Strengthening Atlantic Inflow Across the Mid-Pleistocene Transition
Strengthening Atlantic Inflow Across the Mid-Pleistocene Transition
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DOI：
10.1029/2020pa004200
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发表时间：
2021-04-01
影响因子：
3.5
通讯作者：
Knorr, Gregor
中科院分区：
文献类型：
--
作者：
Barker, Stephen;Zhang, Xu;Knorr, Gregor
在中更新世过渡(MPT)期间，北半球冰盖的发展更大、持续时间更长，与全球变冷相吻合。在这里，我们显示了东北大西洋的表层海水实际上在这个区间(类似于1.2-0.8 Ma)变暖，我们认为这反映了通过北大西洋流(NAC)向东北方向进入北欧海(大西洋流入)的热量和水汽输送的增加。我们认为，在海洋同位素第28阶段(类似于995ka)期间，北冰洋西北部和东南部边缘(分别)同时变冷和变暖，反映了随着大西洋流入的增加，北部冰盖的持续性增加。随着北方冰盖不断向南扩散，东北大西洋从接近40 KYR到接近100 KYR的周期发生了历时变化；在NAC的西北部，第一个“100 KYR”循环发生在终止12之前(类似于960 ka)，而在NAC的东南边缘，这一转变类似于后来的100 KYR。探索性气候模型模拟表明，此时大西洋流入的增加可能会加速冰盖的增长，因为先前存在的中等大小的冰盖允许降水增加的积极影响超过融化。此外，我们认为，一旦超过临界大小阈值，高纬度冰盖缺乏重要的水汽来源，MPT后冰盖对通过大西洋流入的水汽输送的依赖可能最终导致它们对日照强迫的明显脆弱性。
The development of larger and longer lasting northern hemisphere ice sheets during the mid-Pleistocene Transition (MPT) coincided with global cooling. Here, we show that surface waters of the north-eastern Atlantic actually warmed across this interval (similar to 1.2-0.8 Ma), which we argue reflects an increase in the north-eastward transport of heat and moisture via the North Atlantic Current (NAC) into the Nordic Seas (the Atlantic Inflow). We suggest that simultaneous cooling and warming along the north-western and south-eastern margins (respectively) of the NAC during Marine Isotope Stage 28 (similar to 995 ka) reflected the increasing persistence of northern ice sheets as Atlantic Inflow increased. This resulted in a diachronous shift from similar to 40 to similar to 100 kyr cyclicity across the North East (NE) Atlantic as the growing influence of northern ice sheets spread southwards; to the north-west of the NAC the first "100 kyr" cycle preceded Termination 12 (similar to 960 ka), while on the south-eastern margin of the NAC the transition occurred similar to 100 kyr later. Exploratory climate model simulations suggest that increasing Atlantic Inflow at this time could have accelerated ice sheet growth because pre-existing moderately sized ice sheets allowed the positive effect of increasing precipitation to outpace melting. In addition, we propose that the dependence of post-MPT ice sheets on moisture transport via the Atlantic Inflow may ultimately contribute to their apparent vulnerability to insolation forcing once a critical size threshold is crossed and high latitude ice sheets become starved of a vital moisture source.