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Improved understanding of a widely used 'thermometer' for Earth's ancient oceans

Scientists have improved our ability to interpret one of the most common measures of the temperature of Earth's oceans in the distant past.
The measurement is based on the ancient remains of tiny marine organisms called foraminifera, a type of plankton that lives and feeds in water.
The organisms use calcium and magnesium from seawater to help form their shells - more magnesium when ocean temperatures are warmer and less when the temperatures are cooler. But magnesium levels can vary significantly within individual shells, and scientists have been exploring why.

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Oldest Known Redox Gradient Discovered

By analysing iron isotopes against the uranium content in the jasper rock from the ancient ocean of the Barberton Greenstone Belt in South Africa, scientists have found a defined vertical redox gradient, called a redoxcline, showing a change in the level of oxygenation from the deeper part of the ocean leading to the shallower portion.
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New Study Finds Oceans Arrived Early to Earth

Earth is known as the Blue Planet because of its oceans, which cover more than 70 percent of the planet's surface and are home to the world's greatest diversity of life. While water is essential for life on the planet, the answers to two key questions have eluded us: where did Earth's water come from and when?
While some hypothesize that water came late to Earth, well after the planet had formed, findings from a new study led by scientists at the Woods Hole Oceanographic Institution (WHOI) significantly move back the clock for the first evidence of water on Earth and in the inner solar system.

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Earth’s Water
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Solar System Ice: Source of Earth's Water

Scientists have long believed that comets and, or a type of very primitive meteorite called carbonaceous chondrites were the sources of early Earth's volatile elements - which include hydrogen, nitrogen, and carbon - and possibly organic material, too. Understanding where these volatiles came from is crucial for determining the origins of both water and life on the planet. New research led by Carnegie's Conel Alexander focuses on frozen water that was distributed throughout much of the early Solar System, but probably not in the materials that aggregated to initially form Earth.
The evidence for this ice is now preserved in objects like comets and water-bearing carbonaceous chondrites. The team's findings contradict prevailing theories about the relationship between these two types of bodies and suggest that meteorites, and their parent asteroids, are the most-likely sources of the Earth's water. Their work is published July 12 by Science Express.

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Volcanoes Deliver Two Flavours of Water

Seawater circulation pumps hydrogen and boron into the oceanic plates that make up the seafloor, and some of this seawater remains trapped as the plates descend into the mantle at areas called subduction zones. By analysing samples of submarine volcanic glass near one of these areas, scientists found unexpected changes in isotopes of hydrogen and boron from the deep mantle. They expected to see the isotope "fingerprint" of seawater. But in volcanoes from the Manus Basin they also discovered evidence of seawater distilled long ago from a more ancient plate descent event, preserved for as long as 1 billion years. The data indicate that these ancient oceanic "slabs" can return to the upper mantle in some areas, and that rates of hydrogen exchange in the deep Earth may not conform to experiments. The research is published in the February 26, 2012, advanced on line publication of Nature Geoscience.
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Ancient Water
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Volcanic Glass Yields Evidence of Ancient Water

At underwater volcanoes in Southeast Asia, scientists have discovered evidence of ancient distilled seawater that has been preserved for 1 billion years.
Seawater circulation pumps hydrogen and boron isotopes - hydrogen and boron have both light and heavy isotopes, which have differing numbers of neutrons in their nuclei - into the oceanic plates that make up the seafloor. Some of this seawater remains trapped as the tectonic plates descend into the mantle at areas called subduction zones, which are infamous for unleashing huge earthquakes.

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Earth's Oceans
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Space Observatory Provides Clues to Creation of Earth's Oceans

Astronomers have found a new cosmic source for the same kind of water that appeared on Earth billions of years ago and created the oceans. The findings may help explain how Earth's surface ended up covered in water.
New measurements from the Herschel Space Observatory show that comet Hartley 2, which comes from the distant Kuiper Belt, contains water with the same chemical signature as Earth's oceans. This remote region of the solar system, some 30 to 50 times as far away as the distance between Earth and the sun, is home to icy, rocky bodies including Pluto, other dwarf planets and innumerable comets.

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First comet found with ocean-like water

New evidence supports the theory that comets delivered a significant portion of Earth's oceans, which scientists believe formed about 8 million years after the planet itself.
The findings, which involve a University of Michigan astronomer, are published Oct. 5 online in Nature.

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The Ancient Ocean
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Evidence for Iron-Rich Ancient Ocean Changes View of Earth's Early History

Over the last half-billion years, the ocean mostly has been full of oxygen and teeming with animal life. But earlier, before animals evolved, oxygen was harder to come by.
Now a new study, led by researchers at the University of California, Riverside (UCR), reveals that the ancient deep ocean was not only devoid of oxygen but also rich in iron, a key biological nutrient for nearly a billion years longer than previously thought--right through a key evolutionary interval that culminated in the first rise of animals.

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Ancient tides
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Ancient tides different from today - some dramatically higher

The ebb and flow of the ocean tides, generally thought to be one of the most predictable forces on Earth, are actually quite variable over long time periods, in ways that have not been adequately accounted for in most evaluations of prehistoric sea level changes.
Due to phenomena such as ice ages, plate tectonics, land uplift, erosion and sedimentation, tides have changed dramatically over thousands of years and may change again in the future, a new study concludes.
Some tides on the East Coast of the United States, for instance, may at times in the past have been enormously higher than they are today - a difference between low and high tide of 10-20 feet, instead of the current 3-6 foot range.
And tides in the Bay of Fundy, which today are among the most extreme in the world and have a range up to 55 feet, didn't amount to much at all about 5,000 years ago. But around that same time, tides on the southern U.S. Atlantic coast, from North Carolina to Florida, were about 75 percent higher.

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