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  • richardmitnick 2:10 pm on July 9, 2021 Permalink | Reply
    Tags: "Early humans were sheltered from worst effects of volcanic supereruption", , , Neanderthals and Denisovans were living in Europe and Asia at this time., North America Europe and Asia bore the brunt of the cooling., Palaeoclimatology, , , Regions in southern Africa and India may have seen decreases in precipitation at the highest sulphur emission level., Toba supereruption, ,   

    From University of Cambridge (UK) : “Early humans were sheltered from worst effects of volcanic supereruption” 

    U Cambridge bloc

    From University of Cambridge (UK)

    05 Jul 2021
    Sarah Collins
    sarah.collins@admin.cam.ac.uk

    1
    Site of the Toba supereruption, in present-day Indonesia. Credit: Clive Oppenheimer.

    A massive volcanic eruption in Indonesia about 74,000 years ago likely caused severe climate disruption in many areas of the globe, but early human populations were sheltered from the worst effects, suggests a new study published in the journal PNAS.

    The eruption of the Toba volcano was the largest volcanic eruption in the past two million years, but its impacts on climate and human evolution have been unclear. Resolving this debate is important for understanding environmental changes during a key interval in human evolution.

    “We were able to use a large number of climate model simulations to resolve what seemed like a paradox,” said lead author Benjamin Black from Rutgers University (US). “We know this eruption happened and that past climate modeling has suggested the climate consequences could have been severe, but archaeological and palaeoclimate records from Africa don’t show such a dramatic response.

    “Our results suggest that we might not have been looking in the right place to see the climate response. Africa and India are relatively sheltered, whereas North America Europe and Asia bear the brunt of the cooling. One intriguing aspect of this is that Neanderthals and Denisovans were living in Europe and Asia at this time, so our paper suggests evaluating the effects of the Toba eruption on those populations could merit future investigation.”

    The researchers analysed 42 global climate model simulations in which they varied magnitude of sulphur emissions, time of year of the eruption, background climate state and sulfur injection altitude to make a probabilistic assessment of the range of climate disruptions the Toba eruption may have caused.

    The results suggest there was likely significant regional variation in climate impacts. The simulations predict cooling in the Northern Hemisphere of at least 4°C, with regional cooling as high as 10°C depending on the model parameters.

    In contrast, even under the most severe eruption conditions, cooling in the Southern Hemisphere — including regions populated by early humans – was unlikely to exceed 4°C, although regions in southern Africa and India may have seen decreases in precipitation at the highest sulphur emission level.

    The results explain independent archaeological evidence suggesting the Toba eruption had modest effects on the development of hominid species in Africa. According to the authors, their ensemble simulation approach could be used to better understand other past and future explosive eruptions.

    “Our work is not only a forensic analysis of Toba’s aftermath some 74,000 years ago, but also a means of understanding the unevenness of the effects such very large eruptions may have on today’s society,” said co-author Dr Anja Schmidt from the University of Cambridge. “Ultimately, this will help to mitigate the environmental and societal hazards from future volcanic eruptions.”

    The study included researchers from the US National Center for Atmospheric Research, the University of Leeds (UK) and University of Cambridge in the UK, and was supported by the National Center for Atmospheric Research and the National Science Foundation (US).

    See the full article here .

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    U Cambridge Campus

    The University of Cambridge (UK) [legally The Chancellor, Masters, and Scholars of the University of Cambridge] is a collegiate public research university in Cambridge, England. Founded in 1209 Cambridge is the second-oldest university in the English-speaking world and the world’s fourth-oldest surviving university. It grew out of an association of scholars who left the University of Oxford(UK) after a dispute with townsfolk. The two ancient universities share many common features and are often jointly referred to as “Oxbridge”.

    Cambridge is formed from a variety of institutions which include 31 semi-autonomous constituent colleges and over 150 academic departments, faculties and other institutions organised into six schools. All the colleges are self-governing institutions within the university, each controlling its own membership and with its own internal structure and activities. All students are members of a college. Cambridge does not have a main campus and its colleges and central facilities are scattered throughout the city. Undergraduate teaching at Cambridge is organised around weekly small-group supervisions in the colleges – a feature unique to the Oxbridge system. These are complemented by classes, lectures, seminars, laboratory work and occasionally further supervisions provided by the central university faculties and departments. Postgraduate teaching is provided predominantly centrally.

    Cambridge University Press a department of the university is the oldest university press in the world and currently the second largest university press in the world. Cambridge Assessment also a department of the university is one of the world’s leading examining bodies and provides assessment to over eight million learners globally every year. The university also operates eight cultural and scientific museums, including the Fitzwilliam Museum, as well as a botanic garden. Cambridge’s libraries – of which there are 116 – hold a total of around 16 million books, around nine million of which are in Cambridge University Library, a legal deposit library. The university is home to – but independent of – the Cambridge Union – the world’s oldest debating society. The university is closely linked to the development of the high-tech business cluster known as “Silicon Fe”. It is the central member of Cambridge University Health Partners, an academic health science centre based around the Cambridge Biomedical Campus.

    By both endowment size and consolidated assets Cambridge is the wealthiest university in the United Kingdom. In the fiscal year ending 31 July 2019, the central university – excluding colleges – had a total income of £2.192 billion of which £592.4 million was from research grants and contracts. At the end of the same financial year the central university and colleges together possessed a combined endowment of over £7.1 billion and overall consolidated net assets (excluding “immaterial” historical assets) of over £12.5 billion. It is a member of numerous associations and forms part of the ‘golden triangle’ of English universities.

    Cambridge has educated many notable alumni including eminent mathematicians; scientists; politicians; lawyers; philosophers; writers; actors; monarchs and other heads of state. As of October 2020 121 Nobel laureates; 11 Fields Medalists; 7 Turing Award winners; and 14 British prime ministers have been affiliated with Cambridge as students; alumni; faculty or research staff. University alumni have won 194 Olympic medals.

    History

    By the late 12th century the Cambridge area already had a scholarly and ecclesiastical reputation due to monks from the nearby bishopric church of Ely. However it was an incident at Oxford which is most likely to have led to the establishment of the university: three Oxford scholars were hanged by the town authorities for the death of a woman without consulting the ecclesiastical authorities who would normally take precedence (and pardon the scholars) in such a case; but were at that time in conflict with King John. Fearing more violence from the townsfolk scholars from the University of Oxford started to move away to cities such as Paris; Reading; and Cambridge. Subsequently enough scholars remained in Cambridge to form the nucleus of a new university when it had become safe enough for academia to resume at Oxford. In order to claim precedence it is common for Cambridge to trace its founding to the 1231 charter from Henry III granting it the right to discipline its own members (ius non-trahi extra) and an exemption from some taxes; Oxford was not granted similar rights until 1248.

    A bull in 1233 from Pope Gregory IX gave graduates from Cambridge the right to teach “everywhere in Christendom”. After Cambridge was described as a studium generale in a letter from Pope Nicholas IV in 1290 and confirmed as such in a bull by Pope John XXII in 1318 it became common for researchers from other European medieval universities to visit Cambridge to study or to give lecture courses.

    Foundation of the colleges

    The colleges at the University of Cambridge were originally an incidental feature of the system. No college is as old as the university itself. The colleges were endowed fellowships of scholars. There were also institutions without endowments called hostels. The hostels were gradually absorbed by the colleges over the centuries; but they have left some traces, such as the name of Garret Hostel Lane.

    Hugh Balsham, Bishop of Ely, founded Peterhouse – Cambridge’s first college in 1284. Many colleges were founded during the 14th and 15th centuries but colleges continued to be established until modern times. There was a gap of 204 years between the founding of Sidney Sussex in 1596 and that of Downing in 1800. The most recently established college is Robinson built in the late 1970s. However Homerton College only achieved full university college status in March 2010 making it the newest full college (it was previously an “Approved Society” affiliated with the university).

    In medieval times many colleges were founded so that their members would pray for the souls of the founders and were often associated with chapels or abbeys. The colleges’ focus changed in 1536 with the Dissolution of the Monasteries. Henry VIII ordered the university to disband its Faculty of Canon Law and to stop teaching “scholastic philosophy”. In response, colleges changed their curricula away from canon law and towards the classics; the Bible; and mathematics.

    Nearly a century later the university was at the centre of a Protestant schism. Many nobles, intellectuals and even commoners saw the ways of the Church of England as too similar to the Catholic Church and felt that it was used by the Crown to usurp the rightful powers of the counties. East Anglia was the centre of what became the Puritan movement. In Cambridge the movement was particularly strong at Emmanuel; St Catharine’s Hall; Sidney Sussex; and Christ’s College. They produced many “non-conformist” graduates who, greatly influenced by social position or preaching left for New England and especially the Massachusetts Bay Colony during the Great Migration decade of the 1630s. Oliver Cromwell, Parliamentary commander during the English Civil War and head of the English Commonwealth (1649–1660), attended Sidney Sussex.

    Modern period

    After the Cambridge University Act formalised the organisational structure of the university the study of many new subjects was introduced e.g. theology, history and modern languages. Resources necessary for new courses in the arts architecture and archaeology were donated by Viscount Fitzwilliam of Trinity College who also founded the Fitzwilliam Museum. In 1847 Prince Albert was elected Chancellor of the University of Cambridge after a close contest with the Earl of Powis. Albert used his position as Chancellor to campaign successfully for reformed and more modern university curricula, expanding the subjects taught beyond the traditional mathematics and classics to include modern history and the natural sciences. Between 1896 and 1902 Downing College sold part of its land to build the Downing Site with new scientific laboratories for anatomy, genetics, and Earth sciences. During the same period the New Museums Site was erected including the Cavendish Laboratory which has since moved to the West Cambridge Site and other departments for chemistry and medicine.

    The University of Cambridge began to award PhD degrees in the first third of the 20th century. The first Cambridge PhD in mathematics was awarded in 1924.

    In the First World War 13,878 members of the university served and 2,470 were killed. Teaching and the fees it earned came almost to a stop and severe financial difficulties followed. As a consequence the university first received systematic state support in 1919 and a Royal Commission appointed in 1920 recommended that the university (but not the colleges) should receive an annual grant. Following the Second World War the university saw a rapid expansion of student numbers and available places; this was partly due to the success and popularity gained by many Cambridge scientists.

     
  • richardmitnick 12:23 pm on December 19, 2019 Permalink | Reply
    Tags: "What Lies Beneath Is Important for Ice Sheets", , , Palaeoclimatology, , , , The topography under Antarctic ice, Thwaites Glacier, Topography Matters   

    From Durham University via Eos: “What Lies Beneath Is Important for Ice Sheets” 

    Durham U bloc

    From Durham University

    via

    AGU
    Eos news bloc

    Eos

    12.19.19
    Sarah Derouin

    1
    The topography beneath Thwaites Glacier, above, is largely below sea level and slopes inland. Credit: NASA/James Yungel

    Ice sheets blanket continents, obscuring nooks, crannies, and even mountains below. The lay of the land underneath ice sheets is not just a side note—the topography is crucially important to how the overlying ice might behave.

    For years, researchers have been reconstructing the topography under Antarctic ice, essentially “peering” through the ice sheets with technology like ice-penetrating radar surveys.

    A team of scientists wanted to better understand how the topography changed under these continental-sized glaciers, so they worked backward, reconstructing the under-ice topography of Antarctica over the past 34 million years.

    They found that over time, Antarctic topography has become progressively lower. The researchers noted that their reconstructions can provide important boundary conditions for modelers who are trying to estimate ice volumes and sea levels during past climatic changes.

    Topography Matters

    The ice sheets of Antarctica are big players in global sea level rise. Researchers are interested in how the East Antarctic and West Antarctic Ice Sheets behaved in the past, and they rely on modeling to reconstruct ice flows.

    “Bed topography is a really important boundary condition in ice sheet models,” said Guy Paxman, a geophysicist at Durham University in the United Kingdom and lead author of the new study, published in Palaeogeography, Palaeoclimatology, Palaeoecology.

    “If researchers are modeling ice sheets in deep geological time, they need to have a more realistic version of the topography than just using the present-day topography,” he added.

    Two big factors control how ice sheets behave: the extent of land below sea level and the slope of the bed. Both characteristics can contribute to seawater seeping under the ice, a situation that encourages the glacier to start floating, become unstable, and break up. As ice sheets become unstable, they can retreat and contribute to sea level rise.

    Contemporary topographic maps show that most of the bed in West Antarctica is below sea level and slopes inland. Because of that, West Antarctic glaciers such as Thwaites are of particular interest to researchers, said Dustin Schroeder, a radio glaciologist at Stanford University who was not involved with the study.

    “One of the reasons we’re studying Thwaites Glacier is because of its shape,” said Schroeder, who added that like the Antarctic ice sheets themselves, the massive glacier could have been a big contributor to sea level rise in the past.

    Bedrock Changes over Time

    To better understand paleotopographic evolution in Antarctica, the team looked at four time slices in which significant climatic changes were preserved in the geologic record: 34 million years ago (when ice started to accumulate), 23 million years ago, 14 million years ago, and 3.5 million years ago.

    Paxman said their study is the first attempt to reconstruct Antarctic topography for multiple time periods beginning when ice first started to accumulate. To do that, the team had to piece together an immense amount of data on erosion, volcanism, and land subsidence from both crustal rifting and the weight of the overlying ice.

    To reconstruct erosion over the past 34 million years, the team examined sediment accumulation around the continent. Offshore seismic data helped them reconstruct how much land was lost through erosion, and deep-sea drilling cores helped build a more complete picture of the rate of sediment accumulation.

    The team found that glacial erosion rates in East Antarctica appeared to be higher during the Oligocene, the first 10–15 million years of Antarctic glaciation. Paxman noted that erosion started to slow down after the middle Miocene (about 14 million years ago).

    “This is the opposite situation [than] in West Antarctica, where erosion has picked up since the mid-Miocene,” he said.

    In addition to erosion rates, the team looked at ice loading and the effects of rifting in West Antarctica, including thermal subsidence. Overall, the researchers determined that Antarctica’s topography has gotten progressively lower over time: 34 million years ago, there was about 25% more land above sea level than there is today.

    3
    These simplified maps compare Antarctic topography 34 million years ago with the continent’s present-day subglacial topography. Gray represents topography above modern sea level, and blue is topography below modern sea level. Credit: Guy Paxman

    “The most significant changes we tend to find are in the [West] Antarctic rift system,” said Paxman, but he added that there were also large changes in East Antarctica, especially in basins around margins of the continent.

    Paleotopography in Practice

    The new research shows that West Antarctica has changed a lot over time. “This paper said [that] in the past, the shape [of West Antarctica] was different—and really different,” said Schroeder. “That is where it is provocative and interesting.”

    “When we do long-timescale modeling studies on these different topographies, I’m looking forward to seeing if that gives us insights into how things changed in the past,” said Schroeder. He added that this work might give additional insights into how uplift and erosion could affect glaciology and ice vulnerability. “I think it really gives us a tool to ask some important questions that were much harder to ask before.”

    The team hopes that researchers will find the work useful for future studies. “These topographies are freely available to download,” said Paxman. “We’re really encouraging people [to download them.] If they want to model ice sheets in the past, these topographies are there as a boundary condition for whoever wants to look at some of these questions about past Antarctic ice sheets.”

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Durham U campus

    Durham University is distinctive – a residential collegiate university with long traditions and modern values. We seek the highest distinction in research and scholarship and are committed to excellence in all aspects of education and transmission of knowledge. Our research and scholarship affect every continent. We are proud to be an international scholarly community which reflects the ambitions of cultures from around the world. We promote individual participation, providing a rounded education in which students, staff and alumni gain both the academic and the personal skills required to flourish.

     
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