Cross-Slope exchange processes and AABW production in the Ross Sea
Abstract
The polar regions play a crucial role in the climate system through complex physical processes. In particular, some of these processes lead to the formation of Antarctic Bottom Water (AABW), the most voluminous water mass in the deep ocean, which supplies the lower limb of the Global Overturning Circulation and ventilates the deep ocean with oxygen while storing CO2 and heat for hundreds of years. The Ross Sea is a crucial area, with about 25% of AABW produced in its western part through processes occurring on the continental shelf. Here, especially along the shelf break, the strong diurnal tide plays a key role in controlling the outflow and production of AABW, as well as enhancing mixing through the Coastal Trapped Waves (CTWs). These waves are generated by the interaction of tidal currents with the topography along the troughs.
The strong tides also control the intrusion of Circumpolar Deep Water (CDW), a significant water mass for AABW production. Variations in CDW intrusion are closely linked to changes in ice shelf melting rates. Understanding the processes that drive both AABW outflow and CDW intrusion is essential for advancing knowledge of global ocean circulation, the biogeochemical cycling of carbon and nutrients, and the mass balance of ice sheets.
Using the time series data provided by the instruments installed on Mooring G (MORSea project), located at the mouth of the Drygalski Trough, my project aims to enhance understanding of the potential drivers of mixing, production, and outflow of AABW, with a focus on the role of tides and CTWs.
Preliminary analysis has shown that the period around the summer solstice, between December and January, experiences the highest velocity peaks, reaching up to 1.26 m/s. Additionally, three main periods have been identified: a 14-day cycle related to the spring-neap tidal cycle, one corresponding to the diurnal tide, and an interesting inertial period that may be linked to the presence of CTWs.
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