DOI: 10.25921/d3b9-5d97
title: NOAA/WDS Paleoclimatology - Boch et al. 2009 Katerloch Cave Early Holocene Stable Isotopes

description: Two coeval stalagmites from Katerloch Cave show pronounced intervals 
of low d18O values around 8.2, 9.1, and 10.0 kyr (all ages are reported 
before the year 2000 AD) and represent an inorganic U-Th dated climate 
archive from the southeast of the European Alps, a region where only 
very few well-dated climate records exist. The O isotope curves, 
providing near-annual resolution, allow a direct comparison to the 
Greenland ice core records, as temperature was the primary factor 
controlling the O isotopic composition of Katerloch speleothems.
The 8.2 kyr climate anomaly lasted about one century, from 8196 
to 8100 yr, with a maximum amplitude of 1.1 per mil at 8175 yr. 
The event is characterized by a rapid onset and a more gradual demise 
and U-Th data as well as annual lamina counting support a rapid climate 
change towards cooler conditions within 10-20 yr. There is no strong 
evidence that the 8.2 kyr anomaly was superimposed on a pronounced 
longer-term cooling episode, nor do the new data support two separate 
cooling events within the 8.2 kyr event as reported by other studies. 
Our record also shows a distinct climate anomaly around 9.1 kyr, which 
lasted 70-110 yr and showed a maximum amplitude of 1.0 per mil, i.e. 
it had a similar duration and amplitude as the (central) 8.2 kyr event. 
Compared to the 8.2 kyr event, the 9.1 kyr anomaly shows a more 
symmetrical structure, but onset and demise still occurred within a few 
decades only. The different progression of the 8.2 (asymmetrical) and 
9.1 kyr anomaly (symmetrical) suggests a fundamental difference in the 
trigger and/or the response of the climate system. Moreover, both 
stalagmites show evidence of a climate anomaly around 10.0 kyr, 
which was of comparable magnitude to the two subsequent events.
Using a well constrained modern calibration between air temperature 
and d18O of precipitation for the study area and cave monitoring data 
(confirming speleothem deposition in Katerloch reflecting cave air 
temperature), a maximum cooling by ca 3ºC can be inferred at 8.2 
and 9.1 kyr, which is similar to other estimates, e.g., from Lake 
Ammersee north of the Alps. The O isotopic composition of meteoric 
precipitation, however, is a complex tracer of the hydrological cycle 
and these temperature estimates do not take into account additional 
effects such as changes in the source area or synoptic shifts. 
Apart from that, the relative thickness of the seasonally controlled 
lamina types in the Katerloch stalagmites remains rather constant 
across the intervals comprising the isotopic anomalies, i.e. the 
stalagmite petrography argues against major shifts in seasonality 
during the early Holocene climate excursions.
description: Continuous stable C and O isotope records of speleothem growth during the early Holocene from two coeval stalagmites (K1 and K3) of Katerloch Cave, Austria. The individual chronologies are based on Uranium-Thorium MC-ICP-MS data and the age models are constituted by a slightly adjusted linear fit of the data points within the 2-sigma errors. 	   

Katerloch Cave, Southeast Alps, Styria, Austria:	   
47º5'N, 15º33'E, 900 m a.s.l.