Impact of Western Pacific Warm Pool variability on regional and global climate evolution during the late Miocene and early Pliocene

作为地球上最温暖的水体，西太平洋暖池（WPWP）强烈影响着El Niño南方涛动和亚洲-澳大利亚季风系统的动力学，影响着行星尺度的大气环流、大气加热和热带水文。迄今为止，关于热带太平洋气候对温室气体浓度和海平面上升的响应存在相当大的不确定性，这是由于我们对WPWP过去变率的了解有限，以及数据和模式模拟的结果相互矛盾。在现今WPWP西南缘（U1482地点，15°3.32 S, 120°26.10 E，水深1466 m），首次获得了扩展的（沉降速率约6 cm/kyr）中新世至上新世半深海序列。这个富含碳酸盐和粘土的序列为记录不同气候背景状态下WPWP的温度和降水变化提供了理想的档案，并更好地约束了与辐射强迫（CO2和日照）变化相关的气候敏感性。利用高分辨率海洋温度和盐度重建（基于氧同位素和主要不变的、玻璃状浮游生物和中间底栖有孔虫的Mg/Ca分析）和xrf扫描仪衍生的季风径流记录，我们提出：1)在轨道时间尺度上监测WPWP空间范围与高纬度气候变化的关系；2)探讨赤道至极温度梯度变化与澳大利亚季风长期演变的关系；3)评估热带太平洋海温梯度在强烈的全球变冷和变暖期间的变化；4)评估中新世晚期和上新世早期气候逆转期间中水作为高纬度气候变化缓冲的作用。我们的项目将集中在中新世晚期到上新世早期，这代表了一个地质上最近的，相对温暖的气候阶段，被认为是地球未来条件的潜在模拟。这段时间内发生了几次根本性的气候重组，为探索比现在更温暖的地球上的气候-碳循环动力学，以及研究WPWP变化对亚洲-澳大利亚季风系统演变和赤道太平洋纬向过程（例如过去的厄尔尼诺Niño状态）的影响提供了一个具有挑战性的机会，从而有助于指导模式和限制气候变化和敏感性的预测。

As the warmest water body on the planet, the Western Pacific Warm Pool (WPWP) strongly influences the dynamics of the El Niño Southern Oscillation and the Asian-Australian monsoon system, affecting planetary-scale atmospheric circulation, atmospheric heating, and tropical hydrology. To date, there is considerable uncertainty regarding the response of the tropical Pacific climate to rising greenhouse gas concentrations and sea level due to our limited understanding of the WPWP past variability and conflicting results from data and model simulations.During IODP Expedition 363, an extended (sedimentation rate: ~6 cm/kyr), undisturbed upper Miocene to lower Pliocene hemipelagic succession was retrieved for the first time at the southwestern edge of the present day WPWP (Site U1482, 15°3.32 S, 120°26.10 E, water depth: 1466 m). This carbonate- and clay-rich sequence provides an ideal archive to document temperature and precipitation variations in the WPWP under different climate background states and to better constrain climate sensitivity in relation to changes in radiative forcing (CO2 and insolation). Using a combination of high-resolution ocean temperatures and salinity reconstructions (based on oxygen isotope and Mg/Ca analyses of mainly unaltered, glassy planktonic and intermediate water benthic foraminifers) and XRF-scanner derived monsoonal runoff records, we propose: 1) to monitor variations in the spatial extent of the WPWP in relation to high-latitude climate change on orbital timescales; 2) to investigate the relationships between changes in the Equator-to-pole temperature gradient and the long-term evolution of the Australian monsoon; 3) to assess changes in the zonal SST gradient of the tropical Pacific Ocean during intense, global cooling and warming episodes and 4) to evaluate the role of intermediate waters as a buffer of high-latitude climate variations during late Miocene and early Pliocene climate reversals.Our project will focus on the late Miocene to early Pliocene period, which represents a geologically recent, relatively warm climate phase that is considered a potential analog of future conditions on Earth. This interval was marked by several episodes of fundamental climate re-organization, offering a challenging opportunity to explore climate-carbon cycle dynamics on a warmer-than-today Earth as well as to investigate the impact of WPWP variations on the evolution of the Asian-Australian monsoon system and on zonal equatorial Pacific processes (e.g. past El Niño state) and, thus, to help guide models and constrain predictions of climate change and sensitivity.