Hydroclimate variability from western Iberia (Portugal) during the Holocene: Insights from a composite stalagmite isotope record
Hydroclimate variability from western Iberia (Portugal) during the Holocene: Insights from a composite stalagmite isotope record
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DOI：
10.1177/0959683620908648
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发表时间：
2020-03
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通讯作者：
Diana L. Thatcher;A. Wanamaker;R. Denniston;Y. Asmerom;V. Polyak;Daniel Fullick;C. Ummenhofer;D. Gillikin;Jonathan A. Haws
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文献类型：
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作者：
Diana L. Thatcher;A. Wanamaker;R. Denniston;Y. Asmerom;V. Polyak;Daniel Fullick;C. Ummenhofer;D. Gillikin;Jonathan A. Haws
据预测，在未来变暖的情况下，伊比利亚将受到干旱的影响越来越大。虽然已知该区域在全新世经历了多次干旱加剧的时段，但有必要从伊比利亚获得更多对水文气候敏感的记录，以便从更广泛的角度看待当前和未来的干旱。为此，我们提出了来自葡萄牙西部Buraca Gloriosa(BG)洞穴的六个年代良好且重叠的洞穴的多代理综合记录。这一合成石笋记录中六个石笋之间的一致性表明，气候(而不是洞穴内的过程)影响着洞穴同位素的值。这一记录提供了伊比利亚中西部全新世水文气候的第一个高分辨率、精确年代的陆地记录。BG记录显示，从9.0ka BP到现在，葡萄牙西部的干旱程度持续增加，碳(δ13C)和氧(δ18O)稳定同位素的值都有所上升。这一趋势跟踪了北半球夏季日照和与之平行的伊比利亚边缘海表面温度(SST)的下降。全新世干旱的加剧与哈德利环流的变化和热带辐合带(ITCZ)的南迁是一致的。水气候的百年尺度变化与4ka BP后太阳总辐照度(TSI)的变化一致。几个主要的干旱事件是显而易见的，其中最突出的是以4.2 ka BP为中心，这一特征也在其他伊比利亚气候记录中被记录下来，并与有充分记录的地区文化变迁重合。基本上，更潮湿的条件发生在0.8ka BP到0.15ka BP之间，包括“小冰期”的大部分时间。紧随其后的是日益干旱的今天。这一综合石笋替代记录补充了伊比利亚沿海的海洋记录、伊比利亚内陆的湖泊记录和西班牙北部和南部的洞穴记录，并描绘了伊比利亚水文气候的时空变异性。
Iberia is predicted under future warming scenarios to be increasingly impacted by drought. While it is known that this region has experienced multiple intervals of enhanced aridity over the Holocene, additional hydroclimate-sensitive records from Iberia are necessary to place current and future drying into a broader perspective. Toward that end, we present a multi-proxy composite record from six well-dated and overlapping speleothems from Buraca Gloriosa (BG) cave, located in western Portugal. The coherence between the six stalagmites in this composite stalagmite record illustrates that climate (not in-cave processes) impacts speleothem isotopic values. This record provides the first high-resolution, precisely dated, terrestrial record of Holocene hydroclimate from west-central Iberia. The BG record reveals that aridity in western Portugal increased secularly from 9.0 ka BP to present, as evidenced by rising values of both carbon (δ13C) and oxygen (δ18O) stable isotope values. This trend tracks the decrease in Northern Hemisphere summer insolation and parallels Iberian margin sea surface temperatures (SST). The increased aridity over the Holocene is consistent with changes in Hadley Circulation and a southward migration of the Intertropical Convergence Zone (ITCZ). Centennial-scale shifts in hydroclimate are coincident with changes in total solar irradiance (TSI) after 4 ka BP. Several major drying events are evident, the most prominent of which was centered around 4.2 ka BP, a feature also noted in other Iberian climate records and coinciding with well-documented regional cultural shifts. Substantially, wetter conditions occurred from 0.8 ka BP to 0.15 ka BP, including much of the ‘Little Ice Age’. This was followed by increasing aridity toward present day. This composite stalagmite proxy record complements oceanic records from coastal Iberia, lacustrine records from inland Iberia, and speleothem records from both northern and southern Spain and depicts the spatial and temporal variability in hydroclimate in Iberia.