Numerical investigations of the hydrography, dynamics, and ice distributions of Chukchi Sea shelf

Thesis (Ph.D.) University of Alaska Fairbanks, 2019Warm, moderately salty Bering Sea Water (BSW) carried into the Chukchi Sea through Bering Strait provides an oceanic heat flux for melting sea ice comparable to that of the solar heat flux. Intrusions of BSW transport heat and nutrients via intrapycnocline eddies vertically beneath the sea ice and laterally across structural fronts near the ice edge, setting up hydrographic features important to ice edge communities and the seasonal evolution of the ice melt-back. However, the intrapycnocline eddy dynamics and associated hydrography near the fronts have not previously been well described or characterized. Three numerical models using the Regional Ocean Model System (ROMS) are integrated to systematically investigate the importance of the intrapycnocline eddy field and the factors that affect its dynamics. The models suggest that the heat transported by eddies depends on frontal stratification, which is influenced primarily by the Bering Strait inflow discharge and salinity. The eddy field is also indirectly modified by the sea surface height, which varies with strong winds. Two frontal zones near the ice edge are identified according to the model-derived hydrographic structures and eddy dynamics: the Shelf Water Transition Zone (SWTZ) and the Melt Water Transition Zone (MWTZ). Improved understanding of these frontal zones will benefit future research of the ice edge ecosystem. Our models show a noticeable effect of strong wind events on ice edge displacement and vertical transports, both of which may be important to primary production in the frontal zones. Changing winds associated with increasing sea surface temperatures could alter the manifestation of the processes highlighted in this study.BOEM, US Dept. of Interior, and ConocoPhillips Alaska Company, Shell Exploration and Production Company, and Statoil USA E+P, IncIntroduction -- Chapter 1. Lateral mixing across ice meltwater fronts of the Chukchi Sea shelf -- Chapter 2. Assessing the role of oceanic heat fluxes on ice ablation of the central Chukchi Sea shelf -- Chapter 3. Impacts of Short-Term Wind Events on Chukchi Hydrography and Sea Ice Retreat -- Conclusions -- Future perspectives