Master's Presentation and PhysOcean Lunch Seminar 6 Dec 2023

Wednesday, December 06, 12:30 PM to 01:30 PM PST

Master's Presentation: Song Sangmin

Characterizing high-frequency nutrient dynamics in the Southern Ocean through machine learning on multi-platform observations

Faculty Advisor: Gray

12:30 P.M., 123 Marine Sciences Bldg

Abstract: Ocean productivity relies on the cycling of nutrients by physical processes spanning a wide range of spatial and temporal scales. In turbulent regions like the Southern Ocean, transport processes at small scales may contribute significantly to nutrient delivery to the mixed layer, but remain difficult to observe. Although biogeochemical profiling floats (BGC-Argo) have collected valuable nutrient data from the Southern Ocean, they offer limited sampling resolution because of their 10-day cycling period. Here, we derive new nitrate distributions at 50 times the horizontal resolution of original float data by leveraging information from two Seagliders, which co-sampled alongside a BGC-Argo float during the Southern Ocean Glider Observations of the Submesoscale (SOGOS) deployment in 2019. Our Random Forest (RF) modeling approach reconstructs float nitrate profiles with high accuracy (average error < 2%) and generates novel submesoscale estimates when applied to observations from the rapid-sampling Seagliders. The upscaled distributions reveal filamentary structures that suggest strong mixing between deeper, nutrient-rich waters and the upper ocean. By characterizing mixed layer properties of nitrate from the high-frequency glider data, we investigate the contribution of short-lived, small-scale events to nitrate transport. This approach bridges information from different sampling platforms to extend the capabilities of BGC-Argo, allowing deeper analysis of nutrient delivery at the submesoscale. Moving forward, the RF method may be generalized to predict other tracer distributions in other regions to improve understanding of global biogeochemical cycles at fine resolution.

Zoom Link: https://washington.zoom.us/j/91450766031