Isotope and Mg/Ca measurements from Cores ME0005A-43JC and 202-1242 of tropical Pacific

Multiproxy geologic records of d18O and Mg/Ca in fossil foraminifera from sediments under the Eastern Pacific Warm Pool (EPWP) region west of Central America document variations in upper ocean temperature, pycnocline strength, and salinity (i.e., net precipitation) over the past 30 kyr. Although evident in the paleotemperature record, there is no glacial-interglacial difference in paleosalinity, suggesting that tropical hydrologic changes do not respond passively to high-latitude ice sheets and oceans. Millennial variations in paleosalinity with amplitudes as high as 4 practical salinity units occur with a dominant period of 3-5 ky during the glacial/deglacial interval and 1.0-1.5 ky during the Holocene. The amplitude of the EPWP paleosalinity changes greatly exceeds that of published Caribbean and western tropical Pacific paleosalinity records. EPWP paleosalinity changes correspond to millennial-scale climate changes in the surface and deep Atlantic and the high northern latitudes, with generally higher (lower) paleosalinity during cold (warm) events. In addition to Intertropical Convergence Zone (ITCZ) dynamics, which play an important role in tropical hydrologic variability, changes in Atlantic-Pacific moisture transport, which is closely linked to ITCZ dynamics, may also contribute to hydrologic variations in the EPWP. Calculations of interbasin salinity average and interbasin salinity contrast between the EPWP and the Caribbean help differentiate long-term changes in mean ITCZ position and Atlantic-Pacific moisture transport, respectively.

采自中美洲以西东太平洋暖池（Eastern Pacific Warm Pool, EPWP）区域沉积物中化石有孔虫的d18O与Mg/Ca多代理地质记录，揭示了过去3万年以来上层海洋温度、密度跃层强度与盐度（即净降水）的变化。尽管古温度记录中存在清晰的冰期-间冰期差异，但古盐度记录并未表现出此类信号，这表明热带水文变化并非被动响应高纬度冰盖与海洋的变化。冰期/冰消期时段，古盐度呈现出振幅高达4实用盐度单位的千年尺度变化，主导周期为3~5千年；而全新世时段其主导周期变为1.0~1.5千年。东太平洋暖池古盐度变化的振幅，远高于已发表的加勒比海与热带西太平洋古盐度记录的振幅。东太平洋暖池的古盐度变化，与大西洋表层、深层以及北极高纬度区域的千年尺度气候变化具有对应关系：冷事件时期古盐度通常偏高，暖事件时期则偏低。除了对热带水文变率具有重要调控作用的热带辐合带（Intertropical Convergence Zone, ITCZ）动力过程外，与热带辐合带动力过程密切相关的大西洋-太平洋水汽输送变化，也可能对东太平洋暖池的水文变化产生贡献。通过计算东太平洋暖池与加勒比海之间的跨盆地基度盐度平均值与跨盆地基度盐度差，可分别区分热带辐合带平均位置的长期变化与大西洋-太平洋水汽输送的变化。