Caravela, an Autonaut, and the Seagliders

Caravela, an Autonaut, and three Seagliders will be piloted remotely from UEA (University of East Anglia) using iridium communications.

An AutoNaut is a wave-propelled unmanned autonomous surface vessel designed to take meteorological and oceanographic measurements at the air-sea interface. The vehicle is fitted with solar panels to power the instrumentation, as well as a small propeller for thrust when there are no waves. UEA recently purchased a 5-metre AutoNaut, named Caravela. The focus of Caravela’s work during EUREC4A is to gather data to determine air-sea fluxes of heat and momentum. One advantage of using an AutoNaut for this work is that the disturbance to the ocean surface is much lower than using a ship, improving accuracy of measurements close to the ocean surface. In addition, Caravela is equipped to carry and release a Seaglider, such that vertical fluxes can be determined throughout the ocean boundary layer. These platforms provide the opportunity to collect data in remote and harsh environments at a fraction of the cost of ship-based fieldwork.

Seagliders are buoyancy-powered autonomous underwater vehicles that can profile to 1000 m depth every 4 h for up to 6 months. A Seaglider will repeatedly dive and climb to produce a profile of the upper ocean. During EUREC4A, we will deploy 3 Seagliders (1 from Caravela and 2 from the Opens internal link in current windowR/V Meteor). These Seagliders will observe how the surface fluxes measured by the AutoNaut affect the near-surface ocean properties and processes.

Caravela's instrumentation

RadiationAn Apogee CS301-Pyranometer measures short wave solar radiation in the range of 360 nm – 1120 nm. An Apogee SL510-Pyrgeometer is an upward-looking thermopile pyrgeometer used to determine incoming longwave radiation between 5 μm and 30 μm.
Meteorology1An Airmar 120WX provides apparent wind speed and direction, as well as air temperature.
Meteorology2Humidity and temperature are measured by a Rotronic HC2A –S3 standard meteo probe and a Rotronic MP402H-082000 sensor with a Rotronic AC1003 unit. Situated on the mast of the AutoNaut, these measurements are approximately 1m above the sea surface
Ocean state
A Valeport miniCTD is fixed through the bottom of the AutoNaut for continuous sampling of near-surface salinity and temperature. Additionally, we have a Nortek Signature1000 1 MHz Acoustic Doppler Current Profiler (ADCP) with a 5 beam set up for estimating velocity shear and biomass in the water column, range 30 m.

Seagliders

The three seagliders will adopt different configurations of the available instrumentation as outlined below.

Configuration:

  1. SG579 Humpback: Seabird unpumped CT sail. Aanderaa 4130 oxygen optode.  PAR sensor.  Wetlabs triplet Ecopuck.
  2. SG637 Omura: Seabird unpumped CT sail. Nortek Signature1000 custom 4 head ADCP, 15 m range. Contros oxygen optode. WETLabs SeaOWL sensor.
  3. SG620 Seabird unpumped CT sail. Rockland Scientific MicroPod microstructure system: 1X shear 1X fast thermistor, both operating at 512 Hz.

Instrumentation

CT Sails
An SG579 Humpbac Seabird unpumped CT sail measure temperature and salinity
OxygenAanderaa 4130 oxygen optode measures dissolved oxygen concentration.
Ocean particulate
WETLabs SeaOWL measures crude oil-in-water, chlorophyll fluorescence and 700nm optical backscatter for particulate matter.  Wetlabs triplet ecopuck measures chlorophyll fluorescence and optical backscatter at two wavelengths
CurrentsNortek Signature ADCP measures ocean current shear, from which absolute currents can be derived.
TurbulenceRockland Scientific Micropod microstructure system measures ocean turbulence.

PI/Contact:

Karen Heywood, University of East Anglia


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