Sara Todorovic

Witnesses to the Climate Emergency: Ocean acidification crisis and global warming observations from tropical corals (OASIS) - Pacific Region

One of the alarming consequences of climate change is ocean acidification (OA), also commonly dubbed as “the other CO₂ problem”. It is threatening the coral reefs, ecosystems of imminent importance for millions of people who depend on their ecosystem services, as well as global production of one of the primary food sources – fish. Unfortunately, the scientists have had to rely on only a few ship track and station based measurements of pH that are in operation since the 1990s, and model predictions of the past values so far. Corals cores provide the opportunity to fill this data gap. They can provide us with monthly to annual paleoclimatic signals that date back to preindustrial times, making it possible to analyze the development and variation of the oceanic pH, sea surface temperature and sea surface salinity, as well as to understand the importance of the human factor in these processes. So far the majority of studies have focused on using the boron isotope measurements to reconstruct the pH variation in the marginal areas like the Chinese sea and at the Great Barrier Reef but have neglected open ocean conditions in the Pacific and the Atlantic.

During my PhD, I will work with the coral samples from the Pacific Ocean and focus my research on that region. The main research objective is to determine the pH values of seawater in the Pacific Ocean in order to study the development of the ocean acidification since the preindustrial time. With several coral cores from the region I will be able to reconstruct seasonal changes in sea surface temperature and sea surface salinity, yearly to seasonal changes in pH, as well as to make an estimation of the carbon uptake of the ocean making it possible to predict future developments. To do this I plan to measure Boron, Oxygen and Carbon isotopes, and also ratios of trace elements such as Strontium, Calcium, Lithium and Magnesium, which serve as proxies to obtain a comprehensive picture of environmental conditions and climate change since the preindustrial time. A part of my work will be making a comparative, global record of studied parameters and studying the inter-regional variation between the Atlantic, Pacific and Indian oceans in cooperation with other project collaborators as well.