Document Type
Thesis
Abstract
High-resolution (700 year time step) oxygen isotope data from planktonic foraminifera in the Western Equatorial Atlantic (ODP Leg 154, Site 925) are used to reconstruct past vertical ocean temperature gradients in the Early Pliocene (4.1 Ma — 4.2 Ma). The difference of oxygen isotope data (A8'*O) from Globigerinoides sacculifer, a mixed-layer dweller, and Neogloboquadrina dutertrei, a thermocline dweller, provides a record of variability in the depth of the thermocline. Thermocline depth varies at periods of 10-kyr, 8-kyr, and 5-kyr. The 10-kyr period is a harmonic of the 23-kyr orbital precession period which forces variability in solar insolation. The 8-kyr period may be caused by some source internal to the ocean-climate system. The cause of the 5-kyr period is unknown; it may be a harmonic of the 23-kyr precession period, a combination tone of precession-induced periods, a modulation of the 1,800 year oceanic tidal cycle, or caused by a source internal to the ocean-climate system. Variability in thermocline depth reflects changes in trade wind strength and differing volumetric ability for ocean heat storage. This millennial scale variability has implications for more frequently intense Early Pliocene northward ocean heat transport as a cause of the high-latitude warmth during the Early Pliocene.
Date Awarded
2003
Department
Geology
Advisor 1
Katharina Billups
Recommended Citation
Niemitz, Matthew D., "Millennial-scale changes of thermocline depth in the Early Pliocene: Evidence from the western equatorial Atlantic Ocean" (2003). Geology Senior Theses. William & Mary. Paper 116.
https://scholarworks.wm.edu/geologyseniors/116
