Reconstruction of North Atlantic upper ocean circulation using Globorotalia truncatulinoides coiling ratios over interglacial intervals of the past 440 kyr
Date
2024
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Publisher
University of Delaware
Abstract
This project applies planktic foraminifera Globorotalia truncatulinoides coiling ratios as a proxy for changes in subtropical gyre dynamics and poleward warm water advection initiated by the North Atlantic Current (NAC) during interglacial intervals of the past 440 thousand years (kyr). I hypothesize that the relative difference form core top variety in G. truncatulinoides coiling ratios across a south to north transect during the interglacial intervals reflect changes in the path of warm water advection and spatial placement of the North Atlantic Current. To assess the spatial variability in coiling dominance I use sediment cores from Integrated Ocean Drilling Program (IODP) Site U1313 (41°N, 32°W), Site U1308 (49°N,24°W), Site U1314 (56°N, 26°W) and Ocean Drilling Program (ODP) Site 980 (55°N, 14°W). The results at each of the study sites show pronounced variation from the core top records throughout the interglacial subintervals of the past 440 kyr. The maxima and minima in the percent G. truncatulinoides (sinistral) at each study site do not always align with the warm versus cold substages. The results suggest enhanced northward warm water advection in the NAC reaching all sites with respect to core top during MIS 1 (~11 ka), cool substages MIS 5d, MIS 7d, and warm substage MIS 11e. During insolation maxima MIS 5e the subtropical advected waters from the NAC flow north-westward indicative of a steeper paleo-oceanic Arctic front. During MIS 11c, results suggest that the northern boundary of the gyre extended farther north than the modern placement as evidenced by the difference from core top data. In sum, the variability in sinistral abundances indicate different NAC configurations during intervals warmer than today.
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Keywords
Globorotalia truncatulinoides, North Atlantic Current, Integrated Ocean Drilling Program, Ocean Drilling Program, Interglacial intervals