What caused the last ice age?

kstand · 27-01-2012 9:34am #1

A question that often comes into my head and one I have never heard anyone ever answer - what cuased the last ice age?
We know that a comet/asteroid impact in the Yucatan peninsula wiped out the dinosaurs almost 70m years ago, we can tell the make up of stars many light years away, you could even argue that recently, scientists have find the Higgs boson. But I have never heard anyone explain what exactly caused the last ice age, though there have been theories.
When you consider that the ice was as far down as the south of France as recently as 16000 years or so ago (or so I've read), surely it merits a proper study? Could it have been caused by a huge volcanic eruption and is there anything there to back that up? Or what or the current concensus?

krd · 27-01-2012 4:08pm

Climate change happens all the time - even long before man arrived, the climate did its' own thing.

The cause of the last ice age was the seas getting warmer, not colder. More water evaporated from the seas, and landed as snow, which was compacted into ice, and took an incredibly long time to melt.

We're not on the verge of another ice age - no matter what you hear. There's so much water in the seas, it can take thousands of years to change temperature.

Nature doesn't always follow nice neat predictable patterns. Its' path can be wildly chaotic.

oneillMan999 · 28-01-2012 6:56pm

Bad weather.

RichieC · 30-01-2012 5:09pm

Afaik the wobble in the earth spin.

Turtwig · 30-01-2012 11:09pm

There have been quite literally tonnes of studies done into this area. Glacial ages can be caused by numerous factors, the sun, Earth's orbital plane, Earth's gryoscopic precession, Solar Cycles, Atmospheric chemistry, Life, Astronomical events, Geological events etc. Sometimes it can be a combination of different causes. Then various forms of feedbacks both negative and positive kick in. The last "ice age" was most likely caused by subtle changes in solar output which occurred because of slight changes to the earth's orbital precession. Chemistry* in the atmosphere does the rest.

The following article while long and detailed should provide with the answers to everything you need.

*That's a gross GROSS oversimplification!:D

Capt'n Midnight · 31-01-2012 1:10am

Ice ages are mainly determined by heat transfer, this is mainly by green house gases

see also

Snowball Earth

Azolla Event

Give me a half a tanker of iron and I will give you another ice age

development of circumpolar current

krd · 01-02-2012 3:07pm

Capt'n Midnight wrote: »

Ice ages are mainly determined by heat transfer, this is mainly by green house gases

Green house gases?......You mean like clouds.

Give me a half a tanker of iron and I will give you another ice age

And how would you do that?

Turtwig · 01-02-2012 3:17pm

krd wrote: »

Green house gases?......You mean like clouds.

And how would you do that?

Hope the good captain doesn't mind me responding.

Yep, GHG like water vapour which make up clouds.

By creating lots of dust.

Capt'n Midnight · 01-02-2012 3:36pm

krd wrote: »

Green house gases?......You mean like clouds.

you get more clouds when it's warmer

so while H2O is the main green house gas it's more of a symptom than a cause. Also it's got a half life of maybe 10 days so changes in it aren't permenant and because clouds reflect light it is in some way self regulating. Negative feedback and all that.

But the same can't be said of CO2, methane or nitrous oxides which have longer residence times, where a significant amount in the atmosphere is caused by man and where the feed back mechanisms are positive.

warming of siberian permafrost and ocean floor hydrates and drying of amazon forrest will all release more methane and carbon dioxide with a possible five degree step change in temperature

Capt'n Midnight · 01-02-2012 3:36pm

krd wrote: »

And how would you do that?

http://url.ie/e28p

krd · 01-02-2012 8:49pm

Capt'n Midnight wrote: »

you get more clouds when it's warmer

Ireland is not known for its' warmth. We get a lot of cloud. And many places with much warmer weather and warmer seas, get nothing like the clouds we get.

so while H2O is the main green house gas it's more of a symptom than a cause. Also it's got a half life of maybe 10 days so changes in it aren't permenant and because clouds reflect light it is in some way self regulating. Negative feedback and all that.

I think you're confusing clouds with water vapour. It's not quite the same thing. There is always water vapour in the air. In hot and humid places they have more water vapour in the air than we have here. It doesn't cycle out that easily. Clouds, which are made up of condensing water vapour reflect a lot of light.

There's an important reason why the visible spectrum is where it is. If you look at the graph below, you'll see the visible spectrum is in the place where there is the least absorption by naturally occurring gases. Which extinguish/absorb all the light available to their absorption spectrum. If you don't understand this you'll have to think about it. If you shift, the visible spectrum down a few hundred nano metres or if you shift the spectrum up a few hundred nanometres, because of the absorption spectra of oxygen, or water vapour, we'd be in permanent darkness.

It's interesting, in that an alien planet may look to our eyes densely covered in an impenetrable fog - but to aliens who live on the planet - their visible spectrum would probably be in a range where there is little atmospheric absorption. And they wouldn't even be able to see the fog.

But the same can't be said of CO2, methane or nitrous oxides which have longer residence times, where a significant amount in the atmosphere is caused by man and where the feed back mechanisms are positive.

The water vapour is always there. And always absorbing along it's bands - most of the spikes of the laughing gas and CO2 overlap with water vapour - if they weren't there, water vapour would absorb the light. The whole theory of anthropogenic global warming, is the idea that where there is no overlap gases like CO2 and NO2 can make the planet warmer. But if you look at the absorption spectra - if the atmosphere of earth was completely made of NO2 then the planet would be very cold.

warming of siberian permafrost and ocean floor hydrates and drying of amazon forrest will all release more methane and carbon dioxide with a possible five degree step change in temperature

Throughout an average day in Ireland, the temperature can fluctuate by more than five degrees. Cloud cover can vary greatly from year to year. It's quite chaotic.

One theory of the Ice Age, was that by chance there was a long period of low cloud cover - giving the seas just enough extra energy to get warmer by a few degrees. This led to more snowfall, and more cloud cover - snow can really stick if there's enough of it and enough cloud cover. I've been places where they can get long snow coverage - and even as the summer is approaching on hot days - there can still be loads of snow around and it's not melting.

krd · 01-02-2012 9:26pm

Capt'n Midnight wrote: »

http://url.ie/e28p

listen. This is one reason I completely lost patience with environmental scientists. Very often they come out with absurd claims and no one challenges them. Everyone just nods their heads and smiles smugly.

He's not even wrong.

If he had this tanker of iron. He'd need to find a way of distributing it wildly across the plankton fields that can feed on it. It would have to be micro fine - plankton are near the surface. If the Iron precipitated - if it was in clumps any large than super fine dust, there's no way they could get a chance to eat it.

Iron rich rocks are probably leaching mega tonnes of iron into the sea all the time. Most of it - if not all of it, would be Iron oxides. It doesn't dissolve well, and precipitates.

There would be other factors to control the plankton density. There's only so much sunlight available to it - and what's to stop all the other sea creatures who feed on it gorging themselves until their bellies burst. What's to stop the plankton eating itself to death. But it's not going to happen anyhow - most of the iron would have long since precipitated before the plankton got a chance to eat it.

John Martin is talking out of his ass. An Ice Age, is and can only be, caused by the evaporation of the seas, and the water ending up being stored on land.

His claim is drivel.

I've seen some terrible claims made against CO2. For a while on the wikipedia page for CO2 AGW, there was a claim that CO2 shrunk fruit bearing stamens and the rice harvest in China was about to catastrophically fail. This is complete nonsense - CO2 increases fruit bear stamens and makes them much larger. It's why farmers pump green houses full of CO2, to boost harvests - and even a small amount of CO2 can significantly increase the plant and fruit sizes, and the amount of fruit, and length of growing time need. Indoor marijuana growers use the same trick.

Going by John Martin's reasoning, anthropogenic CO2 should take care of itself. As more CO2 is available to plants like trees, and grasses, they should grow larger, and sequester more carbon, as CO2 increases.

Capt'n Midnight · 01-02-2012 11:48pm

krd wrote: »

Ireland is not known for its' warmth. We get a lot of cloud. And many places with much warmer weather and warmer seas, get nothing like the clouds we get.

*sigh*

70% of the earths surface is covered by water, and a fair chunk of the rest is wetlands / snow covered. In general evaporation goes up with warmer air.

The more water vapour you have in the air then the more clouds you get.

Clouds, which are made up of condensing water vapour reflect a lot of light.

yes, that's how the negative feedback works, it's like Daisyworld.

If you shift, the visible spectrum down a few hundred nano metres or if you shift the spectrum up a few hundred nanometres, because of the absorption spectra of oxygen, or water vapour, we'd be in permanent darkness.

Nope because we'd have evolved different pigments in our eyes, perhaps before the oxygen catastrophe other pigments were in use ?

One theory of the Ice Age, was that by chance there was a long period of low cloud cover - giving the seas just enough extra energy to get warmer by a few degrees. This led to more snowfall, and more cloud cover - snow can really stick if there's enough of it and enough cloud cover. I've been places where they can get long snow coverage - and even as the summer is approaching on hot days - there can still be loads of snow around and it's not melting.

If true then that's an example of positive feedback, but warmer seas would affect the pack ice coverage so maybe not. Anyway a big change in temperature of the sea could affect ocean current patterns (something about great globs of salty water from the med getting in on the act) and could release methane hydrates

Capt'n Midnight · 02-02-2012 12:06am

krd wrote: »

He's not even wrong.

The original claim was tongue in cheek in that the amount of Iron you need in theory, from a back of the envelope calculation, would fit in one ship.

And you would probably just use Iron Sulphate, it's water soluble, of course the problem is dispersing it over a wide enough area.

krd · 02-02-2012 6:23am

Capt'n Midnight wrote: »

If true then that's an example of positive feedback, but warmer seas would affect the pack ice coverage so maybe not. Anyway a big change in temperature of the sea could affect ocean current patterns (something about great globs of salty water from the med getting in on the act) and could release methane hydrates

The pattern of the currents is caused by the rotation of the earth. They're not going to change unless the rotation of the earth changes.

Every winter, snow falls on the North pole, and every spring ice melts in the north and flows into the sea. To have a ice age, all you need is for more snow to fall than can be melted in the spring. Then the ice will just keep growing. If there's enough ice in the right place, it can block the gulf stream and on goes the ice age.

krd · 02-02-2012 6:40am

Capt'n Midnight wrote: »

The original claim was tongue in cheek in that the amount of Iron you need in theory, from a back of the envelope calculation, would fit in one ship.

Well, you don't know it's "tongue in cheek", until you look into it. You end up with people assuming that literally all it would take would be a ship load of iron to cause another ice age. That the seas are incredibly fragile, and a tanker ship wreck might cause the end of the world.

This is how some of the loopy stories get started. There are environmental campaigners who are so dumb, they think CO2 is a poison gas, and causes lung cancer. And an idea like that comes from someone says that the carbon from coal has more radioactive isotopes than the carbon cycled by plants.

The claim is like a nuclear physicist claiming that with a lump of coal, they could blow London to pieces. They could, if they could find a way of releasing all the nuclear energy from it. The truth is they can't

And you would probably just use Iron Sulphate, it's water soluble, of course the problem is dispersing it over a wide enough area.

You probably wouldn't. Will the plankton be able to tolerate a higher acidity from eating the sulphate.

The whole claim is bunk. You'd be expecting to see massive rich plankton blooms around shipwrecks - which you don't.

Capt'n Midnight · 02-02-2012 12:36pm

krd wrote: »

The pattern of the currents is caused by the rotation of the earth. They're not going to change unless the rotation of the earth changes.

I think you are confusing the coriolis effect with the thermohaline circulation etc.

Also a few million years ago North and South America weren't joined which changed ocean currents a tad,

Capt'n Midnight · 02-02-2012 1:11pm

krd wrote: »

You probably wouldn't. Will the plankton be able to tolerate a higher acidity from eating the sulphate.

The whole claim is bunk. You'd be expecting to see massive rich plankton blooms around shipwrecks - which you don't.

LOL

the Iron has to be in a biologically accessible form.

krd · 02-02-2012 6:05pm

Capt'n Midnight wrote: »

LOL

the Iron has to be in a biologically accessible form.

Iron oxides are a biological accessible form. And that's probably the form plankton feeds on. It's the most likely form that's going to be in the sea. And probably fine enough to be stirred up to the surface, where the plankton will be. If the plankton don't like that form, sea vegetation can probably convert the iron into a form it likes.

John Martin would need to individually spoon feed each one of his planktons - and make sure they all ate his Iron up.

himnextdoor · 04-02-2012 4:30pm

I have a theory and it is to do with the solar system's passage across the galactic plane.

Imagine a sphere spinning whilst submerged in water. The surface of the sphere causes water to be 'flung' away from it but the force is greatest along the equatorial plane.

I think it might be similar with the galaxy; the spin of the galaxy gives rise to a force that tends to push material away from the centre and the 'current' is strongest along the galactic plane.

As the solar system moves into the galactic plane it 'feels' an increase in that current but due to the difference in inertial mass, the earth is affected sooner and to a larger degree than the sun.

If the earth is between the sun and the galactic centre then it might be 'pushed' closer to the sun, its orbital velocity is slightly increased and the temperature rises.

If the sun is between the earth and the galactic centre then the earth might be 'pushed' further away from the sun, its orbital velocity decreases and the earth cools.

If we are looking for a fifty-two thousand years cycle then this might fit the bill.

Capt'n Midnight · 04-02-2012 5:20pm

himnextdoor wrote: »

If the earth is between the sun and the galactic centre then it might be 'pushed' closer to the sun, its orbital velocity is slightly increased and the temperature rises.

We haven't detected any unknown force large enough in the movements of the Voyager space probes when they left the region where the Sun's effects dominate over the interstellar ones.

http://en.wikipedia.org/wiki/Heliosphere

If we are looking for a fifty-two thousand years cycle then this might fit the bill.

just one little observation that might upset theory

The up/down cycle takes over sixty million years.

himnextdoor · 04-02-2012 6:53pm

Capt'n Midnight wrote: »

We haven't detected any unknown force large enough in the movements of the Voyager space probes when they left the region where the Sun's effects dominate over the interstellar ones.

http://en.wikipedia.org/wiki/Heliosphere

just one little observation that might upset theory

The up/down cycle takes over sixty million years.

Yup. I'm an idiot.

Capt'n Midnight · 04-02-2012 7:14pm

That cycle has been proposed for mass extinctions in the past.

I think they've ruled out the Nemesis? theory about a brown dwarf star orbiting every few dozen million years too.

Nothingbetter2d · 06-02-2012 4:25pm

does polar flips also cause ice ages / droughts? the magnetic field flips from north to south every few hundred thousand years resulting in changes in the flow of magma. we are aparently due another flip in the next few thousand years. Observations from space have already shown signs of where the magnetic field is begining to weaken... bermuda is one such area showning a weakness area.... this maybe also affecting the el nino weather effect

himnextdoor · 23-02-2012 3:59am

Capt'n Midnight wrote: »

That cycle has been proposed for mass extinctions in the past.

I think they've ruled out the Nemesis? theory about a brown dwarf star orbiting every few dozen million years too.

That makes much more sense - crossing the galactic plane causing mass extinctions for one reason or another, that is.

chrismartin4u · 16-05-2012 3:07pm

I would like to say in one word, it was " Natural Disaster".

wolf_ · 14-07-2012 9:31pm

I do believe a lot of it can be explained by the Milankovitch cycles.

What caused the last ice age?

Comments