TRACKING LONG‐TERM CHANGES IN CLIMATE USING ALGAL INDICATORS IN LAKE SEDIMENTS
TRACKING LONG‐TERM CHANGES IN CLIMATE USING ALGAL INDICATORS IN LAKE SEDIMENTS
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DOI：
10.1046/j.1529-8817.2000.00049.x
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发表时间：
2000-12
影响因子：
2.9
通讯作者：
J. Smol;B. Cumming
中科院分区：
文献类型：
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作者：
J. Smol;B. Cumming
随着人们认识到人类活动，例如所谓的温室气体的加速释放，可能会改变我们大气的热特性，对气候变化研究的兴趣也变得更加重要。重要的社会、经济和科学问题包括以下内容。气候在变化吗？如果是这样，这些变化是否与人类活动有关？干旱或飓风等极端天气的发生频率是否在增加？为了回答这些问题，需要在广泛的空间和时间尺度上的长期气象数据。不幸的是，这些数据从来没有收集;因此，间接代用方法必须用来推断过去的气候趋势。一个相对未开发的古气候数据来源是基于使用保存在湖泊沉积物剖面中的藻类（特别是硅藻）的环境最佳值和耐受性来追溯过去的气候趋势。古植物学家使用了两种方法。虽然仍然有争议，但已经尝试直接推断气候变量，如温度，从过去的藻类组合。这些类型的分析的主要假设是，物种组成是直接相关的温度或藻类组合有关的一些变量线性相关的温度。第二种更常用的方法是推断湖沼学变量（例如水化学，湖泊冰盖等）。这与气候有关。虽然古湖泊学的方法在气候区域之间大致相似，但古植物学家追踪的环境梯度可能非常不同。例如，极地地区的气候推断集中在过去的湖泊冰条件上，而在北极树木交错带附近的湖泊中，古植物学家已经开发出推断过去湖水溶解有机碳的方法，因为这个变量与流域中针叶树的密度有关。在干旱和半干旱地区的封闭盆地湖泊中，过去的湖水盐度，可以从化石藻类组合中稳健地重建，与蒸发和降水的平衡（即干旱频率）密切相关。一些最近的古植物学工作的例子包括记录了19世纪北极高纬度环境的惊人环境变化，这些变化被认为与气候变暖有关。与此同时，基于硅藻的盐度重建（例如北美和非洲的大平原）揭示了过去几千年来长时间的干旱，远远超过了近代的记录。在仪器记录范围之外的显著气候变化对人类社会的可持续性有很大影响。只有用长远的眼光，我们才能理解自然气候的变化和人类活动对气候的潜在影响，从而提高我们理解未来气候的能力。
Interest in climate change research has taken on new relevance with the realization that human activities, such as the accelerated release of the so‐called greenhouse gases, may be altering the thermal properties of our atmosphere. Important social, economic, and scientific questions include the following. Is climate changing? If so, can these changes be related to human activities? Are episodes of extreme weather, such as droughts or hurricanes, increasing in frequency? Long‐term meteorological data, on broad spatial and temporal scales, are needed to answer these questions. Unfortunately, such data were never gathered; therefore, indirect proxy methods must be used to infer past climatic trends. A relatively untapped source of paleoclimate data is based on hindcasting past climatic trends using the environmental optima and tolerances of algae (especially diatoms) preserved in lake sediment profiles. Paleophycologists have used two approaches. Although still controversial, attempts have been made to directly infer climatic variables, such as temperature, from past algal assemblages. The main assumption with these types of analyses is that species composition is either directly related to temperature or that algal assemblages are related to some variable linearly related to temperature. The second more commonly used approach is to infer a limnological variable (e.g. water chemistry, lake ice cover, etc.) that is related to climate. Although paleolimnological approaches are broadly similar across climatic regions, the environmental gradients that paleophycologists track can be very different. For example, climatic inferences in polar regions have focused on past lake ice conditions, whereas in lakes near arctic treeline ecotones, paleophycologists have developed methods to infer past lakewater‐dissolved organic carbon, because this variable has been linked to the density of coniferous trees in a drainage basin. In closed‐basin lakes in arid and semiarid regions, past lakewater salinity, which can be robustly reconstructed from fossil algal assemblages, is closely tied to the balance of evaporation and precipitation (i.e. drought frequency). Some recent examples of paleophycolgical work include the documentation of striking environmental changes in high arctic environments in the 19th century believed to be related to climate warming. Meanwhile, diatom‐based reconstructions of salinity (e.g. the Great Plains of North America and Africa) have revealed prolonged periods of droughts over the last few millennia that have greatly exceeded those recorded during recent times. Marked climatic variability that is outside the range captured by the instrumental record has a strong bearing on sustainability of human societies. Only with a long‐term perspective can we understand natural climatic variability and the potential influences of human activities on climate and thereby increase our ability to understand future climate.