Variability and Dynamics of the Coastal Circulation along the West Antarctic Peninsula (WAP)

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TheWest Antarctic Peninsula (WAP) hosts a rich biological community and has undergone significant changes in both oceanic and climatic environments since the later half of the twentieth century. The complexity of the WAP environment is highlighted by its sensitivity to the dynamics of coastal circulation, which is pivotal in distributing and modulating key oceanographic properties such as salinity, temperature, and biogeochemical constituents, crucial for the vitality of local and surrounding ecosystems. The intricate interplay between various dynamics and the coastal circulation makes understanding the structure of the circulating pattern in the WAP critical, thereby forming the focal point of this thesis. High-resolution numerical model outputs, available observational data sets, and reanalysis products are used in this study. Results first reveal a strong along-shore water exchange between the warm and cold shelves along the WAP in Chapter 3. Seasonal and interannual variabilities are observed in the along-shore water exchange processes. Summer is characterized by the intrusion of warm Circumpolar Deep Water (CDW) into the Bransfield Strait, contrasted by winter’s influx of colder Weddell-sourced water into central WAP. Under downwelling-favorable wind conditions, cold water intrusion intensifies, cooling the warm shelf by approximately 0.5◦C. Additionally, the along-shore coastal current circulation system and the freshwater transport have been analyzed in Chapters 4 and 5. The coastal current along the WAP is semi-continuous, the first Coastal Current extends from the Weddell Sea to Anvers Island, where the Antarctic Coastal Current (AACC) emerges and flows southwestward. Glacier meltwater dominates the AACC meltwater input north of Marguerite Bay. South of Marguerite Bay, ice shelf meltwater becomes comparable to, and eventually exceeds, glacier input. Approximately 46 Gt/year of glacier meltwater and 57 Gt/year of ice shelf meltwater carried by AACC at Charcot Island, respectively. Strong buoyancy input is the primary mechanism generating the AACC, with significant wind impact that strengthens the coastal current under favorable downwelling conditions. Moreover, export of freshwater offshore from the buoyant plume persists, predominantly driven by mesoscale, anticyclonic eddies—which comprise 77% to 80% of the total—resulted from baroclinic and barotropic instabilities. Eddies vary in size from 5 to 40 km in radius and transport water offshore especially south of Marguerite Bay where exists massive melting. The offshore freshwater export, driven by eddies, can exceed the onshore wind-driven Ekman transport, reaching up to approximately 0.11 Sv. The exported freshwater strongly modulate the freshwater content variability in the outer shelf. Overall, this dissertation reveals the importance of investigating coastal circulation over the WAP continental shelf and its diverse dynamics for a deeper understanding of local property distributions and the oceanic environment.
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