Ze Zhang, E. Rohling, David B. Kemp, Zhixiang Wang, Chunju Huang
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引用次数: 0
Abstract
Changes in the thermal conditions of the ocean surface, the interface for air‐sea exchange, are critical for understanding global climate and environmental change. Here we explore the evolution of sea surface temperature (SST) and the meridional SST gradient (STG) at orbital timescales since 4 million years ago (Ma), along with interactions between SSTs, the cryosphere, and the global carbon cycle. We observe orbital eccentricity and obliquity influences on SST evolution and infer that SST changes may have played a key role in atmospheric CO2 and cryosphere changes through key climate transitions in the past 4 Ma. We find a major equator‐to‐pole STG increase in the Northern Hemisphere (NH) close to the initiation of major NH glaciation (at ∼2.7 Ma). In addition, we find substantial increases in the obliquity sensitivity (Sobl) of NH STG at ∼2.7 Ma and in Southern Hemisphere (SH) STG at ∼1 Ma, which may be responses to important expansions of NH and SH ice sheets, respectively. Phase analysis shows that SST changes typically lead global ice volume changes throughout the last 4 Ma. SST changes also lead atmospheric CO2 changes since ∼1.5 Ma, which indicates that SST changes either drove, or directly reflect, processes that changed ocean‐atmosphere carbon exchange and, thus, atmospheric CO2 concentrations. Overall, our study emphasizes that SST changes were a critical component of climate change throughout the last 4 Ma.
海洋表面是海气交换的界面,其热状况的变化对于了解全球气候和环境变化至关重要。在此,我们探讨了自 400 万年前(Ma)以来海面温度(SST)和经向 SST 梯度(STG)在轨道时间尺度上的演变,以及 SST、冰冻圈和全球碳循环之间的相互作用。我们观察到轨道偏心率和倾角对 SST 演变的影响,并推断 SST 的变化可能在过去 4 百万年的关键气候转变中对大气 CO2 和冰冻圈的变化起到了关键作用。我们发现,北半球(NH)的赤道到极地的 STG 大幅增加接近于北半球冰川期的开始(2.7 Ma ∼ 2.7 Ma)。此外,我们还发现北半球 STG 的赤纬敏感度(Sobl)在 2.7 Ma ∼ 1 Ma 处和南半球 STG 的赤纬敏感度在 1 Ma ∼ 1 Ma 处显著增加,这可能分别是对北半球和南半球冰盖重要扩张的响应。相位分析表明,在过去的 4 Ma 期间,SST 的变化通常会导致全球冰量的变化。自 1.5 Ma 以来,SST 的变化也引导着大气 CO2 的变化,这表明 SST 的变化推动或直接反映了海洋-大气碳交换的过程,从而改变了大气 CO2 的浓度。总之,我们的研究强调,在过去 4 Ma 期间,海温变化是气候变化的关键组成部分。