From Royal Holloway, University of London
New research published today (Friday 27th June 2014) in the journal Nature Scientific Reports has provided a major new theory on the cause of the ice age that covered large parts of the Northern Hemisphere 2.6 million years ago.
The study, co-authored by Dr Thomas Stevens, from the Department of Geography at Royal Holloway, University of London, found a previously unknown mechanism by which the joining of North and South America changed the salinity of the Pacific Ocean and caused major ice sheet growth across the Northern Hemisphere.
The change in salinity encouraged sea ice to form which in turn created a change in wind patterns, leading to intensified monsoons. These provided moisture that caused an increase in snowfall and the growth of major ice sheets, some of which reached 3km thick.
The team of researchers analysed deposits of wind-blown dust called red clay that accumulated between six million and two and a half million years ago in north central China, adjacent to the Tibetan plateau, and used them to reconstruct changing monsoon precipitation and temperature.
“Until now, the cause of the Quaternary ice age had been a hotly debated topic”, said Dr Stevens. “Our findings suggest a significant link between ice sheet growth, the monsoon and the closing of the Panama Seaway, as North and South America drifted closer together. This provides us with a major new theory on the origins of the ice age, and ultimately our current climate system.”
Surprisingly, the researchers found there was a strengthening of the monsoon during global cooling, instead of the intense rainfall normally associated with warmer climates.
Dr Stevens added: “This led us to discover a previously unknown interaction between plate tectonic movements in the Americas and dramatic changes in global temperature. The intensified monsoons created a positive feedback cycle, promoting more global cooling, more sea ice and even stronger precipitation, culminating in the spread of huge glaciers across the Northern Hemisphere.”
@mkelly says:June 27, 2014 at 9:55 am
@G. Karst says:June 27, 2014 at 10:52 am
Why are there inter-Glacial s and why are we in one now ?
@Sun Spot
The glacial and inter-glacial periods of this present Ice Age, which have been going on for about 3 million years seem to be controlled by the Milankovitch cycles. We are in an inter-glacial episode now because 3 of these cycles, about 12,000 years ago gave close to maximum insolation to the earth, AT THE Northern Hemisphere LATITUDES. The key is what happens in the northern hemisphere, because that is where two huge ice sheets grow during a glacial episode. Such episodes last for 90,000 years or more. Look up the “Laurentide Ice Sheet” to see how extensive the ice sheet on North America can be – 5 million square miles at its peak.
@ur momisugly D J Hawkins
‘Google “Operation Plowshare” and “Pan Atomic Canal”. There is no doubt in my mind that a sea-level canal is technically feasible. Politically feasible is an entirely different kettle of fish.’
Thanks. I will look these up. The reason for my interest is because I had to research this area for a short story I was writing a couple of months ago. Whatever more I can learn, I am very grateful. Thanks again.
Duh!!!!!!! Who are they kidding? Everyone has known about that and its impacts on global circulation and sea chemistry changes for DECADES.
But of course I know who they are kidding – everyone who is NOT a geologist.
mpainter says:
June 27, 2014 at 10:44 am
We are still a glacial epoch. The Holocene, ie the past ~11,000 years, is just the latest of many interglacial intervals. The glacial phases last much longer than interglacials, averaging about 100,000 years. The cycles (named after Milankovitch) of longer glacials & shorter interglacials are largely controlled by orbital & rotational parameters, such as the eccentricity of earth’s orbit.
Earth has been in an “Icehouse” for about 38 million years. Before then, the planet was largely ice free. During the Oligocene, ice sheets formed over Antarctica. They contracted a bit during the following Miocene, but with the closure of Panama, they not only grew bigger there, but occurred in the Northern Hemisphere. Greenland of course still has its ice sheet, but during interglacials the North American, European & Asian ice sheets melt. During the longest, warmest integlacials, like MIS 11, even the southern dome of the Greenland ice sheet thaws.
The northern continental ice sheets will return in a few thousand to at most some tens of thousands of years.
Icehouse & “Hothouse” intervals alternate in earth history. Most of the Mesozoic & the early Cenozoic (Paleocene & Eocene Epochs) were a Hothouse world, without ice at the poles. The Late Carboniferous & Early Permian Periods were an Icehouse, & in the middle of the Mesozoic there was a mild Icehouse (around the Jurassic/Cretaceous boundary). That cold snap was followed by amazingly warm times in the mid-Cretaceous.
Climate is cyclic & self-regulating.
What is a geographer doing tackling the cause of the ice age. People with a knowledge of science have been trying to figure this all out for 150 years since Louis Agassiz first recognized that there had been ice ages at all. Changed salinity? Which way did it go? Now let me do some research:
http://en.wikipedia.org/wiki/Pliocene
“The formation of the Isthmus had major consequences on global temperatures, since warm equatorial ocean currents were cut off and an Atlantic cooling cycle began, with cold Arctic and Antarctic waters dropping temperatures in the now-isolated Atlantic Ocean.”
Hmmm….probably the same source that our grapher of the geo got his inspiration. But note, this cooled the Atlantic waters because of the “..cold Arctic and Antarctic waters”. So it was already cold in the Arctic and Anarctic. And, with the Isthmus still joining us, what made the ice go away again. With the big names’ ‘hiatus’ in climate research, we are getting a lot of bottom feeders getting into the act.
“The team of researchers analysed deposits of wind-blown dust called red clay” HAHA, that IS what a geographer would call it.
@jim, why do you presuppose that if a manmade seaway were dug in Panama that the world would immediately enter a glacial period?
The area where the canal is built appears to be a major syncline, hence the large lake, and elevations are around 200 m at most in the area. Looking at a detailed motion of the plates it appears that area may be wrenching apart, giving Panama its shape and topography.
http://peterbird.name/publications/2003_PB2002/2003_PB2002.htm
Considering how difficult it was to build a canal through panama, building a seaway that allowed sufficient circumequatorial currents to exist seems impossible.
@Robert W Turner
“@jim, why do you presuppose that if a manmade seaway were dug in Panama that the world would immediately enter a glacial period?”
It is more than likely that if the Pacific and Atlantic oceans were once again united as one ocean in the tropical zone, that this would greatly upset the current thermohaline circulation. The result could mean a destabilization of the entire world climate for a few thousand years or more. It is my guess that when the world’s climate becomes upset, it reverts to its default, and currently its default position is a glaciation period since we are currently living within an Ice Age – nothing scientific here – just a hunch.
milodonharlani says:
Earth has been in an “Icehouse” for about 38 million years. Before then, the planet was largely ice free.
I thought the pleistocene ice age began about 3 million years ago? Please forgive me if I am missing something.
Also, weren’t there earlier “Icehouses” such as the Huronian and Cryogenian ice ages during the proterozoic?
Gary Pearse says:
June 27, 2014 at 1:06 pm
Not all the ice has gone away. Because we’re in a warmer interglacial, the Laurentide, Scandinavian & Siberian ice sheets have retreated or melted, but the ice sheets will return, as they periodically have done for about 2.6 million years.
The Pleistocene & Holocene are just a colder episode in the already cooler than the Phanerozoic average Icehouse that began at the Eocene/Oligocene boundary, when Antarctica was fully cut off by deep ocean channels from South America & Australia.
James McCown says:
June 27, 2014 at 1:32 pm
As I just wrote above, the Pleistocene began about 2.6 million years ago, but earth was already in an Icehouse, which basically means a time in geologic history during which ice sheets exist, plus any montane glaciers grow bigger. The Pleistocene & Holocene Epochs have been colder than the Oligocene, Miocene & Pliocene, but all count as an Icehouse, since before the Quaternary (Pleistocene & Holocene) glaciations of the northern hemisphere, Antarctica was already covered by extensive ice sheets.
The present Icehouse (from c. 38 Ma to now) followed a very warm Hothouse during the Cretaceous Period & Paleocene & Eocene Epochs of the Paleogene Period (replacing the Tertiary) the Cenozoic Era. Peak warmth during that Hothouse occurred during the mid-Cretaceous & at the Paleocene-Eocene Thermal Maximum (PETM), when alligators thrived in Alaska.
PS: Yes, there have been Icehouses more serious than our current one, including the Huronian (2.4 to 2.1 Ba) & at least three other “Snowball Earth” episodes during Cryogenian (850 to 635 Ma). The current Phanerozoic Eon has seen at least three major & one minor intervals of glaciation, ie at the Ordovician/Silurian boundary (when CO2 was in the thousands of parts per million), the Late Carboniferous & Early Permian, the lesser episode at the Jurassic/Cretaceous border, & the present Cenozoic one.
Anything to hide the truth!
The yo-yo from very cold to somewhat warm has been happening repeatedly. ALL Ice Ages begin suddenly and all go into Interglacial melting SUDDENLY, too.
The only mechanism that can do this trick is the sun. When the sun is shedding lots of heat, we heat up here on earth. When it ceases and there are virtually no sun spots, it gets really really cold.
End of story. The configuration of the landmasses may amplify the surges and withdrawal of energy from the sun but they don’t cause the instability itself.
The idea that the movements of continents can make a difference to the global average temperature makes a mockery of the whole energy budget cartoons.
D. Cohen says: June 27, 2014 at 10:50 am
Nature has already done this experiment for us.
The Chicxulub Impact
The results were not nice.
Weren’t there several ice ages?
How many times did North and South America marry and get divorced?
What about the Medieval Warm Period? Did that occur when N. and S. America decided to take some time apart to find themselves?
@JohnTyler
There were several ice ages. The one we are in now has lasted from 2.5 to 3 million years.
At one time South America was joined with Antarctica, but the South American plate drifted north and broke from Antarctica and pushed into North America. To my knowledge, the South American plate is still pushing north, so Brazil may butt into the Gulf of Mexico in 50 million years or so. Who really knows.
The Medieval Warm Period occurred just 1,000 years ago. There are warm and cool periods within any interglacial period like the one we are in today. Right now, we are experiencing another warming period as we did 1,000 years ago. These are “minor” warming periods on the larger geological scale without the need for major geological changes to initiate them. We really do not know what controls the climate, but we can only guess. It is a good bet though, that the formation of the Isthmus of Panama started this present Ice Age.
Continental configuration, who’d a thought?
By the way, ever noticed that Africa, South America, North America, Australia are all upright N-S? Chances of this at random is very low. Only few places which aren’t upright are volcanic New Zealand, Japan, Central America, Indonesia etc.
Centrifugal force?
D.J. Hawkins says:
June 27, 2014 at 11:16 am
@Jim Stevens says:
June 27, 2014 at 10:08 am
@D. Cohen says:
June 27, 2014 at 10:50 am
Google “Operation Plowshare” and “Pan Atomic Canal”. There is no doubt in my mind that a sea-level canal is technically feasible. Politically feasible is an entirely different kettle of fish.
===========================================================================
We may know soon enough.
http://www.washingtontimes.com/news/2013/jul/15/chinese-tycoon-plans-to-rival-panama-canal-with-40/?page=all
I have no idea how old the theory about how the joining of the North and South America continents changed the climate enough to start up the current ice age we’re in, but one of my geology professors in the late 70s was tossing around the same concept to us undergrads.
They figured all that out by digging up some clay in Northern China? Impressive. Seldom have such large conclusions been drawn from so little data since the days when little old ladies calculated how many kids you were going to have by looking at tea leaves.
Walt Stone
“I have no idea how old the theory about how the joining of the North and South America continents changed the climate enough to start up the current ice age we’re in,”
I think you will find that it’s part of a general pattern: the temperature differential between the poles and equator has a lot to do with ice ages.
If the continents are joined, there is less heat exchange between the pole and equator, meaning greater temperature differential and more ice at the poles. If North and South America join, this is part of that process I suspect.
Restrictive ocean circulation is one of the factors reducing heat exchange. It also helps if you have a lot of continent about the poles to build up ice to begin with and restrict circulation, meaning once again, you get more ice. Antarctica, Greenland and North America as well as Russia is a lot of land about the poles. Africa is slowly joining Europe (as well as Arabia, both joining Eurasia) meaning oceanic circulation is decreasing there also, the Mediterranean will close entirely in a few million years. Australia moving north is closing the circulation with Indonesia and SE Asia as well, as well as setting up the circumpolar current in the southern ocean. India has joined Asia closing the Tethys Ocean. All these factors have likely cooled the earth over the last 50 million years or so, because they all reduce heat exchange between the tropics and the poles, as well as allowing ice to build up over continents near the poles.
If the poles are cooler and the tropics warmer, the earth is the same average heat as if the temperature was all the same the world over, except that with extra ice at the poles this reflects sunlight so it will actually be slightly cooler on average when the temperature differential is high.
This process is self reinforcing, as they also think one of the triggers into an ice age is when ice doesn’t melt in summer, so its cooler summers that trigger an ice age and not so much cooler winters, because of the ice albedo effect. Ice that doesn’t melt in summer keeps building up and up causing runaway cooling, whereas if it even just melts this doesn’t occur, so it is indeed one of nature’s tipping points.
Other possible factors include: the tropics are buffered against heating due to excess water vapour, meaning that isn’t so much how warm the tropics are, but how cool the poles are that triggers an ice age, the tropics will only be so warm and not much more, the poles can keep cooling indefinitely. Some have also suggested the Himalayas might have cooled the earth with the extra weathering going on (removing C02), as well as blocking heat from the Indian Ocean to central Asia.
So we have:
-continents which are joined tend to reduce ocean circulation and heat exchange, meaning more ice at the poles increasing ice albedo and reducing overall earth temperature,
– more continents near the poles are able to build up ice (particularly where ice over land doesn’t melt in summer) as well as restrict heat exchange with the tropics,
-oceans and seas which close generally reduce heat transfer (Tethys, Mediterranean, SE Asia, N and S America),
-a circum polar current also reduces heat exchange (meaning we have both a lot of land at the poles as well as a circum polar current in different hemispheres, which might be ideal for an ice age to develop)
-possible excessive high mountain ranges also reduce heat transfer as well as increase ice albedo.
It seems the earth has been gradually getting cooler due to many convergent factors over the last 50 million years or so, but if you ask an alarmist they get it round the wrong way-they will answer that c02 has reduced in the atmosphere over the last 50 million years, which is an effect, not a cause.
The relation with atmospheric circulation as described on their figure 1 does not inspire any confidence in their conclusion.
So how often does an IPCC model produce an ice age?
Perhaps the study by Stevens et. al. (together with similar earlier work) is news that we can use. How so?
Suppose that 500 years from now, we find ourselves descending into the next major glacial advance, aka ‘ice age’. One rational response would be a massive geo-engineering project to resurrect the Panama Seaway, in order to affect oceanic circulation. This should warm the planet enough that Canadians, Chicagoans, and Northern Europeans would not become climate refugees.
Of course, geo-engineering on this scale would not be cheap. There would be obvious secondary costs. We’d need to construct nice condos in Florida, to expedite U.S. citizenship, and to provide ESL classes and job training for approximately half of all Panamanian families.
Nicaragua is considering the construction of a secondary canal. We should encourage and partially fund such a project, albeit on a much larger scale than was originally proposed.
Funding for environmental mitigation may also be needed in both countries.