Environmental Science and Engineering Seminar

The abyssal ocean has played a critical role in the sequestration of anthropogenic heat over the past 3 decades, yet the mechanisms controlling the rate of warming are still poorly understood owing to limited data. In this presentation I will discuss two new observational programs that are shedding light on the deep ocean by measuring the "push" and "pull" of the bottom limb of the Meridional Overturning Circulation (MOC). First, year-to-year variability in deep water properties near formation cites around Antarctica are quantified using full depth ocean profiles taken continuously by Deep Argo floats, including under seasonal sea ice. The floats captured the return of the high salinity Ross Bottom Water post 2018. Second, a non-steady state heat budget is explored for the rapidly warming deep Southwest Pacific Basin. The vertical mixing is inferred from the deep ocean heat budget and compared to direct estimates of mixing from full depth chi-pod microstructure temperature measurements taken across the basin during a recent GO-SHIP hydrographic survey using 100 hz thermistors mounted to the rosette. The analysis quantifies the relative contribution of the heat storage (warming) term in the abyssal heat budget and demonstrates the feasibility of collecting a larger scale global microstructure data set using the chi-pods on hydrographic lines.