The Eastern tropical Pacific holds extensive oxygen minimum zone (OMZ) areas where pelagic denitrification occurs. Sedimentary nitrogen isotopes are believed to record their denitrification history, which provides indirect evidence for the past extent of the upper ocean oxygen depletion. We present a new high-resolution sedimentary δ¹⁵N record of ODP Site 1242 located in the Eastern Equatorial Pacific during the Mid-Pleistocene Transition. The sedimentary record shows increased (decreased) denitrification during interglacial (glacial) periods and a substantial 41 kyr power. Comparing the sedimentary nitrogen signal with proxies for organic carbon supply and paleoxygenation indicates a decoupling of the denitrification from local productivity and bottom water oxygenation. We claim that this feature is a response to the extratropical ventilation of the subthermocline waters. Increased glacial AAIW influence might have provided the EEP with oxygenated and nutrient-rich waters, explaining the decreased glacial denitrification rates observed in Site 1242 and other OMZs records. Qualitative inferences about the vertical oxygen structure depict an extensive deoxygenated glacial EEP. This scenario might have contributed to the storage of the carbon captured during the glacials of the MPT.

东热带太平洋拥有广泛的氧气最低区 (OMZ) 区域，发生远洋反硝化作用。沉积氮同位素被认为记录了它们的反硝化历史，这为过去海洋上层氧气消耗的程度提供了间接证据。我们提出了一个新的高分辨率沉积 δ ¹⁵中更新世过渡期间位于东赤道太平洋的 ODP 站点 1242 的 N 记录。沉积记录显示间冰期（冰期）期间反硝化作用增加（减少），并且功率为 41 kyr。将沉积氮信号与有机碳供应和古氧化的代理进行比较，表明反硝化作用与当地生产力和底水氧化作用脱钩。我们声称这一特征是对亚温跃层水域温带通风的响应。冰川 AAIW 影响的增加可能为 EEP 提供了含氧和营养丰富的水，解释了在 Site 1242 和其他 OMZ 记录中观察到的冰川反硝化率降低。关于垂直氧结构的定性推断描绘了一个广泛的脱氧冰川 EEP。