Preprints
https://doi.org/10.5194/gi-2021-27
https://doi.org/10.5194/gi-2021-27

  19 Oct 2021

19 Oct 2021

Review status: this preprint is currently under review for the journal GI.

Glider Observations of Thermohaline Staircases in the Tropical North Atlantic Using an Automated Classifier

Callum Rollo, Karen J. Heywood, and Rob A. Hall Callum Rollo et al.
  • Centre for Ocean and Atmospheric Sciences, School of Environmental Sciences, University of East Anglia, Norwich, United Kingdom

Abstract. Thermohaline staircases are stepped structures of alternating thick mixed layers and thin high gradient interfaces. These structures can be up to several tens of metres thick and are associated with double-diffusive mixing. Thermohaline staircases occur across broad swathes of the Arctic and tropical/subtropical oceans and can increase rates of diapycnal mixing by up to five times the background rate, driving substantial nutrient fluxes to the upper ocean. In this study, we present an improved classification algorithm to detect thermohaline staircases in ocean glider profiles. We use a dataset of 1162 glider profiles from the tropical North Atlantic collected in early 2020 at the edge of a known thermohaline staircase region. The algorithm identifies thermohaline staircases in 97.7 % of profiles that extend deeper than 300 m. We validate our algorithm against previous results obtained from algorithmic classification of Argo float profiles. Using fine resolution temperature data from a fast-response thermistor on one of the gliders, we explore the effect of varying vertical bin sizes on detected thermohaline staircases. Our algorithm builds on previous work with improved flexibility and the ability to classify staircases from profiles with poor salinity data. Using our results, we propose that the incidence of thermohaline staircases is limited by strong background vertical gradients in conservative temperature and absolute salinity.

Callum Rollo et al.

Status: open (extended)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gi-2021-27', Carine van der Boog, 17 Nov 2021 reply

Callum Rollo et al.

Callum Rollo et al.

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Short summary
Using an underwater buoyancy powered autonomous glider, we collected profiles of temperature and salinity from the ocean NE of Barbados. Most of the temperature and salinity profiles contained staircase like structures of alternating constant values and large gradients. We wrote an algorithm to identify these staircases. We hypothesise that these staircases are prevented from forming where background gradients in temperature and salinity are too great.