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Earth of fire

Actualité volcanique, Articles de fond sur étude de volcan, tectonique, récits et photos de voyage

Articles avec #volcans et climat catégorie

Publié le par Bernard Duyck
Publié dans : #Volcans et climat

In an article in the journal Nature in July, relayed by the News of the CNRS-INSU, climatologists have pointed to an almost systematic response of the North Atlantic Oscillation - NAO / North Atlantic Oscillation - after major volcanic eruptions.
 

Main eruptive phase of Pinatubo for the basic Clark / Philippines - Doc Nasa 12.06.1991

Main eruptive phase of Pinatubo for the basic Clark / Philippines - Doc Nasa 12.06.1991

What is the North Atlantic Oscillation ?

This is an atmospheric and oceanic phenomenon, mainly concerning the North Atlantic, characterized by an up-and-coming air masses, north-south over the Arctic and Icelandic regions towards the subtropical belt, the Azores and the Iberian Peninsula. These air mass movements affects the pressure changes on the ground, changes in the westerly winds and the climate around the Atlantic basin.

It is characterized by an index, the NAO index.

The NAO index is calculated each year from the pressure difference between two cities: Lisbon, in Portugal and Reykjavik, in Iceland, taking the average deviation from January to March.

A positive NAO index means that the pressure during the winter is higher than average in Lisbon, and lower than average in Reykjavik ... with the result, a more powerful Azores anticyclone and a hollow Icelandic depression.

A negative NAO index is the inverse to the Azores anticyclone lower than normal in winter, and an Icelandic depression barely growing.

These pressure changes influence the climate of the northern hemisphere, particularly the European winter climate.

When the pressure difference between the Azores high (A) and the Icelandic Low (D) is lower than usual (NAO -), the storm track moves to the south of Europe - When the pressure difference between the Azores high (A) and the Icelandic low (D) is stronger than usual (NAO +), the storm track moves to Northern Europe. © Pablo Ortega - one click to enlargeWhen the pressure difference between the Azores high (A) and the Icelandic Low (D) is lower than usual (NAO -), the storm track moves to the south of Europe - When the pressure difference between the Azores high (A) and the Icelandic low (D) is stronger than usual (NAO +), the storm track moves to Northern Europe. © Pablo Ortega - one click to enlarge

When the pressure difference between the Azores high (A) and the Icelandic Low (D) is lower than usual (NAO -), the storm track moves to the south of Europe - When the pressure difference between the Azores high (A) and the Icelandic low (D) is stronger than usual (NAO +), the storm track moves to Northern Europe. © Pablo Ortega - one click to enlarge

 Positive and negative NAO - Source: Heinz Wanner, climate Institute of Geography and Meteorology, University of Bern

Positive and negative NAO - Source: Heinz Wanner, climate Institute of Geography and Meteorology, University of Bern

Influence of volcanic eruptions on the European winter climate:

The study highlighted the fact that two years after each of the eleven best known eruptions of the last millennium, the NAO index is almost always positive. The last eruption of Mount Pinatubo in 1991 led to this kind of observation.

The mechanism is not fully understood to date, but is a forecast track to the consequences of a major volcanic eruption on the European winter climate.

 

Sources :

- Actualités du CNRS-INSU" - Prévoir les hivers européens en décryptant 1 000 ans d’histoire climatique - link

- Nature - A model-tested North Atlantic Oscillation reconstruction for the past millenium - by Pablo Ortega, Flavio Lehner, Didier Swingedouw, Valerie Masson-Delmotte, Christoph C. Raible & al.

Nature 523, 71–74 (01 July 2015) | doi:10.1038/nature14518 - link

- Ifremer - l'Oscillation Nord Atlantique - link

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Publié le par Bernard Duyck
Publié dans : #Volcans et climat
Eruption of Eyjafjallajökull in 2010 -  Artic pictures

Eruption of Eyjafjallajökull in 2010 - Artic pictures

Iceland has always been a natural laboratory for the study of climate change. About 10% of its surface is covered with some 300 glaciers ... the global warming makes them lose annually 11 billion tons of ice. This enormous mass that melts not only contributes to the overall increase in sea level, but also to a lifting of parts of Iceland, estimated at 35 mm / year.

A recent study by the University del'Arizona in conjunction with that of Iceland, published in Geophysical Research Letters, based on information from 62 GPS stations, shows a lifting speed and acceleration of the latter on 27 stations, localized predominantly in the center of the island.

Iceland - left, some glaciers (-jökull) among the most important - right, geodetic network GPS (red triangles) used to measure the uplift of Iceland / Credit: Kathleen Compton / UA Department of Geosciences - a click to enlarge Iceland - left, some glaciers (-jökull) among the most important - right, geodetic network GPS (red triangles) used to measure the uplift of Iceland / Credit: Kathleen Compton / UA Department of Geosciences - a click to enlarge

Iceland - left, some glaciers (-jökull) among the most important - right, geodetic network GPS (red triangles) used to measure the uplift of Iceland / Credit: Kathleen Compton / UA Department of Geosciences - a click to enlarge

Iceland - rift zones and central volcanoes - Doc. in Geology of Iceland - Dr. T.Weisenberger

Iceland - rift zones and central volcanoes - Doc. in Geology of Iceland - Dr. T.Weisenberger

With the melting of glaciers, the pressure on the underlying rocks decreases. One of the authors of the study says: "the rocks can remain in solid phase at very high temperature if the pressure is high enough. If you reduce the pressure, you actually lower the melting temperature." ... The result is a sub-surface softer, an increase in the amount of eruptive materials and an easier path to the surface for the magma. A temperature rise due to a drop in pressure is a favorable environment for the merger of mantle rocks, which supply the volcanic magma systems.

The Icelandic history confirms this thought : 12,000 years ago, during the last deglaciation period, the volcanic activity on the island has increased by a factor of thirty. But this took more time than the current melting phase of glaciers boosted by human activities ... an extrapolation allows the research authors to predict an Iceland's uplift ratio of 40 mm per year in the middle of the next decade, releasing more calderas and allowing more rapid renewal of disruptive event of our economy type Eyjafjallajökull, 2010.

 

Fire and ice ... a couple "infernal" - Eyjafjallajökull - 16.04.2010 - photo Marco Fulle

Fire and ice ... a couple "infernal" - Eyjafjallajökull - 16.04.2010 - photo Marco Fulle

Once disturbed the climatic balances, the chain of disasters related to it may take longer.

Many questions remain unanswered : an increase of  the frequency of volcanic eruptions shall be added to droughts, floods, forest fires, rising of sea levels, storms, tornadoes, food loss, species extinction ? ... Will we check it firsthand? ... How fast will the volcanic systems react to the melting of the glaciers?

 

Sources :

- American Geophysical Union – Geophysical Research Letters - Climate driven vertical acceleration of Icelandic crust measured by CGPS geodesy – by Kathleen Compton, Richard A. Bennett and Sigrun Hreinsdóttir - link

- Iceland Review - Glacial Melt Lifts Iceland, Triggers Eruptions - link

- Time Science - How Climate Change Leads to Volcanoes - link

- The Royal Society - How will melting of ice affect volcanic hazards in the twenty-first century? - link

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Publié le par Bernard Duyck
Publié dans : #Volcans et climat

The mid-Arctic rift has long been considered geologically inactive ... is it because of its retracted position, its significant ice cover, or its small spacing ratio (0.05 cm / year) and low seismicity .

The Gakkel Ridge rift was hit by an earthquake of M 4.5 March 6, 2014; although with moderate magnitude, this earthquake is associated with a large release of methane into the atmosphere suggesting that the fault movement is not limited to the epicenter but affect the entire fault system of the Gakkel Ridge, where hydrothermal vents are documented, but little is known about the number and distribution.

This information shows that this vent system is a source of heat and fluids powerful, which can influence the climate of the Arctic and the melting of the ice cap.
The Mid-Arctic rift and its various basins and ridges

The Mid-Arctic rift and its various basins and ridges
The Mid-Arctic rift and its various basins and ridges

The Mid-Arctic rift and its various basins and ridges

Research on the Gakkel Ridge began in 1999 when a nuclear submarine has detected the presence of active volcanoes along the rift.

In 2001, the icebreakers allowed to harvest rock samples and observing many hydrothermal vents.

The Woods Hole Oceanographic Institute (WHOI) expedition in 2007 discovered unconsolidated pyroclastic deposits, indicating that a recent and strong submarine eruption marked a significant portion of the Gakkel Ridge. Chemical analysis of deposits indicates an instability of the volcanic beds more than ten times higher than the results achieved on the deep oceanic rift systems. Microbiological analysis also shows chemosynthetic life known to be associated with hydrothermal vents.

Earthquakes along the Mid-Arctic Ridge system (red dots) and installation sites of seismometers (triangles) - doc Awi.de

Earthquakes along the Mid-Arctic Ridge system (red dots) and installation sites of seismometers (triangles) - doc Awi.de

 Pillow lava sample taken from the Gakkel Ridge - photo Hannes Grobe / Alfred Wegener Institute

Pillow lava sample taken from the Gakkel Ridge - photo Hannes Grobe / Alfred Wegener Institute

Pyroclatic deposits photographed and collected during the WHOI expedition July 2007 on the Gakkel Ridge - a. pyroclastic materials overcame a pillow lavas structure - b. Talus of blocks presumably representing the ejecta of a vulcanian explosion of the volcano Oden - c. pyroclastic materials, glassy, and granular - d. fragment of the wall of a bubble from the pyroclastic deposit - Doc. Sohn et al. / WHOI / GVP

Pyroclatic deposits photographed and collected during the WHOI expedition July 2007 on the Gakkel Ridge - a. pyroclastic materials overcame a pillow lavas structure - b. Talus of blocks presumably representing the ejecta of a vulcanian explosion of the volcano Oden - c. pyroclastic materials, glassy, and granular - d. fragment of the wall of a bubble from the pyroclastic deposit - Doc. Sohn et al. / WHOI / GVP

On the left, cross section of the dorsal Gakkel - right, another cut of the ridge and its surroundings (exaggerated) - a click to enlarge - Doc. Hannes Grobe, Alfred Wegener Institute - own work, data from POLARSTERN Expedition ARK-VIII3 in 1991.On the left, cross section of the dorsal Gakkel - right, another cut of the ridge and its surroundings (exaggerated) - a click to enlarge - Doc. Hannes Grobe, Alfred Wegener Institute - own work, data from POLARSTERN Expedition ARK-VIII3 in 1991.

On the left, cross section of the dorsal Gakkel - right, another cut of the ridge and its surroundings (exaggerated) - a click to enlarge - Doc. Hannes Grobe, Alfred Wegener Institute - own work, data from POLARSTERN Expedition ARK-VIII3 in 1991.

... This means that the spreading ratios and seismic activity are not necessarily correlated with the intensity and distribution of the heat flow, and these findings is to apply to all the deep ocean rifts.

Too few climatologists considered the heat induced at the Medio-Arctic rift as a possible explanation of the glacial melting in the Arctic, and its connection with the subglacial planktonic proliferation recently discovered.

 

Sources :

- Climate change dispatch - Update on Geothermal Heat and Arctic Ocean Sea Ice Melt - link

- Global Volcanism Program – East Gakkel ridge at 85 E – link

- WHOI – Dive discover expedition 11 - link


 

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Publié le par Bernard Duyck
Publié dans : #Volcans et climat
Drought in Singapore, where the evergreen city has seen his lawns become redheads - photo cyriljeannesingapour / wordpress March 2014

Drought in Singapore, where the evergreen city has seen his lawns become redheads - photo cyriljeannesingapour / wordpress March 2014

The action of volcanic eruptions on climate, through stratospheric emissions of sulfur dioxide and subsequent sulfuric acid aerosols on the temperature factor, is demonstrated.

Another effect on the local climate is highlighted by Wyss Yim Wai- shu , a professor of Earth Sciences at the University of Hong Kong and Vice-President of Unesco team for climate change.

Eruptions in late 2013 / early 2014 in Indonesia are responsible for drought in Singapore, Hong Kong and southern China . Eruptive plumes from Sinabung and Kelud both reached the stratosphere, changing on the way the temperature of the surrounding air and the movement of air masses. Due to the coastal location of Hong Kong and Singapore on the edge of the vast Asian continent , a change in the usual wind direction created conditions conducive to drought. The authorities of Selangor, Malaysia 's most populous province , began to ration the water . The Environment Agency of Singapore states that the drought will last until mid -March.

The eruptive plume of the Sinabung 2013.11.14 - Credit @ anthonywx - Twitter

The eruptive plume of the Sinabung 2013.11.14 - Credit @ anthonywx - Twitter

It is also based on the history of other major eruptions in 1963, when the Agung volcano erupted on the island of Bali ( VEI 5 / GVP ) , southern China experienced one of the worst droughts in its history, and water had to be rationed in Hong Kong.

In 1991, the eruption of Mount Pinatubo in the Philippines 
( VEI 6 / GVP) was followed by a period of minimal rainfall and drought noted in  Hong Kong.

May 1963 - Gunung Agung erupted on Bali - photo D. Mathews

May 1963 - Gunung Agung erupted on Bali - photo D. Mathews

He also noted that according to the time of the eruption , its location and  his explosivity index, an eruption can cause flooding by cons .
That of El Chichon in 1982 in Mexico, widespread a volcanic cloud over the south China Sea ... and Hong Kong recorded its second wettest year.

The volcano- climate , a science complex and complicated by the intervention of many environmental factors , has a huge future field investigation !

To be continued ...

 

Sources :

- S. China morning post - Indonesian volcanic eruptions may cause southern China drought, expert says .

- Global Volcanism Program - Agung - Pinatubo - El Chichon.

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