Daniel Sinclair, Gavin Holden and Susan Al-Fahid (Te Herenga Waka–Victoria University of Wellington) and Silvia Frisia and Andrea Borsato (University of Newcastle)
Cave stalagmites and stalactites (speleothems) are an important archive of climate history. Their layered structures capture their growth and geochemical signatures of the water that formed them. In a similar way to ice cores, under the right circumstances, parameters such as trace elements can be related to environmental processes to detect changes in regional hydrology over thousands of years. As a result, they are known as “the ice cores of the tropics”.
The researchers were interested in how rainfall responded to rapid climate changes in the tropical Pacific region. Existing records from Pacific island speleothems hinted that the region experienced major disruptions in rainfall over time. However, correctly interpreting speleothem trace-element records can be tricky as they can be influenced by both growth mechanisms and the speleothem’s crystal fabric, which cause variation within the growth layers.
To strengthen confidence in the interpretation of the records, the Microspectroscopy (XFM) beamline mapping feature was used to study the relationship between trace elements and the crystal fabric at high resolution. The researchers looked back to the most recent glacial period, a time of several rapid global-scale climate perturbations. The team analysed a range of speleothems from Niue and the Cook Islands to characterise a pronounced series of rapid warming and cooling events that took place 35-45,000 years ago.
The team found a close relationship between the colour and crystal structure of the cave formations and their chemical composition. This breakthrough suggests a new way to reconstruct 11 ancient climate changes in the region. The findings could also help improve our understanding of how the South Pacific climate might respond to future changes.
Related research:
Sinclair D, Banner J, Taylor F, Partin J, Jenson J, Mylroie J, Goddard E, Quinn T, Jocson J, Miklavic B. 2012. Magnesium and strontium systematics in tropical speleothems from the Western Pacific. Chemical Geology 294-295:1-17. https://doi.org/10.1016/j.chemgeo.2011.10.008
