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Earth & Climate

The Ocean’s Dark Secret: How Human Activities are Turning the World’s Waters a Shade Darker

Scientists, who have spent more than a decade examining the impact of artificial light at night on the world’s coasts and oceans, have shown that more than one-fifth of the global ocean — an area spanning more than 75 million sq km — has been the subject of ocean darkening over the past two decades. Ocean darkening occurs when changes in the optical properties of the ocean reduce the depth of its photic zones, home to 90% of all marine life and places where sunlight and moonlight drive ecological interactions.

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The world’s oceans are facing a new challenge: darkening. A recent study published in Global Change Biology reveals that more than one-fifth of the global ocean – an area spanning over 75 million square kilometers – has become darker over the past two decades. This phenomenon, known as ocean darkening, occurs when changes in the optical properties of the ocean reduce the depth of its photic zones, where sunlight and moonlight drive ecological interactions.

Researchers from the University of Plymouth and the Plymouth Marine Laboratory used satellite data and numerical modeling to analyze annual changes in the depth of photic zones across the globe. Their findings show that between 2003 and 2022:

* 21% of the global ocean – including large expanses of coastal regions and open waters – has become darker.
* More than 9% of the ocean, covering an area similar to the continent of Africa, has seen photic zone depths reducing by over 50 meters.
* Around 10% of the ocean has actually become lighter over the past two decades.

The researchers emphasize that while the precise implications of these changes are not yet fully clear, they could have significant effects on marine species and ecosystems. The study’s lead author, Dr. Thomas Davies, Associate Professor of Marine Conservation at the University of Plymouth, warns: “Our findings represent genuine cause for concern.”

Factors contributing to ocean darkening include:

* Changes in nutrient, organic material, and sediment loading near coastal regions due to human activities such as agricultural runoff and increased rainfall.
* Shifts in sea surface temperatures and algal bloom dynamics in open waters.

The consequences of reduced photic zone depth are far-reaching. Marine species that rely on sunlight and moonlight for survival and reproduction will be forced closer to the surface, where they will compete for food and other resources. This could bring about fundamental changes in entire marine ecosystems.

Professor Tim Smyth, Head of Science for Marine Biogeochemistry and Observations at the Plymouth Marine Laboratory, adds: “The ocean is far more dynamic than it is often given credit for… If the photic zone is reducing by around 50m in large swathes of the ocean, animals that need light will be forced closer to the surface where they will have to compete for food and other resources.”

As we continue to explore and understand the complexities of our oceans, it’s essential to acknowledge the impact of human activities on these vital ecosystems. The ocean’s dark secret is a reminder of the urgent need for responsible stewardship and conservation efforts to protect the health and well-being of our planet.

Air Quality

Unlocking the Secrets of Environmental DNA: A Powerful Tool for Wildlife and Human Surveillance

Environmental DNA from the air, captured with simple air filters, can track everything from illegal drugs to the wildlife it was originally designed to study.

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Dublin, a city known for its warm welcome and lively traditional music, has an unsuspecting secret – the air is teeming with DNA from various species. From cannabis to bobcats, even magic mushrooms – at least their DNA – are floating on the breeze. A new study reveals that this phenomenon can be leveraged to track wildlife, viruses, and other substances in unprecedented ways.

David Duffy, Ph.D., a professor of wildlife disease genomics at the University of Florida, has developed innovative methods for deciphering environmental DNA (eDNA). His lab has been studying sea turtle genetics using eDNA from water samples. Expanding on this research, they’ve created tools to study every species – including humans – from DNA captured in environmental samples like air filters.

“What we’re finding is that you can get intact large fragments of DNA from the air,” Duffy said. “That means you can study species without directly having to disturb them.” This approach opens up vast possibilities for tracking all species in an area simultaneously, from microbes and viruses to vertebrates like bobcats and humans.

A proof-of-concept experiment demonstrated that researchers could pick up signs of hundreds of different human pathogens from the Dublin air, including viruses and bacteria. This surveillance method can aid scientists in tracking emerging diseases. Additionally, it can track common allergens, such as peanut or pollen, more precisely than current methods allow.

In another test, Duffy’s lab identified the origin of bobcats and spiders whose DNA was collected from air filters in a Florida forest. This technique allows researchers to track endangered species without having to lay eyes on them or gather scat samples – all while knowing their exact origin is crucial for conservation efforts.

This powerful analysis is paired with impressive speed and efficiency, as demonstrated by the team’s ability to process DNA for every species in as little as a day using compact, affordable equipment, and software hosted in the cloud. This quick turnaround is orders of magnitude faster than was possible just a few years ago, making advanced environmental studies more accessible to scientists worldwide.

However, Duffy and his collaborators have called for ethical guardrails due to the potential for sensitive human genetic data to be identified using these tools.

“It seems like science fiction, but it’s becoming science fact,” Duffy said. “The technology is finally matching the scale of environmental problems.” As researchers continue to explore the capabilities of eDNA, they must also address the challenges and implications of this rapidly developing field.

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Early Climate

First Direct Observation of Trapped Waves that Shook the World in 2023

A new study has finally confirmed the theory that the cause of extraordinary global tremors in September — October 2023 was indeed two mega tsunamis in Greenland that became trapped standing waves. Using a brand-new type of satellite altimetry, the researchers provide the first observations to confirm the existence of these waves whose behavior is entirely unprecedented.

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The article begins by describing an extraordinary global seismic signal that occurred in September 2023. A peculiar pattern of earthquakes was observed every 90 seconds over nine days, only to be repeated a month later. Initially, two scientific studies proposed that these anomalies were caused by massive tsunamis triggered in a remote East Greenland fjord due to the warming of an unnamed glacier. The resulting waves became trapped in the fjord system, creating standing waves (seiches) that undulated back and forth.

However, despite extensive research, no direct observations of these seiches existed until now. Not even a Danish military vessel visiting the fjord three days into the first seismic event was able to detect the wave responsible for the mystery signals.

A new study from researchers at the University of Oxford has employed cutting-edge analysis techniques on satellite altimetry data from the Surface Water Ocean Topography (SWOT) mission, launched in December 2022. The SWOT satellite measures ocean and surface water levels with unprecedented accuracy along a swath 30 miles wide using its Ka-band Radar Interferometer (KaRIn) instrument.

Utilizing KaRIn data, the researchers created elevation maps of the Greenland Fjord at various time points following the tsunamis. These maps showed clear, cross-channel slopes with height differences of up to two meters. Crucially, the slopes in these maps occurred in opposite directions, indicating that water moved backwards and forwards across the channel.

To confirm their theory, the researchers linked these observations to small movements of the Earth’s crust measured thousands of kilometers away, reconstructing weather and tidal conditions to rule out alternative explanations.

Lead author Thomas Monahan stated: “Climate change is giving rise to new, unseen extremes. These extremes are changing the fastest in remote areas, such as the Arctic, where our ability to measure them using physical sensors is limited. This study shows how we can leverage the next generation of satellite earth observation technologies to study these processes.”

Co-author Professor Thomas Adcock added: “This study is an example of how the next generation of satellite data can resolve phenomena that has remained a mystery in the past. We will be able to get new insights into ocean extremes such as tsunamis, storm surges, and freak waves. However, to get the most out of these data we will need to innovate and use both machine learning and our knowledge of ocean physics to interpret our new results.”

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Ancient DNA

The Tipping Point: Scientists Warn of West Antarctic Ice Sheet Collapse and its Devastating Consequences

Collapse of the West Antarctic Ice Sheet could be triggered with very little ocean warming above present-day, leading to a devastating four meters of global sea level rise to play out over hundreds of years according to a new study. However, the authors emphasize that immediate actions to reduce emissions could still avoid a catastrophic outcome.

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The fate of the West Antarctic Ice Sheet (WAIS) hangs precariously in the balance, with scientists warning that the next few years will be crucial in determining its future. A recent study published in Communications Earth & Environment has shed light on the alarming consequences of WAIS collapse, which could trigger a devastating four meters of global sea level rise over hundreds of years.

The researchers from the Potsdam Institute for Climate Impact Research (PIK), NORCE, and Northumbria University in the UK conducted extensive model simulations spanning 800,000 years to understand how the vast Antarctic Ice Sheet has responded to Earth’s climate fluctuations. Their findings revealed two stable states: one with WAIS intact, which is our current state, and another where the ice sheet has collapsed.

The primary driver of this collapse is rising ocean temperatures around Antarctica, which are mostly supplied by the ocean rather than the atmosphere. Once WAIS tips into the collapsed state, it would take several thousands of years for temperatures to drop back to pre-industrial conditions, reversing the damage.

“We have two stable states: one with WAIS intact and another where it has collapsed,” said lead author David Chandler from NORCE. “Once tipping has been triggered, it’s self-sustaining and seems very unlikely to be stopped before contributing to about four meters of sea-level rise. And this would be practically irreversible.”

The consequences of WAIS collapse would be catastrophic, with four meters of sea level rise projected to displace millions of people worldwide and wreak havoc on coastal communities.

However, there is still hope for a better outcome. Immediate actions to reduce emissions could avoid a catastrophic outcome, giving us a narrow window to act before it’s too late.

“It takes tens of thousands of years for an ice sheet to grow, but just decades to destabilise it by burning fossil fuels,” said co-author Julius Garbe from PIK. “Now we only have a narrow window to act.”

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