Coccolithophore productivity of sediment core GeoB12613-1 from the western Indian Ocean (off Tanzania)

We present a new coccolithophore productivity reconstruction spanning the last 300 ka in core GeoB12613-1 retrieved from the western tropical Indian Ocean (IO), an area that mainly derives its warm and oligotrophic surface waters from the eastern IO. Application of a calibrated assemblage-based productivity index indicates a reduction in estimated primary productivity (EPP) from 300 ka to the present, with reconstructed EPP values ranging from 91 to 246 g C/m2/yr. Coccolithophore assemblages and coccolith fraction Sr/Ca indicate three main phases of productivity change, with major changes at 160 and 46 ka. The productivity and water-column stratification records show both dominant precession and obliquity periodicities, which appear to control the paleoproductivity in the study area over the last two glacial-interglacial cycles. Shallowing of the thermocline due to strengthening of the trade winds in response to insolation maxima resulted to peaks in EPP. […]

本项研究展示了基于GeoB12613-1孔心岩芯，跨越过去300千年的硅藻 productivity（生产力）重建数据，该孔心岩芯位于西印度洋热带地区（IO），该地区温暖且贫营养的表层水体主要源自东部IO。通过应用基于校准群落的生产力指数，发现从300千年前至今，估算的初级生产力（EPP）有所下降，重建的EPP值介于91至246克碳/平方米/年之间。硅藻群落和硅藻成分Sr/Ca比值揭示了生产力变化的三个主要阶段，其中在16万年和4.6万年前发生了主要变化。生产力与水柱层结记录显示出主导的岁差和倾斜周期性，这些周期性似乎控制了研究区域在过去两个冰期-间冰期周期中的古生产力。由于对太阳辐射最大值的响应，贸易风的增强导致热层变浅，进而导致EPP达到峰值。