Determining SISALv2-speleothem growth rates during the Holocene

Speleothems are terrestrial paleoclimate archives that occur abundantly in the low and mid latitudes. They archive changes in the past hydroclimate in many ways, including the rate of calcium carbonate accumulation – their growth rate. However, determining speleothem growth rates, and in particular growth rate changes, is challenging due to speleothem inherent features such as growth hiatuses, and large and abrupt growth rate changes. Low dating resolution poses an additional problem, as the U/Th measurements that allow for precise dating are time-consuming and expensive.

Here, we analyze speleothem growth rates during the Holocene – an ideal period for method testing due to the high abundance of speleothem records in the SISALv2 database. In particular, we compare speleothem growth rates in the early (12-8 kyr BP), mid (8-4 kyr BP) and the late Holocene (4-0 kyr BP). Using synthetically-modelled stalagmites, we test the strengths and weaknesses of state-of-the-art age-depth modelling methods to determine a set of necessary requirements to quantify speleothem growth rates and growth rate changes. Using these, we find slightly higher growth rates in the early Holocene within speleothems that cover at all periods. Comparing growth rates of speleothems that cover only one of the respective periods in the Holocene did not distinguish any period of highest or lowest growth rate. Detailed regional studies and comparison to model data are used to further interpret these results. Reliably determining growth rate changes in the Holocene may help in further understanding and characterizing hydroclimate changes as archived in speleothems also beyond the Holocene.