Accurate dating of stalagmites from low seasonal contrast tropical Pacific climate using Sr 2D maps, fabrics and annual hydrological cycles

Faraji, Mohammadali; Borsato, Andrea; Frisia, Silvia; Hellström, John; Lorrey, Andrew; Hartland, Adam; Greig, Alan; Mattey, D. P.

doi:10.1038/s41598-021-81941-x

Cited by 23 publications

(30 citation statements)

References 59 publications

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“…Less-used indicators of environmental conditions include the variations in physical features of speleothems such as density, colour, and lamina thickness, which are a function of hydrology, karst conditions, drip rate, and drip water chemistry (Fairchild and Baker, 2012). These processes are reflected in the speleothem lamina growth rate and seasonal depositional changes (dry/wet) and can be observed by using high resolution imaging (Faraji et al, 2021). Accounting for these features can improve the interpretation of geochemical data.…”

Section: Introductionmentioning

confidence: 99%

Mid-Holocene rainfall changes in the southwestern Pacific

Fernandez

Braun

Fox

et al. 2022

Preprint

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Abstract. A better understanding of ENSO dynamics is essential for modelling future climate change and its impacts on the ecosystems and lives of the inhabitants of the tropical Pacific islands, which face considerable environmental risk in the coming decades. This study reconstructs past ENSO dynamics using a multi-proxy approach applied to a stalagmite from Niue Island that covers the period 6.4–5.4 ka BP. δ18O and δ13C, trace-element concentrations and image analysis are linked to an age-depth model constrained by eight U/Th dates and a complete lamina count. Principal component analysis of the proxy time series reveals hydrological changes at seasonal scale that are expressed in differential stalagmite lamina growth and geochemical characteristics. Increased concentrations of host-rock derived elements (Mg/Ca and U/Ca) and higher δ18O and δ13C values are observed in the dark, dense calcite laminae that are deposited during the dry season, whereas during the wet season higher concentrations of soil derived elements (Zn/Ca, Mn/Ca) and higher δ18O and δ13C values are found in pale, porous calcite laminae. Greyscale intensity values measured along the stalagmite growth axis are used here as an indicator of colour and density changes of the alternating laminae, allowing for the construction of a further seasonality record which expresses the contrast between wet and dry seasons. The multi-proxy record from Niue shows seasonal cycles associated with hydrological changes controlled by the South Pacific convergence zone. Wavelet analysis of the greyscale record reveals that ENSO was continuously active during the depositional period, with two weaker intervals at 6–5.9 and 5.6–5.5 ka BP. ENSO activity is also observed in the seasonality record, but muted periods are more prolonged, and intervals of significant ENSO-band power are more episodic. Recurrence analysis of nonlinear behaviour shows the influence that ENSO activity exerts on seasonality patterns and allows us to quantify the predictability of the climate system. Our results suggest that recurrence in the seasonal cycle of rainfall was reduced during periods when ENSO activity was stronger, pushing the system towards stochastic conditions. The tipping points from stochastic to predictable conditions may represent transitions in the Tropical Pacific mean state.

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Section: Introductionmentioning

confidence: 99%

Mid-Holocene rainfall changes in the southwestern Pacific

Fernandez

Braun

Fox

et al. 2022

Preprint

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“…Laminae counting and error estimate in this study was made by determining the position of the colloidal laminae and Sr peaks on thin section images and synchrotron Sr maps at five confidence levels (> 95%, 75-95%, 50-75%, 25-50%, 5-25%, and < 5% confidence) using ImageJ software package (Faraji, et al, 2021). The calculated error is up to 13 years for 1760 CE to 1887 CE, and up to 4 years for 1888 CE to 2005 CE.…”

Section: Chronology Buildingmentioning

confidence: 99%

“…The results of the PCA are shown in Figure 5 and Table S4. PC1, PC2 and PC3 explain 46.7%, 19.2% and 8.8% of the variation in the dataset respectively. S5, between group sum of squares = 3.9).…”

Section: Principal Component Analysismentioning

confidence: 99%

Past fires and post-fire impacts reconstructed from a southwest Australian stalagmite

McDonough¹,

Treble²,

Baker³

et al. 2021

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Our current understanding of climate and its relationship to fires is generally confined to the recent past where instrumental records and satellite imagery are available. Speleothem records of past environmental change provide a unique opportunity to explore fire frequency and intensity in the past, and the antecedent climatic conditions leading to fire events. Here, we compare fire sensitive geochemical signals in a stalagmite from Yonderup Cave, a shallow cave in Western Australia, where well-documented wildfire events have occurred in recent decades. Principal component analysis of the stalagmite time-series revealed distinct peaks in a combination of phosphorus and metal (aluminium, zinc, copper and lead) concentrations, interpreted to have come from ash, in response to known fire events. This method is extended to identify fires during the growth interval of the speleothem (1760 CE-2005 CE). We identify lower and less variable peak phosphorus concentrations in the pre-European period that are consistent with low-intensity cultural burning by Indigenous Australians. We also identify an intense wildfire event occurring around 1897 ± 5 CE. The combination of climate and fire sensitive proxies in the speleothem indicates that this wildfire was preceded by a multi-decadal dry period. We interpret that post-fire changes in surfacecave hydrology resulted from heat-induced deformation of the shallow karst bedrock brought about by the intensity of this fire. These findings have implications for the interpretation of speleothem records from shallow caves in fire-prone climates and show the potential for speleothems to provide records of fire intensity and recurrence intervals. Further development of these records could lead to a better understanding of the climate-fire relationship and the effects of land-management practices on wildfire frequency and intensity.October 2019 and February 2020, during which nearly 17 million hectares of land were burned are occurring with increasing frequency. In the Northern hemisphere, in 2020 more than 4% of the total 100 million acres of the state of California land were burned. Karst systems, where caves host speleothems (e.g., stalagmites, stalactites and flowstones), can provide long-term records of changes in climate and the environment (e.g. Bar-Matthews et

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“…Laminae counting and error estimate was made by determining the position of the Sr peaks on two parallel areas of the Sr maps at three confidence levels (> 95%, 50-95% and <50% confidence) using ImageJ software package according to the method outlined in ref. 9 .…”

Section: Supplementary Tablesmentioning

confidence: 99%