Paleoclimatology and Paleotempestology Study of Blue Hole, Lighthouse Reef, Belize through Geochemical Proxies

• Main Author: Sorey, Laura Carolyn
• Format: Text
• Language: unknown
• Published: LSU Digital Commons 2014
• Subjects: upwelling; blue hole; ITCZ; NAO; Caribbean; Earth Sciences; North Atlantic; North Atlantic oscillation
• Online Access: https://digitalcommons.lsu.edu/gradschool_theses/1890; https://doi.org/10.31390/gradschool_theses.1890; https://digitalcommons.lsu.edu/context/gradschool_theses/article/2889/viewcontent/uc.pdf

A large Pleistocene age sinkhole, the Blue Hole on Lighthouse Reef off the coast of Belize in the Caribbean Sea is the site of a well preserved sedimentary record that serves as paleoclimatology and paleotempestology archive. The nutrient-starved surface waters of the Blue Hole and the surrounding lagoons are “fertilized” by the seasonal introduction of cool, nutrient-rich waters upwelled from the Caribbean deep water. These waters, which stimulate production of organic materials within the surface waters, carry a heightened isotopic signature that is imparted to the organics resultant from upwelling-induced production. These organics are then incorporated into the predominantly carbonate sediment at the base of the Blue Hole and become part of the sedimentary record. In this study, the δ15N signal of the residual organics from vibracore BZE-BH-SVC4 was analyzed and compared to an age-depth framework for the core in order to identify fluctuations in local upwelling intensity using δ15N as a proxy for relative intensity. It was hypothesized that these shifts in historical upwelling intensity were related to trends hemispheric-scale climatic records that might impact Caribbean atmospheric and oceanic patterns such as the North Atlantic Oscillation (NAO), the Medieval Climate Anomaly (MCA), the Little Ice Age (LIA), tropical cyclone (TC) strikes at the Blue Hole, and the average position of the Intertropical Convergence Zone (ITCZ). Our findings identify three distinct periods of upwelling diminishment/intensification as recorded by the δ15N signal of Blue Hole residual organics. However, it was determined that the timing of the upwelling regimes is largely disconnected from the historical behavior of these large-scale climatic indices.