Orbital-scale thermocline temperature variability in the western equatorial Pacific during the last 370 kyr
Orbital-scale thermocline temperature variability in the western equatorial Pacific during the last 370 kyr
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DOI：
10.1016/j.palaeo.2022.111285
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发表时间：
2022-10
期刊：
影响因子：
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通讯作者：
T. Sagawa;K. Okamura;M. Murayama
中科院分区：
文献类型：
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作者：
T. Sagawa;K. Okamura;M. Murayama
热带次表层环流在调节两半球之间的热量和盐分输送以及海洋-大气相互作用（例如，厄尔尼诺-南方涛动（ENSO）。因此，了解热带温跃层过去的行为对于预测长期的全球气候变化是重要的。在这里，我们提供了一个轨道尺度的温跃层温度（TT）记录的基础上，Mg/Ca测量的南极有孔虫Pulleniatina pulleniatina acuiloculatain沉积物芯从西赤道太平洋（WEP）的过去370 kyr。WEP中的海温和TT之间的垂直温度梯度与热带太平洋纬向海温梯度在长期趋势和垂直信号上均表现出弱的正相关。这两个梯度的关系并不符合现代ENSO变率，这表明TT的长期变化主要取决于另一种机制。谱分析表明，TT变率在垂直和岁差两个波段都有较强的信号。由于在局地太阳辐射下，赤道温度变化率的异常信号很弱，因此，赤道温度变化率的异常信号意味着热带温跃层环流的异常影响。因此，我们的研究结果表明，连接热带和热带外的次表层环流在轨道尺度的热带温跃层变率中起着至关重要的作用。
Tropical subsurface circulation plays a key role in regulating heat and salt transport between the hemispheres, and in ocean–atmosphere interactions (e.g., El Niño-Southern Oscillation; ENSO). Therefore, understanding the past behavior of tropical thermoclines is important for predicting long-term global climate change. Here, we provide an orbital-scale thermocline temperature (TT) record based on Mg/Ca measurements of planktonic foraminiferPulleniatina obliquiloculatain sediment cores obtained from the western equatorial Pacific (WEP) for the last 370 kyr. The vertical temperature gradient between sea surface temperature (SST) and TT in WEP showed weak positive correlations with the tropical Pacific zonal SST gradient in long-term trend and obliquity signal. The relationship of the two gradients does not coincide with modern ENSO variability, suggesting that the long-term TT variation depend primarily on another mechanism. Spectral analysis indicated that TT variability has strong signals in both the obliquity and precession bands. Since the obliquity signal is very weak in local insolation, the significant obliquity in TT variability implies an extratropical influence on tropical thermocline circulation. Therefore, our findings suggest that the subsurface circulation connecting the tropics and extratropics plays an essential role in orbital-scale tropical thermocline variability.