DOI: 10.5285/eb2f66fa-1c64-49af-b9e8-ce3124ce3c03
title: Autosub Long Range beneath Ronne Ice Shelf (2018): hydrographic, velocity and turbulence observations along the Modified Warm Deep Water Inflow

description: Autosub Long Range (ALR) was deployed along the Modified Warm Deep Water Inflow beneath Ronne Ice Shelf in February 2018 as part of the Ice shelves in a warming world: Filchner Ice Shelf system large grant, Antarctica. The vehicle was equipped with a Seabird Conductivity-Temperature-Depth (CTD) sensor, two Teledyne Acoustic Doppler Current Profilers (ADCPs), one upward looking and one downward looking, and a nose-mounted Rockland Scientific International MicroRider turbulence package. ALR followed a rhumb line course beneath the ice shelf, running approximately parallel to the 400 m isobath. The vehicle alternated between stretches of bottom tracking and top tracking in a square-wave pattern, while maintaining a minimum clearance of 80 m between the vehicle and the ice base or seabed. Funding was provided by the UK Natural Environment Research Council Large Grant Ice shelves in a warming world: Filchner Ice Shelf system, Antarctica (Grant No. NE/L013770/1).
description: All data were collected during the PS111-expedition to the southern Weddell Sea onboard the German research icebreaker RV Polarstern. CTD Hydrographic data were collected using a Seabird SBE-52 CTD that contains a ducted, pumped conductivity-temperature channel and samples at a rate of 1 Hz. The SBE-52 was mounted towards the front of ALR with the inlet and exhaust ducts attached to a pair of ports in the vehicle's hull. ADCP Velocity data were gathered using two Teledyne RDI 300 kHz Workhorse Acoustic Doppler Current Profilers (ADCPs). Both upward and downward looking ADCPs were configured in bottom track mode with 8 m bins and used for navigation as well as current measurements. Each ADCP was set to ping once every 2 seconds, with half-second ping separation between instruments to avoid interference, and the raw velocity data were processed using 5-ping (10 second) averaging. Current velocities in the vehicle frame were calculated by subtracting the bottom track velocity from the raw upwards and downwards-looking water track velocities and were then rotated into a geographic reference frame using the vehicle's heading. Turbulence Turbulence data were sampled using a front-mounted Rockland Scientific International (RSI) MicroRider turbulence package. The RSI MicroRider package had four microstructure probes sampling at a rate of 512 Hz: two orthogonally positioned shear probes and two thermistor probes. The turbulence data were processed using standard methods in the Rockland Scientific ODAS MATLAB Library.
description: Seabird SBE-52 Conductivity, Temperature and Depth sensor Two Teledyne RDI 300 kHz Workhorse Acoustic Doppler Current Profilers Rockland Scientific International (RSI) MicroRider turbulence package
description: From the Seabird SBE-52 Conductivity, Temperature and Depth sensor, the temperature data has an accuracy of ±0.002°C and the conductivity data has an accuracy of ±0.0003 S/m. Post-deployment, the SBE-52 was calibrated against ship-based CTD casts taken from RV Polarstern, with small corrections made to both temperature (+0.0024°C) and conductivity (+0.0002 S/m). The stated accuracy of the Teledyne RDI 300 kHz Workhorse ADCPs is 0.5% of the water velocity relative to the ADCP ±0.5 cm/s. The stated accuracy of the shear probes in the Rockland Scientific International MicroRider turbulence package is 5%. Missing values are indicated with a value of -9999.