Abrupt Changes in Atmospheric Circulation During the Medieval Climate Anomaly and Little Ice Age Recorded by Sr‐Nd Isotopes in the Siple Dome Ice Core, Antarctica

IF 3.2 2区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Paleoceanography and Paleoclimatology Pub Date : 2023-03-21 DOI:10.1029/2022PA004543

B. Koffman, S. Goldstein, G. Winckler, M. Kaplan, L. Bolge, P. Biscaye

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引用次数: 0

Abstract

The Southern Hemisphere westerly winds (SWW) play a critical role in global climate, yet their behavior on decadal to centennial timescales, and the mechanisms driving these changes during the preindustrial era, remain poorly understood. We present a decadally resolved record of dust compositions using strontium and neodymium isotope ratios in mineral dust from the Siple Dome ice core, Antarctica, to explore the potential that abrupt changes in SWW behavior occurred over the past millennium. The record spans portions of the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) intervals as defined in the Northern Hemisphere. We find evidence of an abrupt strengthening of atmospheric circulation during the MCA at ∼1125 CE (825 BP) that persisted for about 60 yr, indicating increased influence of Patagonia‐sourced dust. This occurs during an extended positive phase of Southern Annular Mode (SAM+)‐like conditions, characterized by high SWW velocities and a southerly shift of the main wind belt toward ∼60°S, suggesting that rapid changes in SWW strength could occur under the present SAM+ pattern. A second 20 yr long shift in dust compositions during the LIA at ∼1748 CE (200 BP) is coincident with higher dust delivery to Siple Dome, and may indicate increased dust emissions related to glacier activity in Patagonia. The new Siple Dome ice core data set demonstrates that Sr‐Nd isotopes can be used to trace shifts in atmospheric circulation on decadal timescales.

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南极Siple Dome冰芯Sr-Nd同位素记录的中世纪气候异常和小冰期大气环流突变

南半球西风（SWW）在全球气候中发挥着关键作用，但它们在十年到百年时间尺度上的行为，以及在前工业化时代驱动这些变化的机制，仍知之甚少。我们使用南极Siple Dome冰芯矿尘中的锶和钕同位素比例，提供了一份十年解析的尘埃成分记录，以探索SWW行为在过去千年中发生突变的可能性。该记录跨越了北半球定义的中世纪气候异常（MCA）和小冰期（LIA）的部分时间间隔。我们发现有证据表明，在约1125 CE（825 BP）的MCA期间，大气环流突然增强，持续了约60年，表明巴塔哥尼亚来源的沙尘影响增加。这种情况发生在南部环形模式（SAM+）样条件的延长正相位期间，其特征是SWW速度高，主风带向南移动约60°S，这表明在目前的SAM+模式下，SWW强度可能会发生快速变化。在~1748 CE（200 BP）的LIA期间，灰尘成分的第二次20年长的变化与Siple Dome的灰尘输送量增加相一致，这可能表明与巴塔哥尼亚冰川活动有关的灰尘排放量增加。新的Siple Dome冰芯数据集表明，Sr‐Nd同位素可用于追踪大气环流在十年尺度上的变化。

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来源期刊

Paleoceanography and Paleoclimatology Earth and Planetary Sciences-Atmospheric Science

CiteScore

6.20

自引率

11.40%

发文量

107

期刊介绍： Paleoceanography and Paleoclimatology (PALO) publishes papers dealing with records of past environments, biota and climate. Understanding of the Earth system as it was in the past requires the employment of a wide range of approaches including marine and lacustrine sedimentology and speleothems; ice sheet formation and flow; stable isotope, trace element, and organic geochemistry; paleontology and molecular paleontology; evolutionary processes; mineralization in organisms; understanding tree-ring formation; seismic stratigraphy; physical, chemical, and biological oceanography; geochemical, climate and earth system modeling, and many others. The scope of this journal is regional to global, rather than local, and includes studies of any geologic age (Precambrian to Quaternary, including modern analogs). Within this framework, papers on the following topics are to be included: chronology, stratigraphy (where relevant to correlation of paleoceanographic events), paleoreconstructions, paleoceanographic modeling, paleocirculation (deep, intermediate, and shallow), paleoclimatology (e.g., paleowinds and cryosphere history), global sediment and geochemical cycles, anoxia, sea level changes and effects, relations between biotic evolution and paleoceanography, biotic crises, paleobiology (e.g., ecology of “microfossils” used in paleoceanography), techniques and approaches in paleoceanographic inferences, and modern paleoceanographic analogs, and quantitative and integrative analysis of coupled ocean-atmosphere-biosphere processes. Paleoceanographic and Paleoclimate studies enable us to use the past in order to gain information on possible future climatic and biotic developments: the past is the key to the future, just as much and maybe more than the present is the key to the past.