Bathymetry‐Constrained Navigation of Argo Floats Under Sea Ice on the Antarctic Continental Shelf

Abstract

Antarctic continental shelf waters are poorly sampled, particularly beneath sea ice during winter. Profiling floats could help fill this gap, but floats are unable to surface to obtain a satellite position when ice is present. We deployed Argo profiling floats in a coastal polynya with a novel mission to rest on the sea floor between profiles. “Parking” on the seabed minimized the drift of the floats and allowed year‐round, full‐depth measurements over multiple winters. Measurements of water depth derived from the floats were used in combination with known bathymetry to constrain the position of profiles collected under ice. Errors were quantified by withholding known positions and comparing them to estimated positions; the bathymetrically constrained algorithm outperformed linear interpolation. A similar approach could potentially be used to geolocate other under‐ice oceanographic platforms that measure water depth.

Under-Ice Phytoplankton Blooms: Shedding Light on the “Invisible” Part of Arctic Primary Production

“…While operating beneath the sea-ice cover, profiling floats collect vertical profiles of key biogeochemical variables, and transmit data after surfacing in open water. The presence of sea ice makes it difficult to geolocate ARGO float platforms, so under-ice trajectories are estimated using interpolation methods (Wallace et al, 2020). In order to prevent risk of colliding with sea ice, floats stop their ascent at 10 m and cannot provide near-surface information.…”

Twenty-first century sea-level rise could exceed IPCC projections for strong-warming futures

“…Ice-prone shallow-operating Argo-type floats, and other types of AUV and sampling strategies, now exist but need to be deployed more broadly. 138 Sea mammals have been used with tremendous success in both hemispheres 139 to supplement Argo-type programs, but provide data only in their foraging grounds. It is also important to explore sub-ice-shelf cavities with robotic technologies to provide longterm measurements at and close to the ice-sheet grounding zone.…”

Spatial Variability of Antarctic Bottom Water in the Australian Antarctic Basin From 2018–2020 Captured by Deep Argo

“…To better put the bottom water properties in context of the processes occurring in the region, new float positions were needed. As of April 2020, there is no widely-accepted procedure for re-assigning profile locations, though bathymetry-constrained float locations are a subject of current research (Wallace et al, 2020). Fortunately, the maximum depth recorded by each profile gives an indication of its location in a near-shelf environment with variable bathymetry.…”