Antarctic Bottom Water response to Varying Surface Fluxes

• Main Author: Snow, Kate
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Subjects: Physical Oceanography; Antarctic Bottom Water; Global Overturning Circulation; Surface Buoyancy Fluxes; Antarctic; Southern Ocean; The Antarctic; Antarc*
• Online Access: http://hdl.handle.net/1885/110705; https://doi.org/10.25911/5d7635d87dacc; https://openresearch-repository.anu.edu.au/bitstream/1885/110705/4/Snow%20Thesis%202016.pdf.jpg

Antarctic Bottom Water (AABW) is one of the densest and most voluminous water masses of the global ocean. It forms the lower limb of the global overturning circulation and plays an important role in transporting carbon, heat and freshwater sequestered from the atmosphere to the deep ocean. Surface buoyancy fluxes modulate the production of AABW through the formation of Dense Shelf Water (DSW) on the Antarctic continental shelf. The DSW flows down the continental slope as an overflow, entraining ambient Circumpolar Deep Water (CDW), to form AABW. The AABW spreads through the abyssal ocean, influencing global deep stratification, water properties and circulation over centennial, and even millennial, time scales While surface fluxes play a key role in defining AABW production rates, the role of varying surface fluxes in influencing AABW properties and variability remains uncertain. Broad scale observational analysis of AABW processes is hindered by the extreme conditions particular to the Southern Ocean and Antarctic regions, and climate models struggle to accurately represent AABW formation processes. The difficulty climate models have in representing AABW formation originates from challenges in simulating DSW formation and the resultant overflow. Through both observational analysis and novel model development, this thesis provides insight into the role of varying surface fluxes in controlling AABW responses and feedbacks, and the limitations of climate models in representing such responses. A coarse resolution sector model of the Atlantic Ocean is developed to aid in testing the limitations of climate model representation of AABW formation. With realistic forcing and bathymetry, the sector model efficiently emulates climate model processes and allows AABW sensitivity to overflow parameterisations to be assessed. While AABW proves relatively insensitive to most current generation overflow parameterisations, understanding the importance of DSW formation in defining AABW's role in a changing climate remains an ...