Thesis Chapter 1: Water-mass Transformation in the Weddell Sea

This study investigates the variability of water mass transformation within the Weddell Gyre (WG). The WG is an integral oceanographic feature south of the Antarctic Circumpolar Current due to its role in the global meridional overturning circulation (MOC) and in shaping our climate on time scales of hundreds to thousands of years. The WG serves as a pivotal site for the MOC and for ventilating the ocean because it is the primary origin of the largest volume of water mass in the global ocean, the Antarctic Bottom Water (AABW). It is the densest, coldest and highest-oxygen water in the global ocean, and comprises about 80% of the global deep ocean volume.

Variability in the atmosphere has the potential to modify all aspects of the complex transformations occurring within the WG region. Recent mooring data suggest substantial seasonal and interannual variability of AABW properties exiting the WG. Studies have linked these variabilities between AABW export from the WG to the coupling of large-scale climate forcings affecting wind stress variability that leads to the variability in the WG strength and its density structure. However, the specific thermodynamic mechanisms that link variability in surface forcings to variability in water mass transformations and AABW export remains unclear.

The aim here is to explore WMT variability through Walin’s classic WMT framework and through the lens of ocean model-based reanalysis. Ocean models are a useful tool in studying regions, such as the WG, that lack consistent observations, and for investigating physical mechanisms that drive water mass transformation variability. The three ocean reanalysis products used are ECCOv4r3, SOSE and SODA.

Project has been submitted to Ocean Science at EGUSphere. The preprint doi link is here.

Project Steps: Two parts

Part 1 - Regional (box) Budget

Close box model budget for:

1. Heat ($\theta$)
2. Salinity (S)
3. Reference densities ($\sigma$)

Part 2 - WMT Budget

Similar budget workflow for aforementioned steps, but with moving coordinates.

Part 3 - Timeseries analysis of WMT budget terms in different water mass classes and climate indices

• Climate indices reviewed are ENSO and SAM

  Side note:

• To switch your directory to a different git repository:
• If using SSH: $ git remote set-url origin git@github.com:stb2145/WMT-project.git
• If using HTTPS: $ git remote set-url origin https://github.com/stb2145/WMT-project.git
• To check which repo your directory is connected to:
• git remote -v OR
• git config -l
• To add a whole directory to a repo:
• cd to the directory
• git add *