Cruise Report, RV ATAIR, Cruise 0671021-1, Bremerhaven - Thyboron - Aberdeen, 18 Jul —- 10 Aug 2023 |
5.
scientific
Too's
and
Meihods
11
5.1 Overview
Scientific tools that were in use during the cruise comprised profiling of the entire water column
using a Conductivity-Temperature-Depth (CTD) unit attached to a carousel water sampler sys-
tem and equipped with a number of sensors that will be detailed in the following sections.
Additional sensors attached to the CTD-unit involved a sensor measuring dissolved oxygen, a
dual-wavelength sensor measuring simultaneousliy both turbidity and fluorescence, and an al-
timeter for determining the distance of the underwater unit to the sea bottom in order to avoid
sontact.
The carousel water sampler was equipped with a fixed number of 10 litres Niskin bottles to
allow for taking water samples at discrete depths of the water column. Water sampling activi-
ties consisted of taking oxygen and salinity samples for the sake of calibrating the conductivity
and oxygen sensors of the CTD unit, water samples for water density, chlorophyll-a and phy-
toplankton for home-based laboratory analyses. In total, 100 stations involving the CTDO/wa-
ter sampler system were carried out. Secchi depth determination, water sampling for chloro-
phyll-a and phytoplankton were only performed on daylight stations.
A vessel-mounted Acoustic Doppler Current Profiler (VMADCP) system operating at 150 kHz
and in narrow-band mode delivered oceanic velocity data of the upper water column during
the cruise. Further underway measurements focused on standard meteorological data, water
depth, near-surface values for water temperatures, salinity, fluorescence/chlorophyll and tur-
Didity.
5.2
CTD Sensor Unit and Water Sampler Setup
During cruise 067/021-1 a profiling conductivity-temperature-depth (pressure) sensor unit
(CTD) of type Sea-Bird Electronics (SBE) 9plus (“CTD Sonde S1”) was in use. It was operated
and power-supplied from out of the vessel’s hydrography lab via a deckunit of type SBE11plus.
The CTD sensor package was mounted horizontally in the lower part of a water sampler frame
of type SBE32 potentially carrying up to 12 Niskin bottles of 10 litres volume. The recording of
the raw data was done using the BSH software Seasave_Startf that internally calls the SBE-
software SeaSave, version 7.21f, and the data conversion software (from binary into ASCII)
SBEDataProcessing, version 7.25.0.319.
The CTD sensor package consisted of a primary and a secondary pair of temperature (T) and
zsonductivity (C) sensors that were each connected to a particular pump and the main CTD
housing carrying a pressure sensor. A through-flow oxygen sensor was connected to the pri-
mary T/C sensor pair. In addition, a dual-wavelength sensor of type WetflabECO delivering
simultaneously fluorescence and turbidity data was attached to and powered by the CTD sys-
tem. The distance to the sea bottom was estimated from an altimeter of type Teledyne Benthos
