Numerical Investigations of the Hydrographic Observations of Chukchi Sea Shelf Using ROMS Model Integrations

Summer-fall hydrographic observations from the northeastern Chukchi Sea frequently exhibit 1) the intrapycnocline intrusions of warm, moderately salty summer waters derived from the Bering Sea, and 2) the circulation around Hanna Shoal caused by the interaction of bottom-trapped winter water and the warm Bering Sea inflow. A 3-D hydrodynamic model ROMS (Regional Ocean Modeling System) is used to investigate the dynamics and structure of these two characteristic hydrographic observations in the Chukchi Sea. The intrusions derived from Bering Sea Water are 10-20 m thick and appear as distinct blobs or horizontal plumes. They occur within the shallow (~20 m depth) pycnocline that separates cold, dilute, surface meltwater from near-freezing, salty, winter-formed waters near the bottom. A simple numerical model suggests that the intrusions result from instabilities of the front that separates meltwater from the Bering Sea Water. Meanders and eddies are generated which transport warm Bering Sea Waters into the pycnocline along either side of the Central Channel. These lateral eddy heat fluxes may play a major role in ablation along the ice edge throughout summer and delay the onset of ice formation in fall.