Continental drift: effect on climate cycles

[Naty1]

I'd be interested in any ideas or theories or references on how the location of the continents is thought to affect global warming and cooling cycles. I previously read somewhere that the current position of the continents would cause different net solar heat absorption/reflection than prior locations hundreds of thousands or millions of years ago.

Don't quote me on this but it may be that currently there are signficiantly greater land masses further from the equator than in past epochs...but I can't remember what the hypothesis was about net absorption/reflection of solar energy relative to earlier periods.

 

[mgb_phys]

I'm not sure that continent movements are really that cyclic.
Land masses joining and separating have a huge effect on ocean currents and so on local climate.
N and S America joining directed the gulf stream toward Europe and the separating of Antarctica created the Antarctic circumpolar current that keeps the south pole nice and cold.

 

[jim mcnamara]

It does affect climate in a huge way, and if you view "cycles" as hundreds of millions of years then I guess the answer is 'yes'. The formation of supercontinents (see my definition below) is an example:

Rodinia was the first supercontinent, then later on at the end of the Triassic, Pangea was the last. That we know about anyway. Ur, Neno and the others mentioned in the literature are excluded by me since they predate multicellular life. Plus, I'm using supercontinent to mean one giant continent made of most all of the continents- not Laurasia or Gondwana which were two continents merged.

Rodinia has been "blamed" for a long cold period from about ~700 mya to 550 mya.
This has been referred to as snowball Earth or the 'white Earth hypothesis'
http://www-eps.harvard.edu/people/faculty/hoffman/snowball_paper.html

There is newer evidence to refute a complete 'iceball' Earth
http://www.sciencedaily.com/releases/2007/03/070323104746.htm

The late Triassic was very warm, possibly the warmest period since multicellular life took hold on Earth- and this hot period this was when Pangea was all together in a large landmass straddling the equator.
http://www.scotese.com/ltriascl.htm

 

[Xnn]

http://earthobservatory.nasa.gov/IOTD/view.php?id=4073

Even though it is only a tiny sliver of land, relative to the sizes of continents, the Isthmus of Panama had an enormous impact on Earth's climate and its environment. By shutting down the flow of water between the two oceans, the land bridge re-routed currents in both the Atlantic and Pacific Oceans. Atlantic currents were forced northward, and eventually settled into a new current pattern that we call the Gulf Stream today. With warm Caribbean waters flowing toward the northeast Atlantic, the climate of northwestern Europe grew warmer. (Winters there would be as much as 10 degrees C colder in winter without the transport of heat from the Gulf Stream.) The Atlantic, no longer mingling with the Pacific, also grew saltier.

It may seem fairly odd, but warming winters actually tends to lead to ice ages as it allows more snow to accumulate than would otherwise. The Laurentide and Euroasian sheets were huge and they only got that way by lots of precipitation.

 

[Mammo]

http://earthobservatory.nasa.gov/IOTD/view.php?id=4073




It may seem fairly odd, but warming winters actually tends to lead to ice ages as it allows more snow to accumulate than would otherwise. The Laurentide and Euroasian sheets were huge and they only got that way by lots of precipitation.

I agree with this. It seems logical to suggest that continental drift is also responsible for the mid-Pleistocene transition. This is where the ice ages suddenly became amplified and adherred to the 100-kyr cycle around a million years ago. The restriction of the Indonesian seaway, due to Australia encroaching on Asia, seems a likely possibility to me. It would force westward equatorial currents to join the northward thermohaline circulation. This would then (I'm guessing) increase the strength of the Gulf Stream. A professional report on the situation is http://www.moraymo.us/2007_Lisiecki+Raymo.pdf

 

[Xnn]

Noticed that there were comments in Raymo's paper regarding Huybers:

Huybers (2007) supports the hypothesis of a gradual change in obliquity response with the identification of a linear, 2-Myr trend in the first moment of the power spectrum, M1, which is a weighted average of response frequency. He suggests that this trend toward lower frequency power results from long-term changes in the climate system such as cooling or ice sheet growth. However, we find two problems with this explanation of obliquity response change. First, a gradual shift in frequency response cannot explain why glacial cycles respond to obliquity modulation before 1.4 Myr but not after. (The Huybers model of obliquity pacing is insensitive to the modulation of obliquity forcing for all of the last 2Myr.) Second, in the LR04 stack the trend in M1 reverses at _2 Myr due to the presence of low frequency power from 3.5 to 2.5 Myr. Therefore, the shift to lower frequencies in d18O from 2 to 0 Myr may not be a simple response to long-term cooling or ice sheet growth. We suggest that climate records spanning at least the last 3Myr be used when interpretting the relationship between observed climate responses and the MPT.

And then concludes:

However, our observations cannot determine whether late Pleistocene 100-kyr power results from groupings of 2–3 obliquity cycles.

 

[Mammo]

Noticed that there were comments in Raymo's paper regarding Huybers:
And then concludes:

I noticed this as well. I'm inclined to think that the Huybers hypothesis regarding the 2 or 3 grouping of obliquity is simply wrong. I'm biased of course, since I think the Earth's orbital 'inclination' is a good fit to explain the 100-kyr cycle. The saw-tooth glacial cycle in a 41-kyr world still needs a full explanation though.

 

[The Dagda]

There are several super continent formations stretching back to the beginning of the non lava stage of the surface.

The last one was called Gaia IIRC (my mistake it was Pangea) it usually means there is widespread warming and some pretty cataclysmic weather. See albedo effect.

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

Albedos of typical materials in visible light range from up to 90% for fresh snow, to about 4% for charcoal, one of the darkest substances. Deeply shadowed cavities can achieve an effective albedo approaching the zero of a blackbody. When seen from a distance, the ocean surface has a low albedo, as do most forests, while desert areas have some of the highest albedos among landforms. Most land areas are in an albedo range of 0.1 to 0.4.[6] The average albedo of the Earth is about 30%.[7] This is far higher than for the ocean primarily because of the contribution of clouds.

Human activities have changed the albedo (via forest clearance and farming, for example) of various areas around the globe. However, quantification of this effect on the global scale is difficult.

The classic example of albedo effect is the snow-temperature feedback. If a snow-covered area warms and the snow melts, the albedo decreases, more sunlight is absorbed, and the temperature tends to increase. The converse is true: if snow forms, a cooling cycle happens. The intensity of the albedo effect depends on the size of the change in albedo and the amount of insolation; for this reason it can be potentially very large in the tropics.

The Earth's surface albedo is regularly estimated via Earth observation satellite sensors such as NASA's MODIS instruments onboard the Terra and Aqua satellites. As the total amount of reflected radiation cannot be directly measured by satellite, a mathematical model of the BRDF is used to translate a sample set of satellite reflectance measurements into estimates of directional-hemispherical reflectance and bi-hemispherical reflectance.

 

[Xnn]

On the first page is the following paragraph:

A long-term cooling trend is often considered responsible for the change in glacial dynamics at the MPT. Mechanisms proposed for this transition include changes in sea ice formation (Tziperman and Gildor, 2003; Ashkenazy and Tziperman, 2004), a switch from terrestrial to marine ice margins in Antarctica (Raymo et al., 2006), a gradual increase in the insolation threshold for ice-sheet ablation (Raymo, 1997; Paillard, 1998; Berger et al., 1999; Huybers, 2006), and changes in ice-sheet stability due to the gradual erosion of North American regolith (Clark and Pollard, 1998).

Notice how Raymo is listed more than once!

So, take your pick; but nobody for the Ithmus of Panama.

 

[The Dagda]

See Milankovich cycles too as the growth of ice sheets effects axial tilt and in turn effects the eccentricity of Earth's orbit which in turn leads to colder conditions or warmer accordingly. It is safe to say that ice sheets cause feedback loops that make everything cooler in front of them thus increasing ice formation, this effects axial tilt which in turn can make it colder still leading to a hypothetical snowball Earth. The effects are exponential at some point.

 

[Mammo]

On the first page is the following paragraph:



Notice how Raymo is listed more than once!

So, take your pick; but nobody for the Ithmus of Panama.

The Isthmus of Panama is mentioned a bit earlier on the page of the Raymo & Lisiecki report.

 

[Xnn]

Mammo; thanks for pointing that out.

For example, the tectonic closure of the Isthmus of Panama (Keigwin, 1982; Maier-Reimer et al., 1990), Tibetan uplift (Raymo et al., 1988; Rea et al., 1998), restriction of the Indonesian seaway (Cane and Molnar, 2001), shoaling of the thermocline (Philander and Fedorov, 2003), obliquity modulation (Haug and Tiedemann, 1998; Maslin et al., 1998), and changes in North Pacific stratification (Haug et al., 1999; Sigman et al., 2004) have all been proposed as mechanisms for the initiation of northern hemisphere glaciation.

So, a distinction is made between the initation of NH glaciation and the mid-Pleistocene
transition (MPT) from a 41K to 100K year cycles. Proposals for the MPT are more subtle.

Can't say that I really understand shoaling of the thermocline or changes in the North Pacific stratification. However, what impresses me is that all of these proposals may have played a part.

 

[Mammo]

Mammo; thanks for pointing that out.

So, a distinction is made between the initation of NH glaciation and the mid-Pleistocene
transition (MPT) from a 41K to 100K year cycles. Proposals for the MPT are more subtle.

Can't say that I really understand shoaling of the thermocline or changes in the North Pacific stratification. However, what impresses me is that all of these proposals may have played a part.

I agree Xnn. The report is quite difficult to follow in general, I find. Is this where the current scientific investigation has got us? i.e. a bit of a muddle. The simple question as to the asymmetry of the glacial cycles is interesting. Like they say, the orbital insolation is always symmetrical. Where does the asymmetry, saw-tooth graph and rapid deglaciation come from? (I have an idea that I'm working on)

 

[Xnn]

From Raymo:

The development of this asymmetry is most likely due to a change in the internal dynamics of the climate system because asymmetry is not found in any orbital or insolation curves.

and

In this model ice volume from each hemisphere responds to local insolation, creating out-of-phase precession responses during the Pliocene and early Pleistocene. Before the appearance of large northern hemisphere ice sheets, the out-of-phase precession responses in the north and south nearly balanced out, leaving the d18O record dominated by in-phase obliquity responses. As northern ice volume increased, it began to outweigh the compensating southern response, and precession power in the global climate signal also increased. In contrast, the obliquity responses recorded by d18O are in-phase across hemispheres. Therefore, the sum of northern and southern obliquity responses could follow one continuous exponential trend despite possible changes in the ratio of response across hemispheres.

So, NH ice volumes are postulated to be gradually increasing and as they do, introducing out of phase responses. The SH ice volume is constrained by the geography of Antarctica, where as that is not so in the NH... Possibly, gradually lowering CO2 levels (from more C4 plant life or higher Himilayians?) were allowing NH ice volumes to expand.

 

[Mammo]

From Raymo:

The development of this asymmetry is most likely due to a change in the internal dynamics of the climate system because asymmetry is not found in any orbital or insolation curves

I've thought about this, and the answer seems quite obvious. During deglaciation due to increased insolation, surface meltwater can reach the bottom through glacial fissures. The increased lubrication accelerates the advance of the ice sheet on the American continent due to it's topography. The debris accumulated is more likely to stay near the bottom by the time it is due for iceberg calving. More regular calving would produce smaller bergs with the band of debris located near the base. The bergs would therefore release their IRD relatively quickly, adding to the main deposit just outside the exit of Hudson Bay. Heinrich events are iceberg armadas that occur during glaciation. These are much larger with debris bands often being more centrally located within the berg. Hence the reason why they can traverse the Atlantic before dropping their load of IRD.

Rapid deglaciation compared to glaciation now makes sense. The topography of the NE American continent allows lubricated glaciers to advance much more quickly to the low-lying Hudson Bay area. Sea-level rise adds to the ability of increased ice melt from continental shelves. This is more a feature of the Antarctic topography, which is currently in a phase of accelerated deglaciation.

Source of diagram is NOAA

 

[hokie1]

The current theory is called plate tectonics and is quite distinct from continental drift, an earlier and dispelled theory. Continents don't drift -they are carried along by plates.

An important sea is the Artic sea. It is segregated from the other oceans by shallow and narrow connections. During the last Ice Age it was possible to cross the Bering Sea since it was dry.

 

[DrClapeyron]

The mid ocean ridge secretes new continental crust at different rates. Slower growth can lower the global sea level while faster rates can raise the global sea level. This changes the albedo and total absorption of CO2 while the volcanic activity emits of CO2.

 

[hokie1]

You mean oceanic crust? The change in albedo is due to what: the water itself (some property of it), the total surface covered by water, or something else?

 

[DrClapeyron]

Global eustatic sea level change effects the total surface area covered by water. During sea level rise the total surface area covered by water increases and the opposite occurs during sea level fall.

Position of the continents relative latitude will have an effect on climate. For example, if all the continents were huddled around the polar regions and the tropics were free of continent global temperature would fall. Again, the opposite would ocure when continents are huddled in the tropics witht the polar regions free.

 

[Skyhunter]

Here is a short film about the Arctic byhttp://www.nasa.gov/mov/52579main_Esu%20Pkg%20REVISED.mov" from 2003.
"[URL
Main article here[/URL].

Not only the position of the continents, but the geographic features of the continents, especially mountains. The depth of the oceans effect their circulation and heat transport as well as their ability to regulate the carbon cycle and it's feedback response to albedo flip as the ice sheets erode.

These changes are gradual, beginning slowly then amplifying as albedo flips, accelerating until the inertia is expended. We are observing a similar phenomenon right now in the Arctic. The more the perennial ice thins the more susceptible it becomes to melting or being blown into the Atlantic or Pacific. That loss of stable perennial ice appears to have reached a tipping point that will likely lead to an open Arctic. Warm Arctic summers are in the near future.

 

[Evo]

For the OP, more information on positioning of continents.

http://www.geocraft.com/WVFossils/Carboniferous_climate.html

Great paleo mapping project showing what the Earth is thought to have looked like during various periods.

http://www.scotese.com/earth.htm

 

[DDesHarn]

Actually, some of the information in the first link(http://www.geocraft.com/WVFossils/Ca...s_climate.html ) has been contested recently - specifically, the information relating to hypothesized similarities between the Carboniferous and modern climates:
http://www.sciencedaily.com/releases/2008/07/080731140227.htm

 

[Evo]

Actually, some of the information in the first link(http://www.geocraft.com/WVFossils/Ca...s_climate.html ) has been contested recently - specifically, the information relating to hypothesized similarities between the Carboniferous and modern climates:
http://www.sciencedaily.com/releases/2008/07/080731140227.htm

I suggest that you re-read the information on the Carboniferous period from the link

Climate change during the Carboniferous Period was dominated by the great Carboniferous Ice Age. As the Earth alternately cooled then warmed, great sheets of glacial ice thousands of feet thick accumulated, then melted, then reaccumulated in synchronous cycles.

Vast glaciers up to 8,000 feet thick existed at the south pole then, moving from higher elevations to lower, driven by gravity and their tremendous weight. These colossal slow-motion tidal waves of ice destroyed and pulverized everything in their path, scraping the landscape to bare bedrock-- altering mountains, valleys, and river courses. Ancient bedrock in Africa, Australia, India and South America show scratches and gouges from this glaciation. Image credit:

Department of Environmental and Geophysical Sciences
Manchester Metropolitan University
Manchester, UK

http://www.geocraft.com/WVFossils/Carboniferous_climate.html

Your link

ScienceDaily (Aug. 1, 2008) — Geoscientists have long presumed that, like today, the tropics remained warm throughout Earth's last major glaciation 300 million years ago. New evidence, however, indicates that cold temperatures in fact episodically gripped these equatorial latitudes at that time.

 

[DDesHarn]

Ok, I re-read it. On my re-read, it seemed even more like an apology for the god-hugging-us-closer model of climate change. It is inflating a barely-tenable relationship between the Carboniferous and the modern climate for the purpose of attacking the myriad of peer-reviewed articles on climate change and global warming. Furthermore, upon reviewing his data on other parts of his (Monte Hieb's) site, I found it almost impossible to trace some of his most important sources, and those which could be traced showed additional input that was even more obscure. I also found that Hieb's main claim to fame is his work for the mining industry - not paleoclimatology.

Bottom line: the two climates are NOT analogous. Glaciation in equatorial zones is rare today at best, while the research I referenced above points to it being a feature of the Late Paleozoic climate.

 

[Evo]

Bottom line: the two climates are NOT analogous. Glaciation in equatorial zones is rare today at best, while the research I referenced above points to it being a feature of the Late Paleozoic climate.

The links I provided are in answer the op's question on continental drift.

Of course glaciation in tropical areas would be rare today due to the shift of landmasses affecting ocean circulation and temperature. You did see the maps of the land masses during that time period?