The impacts of climate variability and change on the physical and social-ecological dynamics of the Kuroshio and North Pacific Transition Zone

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Navarra, Giangiacomo Giacomo
Di Lorenzo, Emanuele
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There is growing recognition that climate change is impacting the ocean's western boundary current system. In the Pacific, the Kuroshio and its offshore Kuroshio-Oyashio Extension (KOE) play a central role in the North Pacific climate and impact the social-ecological dynamics of countries that rely on marine ecosystem services (e.g. fisheries). In the thesis, we have used a combination of observations and modeling approaches to understand how past and projected changes in the physical environment of KOE impact social-ecological dynamics linked to the fish industry of Japan and the North Pacific more widely. The thesis is articulated in 3 Chapters. In Chapter 1 we have introduced the problem and the main motivation that lead us to perform this study. In Chapter 2, we analyze the climate variability and change of the KOE over the historical and future projection period 1920-2100. We perform this task using Coupled Model Intercomparison Project 5 (CMIP5) models and a large ensemble from the Community Earth System Model (CESM-LE) output runs. The reason for considering also the CESM-LE runs is that they give the possibility to explore how the variance of the KOE in one model (e.g. a fixed set of dynamics) responds to anthropogenic forcing when compared to the range of natural variability of the CESM-LE model. In this way, we can perform a scenario which goes beyond the time of the observational data. In Chapter 3, we have used an Empirical Dynamical Model approach to characterize the joint statistics of the physical and social-ecological environmental system (SEES) that is relevant to climate and fisheries. To define the states of the SEES we use three international fish databases, (1) the Large Marine Ecosystem (LME, 9,000 fish stocks), (2) the NOAA fishery database referred to as Restricted Access Management (RAM, 300 fish stock) and the (3) the Food and Agriculture Organization (FAO, 1400 fish stocks). Among the approaches used to explore the relationship between KOE’s climate and the SEES response, we have developed a Linear Inverse Model (LIM) approach that has been very successful to simulate and predict the KOE physical climate and its relation to large-scale Pacific dynamics such as El Niño Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), and others.
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