Hydroclimate variability in the Madagascar and Southeast African summer monsoons at the Mid- to Late-Holocene transition
Hydroclimate variability in the Madagascar and Southeast African summer monsoons at the Mid- to Late-Holocene transition
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DOI：
10.1016/j.quascirev.2022.107874
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发表时间：
2023-01
影响因子：
4
通讯作者：
N. Scroxton;S. Burns;D. McGee;L. Godfrey;Lovasoa Ranivoharimanana;P. Faina;Benjamin H. Tiger
中科院分区：
文献类型：
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作者：
N. Scroxton;S. Burns;D. McGee;L. Godfrey;Lovasoa Ranivoharimanana;P. Faina;Benjamin H. Tiger
中晚全新世过渡期的4.2ka事件通常被认为是全新世最大和最好的记录的突发气候扰动之一。这一事件在地中海和中东地区表现得最为明显，表现为一个区域性的干旱异常，从4.26 kyr BP突然开始，一直持续到3.97 kyr BP。然而，这一区域性干旱的影响往往扩大到其他区域，有时甚至扩大到全球。特别是，性质和空间范围的4.2 ka事件在热带地区尚未建立。在这里，我们提出了一个新的石笋稳定同位素记录Anjohikely，马达加斯加西北部。生长于距今5.22 ~ 2.00 kyr BP之间的石笋AK 1显示出距今4.31 ~ 3.93 kyr BP（±40 ~ ± 35 yr）之间的间断，复制了附近Anjohibe的另一石笋中的间断，因此表明在中全新世至晚全新世的过渡期出现了显著的干燥。这一结果是相反的潮湿条件下的8.2 ka的事件，从根本上不同的强迫机制。马拉维湖、马索科湖和毛里求斯的塔托斯盆地的沉积物岩心也记录了干旱状况，这些地区也位于东南非洲季风区。然而，没有显着的事件记录在北方（赤道东非）和东部（罗德里格斯岛）的季风域外围，而湿事件记录在沉积物芯在湖Muzi和Mkhuze三角洲南部。空间格局与现代降水异常格局基本一致，与弱莫桑比克海峡槽和夏季热带辐合带位置偏北相关联。在年龄误差范围内，观测到的气候异常峰值与4.2ka事件重叠。然而，区域水文变化始终开始早于4.26 kyr BP事件的发生。逐渐水文变化经常开始约4.5 kyr BP，提出疑问，是否任何连贯的区域水文变化仅仅是巧合的4.2 ka事件或全球气候异常的一部分。
The 4.2 ka event at the Mid- to Late-Holocene transition is often regarded as one of the largest and best documented abrupt climate disturbances of the Holocene. The event is most clearly manifested in the Mediterranean and Middle East as a regional dry anomaly beginning abruptly at 4.26 kyr BP and extending until 3.97 kyr BP. Yet the impacts of this regional drought are often extended to other regions and sometimes globally. In particular, the nature and spatial extent of the 4.2 ka event in the tropics have not been established. Here, we present a new stalagmite stable isotope record from Anjohikely, northwest Madagascar. Growing between 5.22 and 2.00 kyr BP, stalagmite AK1 shows a hiatus between 4.31 and 3.93 kyr BP (±40 and ± 35 yrs), replicating a hiatus in another stalagmite from nearby Anjohibe, and therefore indicating a significant drying at the Mid- to Late-Holocene transition. This result is the opposite to wet conditions at the 8.2 ka event, suggesting fundamentally different forcing mechanisms. Dry conditions are also recorded in sediment cores in Lake Malawi, Lake Masoko and the Tatos Basin on Mauritius, also in the southeast African monsoon domain. However, no notable event is recorded at the northern (equatorial East Africa) and eastern (Rodrigues) peripheries of the monsoon domain, while a wet event is recorded in sediment cores at Lake Muzi and Mkhuze Delta to the south. The spatial pattern is largely consistent with the modern rainfall anomaly pattern associated a with weak Mozambique Channel Trough and a northerly austral summer Intertropical Convergence Zone position. Within age error, the observed peak climate anomalies overlap with the 4.2 ka event. However regional hydrological change consistently begins earlier than a 4.26 kyr BP event onset. Gradual hydrological change frequently begins around 4.5 kyr BP, raising doubt as to whether any coherent regional hydrological change is merely coincident with the 4.2 ka event or part of a global climatic anomaly.