Origin of Millennial-scale Climate Signals in the Northwestern Subtropical Atlantic

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The question of whether millennial-scale climate changes are related to changes in the Earth's orbit (and thus the timing and distribution of solar influence on the Earth's surface) is decades old, but remains the subject of debate in the climate change science community. This research, led by a scientist at the University of Delaware, investigates how short-term climate variability evolved as the periodicity of orbital precession has changed through the Pleistocene, focusing on the last 900,000 years. The central hypothesis is that millennial-scale climate signals in the northwestern subtropical Atlantic are linked to external driving factors, specifically the fourth harmonic of precession. If tropical insolation forcing controls millennial-scale variability, then there should be a reduction in the spectral power of the fourth harmonic (4,800 year) peak as the 19,000 year precession frequency disappears after about 340,000 years ago. As a prerequisite for testing the hypothesis, the work will fill a key gap in the stable oxygen isotope record from the Blake-Bahama Outer Ridge, completing a 1.4 million year long planktonic foraminifer stable isotope record from the Blake Outer Ridge. This fulfills a primary objective of Ocean Drilling Program Leg 172. In terms of broader impacts, the research will provide important information about natural climate variability, and results will be disseminated through public presentations by the lead scientist. Funding also supports a Master's degree student.