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Planet Earth

River deltas are ‘drowning’, threatening hundreds of millions of people

River deltas are 'drowning', threatening hundreds of millions of people 90

The world’s river deltas take up less than 0.5% of the global land area, but they are home to hundreds of millions of people. Many live in major fast-growing cities such as Kolkata in the Ganges delta, Bangkok in the Chao Phraya delta, or Shanghai, one of dozens of large cities in the Yangtze delta region.

With fertile soils and easy access to the coast, deltas are critical hotspots of food production. Vietnam’s Mekong delta alone supplies almost 20% of the world’s rice. They also host unique ecosystems such as the Sundarbans in Bangladesh and India, the largest mangrove forest in the world.

But many of the world’s deltas are now facing an existential crisis. Sea levels are rising as a result of climate change, while deltas are themselves sinking, and together this means the relative sea level is rising extra fast.

Deltas are built from sediments that are carried downstream by rivers and eventually deposited where the river meets the sea. As these sediments compact under their own weight, deltas naturally sink. Where left undisturbed, the supply of new river sediment can compensate for the subsidence and help to maintain the delta surface above sea level.

But deltas are now subsiding much faster than they would do naturally. That’s thanks to groundwater being pumped (or “mined”) from aquifers underneath them and used to irrigate crops and provide water for rapidly growing cities.

In these circumstances, only the continued deposition of sediment on deltas can keep them from “drowning”. We therefore wanted to find out whether supplies of river sediments would be affected by future environmental changes.

To address this question, we used a computer model to project changes in the flows of sediment to almost 50 major deltas worldwide. We used the model to explore the impact of various environmental changes, including climate change, population growth, increases in wealth and the construction of dams. Our results are published in the journal Environmental Research Letters.

River deltas are 'drowning', threatening hundreds of millions of people 91
Rice farmers in the Mekong Delta, Vietnam.
Phuong D. Nguyen / shutterstock

We found that most of the world’s major deltas will receive less river sediment by the end of the century, regardless of the environmental change scenario. On average, we projected a 38% decrease. Our results suggest that many deltas – already significantly stressed – will become sediment starved, further compounding the risks of rising relative sea levels.

Some of the most severe reductions will be found in major Asian deltas such as the Ganges (81% less sediment) and the Mekong (77%). This is particularly concerning because these deltas are among the largest and most densely populated in the world.

We found that climate change will generally drive a small increase in the flows of sediments as, among other factors, warmer temperatures lead to increased precipitation and more soil is washed into rivers. But in many deltas this modest uptick will be more than offset by dams (which trap river sediments) and improved soil conservation practices as societies become wealthier. The Aswan Dam on the River Nile in Egypt or the Hoover Dam on the Colorado River in the US are among the dams that have already starved their downstream deltas of sediment.

River deltas are 'drowning', threatening hundreds of millions of people 92
Bad news for a river delta.
Tupungato / shutterstock

Better management of river sediment is vital to improve the outlook for the world’s deltas. International cooperation will be essential in deltas such as the Mekong and Ganges which are supplied by large rivers that drain many countries. For dams specifically, comprehensive environmental risk assessments that fully cost the consequences for downstream regions are required so that plans can be changed or scrapped. For those dams that are to be built in the coming decades, their design must accommodate transport of sediment downstream.

For authorities within deltas, faced with managing a dwindling supply of river sediment, new approaches are needed to better manage this precious declining resource. Flood embankments prevent sediment reaching delta plains and may need to be breached, as is being explored in the Ganges delta. Additionally, the removal of sand from rivers for construction materials, which is pervasive in many deltas around the world, must be better managed.

Ultimately, difficult decisions need to be made about development priorities between countries upstream of deltas and those including the deltas themselves, and there will be trade-offs to be made between hydropower, agricultural practices and delta sustainability.

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Planet Earth

A new ice age: why it will begin in 2030

A new ice age: why it will begin in 2030 93

The sun is both the main source of life and the greatest threat to it. On the one hand, the star converts four million tons of matter every second into energy, which is the main source of light and heat. On the other hand, it is a source of powerful emissions that cause strong disturbances on Earth and near-earth space.

Magnetic storms and auroras are nothing more than a consequence of anomalies occurring on the luminary. Fortunately, today scientists have learned to predict these manifestations, and humanity as a whole already knows how to neutralize their negative impact.

At the same time, some of the processes occurring on the Sun cause concern among specialists. Experts around the world state an unprecedented decrease in solar activity and predict the approach of a new ice age – the fifth in the last 400 thousand years.

What are solar cycles

A lot of what happens on the Sun and, as a consequence, in the entire solar system, depends on the state of the magnetic field of the star. Its amplitude and spatial configuration are constantly changing, which, together with the formation and decay of other strong fields in the atmosphere, leads to the transformation of the wave radiation of a celestial object and the intensity of fluxes of corpuscles – particles of solar gas in a plasma state. The number of spots – relatively cold regions in its photosphere – on the surface of the Sun also changes.

Long-term studies have shown that the activity of a star associated with the appearance of spots has a cyclic structure. Scientists estimate the duration of the cycles in different ways – up to six thousand years, but most often they distinguish three periods: 11-year, 90-year and 300-400-year cycles.

The shortest of them is more pronounced and is associated with changes in the direction of the main component of the magnetic field of the star. The period is characterized by a rather rapid – for about four years – increase in the number of sunspots and its subsequent decrease, which takes about seven years. At the same time, the assessment of the cycle duration of 11 years is an average, in some cases it can last from nine to 14 years.

A new ice age: why it will begin in 2030 94

The 90-year variation is associated with a 25-50 percent periodic decrease in the number of sunspots in 11-year cycles. 300-400-year intervals are completely characterized by the appearance of long, up to several tens of years, intervals when very few sunspots appear on the Sun. The last such period was recorded quite recently – in 2017. And the most famous – the Maunder minimum – lasted from about 1645 to 1715 and coincided in time with the coldest phase of climate cooling – the Little Ice Age.

How the Sun’s cycling affects the Earth

Scientists have long formed certain ideas that the activity of a star affects the climate – both space and terrestrial. When there are many sunspots on the Sun, the probability of reconnection of magnetic lines of different polarities increases. The visible result of this process is flares, characterized by explosive energy release. This burst of radiation, reaching the Earth, causes strong disturbances in its magnetic field, disrupts satellites and increases the likelihood of aurora borealis in low geographic latitudes.

The planet’s ionosphere is also subject to fluctuations in solar activity, which manifests itself in a change in the propagation of short radio waves. It also affects the chemical processes in the Earth’s atmosphere, since it affects the intensity of galactic cosmic ray fluxes.

Moreover, it is now known that a change in the total value of the electromagnetic radiation of the Sun by only one percent can entail a noticeable change in the distribution of temperature and air currents on the Earth. An increase in the flow of particles leads to the fact that warm currents from the south rush with even greater energy to the northern latitudes, and the cold ones, carrying the Arctic air, penetrate deeper to the south.

Should we wait for a new ice age?

Each solar minimum traditionally raises concerns about the possible onset of the next global cooling, akin to that observed at the turn of the 17th and 18th centuries. During the Little Ice Age, global average temperatures dropped by one to two degrees Celsius, snow lay on some of the plains all year round, and Greenland was covered with glaciers. Moreover, the waters of the Thames and Danube rivers were frozen, and the Moscow River was covered with ice every six months.

However, for such cataclysms, a simple decrease in solar activity is not enough; a significant deviation is needed. A sharp decline, according to an international group of scientists, may occur in 2030-2040. This conclusion was made by experts after analyzing solar radiation during the 1982-2002 cycles. The data they obtained made it possible to derive analytical formulas that can be used to predict the behavior of a star in the period from 1200 to 3200.

“If the existing theories about the influence of solar activity on the climate are correct, then this minimum will lead to a significant cooling, similar to that which was during the Maunder minimum. In view of the fact that our future minimum will last three solar cycles – about 30 years, perhaps the decrease in temperature will not be as deep as in the Maunder minimum. But this will need to be studied in more detail, ”the MSU website writes.

Scientists see a lot of other “bells” that foreshadow a sharp decline in solar activity. For example, Matthew Penn, an astronomer at the National Solar Observatory in Tucson, Arizona, told Deutsche Welle that sunspots are not observed at all if the magnetic field of the star falls below 1500 gauss. Moreover, in the penultimate cycle, local fields weakened by about 50 gauss per year.

“If we extrapolate this trend, then by 2021 they will become too weak and will not be able to resist convection. The spots on the Sun will disappear,” he stated.

The director of the National Solar Observatory in Tucson, Frank Hill, even notes that in the new millennium, a malfunction was recorded in the formation of a plasma flow, the movement of which to the equator of the star and becomes the cause of the appearance of spots.

At the same time, the connection between disruptions in solar activity and the beginning of ice ages has not yet been reliably established, and so far experts are very cautious about this.

“My position is this: we do not yet have scientific data that could confirm or deny such a relationship,” Frank Hill emphasized. – Of course, a long minimum of solar activity, in principle, will have some effect on everything – both on space exploration and on the Earth’s climate. But I still want to emphasize: we are predicting changes in the solar cycle, and not at all the onset of a new Little Ice Age.”

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Planet Earth

A strange phenomenon in the Arctic, the cause of which is unknown

A strange phenomenon in the Arctic, the cause of which is unknown 95

In 2018, a plane flying over the Greenland glaciers noticed strange holes in the ice. NASA scientists cannot yet find the reason for their appearance.

The Arctic is a mysterious place, and as the Earth’s climate changes, it changes faster than scientists can record. So, according to NASA, strange holes began to appear in the ice, and so far no one can understand what causes them. 

The photo was taken by John Sonntag, a scientist working for NASA’s IceBridge operation, an ambitious mission to capture as much detail as possible of the North and South Poles in hopes of figuring out what is happening right now in these remote parts of the planet.

Unfortunately, this photo raises more questions than answers, at least for now. But even though scientists from IceBridge do not have an exact answer to what these holes are, they make assumptions. / These holes may be caused by ice melting due to the water warming under the ice, or they may be air pockets caused by whales or seals. However, for the latter variant the holes are somehow too big. 

NASA even asked its readers on the Internet for advice on what it might be. There were many assumptions, but it is not yet possible to say exactly why these holes formed.

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Planet Earth

Rich people from all over the world are buying submarines

Rich people from all over the world are buying submarines 96
Photo: uboatworx / YouTube

The wealthy around the world will spend millions of dollars on private submarines, following Russian billionaire Roman Abramovich, The Times reports.

According to the publication, in the period from 2019 to 2020, it was about the sale of 15 to 25 submarines, however, this number is expected to double in 2021. According to representatives of the three leading submarine manufacturing companies, next year the market will be estimated at 75 million pounds.

Among the first buyers of deep-sea vessels were the owner of Chelsea Football Club Roman Abramovich, the late Microsoft founder Paul Allen and the Emir of Abu Dhabi, Sheikh Khalifa Al Nahyan.

Roy Heijdra of the Dutch company U-Boat Worx noted that wealthy people increasingly want their yachts to be specially equipped for exploration, not just luxury holidays. According to him, ten vessels were sold in 2020 worth up to £ 2.2 million each. Among them was the Nemo model, which is estimated at 875 thousand pounds, has a height of 2.8 meters and can dive to a depth of more than 90 meters with two people on board.

In turn, the executive director of the Florida company Triton, Bruce Jones, said that compared with the previous year sales of submarines this year rose by almost a third, despite the pandemic coronavirus. At the moment, he has about five orders that need to be completed by the beginning of 2021.

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