Date of Award
Master of Science (MS)
Linda C. Ivany
climate, coral, ENSO, intra-annual extension rate, numerical modeling, Sr/Ca
Physical Sciences and Mathematics
The relationship between coral growth and environmental parameters is not straightforward, and few studies have explored intra-annual changes in extension rate. Variations in the magnitude and timing of intra-annual extension could be influenced by various environmental parameters such as sea surface temperature (SST), light and nutrient availability, turbidity or salinity stress, as well as by inter-annual climate variations such as the El Niño-Southern Oscillation (ENSO). In this study we use SST proxy data from Porites spp. corals to model intra-annual growth using an iterative numerical model comparing growth and temperature sine functions to measured Sr/Ca data to find the best combination of intra-annual variation in both variables. This approach converts sampling distance within cores into time, providing a framework that allows us to quantify how extension rate varies both within and between years. The model was applied to coral records spanning both the tropical Pacific (Australia to the Galapagos) and the past 400 years (Little Ice Age to present). To validate model results, modern coral data are compared with observational temperature and ENSO records. In this project, we focused on testing the idea that intra-annual SST is a dominant control on the timing of intra-annual coral extension. Results indicate that maximum coral extension in the West Pacific typically occurs during the periods of warmest SST, and in the East Pacific dominantly in periods of cooler SST. These records also indicate that multiple exogenous factors influence skeletal extension in these dynamic equatorial settings, particularly in the context of ENSO. Growth recovered from these records offers a picture of how extension rate and environment interact in the Equatorial Pacific. This modeling approach has the potential to improve seasonally resolved coral records of climate, and for understanding the relationship between coral calcification and climate change by comparing changes in intra-annual extension patterns over time.
McCraw, Jessie, "Modeling intra-annual variation in coral extension rate using multiproxy geochemical records from Pacific corals" (2020). Theses - ALL. 451.