Archive for the ‘paleo’ Category

Canadian Arctic archipelago [via Wikipedia]


The clue is in the study title: The importance of Canadian Arctic Archipelago gateways for glacial expansion in Scandinavia.
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A new study led by University of Arizona researchers may have solved two mysteries that have long puzzled paleo-climate experts (says Phys.org): Where did the ice sheets that rang in the last ice age more than 100,000 years ago come from, and how could they grow so quickly?

Understanding what drives Earth’s glacial–interglacial cycles—the periodic advance and retreat of ice sheets in the Northern Hemisphere—is no easy feat, and researchers have devoted substantial effort to explaining the expansion and shrinking of large ice masses over thousands of years.

The new study, published in the journal Nature Geoscience, proposes an explanation for the rapid expansion of the ice sheets that covered much of the Northern Hemisphere during the most recent ice age, and the findings could also apply to other glacial periods throughout Earth’s history.

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Arctic sea ice [image credit: cbc.ca]


The researchers find ‘a significantly declining AA effect on the millennial time scale’ — but then attempt to link that to anthropogenic forcing in recent times, according to the article at least. That seems illogical if the argument is that humans are playing a part. In any case if the effect has been shown to occur over at least a millennium, that in itself casts doubt on claims that humans must be the prime (or any) cause of the most recent observed changes.
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The recent amplified warming in the Arctic during the last decades has received much attention, says Phys.org.

But how Arctic amplification (AA) has varied on longer time scales and what drives these variations remain unclear.

Recently, a study has provided a new perspective on the AA effect during the past millennium based on the best available paleoclimate data and novel data assimilation methods.

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The author notes, with examples, that ‘it is difficult to reconcile this latest research with many other lines of inquiry to determine past temperatures.’ Using a single computer model to ‘fill in gaps’ in data has its own drawbacks, as mentioned below.
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Modern warming differs from the gradual rise in temperature seen in the past 10,000 years. That’s the conclusion of a paper just published in the journal Nature, says David Whitehouse.

Reconstructing the temperature timeline back to 24,000 years ago – the so-called Last Glacial Maximum – a team of researchers show that recent warming is unusual.

Knowledge of past climate is important to put our present climate into context, allowing us to see what climatic variations can take place in the absence of contemporary amounts of greenhouse gasses.

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Diagram showing solid-body rotation of the Earth with respect to a stationary spin axis due to true polar wander. [Credit: Wikipedia]

The researchers say their finding ‘challenges the notion that the spin axis has been largely stable over the past 100 million years.’
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We know that true polar wander (TPW) can occasionally tilt whole planets and moons relative to their axes, but it’s not entirely clear just how often this has happened to Earth, says ScienceAlert.

Now a new study presents evidence of one such tilting event that occurred around 84 million years ago – when dinosaurs still walked the Earth.

Researchers analyzed limestone samples from Italy, dating back to the Late Cretaceous period (100.5 to 65.5 million years ago), looking for evidence of shifts in the magnetic record that would point towards an occurrence of TPW.

Bacteria fossils trapped in the rock, forming chains of the mineral magnetite, offer some of the most convincing evidence yet of true polar wander in the Late Cretaceous – and it may help settle a scientific debate that’s been going on for decades.

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drought-CA-july-2021

La Niña pending

Natural climate change has always been around, as this study indicates. Attempts at attribution of weather-related conditions like droughts to recent (in historical terms) fuel-burning activities are full of pitfalls and uncertainties.
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A team of researchers at Columbia University has shown that long-term droughts in southwestern parts of North America and in southwestern parts of South America have occurred at the same time on multiple occasions over the past 1,000 years coinciding with La Niña events, reports Phys.org.

In their paper published in the journal Nature Geoscience, the group describes how they used archival data and paleoclimate proxies (materials preserved in the geologic record that can be used to estimate climate conditions) to create climate models.

La Niña events are climatic occurrences that are kicked off when trade winds in the Pacific Ocean are pushed toward Asia. This results in a cooling effect in the waters off the coasts of North and South America. It pushes the jet stream northward just enough to create drier conditions across parts of both continents.

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EarthspaceScientists previously proposed 26 million year cycles of mass extinctions, but this appears to correct the period. They suggest ‘cycles of activity in the Earth’s interior’ could be behind their new period, but then say: ‘However, similar cycles in the Earth’s orbit in space might also be pacing these events.’ Their study also says ‘a strong secondary signal occurs at a period 8.9 Myr’.
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Geologic activity on Earth appears to follow a 27.5-million-year cycle, giving the planet a ‘pulse,’ according to a new study published in the journal Geoscience Frontiers. Phys.org reporting.

“Many geologists believe that geological events are random over time. But our study provides statistical evidence for a common cycle, suggesting that these geologic events are correlated and not random,” said Michael Rampino, a geologist and professor in New York University’s Department of Biology, as well as the study’s lead author.

Over the past five decades, researchers have proposed cycles of major geological events—including volcanic activity and mass extinctions on land and sea—ranging from roughly 26 to 36 million years.

But early work on these correlations in the geological record was hampered by limitations in the age-dating of geologic events, which prevented scientists from conducting quantitative investigations.

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Image credit: ScienceDaily


This has echoes of the ice age dust/albedo theory – with no CO2 feedbacks – proposed by Ralph Ellis a few years ago. The article concludes: ‘The result thus has the potential to aid the understanding of the abrupt warming and cooling periods during the ice ages called Dansgaard/Oeschger events which bear the marks of climate tipping points.’

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Every late winter and early spring, huge dust storms swirled across the bare and frozen landscapes of Europe during the coldest periods of the latest ice age, says Phys.org.

These paleo-tempests, which are seldom matched in our modern climate frequently covered Western Europe in some of the thickest layers of ice-age dust found anywhere previously on Earth.

This is demonstrated by a series of new estimates of the sedimentation and accumulation rates of European loess layers obtained by Senior Research Scientist Denis-Didier Rousseau from Ecole Normale Supérieure in Paris, France, and colleagues.

The work, which is published in Quaternary Science Reviews is part of the TiPES project on tipping points in the Earth system, coordinated by The University of Copenhagen.

In the study Denis-Didier Rousseau and colleagues reinterpreted layers in loess from Nussloch, Germany.

Loess is a fine-silt-sized earth type found all over the world. It mainly consists of aeolian sediments, which are materials transported by the wind from dry areas without vegetation such as deserts of any type, moraines, or dried-out river beds.

Within the aeolian sediments, darker layers of paleosol alternate within the loess layers. Every layer in the loess represents a shift in climatic conditions.

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Some interesting theorising arises from this research, but as one expert commented: “These new data may raise more questions than they answer.” At least one existing belief about long-term climate change finds itself challenged.
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The retreat of North America’s ice sheets in the latter years of the last ice age may have begun with “catastrophic” losses of ice into the North Pacific Ocean along the coast of modern-day British Columbia and Alaska, scientists say.
[Science News reporting].

In a new study published October 1 in Science, researchers find that these pulses of rapid ice loss from what’s known as the western Cordilleran ice sheet contributed to, and perhaps triggered, the massive calving of the Laurentide ice sheet into the North Atlantic Ocean thousands of years ago.

That collapse of the Laurentide ice sheet, which at one point covered large swaths of Canada and parts of the United States, ultimately led to major disturbances in the global climate (SN: 11/5/12).

The new findings cast doubt on the long-held assumption that hemispheric-scale changes in Earth’s climate originate in the North Atlantic (SN: 1/31/19).

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Image credit: theonlinefisherman.com


A rare chance to brush up on your *vesicle paleobarometry* — or to put it another way, learn that air pressure at sea level has not always been around the 1 bar (1000 mb) that we expect to find nowadays. According to the ideal gas law, pressure and temperature are closely related, implying historic climate variability, but results so far seem inconclusive.

NASA says:
Researchers supported in part by the NASA Astrobiology Program have attempted to better understand global barometric pressure on Earth during the Archaean by studying vesicle sizes in 2.9 billion year-old lavas that erupted near sea level.

Today, Earth’s global barometric pressure is 1 bar at sea level. However, barometric pressure has changed throughout the planet’s history.

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A recent review article on PNAS titled ‘Astronomical metronome of geological consequence’ by Linda Hinnov makes interesting reading for talkshoppers.

A Brief Retrospective
In geology, a reliable “metronome” in the geologic record with a sufficiently short repeat time would greatly enhance the resolving power of the geologic timescale. Astronomers recognized the potential importance of a dominant 405-ky cycle in Earth’s orbital eccentricity variation for supplying such a metronome (2, 3), leading geologists to turn to the stratigraphic record of astronomically forced paleoclimate change to search for this cycle. In fact, one of the first geological studies to describe 405-ky scale stratigraphic cycling was on the Triassic–Jurassic Newark Basin lacustrine strata (4, 5) recovered in the National Science Foundation-funded Newark Basin Coring Project, in which each of the prominent 60-m-thick McLaughlin cycles in the cored sequence was assigned a 412.885- ky periodicity based on a now-legacy analytical astronomical solution, BRE74/BER78 (6, 7). Since the 1990s, there have been dozens of reports for strong 405-ky scale cycles in stratigraphic sequences from around the world that appear to bear out this astronomical calculation (8).

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1989 Loma Prieta earthquake damage [image credit: H.G. Wilshire, U.S. Geological Survey]


Smaller quakes seem to have taken over, for the time being at least. The Loma Prieta earthquake of 1989 in Northern California had a magnitude of 6.9 but was not considered to be ‘major’, despite some deaths and billions of dollars worth of damage.

There have been no major ground rupturing earthquakes along California’s three highest slip rate faults in the past 100 years, reports ScienceDaily.

A new study concludes that this current ‘hiatus’ has no precedent in the past 1000 years.

U.S. Geological Survey researchers Glenn Biasi and Kate Scharer analyzed long paleoseismic records from the San Andreas, San Jacinto and Hayward Faults for the past 1000 years, to determine how likely it might be to have a 100-year gap in earthquakes across the three faults.

They found that the gap was very unlikely — along the lines of a 0.3% chance of occurring, given the seismic record of the past 1000 years.

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Impact [image credit: karbalion.com]


This time, unusually, the new Younger Dryas evidence is from way below the equator, which they believe shows that ‘the Younger Dryas climatic onset was an extreme global event’.

When UC Santa Barbara geology professor emeritus James Kennett and colleagues set out years ago to examine signs of a major cosmic impact that occurred toward the end of the Pleistocene epoch, little did they know just how far-reaching the projected climatic effect would be, says Phys.org.

“It’s much more extreme than I ever thought when I started this work,” Kennett noted. “The more work that has been done, the more extreme it seems.”

He’s talking about the Younger Dryas Impact Hypothesis, which postulates that a fragmented comet slammed into the Earth close to 12,800 years ago, causing rapid climatic changes, megafaunal extinctions, sudden human population decrease and cultural shifts and widespread wildfires (biomass burning).

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Open Letter to
Honorable Prime Minister of Fiji and President of COP23
Frank Bainimarama
Mr. President,
The community assembled at the COP23 meeting in Bonn badly wants
temperature to rise according to models proposed (but never verified, rather
seriously contradicted) and sea level changes that may pose serious flooding
threats to low lying coasts provided sea level would suddenly start to rise at
rates never recorded before (which would violate physical laws as well as
accumulated scientific knowledge over centuries).

sea-level-fiji

Figure 2. Sea level changes in the Yasawa Island of Fiji (from Mörner & Matlack-Klein, 2917c). Sea level was high in the 16th and 17th century (1), low in the 18th century (2) and at about the present level over the 19th, 20th and early 21st centuries (3) with a somewhat higher level in the early 19th century and with a perfectly stable sea level during the last 50-70 years as indicated by C14-dated microatolls at multiple sites. Consequently there is a total absence of a present sea level rise – i.e. the threat of a future flooding is lifted off.

We have been in your lovely country and undertaken a detailed sea level
analysis, which beyond doubts indicates that sea level is not at all in a rising
mode, but has remained perfectly stable over the last 50-70 years. Hence all
threats of an approaching general sea level flooding is totally unfounded.
Whatever economy, politics and project agendas may want to put in the centre,
the true scientific community must insist that only facts as revealed in nature
itself and in laboratory experiments can provide trustworthy results.
These are the facts:
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YDBfield
Is this the last word on the mysterious Younger Dryas period? It’s an interesting, if not entirely new, hypothesis at least.

At the end of the Pleistocene period, approximately 12,800 years ago—give or take a few centuries—a cosmic impact triggered an abrupt cooling episode that earth scientists refer to as the Younger Dryas, reports Phys.org.

New research by UC Santa Barbara geologist James Kennett and an international group of investigators has narrowed the date to a 100-year range, sometime between 12,835 and 12,735 years ago. The team’s findings appear today in the Proceedings of the National Academy of Sciences.

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Guest post from Ben Wouters

Geothermal flux and the deep oceans.

To appreciate how the small geothermal flux of ~100 mW/m2 can play a significant role in our climate we’ll take a look at a cross-section of the Pacific in Fig 1.

fig1

Fig 1

A typical temperature profile is given in Fig 2 below

Fig 2

Fig 2

First the profile below ~1000 m. Slowly decreasing temperature with depth, more or less the same for all latitudes. The dark blue layer (~30 C) can be regarded as the top of the cold deep oceans. From 1000 m. upward the temperature increases rapidly, warmest water at the surface in the (sub) tropics. The dark blue layer only reaches the surface at high latitudes (red arrows). All water above this dark blue layer is warmed from above by the sun, either directly or indirectly. This layer also loses its energy again at the surface to the atmosphere, and eventually to space. Solar energy only warms the upper ~1000 m. between ~50N and 55S. How high the surface temperatures will be, depends on the temperature of the deep oceans and how much the sun can warm the upper layer above the deep ocean temperature.

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Guest post from Jeremy Shiers (@JeremyShiers), whose blog is at http://jeremyshiers.com/

Temperatures were 2ºC warmer 5000 years ago according to
archaeological and geological evidence from Skara Brae in Orkneys,
Scotland

Professor Ian Stewart presented the series Making Scotland’s
Landscape
, one program, part 5, focused on historic climate.

I produced the following chart from 3 separate charts shown on the
program, the original charts are shown lower down.

Temperature Scotland 4000BC to 1400AD

It is clear

  1. current temperatures
    are not unusual
  2. there have been a
    number of changes in temperature over the millenia

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From Physorg, news of a new paper  which may shed light on the rapid warming at the end of the last ice age. The young scientists don’t mention Milankovitch cycles in this presser, but these are slow to change in comparison to the rapid deglaciation, so maybe their theory lends something to the story. It does lead me to wonder if the precession cycle might be involved with bringing the oceanic oscillations into synch though.

From SoundonSound.com: Here you can see the original waveforms of the two different kick-drum samples. It's clear that they are drifting in and out of phase with each other. The resulting phase cancellation made it impossible to arrive at a consistent sound, so Mike had to edit them back into phase before processing.

From SoundonSound.com:
Here you can see the original waveforms of the two different kick-drum samples. It’s clear that they are drifting in and out of phase with each other. The resulting phase cancellation made it impossible to arrive at a consistent sound, so Mike had to edit them back into phase before processing.

Synchronization of North Atlantic, North Pacific preceded abrupt warming, end of ice age

A newly published study by researchers at Oregon State University probed the geologic past to understand mechanisms of abrupt climate change. The study pinpoints the emergence of synchronized climate variability in the North Pacific Ocean and the North Atlantic Ocean a few hundred years before the rapid warming that took place at the end of the last ice age about 15,000 years ago.

The study suggests that the combined warming of the two oceans may have provided the tipping point for abrupt warming and rapid melting of the northern ice sheets.

“If we really do cross such a boundary in the future, we should probably take a long-term perspective and realize that change will become the new normal. It may be a wild ride.”

Results of the study, which was funded by the National Science Foundation, appear this week in Science.

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Pierre L. Gosselin provides an English overview of a video presentation in German given by Dr. Sebastian Lüning, a geologist and co-author of the book “The Neglected Sun

This is a geological context that unfortunately is lost on many people like physicists who believe their formulae more than they believe the true facts.

Pierre mentions “All graphics cropped from Lüning’s presentation with permission.” so I won’t copy them here.

http://notrickszone.com/2014/06/29/german-geologist-ipcc-models-a-failure-have-no-chance-of-success-sees-possible-0-2c-of-cooling-by-2020

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I’m of the opinion that before getting into the complexity of numerical modelling, it’s wise to put considerable effort into trying to understand the physical processes at work in the climate system, and the origins of the energy flows that drive them. David Evans’ recent series of posts over at Jo Nova’s site have generated a lot of interesting discussion (despite being roundly ignored by Anthony Watts at WUWT), and I think we can shed some light on the ‘mysterious 11yr lag’ between solar input and climate response.

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Once again Pierre L. Gosselin brings fascinating content from the German speaking world

Distinct solar imprint on climate What’s more worrisome,

Schlüchter’s findings show that cold periods can strike very rapidly. Near the edge of Mont Miné Glacier his team found huge tree trunks and discovered that they all had died in just a single year. The scientists were stunned.

“The year of death could be determined to be exactly 8195 years before present. The oxygen isotopes in the Greenland ice show there was a marked cooling around 8200.”

That finding, Schlüchter states, confirmed that the sun is the main driver in climate change.

Article “Giant Of Geology/Glaciology Christian Schlüchter Refutes CO2…Feature Interview Throws Climate Science Into Disarray”

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