Browsing by Author "Fritz, Hermann M."

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    Modeling Impacts of Energy Extraction from the Gulf Stream System
    Haas, Kevin A.; Yang, Xiufeng; Fritz, Hermann M. (2014-04)
    Ocean currents are an attractive source of clean energy due to their inherent reliability, persistence and sustainability. The Gulf Stream system, particularly the Florida Current, is of interest as a potential energy resource for some coastal states within the USA. However, little is known about the potential impacts of extracting energy from this unconfined flow field. The presented study takes two approaches to evaluate the modifications of the flow field upon extraction of significant energy from the Florida Current. First, the theoretical momentum balance in the Gulf Stream system is examined using the two-dimensional ocean circulation equations based on the assumptions of the Stommel model for subtropical gyres with additional turbine drag formulated and incorporated into the model to represent power extraction by turbines. The impact of the extraction is evaluated by examining the new circulation patterns such as the flow diversion around the turbine extraction region. Secondly, a full numerical simulation of the ocean circulation in the Atlantic Ocean is performed using Hybrid Coordinate Ocean Model (HYCOM) and power extraction from the Florida Current is modeled as additional momentum sink. Various scenarios with different turbine distributions are tested. Effects of power extraction are shown to include flow rerouting from the Florida Strait channel to the east side of the Bahamas. Other effects, such as changes to the residual kinetic energy as well as the water level variations are also evaluated for different scenarios.
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    Stratigraphic evidence of two historical tsunamis on the semi-arid coast of north-central Chile
    DePaolis, Jessica M.; Dura, Tina; MacInnes, Breanyn; Ely, Lisa L.; Cisternas, Marco; Carvajal, Matias; Tang, Hui; Fritz, Hermann M.; Mizobe, Cyntia; Wesson, Robert L.; Figueroa, Gino; Brennan, Nicole; Horton, Benjamin P.; Pilarczyk, Jessica E.; Corbett, D. Reide; Gill, Benjamin C.; Weiss, Robert (Pergamon-Elsevier, 2021-07-21)
    On September 16, 2015, a Mw 8.3 earthquake struck the north-central Chile coast, triggering a tsunami observed along 500 km of coastline, between Huasco (28.5°S) and San Antonio (33.5°S). This tsunami provided a unique opportunity to examine the nature of tsunami deposits in a semi-arid, siliciclastic environment where stratigraphic and sedimentological records of past tsunamis are difficult to distinguish. To improve our ability to identify such evidence, we targeted one of the few low-energy, organic-rich depositional environments in north-central Chile: Pachingo marsh in Tongoy Bay (30.3°S). We found sedimentary evidence of the 2015 and one previous tsunami as tabular sand sheets. Both deposits are composed of poorly to moderately sorted, gray-brown, fine-to medium-grained sand and are distinct from underlying and overlying organic-rich silt. Both sand beds thin (from ∼20 cm to <1 cm) and fine landward, and show normal grading. The older sand bed is thicker and extends over 125 m further inland than the 2015 tsunami deposit. To model the relative size of the tsunamis that deposited each sand bed, we employed tsunami flow inversion. Our results show that the older sand bed was produced by higher flow speeds and depths than those in 2015. Anthropogenic evidence along with 137Cs and 210Pb dating constrains the age of the older tsunami to the last ∼110 years. We suggest that the older sand bed was deposited by the large tsunami in 1922 CE sourced to the north of our study site. This deposit represents the first geologic evidence of a pre-2015 tsunami along the semi-arid north-central Chile coast and highlights the current and continuing tsunami hazard in the region.