readx;? About 2.59 million years ago, the Earth entered the Quaternary Ice Age. Pen ~ Fun ~ Ge www.biquge.info Until the middle of the 20th century, most scientists believed that the climate of the Ice Age was persistently cold. But in fact, there were relatively warm periods during the ice age.

Scientist Milankovic discovered that the pattern of climate change in the Quaternary was glacial-interglacial alternation, which is called a cycle. It is inferred that the formation of the cycle is related to the change of the Earth's orbital elements. The cycle of the cycle (Milankovic cycle) is usually measured in 10,000 years, but it is not stable.

Recognizing the instability of glacial climate is an important achievement in paleoclimate research.

In the past 700,000 years, a 100,000-year cycle has been a cycle. In each glacial-interglacial cycle of about 100,000 years, the warm period is relatively short, generally about 1-20,000 years. And more time is in the cooling process. But the drop in temperature is not a straight line, but consists of a series of fluctuations.

The most recent cycle begins in the year, when the Earth's climate is comparable to that of modern times, until the year reaches its coldest point (known as the last glacial maximum).

years, after the last glacial maximum, there is a glacial period. The Earth is gradually "recovering" from the Ice Age, and although the high latitudes are still covered with large ice sheets, the Earth's climate is slowly warming at that time. The Laurentai Ice Sheet in North America and the Scandinavian Ice Sheet in Northern Europe began to disintegrate.

years, the climate has warmed up to a near-modern situation. At this time, a comet explodes before it crashes into the Earth, and the debris produced by the exploding comet may fall into the Earth's ice sheet, causing the ice sheet to melt a large area. The massive melting of the North American ice sheet has changed the southward flow of freshwater into the Gulf of Mexico, which in turn has caused a large amount of freshwater to flow northward into the North Atlantic, resulting in lighter surface water (because of less salinity) and less sinking seawater, thus weakening the "thermohaline circulation". The northward current from the sea surface also weakened, reducing the heat transmitted to the north, reducing the ocean's function of regulating the atmosphere at high latitudes, and the temperature dropped rapidly.

This intense climate fluctuation is known as the "New Fairy Wood" event. Centered on the northern part of the North Atlantic, the climate is rapidly cooling.

The earth is up to this time). Falling back into ice and snow and plummeting temperatures in much of the planet's northern hemisphere, destroying Paleolithic civilization and causing the extinction of large prehistoric animals such as mammoths. This period is known as the Neo-Fairy Wood Period.

During this period, the average temperature in southern England dropped to -8C and even lower to -20C in winter, severely disrupting the development of early human civilization that was taking shape in Europe and Asia at the time.

The "New Fairy Wood" event lasts for about a thousand years. The temperature drops rapidly at the beginning and rises rapidly at the end, and the time for cooling and warming is only a few decades or even ten years, so it is called a sudden climate change. The amplitude of temperature change is three-quarters of that of the glacial-interglacial cycle. This is the first abrupt change in climate after the last glacial maximum, which is in the stage of temperature rise. It is due to the closure of thermohaline circulation in the global oceans.

The "new" of "new fairy wood" refers to the most recent cold event after the last glacial maximum, after which the climate warmed and entered the warm Holocene.

The new fairy wood event is a typical unconventional event of sudden cooling during the continuous warming of the glacial period after the last glacial maximum, which is of great significance for the study of rapid abrupt change events and short-period phenomena of paleoclimate and paleoenvironment, and for the reasonable assessment of the current climate and environmental conditions and the prediction of climate change. It is a global event, and sedimentary records of the "New Fairy Wood" event are also commonly found in the shelf waters of eastern China. Since China's eastern shelf is located between Eurasia and the Pacific Ocean, it is strongly influenced by the monsoon and therefore has a unique response.

I asked the sages, "What is the 'thermohaline circulation' and how can it have such a big impact?"

"In the west of the European continent, in the northeast region of the Atlantic Ocean, there is an ocean current that flows from southwest to northeast - the North Atlantic thermohaline circulation, which brings warm and humid air and abundant rainfall to Europe, so that the winter in Northern Europe is not so cold, and this warm current also affects the northeastern part of North America similarly, without it, the winter in Northern Europe will become unusually cold, and not only that, but the temperature in a large part of the Northern Hemisphere will be affected.

The North Atlantic thermohaline circulation is like a conveyor belt that transports heat from the equator to the North Atlantic: surface warm water from the equator is constantly moving northward by the Gulf Stream along the coast, releasing heat from the seawater along the way, causing net heat to be transported northward.

The gradual cooling of the seawater, which releases heat, increases the salinity of the seawater due to constant evaporation. As a result, the further north the sea becomes, the colder and thinner it becomes, and therefore heavier, and finally sinks into the deep sea in a fixed sinking zone at high latitudes in the North Atlantic, and this part of the originally warm equatorial water becomes cold and salty deep North Atlantic water.

The cold water mass that forms in the North Atlantic flows southward in the form of boundary currents at depth, then circles the Antarctic jet stream around the Antarctic, and partially mixes with the Antarctic bottom water that forms in the Weddell Sea, and flows to the Pacific and Indian Oceans, where it climbs through the thermocline to reach the upper ocean.

After that, the thermohaline circulation turns around and moves southward with deep water, along the South Atlantic, Antarctica into the Indian Ocean, and finally back to the equator, completing the so-called "circulation".

From the above situation, it can be seen that the thermohaline circulation is mainly driven by the temperature and salt density of seawater, and is a global ocean current circulation system. The warm currents on the surface of the sea are driven by the winds affected by temperature, and the cold currents on the seabed are driven by the difference in the density of the sea affected by salinity.

Surface winds play a negligible role in the circulation of seawater at depths below 100 meters, while changes in temperature and salinity are enough to make a difference in the density of seawater.

The difference in the density of seawater causes a density gradient in seawater, which leads to the formation of ocean currents. The currents produced in this way flow at very slow speeds (only a few kilometers per year) can only be detected by special means, i.e. by representing the temperature, salinity and oxygen content of water masses at different depths on a map.

A thermohaline cycle takes about 1,600 years, during which ocean currents transport not only energy (temperature/heat) but also the earth's solid and gaseous resources, but the thermohaline circulation has attracted the most attention for its function as a global constant temperature.

The importance of the thermohaline circulation lies in the fact that, together with the well-known atmospheric circulation, circulation and polar circulation, it constitutes a meridional circulation system that is essential for maintaining the energy balance of the global climate system.

For the global climate system, there is a radiation surplus in the tropics and a radiation deficit in the polar regions, and in order to maintain the energy balance of the whole system, there must be a strong meridional energy transport between low and high latitudes. Previously, it was thought that this transport was mainly achieved by atmospheric transport. In the Northern Hemisphere, it transports heat from low latitudes to high latitudes, and around 50 degrees north latitude (where the western boundary of the ocean is strongest), it transports a large amount of heat to the atmosphere through strong air-sea heat exchange, which then transports energy to higher latitudes. Changes in the intensity of ocean meridional heat transport will have an important impact on the global climate.

In the current climate, the Atlantic Ocean is the main heat transporter to high latitudes. The transition of cold and warm water from the North Atlantic Gulf Current at high latitudes in the North Atlantic releases a large amount of heat into the atmosphere. It is estimated that at 24 degrees north latitude, the Atlantic Ocean has a total of 1.2 pw of heat transport, while the total meridional heat transport of all oceans at that latitude is 2.0 pw and the total heat transport of the atmosphere is 3.0 pw. In the North Atlantic, heat transport to high latitudes and the release of heat in winter can replenish 25% of annual insolation, and the prevailing westerly winds carry this heat to the adjacent continents, keeping the Nordic climate warm.

Therefore, any change in thermohaline circulation activity will have a considerable impact on the regional and global climate. And the new fairy wood event is precisely because of a sudden increase in heat that causes the thermohaline circulation in the global ocean to shut down.

In January, the middle and lower reaches of the Yangtze River and the southern part of the Yangtze River in China cooled sharply, also because global warming affected the movement of the thermohaline circulation.

The next chapter deals with the prehistoric Flood.