The Eyjafjallajökull volcano in Iceland is becoming more active again with the ash cloud shutting down 19 Spanish airports. But the real worry is that Katla a much larger sister volcano will erupt. Every time that Eyjafjallajökull volcano has erupted in recorded history, the much larger Katla volcano has also erupted. Katla typically awakens every 80 years or so, having last exploded in 1918. Now slightly overdue, scientists are watching Katla carefully.
There was a magnitude 3 earthquake under the glacier at Katla this week, along with many smaller quakes, raising concerns that history is about to be repeated.
A Katla eruption would be 10 times stronger and shoot higher and larger plumes of ash into the air than its smaller neighbor. The two volcanoes are side by side in southern Iceland, about 12 miles apart and are thought to be connected by a network of magma channels.
Katla is buried under a thick icecap, the massive Myrdalsjokull glacier which is one of Iceland's largest. It has more than twice the amount of ice that the current eruption has burned through – threatening a new and possibly longer aviation standstill across Europe.
The question is if this larger volcano erupts, as it has in the past, could it influence global weather patterns like other large volcano eruptions in South America and the Philippine Islands? The last time Katla erupted was 1918. It turns out that 1918-1919 were interesting weather year with a strong El Nino influence, and a winter of intense global climate variability.
The year 1918 began with record-setting cold temperatures in much of the United States. January 1918 still stands as the coldest January registered in Central Park in New York. The surface air temperature changes from 1917/18 to 1918/19 was among the largest year-to-year changes on record.
It is true that tropical volcanism has more global impact as the ash and aerosols travel north and south and affect most of the globe while high latitude volcanoes find ash and gases limited more to the higher latitudes and tend to have effects that don’t last as long. But research by Oman (2006) showed northern hemispheric high latitude volcanoes influence the Arctic and North Atlantic Oscillations which can have a profound effect on the climate as e saw last summer and then this winter with Redoubt and Sarychev and may this summer and next winter with Eyjafjallajokull, especially if the eruptions continue and become stronger and if it excites nearby larger Katla into action as past eruptions have. The stratosphere is lower in the polar regions than in the tropics where eruptions need to get well above 55,000 feet to have long term impact. In the polar regions a 30,000-40,000 foot ash and aerosol cloud can have impact.
A study of the 1918/1919 El Nino found the west coast of the US was much cooler than normal for several years. I looked at the Sacramento temperatures from 1877 to 2009. The annual means from 1877 to 2009 is 61.4. The average mean temperature for 1918 was 59.92, 1.48 below the annual mean. For 1919 the average mean was 59.3 or 2.1 below the mean. Even cooler was 1920 with 59.21, a year 2.19 below the mean. However, there was no indication if the cooling was due to vulcanism or the El Nino weather pattern. Or both.While this winter was influenced by an El Nino weather pattern, there is no assurance that next winter will follow the same pattern. We will just have to wait until Mother Nature makes up her mind. More vulcanism? More El Nino, or perhaps even a wet La Nina pattern? Only Mother nature knows for sure. Stay Tuned.