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Gulf Stream density structure and transport during the past millennium
David C Lund1, Jean Lynch-Stieglitz, William B Curry
1Massachusetts Institute of Technology/Woods Hole Oceanographic Institution Joint Program in Oceanography, Woods Hole, Massachusetts 02543, USA. dlund@gps.caltech.edu
Nature
|December 1, 2006
Summary
The Gulf Stream flowed weaker during the Little Ice Age, potentially contributing to North Atlantic cooling. This study used sediment cores to reconstruct past ocean conditions and climate.
Area of Science:
- Oceanography
- Paleoclimatology
- Climate Science
Background:
- The Gulf Stream is a major ocean current transporting heat and water into the North Atlantic.
- Understanding long-term Gulf Stream variability is crucial for climate change predictions.
- Instrumental records are too short to capture multi-century climate fluctuations.
Purpose of the Study:
- To reconstruct past Gulf Stream behavior using geologic archives.
- To investigate the Gulf Stream's role in past climate events like the Little Ice Age.
- To assess the linkage between Atlantic ocean circulation and the hydrologic cycle.
Main Methods:
- Analysis of foraminifera from high-resolution sediment cores in the Florida Straits.
- Reconstruction of cross-current density gradient and vertical current shear.
- Estimation of past volume transport and surface salinity.
Main Results:
- The Gulf Stream exhibited systematically lower cross-current density gradient and vertical current shear during the Little Ice Age (approx. 1200-1850 AD).
- Estimated Little Ice Age volume transport was approximately 10% weaker than present-day values.
- Reduced flow coincided with temperature minima and anomalously high surface salinity, indicating a link to the hydrologic cycle.
Conclusions:
- Diminished oceanic heat transport by the Gulf Stream may have contributed to Little Ice Age cooling in the North Atlantic.
- The study highlights a tight linkage between Atlantic Ocean circulation and the hydrologic cycle over the past millennium.
- Paleoceanographic data provide essential insights into long-term climate dynamics and ocean current behavior.
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