Abstract
Water isotopes are powerful proxies able to deliver valuable information about past climate conditions at the precipitation site, along the path of the moisture or at its source. We use a recently developed microliter sampling technique associated with continuous-flow laser spectroscopy in order to investigate its potential for direct determination of17Oexcesson microliter amount of water released from speleothem crushing. Results from Milandre Cave stalagmite (Switzerland) suggest that17Oexcessfrom speleothem fluid inclusion water could likely be used as a paleoclimate proxy and to resolve past hydroclimatic changes mainly depending on (i) the technical capability to produce precise and accurate direct measurements and (ii) our understanding of which factors influence the17Oexcessproxy in speleothem fluid inclusion water. With our setup, the main challenge regarding17Oexcessmeasurements is the very low amount of water released by the crushing of speleothem samples, which also lead to the difficulty of producing sample replications. The precision achieved based on duplicate measurements is ∼30 per meg, which is currently a value too high to retrieve robust paleoclimate information. We suggest sample replications and further improvement of the presented method through the increase of the signal to noise ratio and correction for isotope composition—mixing ratio dependence to reach the required precision of 10 per meg or less.
Highlights
Water stable isotopes of oxygen and hydrogen of past precipitation are widely used in paleoclimatology (e.g., Seierstad et al, 2014; Lecavalier et al, 2017; Affolter et al, 2019)
We acknowledge two reviewers for their comments that significantly improved this manuscript
Both authors contributed to the article and approved the submitted version
Summary
Water stable isotopes of oxygen and hydrogen of past precipitation are widely used in paleoclimatology (e.g., Seierstad et al, 2014; Lecavalier et al, 2017; Affolter et al, 2019). Paleoclimate interpretations of 17Oexcess data have been acquired from Greenland (Landais et al, 2018) and Antarctica (Landais et al, 2008; Winkler et al, 2013) ice cores, from gypsum hydration water in lakes from Spain (Gazquez et al, 2018) or from speleothems in Switzerland (Affolter et al, 2015) In these studies, different techniques were used for 17Oexcess measurements of the water: for ice cores, the ice is melted and the water is further analyzed using the method of water fluorination with a precision of ± 6 per meg (e.g., Winkler et al, 2013). After the sample is crushed using a hydraulic press, the released sample water is vaporized and directly flushed to the laser instrument (Picarro L2140-i, Santa Clara, United States) without any treatment of the water molecule prior to its measurement
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