Examining links between dust deposition and phytoplankton response using ice cores

Dust is a major source of nutrients to remote ocean environments, influencing primary productivity (PP). Enhanced oceanic PP causes drawdown of atmospheric CO2 and is considered likely to be a driver of climate variability on glacial-interglacial timeframes. However, the scale of this relationship and its operation over shorter timescales remains uncertain, while it is unclear whether dust fertilisation, or other mechanisms, e.g. nutrient upwelling, are the primary driver of PP in high-nutrient low-chlorophyll (HNLC) ocean regions. In this study, we demonstrate, using dust derived Fe and Methanesulfonic acid (a measure of ocean PP) deposition in ice cores from the South Atlantic (South Georgia Island) and North Pacific (Yukon), that PP is significantly correlated with Dust-Fe on both an event and annual scale. However, measuring the relationship between (dust) Fe fertilization and PP in high resolution ice cores is subject to a number of highly complex factors, which are discussed and together used to recommend future research directions. In conclusion, our research suggests that changes in aeolian Fe flux, due to climate change and human activity in dust source regions, could have significant implications for HNLC ocean PP and, therefore potentially, carbon sequestration.