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community weblog

Something interesting is happening in Geochemistry

Dr. Lisa Welp of Purdue University has begun organizing a crowdsourced isotopic analysis of this weekend's snowstorm. (Threaded view here, just scroll down.)
posted by endotoxin on Jan 23, 2026 at 4:48 PM

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While it is fun to read all of the thread of academics signing onto the project, I would be interested to know what an isotopic analysis would measure, and what questions would this project contribute to answering?
posted by Jon_Evil at 4:58 PM

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Thanks for posting this endotoxin! I read widely in water (rain, fog, dew, snow - and flowing waters) isotopics (for stormwater and pollution solutions).

Jon_Evil - water behaves differently (esp. in biological sytems) depending on the isotopic forms of its Oxygen (16 O, 17 O, and 18 O) and Hydrogen (1H, 2H - Deuterium, 3H - Tritium) and the ratio of those in the water. e.g. snow with a high 018 content appears to be collected by trees, while the lighter fraction tends not be be held. Ratios can show where the water for that snow evaporated from - e.g. from the sea, from a forest, or from a lake.

Once that heavy snow has be caught it eventually melts and enter the soil and is held. The really weird thing is that some trees preferentially access this water a year or more later - even when they have a river crossing their root zone. On a phone so don't have refs on hand.
posted by unearthed at 5:21 PM

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If this water turns out to come from specific places in the ocean, wouldn't that put the fingerprints of Global Warming all over this catastrophic storm?
posted by jamjam at 6:24 PM

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Thanks, unearthed! One of my favorite parts of Metafilter how so quickly someone can explain to me what I'm looking at in an FPP
posted by Jon_Evil at 6:37 PM

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The trees prefer heavy water, or they prefer to use last year's water storage?
posted by PresidentOfDinosaurs at 6:38 PM

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Trees transpire vast amounts of water through their leaves, and any low temperature evaporation process will favor lighter molecules of the same compound, which in this case means that trees will end up with more O18 bearing water because it gets left behind.
posted by jamjam at 6:46 PM

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Trump says the big US winter storm is proof of climate hoax – here's why he's wrong

I think Welp's study will stuff Trump's moronic claim right back down — or up — the fetid orifice it came out of.
posted by jamjam at 7:03 PM

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Creed and Noordwijk Forest and Water on a Changing Planet: Vulnerability, Adaptation and Governance Opportunities. [International Union Forest Research Orgs. 5Mb pdf], and go to page 92 "Molecular differences in common isotopes cause fractionation during most phase transitions: {rain, snow, evaporation etc,} heavier isotopes (HDO) preferentially condense, whereas lighter isotopes (H2 16 O) preferentially evaporate."

The trees prefer heavy water, or they prefer to use last year's water storage? Both I think - (but not all trees do this, there are so many exceptions and variations it is hard ro understand), but the most concentrated 'pools' of heavy water are in the soil - and in places like California first falls as snow in the mountains." I have also read of increased snow accumulation in tree gaps in the high sierra with increased levels of heavier oxygen and hydrogen fractions.

Well worth reading: Brooks Barnard Coulombe McDonnell 2009 Two water worlds paradox: Trees and streams return different water pools to the hydrosphere. [NatureGeo Letters pdf]. A fairly mindblowing article as it indicates (among other things) that some/much of the water running off land on a very rainy day is not the rain, but is older water that's been in storage for a year or so, and this is based on isotopic differences. I've recently found a guy in china experimenting with designing stormwater systems on this basis. The Brooks paper is controversial as it threatens so many disciplines ... and engineering standards, but water is still poorly understood so expect there are many surprises yet.
posted by unearthed at 9:36 PM

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