Translate

Monday, February 17, 2014

The 1783 Eruption of Laki

File:Laki fissure (3).jpg
Laki, Iceland (Source)

One of the most distructive volcanic eruptions in modern history was the 1783 eruption of Laki in Iceland.

Volcano World gives  a brief synopsis:
The Laki eruption lasted eight months during which time about 14 cubic km of basaltic lava and some tephra were erupted. Haze from the eruption was reported from Iceland to Syria. In Iceland, the haze lead to the loss of most of the island's livestock (by eating fluorine contaminated grass), crop failure (by acid rain), and the death of one-quarter of the human residents (by famine). Ben Franklin noted the atmospheric effects of the eruption (Wood, 1992).

It is estimated that 80 Mt of sulfuric acid aerosol was released by the eruption (4 times more than El Chichon and 80 times more than Mount St. Helens).

The climatic effects of the Laki eruption are impressive. In the eastern United States, the winter average temperature was 4.8 degrees C below the 225 year average. The estimate for the temperature decrease of the entire Northern Hemisphere is about 1 degree C. The top graph shows change in acidity in micro equivalents H+ per kg in the Greenland icecap. The bottom graph represents the winter temperature records in the eastern United States. From Sigurdsson (1982).

The Laki eruption illustrates that low energy, large volume, long duration basaltic eruptions can have climatic impacts greater than large volume explosive silica-rich eruptions. The sulfur contents of basaltic magmas are 10-100 times higher than silica-rich magmas (Palais and Sigurdsson, 1989).
Initially, I want to address a 2011 paper published in Geophysical Research Letters that suggested that the Laki eruption was the not the significant cause of the decline in temperature. Live Science provides a summary:
The eruption of a volcano in Iceland is often blamed for the unusually harsh winter of 1783 to 1784 around the North Atlantic. But new research lays the blame for the extreme cold elsewhere.

Scientists find that the extremes of cold back then might actually have been triggered by the same climate effects potentially responsible for the unusually cold and snowy winter that Europe and North America experienced from 2009 to 2010.

These new findings shed light on how extremes in natural variability in climate have played and still play a key role in our world today, along with any recent global warming effects, the researchers said.

... In the winter of 2009 to 2010, the North Atlantic Oscillation (NAO), a climate phenomenon in the North Atlantic sector, went through a negative phase, meaning less warm air flowed into Europe and more cold Arctic air headed toward North America. At the same time, the El NiñoSouthern Oscillation (ENSO), a climate pattern in the tropical Pacific Ocean, went through a warm phase, which can potentially cause wetter, cloudier winters in northern Europe and enhanced storms to hit the central and southern latitudes of the United States.

After analyzing 600 years' worth of data in tree rings, which preserve details about the climate in which the trees grew, the scientists found that NAO and ENSO conditions during the 1783 to 1784 winter were similar to those seen in the 2009 to 2010 winter. In ranking this kind of combined NAO-ENSO events, the researchers found that the 2009 to 2010 winter showed the strongest combined effects and the 1783 to 1784 winter the second strongest in the past 600 years.

At the same time, their simulations of the effects of the Laki eruption and its dissipation through the autumn of 1783 suggest that it did not play a key role in these events.
Watts Up With That also discusses the 2011 paper. You can get a copy of the 2011 paper here (pdf). However, a subsequent paper in the Journal of Geophysical Research (VOL. 117, D23116, doi:10.1029/2012JD018414, 2012) which rebutted the 2011 paper. The 2012 paper, "Climatic impact of the long-lasting 1783 Laki eruption: Inapplicability of mass-independent sulfur isotopic composition measurements," essentially argues that the prior studies were flawed because they only examined sulphur dioxide concentrations in the norther latitudes, while climate modelling predicted that the SO2 would have been pushed into the middle-latitudes, which, I might add, is supported by the historical record at the time.

However, whatever the cause of the temperature fluctuations, let's look at what happened in 1783-84. Netherland's NRC noted, in an article on an April 2010 eruption in Iceland:
... On June 8, 1783, the Laki volcano erupted and remained active for eight months. Its ash cloud reached as high as 15 kilometres. The poisonous dust that rained down on Iceland killed 10,000 people, a quarter of the island's population at the time.

The Icelandic language even has a word for it: Móduhardbindin, meaning "death by famine caused by poisonous gas". Domestic animals suffered white spots on their skin and burns on their hooves. The little grass that remained turned yellow and pink. Half of all livestock died from poisoning.

Iceland was not the only country where apocalyptic scenes became reality. In the United Kingdom, the summer of 1783 would go down in history as the "sand summer". Large swaths of Europe were enveloped in a thick, permanent, haze. The fog rolled over Bergen in Norway first, followed by Prague and Berlin, and finally, Paris and Rome. With visibility at sea extremely limited, ships remained moored in port. By day, a paltry sun emitted little more light than the moon did by night. Only at sunset and sunrise did it turn a deep crimson red.

Extremely hot summers and cold winters followed, causing crops to fail across Europe. Famine ensued. In the UK alone, 23,000 people died from poisoning in the summer of 1783. In the winter that followed an additional 8,000 succumbed to hunger. In 1784, the United States had its coldest winter ever. Even parts of the Gulf of Mexico froze over. The Mississippi river was covered with ice as far south as New Orleans.

The eruption's effects lasted until 1788. France was plagued by heavy storms. Newspaper reports from the era mention hailstones so big they killed cattle on impact. Harvests failed and famine followed. Grain prices reached record heights. The country's rural populace in particular, which then accounted for 85 percent of the population, rebelled against the bankrupt French monarchy. The Bastille prison was stormed and the Ancien Régime overturned. France would remain a hotbed of unrest for years, long after the Laki volcano in Iceland had already returned to a deep and long-lasting slumber.
The Laki eruption wasn’t really a single event, but rather 8 months’ worth of lava flows and explosions that ejected an astounding ~14.7 km3 of basaltic lava that came out of 140 vents along a 23-km-long set of fissures and cones. ... That volume might be hard to visualize, but 14.7 km3 would pave the entire city of Boston (~232 km2) in ~63 meters deep of basalt. Think of it another way: Kilauea, one of the most active volcanoes on Earth, as erupted ~4 km3 of basalt since 1983. That means that Laki erupted 3.6 times more lava in 8 months than Kilauea as erupted in 30 years. That is pretty remarkable! This doesn’t even take into account that while the Laki eruptions were occurring, nearby Grímvötn was also erupting, possibly as many as 8 times between May 1783 and May 1785. These two events are thought to be related in a single “volcanic-tectonic episode” that fed magma into the Laki fissures and Grímvötn.
... Now, the Laki eruptions had a staggering effect on Iceland itself, in large part due to the volcanic gases released in the eruption and not the lava flows themselves. Sulfur dioxide released by the lava flows stayed close to the ground (within 5 km) in Iceland, creating acid rains that were strong enough to burn holes in leaves, kill trees and shrubs and irritate skin. The eruption released 8 Mt of fluorine, so as that fluorine settled out and was incorporated into grasses, grazing livestock got fluorinosis. Sixty percent of all grazing livestock died due to the effects of the Laki eruptions. The “Haze Famine” as it is called in Iceland killed over 10,000 people (~22% of the population) from famine and disease.

Of the 122 Mt of sulfur dioxide released in the eruption, 95 Mt made it to the upper troposphere and lower stratosphere, so it entered the jet stream and was circulated around the entire northern hemisphere (see right). The haze quickly reached Europe and by July 1, 1783, the haze was noticed in China. There are not many historical records from North America that mention the arrival of the Laki haze, but tree ring records from northern Alaska suggest that July and August 1783 were very cold. The mean temperature in northern Alaska is 11.3ºC, but the mean temperature recorded in May-August 1783 was only 7.2ºC. Russian traders in Alaska noted a population decrease in the years after the eruption while Inuit oral histories do refer to a “Summer that did not come” that could correlate with the Laki eruption as well.

Globally, those 95 Mt of sulfuric dioxide reacted with atmospheric water to form 200 Mt of sulfuric acid aerosols. Almost 90% of that sulfuric acid was removed in the form of acid rain or fogs, while 10% stayed aloft for over a year. This might explain why northern hemisphere temperatures were 1.3ºC below normal for 2-3 years after the eruption. Thordarson and Self (2003) created an excellent figure to show how the sulfur aerosols were dispersed during the eruption (see below), where 80% was part of the explosive phase of the eruption and launched 10-15 km, producing distant haze across the world while 20% came directly from cooling lava flows, so it stayed close to the ground to produce the local haze in Iceland. The sulfuric acid was even damaging to crops in Europe, where noxious dews and frosts (sulfur precipitates) formed. Ash from the eruption was noted as far away as Venice, Italy and many places in between.
See also this short article from Scientific American, noting that the famine after the eruption helped spark the French Revolution. This April 10, 2010, article from the Guardian also notes the devastating consequences to the people of Iceland, as well as the broader global implications:
In Norway, the Netherlands, the British Isles, France, Germany, Italy, Spain, in North America and even Egypt, the Laki eruption had its consequences, as the haze of dust and sulphur particles thrown up by the volcano was carried over much of the northern hemisphere.

Ships moored up in many ports, effectively fogbound. Crops were affected as the fall-out from the continuing eruption coincided with an abnormally hot summer. A clergyman, the Rev Sir John Cullum, wrote to the Royal Society that barley crops "became brown and withered … as did the leaves of the oats; the rye had the appearance of being mildewed".

The British naturalist Gilbert White described that summer in his classic Natural History of Selborne as "an amazing and portentous one … the peculiar haze, or smokey fog, that prevailed for many weeks in this island, and in every part of Europe, and even beyond its limits, was a most extraordinary appearance, unlike anything known within the memory of man.

"The sun, at noon, looked as blank as a clouded moon, and shed a rust-coloured ferruginous light on the ground, and floors of rooms; but was particularly lurid and blood-coloured at rising and setting. At the same time the heat was so intense that butchers' meat could hardly be eaten on the day after it was killed; and the flies swarmed so in the lanes and hedges that they rendered the horses half frantic … the country people began to look with a superstitious awe, at the red, louring aspect of the sun."

Across the Atlantic, Benjamin Franklin wrote of "a constant fog over all Europe, and a great part of North America".

The disruption to weather patterns meant the ensuing winter was unusually harsh, with consequent spring flooding claiming more lives. In America the Mississippi reportedly froze at New Orleans.

The eruption is now thought to have disrupted the Asian monsoon cycle, prompting famine in Egypt. Environmental historians have also pointed to the disruption caused to the economies of northern Europe, where food poverty was a major factor in the build-up to the French revolution of 1789.
You can find more on the fluorine poisoning in this report, "Fluorine poisoning in victims of the 1783-84
eruption of the Laki fissure, Iceland." Alexendra Witze also notes:
In the end, Laki’s effects would spread all the way around the northern hemisphere. Volcanic fluorine settled across the lush pastures of Iceland, poisoning the grass and killing livestock and leading to one of the worst famines in the country’s history. Farther afield, volcanic sulfur first choked people on the ground across Europe — and later, by scattering away the sun’s incoming rays, led to climate change across the Northern Hemisphere for years. Laki cooled parts of the planet in ways that likely shut down the flow of the Nile, and that may have contributed to famine as far away as Japan. Some have gone so far as to attribute the French Revolution of 1789, in part, to Laki’s role in crop failures across France throughout the 1780s. The eruption’s official death toll is around 10,000, but if you add in the distant famines that may be linked to Laki’s climatic effects, something closer to several million people may have died.
(She is probably referencing the Great Tenmei famine in Japan, which was at least partly the result of local eruptions). NASA simulations showed:
In contrast to the cooling over Northern Hemisphere land masses, computer simulations showed the weakening monsoon led to an area of significant warming of 1 to 2 degrees Celsius (1.8 to 3.6 degrees Fahrenheit) over the Sahel of Africa, southern Arabian Peninsula, and India in the summer of 1783. The researchers believe the weaker-than-normal monsoon reduced the cloud cover in the region, allowing more of the sun's energy to reach the surface, raising temperatures and further worsening drought conditions. 
Computer model simulations also showed that this reduction in cloud cover was consistent with a decline in summer precipitation. "Some of the driest weather occurred over the Nile and Niger River watersheds," said Oman. "The relative lack of cloud cover and increased temperature likely amplified evaporation, further lessening water available for run-off." 
To see what effect major high-latitude volcanic eruptions have on rainfall and river levels, the researchers used records on the height of the Nile River that date back to 622 A.D. Record low Nile River water levels occurred in 1783-1784 following the Laki event. Similarly low levels were observed after the Mount Katmai, Alaska, eruption in 1912, when the Niger River was also at a record low. And in 939 A.D. there was also low Nile River flow following the Eldgjá eruption in Iceland. "Our analysis found there is less than a 3 percent chance that the Laki and Katmai low river flow events could be attributed to natural climate variability," said Oman.
In Exodus Lost, by S.C. Compton, writes that "[c]rops could not be grown in Egypt in 1783 or 1784, and by 1785 one-sixth of Egypt's population had starved or fled."  This article from Decoded Science describes:
Because the Laki eruption took place within an era and a geographic location in which written records were kept, researchers know a lot about the environmental impacts. They were extensive: it’s been described on the The Naked Scientist podcast as ‘the biggest atmospheric pollution event in history.’ Benjamin Franklin, at the time living in Paris, wrote of the ‘constant fog’ which shrouded Europe and North America. 
The fog was not the only outcome. The vast quantity of sulphur dioxide which found its way into the atmosphere created acid rain in parts of northern Europe. The eruption also seems to have interfered with climate patterns: in North America, climate records show that the years 1784-86 were abnormally cold – although in Europe the summer of 1783 was exceptionally hot and in Japan, unseasonably wet.

In Iceland, the impacts were particularly severe as concentrations of poisonous gases acted upon the local population and livestock within only few days. Vegetation also became poisoned by the gases and volcanic fallout. The result was famine: estimates suggest that the final toll was up to 75% of all the livestock in Iceland and possibly also a quarter of its population.
 
The famine took hold elsewhere, with reports of crops failing in Sweden. In addition, the toxic atmospheric gases proved fatal to large numbers of people, with Dr John Grattan of the University of Aberystwyth (quoted by The Naked Scientist) stating a figure of ‘something like 20,000 extra people’ dying in the summer of 1783. Although there are no accurate figures, the death toll worldwide must have been significant. 
Moving further afield, the Drishtikone blog states:
The atmosphere also impact the weather in other areas. India’s monsoon was severely impacted contributing to the drought of 1783-84, which led to Chalisa Famine. 
The modeling showed significant warming that occurred in the region west to east across Africa to the southern Arabian Peninsula and on to India during the summer of 1783. With little or no monsoon, there were no clouds to bring rain for the rivers or shield the surface from evaporation. Little or no rain, no irrigating floods, no crops and no food — all conspired to bring about the situation Volney described, and all were traceable back to Laki. 
It has been said time and again that the entire ecosystem is linked. In case of the impact of Laki Eruption to India leading to the Chalisa Famine, the underground occurrences – which caused volcanic eruption led to weather changes that devastated many large areas and killed many. 
 That famine caused over 11 million deaths in India alone.

Ars Technica warns that "[t]here have been four 'Laki-like' eruptions in Iceland over the past 1,150 years—some bigger, some smaller—which means this is not just an academic exercise. It’s a scenario that we could very well encounter in the near future."

No comments:

Post a Comment