An aeolian sediment reconstruction of regional wind intensity and links to larger scale climate variability since the last deglaciation from the east coast of southern Africa
An aeolian sediment reconstruction of regional wind intensity and links to larger scale climate variability since the last deglaciation from the east coast of southern Africa
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自南部非洲东海岸上次冰消期以来区域风强度的风成沉积物重建及其与更大规模气候变化的联系
DOI：
10.1016/j.gloplacha.2017.08.002
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发表时间：
2017
影响因子：
3.9
通讯作者：
Finch, J.M.
中科院分区：
文献类型：
--
作者：
Humphries, M.S.;Benitez-Nelson, C.R.;Bizimis, M.;Finch, J.M.
南部非洲几乎没有长期环境记录，因为在那里，大气环流的变化和海面温度的变化相互作用，影响区域气候动态。我们提供了南非东海岸泥炭地过去~23000年以来的岩心下部颗粒尺寸和无机地球化学数据，并研究了区域风活动变化与古气候变异性之间的联系。我们的记录记录了与反映更大规模大气环流模式的区域气候和风型变化有关的风沙通量的巨大变化。在最后一次冰盛期(LGM)观察到的相当高的通量与广泛的干旱化和当地来源地区的扩张有关，这是由于明显转向干燥和凉爽的条件。粒度分布的变化表明，来自MFabeni的风沙记录包括两个主要的末端成员：来自当地的粗颗粒物质和更细颗粒的尘埃成分。成分和模式粒度的显著变化表明，该地区在末次盛冰期的水文变化伴随着风暴频率和风力的增加，我们认为这与西风带向北移动和风力强度增强有关。海洋表面温度(SST)的快速上升和风沙活动在15千卡年后减少近三倍之间的耦合表明，SST的变化及其对南大洋西风带位置和强度的影响是该地区在冰川消融期间的主要气候驱动因素。整个全新世早期，风沙活动显著减少，表明在热带东风气流增强的影响下，区域气候变暖，并建立了更潮湿的条件。我们的记录还记录了全新世中后期气候的更微妙变化，并为南部非洲气候6-4千卡年的干旱阶段提供了支持，以及与厄尔尼诺-南方涛动(ENSO)活动增强相关的气候变异性增加。这项研究有助于了解目前对南半球大气环流模式的认识，并对现有古气候记录稀缺的区域的风沙活动、区域风型和在冰川-间冰期时间尺度上的气候变异性之间的联系提供了新的见解。
Few long-term environmental records are available for southern Africa where shifts in atmospheric circulation and changes in sea surface temperatures interact to influence regional climate dynamics. We present downcore grain size and inorganic geochemistry data covering the last ~ 23,000 years from a peatland on the east coast of South Africa and examine links between shifts in regional wind activity and palaeoclimatic variability. Our record documents substantial variations in aeolian flux associated with changes in regional climate and wind patterns that reflect larger scale atmospheric circulation patterns. Substantially higher fluxes observed during the Last Glacial Maximum (LGM) are linked to widespread aridification and an expansion in local source areas brought about by a clear shift to dry and cool conditions. Variations in grain size distribution reveal that the aeolian record from Mfabeni comprises two dominant end-members; locally-derived coarse-grained material and a more fine-grained dust component. Marked changes in composition and modal grain size suggest that hydrological shifts in the region during the LGM were accompanied by an increase in storm frequency and wind strength that we link to a northward displacement in the westerly wind belt and a strengthening in wind intensity. Coupling between a rapid increase in sea surface temperature (SST) and an approximate three-fold decrease in aeolian activity after 15 kcal yr BP suggests that changes in SST and its effect on the position and intensity of the westerlies in the Southern Ocean was the dominant climatic driver in the region during deglaciation. Substantially lower aeolian activities through the early Holocene indicate a warming in regional climate and the establishment of more humid conditions under the influence of enhanced tropical easterly flow. Our record also documents more subtle changes in climate over the mid to late Holocene and provides support for an arid phase in southern African climate 6–4 kcal yr BP, as well as an increase in climate variability associated with a strengthening in El Niño–Southern Oscillation (ENSO) activity ~ 2 kcal yr BP. The study contributes to current knowledge of atmospheric circulation patterns in the Southern Hemisphere and provides new insight into links between aeolian activity, regional wind patterns and climatic variability over glacial-interglacial timescales for a region where existing palaeoclimate records are scarce.
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