Reconstruction of Sothern Ocean dust fluxes and dust provenance areas at highest spatial resolution: implications from 230Thxs, isotopic and REE data

Abstract:

The study of dust fluxes in the Southern Ocean (SO) is crucial to understand processes and feedback mechanisms in the SO since atmospheric dust is considered to play a key role in past atmospheric CO₂ variability by affecting the marine biological production through iron fertilization. We present ²³⁰Th_xs, isotopic (Sr, Nd, Pb) and REE data of numerous surface samples across the Pacific sector of the SO in order to determine lithogenic mass accumulation rates (MAR) (corrected for sediment focusing) and possible dust provenance areas. Our MAR data display highest values near New Zealand´s east coast (South Island), however this may not reflect a pure Australian/New Zealand dust signal due to a strong influence of fluvial sediment input from New Zealand sources. In contrast, we interpret the open ocean MAR values as derived from the Australian/New Zealand dust plume, which might reach as far east as ~100° W. The highest MAR values among the open ocean samples are found south of the winter sea ice front (WSI), and likely reflect the admixture of ice rafted debris (IRD). Further east of ~100° W, the MAR data exceed the open ocean samples by up to a factor of ~6, consistent with predominating terrigenous input from southernmost Patagonia and Antarctica. Combining the MAR data set with provenance sensitive proxies (isotopic and REE data) enables us to identify at least 3 different possible provenance areas (Australia/New Zealand, Antarctica and Patagonia) and to reconstruct the possible pathway of the Australian/New Zealand dust plume. Since the atmospheric circulation (westerly winds) is one controlling factor influencing the distribution of dust over the SO this data set also allows us to infer variations of wind speed and strength of the westerly wind belt.