International Journal of Marine Science, 2024, Vol.14, No.3, 182-192 http://www.aquapublisher.com/index.php/ijms 184 3.3 Data assimilation in coastal models Data assimilation is a powerful technique used to integrate observational data into numerical models, thereby improving their accuracy and reliability. This process involves adjusting the model state based on observations to minimize uncertainties and better represent the true state of the system. In the context of coastal circulation models, data assimilation can significantly enhance the understanding of ocean dynamics and climate feedbacks. The study by Widmann et al. (2009) explores the use of data assimilation in palaeoclimatology, demonstrating how combining empirical data with model simulations can provide better estimates of past climate states. Similarly, Ghentet et al. (2011) investigates the implications of data assimilation for land surface models, emphasizing its role in constraining model predictions and understanding biogeochemical cycling. In summary, coastal circulation models, supported by advanced numerical modeling techniques and data assimilation, are vital for understanding the complex interactions between ocean dynamics and climate change. These models provide critical insights into the mechanisms driving coastal circulation and their responses to anthropogenic influences, thereby informing climate predictions and mitigation strategies. 4 Observational Methods 4.1 Remote sensing technologies In assessing coastal circulation mechanisms and their response to climate change, various advanced observational methods were utilized to ensure the accuracy and comprehensiveness of the data. These methods include remote sensing technologies, in-situ measurements, and autonomous observation systems. Remote sensing technologies have played a key role in observing coastal circulation, particularly through the provision of sea surface temperature (SST) and sea surface height (SSH) data from satellite platforms. These data have provided significant support for the analysis of 4D variational data assimilation systems (4D-Var), significantly enhancing the accuracy and predictive capabilities of coastal transport analysis (Moore et al., 2011). High-frequency (HF) radar has also been widely used in coastal ocean observations, providing real-time data on surface currents, with unprecedented coverage and resolution (Manso-Narvarte et al., 2019). Additionally, satellite synthetic aperture radar (SAR) and infrared scanners have been used to map ocean current patterns, such as monitoring circulation in the Gulf of Mexico through thermal imaging (Ladner et al., 2009). The integration of these technologies has made it possible to monitor and predict changes in coastal ecosystems, significantly enhancing the ability to address climate change (Klemas, 2012). 4.2 In-situ measurements In-situ measurement methods include the use of Acoustic Doppler Current Profilers (ADCP), Conductivity, Temperature, and Depth sensors (CTD), and autonomous profiling floats, which are used to obtain sub-surface current speeds and other critical oceanographic parameters. These data are essential for validating and calibrating numerical models. For example, in the study of the California Current System, data from Argo floats, CTDs, and tagged marine mammals have had a significant impact on the analysis and prediction of coastal transport (Moore et al., 2011). 4.3 Autonomous observing systems Autonomous observation systems, such as autonomous gliders and buoy networks, provide continuous and high-resolution ocean data. These systems can cover the entire coastal marine continuum from regional oceans to estuaries and river deltas, greatly increasing the value of observational data. High-resolution models play a crucial role in applications such as monitoring sea level rise, coastal management, and marine ecosystem conservation by connecting and synthesizing these sparse observational data. Additionally, the combination of numerical models and data assimilation methods further enhances the effectiveness of these autonomous observation systems (Manso-Narvarte et al., 2019). 5 Impacts of Climate Change on Coastal Circulation 5.1 Changes in wind patterns Climate change has led to significant alterations in wind patterns, particularly in coastal upwelling ecosystems. Research indicates that increasing greenhouse gas concentrations have intensified upwelling-favorable winds in
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