UC San Diego

This dissertation investigates the mechanisms which modulate the transport and transformation of water masses using observational techniques. Observations were made in the Solomon Sea during the Southwest Pacific Ocean Circulation and Climate Experiment (SPICE) (Chapters 2 & 3) and in the Canada Basin during the ArcticMix and Stratified Ocean Dynamics of the Arctic (SODA) experiments (Chapter 4).

The Solomon Sea connects the subtropical and equatorial Pacific, transporting water masses that supply the equatorial undercurrent and support eastern equatorial primary productivity. Chapter 2 investigates the spatial patterns of vertical diffusiv- ity and dissipation of kinetic energy in the Solomon Sea, indirectly estimated from shipboard and Argo observations. Across the Solomon Sea, dissipation is strong rel- ative to global estimates over the same latitudinal band and decreases by 2-3 orders of magnitude from the surface to 2000 m depth. Mixing along intermediate and deep isopycnals is indicative of tidally driven mixing. The sources of energy for thermocline mixing are temporally and spatially variable and observations do not resolve a clear relationship at this time.

Chapter 3 details the first, full-depth mooring transport time series from all three exit passages of the Solomon Sea: Vitiaz Strait, St. Georges Channel, and Solomon Strait. Vitiaz Strait is confirmed to supply the majority of transport (53%) toward the equator and is relatively steady in time. Transport through Solomon Strait supplies 34% of the total mean transport but dominates the total transport temporal variability. Thermocline transport variability in Solomon Strait is well described by the arrivals of the off-equatorial Rossby waves. St. Georges channel, which is typically not resolved in global and regional models due to the narrow channel width, supports 13% of total transport and seasonally exchanges water between the Bismarck Sea and Solomon Sea.

The Canada Basin has experienced greater than predicted losses in summer sea ice extent and the responsible dynamics are still an active area of research. Chapter 4 studies the influence of submesoscale dynamics on the transport of heat in the Canada Basin summer mixed layer using novel observations of mixed layer temperature and salinity from a bow chain. Simultaneous microstructure observations find asymmetric mixing across surface fronts. Horizontal wavenumber spectra from in-situ and satellite observations are used to infer upper ocean dynamics and evaluate satellite sea surface temperature products.