Migration weather

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Climate change leads to changes in wind patterns.

Dunes will deform or migrate in new directions.

Sand dunes cross the desert as waves cross the ocean. Wind is a driving force for them to crawl, and when the direction of the driving force changes, sand dunes will also be reshaped. A few days ago, two scientists from King's College London studied how changes in wind patterns caused by climate change reshape sand dunes around the world. The results show that by the end of this century, there will be more sand dune migration in tropical and equatorial regions compared with other regions. This study has important reference significance for future urban planning and farmland management.

It is pointed out that by the end of this century, the potential of sand flow in several sand seas in the northern Sahara desert will increase. By 2 100, parts of Australia will see higher quicksand in some directions. On the contrary, the quicksand potential of dunes in the Great Plains of North America will be reduced.

In Australia's Great Victoria Desert, historically, winds came from many directions, so the terrain formed linear sand dunes. At present, these dunes are covered by vegetation and will not migrate. However, climate change may change the wind direction, leading to the formation of crescent dunes. At the same time, the prediction of soil water deficit shows that with the disappearance of vegetation, drought in this area may aggravate the movement of sand dunes. In the southern hemisphere, if climate change forces the wind direction to change, farmland in southern Egypt may be at risk: a series of crescent dunes migrating south may turn eastward to irrigated fields. By the end of this century, the local wind direction will rotate nearly 90 degrees counterclockwise.

How does climate change lead to changes in wind patterns? Usually, the temperature difference between the poles and the equator determines the global air circulation, but with the warming of the poles, the circulation between the poles and the equator weakens. At the same time, the warmer air in the atmosphere gives it more energy and strengthens the wind from other directions.

Extreme drought seen from space

How to affect carbon emissions

With global warming, the frequency of extreme weather has increased significantly. Recently, a new study provides an important case for evaluating the impact of extreme weather on regional carbon balance by using new remote sensing observation data. Researchers from California Institute of Technology, Goddard Space Flight Center of NASA and other units have quantified the losses caused by drought and forest fires in southeastern Australia from 20 19 to 2020 through satellite observation.

It is pointed out that in the fire season, forest fires lead to a large amount of carbon dioxide emissions, while drought and fire reduce the carbon absorption of ecosystems, so Australia's annual carbon emissions have nearly doubled.

In addition, the researchers also proved that extreme drought has an important impact on carbon flux in unburned areas. The abnormal net ecosystem exchange caused by drought and fire reduces the carbon absorption in the growing season by 19TgC~52TgC, and these excess carbon are usually absorbed by the atmosphere.

In the next few years, it is expected that these ecosystems will recover the lost carbon storage to a great extent, but the recovery speed may be strongly affected by climate change, because high temperature and drought events driven by climate change may increase the frequency of fire events and the recovery time of ecosystems.

Phenological changes may

Lagging behind climate change

Recently, a new study shows that there is a general mismatch between surface phenology and climate, which is more obvious in the landscape dominated by human beings, indicating that there is a relationship between human activities and the unsynchronized phenology and climate change.

The researchers compared the speed of these changes with the climate data and phenological indicators observed in the field and remotely, and found many examples that the speed of phenology and climate change was not synchronized. Among them, the biggest disharmony appears in the landscape dominated by human beings, which is related to population density and intensive agricultural management system. This may be caused by the mismatch between crop growth and regional climate due to insufficient crop variation.

Although this result shows that the vulnerability of agriculture is increasing and the opportunity to increase yield may be lost, it is also expected to create opportunities for the cultivation of new varieties.

The oldest magnetic pole

Hand it over or be found.

For a long time, the earth's magnetic field has been like an invisible "shield" to protect us from cosmic radiation. At the same time, close to the earth's surface, they move back and forth from the earth's crust to the inside, triggering chemical reactions, which may help stabilize the global temperature for a long time, just like geological thermostats.

Recently, at the autumn meeting of American Geophysical Society 202 1, a new study may reveal the oldest known evidence of plate tectonics and a stable dipole magnetic field similar to that of the earth today. If confirmed, this discovery will support the view that the early earth already had many of the same physical characteristics as today and has nourished life on the earth for billions of years. This study fully confirmed the maturity of early geodynamics.

Researchers collected rocks 3.25 billion years ago from a crater in Australia, and analyzed the magnetic characteristics of iron-rich particles in the rocks, which were consistent with the direction of the earth's magnetic field when rocks formed during submarine eruption and then cooled down. In the study of magnetic signals, it is found that the mineralization compasses of some rocks point in the same direction, but the older rocks below point in the opposite direction. Therefore, people realize that this may be the phenomenon of the earth's magnetic field flipping.