Isotope hydrology of dripwaters in a Scottish cave and implications for stalagmite palaeoclimate research

Papers published in Hydrology and Earth System Sciences Discussions are under open-access review for the journal Hydrology and Earth System Sciences Abstract Dripwater hydrology and hydrogeochemistry is particularly useful to constrain the meaning of speleothem palaeoclimate archives, for example using δ 18 O signatures. Here, we calibrate the relationship between δ 18 O in precipitation, percolation waters and contemporary calcite deposits, at Tartair cave, Sutherland, NW Scotland, an At-5 lantic site sensitive to regional changes both of temperature and precipitation. Monthly precipitation displayed a 7.1‰ range in δ 18 O, a negative linear relationship with rainfall amount, and no correlation with temperature. Autogenically-derived cave percolation waters show little variation in δ 18 O during the same period and their annual weighted mean is the same as that of the local precipitation. This evidence together with hydro-10 logical data and electroconductivity values indicates that percolation waters are well mixed and dominated by stored water. Calculated values of δ 18 O of calcite deposited in this cave environment indicate that the cave deposits are forming close to isotopic equilibrium and kinetic effects are negligible. Comparison of a high-resolution δ 18 O stalagmite record with the instrumental record of climate indicates that isotopically heavy 15 values are reflective of relatively cold, dry conditions (and vice-versa for warm, wet condition) and hence that stalagmite oxygen isotopes provide an appropriate means of investigating the palaeoclimate in this location.