Uranium isotope evidence for two episodes of deoxygenation during Oceanic Anoxic Event 2


"Oceanic Anoxic Event 2 (OAE 2), occurring ∼94 million years ago, was one of the most extreme carbon cycle and climatic perturbations of the Phanerozoic Eon. It was typified by a rapid rise in atmospheric CO2, global warming, and marine anoxia, leading to the widespread devastation of marine ecosystems. However, the precise timing and extent to which oceanic anoxic conditions expanded during OAE 2 remains unresolved. [...]"

Source: PNAS
Authors: Matthew O. Clarkson et al.
DOI: 10.1073/pnas.1715278115

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Oxygen loss could be a huge issue for oceans

"A major study into an ancient climate change event that affected a significant percentage of Earth’s oceans has brought into sharp focus a lesser-known villain in global warming: oxygen depletion. 

The study, just published in the prestigious Proceedings of the National Academy of Sciences (PNAS), examined a past period of global warming around 94 million years ago, when oceans became de-oxygenated.

This famous period in Earth’s geological history, known as an Oceanic Anoxic Event (OAE), was more severe and on much longer timescales than the current changes. But it has given the scientists studying this period an extreme case-study to help understand how the oceans are effected by high atmospheric CO2 emissions. [...]"

Source: University of Exeter News

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Earth’s Oceans Suffocate as Climate Change and Nutrient Loading Create “Dead Zones”

"A new research study from a Global Ocean Oxygen Network (GO2NE) team of scientists reveals that the number of low- and zero oxygen sites in the world’s oceans have increased dramatically in the past 50 years. The Intergovernmental Oceanographic Commission of the United Nations created the GO2NE working group to provide a multidisciplinary, global view of deoxygenation, with the end goal of advising policymakers on preserving marine resources by countering low oxygen. [...]"

Source: environmental monitor
Author: Karla Lant

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Top Ocean Research Organizations Develop Unified Voice at Scripps Meeting

Global research organization seeks to leverage technological advances to promote ocean protection

"Several dozen of the world’s top oceanographers were at Scripps Institution of Oceanography at the University of California San Diego last week to showcase advances in the technology used to observe the oceans.

At the 19th annual meeting of the Partnership for Observation of the Global Oceans (POGO), which Scripps Oceanography co-founded in 1999, leaders said that the organization has evolved from setting up scientific observation networks in the global oceans to encouraging the spread of oceanographic expertise worldwide. Now, said POGO Chair Karen Wiltshire, the organization seeks to create consensus among scientists to create a global voice calling attention to issues ranging from ocean acidification to deoxygenation and sustainable fishing. [...]"

Source: Scripps Institution of Oceanography

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Biogeochemical role of subsurface coherent eddies in the ocean: Tracer cannonballs, hypoxic storms, and microbial stewpots?


"Subsurface coherent eddies are well-known features of ocean circulation, but the sparsity of observations prevents an assessment of their importance for biogeochemistry. Here, we use a global eddying (0.1° ) ocean-biogeochemical model to carry out a census of subsurface coherent eddies originating from eastern boundary upwelling systems (EBUS), and quantify their biogeochemical effects as they propagate westward into the subtropical gyres.  [...]"

Source: Global Biogeochemical Cycles
Authors: Ivy Frenge et al.
DOI: 10.1002/2017GB005743

Ocean Deoxygenation – Another Global Challenge

"The ocean is facing unprecedented pressures that are causing massive ecosystem and nutrient cycle disruption the result of industrial-scale depletion of ocean wildlife and destabilization of steady-state ecosystems. This occurs not only on the seafloor by trawling, dredging, drilling, and mining but also in the water column with nets, long lines, fish aggregating devices and other techniques; methods introduced in recent decades to extract with unprecedented speed and scale from ecosystems hundreds of millions of years in the making.  [...]"

Source: GIS and Science
Author: Matt Artz

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Tropical Atlantic climate and ecosystem regime shifts during the Paleocene–Eocene Thermal Maximum


"The Paleocene–Eocene Thermal Maximum (PETM, 56 Ma) was a phase of rapid global warming associated with massive carbon input into the ocean–atmosphere system from a C-depleted reservoir. Many midlatitude and high-latitude sections have been studied and document changes in salinity, hydrology and sedimentation, deoxygenation, biotic overturning, and migrations, but detailed records from tropical regions are lacking. [...]"

Source: Climate of the Past
Authors: Joost Frieling et al.
DOI: 10.5194/cp-14-39-2018

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Oxygen loss strains marine ecosystems

A new review highlights the impact of declining oxygen levels in the open ocean and coastal waters due to increasing temperatures and nutrient discharge.


"Half of the world’s oxygen originates from the ocean. Yet, worldwide, the amount of open ocean without any oxygen has quadrupled over the past 50 years. Oxygen-minimum zones have expanded by several million square kilometres, increasing by more than 10-fold since 1950.  [...]"

Source: nature Middle East
Author: Lakshini Mendis
DOI: 10.1038/nmiddleeast.2018.2

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Intensification and deepening of the Arabian Sea oxygen minimum zone in response to increase in Indian monsoon wind intensity


"The decline in oxygen supply to the ocean associated with global warming is expected to expand oxygen minimum zones (OMZs). This global trend can be attenuated or amplified by regional processes. In the Arabian Sea, the world's thickest OMZ is highly vulnerable to changes in the Indian monsoon wind. Evidence from paleo-records and future climate projections indicates strong variations of the Indian monsoon wind intensity over climatic timescales. [...]"

Source: Biogeosciences
Authors: Zouhair Lachkar, Marina Lévy, and Shafer Smith
DOI: 10.5194/bg-15-159-2018

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Oceans suffocating as huge dead zones quadruple since 1950, scientists warn

Areas starved of oxygen in open ocean and by coasts have soared in recent decades, risking dire consequences for marine life and humanity


"Ocean dead zones with zero oxygen have quadrupled in size since 1950, scientists have warned, while the number of very low oxygen sites near coasts have multiplied tenfold. Most sea creatures cannot survive in these zones and current trends would lead to mass extinction in the long run, risking dire consequences for the hundreds of millions of people who depend on the sea. [...]"

Source: The Guardian

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