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Abstract
The Arctic has undergone significant warming and rapid sea ice loss due to a series of positive feedbacks known as Arctic amplification. Climate forcing from the tropics contributes to Arctic amplification through multiple pathways, including the radiative and turbulent heat transfers during enhanced moisture transport. Moisture transport from anticyclonic circulation anomalies embedded within Rossby waves plays a substantial role in modulating seasonal sea ice, where this moisture is enhanced during Rossby wave breaking. Poleward moisture transport is projected to increase through the end of the century, concurrent with longitudinal shifts in tropical sea surface temperature (SST) anomalies, leads to uncertainty around long-term tropical contributions to Arctic amplification. This dissertation ascertains the connections of tropical SSTs variability, atmospheric circulation-forced moisture fluxes, and Arctic sea ice by evaluating those relationships within global climate models (GCMs). First, to understand the linkages between tropical SST variability and Arctic atmospheric circulation, a novel potential vorticity-based approach is used to identify Rossby wave break-related blocking events, which are composited to quantify tropical variability impacts on moisture transport. Findings establish that summertime moisture transport in the North Atlantic (NA) during cyclonic wave breaking is greatest when El Niño originates in the Central Pacific (CP). Second, fully coupled GCM large ensemble simulations are utilized to explore the connection between the ENSO variability and sea ice. Although observations confirm a negative correlation between summertime sea ice and CP ENSO in the Canadian Archipelago region, the large ensemble simulations do not adequately capture the extent of this correlation. The CP ENSO teleconnection as demonstrated through 500 hPa geopotential height and moisture anomalies appears to have limited representation in the model. Finally, using the large ensemble simulations, atmospheric blocking events are identified to assess blocking impacts on past and projected sea ice concentration. A novel finding here shows significant increases in the number of projected summer blocking days in the NA, which appears driven by blocking persistence. NA blocking activity leads to substantial spring and summer sea ice loss through increased surface turbulent heat anomalies, where projected increases in blocking may exacerbate sea ice loss through the end of the century.