Under the Sea-diments: Reconstructing Past Climate Using South African Marine Sediment Cores Affected by the Agulhas current

Ocean currents play a vital role in regulating global climate. Upwelling systems are an example of this. Upwelling is when cold water, filled with nutrients from the deep ocean, is brought to the surface which leads to a productive ecosystem. Alongside the west coast of South Africa, there is upwelling. On the east coast of South Africa, there is the Agulhas current bringing in warm water. Even with these two ocean currents acting on this area, this region is not as heavily studied as other regions. Understanding this is important when attempting to reconstruct past climate. To begin reconstructing what the climate in this region looked like, deep marine sediment cores taken by the International Ocean Discovery Program (IODP) were used for samples. One particular way to reconstruct past climate is by looking at the chemical composition of the sediment during the Pliocene era. Calcium carbonate comprises the shells and skeletons of coccolithophores so calcium carbonate is a good proxy for the biological productivity of the past. The vast majority of the sediment was comprised of calcium carbonate. The sediment reflectance was found by the IODP and when compared to the calcium carbonate a weak correlation was found. The remaining composition of the sediment is terrigenous because little to no biogenic silica was found using a sodium hydroxide digestion method. Sea surface temperature was also found and lined up with the reflectance data where high reflectance showed warmer temperatures and lower reflectance showed cooler temperatures. Not only is climate showing a change through time but it is showing a clear cycle and pattern. Looking at how sediment changes through time can help us formulate a cycle and add to mapping global climate changes. This can further our understanding of ocean circulation currents' impact on climate and how climate could likely be at the end of the 21st century.