摘要：

Nitrogen isotopic composition (d15N) of organic matter bound and preserved in diatom frustules is a useful tool to reconstruct surface nutrient conditions and upwelling strength in the Antarctic Zone in the past. Previous work suggests that during ice ages, upwelling was weaker in the Antarctic Zone, leading to more efficient biological pump which likely contributed to the low level of atmospheric CO2. This talk presents high-resolution diatom-bound d15N from two sectors of the Antarctic Zone, showing that the changes in upwelling strength and nitrate supply to the surface ocean in the Antarctic Zone are driven by changes in the position and/or intensity of the Southern Westerly Wind, which are in turn explained by three mechanisms: global climate change, interhemispheric heat asymmetry, and mid-high latitude temperature gradient driven by obliquity.