Influence of the Kuroshio Extension on the Pacific Decadal Precession and Marine environment in the Northeast Pacific
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Citation
Abstract
The North Pacific’s Western Boundary Current’s extension – the Kuroshio Extension (KE) – has decadal variability of both sea surface temperature and sea surface height. The variability of the KE has been linked to a quasi-decadal mode of climate variability in the North Pacific’s atmosphere called the Pacific Decadal Precession (PDP). Research suggests that on decadal time scales, the PDP both responds to and forces the KE. This research investigates the link between the KE and the PDP and how this link extends to the occurrence of Marine Heatwaves (MHWs) in the Northeast Pacific. This dissertation addresses three research questions: 1. What scale of the KE variability influences the downstream atmosphere that links with the Pacific Decadal Precession? 2. What is the influence of Kuroshio Extension variations on marine environmental extremes in the Northeast Pacific Ocean? and 3. How does the Kuroshio Extension’s influence on the North Pacific atmosphere and marine environments change as the global climate changes? To answer these questions, high-resolution ocean and atmospheric data and climate model data were used. In addition, multiple analyses are used, including empirical orthogonal function analysis, spatial correlation and regression analysis, and causality analysis. Through these analyses, it was determined that the second mode of the KE’s large-scale variability links well with the PDP. In particular meridional variability of the KE’s sea surface temperature supports a north-south atmospheric pressure dipole over the North Pacific. This atmospheric modification then modifies the downstream atmospheric pressure patterns through a reduction of zonal propagation of stationary wave energy and an enhancement of the climatological zonal wave heights over North America, which in turn gives rise to the east-west phase of the PDP. Next, it was found that this large-scale KE variability links with the occurrence of MHWs in the northeast Pacific region. An atmospheric teleconnection is proposed between the KE variability and MHWs whereby the KE variability modifies the sea-level pressure in the northeast Pacific region. The physical and biogeochemical changes that the region undergoes during an MHW are linked to the KE variability. Finally, the presence of these links in the high-resolution Community Earth System Model simulation was investigated. Through this analysis, it was determined the link between the KE and the PDP is present in the model’s pre-industrial, historical, and future simulations. This enabled the project to study the future of the KE and the PDP relationship and its influence on the Northeast Pacific MHWs in a changing climate.
Description
2024
License
Attribution 4.0 International