The past climatic history of Siberia has been explored through dating of speleothem samples from caves (Vaks et al., 2013). Speleothems are cave carbonates such as stalactites and stalagmites (see fig.1), which form when calcium carbonate is deposited into a solid from a solution, a process called ‘precipitation’ (Bradley, 2015). Cave conditions are unlikely to be affected by daily or seasonal variances in temperatures therefore through studying speleothems, the climate conditions throughout the past can be inferred and this paper seeks to put forward several predictions for the future. The article uses dated speleothems samples to piece together both temporal and climatic condition data.
As speleothem growth requires moisture to occur the climatic conditions at the time of formation can be inferred through dating. Speleothems are often examined as a record of past climate due to the extensive and detailed records they provide, and their relative ease of examination through radiometric dating techniques (Lowe & Walker, 1997). U-Th or uranium-thorium dating is particularly powerful in dating calcium carbonate materials such as speleothem (Lowe & Walker, 1997). This method of radiometric dating is well-documented as being the best practise in ascertaining dates for speleothem growth, and as a result is a tool to generate the data upon which the paper is based. An in depth detailed discussion regarding U-Th dating is not particularly relevant to this report as it only provided the raw information which is subsequently analysed by the authors.
Speleothems are unable to grow during glacial periods at high latitudes where temperatures are low or where the ground temperature is consistently below freezing (areas of permafrost) due to reduced liquid moisture. In arid areas where moisture availability is also low, speleothem growth is hindered (Vaks et al., 2013). As a result, speleothems are very useful in inferring (are viable proxies for) past conditions in areas samples were taken from. The speleothems sampled in the Vaks et al (2013) paper were taken from areas of variable permafrost in Siberia (see fig 2). As discussed, cave temperatures reflect atmospheric temperatures therefore it is reasonable to assume that speleothem growth is currently inhibited in areas of continuous permafrost (purple shaded areas on fig 2) due to lack of liquid water. These speleothems must have been formed when conditions in the area were warmer and wetter. Through dating the speleothems a historical timeframe can be derived which describes past climatic change.
Vaks et al (2013) give information regarding the different samples and dates of speleothem formation. This in turn is compared to other palaeoclimate records, such as the benthic stack data, greenhouse gas emission and insolation levels. There is a distinct relationship between speleothem formation and these aspects (figure 3, parts B, C, E, F & G) and the paper pieces together both spatial and temporal climate...