Marine isotope stage 4 changes in hydroclimate of southern Portugal

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Date
2023-05
Authors
Oeste, Ryan Andrew
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Wanamaker, Alan D
Johnson, Benjamin W
Denniston, Rhawn F
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Geological and Atmospheric Sciences
Abstract
Marine isotope stage (MIS) 4 spanned ~ 71 - 57 ka and was one of coldest segments of the last glacial period in Europe. Despite the harsh environment, evidence of early hominin migration throughout the Iberian Peninsula expands circa this interval. Regional marine and terrestrial records provide context for the general climate boundary condition at relatively low temporal resolution (centennial or longer) during MIS 4. However, few high resolution (annual to decadal) proxy records from southern Portugal exist, thus our understanding of environmental variability on time scales that impact hominin migration is poorly understood. In this study, we use sub-decadally resolved stable carbon and oxygen isotopes and trace elemental abundances of a stalagmite collected in southern Portugal (Companheira Grande cave) that grew from ~ 69 – 64 ka, coeval with a relatively cool segment recorded in Greenland ice cores (Greenland Stadial - 19.2) to develop a better understanding of environmental variability in southern Portugal. Integrating these new data with regional precipitation records and other sources of the changing climatic boundary conditions during MIS 4 (i.e., greater glacial extent, a more southerly located oceanic polar front, and displaced westerlies and storm track migration) provide possible mechanisms to alter regional hydroclimate. In this study, we investigate the few Iberian stalagmite records that continued growing during MIS 4 and suggest that the regional response to cooling events within the cold period was complex and potentially related to changes in atmospheric circulation and rainfall patterns. Further, an additional goal of this study is to provide a more complete depiction of the regional climatic boundary conditions during MIS 4 focusing on the environmental suitability of early hominins.
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