Unraveling the mechanisms and implications of a stronger mid-Pliocene Atlantic Meridional Overturning Circulation (AMOC) in PlioMIP2
Unraveling the mechanisms and implications of a stronger mid-Pliocene Atlantic Meridional Overturning Circulation (AMOC) in PlioMIP2
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DOI：
10.5194/cp-19-61-2023
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发表时间：
2023-01
影响因子：
4.3
通讯作者：
Julia E. Weiffenbach;M. Baatsen;H. Dijkstra;A. S. von der Heydt;A. Abe‐Ouchi;E. Brady;W. Chan;
中科院分区：
文献类型：
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作者：
Julia E. Weiffenbach;M. Baatsen;H. Dijkstra;A. S. von der Heydt;A. Abe‐Ouchi;E. Brady;W. Chan;
抽象的。上新世中期的温暖期（3.264-3.025 Ma）是最近的地质时期，大气中的CO2浓度大约等于我们今天测量的浓度（约3.264 -3.025 Ma）。400 ppm）。海表温度（SST）代理指标表明，在上新世中期，北大西洋的平均变暖相对于前工业化时期，这可能与加强大西洋经向翻转环流（AMOC）。上新世模型相互比较项目第2阶段（PlioMIP 2）的早期结果表明，该集合模拟了上新世中期比工业化前更强的AMOC。然而，没有一致的关系，无论是在上新世中期AMOC和大西洋向北的海洋热输送（OHT）或平均北大西洋SST已经founded. In这项研究中，我们进一步探讨了一个更强的AMOC在上新世中期的驱动程序和后果相比，工业化前的模拟PlioMIP 2。我们发现，所有的模型模拟与封闭的白令海峡和加拿大群岛显示减少淡水运输从北冰洋到北大西洋。这导致了北大西洋和拉布拉多海的盐度增加，这可能与上新世中期更强的AMOC有关。要调查的动力学背后的合奏的总大西洋OHT的变量响应较强的AMOC，我们分开的大西洋OHT成两个组件与翻转环流或风驱动的环流。虽然整体平均的翻转分量的幅度显着增加，在上新世中期，这是部分补偿的减少在北方副热带环流区的环流分量。这表明OHT总量与AMOC之间缺乏联系是由于副热带环流改变了OHT。因此，应单独考虑翻转和环流分量，以更全面地了解OHT对上新世中期AMOC的反应。此外，我们表明，AMOC施加更强的影响，在上新世中期比在工业化前的北大西洋SST，提供了一个可能的解释改善协议的PlioMIP 2合奏平均SST与重建在北大西洋。
Abstract. The mid-Pliocene warm period (3.264–3.025 Ma) is the most recent geological period in which the atmospheric CO2 concentration was approximately equal to the concentration we measure today (ca. 400 ppm). Sea surface temperature (SST) proxies indicate above-average warming over the North Atlantic in the mid-Pliocene with respect to the pre-industrial period, which may be linked to an intensified Atlantic Meridional Overturning Circulation (AMOC). Earlier results from the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2) show that the ensemble simulates a stronger AMOC in the mid-Pliocene than in the pre-industrial. However, no consistent relationship between the stronger mid-Pliocene AMOC and either the Atlantic northward ocean heat transport (OHT) or average North Atlantic SSTs has been found. In this study, we look further into the drivers and consequences of a stronger AMOC in mid-Pliocene compared to pre-industrial simulations in PlioMIP2. We find that all model simulations with a closed Bering Strait and Canadian Archipelago show reduced freshwater transport from the Arctic Ocean into the North Atlantic. This contributes to an increase in salinity in the subpolar North Atlantic and Labrador Sea that can be linked to the stronger AMOC in the mid-Pliocene. To investigate the dynamics behind the ensemble's variable response of the total Atlantic OHT to the stronger AMOC, we separate the Atlantic OHT into two components associated with either the overturning circulation or the wind-driven gyre circulation. While the ensemble mean of the overturning component is increased significantly in magnitude in the mid-Pliocene, it is partly compensated by a reduction in the gyre component in the northern subtropical gyre region. This indicates that the lack of relationship between the total OHT and AMOC is due to changes in OHT by the subtropical gyre. The overturning and gyre components should therefore be considered separately to gain a more complete understanding of the OHT response to a stronger mid-Pliocene AMOC. In addition, we show that the AMOC exerts a stronger influence on North Atlantic SSTs in the mid-Pliocene than in the pre-industrial, providing a possible explanation for the improved agreement of the PlioMIP2 ensemble mean SSTs with reconstructions in the North Atlantic.