issue of the journal Science show that melt-water is extremely important in the Indus basin and important for the Brahmaputra basin, but only plays a modest role for the Ganges, Yangtze and Yellow rivers. The study found that in the Indus and Ganges basins, glacial ice contributes only about 40% of the total meltwater, with the rest coming from seasonal snows. In the other three rivers its contribution is even lower.

I suppose that there is a small misprint or typo in the following sentence:

“...the Indus: Discharge generated by snow and glacial melt is 151% of the total discharge naturally generated in the downstream areas. In the Brahmaputra basin this amounts to 27%.”


I’ll leave it to you to wonder over the 151%!

Climate change will have two effects. One will be to reduce the contribution of glaciers to total run-off. The other will be to change weather patterns, including rain and snowfall.

The expected decrease in melt-water from the glaciers will probably be partially compensated for by an increase in precipitation. This means that for the Yellow river, climate change may even yield a positive effect as the dependence on melt-water is low and a projected increased upstream precipitation, when retained in reservoirs, would enhance water availability for irrigated agriculture and food security.

Overall, however, the study concludes that climate change will reduce water supplies enough that by 2050, declines in irrigation water are likely to reduce the number of people the region's agriculture can support by about 60 million — 4.5% of the region's present population.

Rest to say that the results should be treated with caution, because most climate models have difficulty simulating mean monsoon and the interannual precipitation variation.

Reference:
Immerzeel et. al.
Climate Change Will Affect the Asian Water Towers
Science 11 June 2010
Vol. 328. no. 5984, pp. 1382 - 1385
DOI: 10.1126/science.1183188

Science is not Open Acces, but the journal is available in many larger (public) libraries.





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Arctic And Greenland Ice Melting At Shocking Speed

Thursday, September 3, 2009 7:51:41 PM

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Arctic and Greenland ice is often in the news. With good reason. Some years from now on it may be history, as the ice is melting extremely fast. The news brought by redOrbit on 2 and 3 September 2009 was bad news.

On 2 September: “Arctic sea ice thickness down 53 percent”.
U.S. scientists using satellite data and records from cold war submarine missions have found Arctic Ocean ice thickness has declined 53 percent since 1980.

On 3 September: “Greenland Glaciers Melting At Shocking Speed”.

Can it be repeated too often - or often enough - that the fate of the world’s ice sheets remains one of the biggest concerns in the field of climate prediction?


Image Narsaq, Greenland, July 2002 (Ole Nielsen)





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Bursting Glacial Lakes in Nepal

Monday, August 31, 2009 6:55:44 PM

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A glacial lake is a lake formed by the melting of glacier ice. In a time like now with global warming most glaciers on earth are retreating, resulting in more and swelling glacial lakes - lakes that are often formed behind terminal/end moraines, also known as moraine dammed glacier lakes. A serious problem with such lakes is that when the water reaches a certain level the dam will burst and an extremely large amount of water will suddenly flow into lower valleys with potential catastrophic results.

Studies of the past 30 years show that the temperatures in the Himalayas are rising up to eight times faster than the global average. Nepal has more than 2,300 glacial lakes and experts say at least 20 are in danger of bursting. One of them is the Imja Glacier above Dengboche, which is retreating by about 70 metres a year, and the melting ice has formed a huge lake that could devastate villages downstream if it bursts. The Imja lake, that was nonexistent in 1960, is now the second largest glacial lake in Nepal and is considered the most dangerous. It covers almost one square kilometre, and is estimated to hold 36 million cubic metres of water.

Information about how many people would be affected by a glacial lake bursting remains limited, but experts say the floodwaters could reach as far as Nepal's southern planes and beyond. Environment secretary Uday Raj Sharma said last week the bursting of the Imja lake would be like a "Nepalese tsunami," comparing it with the 2004 Indian Ocean disaster in which around 220,000 people died.

Global Warming - Imja Glacier - on YouTube (of November 10, 2007):






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Why are Some Mountains so Low?

Wednesday, August 12, 2009 7:33:40 PM

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There are indications that the general height of mountain ranges is directly influenced by the extent of glaciation through an efficient denudation mechanism. A global analysis of topography shows that variations in maximum mountain height correlate closely with climate-controlled gradients in snowline altitude rather than with tectonic activity.



A new study, published in the journal Nature of 13 August 2009, used radar images of Earth's surface (taken during a NASA space shuttle mission several years ago) and computer models to show that glacial action, governed by climate, is responsible for the height differences in many of Earth's mountain ranges. Glaciers carve mountains down near the poles, while in the tropics, mountains are able to rise much higher in the air.

If the snowline altitude is very high, the glacial buildup will be limited and so little of the mountain will be ground down. On the other hand, if the snow-line altitude is much lower, as is the case nearer Earth's poles, the glaciers will effectively grind the mountain away. So in order to get really high mountains you need a high snowline altitude, otherwise glaciers will basically destroy the mountain at elevations below that.

In the Himalayas the snow-line is nearly at a height of 6.000 metres. In the Alps the snow-line lies at around 3.500 metres, and in Norway the snow-line is at 1.500 metres.

The authors don’t think that it is a coincidence that the high mountains exist around the equator, where the snowline is high. The forces of plate tectonics are still pushing up the crust under high-latitude ranges, but the mountain tops just get removed as quickly by glaciers as they accumulate by plate tectonics.

This way the glacial action explains why in a range like the Andes, which runs north to south, the northern mountains are higher than the southern — glacial action has worn down the southern peaks (because they are at higher latitudes in the southern hemisphere).

If the climate stays warmer for many thousands of years, mountains might become slightly higher.

Reference:
Egholm et al.
Glacial effects limiting mountain height
Nature 460, 884-887 (13 August 2009)
doi:10.1038/nature08263



In Danish:




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Melting Details

Sunday, August 9, 2009 7:22:32 AM

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At the so-called Last Glacial Maximum (LGM) the ice sheets grew to their maximum positions between 33,000 and 26,500 years ago due to decreases in northern summer insolation, tropical Pacific sea surface temperatures, and atmospheric CO2. Nearly all ice sheets were at their maximum extent from 26,500 to some 19,000-20,000 years ago.

Some key questions that remain widely debated are what initiated the last deglaciation of the global ice sheets and what was their subsequent role during deglaciation in climate change, questions may be best assessed from the record of individual ice sheets rather than the integrated record.

In a study published on 7 August 2009 in the journal Science Clark et al. compiled and analyzed more than 5000 dated ages in order to develop a record of maximum regional ice extent around the time of the Last Glacial Maximum.

There is considerable regional variability in the timing of when ice sheets (and various sectors of ice sheets) first reached their local last glacial maxima. mountain glaciers were near or at their maximum extent by around 30,000 years ago. The onset of Northern Hemisphere deglaciation 19,000 to 20,000 years ago was induced by an increase in northern summer insolation, providing the source for an abrupt rise in sea level.

The authors have shown that the duration of the LGM sea-level lowstand (26.500 to 19,000 years ago) is in excellent agreement with the duration of maximum extent of most of the global ice sheets, suggesting that most of the global ice sheets were in near-equilibrium with climate during this 7500-year interval.

Another paper published on 8 August 2009 in Palaeocanography on the Last Glacial maximum concerns the “Impact of strong deep ocean stratification on the glacial carbon cycle”. During the Last Glacial Maximum, the climate was substantially colder and the carbon cycle was clearly different from the late Holocene (the Holocene is the geological epoch after the Ice Age, which means that it began approximately 11 700 years ago).






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Retreating Svalbard Glaciers

Monday, July 20, 2009 7:40:51 AM

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Svalbard has a total area of 62,248 km2, mostly contained in the four main islands, Spitsbergen, Nordaustlandet, Edgerøya, and Barentsrøya. More than 2,100 glaciers cover 36,591 km2, or about 59 percent of the total area. These are old figures that I have from last century, and will be lower today, as most of these glaciers are retreating. Glaciers in Svalbard and Alaska melt much quicker than glaciers in other Arctic regions, and furthermore Svalbard glaciers melt twice as fast as the ones in Canadian Arctic do.

One of the more famous glacier is the 14th July Glacier, named by French explorers (“Glacier du Quatorze Juillet”). I would guess that the name is due to the “Bastille Day” (commemorating the storming of the Bastille prison on 14 July 1789), and not the day they found it. In Norwegian it is called the “Fjortende Julibreen”. Many (excellent) pictures of this glacier is found on the internet - just do a Google-search - much better than mine, nevertheless here is a panorama of this famous, and rapidly retreating glacier. I took this photo on 6 July 2009 (sorry 8 days too early).

Another retreating glacier in that area is the Lilliehöök-breen or Lilliehook Glacier, that has retreated 4-5 km over the latest 100 years:

These two glaciers are situated near the i on the labelled map below (11 July Glacier out to the Krossfjord and Lilliehook Glacier a bit further to the north in the Lilliehöökfjord, which is the northwestern continuation of the Krossfjord)

Finally two more clearly retreating glaciers at the Krossfjord:



• http://en.wikipedia.org/wiki/File:Spitsbergen_labelled.png

In Norwegian:
• http://www.abcnyheter.no/node/92274
• http://www.troms.com/nyhet/?ID=1485



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Magdalenafjord Svalbard

Tuesday, July 14, 2009 9:11:07 AM

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I am just back from a cruise to Svalbard/Spitsbergen and back along the coast of Norway. Fortunately the weather was excellent. It will take me a few days to get back to normal. In the meantime this picture of our cruise ship anchored in the Magdalenafjord (aka Magdalenabukt).


About 60% of the Svalbard archipelago is covered by ice. The behavior of the Svalbard ice masses is intimately bound up with variations of the ocean-atmosphere-glaciation system and can serve as an indicator of global scale change. Recession of the majority of Svalbard glaciers seems to be the result of recent climatic warming, but reaction of particular glaciers is different. It is noteworthy that about 90% of the Svalbard glaciers are emptying into the sea. Nearly 20% of the total coast length are ice cliffs providing a source for icebergs.

It is much easier to navigate along the west coast than the east coast because a branch of the Gulf Stream is stretching out to west coast of Svalbard.
And, actually new research, which reconstructs the extent of ice in the sea between Greenland and Svalbard from the 13th century to the present indicates that there has never been so little sea ice as there is now. This means that we saw no sea ice on our way to around 80° N (Magdalenafjord: Latitude: 79° 34' 60 N, Longitude: 10° 58' 0 E), apart from extremely small lumps that had just calved off the glaciers. We did however have a clear view to glacier after glacier after glacier after ...

• http://resources.metapress.com/pdf-preview.axd?code=922v30um17650817&size=largest
• http://www.livescience.com/environment/090701-shrinking-sea-ice.html
• http://www.terradaily.com/reports/The_Least_Sea_Ice_In_800_Years_999.html



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Third Pole Melting

Sunday, April 5, 2009 7:54:30 AM

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I must admit that although I have seen plenty of glaciers in places like Norway, the Alps, Canada, Alaska, South America and not least Greenland, I have never been to the Himalayas or the Tibetan Plateau. I have seen numbers from 3,000 to 45,000 glaciers for the area, but whatever the number nowhere else on Earth outside of Greenland and Antarctica is there such a concentration of freshwater, stored as ice. Because of the vast and massive glacial ice sheets the Tibetan Plateau is often called the “Third Pole”.

Some of the world’s most populated areas and states are dependent on the water supply from the roof of the World - coming at the right speed, not too much or too little at a time. We are talking about something like 2 billion people relying on the water flowing to the oceans via major rivers like the Yangtze, Yellow River, Brahmanputra, Ganges, and Mekong - indeed some of the largest rivers in Asia. But the glaciers are shrinking, and shrinking fast. Being each individually relatively small, they are melting much faster that the Ice on Antarctica and Greenland.

70% of the water in the river Ganges comes from the Himalayas. 80% of the river water in India is used for irrigation, and it will be necessary to change the agricultural practices. The glaciers function as a kind of water towers. They collect water from the monsoon in the wet season, and release it in the dry season. But how effective they are depends on how much water is in the towers.

Most urban dwellers on the southern side of the Himalayas don’t see a problem. Because of the recent rapid melting, cities have been getting used to excessive freshwater supplies. There is more than enough water in most big cities right now. Let the present financial crisis be a warning. Some day the credits may come to an end. The present tapping of the glacial water tower is tapping a bank account that has built over thousands of years. But that bank account is being rapidly diminished.


The melting of glaciers in the southern slopes of the Himalayas caused by climate change is also being accelerated by the "Asian brown cloud". The Asian brown cloud is a layer of air pollution that covers parts of South Asia, namely the northern Indian Ocean, India, and Pakistan. Viewed from satellite photos, the cloud appears as a giant brown stain hanging in the air over much of Asia and the Indian Ocean every year between January and March.

In a speech a couple of months ago the Chairman of the Intergovernmental Panel of Climate Change (IPCC) Rajendra Kumar Pachauri said that there were 500,000 km2 of glacial cover in the Himalayas in 1995. At the present rate of shrinking, there will be 100,000 by 2030. These glaciers are shrinking at a faster rate than any other in the world. 6 million Tibetans homes are being radically degraded by the thawing.

• http://climatechange.foreignpolicyblogs.com/2009/01/18/the-melting-himalayas/
• http://www.rediff.com/news/2007/nov/26warming.htm
• http://www.indianmuslims.info/news/2008/feb/06/two_billion_face_water_famine_himalayan_glaciers_melt.html
• http://www.screenindia.com/news/melting-of-glaciers-a-cause-for-concern-pachauri/243587/



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Does dust from Patagonia reach Antarctica?

Sunday, March 29, 2009 7:04:39 PM

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Sometimes it does. During the very coldest periods of the last ice age, glaciers in Patagonia (in South America) were at their biggest and released their meltwater, containing dust particles, on to barren windy plains, from where dust was blown to Antarctica. When the glaciers retreated even slightly, their meltwater ran into lakes at the edge of the ice, which trapped the dust, so that fewer particles were blown across the Southern ocean to Antarctica. Therefore the very coldest periods of the last ice age correspond with the dustiest periods in Antarctica's past. At least over the past 80,000 years according to findings published in Nature Geoscience.


Perito Moreno Glacier, in the Southern Patagonian Ice Field

When glaciers retreated near the end of the ice age about 21,000 years ago the airborne dust supply to Antarctica shut off because it ended up trapped in lakes that formed at the end of the glaciers. Release of dust at the coldest peaks was 20-50 times more than now, when many glaciers in Patagonia are in retreat. The dust from the Patagonian glaciers can now be studied in layers of dust in Antarctic ice and tell us more about the climate in the past.

• http://www.eurekalert.org/pub_releases/2009-03/uoe-dms032709.php
• http://www.alertnet.org/thenews/newsdesk/LR529703.htm
• http://www.reuters.com/article/latestCrisis/idUSLR529703
• http://news.bbc.co.uk/2/hi/uk_news/scotland/edinburgh_and_east/7971017.stm



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