Sunday, March 19, 2017

Turning Earth into a Snowball is Not a Racial Pun - Science

At one time, Earth really was a snowball as it was covered from pole to pole after one of the most dramatic weather events in the planet's history.  Anything that stupendous is going to draw scientists like kids to an ice cream truck and, sure enough, it did.

What caused the largest glaciation event in Earth's history, known as 'snowball Earth'? Geologists and climate scientists have been searching for the answer for years but the root cause of the phenomenon remains elusive.

Now, Harvard University researchers have a new hypothesis about what caused the runaway glaciation that covered Earth pole-to-pole in ice.

The research is published in Geophysical Research Letters.

Science Daily:  A perfect storm of fire and ice may have led to snowball Earth

About 700 million years ago, runaway glaciers covered the entire planet in ice. Harvard researchers modeled the conditions that may have led to this so-called 'snowball Earth.'

Credit: Image courtesy of NASA

Note the time period since 700 million years isn't that long for a planet which has been spinning for about 4.5 billion.

Researchers have pinpointed the start of what's known as the Sturtian snowball Earth event to about 717 million years ago -- give or take a few 100,000 years. At around that time, a huge volcanic event devastated an area from present-day Alaska to Greenland. Coincidence?

Harvard professors Francis Macdonald and Robin Wordsworth thought not.

- SD

Note:  I'm presenting the information in the same sequence as the originating article so allow them a little suspense, please.

Geological and chemical studies of this region, known as the Franklin large igneous province, showed that volcanic rocks erupted through sulfur-rich sediments, which would have been pushed into the atmosphere during eruption as sulfur dioxide. When sulfur dioxide gets into the upper layers of the atmosphere, it's very good at blocking solar radiation. The 1991 eruption of Mount Pinatubo in the Philippines, which shot about 10 million metric tons of sulfur into the air, reduced global temperatures about 1 degree Fahrenheit for a year.

- SD

We see all volcanoes are not the same and this one was loaded with sulfur which made for a substantive change.

Another important aspect is where the sulfur dioxide plumes reach the stratosphere. Due to continental drift, 717 million years ago, the Franklin large igneous province where these eruptions took place was situated near the equator, the entry point for most of the solar radiation that keeps Earth warm.

So, an effective light-reflecting gas entered the atmosphere at just the right location and height to cause cooling. But another element was needed to form the perfect storm scenario. After all, the Pinatubo eruption had similar qualities but its cooling effect only lasted about a year.

- SD

They're going to keep the suspense alive since I'm sure you have all got it that volcanoes cause cooling but they tease us with the other factor.

It turns out it really was a tease since the volcanoes did it all along; they just did a whole lot more of it.

The eruptions throwing sulfur into the air 717 million years ago weren't one-off explosions of single volcanoes like Pinatubo. The volcanoes in question spanned almost 2,000 miles across Canada and Greenland. Instead of singularly explosive eruptions, these volcanoes can erupt more continuously like those in Hawaii and Iceland today. The researchers demonstrated that a decade or so of continual eruptions from this type of volcanoes could have poured enough aerosols into the atmosphere to rapidly destabilize the climate.

"Cooling from aerosols doesn't have to freeze the whole planet; it just has to drive the ice to a critical latitude. Then the ice does the rest," said Macdonald.

- SD

Maybe you ask what's the point when we all die if it happens again but there is a real purpose.

Understanding how these dramatic changes occur could help researchers better understand how extinctions occurred, how proposed geoengineering approaches may impact climate and how climates change on other planets.

"This research shows that we need to get away from a simple paradigm of exoplanets, just thinking about stable equilibrium conditions and habitable zones," said Wordsworth. "We know that Earth is a dynamic and active place that has had sharp transitions. There is every reason to believe that rapid climate transitions of this type are the norm on planets, rather than the exception."

- SD

In looking to the past, they're looking to space and you see above that's no exaggeration.

There's a large packet of sci fi stories which built around colonies which were established somewhere and the weather subsequently changed.  Even "Star Trek: Wrath of Khan" is somewhat similar although the reason for the weather change wasn't the same.  In that one, Ricardo Montalban's people were reduced to rags when the planet's weather changed to make it a Sahara Desert.

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