Recent Central American and low latitude climate variability revealed using speleothem-based rainfall proxy records from southern Belize

Abstract

Comprehensive assessment of recent tropical climate variability is essential in order to understand the full spatial expression of climate change in the context of long term climate variability. This requires highly resolved and precisely dated tropical proxy records which include the critical transition from the pre-industrial to industrial eras. Speleothem provide highly-resolved and well preserved climate signals and are particularly valuable in tropics where few alternative high resolution records are available. This thesis presents a comprehensive study of recent Central American and low latitude climate variability through assessment of two highly resolved speleothem stable isotope based rainfall proxy records from Yok Balum Cave, southern Belize.
The YOK-G stalagmite δ13C record has a bi-monthly resolution and robust chronology permitting the inference of palaeo-seasonality as well as intra annual rainfall variations over the last 453 years. The record strongly suggests that volcanic aerosol injections into the Northern Hemisphere atmosphere result in southward Intertropical Convergence Zone (ITCZ) repositioning, and firmly implicate anthropogenic aerosol emissions as having caused 20th Century rainfall reductions in the northern tropics.
The YOK-I stalagmite δ13C record provides a bi-annually resolved correlate records of North Atlantic Oscillation for the last 2000 years. Links between high latitude explosive volcanism and repositioning of the ITCZ are further investigated with emphasis on the subsequent impact of observed North Atlantic Oscillation (NAO) phases. High latitude eruptions are compellingly linked to negative NAO circulatory patterns in the North Atlantic thereby providing new insight into atmospheric mechanics of the North Atlantic.
Cave monitoring data provides essential background information on cave environmental variables which could modify climate signals preserved within speleothem carbonate, precluding or complicating interpretations. Using remote monitoring techniques the cave ventilation dynamics and hydrology at Yok Balum are characterised, thereby helping to put the speleothem geochemical data discussed into correct environmental context.