Terrific video, thanks a lot for the time. You've explained these concepts thoroughly and clearly. This video, as a complete introduction to isotope fractionation, is unparalleled in its quality.
To "A kuitin": isotope fractionation isn't "of an" atom, but is "between" atoms. It's the separation of isotopes by different weights. Sometimes this fractionation is mass dependent, as in the examples discussed in this video, and sometimes it's mass independent, as with sulfur isotopes in early Earth history. Perhaps it would help to think of the mass difference between isotopes as a % of the total mass. Hydrogen vs. deuterium is huge then: 200% more mass in D than H. But with U-235 and U-238, that percentage is much smaller relative to the whole. It's only about a 1% difference: apparently not enough to make a difference to the physical systems which would fractionate smaller atoms of different isotopes.
The measuring of Hydrogen isotopes is new to me. Makes sense. My understanding is what you mention later in the video, in measuring the oxygen isotopes stored in oceanic creatures, like diatoms, that use the oxygen available at the time to generate a shell. And then when that creature dies and it sinks to the bottom of the ocean. Over time you get ocean floor layers that are sometimes rich in Oxygen 16/18 alternating with ones that have lower in oxygen 16, as they have evaporated and been stored in ice sheets. Cool presentation though, much more thorough in the whole picture. Your students are lucky to have a teacher like you.
you make all this isotope fractionation stuff right and clear. I`m dealing with the PETM and, as you say, some issues are somewhat tricky. Greetings from Mexico!
Thank you Callan. By far the best video out there explaining isotope fractionation. It would have been nice to include potential energy well and how fractionation is related to temperature. I would love to see more of those video about proxies used in paleoclimate. Cheers.
This is a terrific presentation. Thank you so much. Helps one understand the fundamental background science. Now I better understand how those charts and graphs are generated. More please.
These 17 minutes were the best of my day...even, when you finished I said that´s all (referring me to...I want to hear more)...it´s extremely easy to hear you and understand you...MANY THANKS!
Thank you for the clear and simplified presentation. I was looking for that equation of how to calculate the D excess using the VSMOW and its much clearer now.
Why do you show delta deuterium in one slide as the ratio of D/H, then in the next slide show delta deuterium as the ratio of H/D? That would cause the inverse, wouldn't it?
Firstly, thank you for the best explanation! I just have one question: 18O, OCEAN PART (12:44): T is growing, amount of 18O in ocean decreases due to higher amoutn of E, so the number in numerator is lower too, hence the result of ratio is lower because we are dividing by higer number of 16O? But 16O is lighter than 18O in any occasion, so during that warmer period the ratio should be still higher than in colder periods (amount of evaporated 16O is higher than amount of 18O) but evidently my cogitation is not right, so what am I missing :D
Hello Challan at 08.31 you have used H/D instead D/H as in Oxygen 18O/160 I am bit confused the heavier isotope should be in numerator as in the formula
Nice presentation. Wondering if there is evidence that life - plants have methods to select C12 (Not C13) during photosynthesis? Is it simply an axiomatic Model? As a consequence, all animals that survive on plant source of food, also needs to be C12 based without C13.
Hello - There certainly is evidence that they have "methods" in that when we measure plants' C signatures, we find a higher 12C/13C ration than in the ambient CO2. I cannot speak to the biochemical discrimination mechanism in detail, though - but the result is empirically measurable in modern plants. You're right about the trophic cascade - all else being equal, the "downstream" organisms (primary consumers, secondary consumers, etc.) would carry that same ratio forward.
hey Callan, many thanks for this enlightening video! One curiosity-question: for which elements is this isotope fractionation method available? Are rare earth elements also included, e.g. Cerium, Yttrium...? Can the isotope fractionation be employed in an industrial scale? Cheers!
I'm not sure I could quote a complete list to you of all elements that have stable isotopes that get fractionated in geological systems, but there are big ones like covered here, and some rare ones too, and there are even some like sulfur that were fractionated on means other than mass in early Earth's different conditions.
quick question who would answer the question "what isotope fractionation? because i get the concept of how it can be used to to deduce paleoclimates but what exactly is isotope fractionation of an atom fundamentally. for example when they say U 235 and 238 have little natural factionalism naturally but like H 1 and 2 deoes. what does that mean?
Probably not relevant for you anymore, but I'll respond that anyways. Isotope fractionation exists when there exists some mecanism that prefers one isotope over another. For example evaporation "prefers" lighter water molecules over heavier molecules. This means that lighter water molecules are more likely to evaporate than heavier molecules. This natural process tends to enrich the oceans in Deuterium (because they have a hard time getting out) and enrich the atmosfere with normal Hydrogen. U235 and U238 on the other hand have no or very little natural fractionalism, because there is no important process that prefers U235 over U238 or viceversa. To name some examples: None of those two uranium isotopes "evaporate" in our atmosfere, so you cannot say that U235 evaporates more readily than U238. Also, there are no living organisms that use Uranium, so by logic there exist no living organisms that prefer one isotope of uranium over the other.
why didn't you mention the influence of water vapor on atmospheric temperature. Water vapor is a bigger player in global temperature than CO2. Regardless, thank you for the video!
