Really high quality video following glacier scientists in New Zealand utilizing new techniques for fine tuning our understanding of glacier melt over long periods.
Worth watching and bookmarking for the photography alone, but extremely interesting science here. Only 8 minutes, from the Department of Education at the American Museum of Natural History
Description:
Analysis of Earth’s geologic record can reveal how the climate has changed over time. Scientists in New Zealand are examining samples from the rocky landscape once dominated by glaciers. They are employing a new technique called surface exposure dating, which uses chemical analysis to determine how long minerals within rocks have been exposed to the air since the glaciers around them melted. Comparisons of this data with other climate records have revealed a link between glacial retreat and rising levels of carbon dioxide in the air, findings that are informing scientists’ understanding of global climate change today.
Thanks Peter. That video is awesome.
To those not already aware, the message of this video could be misconstrued as being that increased CO2 in the atmosphere caused glaciers to start melting 20k years ago. The video-makers therefore appear to assume the viewer understands the underlying physics: This research is all about confirming the date (using this Berylium-10 technique to date the emergence of boulders from the ice) of the onset of retreat. This resulted from the natural warming of the atmosphere at the end of the last Ice Age (due to changes in Earth’s orbit – axial inclination, eccentricity, etc). This caused the incoming radiation from the Sun to be more effective at warming the planet, which induced an energy imbalance that was eliminated by CO2 being released from warming oceans (trapping more longwave radiation).
To those inclined to misrepresent or misunderstand palaeoclimatolgy, I would therefore wish to point out the following: The message of this video is that we now have a problem because we are artificially increasing atmospheric CO2, which will require the Earth to warm up in order to re-establish a new artificial equilibrium between incoming (solar) and outgoing (longwave) radiation.
N.B. I am not trying to talk down to anybody; I am merely trying to forestall the appearance of any bogus/strawman arguments.
https://lackofenvironment.wordpress.com/2012/03/19/ice-age-not-for-60-thousand-years-if-ever/
Correct me if I’m wrong, but my understanding was that while orbital changes do force a little warming/cooling, the way it normally goes is that the axis shifts, there’s slight warming, which triggers a rise in CO2, and that does the rest of that work in pushing back the glaciers between ice ages.
Am I missing something?
I don’t think so (I think we are both right).
My point is that the video appears to suggest the glacier retreat can be correlated with CO2 increases, which is clearly not the case. The glaciers retreat because it gets warmer; whereas there is a time lag of several hundred years between the warming and the CO2 increase.
Contrast this situation with what we have now: We have added a whole load of CO2 to the atmosphere much faster than what happened at the end of the last Ice Age – causing a much prompter increase in temperature.
In short, it does not matter which increases first (temperature if natural; CO2 if artificial) – a change in one will always induce a change in the other – because this is the only way any radiative energy imbalance can be eliminated.
I guess I would just caution you to be careful of how you phrase that, because I still run into people who go with the “CO2 lags temperature” crock, and your comment could be used to support that by dishonest people/deniers.
http://www.skepticalscience.com/co2-lags-temperature.htm
Unless a contextomy is performed on them, my comments completely refute the CO2 lags temperature argument (i.e. because it was true then [natural warming] but is not true now [artificial warming]).
Fair enough.
Question: How can they determine if the Beryllium10 was created before or after the glacier spit it out? Perhaps it was a surface rock already when the glacier picked it up?
experts weigh in, but I’m guessing Berryllium decays at a known rate into specific daughter isotopes that can also be measured?
I would also assume Be-10 is not a naturally occurring isotope. Therefore it’s presence today can be used to determine the date it was created because we know its half-life.
http://en.wikipedia.org/wiki/Beryllium-10
I’m not positive, but I think stones tend to get ground around a bit in glaciers – it’s unlikely that even if it WAS a surface stone, the original pre-glacier surface layer of the rock would still be there by the time it got left behind.
Ah Yes! Now I get the reason for the question; and I don’t have a better answer than that one.
I’ll buy that, plus since they are taking multiple samples from the area, it’s unlikely that one anomalous stone would skew the results.
Shane,
Good questions. I’m no expert here but that won’t stop me from thinking.
Re: “How can they determine if the Beryllium10 was created before or after the glacier spit it out?”
Cosmic rays are directional. So you sample the surface exposed to the Sun and the bottom of the glacial erratic for a sample that is shaded from cosmic rays. Note the difference in Beryllium-10. http://en.wikipedia.org/wiki/Surface_exposure_dating
See also Lichenometry which will give a good indication as to how long a boulder (glacial erratic) is likely to have been at its present location: This is the old “moss grows on the North side” woodsman’s wisdom. (Does not apply in New Zealand!) http://en.wikipedia.org/wiki/Lichenometry
Re: “Perhaps it was a surface rock already when the glacier picked it up?
Consider Half Dome in Yosemite Park. http://en.wikipedia.org/wiki/Half_Dome At one point in time this geological feature would have been called Whole Dome. Until glaciers repeatedly sweep down the Merced River Valley and took the surface and whole lot more away from the front face of Half Dome. I’m being somewhat facetious, of course. But from my time examining glacial erratics from California to Alaska, I’ve found it easy to tell if the surface has been well rounded such as you’ll find in river boulders or sharply delineated as would be the case with rock recently fractured and pulled from the bedding material and place as an erratic on dry land typically in moraines.
Thanks for the detailed answer! I’m not a scientist but I am trained to think in terms of “how could this process break” for my profession as a software developer so I’m always trying to think through any holes in the logic of an idea.