A 500-year seasonally resolved δsup18/supO and δsup13/supC, layer thickness and calcite aspect record from a speleothem deposited in the Han-sur-Lesse cave, Belgium

摘要

Speleothem δ18O and δ13C signals enable climatereconstructions at high resolution. However, scarce decadal and seasonallyresolved speleothem records are often difficult to interpret in terms ofclimate due to the multitude of factors that affect the proxy signals. Inthis paper, a fast-growing (up to 2 mm yr?1) seasonally laminated speleothemfrom the Han-sur-Lesse cave (Belgium) is analyzed for its δ18Oand δ13C values, layer thickness and changes in calcite aspect.The studied record covers the period between AD 2001 and 1479 as indicatedby layer counting and confirmed by 20 U / Th ages. The Proserpine proxies areseasonally biased and document drier (and colder) winters on multidecadalscales. Higher δ13C signals reflect increased prior calciteprecipitation (PCP) and lower soil activity during drier (and colder)winters. Thinner layers and darker calcite relate to slower growth and existduring drier (and colder) winter periods. Exceptionally dry (and cold)winter periods occur from 1565 to 1610, at 1730, from 1770 to 1800, from1810 to 1860, and from 1880 to 1895 and correspond to exceptionally coldperiods in historical and instrumental records as well as European wintertemperature reconstructions. More relative climate variations, during whichthe four measured proxies vary independently and display lower amplitudevariations, occur between 1479 and 1565, between 1610 and 1730, and between1730 and 1770. The winters during the first and last periods are interpretedas relatively wetter (and warmer) and correspond to warmer periods inhistorical data and in winter temperature reconstructions in Europe. Thewinters in the period between 1610 and 1730 are interpreted as relativelydrier (and cooler) and correspond to generally colder conditions inEurope. Interpretation of the seasonal variations in δ18O andδ13C signals differs from that on a decadal and multidecadalscale. Seasonal δ18O variations reflect cave air temperaturevariations and suggest a 2.5 °C seasonality in cave airtemperature during the two relatively wetter (and warmer) winter periods(1479–1565 and 1730–1770), which corresponds to the cave air temperatureseasonality observed today. Between 1610 and 1730, the δ18Ovalues suggest a 1.5 °C seasonality in cave air temperature,indicating colder summer temperatures during this drier (and cooler)interval. The δ13C seasonality is driven by PCP and suggestsgenerally lower PCP seasonal effects between 1479 and 1810 compared totoday. A short interval of increased PCP seasonality occurs between 1600 and1660, and reflects increased PCP in summer due to decreased winter recharge.