Rapid shift and millennial-scale variations in Holocene North Pacific Intermediate Water ventilation.
Rapid shift and millennial-scale variations in Holocene North Pacific Intermediate Water ventilation.
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DOI：
10.1073/pnas.1714754115
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发表时间：
2018-05-22
影响因子：
11.1
通讯作者：
Lohmann G
中科院分区：
文献类型：
--
作者：
Lembke-Jene L;Tiedemann R;Nürnberg D;Gong X;Lohmann G
北太平洋拥有广泛的氧气最低区。北太平洋中层水的通风减轻了不受海洋-大气过程影响的温跃层沃茨的缺氧。仪器数据集显示，最近的十年减少O2，但千年尺度的自然变化中层通风可能是大的，并没有很好地理解。我们重建全新世通风变化的一个关键区域（鄂霍次克海）。现代通风和氧气水平是一个相对较新的功能。在温暖比现在早全新世，中层O2浓度减少了25%至50%，具有显着的千年尺度的变化。6000年前的突然通风减少与海洋温度升高、海冰流失和更高的全球化有关，这一点得到了古气候建模结果的证实，为未来的变暖情景提供了限制。太平洋拥有世界海洋中最大的最低含氧区（OMZ），据认为，在未来气候变化的情况下，这一区域将加剧和扩大，对海洋生态系统、海洋地球化学循环和渔业产生重大影响。目前，没有深层通风发生在北太平洋由于持续的盐跃层，但相对较好的含氧地下北太平洋中层水（NPIW）减轻低纬度OMZ的发展。在过去的几十年中，仪器数据显示NPIW中的氧合减少;然而，中深度通风的长期变化可能很大，掩盖了人类对千年尺度自然背景变化的影响。在这里，我们使用来自鄂霍次克海，最重要的北太平洋通风区的古海洋学代理证据，以表明其现代含氧模式是一个相对较新的功能，在六千年前几乎没有通风，构成了一个明显的早中全新世（EMH）阈值或“临界点”。补充的古模型结果同样表明，一个温暖，咸EMH NPIW，从它的现代条件不同。在EMH期间，鄂霍次克海从现代氧化源转变为汇，通过海冰损失，更高的水温和海水化率的组合，抑制了通风。我们估计EMH NPIW的氧合会大幅降低30%至50%，太平洋中层营养盐浓度和碳储量会增加。我们的研究结果（i）意味着，在过去或未来比现在更温暖的条件下，海洋生物地球化学反馈机制可能会改变，甚至切换方向，（ii）提供高纬度北太平洋的中层通风动力学的影响的限制，与大型海洋区域的后果。
The North Pacific hosts extensive oxygen minimum zones. Ventilation of North Pacific Intermediate Water mitigates hypoxia in thermocline waters not under influence of ocean–atmosphere processes. Instrumental datasets show recent decadal decreases in O2, but millennial-scale natural variations in mesopelagic ventilation might be large and are not understood well. We reconstruct Holocene ventilation changes in a key region (Okhotsk Sea). Modern ventilation and O2 levels are a relatively recent feature. In the warmer-than-present Early Holocene, middepth O2 concentrations were 25 to 50% reduced, with significant millennial-scale variations. A sudden ventilation decrease six thousand years ago is linked to higher ocean temperatures, sea ice loss, and higher remineralization, corroborated by results from paleoclimate modeling, providing constraints for future warming scenarios. The Pacific hosts the largest oxygen minimum zones (OMZs) in the world ocean, which are thought to intensify and expand under future climate change, with significant consequences for marine ecosystems, biogeochemical cycles, and fisheries. At present, no deep ventilation occurs in the North Pacific due to a persistent halocline, but relatively better-oxygenated subsurface North Pacific Intermediate Water (NPIW) mitigates OMZ development in lower latitudes. Over the past decades, instrumental data show decreasing oxygenation in NPIW; however, long-term variations in middepth ventilation are potentially large, obscuring anthropogenic influences against millennial-scale natural background shifts. Here, we use paleoceanographic proxy evidence from the Okhotsk Sea, the foremost North Pacific ventilation region, to show that its modern oxygenated pattern is a relatively recent feature, with little to no ventilation before six thousand years ago, constituting an apparent Early–Middle Holocene (EMH) threshold or “tipping point.” Complementary paleomodeling results likewise indicate a warmer, saltier EMH NPIW, different from its modern conditions. During the EMH, the Okhotsk Sea switched from a modern oxygenation source to a sink, through a combination of sea ice loss, higher water temperatures, and remineralization rates, inhibiting ventilation. We estimate a strongly decreased EMH NPIW oxygenation of ∼30 to 50%, and increased middepth Pacific nutrient concentrations and carbon storage. Our results (i) imply that under past or future warmer-than-present conditions, oceanic biogeochemical feedback mechanisms may change or even switch direction, and (ii) provide constraints on the high-latitude North Pacific’s influence on mesopelagic ventilation dynamics, with consequences for large oceanic regions.
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DOI：
10.1016/j.dsr2.2011.05.016
发表时间：
2012-02-01
影响因子：
3
作者：
Gorbarenko, Sergey A.;Harada, Naomi;Ignatiev, Aleksandr V.
通讯作者：
Ignatiev, Aleksandr V.
影响因子：
2.3
作者：
Gorbarenko, Sergey Alexandrovich;Goldberg, Evgenia L'vovich;Ivanova, Elena Diamilevna
通讯作者：
Ivanova, Elena Diamilevna
影响因子：
5.2
作者：
Itaki, T;Ikehara, K
通讯作者：
Ikehara, K
影响因子：
4.3
作者：
Debret, M.;Bout-Roumazeilles, V.;Trentesaux, A.
通讯作者：
Trentesaux, A.
影响因子：
18.3
作者：
Hoogakker, Babette A. A.;Elderfield, Henry;Rickaby, Rosalind E. M.
通讯作者：
Rickaby, Rosalind E. M.