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SISAL scientific goals

The SISAL working group has a well established network with over 100 members from 20+ countries.

Phase III

The goal is to harness data-model comparison techniques for improved understanding of climate processes.

Objective 1: Common Era climate interpretations
Speleothem proxy interpretations are region and time-scale dependent. Therefore, we have so far not provided interpretations in the database. Recent developments in speleothem proxy interpretations, the framework for hydroclimate-relevant interpretations provided by Iso2k, and the 2k Network’s project to create a multi-archive Hydro2k database suggest that this is an opportune time to undertake this activity. This will be completed through ongoing collaboration with the 2k Network and SISAL’s regional coordinator framework.

Objective 2: Proxy System Models (PSMs)
PSMs use transfer functions to move between the proxy space and the climate variable space. While several PSMs exist, they either require an extensive array of input variables that are not available for a large number of caves, or favour simplicity at the cost of missing parameters that are highly relevant to particular regions (Hu et al, 2021). The monitoring database being created by the SISAL WG provides a unique opportunity to evaluate the existing PSMs and update / develop a more accurate and widely applicable PSM. This project will be completed in collaboration with the 2k Network and CVAS WGs.

Objective 3: Spatial-statistics techniques
Past work on data-model evaluation using speleothem oxygen isotope data showed that isotopic gradients across space provides one of the most accurate techniques for comparing speleothem against modeled oxygen isotope data (Comas-Bru et al, 2019). Therefore, spatial-statistics techniques will be used to provide isoscapes of critical time periods as single or evolving time slices. The time slices will be obtained using advanced interpolation methods based on spatial-statistics such as kriging or multiple-point geostatistics. It will allow estimating the space-time distribution of isotopes by accounting for factors such as latitude, continentality, or prior information coming from present-day isotope data. 

Phase II

In SISAL Phase II, we used the SISAL database, coupled with cave monitoring, karst and climate modeling studies, to improve our understanding of speleothem records, their climatic interpretation and usefulness for model evaluation.

Specific objectives

1. Assess how cave monitoring data can improve the climatic interpretation of speleothem isotopic records. We are liaising with the cave monitoring community via the Innsbruck Quaternary Research group to gather data from individual researchers.

2. Explore the use of proxy-system and process-based modeling of oxygen and carbon isotopes to explain changes in speleothem isotopic records through time.

3. Assess how trace elements can strengthen climatic interpretations of speleothem isotopic data in addition to providing independent palaeoclimatic and palaeoenvironmental information.

4. Incorporate age-modeling uncertainties into the interpretation of proxy records, building on work already begun in the third year of SISAL Phase 1. Investigation of uncertainties through comparison of different age-modeling techniques will strengthen the age-models of all speleothem archives.

5. Draw on the various approaches listed in the objectives above to reconstruct past climate based on robust interpretations of the speleothem records for use in PMIP non-isotope enabled climate model evaluations.

Waipuna Cave, New Zealand. Image credit: Sebastian Breitenbach.

Waipuna Cave, New Zealand. Image credit: Sebastian Breitenbach.