Archives de catégorie : climate and geology

AR6 and The Paleocene-Eocene Thermal Maximum

by Andy May, Aug 18, 2021 in WUWT


The PETM or Paleocene-Eocene Thermal Maximum was a warm period that began between 56.3 and 55.9 Ma (million years ago). The IPCC AR6 report (actually a draft, not a final edited report), released to the public on August 9, 2021, suggests that this warm period is similar to what is happening today and they expect to happen in the future (IPCC, 2021, pp. 2-82 & 5-14). During the PETM, it was very warm and average global surface temperatures probably peaked between 25.5°C and 26°C briefly, compared to a global surface temperature average of about 14.5°C today, as shown in Figure 1.

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oday we have tens of thousands of daily temperature measurements around the world and can calculate a fairly accurate global average surface temperature. To construct a global average for the PETM we must rely on proxy temperatures, such as oxygen isotope ratios, Calcium/Magnesium ratios in fossil shells, and fossil membrane lipids that are sensitive to temperature like Tex86. Proxy temperature values are sparsely located and have a temporal resolution, 56 Ma, of thousands to hundreds of thousands of years. Thus, in terms of rate of temperature change, they are not comparable to today’s monthly global averages.

Before diving into the PETM, we will provide some geological perspective. According to Christopher Scotese, the highest global average temperature in the Phanerozoic (the age of complex shelled organisms, or the past 550 million years) was the Triassic hothouse event, following the end of the Karoo Ice Age, around 250-300 Ma. Global average surface temperatures peaked then at about 27.9°C.

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NYIRAGONGO VOLCANO ERUPTS TO 45,000 FEET: DR CONGO ORDERS CITYWIDE EVACUATIONSp Allon,

by Cap Allon, May 23, 2021 in Electroverse


Nyiragongo’s deadliest eruption in history was that of 1977 (during the weak solar minimum of cycle 20) — this event went down as a VEI 1, according to historical observations, yet still managed to kill more than 600 people.

Saturday evening’s eruption looks bigger.

This was likely the volcano’s strongest eruption in recorded history.

UPTICK

Seismic and Volcanic activity has been correlated to changes in the Sun.

The recent global uptick in earthquakes and volcanic eruptions is likely attributed to the drop-off in solar activity, coronal holes, a waning magnetosphere, and the increase in Galactic Cosmic Rays penetrating silica-rich magma.

The COLD TIMES are returning, the mid-latitudes are REFREEZING, in line with a volcanic uptickthe great conjunction, historically low solar activitycloud-nucleating Cosmic Rays, and a meridional jet stream flow (among other forcings).

Both NOAA and NASA appear to agree, if you read between the lines, with NOAA saying we’re entering a ‘full-blown’ Grand Solar Minimum in the late-2020s, and NASA seeing this upcoming solar cycle (25) as “the weakest of the past 200 years”, with the agency correlating previous solar shutdowns to prolonged periods of global cooling here.

Furthermore, we can’t ignore the slew of new scientific papers stating the immense impact The Beaufort Gyre could have on the Gulf Stream, and therefore the climate overall.

Long Term Changes on the Grindelwald Glacier

by P. Homewood, March 28, 2021 in IowaClimSciEducation


The Upper & Lower Grindelwald Glaciers in 1774 by Caspar Wolf

https://en.wikipedia.org/wiki/Caspar_Wolf

HH Lamb’s Climate, History and The Modern World tells us much about the history of Alpine glaciers. For instance, how they advanced rapidly between 800 and 400 BC. They then retreated before advancing again between AD 600 and AD 850, when they may have even reached Little Ice Age maximum extents.

We are probably all familiar with the terrifying glacier advances, which began in the 17thC, following centuries of a much warmer climate. These were catastrophic for anybody living nearby, as farming land was wiped out, and even the land that escaped being overrun was far too cold to farm. As a result, famine was rife in Switzerland and elsewhere, even in cities which relied on the countryside for food.

People living in those days would have been dumfounded to hear that there are some now who are worried that glaciers are getting smaller.

 

A paper by Zumbuhl et al, published in 2006, offers a detailed history of the Lower Grindelwald glacier, as well as the Mer de Glace in the Mont Blanc region:

Claim: Melting glaciers contribute to Alaska earthquakes

by UNIVERSITY OF ALASKA FAIRBANKS, March 15, 2021 in WUWT


In 1958, a magnitude 7.8 earthquake triggered a rockslide into Southeast Alaska’s Lituya Bay, creating a tsunami that ran 1,700 feet up a mountainside before racing out to sea.

Researchers now think the region’s widespread loss of glacier ice helped set the stage for the quake.

In a recently published research article, scientists with the University of Alaska Fairbanks Geophysical Institute found that ice loss near Glacier Bay National Park has influenced the timing and location of earthquakes with a magnitude of 5.0 or greater in the area during the past century.

Scientists have known for decades that melting glaciers have caused earthquakes in otherwise tectonically stable regions, such as Canada’s interior and Scandinavia. In Alaska, this pattern has been harder to detect, as earthquakes are common in the southern part of the state.

Alaska has some of the world’s largest glaciers, which can be thousands of feet thick and cover hundreds of square miles. The ice’s weight causes the land beneath it to sink, and, when a glacier melts, the ground springs back like a sponge.

“There are two components to the uplift,” said Chris Rollins, the study’s lead author who conducted the research while at the Geophysical Institute. “There’s what’s called the ‘elastic effect,’ which is when the earth instantly springs back up after an ice mass is removed. Then there’s the prolonged effect from the mantle flowing back upwards under the vacated space.”

In the study, researchers link the expanding movement of the mantle with large earthquakes across Southeast Alaska, where glaciers have been melting for over 200 years. More than 1,200 cubic miles of ice have been lost.

Southern Alaska sits at the boundary between the continental North American plate and the Pacific Plate. They grind past each other at about two inches per year — roughly twice the rate of the San Andreas fault in California — resulting in frequent earthquakes.

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Is Climate Change Real?

by Robert Lyman,  March 23, 2021 in FriendsofScienceCalgary


Contributed by Robert Lyman © 2021 Full bio here.

Is climate change real? Journalists in Canada have had a field day with that question since it was debated at the Conservative Party policy meeting on March 20, 2021. It is the perfect question to ask if you want to boil a mind-numbingly complex set of issues into a simple question that can be used to misinform and confuse people. The proper answer to that question is another one. To what part of the climate policy conundrum are you referring?

You see, the “realness” (or truthfulness, or even importance) of climate policy depends on the answer to several questions, not one. Let’s break them down, and comment ever so briefly on the possible answers.

Is global warming occurring?

The global climate has been changing for millions of years, with temperatures rising and falling. They were as high as they are today during Roman times and the Medieval Warm Period. Since 1850, global average temperatures have risen slightly more than one degree Celsius.

MAGMATIC MOVEMENTS REGISTERED UNDER FAGRADALSFJALL VOLCANO, ICELAND — 34,000 QUAKES IN TWO WEEKS, ERUPTION LIKELY

by Cap Allon, March 11, 2021 in Electroverse


A “seismic crisis” has been occurring in the area near Fagradalsfjall since late Feb 2021. This activity has been interpreted as intrusion of magma at shallow depths, which could lead to a new eruption.

Fadradalsfjall is a Pleistocene table mountain in the Reykjanes Peninsula, NE of Grindavik, Iceland.

Of today’s reawakening volcanoes, those located in Iceland are perhaps the most concerning.

It is this highly-volcanic region that will likely be home to the next “big one” (a repeat of the 536 AD eruption that took out the Roman Republic…?) — the one that will return Earth to another volcanic winter.

Volcanic eruptions are one of the key forcings driving Earth into its next bout of global cooling.

Volcanic ash (particulates) fired above 10km –and so into the stratosphere– shade sunlight and reduce terrestrial temperatures. The smaller particulates from an eruption can linger in the upper atmosphere for years, or even decades+ at a time.

Today’s worldwide volcanic uptick is thought to be tied to low solar activity, coronal holes, a waning magnetosphere, and the influx of Cosmic Rays penetrating silica-rich magma.

The COLD TIMES are returning, the mid-latitudes are REFREEZING in line with the great conjunction, historically low solar activitycloud-nucleating Cosmic Rays, and a meridional jet stream flow (among other forcings).

Both NOAA and NASA appear to agree, if you read between the lines, with NOAA saying we’re entering a ‘full-blown’ Grand Solar Minimum in the late-2020s, and NASA seeing this upcoming solar cycle (25) as “the weakest of the past 200 years”, with the agency correlating previous solar shutdowns to prolonged periods of global cooling here.

Furthermore, we can’t ignore the slew of new scientific papers stating the immense impact The Beaufort Gyre could have on the Gulf Stream, and therefore the climate overall.

Molecular and isotopic evidence reveals the end-Triassic carbon isotope excursion is not from massive exogenous light carbon

by C.P. Fox et al., Dec 1, 2020 in PNAS


Significance

The end-Triassic mass extinction that occurred ∼202 Ma is one of the “Big Five” biotic crises of the Phanerozoic Eon. It is also accompanied by an organic carbon isotopic excursion that has long been interpreted as the result of a global-scale carbon-cycle disruption. Rather than being due to massive inputs of exogenous light carbon into the ocean–atmosphere system, the isotopic excursion is shown here to reflect regional sea-level change that caused a transition from a marine ecosystem to a less saline, shallow-water, microbial-mat environment and resultant changes in the sources of organic matter. The mass extinction that occurred slightly later, caused by abrupt injection of volcanogenic CO2, is accompanied by only modest changes in organic carbon isotopic composition.

Abstract

The negative organic carbon isotope excursion (CIE) associated with the end-Triassic mass extinction (ETE) is conventionally interpreted as the result of a massive flux of isotopically light carbon from exogenous sources into the atmosphere (e.g., thermogenic methane and/or methane clathrate dissociation linked to the Central Atlantic Magmatic Province [CAMP]). Instead, we demonstrate that at its type locality in the Bristol Channel Basin (UK), the CIE was caused by a marine to nonmarine transition resulting from an abrupt relative sea level drop. Our biomarker and compound-specific carbon isotopic data show that the emergence of microbial mats, influenced by an influx of fresh to brackish water, provided isotopically light carbon to both organic and inorganic carbon pools in centimeter-scale water depths, leading to the negative CIE. Thus, the iconic CIE and the disappearance of marine biota at the type locality are the result of local environmental change and do not mark either the global extinction event or input of exogenous light carbon into the atmosphere. Instead, the main extinction phase occurs slightly later in marine strata, where it is coeval with terrestrial extinctions and ocean acidification driven by CAMP-induced increases in PCO2; these effects should not be conflated with the CIE. An abrupt sea-level fall observed in the Central European basins reflects the tectonic consequences of the initial CAMP emplacement, with broad implications for all extinction events related to large igneous provinces.

Antarctica’s Larsen Ice Shelf Break-Up Driven by Geological Heat Flow Not Climate Change

by J.E. Kamis, Jan 19, 2017 in PlateClimatology


 

Figure 1  North tip of Antarctic Continent including Larsen Ice Shelf Outline (black line), very active
West Antarctica Rift / Fault System (red lines), and currently erupting or semi-active volcanoes (red dots).

Progressive bottom melting and break-up of West Antarctica’s seafloor hugging Larsen Ice Shelf is fueled by heat and heated fluid flow from numerous very active geological features, and not climate change.

This ice shelf break-up process has been the focus of an absolute worldwide media frenzy contending man-made atmospheric global warming is at work in the northwest peninsula of Antarctica. As evidence, media articles typically include tightly edited close-up photos of cracks forming on the surface of the Larsen Ice Shelf (Figure 2) accompanied by text laced with global warming alarmist catch phrases. This “advertising / marketing” approach does in fact produce beautiful looking and expertly written articles. However, they lack subsidence, specifically a distinct absence of actual scientific data and observations supporting the purported strong connection to manmade atmospheric global warming.

Working level scientists familiar with, or actually performing research on, the Larsen Ice Shelf utilize an entirely different approach when speaking about or writing about what is fueling this glacial ice break-up. They ascribe the break-up to poorly understood undefined natural forces (see quote below). Unfortunately, comments by these scientists are often buried deep in media articles and never seem to match the alarmist tone of the article’s headline.

“Scientists have been monitoring the rift on the ice shelf for decades. Researchers told NBC News that the calving event was “part of the natural evolution of the ice shelf,” but added there could be a link to changing climate, though they had no direct evidence of it.” (see here)

Hematite reconstruction of Late Triassic hydroclimate over the Colorado Plateau

by Lepre, J & Olsen P.E., Feb 21, 2021 PNAS


Significance

Hematite provides much of the color for the classic Triassic–Jurassic “red beds” of North America and elsewhere. Measuring the spectrum of visible light reflected and absorbed by the red beds, we demonstrate that the hematite concentrations faithfully track 14.5 million years of Late Triassic monsoonal rainfall over the Colorado Plateau of Arizona and use this information to assess interrelationships between environmental perturbations, climate, and the evolution of terrestrial vertebrates. The research challenges conventional ideas that the hematite has limited use for interpreting the ancient past because it is a product of natural chemical alterations that occurred long after the beds were initially deposited.

Abstract

Hematite is the most abundant surficial iron oxide on Earth resulting from near-surface processes that make it important for addressing numerous geologic problems. While red beds have proved to be excellent paleomagnetic recorders, the early diagenetic origin of hematite in these units is often questioned. Here, we validate pigmentary hematite (“pigmentite”) as a proxy indicator for the Late Triassic environment and its penecontemporaneous origin by analyzing spectrophotometric measurements of a 14.5-My–long red bed sequence in scientific drill core CPCP-PFNP13-1A of the Chinle Formation, Arizona. Pigmentite concentrations in the red beds track the evolving pattern of the Late Triassic monsoon and indicate a long-term rise in aridity beginning at ∼215 Ma followed by increased oscillatory climate change at ∼213 Ma. These monsoonal changes are attributed to the northward drift of the Colorado Plateau as part of Laurentia into the arid subtropics during a time of fluctuating CO2. Our results refine the record of the Late Triassic monsoon and indicate significant changes in rainfall proximal to the Adamanian–Revueltian biotic transition that thus may have contributed to apparent faunal and floral events at 216 to 213 Ma.

Scientists Discover Plate Tectonics… Again

by D. Middleton, Feb 5, 2021 in WUWT


An upwelling of rock beneath the Atlantic may drive continents apart
The Mid-Atlantic Ridge may play a more active role in plate tectonics than thought

By Maria Temming

FEBRUARY 4, 2021

An upsurge of hot rock from deep beneath the Atlantic Ocean may be driving the continents on either side apart.

The Americas are moving away from Europe and Africa by a few centimeters each year, as the tectonic plates underlying those continents drift apart. Researchers typically think tectonic plates separate as the distant edges of those plates sink down into Earth’s mantle, creating a gap (SN: 1/13/21). Material from the upper mantle then seeps up through the rift between the plates to fill in the seafloor.

But new seismic data from the Atlantic Ocean floor show that hot rock is welling up beneath a seafloor rift called the Mid-Atlantic Ridge from hundreds of kilometers deep in Earth’s mantle. This suggests that material rising up under the ridge is not just a passive response to tectonic plates sliding apart. Rather, deep rock pushing toward Earth’s surface may be driving a wedge between the plates that helps separate them, researchers report online January 27 in Nature.

A better understanding of plate tectonics — which causes earthquakes and volcanic eruptions — could help people better prepare for these natural disasters (SN: 9/3/17).

Newly Discovered Greenland Plume Drives Thermal Activities in the Arctic

by C. Rotter, Dec 29, 2020  in WUWT


A team of researchers understands more about the melting of the Greenland ice sheet. They discovered a flow of hot rocks, known as a mantle plume, rising from the core-mantle boundary beneath central Greenland that melts the ice from below.

The results of their two-part study were published in the Journal of Geophysical Research.

“Knowledge about the Greenland plume will bolster our understanding of volcanic activities in these regions and the problematic issue of global sea-level rising caused by the melting of the Greenland ice sheet,” said Dr. Genti Toyokuni, co-author of the studies.

The North Atlantic region is awash with geothermal activity. Iceland and Jan Mayen contain active volcanoes with their own distinct mantle plumes, whilst Svalbard – a Norwegian archipelago in the Arctic Ocean – is a geothermal area. However, the origin of these activities and their interconnectedness has largely been unexplored.

The research team discovered that the Greenland plume rose from the core-mantle boundary to the mantle transition zone beneath Greenland. The plume also has two branches in the lower mantle that feed into other plumes in the region

 

Newly discovered Greenland plume drives thermal activities in the Arctic

by Tohoku University, Dec 7, 2020 in ScienceDaily


A team of researchers understands more about the melting of the Greenland ice sheet. They discovered a flow of hot rocks, known as a mantle plume, rising from the core-mantle boundary beneath central Greenland that melts the ice from below.

The results of their two-part study were published in the Journal of Geophysical Research.

“Knowledge about the Greenland plume will bolster our understanding of volcanic activities in these regions and the problematic issue of global sea-level rising caused by the melting of the Greenland ice sheet,” said Dr. Genti Toyokuni, co-author of the studies.

The North Atlantic region is awash with geothermal activity. Iceland and Jan Mayen contain active volcanoes with their own distinct mantle plumes, whilst Svalbard — a Norwegian archipelago in the Arctic Ocean — is a geothermal area. However, the origin of these activities and their interconnectedness has largely been unexplored

 

Claim: The climate changed rapidly alongside sea ice decline in the north

by University of Copenhagen, Dec 6, 2020 in WUWT


Researchers from the Niels Bohr Institute, University of Copenhagen have, in collaboration with Norwegian researchers in the ERC Synergy project, ICE2ICE, shown that abrupt climate change occurred as a result of widespread decrease of sea ice. This scientific breakthrough concludes a long-lasting debate on the mechanisms causing abrupt climate change during the glacial period. It also documents that the cause of the swiftness and extent of sudden climate change must be found in the oceans.

Scientific evidence for abrupt climate change in the past finally achieved

During the last glacial period, app. 10,000 – 110,000 years ago the northern hemisphere was covered in glacial ice and extensive sea ice, covering the Nordic seas. The cold glacial climate was interrupted by periods of fast warmup of up to 16.5 degrees Celsius over the Greenland ice sheet, the so called Dansgaard Oeschger events (D-O).

These rapid glacial climate fluctuations were discovered in the Greenland ice core drillings decades ago, but the cause of them have been hotly contested. D-O events are of particular significance today as the rate of warming seems to be very much like what can be observed in large parts of the Arctic nowadays. The new results show that the abrupt climate change in the past was closely linked to the quick and extensive decline in sea ice cover in the Nordic seas. Very important knowledge as sea ice is presently decreasing each year.

“Our, up until now, most extensive and detailed reconstruction of sea ice documents the importance of the rapid decrease of sea ice cover and the connected feedback mechanisms causing abrupt climate change”, says Henrik Sadatzki, first author of the study.

Sediment core and ice core data were combined in order to achieve the result

In Geological Terms, Today’s Atmospheric CO2 Concentrations Are Still Uncomfortably Low

by P. Gosselin, Dec 5, 2020 in NoTricksZone


Under 180 ppm atmospheric CO2 concentration, life on earth begins to die.

The earth came very close to that point not long ago during the Ice Ages (20,000 years ago). Then the planet warmed naturally, and an increase in atmospheric CO2 to over 200 ppm followed (new study here).

The earth saw CO2 levels of close to 8000 ppm in the past, i.e. about 20 times more than today. The following chart shows the earth’s atmospheric CO2 concentrations for the past 600 million years.

Today, thanks in large part to mankind, concentrations have risen to over 400 ppm, yet historically this remains at the very low end of the scale compared to the thousands of ppm seen naturally earlier in history.

Greening planet

Today, definitely a safer level would be near 1000 ppm. Studies unanimously show plant growth at these higher levels is far enhanced. Already today we see clear evidence the planet is greening Zhu et al. (2016), in part due to the fertilizations taking place through human emissions:

New Paleoclimatology Finding Shows Earth’s Climate Was Typically Warmer than Today

by H.S. Sterling, Dec2, 2020 in WUWT


Archaeologists have published a new paper in The HoloceneDOI: 10.1177/0959683620972775 that confirms what previous research has shown: numerous periods during recent history have been as warm as or warmer than the present.

The press release was covered in The New Scientist, “Climate change has revealed a huge haul of ancient arrows in Norway,”  and discusses the findings of researchers from the Universities of Cambridge, Oslo, and Bergen. The researchers discovered a “treasure trove” of arrows, arrowheads, clothing, and other artifacts, recently uncovered by a receding ice in a mountainous region of southern Norway. The oldest arrows and artifacts date from around 4100 BC. The youngest artifacts date from approximately AD 1300, at the end of the Medieval Warm Period. Because present temperatures are only now exposing some of the artifacts were deposited when no ice covered the ground, temperatures were clearly warmer during the many periods when artifacts were deposited.

Along with the arrows and other artifacts, the researchers found nearly 300 specimens of reindeer antler and bone exposed by receding ice. Because reindeer presently frequent the area, the archaeologists say they are confident the area has served as an important hunting ground, off and on, for millennia.

The fact that artifacts were found from several different periods separated by hundreds and thousands of years in time indicates the ice and snow in the region has expanded and receded several times over the current interglacial period.

Elsewhere in Norway, scientists also recently uncovered what they have labeled a “Viking highway,” a route the ancient peoples inhabiting the region used to travel regularly. The route had for approximately 2,000 years been covered by snow and ice that expanded as the region’s climate shifted from a relatively warm period, comparable to present temperatures, to a colder period during which “permanent” thick snow and ice cover formed. This erected the equivalent of a “highway closed” sign.

Editorial: Deep Carbon Science

by D. Cardace et al., Nov 12, 2020 in Front.Earth.Sci.


Editorial on the Research Topic
Deep Carbon Science

Our understanding of the slow, deep carbon cycle, key to Earth’s habitability is examined here. Because the carbon cycle links Earth’s reservoirs on nano- to mega-scales, we must integrate geological, physical, chemical, biological, and mathematical methods to understand objects and processes so small and yet so vast. Here, we profile current research in the physical chemistry of carbon in natural and model systems, processes ongoing in the deepest portions of planets, and observations of carbon utilization by the deep biosphere. The relationships between the carbon cycle and planetary habitability are undeniable, forming a conceptual anchor to all work in deep carbon science.

Carbon minerals respond to changing pressures, temperatures, and geochemical conditions. The geologic record preserves evidence of transitional periods at the submicroscopic to regional landscape scales, and demonstrates interplay between carbon-bearing phases and the biosphere. In a new review, Morrison et al. (2020) cast a retrospective look through deep time and call for emerging approaches to clarify the coevolution of the biosphere and geosphere.

Critical to transformations of Earth’s carbon inventory over time are indomitable tectonics – which influence Earth’s surface environment, weathering, metamorphism, magmatism, and volcanism. The slow, deep (endogenous) carbon cycle refines and re-distributes carbon within Earth. In fact, over the 200-million-year-long time scale, important tectonic controls on carbon cycling emerge (Wong et al., 2019). Wong et al. (2019) document the spatiotemporal evolution of fluxes inferred from plate tectonic reconstructions, and highlight CO2 fluxes from continental rift settings post-Pangea. The volcanic flux of CO2 has been successfully reconstructed by direct study of CO2 flux through lakes and adjacent soils (Hughes et al., 2019), an important and often overlooked CO2 valve linking lithosphere, atmosphere, and hydrosphere. From perspectives rooted deeper in the tectonic system, the important roles that serpentinites play in the carbon cycle are evaluated in two senses: 1) serpentinite as a carbon vector to the deep mantle (Merdith et al., 2019), and 2) serpentine mud volcanoes as sites of carbon mobilization through organic acid release (Eickenbusch et al., 2019), in a Mariana Trench case study.

Continuer la lecture de Editorial: Deep Carbon Science

How ancient dust from the sea floor helps to explain climate history

by UNIVERSITY OF OLDENBURG, Nov 11, 2020 in WUWT


During the last Ice Age about 20,000 years ago, iron-containing dust acted as a fertilizer for marine phytoplankton in the South Pacific, promoting CO2 sequestration and thus the glacial cooling of the Earth. But where did the dust come from? Researchers led by Dr. Torben Struve, geoscientist at the University of Oldenburg, Germany, have investigated this open question of climate history, which is also relevant with respect to current climate change.

Using sediment cores from the sea floor, they found that a large part of the dust deposited in the southern South Pacific at that time had travelled an extremely long way. Up to 80 percent of the dust came from what is now north-west Argentina, from where it was transported almost completely around the globe by the prevailing westerly winds. After a voyage of up to 20,000 kilometres, it contributed significantly to the increased input of iron into the glacial South Pacific. The dust input from Australia, which dominates in the South Pacific today, played only a minor role. The research team has published these new insights into the mechanisms of natural iron input into the Southern Ocean in the journal Nature Communications.

“We have analysed the chemical fingerprint of the dust and compared it with geological data from several continents. This was laborious work, like a jigsaw puzzle,” says Struve, a post-doctoral scientist in the research group “Marine Isotope Geochemistry” at the University’s Institute for Chemistry and Biology of the Marine Environment (ICBM). The team included researchers from his group as well as colleagues from the Alfred Wegener Institute – Helmholtz Centre for Polar and Marine Research, Bremerhaven (Germany), and from Columbia University, New York (USA).

The cement for coral reefs

by University of Erlangen-Nuremberg  Nov 2020, in ScienceDaily


Coral reefs are hotspots of biodiversity. As they can withstand heavy storms, they offer many species a safe home, and at the same time, they protect densely populated coastal regions as they level out storm-driven waves. However, how can these reefs that are made up of often very fragile coral be so stable? A team of researchers from Friedrich-Alexander Universität Erlangen-Nürnberg (FAU) and the University of Bayreuth have now discovered that a very specific type of ‘cement’ is responsible for this — by forming a hard calcareous skeleton, coralline red algae stabilise the reefs, and have been doing so for at least 150 million years.

The wide variety of life they support is immediately apparent on images of tropical coral reefs. Their three-dimensional scaffolding provides a habitat for a large number of species. However, the skeletons of the coral are often so fragile that they would not be able to withstand heavy storms by themselves. Even if scientists have long suspected that coralline red algae provide support to reefs with their calcareous skeletons, this is the first time that this link has been proven.

Coralline red algae have been supporting coral reefs for at least 150 million years

The researchers from FAU and the University of Bayreuth were able to prove this supporting function by analysing more than 700 fossilised reefs from 150 million years of the Earth’s history. ‘The coralline red algae form a calcareous skeleton and cement the coral reefs together,’ explains Dr. Sebastian Teichert from the Chair of Palaeoenvironmental Research at FAU. ‘However, several crises over the course of millions of years have limited their capacity to do so.’

Successful adaptive strategies against plant grazers

 


 

3 More New Studies Show Modern Arctic Sea Ice Extent Is Greater Than Nearly Any Time In The Last 10,000 Years

by K. Richard, Oct 29, 2029 in NoTricksZone


For years scientists have been using biomarker evidence (IP25, PIP25) to reconstruct the Arctic’s sea ice history. The evidence shows modern (20th-21st century) Arctic sea ice is at its greatest extent since the Holocene began.

Scientists (Wu et al., 2020) have determined that from about 14,000 to 8,000 years ago, when CO2 lingered near 250 ppm, the Beaufort Sea (Arctic) was “nearly ice free throughout the year” (<0.2 PIP25) and ~4°C warmer than today in winter.

With CO2 at ~400 ppm, this region is 70-100% ice-covered (>0.8 PIP25) for all but 1-2 summer months in the modern (1988-2007) era.

….

“Where’s the sea ice?” Right where it’s been for most of the Holocene.

by D. Middleton, Oct 30, 2020 in WUWT


This is sort of a sequel yesterday’s post: Where’s the sea ice? 3 reasons the Arctic freeze is unseasonably late and why it matters.

What a difference a day can make! Looks like it’s starting to crust over:

Figure 0. Daily sea ice extent map, October 29, 2020. (NSIDC)

Two key takeaways:

  1. Maximum Holocene sea ice extent occurred within the past 500-1,000 years at every location.
  2. The current sea ice extent is higher at all of the locations than over 50% to 85% of the Holocene.

While this doesn’t tell us what the sea ice extent was in million km2, it does tell us that the modern sea ice extent is larger than it was over most of the Holocene Epoch. It also tells us that the areas of currently seasonal sea ice extent have been seasonal or reduced over most of the past 5,000 years and ice-free or nearly ice-free over the prior 3,000 years or so. Here’s is the Kinnard graph plotted at the same horizontal scale as the Stein cross section:

Permian–Triassic mass extinction pulses driven by major marine carbon cycle perturbations

by Jurikova, H. et al., Oct 19, 2020 in NatureGeoscience


Abstract

The Permian/Triassic boundary approximately 251.9 million years ago marked the most severe environmental crisis identified in the geological record, which dictated the onwards course for the evolution of life. Magmatism from Siberian Traps is thought to have played an important role, but the causational trigger and its feedbacks are yet to be fully understood. Here we present a new boron-isotope-derived seawater pH record from fossil brachiopod shells deposited on the Tethys shelf that demonstrates a substantial decline in seawater pH coeval with the onset of the mass extinction in the latest Permian. Combined with carbon isotope data, our results are integrated in a geochemical model that resolves the carbon cycle dynamics as well as the ocean redox conditions and nitrogen isotope turnover. We find that the initial ocean acidification was intimately linked to a large pulse of carbon degassing from the Siberian sill intrusions. We unravel the consequences of the greenhouse effect on the marine environment, and show how elevated sea surface temperatures, export production and nutrient input driven by increased rates of chemical weathering gave rise to widespread deoxygenation and sporadic sulfide poisoning of the oceans in the earliest Triassic. Our findings enable us to assemble a consistent biogeochemical reconstruction of the mechanisms that resulted in the largest Phanerozoic mass extinction.

A Geological Perspective of Polar Bears

by D. Middelton, Oct 11, 2020 in WUWT


Estimates have ranged from 70,000 to 5,000,000 years ago. The oldest confirmed polar bear fossil dates to 110,000 to 130,000 years ago… Meaning that polar bears survived the Eemian interglacial stage.

The peak warmth of the Eemian interglacial stage marks the boundary between the Late Pleistocene Tarantian Age and the Middle Pleistocene Ionian Age.

A New Mass Extinction Event Has Been Discovered, And It Triggered The Rise of Dinosaurs

by M. Benton, Sep 25, 2020 in ScienceAlert


Huge volcanic eruptions 233 million years ago pumped carbon dioxide, methane, and water vapour into the atmosphere. This series of violent explosions, on what we now know as the west coast of Canada, led to massive global warming.

Our new research has revealed that this was a planet-changing mass extinction event that killed off many of the dominant tetrapods and heralded the dawn of the dinosaurs.

The best known mass extinction happened at the end of the Cretaceous period, 66 million years ago. This is when dinosaurs, pterosaurs, marine reptiles and ammonites all died out.

This event was caused primarily by the impact of a giant asteroid that blacked out the light of the sun and caused darkness and freezing, followed by other massive perturbations of the oceans and atmosphere.

Geologists and palaeontologists agree on a roster of five such events, of which the end-Cretaceous mass extinction was the last. So our new discovery of a previously unknown mass extinction might seem unexpected.

And yet this event, termed the Carnian Pluvial Episode (CPE), seems to have killed as many species as the giant asteroid did. Ecosystems on land and sea were profoundly changed, as the planet got warmer and drier.

On land, this triggered profound changes in plants and herbivores. In turn, with the decline of the dominant plant-eating tetrapods, such as rhynchosaurs and dicynodonts, the dinosaurs were given their chance.

Scientists Find Peak 1940s Warmth, Post-1950s Cooling In The Same Western US Region Where Hockey Sticks Emerged

by K. Richard, Sep 24, 2020 in NoTricksZone


A new 1735-2015 temperature reconstruction (Heeter et al., 2020) using Western US tree ring proxies shows peak 1940s warmth and post-1950s cooling. This is the same region Dr. Michael Mann used tree ring data to construct his famous hockey stick graph.

A new Scandinavian temperature reconstruction (Seftigen et al., 2020) that’s “skillfull in characterizing past temperature changes over the past one to two millennia” finds there