| Summary: | Palmer Deep Canyon (PDC) is a submarine canyon located along the Western Antarctic Peninsula. The region is considered a biological hotspot due to the high number of marine predators during the austral summer. The mechanisms that drive this hotspot, however, are poorly understood. Glider and satellite-based temperature and chlorophyll measurements in the region previously suggested that upwelling of warm, nutrient-rich water was fueling phytoplankton blooms in the area. These phytoplankton blooms would support Antarctic krill (Euphausia superba) in the region who feed on the phytoplankton blooms occurring over the canyon, providing a reliable food source for marine predator populations. ☐ Gliders deployed in the austral summer of 2015, however, illustrate that upwelling of mUCDW does not occur over PDC. Spatial decorrelation analysis of surface and deep (100 m) water masses suggest PDC is a two-layer system: a surface mixed layer that does not feel the presence of the canyon, and a deep subsurface layer that is heavily influenced by the canyon. Within this subsurface layer, isopycnal doming was present over the deepest and eastern flanks of the canyon, suggesting that subsurface circulation may be present within the canyon. A subsurface backscattering particle layer was also observed in these regions of the canyon, suggesting that retention may be present below the surface mixed layer. This led to the hypothesis that a recirculating subsurface eddy was present below the mixed layer and retaining particles in the system. ☐ Three gliders were deployed in the austral summer of 2020 to test this hypothesis. Isopycnal doming was observed in similar regions to the canyon as 2015. The subsurface particle layer was also present, but it was not as strong as it was in 2015. Opportunistic transects illustrated a distinct lack of particles outside of the canyon, indicating possible retention in the canyon. Regional Ocean Model System (ROMS) simulations revealed the presence of subsurface, bathymetry-following flows forming ...
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