Causes of ice age intensification across the Mid-Pleistocene Transition.
Causes of ice age intensification across the Mid-Pleistocene Transition.
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DOI：
10.1073/pnas.1702143114
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发表时间：
2017-12-12
影响因子：
11.1
通讯作者：
Wilson PA
中科院分区：
文献类型：
--
作者：
Chalk TB;Hain MP;Foster GL;Rohling EJ;Sexton PF;Badger MPS;Cherry SG;Hasenfratz AP;Haug GH;Jaccard SL;Martínez-García A;Pälike H;Pancost RD;Wilson PA
相互矛盾的几组假说强调了冰盖或大气二氧化碳(二氧化碳)在导致中更新世过渡期间冰河时代周期∼1 Mya持续时间和严重程度增加方面的作用。我们记录了早期的MPT二氧化碳循环，它们比最近的冰河时代循环要小。通过模式模拟，我们将这归因于MPT后冰期沙尘的增加及其对南大洋生产力的影响。详细的分析揭示了二氧化碳气候强迫的重要性，它是一种强大的正反馈，放大了最初由冰盖动态变化引发的MPT气候变化。这些发现提供了对地球系统内气候、海洋和冰盖紧密耦合的洞察。在中更新世过渡期(MPT；1,200-800 Kya)，地球轨道节奏的冰期周期加剧，从∼40,000(∼40 Ky)延长到∼100 Ky，并变得明显不对称。事实证明，用现有的观测数据很难验证大气二氧化碳水平变化是MPT的驱动因素的假设。在这里，我们使用轨道分辨的硼同位素二氧化碳数据来表明，从∼43到∼75μ大气层，冰川和间冰期二氧化碳的差异增加，主要是因为冰川二氧化碳水平较低。通过碳循环模拟，我们将这一下降主要归因于冰川高峰期南大洋沙尘携带的大量铁肥的启动。我们还观察到海平面和与二氧化碳相关的气候强迫之间关系的双重陡化，这表明支配冰盖稳定性的动力发生了变化，例如冰下浮冰或半球间冰盖相位锁定的移除预期的变化。我们认为，无论是冰盖动力学还是孤立的二氧化碳变化都不能解释MPT。相反，我们推断，MPT是由冰盖动力学的变化启动的，MPT后更长、更深的冰期是由于较大的冰盖导致与南大洋尘埃肥沃有关的碳循环反馈而维持的。
Conflicting sets of hypotheses highlight either the role of ice sheets or atmospheric carbon dioxide (CO2) in causing the increase in duration and severity of ice age cycles ∼1 Mya during the Mid-Pleistocene Transition (MPT). We document early MPT CO2 cycles that were smaller than during recent ice age cycles. Using model simulations, we attribute this to post-MPT increase in glacial-stage dustiness and its effect on Southern Ocean productivity. Detailed analysis reveals the importance of CO2 climate forcing as a powerful positive feedback that magnified MPT climate change originally triggered by a change in ice sheet dynamics. These findings offer insights into the close coupling of climate, oceans, and ice sheets within the Earth System. During the Mid-Pleistocene Transition (MPT; 1,200–800 kya), Earth’s orbitally paced ice age cycles intensified, lengthened from ∼40,000 (∼40 ky) to ∼100 ky, and became distinctly asymmetrical. Testing hypotheses that implicate changing atmospheric CO2 levels as a driver of the MPT has proven difficult with available observations. Here, we use orbitally resolved, boron isotope CO2 data to show that the glacial to interglacial CO2 difference increased from ∼43 to ∼75 μatm across the MPT, mainly because of lower glacial CO2 levels. Through carbon cycle modeling, we attribute this decline primarily to the initiation of substantive dust-borne iron fertilization of the Southern Ocean during peak glacial stages. We also observe a twofold steepening of the relationship between sea level and CO2-related climate forcing that is suggestive of a change in the dynamics that govern ice sheet stability, such as that expected from the removal of subglacial regolith or interhemispheric ice sheet phase-locking. We argue that neither ice sheet dynamics nor CO2 change in isolation can explain the MPT. Instead, we infer that the MPT was initiated by a change in ice sheet dynamics and that longer and deeper post-MPT ice ages were sustained by carbon cycle feedbacks related to dust fertilization of the Southern Ocean as a consequence of larger ice sheets.
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DOI：
10.1073/pnas.1702143114
发表时间：
2017-12-12
影响因子：
11.1
作者：
Chalk TB;Hain MP;Foster GL;Rohling EJ;Sexton PF;Badger MPS;Cherry SG;Hasenfratz AP;Haug GH;Jaccard SL;Martínez-García A;Pälike H;Pancost RD;Wilson PA
通讯作者：
Wilson PA
影响因子：
5
作者：
Fantle, Matthew S.;DePaolo, Donald J.
通讯作者：
DePaolo, Donald J.
DOI：
10.1016/0198-0149(90)90004-f
发表时间：
1990-05-01
期刊：
DEEP-SEA RESEARCH PART A-OCEANOGRAPHIC RESEARCH PAPERS
影响因子：
--
作者：
DICKSON, AG
通讯作者：
DICKSON, AG
影响因子：
3.6
作者：
ARCHER, D
通讯作者：
ARCHER, D
影响因子：
--
作者：
Clark, PU;Pollard, D
通讯作者：
Pollard, D