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#paleoclimate

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Loving the discussion surrounding this @PNASNews publication on Phanerozoic #paleo #temperature evolution, one of the most interesting #paleoclimate discussions in my opinion.

pnas.org/doi/10.1073/pnas.2400

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.

pnas.org/doi/10.1073/pnas.2424

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

raisedbeaches.buzzsprout.com/2

doi.orgTowards quantitative reconstruction of past monsoon precipitation based on tetraether membrane lipids in Chinese loessAbstract. Variations in the oxygen isotope composition (δ18O) of cave speleothems and numerous proxy records from loess–paleosol sequences have revealed past variations in East Asian monsoon (EAM) intensity. However, challenges persist in reconstructing precipitation changes quantitatively. Here, we use the positive relationship between the degree of cyclization (DC) of branched glycerol dialkyl glycerol tetraethers (brGDGTs) in modern surface soils from the Chinese Loess Plateau (CLP) and mean annual precipitation (MAP) to quantify past monsoon precipitation changes on the CLP. We present a new ∼ 130 000-year-long DC-based MAP record for the Yuanbao section on the western edge of the CLP, which closely tracks the orbital- and millennial-scale variations in available records of both speleothem δ18O and the hydrogen isotope composition of plant waxes (δ2Hwax) from the same section. Combing our new data with existing brGDGT records from other CLP sites reveals a spatial gradient in MAP that is most pronounced during glacials, when the western CLP experiences more arid conditions and receives up to ∼ 250 mm less precipitation than in the southeast, whereas MAP is ∼ 850 mm across the CLP during the Holocene optimum. Furthermore, the DC records show that precipitation amount on the CLP varies at both the precession scale and the obliquity scale, as opposed to the primarily precession-scale variations in speleothem δ18O and δ2Hwax at Yuanbao and the 100 kyr cycle in other loess proxies, such as magnetic susceptibility, which rather indicates the relative intensity of the EAM. At the precession scale, the DC record is in phase with δ2Hwax from the same section and the speleothem δ18O record, which supports the hypothesis that monsoon precipitation is driven by Northern Hemisphere summer insolation.
Replied in thread

@edwiebe
So. Hansen tandfonline.com/doi/full/10.10 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 climatejustice.social/@anlomed

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?

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.

#Paleoclimate #AMOC #YoungerDryas #ClimateChange #Volcano

doi.org/10.1126/sciadv.adt4057

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

awi.de/ueber-uns/service/press

www.awi.dePresse Detailansicht - AWI

@DrEvanGowan

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.
fediscience.org/@DrEvanGowan/1

#paleoclimate
#Milankovich
#cycles
#climate
#iceAge

FediScience.orgDr. Evan J. Gowan (@DrEvanGowan@fediscience.org)Episode 4 of the Raised Beaches Podcast, a podcast on paleoclimate and global change is out! The deep dive in this episode is on Milankovitch Cycles. Get it on Buzzsprout or wherever you get your podcasts. In the intro, I discuss Holocene sea level changes in Okinawa, the Aso Caldera, ammonite fossils, and an overview of my activities in 2024. For the deep dive, I discuss Milankovitch Cycles, the three types of orbital changes and how they affect climate, as well as the LR04 benthic δ¹⁸O and Chinese speleothem δ¹⁸O proxy records, that demonstrate the orbital control on climate change. In the further discussion, I discuss how James Croll originally proposed an orbital control on climate change before Milankovitch, why Charles Darwin was a fan, and why Croll's theory was not accepted. I also show how Milankovitch Cycles also affect the climate of Mars. In the papers section, I discuss one paper by Rubio-Sandoval et al (I am a coauthor) on deducing paleo sea level in Camarones, Argentina. There are four periods of higher-than-present sea level at this location. (link in the next post) I will be posting the video version of this podcast in the coming days! #Podcast #ClimateChange #Paleoclimate https://www.buzzsprout.com/2401751/episodes/16354340-episode-4-milankovitch-cycles
Replied in thread

@rahmstorf

Does anyone here know how or when AMOC is restarted after a shutdown?
How it used to get restarted in past climate changes. And how that restart would play out under our unusual changed factors?

I was thinking that maybe, a restart requires all Milankovic cycles to sufficiently favour Northern Hemisphere. And the process would be that sufficiently warmer summer temperatures over the Northern North Atlantic manage to evaporate enough ocean water for it to become saltier – and that would kickstart convection in place, with strictly local conditions as the first engine.

All 3 Milankovic cycles sufficiently favouring Northern Hemisphere, that's in about 120,000 years....

Earth May Have Had A Ring System 466 Million Years Ago
--
phys.org/news/2024-09-earth-mi <-- shared technical article
--
doi.org/10.1016/j.epsl.2024.11 <-- shared paper
--
“HIGHLIGHTS:
• Earth may have had a ring during the middle Ordovician, from ca. 466 Ma.
• Breakup of an asteroid passing within Earth's Roche limit likely formed the ring.
• Among several features preserved is a near-equatorial band of impact craters.
• Shading of Earth by the ring may have triggered a global icehouse period…”
--
#GIS #spatial #mapping #model #modeling #geology #structuralgeology #planetarygeology #rings #climatechange #paleoclimate #Ordovician #asteroid #rochelimit #craters #impactcrater #crater #icehouse #meteorite #platetectonics #HirnantianIcehouse