Deep Argo Improves the Accuracy and Resolution of Ocean Bathymetry

Abstract

Ocean bathymetry plays an instrumental role in stirring ocean circulation and ocean mixing, shaping the transport of ocean heat, freshwater, oxygen, and carbon, influencing the propagation of tides and tsunamis, and controlling the dispersion of sediments, nutrients, and planktonic species. The dearth of direct ocean bathymetry measurements from shipboard echo sounders covering only 26% of the ocean floor calls for supplemental data. Satellites can provide bathymetry estimates in poorly-sampled regions, but intrinsic limitations of satellite measurements limit their ability to resolve features at horizontal scale <6 km (1/2 wavelength). Here, profile pressure and float descent rate from Deep Argo floats of the Deep Arvor and Deep SOLO float models were used to infer ∼14,000 ocean bathymetry measurements between 2014 and 2024. Our analysis indicates high consistency, 0.98 and 0.97 correlation coefficient, and small rms difference, 88 and 96 m, between multibeam sounding at 1,500–6,000 m depth and bathymetry measurements from Deep SOLO and Deep Arvor models respectively. The stronger agreement between Deep Argo-derived depths and multibeam data compared to altimetry is consistent with lower spatial uncertainties (<1.5 km for >77% of data coverage) and higher vertical accuracy of the Deep Argo data set (3.9–4.2 m at 4,000–6,000 m depth). The inclusion of the Deep Argo bathymetry in the general bathymetric chart of the ocean shows 50–200 m range improvement in the accuracy of altimetrically derived predicted depths.