Mineral dust coupled with climate-carbon cycle on orbital timescales over the past 4 Ma

Mineral dust is one of the environmental component for forcing the global climatic change, and not only influences the amount of solar radiation incoming the earth surface, but affects atmospheric CO₂ concentrations in the past through wind transport to ocean and subsequent biological pumping. Mineral dust is one of the important driving factors for variations of atmospheric CO₂ content in Quaternary glacial-interglacial cycles. Here, we reconstruct the interaction between the Asian dust flux (as a representative of the global dust flux), the cryosphere system (δ¹⁸O_benthic), and the global carbon cycle since 4 Ma using phase analysis, power decomposition analysis, obliquity sensitivity calculation and evolutionary spectral analysis. The evolutionary spectra show that orbital-scale variability of mineral dust, δ¹⁸O_benthic and δ¹³C_benthic are very similar over the past 4 Ma, except the interval time of 3-2 Ma that shows higher obliquity energy (higher O/T values) of the δ¹⁸O_benthic and δ¹³C_benthic data. Therefore, we suggest that the Asian and/or global dust is acted as a transmitter transporting the periodic signals stored in the Arctic ice sheet to deep-sea δ¹³C_benthic. This is why δ¹³C_benthic data have very similar changes with the Arctic ice sheets on the orbital scale. Sharp increase of global dust flux after 1.6 Ma resulted in a significant weakening of the 405 kyr long eccentricity power of δ¹³C_benthic series because Arctic ice sheet signals strongly inhibit the influences of low-latitude solar insolation variations on deep-sea δ¹³C_benthic system. In addition, we suggest that strengthened global drought and increases of dust fluxes since late Miocene probably forced the anti-phase relationship between δ¹⁸O_benthic and δ¹³C_benthic around 6 Ma, rather than the expansion of Arctic ice sheet. Our results highlight the close coupling between dust fluxes and the global carbon cycle, with deeply influencing marine productivity and land surface processes.

Keywords: mineral dust; deep sea oxygen isotope (δ¹⁸O_benthic ); deep sea carbon isotope(δ¹³C_benthic); orbital  periods ; inland Asia