Fig. 1: Hydrography, circulation, and observational coverage in the Amundsen Sea.
a Map of the Amundsen Sea continental shelf, highlighted in the inset Antarctica map (top left). Arrows indicate the time-mean modeled velocity at 455 m depth during the mooring observational period (2012–2014). Background colors indicate the correlation coefficient (r) between the 455-m velocity and the AU velocity (defined in Methods) at each grid-point based on monthly model output during the observational period. Black contours represent the 500-m isobath and blue contours indicate 1000- and 2000-m isobaths. White areas are regions with depths shallower than 455 m, light blue areas indicate ice shelves with names labeled, and gray areas denote grounded ice regions. b The study region marked in (a) by the blue rectangle. Arrows are the same as in (a) and background colors indicate the modeled time-mean potential temperature θ at 455 m depth during the observational period. Symbols denote observational locations used in this study: mooring (red star), conductivity-temperature-depth (CTD) stations with Lowered Acoustic Doppler Current Profiler (ADCP) velocity measurements (blue circles), and stations with additional microstructure turbulence measurements (spring green plus symbols). All CTD stations measure temperature and salinity profiles. Red rectangle indicates the region where the modeled results are used for the finescale parameterization. The yellow dashed line marks a cross-slope section that represents the main pathway of Circumpolar Deep Water inflow based on model results, as analyzed in Fig. 6. Moored observations of (c) along-trough velocity U (positive towards the shelf), (d) cross-trough velocity V, (e) the magnitude of velocity shear ∣Uz∣, and (f) potential temperature θ. U and V are derived by applying a 35° clockwise rotation, aligned with the trough axis, to the zonal and meridional velocity components. The blue dash-dotted line in (c) represents the spatially-averaged θ profile from CTD stations shown in (b) with depth-averaged standard deviation of 0.09 ∘C. Velocities in (c) and (d) include data from both the ADCP and the current meter, whereas the velocity shear in (e) is solely from the ADCP. The salinity used to calculate θ is from the CTD station measurements.
