Enjoyed reading about this nice study @Palaeo3 about the relationship between Li/Ca ratios in #brachiopods and #temperature. The #dataset looks very robust and the empirical relationship highly promising for #paleoclimate #reconstructions!
https://www.sciencedirect.com/science/article/pii/S0031018225002135
Heading to the KR10 conference to present work in this and other #caves in #Utah. #geology #earthscience #climate #paleoclimate #science
Loving the discussion surrounding this @PNASNews publication on Phanerozoic #paleo #temperature evolution, one of the most interesting #paleoclimate discussions in my opinion.
https://www.pnas.org/doi/10.1073/pnas.2400434121
Critique: 6-10 degrees #tropical #ocean #temperatures during the #Ordovician seem very low to me, especially considering that in this time (450 million years ago) corals were thriving. The critical comment by Ethan Grossman and colleagues therefore seems fitting.
Exciting work studying the chemical bonds in membrane lipids of #archaea (#marine #microbes) which are often used for #paleoclimate reconstructions suggests improvements to #temperature reconstructions.
https://www.sciencedirect.com/science/article/pii/S0012821X25000925
I have released episode 5 of the Raised Beaches Podcast, a podcast about paleoclimate, Earth science and global change! This episode's deep dive is on the greenhouse effect. Get it in the following link or wherever you get your podcasts.
In the intro, I talk about going to watch Sakurajima Volcano erupt, an earthquake I felt in January, my efforts to download data from NOAA and how US government agencies are being shut down, and a commentary on DEI.
I discuss in the deep dive how the greenhouse effect works, and why greenhouse gases are needed to keep the planet inhabitable. In the second part I discuss the history of the discovery of the greenhouse effect and how it got its name, and the greenhouse effect on Venus and Mars.
Finally, I discuss in the papers section a recent paper I am coauthor on, led by Alessio Rovere, about determining past sea level position from a beach ridge in Argentina. I discuss 4 other papers.
#Paleoclimate #ClimateChange #Podcast #SeaLevel #NOAA #Volcano
https://raisedbeaches.buzzsprout.com/2401751/episodes/16758479-episode-5-the-greenhouse-effect
"What previous studies have labelled an ‘AMOC collapse’ is now called ‘no collapse’. It’s essentially a discussion about semantics, not physics. Do you call it an AMOC collapse if a weak and shallow wind-driven overturning persists after the thermohaline part has collapsed? Or not?"
https://www.realclimate.org/index.php/archives/2025/02/how-will-media-report-on-this-new-amoc-study/
Rahmstorf about the new #AMOC paper misleadingly titled "Continued Atlantic overturning circulation even under climate extremes" https://www.nature.com/articles/s41586-024-08544-0
Good to know.
Now I think that maybe Jochem Marotzke, cli-sci at the Max Planck Institute for Meteorology in Hamburg, also applies semantics when he says that collapse can't occur – and in a new sentence then explains the fact that the Gulf Stream is purely wind-driven and will never shut down.
If this is his only argument against "AMOC Collapse", it's a weak one.
But I also heard him say something like, that the freshwater input isn't available that's required for making AMOC react like in #paleoclimate .
***
We do know how much water comes today from Greenland, from the Alpes and from Canada's remaining glaciers.
And compared to what melted during the last deglaciation, it's a tiny amount.
But we don't know how much more it rains on the Northern #Atlantic ocean compared to pre-Holocene times when it was so much colder up there in the North.
We don't even know how much it rains in the AMOC-relevant regions today.
Also, ice models for the deglaciation do differ a lot in the AMOC-relevant regions, both for land-bound ice and #seaice, if they even bother to model sea ice at all.
On this #InternationalDayOfWomenAndGirlsInScience, here is a great story presented in two papers led by a #WomanInScience (Jingjing Guo) and last authored by another #WomanInScience (Francien Peterse).
#Scientific #publication #1: https://doi.org/10.5194/cp-21-343-2025
Scientific publication #2: https://doi.org/10.1016/j.orggeochem.2025.104947
#Science
#ScienceMastodon
#AcademicMastodon
#PaleoClimate
#PaleoHydrology
#EastAsianMonsoon
#PaleoTemperature
#OrganicGeochemistry
#GDGTs #brGDGTs
#ClimateProxies #Loess
#IDWGS #IDWGS2025
"The first #Europeans weren’t who you might think." They pretty much were, given what we know about #geography, #paleoclimate, and #human #evolution—but generations of ideologues successfully argued otherwise. Implications for the modern world are left as an exercise for the reader.
@edwiebe
So. Hansen https://www.tandfonline.com/doi/full/10.1080/00139157.2025.2434494#d1e386 projects the same effect of SO2 on ocean cloud cover as on land. I think, the further inland we go, plants dominate the hydrological cycle, pheromones "VOC" the cloud seeding. Recovering from acid rain & prolonged growing seasons even increase
seeding.
I think.
Maybe not in the tropics where C3 plants are nearing their heat limit earlier than in mid and high latitudes.
But my point is, land reacts differently to SO2 poisoning and should be incorporated in projections, no?
***
Another matter is ice melt and AMOC.
Hansen says that today's melt in Greenland can cause AMOC to tip within 20-30 years.
How does today's freshwater input compare to the big thaw coming out of the ice age which turned AMOC off?
All of North-Eastern America and all of Scandinavia and Scotland melted and directly influenced AMOC's western and eastern branch respectively.
How much was that? Much more than today?
Also, all those ice shields plus West Greenland were ice free in the long interglacial 409thsd years ago.
But AMOC did not stop.
And if melt speed matters:
so far, East Greenland's warming rate is the same 0.35°C/decade as it was in the 2 steep warmings pre-Holocene. See more info on my chart here https://climatejustice.social/@anlomedad/113853576092288476
Less ice is melting (I assume), same warming rate...
how could this make AMOC tip within the next 100 years even?
I read 2 papers by vanWesten's team, and Rahmstorf's recent blog on RealClimate and last year's TOS overview paper, and many more on AMOC.
But I couldn't find a single one on Scholar-Google that puts a number on freshwater input from melting ice in both, today's melt and in #paleoclimate times.
I understand that rain due to increased temperatures plays a role too. And I understand that we don't know how much that is or was over the oceans. Certainly, rain is now much more than when temperatures were much colder before the Holocene.
But how the amount of melted ice in the AMOC-influencing areas compares should be known, no?
On my way to #utah to make a presentation about research in this and other #caves in the Uinta Mountains. #geology #cave #caving #paleoclimate #earthscience
Warken et al precisely date the Laacher See volcanic eruption (in central Germany) from a speleothem record, which allows them to precisely define when the eruption happened relative to the start of the Younger Dryas. They find that the timing of the eruption (13,008 yr BP) is at least 150 years before the start of the Younger Dryas, precluding any causal relationship between the eruption and the Younger Dryas. The results from the speleothem also show that the cooling in Europe from the Younger Dryas after the AMOC shutdown happened abruptly.
The last time, today's warming rate happened was during deglaciation, see ice core from Greenland.
It was so fast that the AMOC stopped. Which also re-froze Scotland and Scandinavia for a while. Scotland was a wall of ice 800 m tall!
But the Earth's orbital cycles drove further warming, #AMOC restarted – and our stable #Holocene began.
The chart shows decadal average temperature in °C from Renland in East Greenland and a short contemporary time series from a weather station 600km further North at the coast in Danmarkshavn. To visualise the similar warming rates a little better, Danmarkshavn's data was copied in at the 2 previous periods of fast rising temperatures in Renland.
Noteworthy: the 2 steep warming periods took about 300 years each and covered first 10 and then 8 °C. Roughly 0.33°C per decade.
While Danmarkshavn saw a rise of 0.35 per decade since 1980.
#PaperClub is back for the start of 2025, and we're kicking off with Patterson et al (2024), who present a PCP-corrected stalagmite d18O record from Vietnam, spanning 45-4 ka. Interesting paper, and the whole 'PCP impacts on d18O' thing has been getting quite a lot of airtime in recent years. Hopefully without sounding like a hater, I remain a bit skeptical. In this instance, the model assumptions include a feeding stalactite drip rate of 1 drip/second, which seems too high for LGM (where PCP effect on the stal was greatest). For stalactite PCP to be recorded in a stalagmite, there must not be sufficient residence time for re-equilibration to occur. I would love to see a sensitivity test of the drip rate on the model.
Growth rates during the 'peak PCP' period were also extremely low (<5 um/yr), which suggests to me that growth was likely not continuous over the period. d18O vals were high, I assume there was greater opportunity for disequilibrium to drive the signal rather than PCP?
Anyway, I'm definitely no expert in d18O kinetics, and I'm looking forward to hearing the opinions of the group, and anyone else who has read the paper :) I am really happy to be wrong about this, as there are lots of clever people on the paper who know more than me about this stuff!
#Paleoclimate #Speleothems #speleology
https://www.nature.com/articles/s41467-024-53422-y
In an ocean of bad news, here's some science excitement - the beyond EPICA team has announced they've drilled an ice core dating continuosly to 1.2 million years ago!! This core will give key information about the transition to the 100-000 year earth - the cycle of glacials and interglacials in which we currently live. So cool (pun intended).
#Antarctica #paleoclimate #IceIceBaby #IceCore #ClimateScience
The introduction speaks of organic material in #seaice originating from the Siberian coast that got squeezed toward the central #Arctic ice by the wind-driven Trans Polar Drift.
But Siberia wasn't part of the Eurasian ice sheet, it was ice free during the last glacial. (Which surprises me bigly! )
No wonder then, that its coast, and further out, also wasn't covered in sea ice year round.
And therefore, ice fields drifting toward the Arctic centre containing organic material from Siberia's coast is not a surprise.
May be, there's a process that cuts off the bottom layer of the inflowing ice once it encounters a more massive top ice field. And the bottom layer then keeps the strength of the push for a while longer. Thus, transporting its organic content further toward the centre?
@DrEvanGowan has released a fine new episode of Raised Beaches podcast, about Milankovich cycles! In recent centuries, industrial CO2 has drowned out Milankovich cycles, but Milankovich cycles were a major factor in climate change during the Pleistocene and Pliocene (and presumably before). Bonus: Mars has Milankovich cycles as well.
https://fediscience.org/@DrEvanGowan/113740539812374781
Another excellent edition of Quaternary Australasia is out! I always enjoy the post-conference student reports, especially when the students seem to have really gotten into the 'AQUA vibe'!
Oh, wait, just a second...
When AMOC hickupped during LGM or deglaciasation, global sea level was 120m lower than today.
My musings wrt (sea) ice melt back then compared to today, and its impact on AMOC transport speed should also consider that coastal ice wasn't sea ice at all due to lower sea level.
Dunno for sure, but continental ice could have covered the very shallow Norwegian sea all the way up to Svalbard.
Arctic ocean also has ocean currents that somehow interact with AMOC. Sea ice formation helps driving ocean currents.
When less area was covered by ocean, sea ice formation was less which must have influenced Arctic ocean currents, and therefor, AMOC in paleoclimate.
Today's Arctic sea ice loss has already altered, weakened or stopped a bottom water current that goes right through the centre of the Arctic sea. Don't recall its name now, maybe starts with a T or L...?
And wasn't Alaska also connected to Siberia, and hence no water from the Pacific entered the Arctic sea to drive currents and influence AMOC?
Anyway, whether or not any Arctic ocean currents existed during LGM or deglaciasation, when sea ice formation was greatly reduced all around the Arctic coast, is also something to bear in mind when comparing the causes of a tipping paleo AMOC with the causes of the tipping potential of an #EconObscene AMOC.
Antarctic sea ice formation wouldn't have been reduced from lower sea level, tho. Not impeded by <surrounding> land area, it just formed further out. That's all.
Still haven't gotten around comprehending how to convert a lat-lon grid with ice thickness to a correct regional sum of freshwater amount in Gt.
But something else keeps popping up in my head now.
Peltier's ice model / reconstruction (dunno which it is) doesn't include sea ice at all https://www.atmosp.physics.utoronto.ca/~peltier/data.php
Tarasov's GLAC1D model does. https://doi.org/10.5281/zenodo.10159104
At least the melted parts of sea ice is included. But not the ever-lasting part.
That ever-lasting part is melting today, and has been melting for a long while now. But it didn't melt during past AMOC hickups. What melted back then was ice that covered Scotland with a whopping 400m ice wall. And higher ice mountains still melted in other regions. But not sea ice in the Arctic ocean.
...hm. What I really want to know is how the amount of freshwater influx back then
compares to the amount today, and how today's very little left-over ice would be capable of stopping AMOC.
We'll be having a blue Arctic ocean before 2030, says a new study https://www.ft.com/content/63fbcf2b-9acc-4ccb-ac12-9f3b78e85b68
https://www.nature.com/articles/s41467-024-54508-3 #Heuze and #Jahn 2024, "The first ice-free day in the Arctic Ocean could occur before 2030" #openaccess 
Wouldn't it be cool to know by then how much ice in kilos or Gt melted ? And how that amount compares to the amount before previous AMOC shutdowns during the LGM and deglaciasation?
Explore AGU Paleo Section Awards: Contribute to Science
The American Geophysical Union Fall Meeting (#AGU24) is next week. Which means that it is time for my regular message on behalf of the AGU Paleoceanography and Paleoclimatology section to say: please consider nominating someone for one of the section awards in 2025....
http://andy-baker.org/2024/12/05/explore-agu-paleo-section-awards-contribute-to-science/
