📚 The Nature and Distribution of Cold Environments | 冷环境的性质与分布
Cold environments are regions where water is largely frozen and low temperatures directly control landforms, ecosystems and human activity. In the Edexcel A-Level Geography specification, this topic examines the global distribution of polar, alpine and periglacial landscapes, together with the climatic and physical controls that explain their location and characteristics.
冷环境是指水分主要以固态存在、低温直接控制地貌、生态系统和人类活动的区域。在 Edexcel A-Level 地理大纲中，本专题研究极地、高山和冰缘景观的全球分布，以及解释其位置与特征的气候和自然控制因素。
1. Defining Cold Environments | 冷环境的定义
A cold environment is broadly defined as an area where mean annual air temperature is below 0 °C, so precipitation often falls as snow and ice can persist for long periods. Cold environments include ice sheets, ice caps, glaciers, tundra and permafrost zones.
冷环境广义上指年均气温低于 0 °C 的区域，因此降水多以雪的形式出现，冰雪可以长期存在。冷环境包括冰盖、冰帽、冰川、苔原和多年冻土区。
These areas form part of the cryosphere, the frozen-water portion of the Earth system. The cryosphere contains glaciers, ice sheets, ice shelves, sea ice, seasonal snow cover and frozen ground, all of which store water in solid form for months to thousands of years.
这些区域构成冰冻圈，即地球系统中水分冻结的部分。冰冻圈包含冰川、冰盖、冰架、海冰、季节性积雪和冻土，它们以固态形式储存水分，时间从数月到数千年不等。
It is useful to separate glacial environments, where moving ice is the dominant agent, from periglacial environments, which are cold but not glaciated and are dominated by permafrost and frost action. Both are cold environments but have different landform assemblages and processes.
区分冰川环境与冰缘环境很有用：冰川环境以运动冰体为主要营力，而冰缘环境虽然寒冷但无冰川覆盖，以多年冻土和冻融作用为主。两者同属冷环境，但具有不同的地貌组合和过程。
2. Global Distribution Patterns | 全球分布格局
The largest cold environments occur at high latitudes. Antarctica contains about 90% of Earth’s ice, while Greenland holds most of the Northern Hemisphere’s ice sheet. Extensive permafrost underlies northern Canada, Alaska and Siberia, forming a circumpolar belt around the Arctic Ocean.
规模最大的冷环境位于高纬度地区。南极洲拥有地球约 90% 的冰量，而格陵兰保存了北半球大部分冰盖。广阔的多年冻土分布于加拿大北部、阿拉斯加和西伯利亚地下，形成环绕北冰洋的环极地带。
Smaller but widely distributed cold environments appear in high mountain ranges, including the Himalayas, Andes, Rockies, Alps and Southern Alps. In these regions, altitude lowers temperatures sufficiently for glaciers to form even at low or middle latitudes.
规模较小但分布广泛的冷环境出现在高山山脉，如喜马拉雅山、安第斯山、落基山、阿尔卑斯山和南阿尔卑斯山。在这些地区，海拔使温度降低到足以形成冰川，即使它们位于低纬度或中纬度。
Cold environments therefore follow two broad distribution rules: they are found at high latitudes and high altitudes. The snowline, the lower limit of permanent snow, falls from about 5,000 m near the equator to sea level in polar regions.
因此，冷环境遵循两大分布规律：分布在高纬度和高海拔地区。雪线，即永久积雪的下限，从赤道附近的约 5,000 米降至极地地区的海平面。
| Type 类型 | Typical Location 典型位置 | Key Features 主要特征 |
|---|---|---|
| Polar ice sheet 极地冰盖 | Antarctica, Greenland 南极洲、格陵兰 | Vast ice mass, extreme cold, very low precipitation 巨大冰体、极寒、降水极少 |
| Ice cap 冰帽 | Iceland, Canadian Arctic 冰岛、加拿大北极地区 | Smaller dome-shaped ice mass 较小圆顶状冰体 |
| Alpine glacier 高山冰川 | Himalayas, Andes, Alps 喜马拉雅山、安第斯山、阿尔卑斯山 | Valley glaciers, high relief, steep slopes 谷冰川、高起伏、陡坡 |
| Tundra and permafrost 苔原与多年冻土 | Siberia, Alaska, northern Canada 西伯利亚、阿拉斯加、加拿大北部 | Frozen ground, low vegetation, active layer 冻土、低矮植被、活动层 |
3. Polar Environments | 极地环境
Polar environments such as Antarctica and the Arctic are dominated by ice sheets, ice shelves and sea ice. Mean annual temperatures can fall below -50 °C on the Antarctic Plateau, and much of Antarctica receives less than 50 mm precipitation per year, making it a polar desert.
南极和北极等极地环境以冰盖、冰架和海冰为主。南极高原的年均温度可低于 -50 °C，南极大部分地区年降水量不足 50 毫米，属于极地荒漠。
Despite low snowfall, ice accumulates because ablation is very limited and old ice is buried and compressed over thousands of years. In central Antarctica, the ice sheet reaches thicknesses of more than 4,000 m in places.
尽管降雪量少，但由于消融极为有限，古老冰体在数千年中被埋藏并压实，冰仍然不断累积。在南极洲中部，冰盖厚度在部分地区超过 4,000 米。
Sea ice also expands and contracts with the seasons. Around Antarctica, sea ice can extend over 18 million km² in winter and shrink to about 3 million km² in summer, which strongly alters albedo and ocean-atmosphere heat exchange.
海冰也随季节扩张和收缩。在南极洲周围，海冰冬季可扩展到 1,800 万平方公里以上，夏季缩减至约 300 万平方公里，这强烈改变了反照率和海气热量交换。
4. Alpine and High-Mountain Environments | 高山环境
High-mountain cold environments occur above the snowline, where annual snow accumulation equals or exceeds summer melting. The snowline altitude varies with latitude, aspect and precipitation, so equatorial mountain glaciers require much higher altitudes than polar glaciers.
高山冷环境出现在雪线以上，即每年积雪量等于或大于夏季融化量的区域。雪线高度随纬度、坡向和降水而变化，因此赤道山地冰川比极地冰川需要更高的海拔。
Temperature falls with altitude at an average lapse rate of about 6.5 °C per 1,000 m. This allows ice to form on high equatorial peaks such as Kilimanjaro and the Andes even though surrounding lowlands are tropical.
气温随海拔升高而下降，平均递减率约为每 1,000 米 6.5 °C。这使得赤道高山峰，如乞力马扎罗山和安第斯山，尽管周围低地为热带气候，仍能形成冰体。
Alpine glaciers typically occupy valleys and erode distinct features, including cirques, arêtes, pyramidal peaks and U-shaped valleys. These landforms are later used as evidence of former cold environments in areas that are now deglaciated.
高山冰川通常占据谷地，并侵蚀出独特的地貌，包括冰斗、刃脊、角峰和 U 形谷。这些地貌后来被用作现今已无冰川地区曾经存在冷环境的证据。
5. Periglacial Environments and Permafrost | 冰缘环境与多年冻土
Periglacial environments are cold, non-glacial areas where permafrost and intense frost action dominate. They include much of Siberia, northern Canada, Alaska and the Tibetan Plateau, and they can occur at high latitude or high altitude.
冰缘环境是寒冷但无冰川覆盖的区域，以多年冻土和强烈冻融作用为主，包括西伯利亚、加拿大北部、阿拉斯加和青藏高原的大部分地区。它们既可以出现在高纬度，也可以出现在高海拔。
Permafrost is ground that remains below 0 °C for at least two consecutive years. It may be continuous, discontinuous or sporadic depending on temperature and local conditions, and its upper active layer thaws in summer and refreezes in winter.
多年冻土指至少连续两年保持在 0 °C 以下的地层。根据温度和局地条件，它可以是连续的、不连续的或零星的，其上部活动层在夏季融化、冬季再冻结。
Freeze-thaw cycles drive periglacial processes such as frost heave, frost shattering and solifluction. These processes create patterned ground, ice wedges, pingos and blockfields, which are distinctive indicators of cold environments.
冻融循环驱动冻胀、冻裂和泥流等冰缘过程。这些过程形成多边形土、冰楔、热融丘和石海，它们是冷环境的独特指示物。
6. Climatic Controls: Latitude and Radiation | 气候控制因素：纬度与辐射
Latitude is the primary control on cold environments because solar radiation strikes polar regions at a low angle. The same amount of energy spreads over a larger surface area, so energy received per unit area is much less than at the equator.
纬度是冷环境的主要控制因素，因为太阳辐射以低角度到达极地。相同能量分散在更大的地表面积上，因此单位面积接收的能量远低于赤道地区。
In addition, radiation travels through a greater thickness of atmosphere at high latitudes, increasing absorption, scattering and reflection before it reaches the surface. The polar night removes solar input entirely for weeks or months in winter.
此外，在高纬度地区，太阳辐射穿过更厚的大气层，在到达地面前被吸收、散射和反射得更多。极夜则使冬季数周或数月完全没有太阳辐射输入。
Net radiation is negative for much of the polar year, producing a persistent heat deficit. This energy loss keeps air and ground temperatures below freezing and allows snow, ice and permafrost to survive through summer.
极地一年中的大部分时间净辐射为负，形成持续的热量亏损。这种能量损失使空气和地面温度保持在冰点以下，让冰雪和多年冻土能够度过夏季而继续存在。
7. Climatic Controls: Altitude, Continentality and Ocean Currents | 气候控制因素：海拔、大陆性与洋流
Altitude lowers temperature because the atmosphere becomes thinner and less able to retain heat. This is why high mountains in low latitudes, such as the Andes or East African peaks, can support glaciers despite their equatorial location.
海拔降低温度，因为大气变薄，保温能力减弱。这就是低纬度高山，如安第斯山或东非山峰，尽管位于赤道附近，仍能发育冰川的原因。
Continentality describes the effect of distance from the sea on temperature range. Interior areas of Siberia and northern Canada have extremely cold winters and short warm summers, which favours deep permafrost even at lower latitudes than coastal areas.
大陆性指远离海洋对温度变化幅度的影响。西伯利亚和加拿大北部内陆地区冬季极冷、夏季短而暖，这有利于在比沿海更低纬度形成深厚的多年冻土。
Ocean currents also redistribute heat. Cold currents such as the Labrador Current and the West Greenland Current lower coastal temperatures and can extend cold conditions toward lower latitudes, while warm currents may restrict sea ice development.
洋流也会重新分配热量。拉布拉多寒流和西格陵兰寒流等冷洋流会降低沿岸温度，使寒冷条件向较低纬度扩展，而暖流则可能限制海冰的发育。
8. The Role of Albedo and Feedback | 反照率与反馈机制的作用
Snow and ice have a high albedo, reflecting 60-90% of incoming solar radiation back to space. This reflection reduces surface heating and helps maintain the low temperatures that allow cold environments to persist.
雪和冰具有高反照率，可将 60-90% 的入射太阳辐射反射回太空。这种反射减少地表增温，有助于维持使冷环境得以持续的低温。
Bare ground or open water has a much lower albedo, so it absorbs more solar energy. If warming reduces snow and ice cover, darker surfaces are exposed, absorbing extra heat and accelerating further melting: this is the positive ice-albedo feedback.
裸露地面或开阔水面的反照率低得多，因此会吸收更多太阳能。如果变暖减少冰雪覆盖，较暗的表面就会暴露出来，吸收额外热量并加速进一步融化：这就是正反馈的冰-反照率反馈。
Albedo feedback is strongest at the margins of ice sheets and sea ice, where small temperature changes can convert extensive bright surfaces into darker land or ocean, amplifying regional and
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