The climatic constraints on speleothem deposition in SW Asia

Abstract Speleothems are high-quality archives of past climatic information. They have been crucial in revealing past changes in annual precipitation (AP), and their presence in water-limited arid regions is used as direct evidence for past wetter climates. However, the exact climate parameters constraining their deposition are unclear. A regionally specific AP-based minimum of 300–350 mm yr−1 has been applied but has not been widely tested and does not explicitly consider other important factors (temperature, evaporation, and topography). Here, we combine field observations of speleothem deposition with logistic regression (LR) and random forest (RF) statistical models to identify the climatic constraints controlling the modern distribution of active and inactive speleothems over a broad geographic region (SW Asia). Using a suite of climatological information related to precipitation, evaporation, temperature, and topography, LR shows that as AP increases, so does the probability of speleothem deposition. However, there is no clear threshold at which speleothem deposition is more likely. This shows a single parameter value cannot be used to determine speleothem deposition across the region. RF combines the effects of several climate metrics to predict areas of active speleothem deposition in SW Asia.