Glacial ablation

Ice consumption caused by melting and evaporation of ice

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Glacier ablation refers to the phenomenon of glacier consumption caused by ice melting and evaporation Material consumption The main way. Direct solar radiation and Near stratum atmospheric turbulence Exchange is the main heat source that causes glacier ablation Aspect as well as weather condition It also affects ablation. Ablation mainly occurs in summer and daytime, so it has daily, seasonal and annual changes. Its quantity depends on the latitude (temperature) of the glacier and the pollution degree of the ice surface. The ways of glacier melting are Ice melting 、 Intraglacial ablation and Subglacial ablation , mainly ice surface ablation. Studying glacier ablation is an important way to analyze and predict the advance and retreat of glaciers Mountain roads And bridge design The basis of is to understand River recharge And the basis for the development and utilization of glacier resources.

2023, South Pole Glacier melting and other climate change indicators set new records.^[2]

Chinese name: Glacial ablation
Phenomenon: Ice consumption caused by melting and evaporation of ice

Mode: Ice surface ablation, intra ice ablation and sub ice ablation
Research: An important way to analyze and predict the advance and retreat of glaciers

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brief introduction

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Glacial ablation

The general term for the destruction and construction of surface rocks and topography caused by glacier activities. include Glaciation , transport function and Sedimentation 。 Glaciation In the polar regions High latitude And high mountains Cold region Occupy a prominent position.

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Basic Introduction

Glacial ablation

Glacier activity destroys the rock and terrain that make up the ice bed, also known as Gouging 。 Ice erosion Including excavation and abrasion Action mode , and almost none Dissolution 。 The ice body near the ice bed is squeezed, the melting point is reduced and melted into water, which seeps into the cracks or pores of the underlying ice bed, and the water body is frozen due to the pressure reduction. With the repeated melting and freezing of ice body and melt water, their volume shrinks and expands repeatedly, resulting in the disintegration of bedrock or soil mass that forms the ice bed. The disintegrated debris (including the original debris) will be refrozen, incorporated into the glacier, and migrated with the glacier. In the future, fresh ice beds will continue to suffer from the above actions repeatedly, deepening and widening, which is called digging erosion. Developed in precipitation Abundant Marine climate Lower Temperate glacier （ Marine glacier ）And developed in low precipitation Continental climate The cold glacier below（ Continental glacier ）The intensity of excavation and erosion is obviously different. The temperature of the former is close to the melting point, with abundant meltwater at the bottom and especially strong tunneling erosion; The temperature of the latter is lower than the melting point, and the molten water at the bottom is poor, so the excavation and erosion are extremely weak.

In addition, during the movement, the glacier is strong due to its own Extrusion force , carried debris The grinding of the ice bed makes the bedrock bed surface and rock debris subject to abrasion, which is called abrasion. Because the excavation and erosion of the temperate glacier is stronger than that of the cold glacier, it carries more rock debris at its bottom. In addition, it can slide along the ice bed, so the Abrasion Stronger than cold glaciers. Glaciation A series of special landforms can be shaped. stay Mountain glacier The most common Glacial landform yes: Cross section U-shaped Glacial valley , like Armchair Of Cirque , pyramidal Angular peak , the ridge is as thin as a blade Blade ridge , smooth and flat with multiple sets of nicks Ice skating noodles , and the shape of a sheep's back lying on the ground Sheep backed stone Etc.

Glaciation

Glacial transport In the process of movement, the glacier transfers the debris it carries to other places. The material transported by glaciers is called ice transport. The glacier contains a large number of Grain size fraction In addition to the debris from both sides Valley slope By frost weathering and Slope gravity Debris produced. The amount of debris in warm glaciers is much higher than that in cold glaciers. Even in cold glaciers, the debris content can reach 60%. These debris are mainly distributed at the bottom and both sides of the glacier, and there are also debris distributed inside and on the surface.

Glacier has great transport capacity, which can transport large particles with a particle size of 10-20 meters Rock block move. The rock block with particle size greater than 1m is called Glacial boulder 。 Glacial Transport action It includes two modes of carrying and pushing. Glacial movement The debris inside and on the surface of the glacier will migrate with the glacier, just like Conveyor belt Conveying objects is called carrying. Carrying is the main mode of glacier transport. The movement route of glacier load is determined by Glacial ice Particle path of particle Determined. Because the ice bed is uneven Inclined plane The movement track of glacial ice particles changes with the change of ice bed morphology. At the protruding part of the ice bed, the ice body is subject to tensile stress, and the overlying ice layer and the underlying ice layer slide downward along the inclined interface between them; In the depression of the bed surface, the ice layer is subject to compressive stress, and the overlying ice layer thrusts upward against the underlying ice layer along the inclined interface between them. Therefore, debris at the bottom of the glacier can also rise to the ice surface. In addition, the movement track of glacial ice particles can make lateral scattering on the plane, Scattering angle Generally 2 °～ 10 °, up to 20 °～ 60 °. Pushing means that the front end of the glacier pushes the debris on the ground in the front end of the glacier forward with a huge thrust, which only occurs when the front end of the glacier moves forward. Since glaciers are solid materials, ice transport relative position There are few changes during the transportation, so the glacier transportation does not have sorting phenomenon according to size and specific gravity.

glacial deposit 　

Directly accumulated by glaciers sediment be called Moraine , with invisible bedding , mixed debris size Roundness Poor characteristics. Moraines often form a series of embankment landforms. The moraine (dike) deposited on the valley slopes on both sides of the glacier is called Lateral moraine (embankment). The moraines that make up the side moraines are mainly produced by melting and falling. In some areas, there are multiple side moraines (embankments) at different heights of valley slopes, reflecting that they are either the same Glaciation The products of different melting stages or different ice ages. Deposited in glacier tongue Front moraine (embankment) scale Terminal moraine (Embankment), also known as front moraine (embankment) or tail moraine (embankment). It is deposited under the condition that the glacier is in a period of temporary stability, and the supply and ablation of the front end of the glacier reach a balance. There are many terminal moraines (levees) in some areas, which also reflects that they can be products of the same glacial period or different glacial periods. The position and size of the terminal moraine (dike) can indicate the position and duration of the stagnation of the front end of the glacier. The end of lateral moraine (levee) is often connected with a terminal moraine (levee), which proves that they are the products of the same glacial melting stage. In addition, new terminal moraines may be formed in the process of advancing the front end of the glacier, that is, the products of advancing accumulation cover the old terminal moraines; It may also destroy the old terminal moraine. Moraine scale deposited at the bottom of ice bed Bottom moraine (also known as Lower moraine ）。 It is produced by stop accumulation. After the glacier melts, the moraine originally distributed on the surface and inside of the glacier falls onto the originally formed bottom moraine Base moraine 。 ice water Sedimentation Deposition caused by glacial melt water (ice water). There are ice streams on the surface, bottom and both sides of the glacier. When the glacier is in the retreat stage, the ice water is more developed. Ice water deposit Divided into two categories: ① Glacial contact deposit (also known as ice boundary deposits), refers to the coexistence and close contact of ice water and glaciers in or near the glacier area, Ice water sediment A kind of ice water deposit mixed with and overlapping with moraine. This kind of sediment is also often affected by Ice flow Stir or collapse deformation occurs. Glacial contact sediments often form mound shaped mound mound, platform shaped mound terrace and crater shaped Pot cave , levee shaped Serpentine hill And other landforms. ② Preglacial deposition is the deposition of ice water on the periphery of the glacier after the ice water flows out of the glacier. Including ice water Fluvial deposit and Glacial lake Sedimentation. Ice water river deposits often form fan shaped bodies composed of sand and gravel, called Ice water fan 。 Several ice water fans combine to form a wavy sloping plain, called ice water Alluvial plain (Also called Outwash plain ）。 Glacial lacustrine deposit include Delta deposit , lakeside sedimentation and lake bottom sedimentation. The bottom deposits of glacial lakes are typical of glacial lake deposits. It has clear Prosodic stratification , light colored coarse grains (fine sand Silty sand ）Layer and dark fine grains deposited in winter（ Loam , clay) layer Interbedding Composition, usually called Tattoo mud Or monsoon mud.

Glacier Benefits

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Main impacts

⑴ The earth is a planet with water, and at the same time, it has a suitable temperature. Water can circulate between liquid, gas and solid. Solid water mainly appears on the earth in the form of glaciers. Glaciers and Earth environment The changes of climate change have a close relationship, affecting the climate and the existence of life.

Source of rivers

⑵ Most of the fresh water on the earth is preserved in the form of ice on the north and south poles and some high altitude mountains, which are solid reservoirs on the earth. The operation of such reservoirs is subject to Earth climate change It also affects the surrounding environment in turn. And developed in Mid latitude The mountain glaciers in the region are also like water towers, feeding many large rivers. Glaciers are the source of rivers in a sense.

Ice core

⑶ Today, the global climate is constantly warming, and human beings urgently need to understand the laws of the earth's climate change for a long time. As a solid reservoir, the ice layer with a thickness of tens or even thousands of meters has recorded long-term climate change. Through the study of ice cores, humans can accurately understand the Climate information 。 Ice cores are called pointers to record climate change.

Current situation

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The total area of glaciers in the world is about 15 million square kilometre , about 60000 square kilometers in China human activity It is closely related, and its advance and retreat changes are more closely related to the human beings living around the mountains.

Since the 1980s, global warming The trend is accelerating, and the melting of glaciers is also accelerating. According to the observation data, there are nearly 50000 glaciers in China, 80% of which are retreating. Scientists predict that some glaciers are small Glacial retreat It is expected to disappear in a decade or decades.

On March 19, 2024, the World Meteorological Organization released the Global Climate Report 2023, which shows that in 2023, The Antarctic sea ice area is a record low, and the maximum sea ice area at the end of winter is 1 million square kilometers less than the previous record low.^[2]

significance

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Significant impact

Glacier changes Sea-level fluctuation Has an important impact. According to the latest assessment report of the International Intergovernmental Panel on Climate Change (ipcc) last Glacial Since the peak period (about 20000 years ago), the global sea level has risen by 120 meters on average, mainly because North America and eurasia The disappearance of the ice sheet and the melting of other glaciers have caused a large number of water bodies on land to transfer into the sea. Twentieth Century Mountain glacier and Ice cap The average annual sea-level rise is 0.2mm~0.4mm due to the ablation of greenland ice sheet The sea level will rise by 0 mm~0.1 mm every year, antarctic The ice cover is - 0.2 mm~0 mm per year (actually does not raise the sea level). See right, although mountain glaciers and ice caps Ice reserve Very small, but due to strong ablation, the impact on sea level rise is greater than that of polar ice sheet. along with global warming , not only the melting of mountain glaciers and ice caps, but also the melting of polar ice sheets. According to ipcc estimates, the ablation of mountain glaciers and ice caps alone will raise sea level by 0.01 meters to 0.23 meters in the 21st century. It is worth noting that if the climate continues to warm, in addition to the increase of glacier melting, the increase of internal temperature of glaciers will lead to the acceleration of ice flow, and even the disintegration of glaciers. The danger to the west Antarctic ice sheet It is especially prominent because there are some islands rather than contiguous land under the ice sheet, and the stability of this "sea ice sheet" is extremely poor. According to the current volume of glaciers, if the Antarctic ice sheet melts completely, the global sea level will rise by about 65 meters. At that time, how much land could human beings live on?

natural disaster

Alpine glacier Strong melting will also lead to some natural disaster Occurrence of. For example, ice lake outburst, flood Glacial debris flow Wait at Qinghai Tibet Plateau Southeast and the himalayas And other regions are more prominent. Europe The Alps Glacier melt water is an important hydropower resource in such regions as Sichuan, and glacier changes have a huge impact on energy supply.

Other impacts

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The main impacts of glacier melting are, first of all, glacier melting , injected into the ocean, resulting in sea level Increased. Recently, major media also released sea level rise The news that more than 3000 cities in the world will be submerged is wrong. The glaciers will never melt completely. The earth has its own feedback system ；

Secondly, the melting of glaciers will also lead to the reduction of the reserves of solid water resources, resulting in Water shortage 。 The drought areas in China, such as those in Xinjiang, are greatly affected Southern Xinjiang , where agriculture and animal husbandry mainly rely on snow mountain melt water, Tarim River And Hexi Corridor It also depends on Glacial recharge ；

There are also studies saying that melting glaciers will release Viruses , bringing devastating disasters to mankind. Scientific researchers Drilling from the polar regions Ice core It was found that it contains ancient viruses, and after tens of millions of years, these viruses are still alive. They believe that, Polar glacier It is the largest stock of ancient viruses. Once the glaciers melt, these viruses may be released, creating an unprecedented catastrophe 。

In addition, melting glaciers will also bring tourism significant impact , some with Snow Mountain Glacier Famous scenic spots may be on the verge of disappearing. Glaciers with lower dimensions, such as the Yulong Snow Mountain Glacier in China, will bear the brunt Climate warming The threat of.

In May 2023, a study published in the monthly journal Nature Geoscience in the UK pointed out that the melting of glaciers caused by temperature rise is causing the oceans to emit more mercury So as to bring risks to the Arctic ecosystem.^[1]

Inhibition ablation

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Glacial ablation

Glacier mass balance In other words, the loss process of glacier material. In temperate glacier areas, glacier material expenditure is mainly ice surface melting; In the polar regions ice sheet With glaciers and a few temperate mountains Glacier terminus Mainly collapse and evaporation; There are also some temperate glaciers melting under and within the ice. The melting of both cold season supply glaciers and warm season supply glaciers is concentrated in the summer half year. Glacial meltwater runoff include Glacial water 、 Granular snow And glaciers Surface area The runoff formed by melting water flowing into the river at the end of the glacier is Alpine mountain area An important source of water for rivers.

The measures to accelerate or inhibit ice body ablation by artificial means are called artificial regulation of ice ablation. The methods of artificial accelerated ablation are divided into physical and chemical methods. Physical methods It is spreading all kinds of black on the ice and snow surface Fine-grained material Blacken ice and snow, reduce reflectivity To accelerate its ablation. The chemical method is to reduce the melting point of ice and snow and release heat Chemicals Spray on the ice and snow surface to promote its melting. Inhibition ablation is weakened by various methods solar radiation And reduce the heat absorption of glaciers.

Defer problems

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In a report, the Intergovernmental Panel on Climate Change also predicted that, the himalayas Many glaciers will melt and disappear before 2035. According to relevant experts, changes in glaciers are mainly affected by temperature and precipitation. Climate warming will promote melting, but the increase of precipitation will, to some extent, cause the increase of glaciers. This impact assessment is currently under study.

Glacier ablation is a long-term and complex subject environmental change It is also fluctuating, and the scientific community's research on glacier ablation is still in progress, and it is still inconclusive.

Action mode

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(Picture) Glacier ablation

(Figure) Glacier transport

Glaciation

Glacial transport

Glaciers have great transport capacity, and can move huge rocks with particle size of 10-20 meters or more. Rock blocks with particle size greater than 1m are called glacial boulders. The transport function of glaciers includes two modes: carrying and pushing. When the glacier moves, the debris inside and on the surface of the glacier will move with the glacier, just like a conveyor belt, which is called carrying. Carrying is the main mode of glacier transport. The movement route of glacier load is determined by the movement track of glacier ice particles. Because the ice bed is an uneven slope, the movement track of ice particles in the glacier changes with the shape of the ice bed. At the protruding part of the ice bed, the ice body is subject to tensile stress, and the overlying ice layer and the underlying ice layer slide downward along the inclined interface between them; In the depression of the bed surface, the ice layer is subject to compressive stress, and the overlying ice layer thrusts upward against the underlying ice layer along the inclined interface between them. Therefore, debris at the bottom of the glacier can also rise to the ice surface. In addition, the movement track of glacial ice particles can make lateral scattering on the plane, and the scattering angle is generally 2 °～ 10 °, and the maximum is 20 °～ 60 °. Pushing means that the front end of the glacier pushes the debris on the ground in the front end of the glacier forward with a huge thrust, which only occurs when the front end of the glacier moves forward. As the glacier is a solid material, the relative position of ice transport rarely changes during transportation, so the glacier transportation does not have the sorting phenomenon according to size and specific gravity.

glacial deposit

(Picture) Glacier ablation

It includes three methods, namely, melt fall, push and stop accumulation. Melt fall refers to a deposition mode in which debris scattered from the surface or edge of the glacier is deposited in situ due to partial melting. When the front of the glacier moves forward, it will look like Bulldozer That way Scraping This deposition method is called pushing. In addition, if the glacier encounters obstacles during its movement, it will be squeezed, melting point will be lowered and melt, and debris scattered in it will accumulate in place. This sedimentation mode is called stop accumulation.

Faced with situation

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The total area of glaciers in the world is about 15 million square kilometers, and that in China is about 60000 square kilometers. These glaciers are closely related to human activities, and their advance and retreat changes are more closely related to human beings living around mountains.

Since the 1980s, the global warming trend has accelerated, and the melting of glaciers has also accelerated. According to observation data, there are nearly 50000 glaciers in China, 80% of which are retreating. Scientists predict that some small glaciers are retreating faster and faster, and may disappear in a decade or decades.

Small glaciers generally refer to glaciers with an area of less than 2 square kilometers and a length of less than 2 kilometers. Yulong Snowmountain The glaciers in the area are relatively small and may disappear within 30 years. But some large glaciers will not melt so fast. The largest glacier in China is 40 kilometers long. The larger mountain glaciers are unlikely to disappear in decades or even a hundred years.

Change significance

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(Picture) Glacier ablation

Glacial change For the world Surface heat balance 、 atmospheric circulation And the ocean ocean current It also has an important impact. Because snow and ice have strong influence on solar radiation Reflex effect ， Glacier area Large scale changes will cause Surface radiation And heat imbalance, resulting in changes in atmospheric circulation. The injection of cold water from the melting of the polar ice sheet into the ocean will change the original ocean current pattern, so as to change the interaction between the ocean and the atmosphere, thus affecting global climate 。

The strong melting of mountain glaciers will also lead to some natural disasters. For example, glacial lake outburst, flood, glacier debris flow, etc. are prominent in the southeast of the Qinghai Tibet Plateau and the Himalayas. Europe The Alps Glacier melt water is an important hydropower resource in such regions as Sichuan, and glacier changes have a huge impact on energy supply.

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