Archives de catégorie : climate and geology

Scientists Say A 6°C Warmer-Than-Today Arctic Is ‘Optimal’ For Thermophile Species

by K. Richard, Apr 6, 2023 in NoTricksZone


Back in the Early Holocene, when CO2 levels were said to be ~255 ppm, Arctic Svalbard was warm enough to accommodate abundant numbers of thermophiles, or warmth-demanding species. Only “remnants” of these species and their habitat exist in today’s much-colder Arctic.

With the exception of a few centuries in recent millennia, today’s Svalbard (Arctic) is the most glaciated it has been in the last 10,000 years (see the blue trend line in the below chart from Brožová et al., 2023).

 

This region is today about 6°C colder than it was during the early Holocene (~10,000 to 8,000 years ago), a climatic period scientists characterize as an optimum, or “most favorable,” for a “rich species pool” of thermophiles.

The sea surface temperatures (SSTs) in the western Barents Sea were as warm as 13°C and “sea ice-free during most of the mid-Holocene” (Łącka et al., 2019). In contrast, today’s SST in this region are as cold as they were during the last glacial (2-4°C), when CO2 hovered near 200 ppm. Rapid double-digit SST fluctuations, varying from 3 to 13°C, have been ongoing throughout the Holocene.

New Study: Roman And Medieval Warm Periods Were 2.8°C Warmer Than 1970-2000 In Central China

by K. Richard, Mar 13, 2023 in NoTricksZone


A series of paleoclimate lake reconstructions across China in recent years have failed to support the global-scale warming narrative.

Per a new lake temperature reconstruction (Li et al., 2023) from Central China, there were distinct “warm intervals during the RWP [Roman Warm Period] (403–413 CE), with a temperature 2.89°C higher than that of the mean for 1970–2000 CE, and during the MWP [Medieval Warm Period] (864–882 and 965–994 CE), when the temperature was 2.81°C higher.”

There are 8 other lake sediment reconstructions from the region (Qinghai, Gahai, Sugan, Kusai, Tiancai, Heiahi, Lugu, Cuoqia) documented in the study. None of the 8 are shown to have a modern temperature uptick that would support the claims of an unusually warm modern climate relative to past millennia.

Elegantly modeling Earth’s abrupt glacial transitions

by American Institute of Physics, Mar 7, 2023 in ScienceDaily


Proxy data — indirect records of the Earth’s climate found in unlikely places like coral, pollen, trees, and sediments — show interesting oscillations approximately every 100,000 years starting about 1 million years ago. Strong changes in global ice volume, sea level, carbon dioxide concentration, and surface temperature indicate cycles of a long, slow transition to a glacial period and an abrupt switch to a warm and short interglacial period.

Milutin Milankovitch hypothesized that the timing of these cycles was controlled by the orbital parameters of the Earth, including the shape of its path around the sun and the tilt of the planet. A slightly closer orbit or more tilted planet could create a small increase in solar radiation and a feedback loop that leads to massive changes in climate. This idea suggests that there may be some predictability in the climate, a notoriously complex system.

In Chaos, by AIP Publishing, Stefano Pierini of Parthenope University of Naples proposed a new paradigm to simplify the verification of the Milankovitch hypothesis.

“The main motivation behind this study was the wish to characterize and illustrate the Milankovitch hypothesis in a simple, elegant, and intuitive way,” Pierini said.

Many models suggest that Milankovitch is correct; however, such methods are often detailed and study specific. They incorporate climate feedback loops — for example, increased ice cover reflects more radiation back into space, leading to further cooling and more ice cover — as threshold crossing rules. This means that an abrupt jump in climate only occurs once a parameter reaches a given tipping point.

Pierini’s “deterministic excitation paradigm” combines the physics concepts of relaxation oscillation and excitability to link Earth’s orbital parameters and the glacial cycles in a more generic way. The relaxation oscillation component describes how the climate slowly returns to its original glacier state after it is disturbed. At that point, the excitability piece of the model captures the external orbital changes and triggers the next glacial cycle.

By using his own threshold crossing rules and adopting a classical energy-balance model, Pierini obtained correct and robust timing of the most recent glacial cycles.`

Early Cretaceous shift in the global carbon cycle affected both land and sea

by University of Nebraska-Lincoln, Feb 22, 2023 in ScienceDaily


Geologists doing fieldwork in southeastern Utah’s Cedar Mountain Formation found carbon isotope evidence that the site, though on land, experienced the same early Cretaceous carbon-cycle change recorded in marine sedimentary rocks in Europe. This ancient carbon-cycle phenomenon, known as the ‘Weissert Event’ was driven by large, sustained volcanic eruptions in the Southern Hemisphere that greatly increased carbon dioxide levels in the atmosphere and produced significant greenhouse climate effects over a prolonged time.

Scientific research in recent decades has confirmed that major changes in the global carbon cycle caused significant changes in the Earth’s atmosphere and oceans 135 million years ago, during the early Cretaceous Period. A range of questions remain about the details of climate change dynamics in that era. This new research, involving wide-ranging chemical and radioactivity-based analyses of rock strata in Utah’s Cedar Mountain Formation, helps fill in that knowledge gap by confirming that such carbon-cycle shifts were recorded on land in ancient North America.

The carbon cycle is one of Earth’s fundamental environmental phenomena, involving the ongoing transfer of carbon among the atmosphere, oceans and living organisms, as well as soils, sediments and rocks in the solid Earth. The cycle is crucial to biological processes for living things on land and sea. When large-scale changes in the cycle occur, they can produce major shifts in climate and the oceans’ biological conditions.

“We’re studying how the global carbon cycle has functioned in the past, how changes are recorded in the sedimentary rocks around the world,” said Joeckel, a professor in the School of Natural Resources at Nebraska. The environmental phenomena he and his colleagues analyzed “are exactly the kind of things we’re talking about today, as people increase the input of carbon dioxide into the atmosphere at a much-accelerated rate by burning fossil fuels.”

Joeckel, the Nebraska state geologist, headed the Utah fieldwork and organized the study, published as a peer-reviewed paper in a special February issue of the journal Geosciences.

Keeling Curve CO2 Measurements Halted By Mauna Loa Eruption

by BigIslandVideoNews, Nov 29, 2022


(BIVN) – The collection of data for use in the decades-long record of atmospheric carbon dioxide, known famously as the Keeling Curve, was cut off on Monday night, as lava from the latest Mauna Loa eruption flows down the mountain.

The lava crossed the Mauna Loa Weather Observatory Road at approximately 8 p.m. in the evening, cutting off power to observatory facilities and equipment.

Researchers at Scripps Institution of Oceanography at UC San Diego, which started collecting the Keeling Curve data at the site in 1958, say they “are exploring options regarding the relocation of measurement equipment.” From the Tuesday announcement:

 

..

 

See also Mauna Loa eruption cuts access, power to Mauna Loa Observatory

An Inconvenient Tree: Is Climate Change Driving Worse Floods

by E. Worrall, Nov 27, 2022 in WUWT


Does evidence of past extreme floods invalidate claims that climate change is making floods worse?

 

Could volcanic activity be a contributor to major floods in Australia? Australia is on the South Western edge of the Ring of Fire. While the Australian mainland is not very volcanically active, there have been some spectacular eruptions in our neighbourhood, such as the infamous Krakatoa eruption in 1883, or the 1815 Tambora Eruption, which is blamed for causing famine in the United States in 1816, “The Year Without a Summer”.

A notable volcanic eruption occurred at the start of 2022 – The Hunga Tonga eruption. JoNova published an intriguing comparison between the volcanic ash distribution from the Hunga Tonga eruption in January 2022, and 2022 rainfall anomalies across Australia. Hunga Tonga was light on sulphates, but the blast threw unprecedented amounts of water into the stratosphere. Where I live, on the Southern edge of the volcanic debris distribution, we’ve had some spectacular sunsets over the last year.

The apparent overlap between rainfall anomalies and volcanic debris could be a coincidence – but the comparison is visually intriguing.

Earth can regulate its own temperature over millennia, new study finds

by Massachusetts Institute of Technology, Nov16, 2022 in ScienceDaily


The Earth’s climate has undergone some big changes, from global volcanism to planet-cooling ice ages and dramatic shifts in solar radiation. And yet life, for the last 3.7 billion years, has kept on beating.

Now, a study by MIT researchers in Science Advances confirms that the planet harbors a “stabilizing feedback” mechanism that acts over hundreds of thousands of years to pull the climate back from the brink, keeping global temperatures within a steady, habitable range.

Just how does it accomplish this? A likely mechanism is “silicate weathering” — a geological process by which the slow and steady weathering of silicate rocks involves chemical reactions that ultimately draw carbon dioxide out of the atmosphere and into ocean sediments, trapping the gas in rocks.

Scientists have long suspected that silicate weathering plays a major role in regulating the Earth’s carbon cycle. The mechanism of silicate weathering could provide a geologically constant force in keeping carbon dioxide — and global temperatures — in check. But there’s never been direct evidence for the continual operation of such a feedback, until now.

The new findings are based on a study of paleoclimate data that record changes in average global temperatures over the last 66 million years. The MIT team applied a mathematical analysis to see whether the data revealed any patterns characteristic of stabilizing phenomena that reined in global temperatures on a geologic timescale.

Journal Reference:

  1. Constantin W. Arnscheidt, Daniel H. Rothman. Presence or absence of stabilizing Earth system feedbacks on different time scales. Science Advances, 2022; 8 (46) DOI: 10.1126/sciadv.adc9241

Nature Unbound I: The Glacial Cycle

by Javier, Oct 24, 2016 in ClimateEtc.


Insights into the debate on whether the Holocene will be long or short.

Summary: Milankovitch Theory on the effects of Earth’s orbital variations on insolation remains the most popular explanation for the glacial cycle since the early 1970’s. According to its defenders, the main determinant of a glacial period termination is high 65° N summer insolation, and a 100 kyr cycle in eccentricity induces a non-linear response that determines the pacing of interglacials. Based on this theory some authors propose that the current interglacial is going to be a very long one due to a favorable evolution of 65° N summer insolation. Available evidence, however, supports that the pacing of interglacials is determined by obliquity, that the 100 kyr spacing of interglacials is not real, and that the orbital configuration and thermal evolution of the Holocene does not significantly depart from the average interglacial of the past 800,000 years, so there is no orbital support for a long Holocene.

Another Study Says Europe Was At Times Warmer During The Last Glacial When CO2 Levels Were 40% Lower

by K. Richard, Oct 24, 2022 in NoTricksZone

The Earth was still in ice age conditions 14,700 to 12,900 years ago, or during the “Bolling interstadial.” CO2 hovered near 230 ppm at that time, and yet “continental Europe was a few degrees warmer than present” (Toth et al., 2022).

In recent years there have been multiple studies detailing a European climate that was as warm or warmer than today during the late Pleistocene ice age.

The latest study, Toth et al., 2022, uses chironomid proxy evidence to reconstruct summer temperatures at a lake site in the Eastern Carpathians.

These authors report that “continental Europe was a few degrees warmer than present during the Bolling interstadial,” and there were slightly (0.5°C) warmer-than-today periods (e.g., ~16,300 years ago) at the study site. The warming events were both pronounced (5°C) and abrupt.

Ultra-depleted hydrogen isotopes in hydrated glass record Late Cretaceous glaciation in Antarctica

by D.A. Nelson et al. , Sept 7, 2022 in NatureCommunications


Abstract

The Early Jurassic Butcher Ridge Igneous Complex (BRIC) in the Transantarctic Mountains contains abundant and variably hydrated silicic glass which has the potential to preserve a rich paleoclimate record. Here we present Fourier Transform Infrared Spectroscopic data that indicates BRIC glasses contain up to ~8 wt.% molecular water (H2Om), and low (<0.8 wt.%) hydroxyl (OH) component, interpreted as evidence for secondary hydration by meteoric water. BRIC glasses contain the most depleted hydrogen isotopes yet measured in terrestrial rocks, down to δD = −325 ‰. In situ 40Ar/39Ar geochronology of hydrated glasses with ultra-depleted δD values yield ages from 105 Ma to 72 Ma with a peak at c. 91.4 Ma. Combined, these data suggest hydration of BRIC glasses by polar glacial ice and melt water during the Late Cretaceous, contradicting paleoclimate reconstructions of this period that suggest Antarctica was ice-free and part of a global hot greenhouse.

Successive climate crises in the deep past drove the early evolution and radiation of reptiles

by T. Simoes et al., Aug 19, 2022 in ScienceAdvance


Abstract

Climate change–induced mass extinctions provide unique opportunities to explore the impacts of global environmental disturbances on organismal evolution. However, their influence on terrestrial ecosystems remains poorly understood. Here, we provide a new time tree for the early evolution of reptiles and their closest relatives to reconstruct how the Permian-Triassic climatic crises shaped their long-term evolutionary trajectory. By combining rates of phenotypic evolution, mode of selection, body size, and global temperature data, we reveal an intimate association between reptile evolutionary dynamics and climate change in the deep past. We show that the origin and phenotypic radiation of reptiles was not solely driven by ecological opportunity following the end-Permian extinction as previously thought but also the result of multiple adaptive responses to climatic shifts spanning 57 million years.

Iceland eruption may be the start of decades of volcanic activity

by G. Andrews, Aug 4, 2022 in NationalGeographic


Less than a year has passed since lava stopped sputtering from Iceland’s Reykjanes Peninsula following the first major volcanic outburst from this region in almost 800 years. But now the island is once again bleeding molten rock. The start of a new eruption so soon after unrest in 2021 seems to underscore that this once quiescent peninsula has awoken from its long slumber.

“This could herald the start of decades of occasional eruptions,” says Dave McGarvie, a volcanologist at Lancaster University.

The new eruption, which started at 1:18 p.m. local time on August 3, sent scarlet ribbons streaming from the base of a small mountain into the uninhabited Meradalir Valley. Located far from populations, the volcanic burbles likely pose little danger to the public, at least in the near term. And this relative safety allows scientists and tourists alike to marvel at the geologic majesty and get excited for a possible onslaught of new scientific knowledge.

After all, each volcanic eruption here provides a “window into the abyss,” McGarvie says. The 2021 event yielded revelations about the personality of the peninsula’s exuberant eruptions—from their physical behaviors to their quirky chemistries. This new eruption promises even more insights as the nascent volcano forges the world’s youngest land.

It’s still unclear how prolific or lengthy the eruption will be; this information will only come to light with more time and continued monitoring. But this week’s show of fireworks strongly hints the peninsula will become one of the most volcanically active parts of the planet for several generations.

“I am genuinely excited,” McGarvie says.

A volcanic double-bill

Tonga Eruption Blasted Unprecedented Amount of Water Into Stratosphere

by C. Rotter, Aug 3, 2022 in WUWT


….

This looping video shows an umbrella cloud generated by the underwater eruption of the Hunga Tonga-Hunga Ha’apai volcano on Jan. 15, 2022. The GOES-17 satellite captured the series of images that also show crescent-shaped shock waves and lightning strikes.
Credit: NASA Earth Observatory image by Joshua Stevens using GOES imagery courtesy of NOAA and NESDIS

The huge amount of water vapor hurled into the atmosphere, as detected by NASA’s Microwave Limb Sounder, could end up temporarily warming Earth’s surface.

When the Hunga Tonga-Hunga Ha’apai volcano erupted on Jan. 15, it sent a tsunami racing around the world and set off a sonic boom that circled the globe twice. The underwater eruption in the South Pacific Ocean also blasted an enormous plume of water vapor into Earth’s stratosphere – enough to fill more than 58,000 Olympic-size swimming pools. The sheer amount of water vapor could be enough to temporarily affect Earth’s global average temperature.

“We’ve never seen anything like it,” said Luis Millán, an atmospheric scientist at NASA’s Jet Propulsion Laboratory in Southern California. He led a new study examining the amount of water vapor that the Tonga volcano injected into the stratosphere, the layer of the atmosphere between about 8 and 33 miles (12 and 53 kilometers) above Earth’s surface.

A Tropical Plant’s Warmth Threshold Affirms Mid-Holocene Temps Were ‘7.7°C Higher Than Today’

by K. Richard, July 25, 2022 in NoTricksZone


A warmth-demanding plant can provide us with solid evidence of a much warmer than today Mid-Holocene climate.

Growth of the tropical aquatic plant ceases when air temperatures fall below 10°C.

A new study says that from about 8000 to 5000 years ago it was warm enough in winter that could grow at the 40°N latitude in northern China. Today its warmth threshold growth limit is ~34°N.

Scientists can therefore deduce the Mid-Holocene winter temperatures needed to have been “7.7°C higher than today” at that time.

….

Global-Scale Warming Events Of ‘Up To 15 °C Within A Few Decades’ Have Occurred Since The Jurassic

Boulila et al., 2022 in NoTricksZone


A new study (Boulila et al., 2022) suggests “abrupt and severe changes in Earth’s past climate” have been occurring at ~1,500-year periodicities since the iceless Jurassic period.

Warming events of degrees C per within decades or less were at one time thought to have occurred only at locations like Greenland and the North Atlantic during the last glacial period (70 to 12 thousand years ago).

But the evidence has been piling up from locations throughout the globe (e.g., on continents and tropical to high latitude oceans, lakes, and rivers) indicating these warming events have “a global interconnection between the two hemispheres.”

These “abrupt and severe” global warming events with ~1,500-year periodicities can even be traced back to the iceless Jurassic period when Antarctica was a rainforest and 38°C warmer than today. This suggests the driving force for these global warming periods were not dependent on ice sheet dynamics.

 

Abstract

Earth’s past climate exhibits short-term (1500-year) pronounced fluctuations during the last glacial period, called Dansgaard–Oeschger (DO) glacial events, which have never been detected in pre-Quaternary times. The record of DO equivalent climate variability in Mesozoic strata can provide constraints on understanding these events. Here we highlight a prominent 1500-year cyclicity in a Jurassic (~ 155 Ma) ice-free sedimentary record from the Tethyan Basin. This Jurassic 1500-year cyclicity is encoded in high-resolution magnetic susceptibility (MS) proxy data reflecting detrital variations, and expressed as marl-limestone couplets. Additionally, MS data detect the modulation of these DO-scale couplets by supercouplet sets, reflecting the precession and its harmonics. We suggest that this Jurassic DO-like cyclicity may originate from paleo-monsoon-like system, analogous to the record of DO events in the Pleistocene East Asian monsoon archives. Paleogeographic reconstructions and atmosphere–ocean simulations further support the potential existence of strong, ancient monsoon circulations in the Tethyan Basin during the Jurassic.

2021-2022 Tonga Volcanic Eruption and Record Rainfall in Eastern Australia and New Zealand

by A. Wong & W. Yims, Jul 4, 2022 in The SaltbushClub


Summary

During late 2021, the Hunga Tonga-Hunga Ha’apai submarine volcano erupted creating a new island which erupted sub-aerially on 15th January, 2022 sending a plume 58 km above sea level penetrating the mesosphere. The study of observation records including satellite data has revealed warming of the ocean-surface layer followed by atmospheric cooling caused by the release of geothermal heat and volcanic materials entering the atmosphere respectively. Environmental factors influencing weather include the development of a relatively ‘short’ life-span South Pacific Blob; the transfer of large quantities of water vapour from the ocean into the atmosphere; the low-pressure condition on the ocean surface; the formation of clouds; the reduction of solar radiation caused by volcanic materials in the atmosphere; the strengthening of trade winds; the meandering of jet streams; the development of atmospheric rivers, the additional cooling effect of torrential rainfall, and, the switch to La Niña conditions. The record rainfall in eastern Australia and New Zealand and Tropical Cyclone Dovi occurring in February 2022 were both outcomes of atmospheric cooling following the sub-aerial eruption.

CO2 and O2 oxidized 2.7 Ga micrometeorites in two stages suggesting a >32% CO2 atmosphere

by Huang G. et al., Nov 2021 in PrecambrianResearch


Abstract
It is widely accepted that atmospheric pO2 < 1 ppm before the Great Oxidation Event. Yet a recent study found fossil micrometeorites (MMs) containing the oxidized iron species wüstite (FeO) and magnetite (Fe3O4) formed 2.7 billion years ago (Ga). How these MMs became oxidized is uncertain. Abundant O2 in the upper atmosphere and iron oxidation by CO2 have been suggested. However, photochemical reactions cannot produce sufficient O2, and oxidation by CO2 can only produce FeO, each individually failing to explain the formation of Fe3O4-only MMs. Using an oxidation model of iron MMs including photochemistry, we show that a >32% CO2 Archean atmosphere and different entry angles can generate the Fe3O4-only and Fe-FeO mixed composition MMs that have been discovered. Oxidation happens in two stages: by CO2 under brief melting, then by O2. Our results challenge existing constraints on Earth’s atmospheric CO2 concentration at 2.7 Ga and support a warm Late Archean despite the ‘faint young Sun’.

Rapid Asia–Europe–North America geographic dispersal of earliest Eocene primate Teilhardina during the Paleocene–Eocene Thermal Maximum

by T. Smith et al., July 25, 2022 in PNAS


Abstract

True primates appeared suddenly on all three northern continents during the 100,000-yr-duration Paleocene–Eocene Thermal Maximum at the beginning of the Eocene, ≈55.5 mya. The simultaneous or nearly simultaneous appearance of euprimates on northern continents has been difficult to understand because the source area, immediate ancestors, and dispersal routes were all unknown. Now, omomyid haplorhine Teilhardinais known on all three continents in association with the carbon isotope excursion marking the Paleocene–Eocene Thermal Maximum. Relative position within the carbon isotope excursion indicates that Asian Teilhardina asiatica is oldest, European Teilhardina belgicais younger, and North American Teilhardina brandti and Teilhardina americana are, successively, youngest. Analysis of morphological characteristics of all four species supports an Asian origin and a westward Asia-to-Europe-to-North America dispersal for Teilhardina. High-resolution isotope stratigraphy indicates that this dispersal happened in an interval of ≈25,000 yr. Rapid geographic dispersal and morphological character evolution in Teilhardina reported here are consistent with rates observed in other contexts.

Correcting Misinformation on Atmospheric Carbon Dioxide

by Bud Bromley, May 20, 2022 in budbromley


Abstract

Digital signal processing technology was used to analyze daily carbon dioxide data from the joint NOAA – Scripps Oceanographic Institution’s Global Monitoring Laboratory (MLO).  The period surrounding the 1991 eruption of the Pinatubo volcano was rigorously analyzed for slope and acceleration of net global average atmospheric CO2 concentration and found to be consistent with the theory that Henry’s Law, the Law of Mass Action, and Le Chatelier’s principle control net global average atmospheric CO2 concentration rather than human-produced CO2 emissions.  Background and theory are explained.  A method of using common physics and math for a novel purpose is presented to compare natural CO2emission or absorption with human-produced CO2 emission.  The claim that human-produced CO2 emission is causing increasing global CO2 concentration and climate change is shown to be without scientific merit.  

Key words: carbon, CO2, climate, warming, Impulse, Pinatubo, Henry’s Law, Mauna Loa 

Figure 1. Photo of Pinatubo eruption by Dave Harlowe, USGS. Public domain

PERMAFROST AND CLIMATE CHANGE IN ICELAND

by B. Van Vliet-Lanoé & A. Gudmundsson, Feb 2020, in ResearchGate


Permafrost developed from Termination Ia (Bölling interstadial, 14.5 cal ka BP) in Northern Iceland, in answer to deglaciation. Permafrost persisted or even re-extended during the Preboreal cooling events (at 11.2, 10.3 and 9.3 cal ka BP) synchronic with pulsated glacial advances. It disappeared below 1000 masl during the Thermal Optimum (8-5 cal ka BP). The present-day re-extent was controlled with the cooling related with the Little Ice Age and particularily the Maunder solar Minimum. Continuous permafrost is stable above 1000 masl, but is today melting between 900 and 800 masl. Discontinuous permafrost is vanishing today with the recent climate warming (from 1970), especially in palsa bogs, and on valley slopes with thermokarstic mass wasting.

Holocene ice-free strait followed by dynamic Neoglacial fluctuations: Hornsund, Svalbard

by A. Osaka et al., Apr 25, 2022 in TheHolocene


Keywords

The recession of the Hornbreen-Hambergbreen glaciers (Hornsund, Svalbard) will lead to the formation of a strait between the Greenland and Barents Seas within a few decades. We provide evidence for the earlier existence of this strait, in the Early–Middle Holocene and presumably since 1.3 ka cal. BP until glacier advance 0.7 ± 0.3 ka or earlier. Radiocarbon dating of mollusc shells from the ground moraines in the Hornbreen forefield indicate the existence of the marine environment at the contemporary glacierized head of Hornsund since 10.9 ka cal. BP or earlier due to glacier retreat. The gap in the radiocarbon dates between 3.9 and 1.3 ka cal. BP and the published results of 10Be exposure dating on Treskelen suggest the strait’s closure after glacier advance in the Neoglacial. Subsequent re-opening occurred around 1.3 ka cal. BP, but according to 10Be dates from Treskelen, the strait has again been closed since ca. 0.7 ± 0.3 ka or earlier. The oldest known surge of Hornbreen occurred around 1900. Analysis of Landsat satellite images, morphometric indicators characterizing the glacier frontal zones and previous studies indicate one surge of Hambergbreen (1957–1968) and five re-advances of Hornbreen in the 20th century (after 1936, between 1958 and 1962, in 1986–1990, 1998–1999, 2011). While the warmer Holocene intervals might be a benchmark for the effects of future climate change, glacier dynamics in post-Little Ice Age climate warming seems to be an analogue of glacier retreats and re-advances in the earlier periods of the Holocene.

Sea Level: Rise and Fall – Slowing Down to Speed U

by Kip Hansen, Mai 3,2022 in WUWT


Yes, I do know that acceleration, technically, means just a change in velocity.  But, in every day English, we use acceleration to mean an increase in velocity – speeding up — and deceleration as a decrease in velocity – slowing down.  I mention acceleration and deceleration because one of the major talking points of IPCC reported findings about sea level rise, the incessant media mantra, is that “Sea Level Rise is Accelerating”.  (here, here, here, here, here and hundreds more here)

Is sea level rising?  Yes, of course it is.  It has been rising since about 1750-1775, coinciding with the end of the Little Ice Age.  This is widely accepted as shown below:

 

How do we know?  The important aspect of sea level is how it affects the land at the edges of the oceans.  The water level there is measure by tide gauges at the ports and harbors of the world.  The levels recorded by tide gauges are of local Relative Sea Level (RSL) – the level at which the sea surface hits the land.  This measurement includes both the actual rise in the sea surface height (think: distance from the center of the Earth) plus any vertical movement (VLM) of the tide gauge itself, either up or down.  In many locations the land mass itself is subsiding (sinking) due to glacial isostatic adjustment (GIA) as the land mass readjusts itself for the melting of the glaciers of the last great  Ice Age and at most tide gauge locations, the structure to which the tide gauge tself is attached, such as a pier or dock or sea wall, is also itself subsiding due to compaction of the soil underneath and the fact that many such locations are built on man-made filled substrate.  To see if sea level is rising, it is only necessary to look at high quality tide gauge records for whom the VLM is known to be relatively constant.  The linearity of these graphs is typical, there are many, many more.

The inter-glacial cycle is not a 100,000-year cycle, it is a shorter cycle with missing beats

by M.O. Jonas, 2022, WorldJ.Adv.ResReviews


Review Article
World Journal of Advanced Research and Reviews, 2022, 13(03), 388–392
Article DOI: 10.30574/wjarr.2022.13.3.0259
Publication history:
Received on 18 February 2022; revised on 20 March 2022; accepted on 22 March 2022
Abstract:
The “100,000-year problem” refers to an apparent unexplained change in the frequency of inter-glacial periods which occurred about a million years ago. Before that, inter-glacial periods seemed to occur about every 41,000 years, in line with the obliquity Milankovich cycle. But after that, they seemed to occur about every 100,000 years, in line with the orbital inclination Milankovich cycle. Examination of the data shows that there never was a 41,000-year cycle, and that there is no 100,000-year cycle, but that the most influential cycle is the approx 21,000-year precession cycle which is the major factor in the cycles of insolation at higher latitudes. Insolation at 65N is generally regarded as the most significant of these. Inspection of the data shows that every glacial termination (start of an inter-glacial period) began at a time when insolation at 65N increased from a low point in its cycle. That not every such cycle triggered a new inter-glacial period underlines the chaotic non-linear nature of Earth’s climate. Until about a million years ago, this cycle occasionally “missed a beat”, making the inter-glacial frequency average about 41,000 years. After that, the cycle started missing more “beats”, making the inter-glacial frequency average about 100,000 years. There never was an actual 41,000-year or 100,000-year inter-glacial cycle.
Keywords:
Climate; Glacial Termination; Inter-Glacial; Milankovich Cycle; Non-Linear; Precession
Full text article in PDF:

A new volcanic province: an inventory of subglacial volcanoes in West Antarctica

by M. van Wyk et al., May 29, 2017 in LyellSpecPublications


(a) Location of the main components of the West Antarctic Rift System and confirmed volcanoes (red circles: after LeMasurier et al. 1990; Smellie & Edwards 2016). (b) Location of Holocene volcanoes (red circles) in the Ethiopia/Kenya branch of the East African Rift (red shaded area). The majority of this activity is aligned along the rift axis with occasional flank volcanism. Data from Siebert & Simkin (2002) and Global Volcanism Program (2013).

 Abstract

The West Antarctic Ice Sheet overlies the West Antarctic Rift System about which, due to the comprehensive ice cover, we have only limited and sporadic knowledge of volcanic activity and its extent. Improving our understanding of subglacial volcanic activity across the province is important both for helping to constrain how volcanism and rifting may have influenced ice-sheet growth and decay over previous glacial cycles, and in light of concerns over whether enhanced geothermal heat fluxes and subglacial melting may contribute to instability of the West Antarctic Ice Sheet. Here, we use ice-sheet bed-elevation data to locate individual conical edifices protruding upwards into the ice across West Antarctica, and we propose that these edifices represent subglacial volcanoes. We used aeromagnetic, aerogravity, satellite imagery and databases of confirmed volcanoes to support this interpretation. The overall result presented here constitutes a first inventory of West Antarctica’s subglacial volcanism. We identified 138 volcanoes, 91 of which have not previously been identified, and which are widely distributed throughout the deep basins of West Antarctica, but are especially concentrated and orientated along the >3000 km central axis of the West Antarctic Rift System.

Ancient Ice Reveals Scores of Gigantic Volcanic Eruptions

by C. Rotter, Mar 15, 2022 in WUWT/ClimPast


Magnitude, frequency and climate forcing of global volcanism during the last glacial period as seen in Greenland and Antarctic ice cores (60–9 ka)

Abstract

Large volcanic eruptions occurring in the last glacial period can be detected by their accompanying sulfuric acid deposition in continuous ice cores. Here we employ continuous sulfate and sulfur records from three Greenland and three Antarctic ice cores to estimate the emission strength, the frequency and the climatic forcing of large volcanic eruptions that occurred during the second half of the last glacial period and the early Holocene, 60–9 kyr before 2000 CE (b2k). Over most of the investigated interval the ice cores are synchronized, making it possible to distinguish large eruptions with a global sulfate distribution from eruptions detectable in one hemisphere only. Due to limited data resolution and large variability in the sulfate background signal, particularly in the Greenland glacial climate, we only list Greenland sulfate depositions larger than 20 kg km−2 and Antarctic sulfate depositions larger than 10 kg km−2. With those restrictions, we identify 1113 volcanic eruptions in Greenland and 737 eruptions in Antarctica within the 51 kyr period – for which the sulfate deposition of 85 eruptions is found at both poles (bipolar eruptions). Based on the ratio of Greenland and Antarctic sulfate deposition, we estimate the latitudinal band of the bipolar eruptions and assess their approximate climatic forcing based on established methods. A total of 25 of the identified bipolar eruptions are larger than any volcanic eruption occurring in the last 2500 years, and 69 eruptions are estimated to have larger sulfur emission strengths than the Tambora, Indonesia, eruption (1815 CE). Throughout the investigated period, the frequency of volcanic eruptions is rather constant and comparable to that of recent times. During the deglacial period (16–9 ka b2k), however, there is a notable increase in the frequency of volcanic events recorded in Greenland and an obvious increase in the fraction of very large eruptions. For Antarctica, the deglacial period cannot be distinguished from other periods. This confirms the suggestion that the isostatic unloading of the Northern Hemisphere (NH) ice sheets may be related to the enhanced NH volcanic activity. Our ice-core-based volcanic sulfate records provide the atmospheric sulfate burden and estimates of climate forcing for further research on climate impact and understanding the mechanism of the Earth system.How to cite. Lin, J., Svensson, A., Hvidberg, C. S., Lohmann, J., Kristiansen, S., Dahl-Jensen, D., Steffensen, J. P., Rasmussen, S. O., Cook, E., Kjær, H. A., Vinther, B. M., Fischer, H., Stocker, T., Sigl, M., Bigler, M., Severi, M., Traversi, R., and Mulvaney, R.: Magnitude, frequency and climate forcing of global volcanism during the last glacial period as seen in Greenland and Antarctic ice cores (60–9 ka), Clim. Past, 18, 485–506, https://doi.org/10.5194/cp-18-485-2022,