Export production fluctuations in the eastern equatorial Pacific during the Pliocene-Pleistocene: Reconstruction using barite accumulation rates

Export production is an important component of the carbon cycle, modulating the climate system by transferring CO2 from the atmosphere to the deep-ocean via the biological pump. Here we use barite accumulation rates to reconstruct export production in the Eastern Equatorial Pacific over the past 4.3 Ma. We find that export production fluctuated considerably on multiple time scales. Export production was on average higher (51 gC m-2 yr-1) during the Pliocene than the Pleistocene (40 gC m-2 yr-1), decreasing between 3 to 1 Ma (from 60 to 20 gC m-2 yr-1) followed by an increase over the last million years. These trends likely reflect basin scale changes in nutrient inventory and ocean circulation. Our record reveals decoupling between export production and temperatures on these long (million years) time scale. On orbital time scales export production was generally higher during cold periods (glacial maxima) between 4.3 and 1.1 Ma. This could be due to stronger wind stress and higher upwelling rates during glacial periods. A shift in the timing of maximum export production to deglaciations is seen in the last ~1.1 million years. Results from this study suggest that in the EEP mechanisms that affect nutrient supply and/or ecosystem structure and in turn carbon export on orbital time scales differ from those operating on longer time scales and that processes linking export production and climate modulated oceanic conditions changed about 1.1 million years ago. These observations should be accounted for in climate models to ensure better predictions of future climate change.

出口生产是碳循环的重要组成部分，通过通过生物泵从大气中将CO2从大气中转移到深洋，从而调节气候系统。在这里，我们使用Barite积累率在过去的4.3 MA中重建了东部赤道太平洋的出口产量。我们发现，出口产量在多个时间尺度上大大波动。在上新世期间，出口产量的平均高于更新世（40 GC M-2 YR-1），降低3至1 MA（从60到20 GC M-2年，降低1）随后在过去的百万年中增加了。这些趋势可能反映了营养库存和海洋循环的盆地量表变化。我们的记录揭示了在这些长期（百万年）时间范围内出口产量与温度之间的脱钩。在寒冷期间（冰川最大值）4.3至1.1 MA之间，在轨道时间尺度上的出口通常更高。这可能是由于冰分较强的风应力和较高的上升速率所致。在过去的〜110万年中，最大出口产量的时机转变为脱胶。这项研究的结果表明，在影响养分供应和/或生态系统结构的EEP机制中，以及轨道时间尺度上的碳导出与在较长时间尺度上运行的碳导出不同，并且该过程将出口生产和气候调节状况连接到1.1左右。百万年前。这些观察结果应在气候模型中考虑，以确保对未来气候变化的更好预测。