로스해 해양-빙붕 상호작용을 고려한 수치 모의: 고밀도 대륙붕수의 계절변동 특성과 조절 요인

Abstract

The Ross Sea continental shelf plays a crucial role in ocean circulation and climate regulation by forming Dense Shelf Water (DSW), which contributes to the production of Antarctic Bottom Water (AABW) that ventilates the abyssal Pacific. DSW primarily composed of High Salinity Shelf Water (HSSW), formed through brine release during sea ice formation in coastal polynyas, with additional contributions from mixing with Ice Shelf Water (ISW) originating from basal meltwater beneath ice shelves. The export of AABW from the Ross Sea shelf is compensated by the import of lighter water masses from adjacent regions. Consequently, the characteristics of shelf waters are highly sensitive to these transports, which serve as an effective regulator of shelf water salinity. In this study, we developed a three-dimensional ocean circulation model that incorporates sea ice processes and physical interactions at the ocean-ice shelf interface. This system successfully reproduces the formation and circulation of the major water masses in the Ross Sea, as well as the export of AABW toward the Pacific basin. Using model results, the seasonal variability of DSW volume and underlying processes driving the changes were investigated. Despite active sea ice formation throughout the austral autumn and winter, which supplies HSSW, the volume of DSW decreases during autumn before increasing rapidly in winter. This seasonal contrast is attributed to the strengthening of westward currents in autumn, which enhances the inflow of fresher water from the Amundsen Sea and the export of AABW, ultimately reducing the proportion of dense water masses on the shelf. During winter, as these transport processes weaken, the persistent brine release from active sea ice formation in coastal polynyas leads to an increase in the volume of DSW.