* Astronomy

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RE: The ancient sea

Blobrana · L

Ancient oceans belched stagnant CO2 into the skies

At the end of the last ice age, atmospheric carbon dioxide levels shot up by nearly 50 per cent. But where did the CO2 come from? This long-standing climatic mystery has now been solved.
Climate scientists have suspected - but never been able to prove - that the CO2 was the result of a huge belch of gas from the oceans. They predicted that the ice age had slowed ocean circulation, trapping CO2 deep within it, and that warmer temperatures reversed this process.
Signs of stagnant CO2-rich water have now been discovered 3700 metres beneath the Southern Ocean's seabed, between Antarctica and South Africa.
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Title: Mid-Holocene sea-level highstand along the Southeast Coast of China.
Authors: Dr Yongqiang Zong

Various sea-level curves have been proposed for the coast of China in the past two decades. These sea-level curves indicate a complex history of Holocene sea level, and so the debate on whether or not a higher mid-Holocene sea-level highstand exists in the coast of China has continued. This paper aims to re-examine the Holocene sea-level history for the low latitude part of the China coast (between 18°N and 32°N) by re-assessing all the sea-level data available from the east to south coasts and separating them according to geological settings in order to examine the influences of global and local factors. The reconstructed sea-level histories from different coastal sectors of the China coast reveal a certain degree of variability in the timing and height of mid-Holocene sea-level highstand. Within large river deltas, the mid-Holocene sea-level highstand occurred earlier by almost 1000 years than that from other coastal sites. The highstand from large river deltas appears also lower in altitude (a few metres below the present-day sea level) due probably to the local factors of subsidence and sediment consolidation. In geologically stable coastal sites, the highstand is recorded at the same altitude as the present-day sea level. A 1-2 m higher highstand is found from sites where tectonic uplift is observed.

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Blobrana · L

Why Early Earth's Oceans Didn't Freeze

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Early Earth stayed warm because its ocean absorbed more sunlight; greenhouse gases were not involved, Stanford researchers say

Four billion years ago, our then stripling sun radiated only 70 to 75 percent as much energy as it does today. Other things on Earth being equal, with so little energy reaching the planet's surface, all water on the planet should been have frozen. But ancient rocks hold ample evidence that the early Earth was awash in liquid water - a planetary ocean of it. So something must have compensated for the reduced solar output and kept Earth's water wet.
To explain this apparent paradox, a popular theory holds there must have been higher concentrations of greenhouse gases in the atmosphere, most likely carbon dioxide, which would have helped retain a greater proportion of the solar energy that arrived.
But a team of earth scientists including researchers from Stanford have analysed the mineral content of 3.8-billion-year-old marine rocks from Greenland and concluded otherwise.
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Rate of ocean acidification the fastest in 65 million years

A new model, capable of assessing the rate at which the oceans are acidifying, suggests that changes in the carbonate chemistry of the deep ocean may exceed anything seen in the past 65 million years.
The model also predicts much higher rates of environmental change at the oceans surface in the future than have occurred in the past, potentially exceeding the rate at which plankton can adapt.
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Carbonate veins reveal chemistry of ancient seawater

The chemical composition of our oceans is not constant but has varied significantly over geological time. In a study published this week in Science, researchers describe a novel method for reconstructing past ocean chemistry using calcium carbonate veins that precipitate from seawater-derived fluids in rocks beneath the seafloor. The research was led by scientists from the University of Southampton's School of Ocean and Earth Science (SOES) hosted at the National Oceanography Centre, Southampton (NOCS).

"Records of ancient seawater chemistry allow us to unravel past changes in climate, plate tectonics and evolution of life in the oceans. These processes affect ocean chemistry and have shaped our planet over millions of years" - Dr Rosalind Coggon, formerly of NOCS now at Imperial College London.

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Contrary to preconceived notions, the atmosphere and the oceans were perhaps not formed from vapors emitted during intense volcanism at the dawning of our planet. Francis Albarède of the Laboratoire des Sciences de la Terre (CNRS / ENS Lyon / Université Claude Bernard) suggests that water was not part of the Earth's initial inventory but stems from the turbulence caused in the outer Solar System by giant planets. Ice-covered asteroids thus reached the Earth around one hundred million years after the birth of the planets.
It is widely accepted that terrestrial planets are formed over several million years by the agglomeration of asteroids (of kilometric size) then protoplanets (of the size of Mars). The arrival of the last of these large objects corresponds to the lunar impact, 30 million years after the formation of the Solar System. Initially, this hurly-burly took place between planetary objects located within the snow line, in other words between the Sun and the asteroid belt. This space, swept by the electromagnetic winds of the young Sun, was then too hot for water and volatile elements to condense within it.
The major delivery of volatile elements on our planet could have corresponded to a phenomenon that occurred some tens of millions of years after the lunar impact: this was the big clean up of the outer Solar System initiated by the giant planets. Due to their very strong gravity, they sent the final ice-rich planetary rubble in all directions, including in our own direction. Penetrating into the mantle through the surface, the water could then have softened the Earth and reduced the strain at which materials shatter. Plate tectonics then began and with it the emergence of continents, conditions probably necessary for the appearance of life. Mars dried out before water managed to penetrate in depth and, as regards Venus, the conditions that reigned before the violent remodelling of its surface, 800 million years ago, by intense volcanism are still not known.

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Lizette Leon-Rodriguez had never been on a boat for more than a couple of hours before embarking upon the voyage of a lifetime.
The Rice graduate student recently returned to campus after two months aboard the JOIDES Resolution, a research ship operated by the Integrated Ocean Drilling Program. She spent all night every night on that ship analysing core samples for clues that may ultimately reveal something about the near- and long-term fate of Earth's ocean-atmosphere dynamics.
A palaeontologist specialising in planktonic foraminifers, she was one of 27 scientists among the crew of 120 that left Hawaii in March for a trip that saw the vessel skirt the equator. There, the crew drilled hundreds of meters of core samples to give them a glimpse at what the planet looked like in the Eocene period, approximately 55 to 34 million years ago.
It turns out there's a lot that the remains of ancient plankton can tell about the Earth back then, when atmospheric carbon dioxide peaked and the planet suffered several periods of global warming very much like what many fear today. Sinking to the sea floor in a constant shower over millions of years, the "forams" and their calcium carbonate shells are buried in the sediment, creating a fossil record that goes back millions of years.

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Red jasper cored from layers 3.46 billion years old suggests that not only did the oceans contain abundant oxygen then, but that the atmosphere was as oxygen rich as it is today, according to geologists.
This jasper or hematite-rich chert formed in ways similar to the way this rock forms around hydrothermal vents in the deep oceans today.

"Many people have assumed that the hematite in ancient rocks formed by the oxidation of siderite in the modern atmosphere. That is why we wanted to drill deeper, below the water table and recover unweathered rocks" - Hiroshi Ohmoto, professor of geochemistry, Penn State.

The researchers drilled diagonally into the base of a hill in the Pilbara Craton in northwest Western Australia to obtain samples of jasper that could not have been exposed to the atmosphere or water. These jaspers could be dated to 3.46 billion years ago.

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