Date of Award

2025

Degree Type

Thesis

Degree Name

Master of Science in Oceanography

Specialization

Physical Oceanography

Department

Oceanography

First Advisor

Brice Loose

Abstract

The Amundsen Sea is not a known site of bottom water formation, yet the presence of Winter Water reveals the role of deep winter mixing. In this study, we investigate how the production of Winter Water within the Amundsen Sea leads to ventilation by introducing a surface tracer into a regional configuration of MITgcm with ECCO-constrained forcing conditions for the years from 1998 to 2023. Modeled mixed layer depths routinely reached depths of 300 m or deeper in coastal polynyas and along sea ice divergence zones, driven by changes in salinity from sea ice formation and wind stress. The annual average in ventilation flux ranges from -0.34 up to -1.34 Sv, and the largest fluxes occur in early spring leading to the ventilation of up to 45% of the water column and restoring on average 126.7 μmol/kg of oxygen to the deepest mixed layer depths. Seasonal and multiyear trends in ventilation flux correlate with sea surface salinity as well as surface buoyancy flux. Interestingly, the ECCO-constrained model forcing produced a diminishing rate of ventilation of 0.04 Sv or 6.6% per decade, which coincides with progressive freshening and stratification of the modeled surface ocean, especially after 2014. These trends are consistent with observations of decadal trends in other Antarctic seas. These results highlight how ventilation transforms the water column and can impact deep water formation from inter-basin transport between the West Antarctic regional seas.

Available for download on Wednesday, May 27, 2026

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