Seasonal oceanography of Hvalfjörður in southwest Iceland 2024-2025 – mooring data

The research project Seasonal oceanography of Hvalfjörður in southwest Iceland 2024-2025 was carried out by the Icelandic Marine and Freshwater Research Institute (MFRI) to obtain baseline data on physical and chemical oceanography and phytoplankton of the fjord over a full year. The geographic area of this research is bounded by the following coordinates: North: 64.5°, South: 64.2°, West: -21.3°, East: -22.1°. 
During twenty cruises conducted between April 2024 and April 2025 on three different vessels (Bjarni Sæmundsson HF30, Sæmundur fróði RE32 and Vonin KE10), samples were collected from ten to twelve fixed stations throughout the fjord for measurement of various parameters. Profiles of temperature, salinity, dissolved oxygen, pressure, fluorescence, turbidity and  Photosynthetic Active Radiation (PAR) were obtained by CTD. Discrete samples were collected at different depths  with Niskin bottles for the determination of salinity, dissolved oxygen, nitrate, silicate, phosphate, ammonium, pH, dissolved inorganic carbon, total alkalinity and chlorophyll a. At three of the fixed stations at two depths, samples were obtained for environmental DNA and sequenced using 18S rRNA V4 primers. Additionally, five moorings equipped with MicroCATs for obtaining timeseries for temperature, salinity, pressure, oxygen and pH, as well as ADCPs measuring current velocity, direction and acoustic backscatter were deployed at five different locations in the fjord. All data has been quality controlled. The full dataset has been split up into four subsets: CTD, discrete samples, e-DNA sequences and mooring data.
The data improves the basic understanding of the seasonality of the oceanography of the fjord at this point in time. In addition, the information can be used as input in model validations as well as enabling better assessment of the impact of various stressors, man-made or natural, on the environment in the fjord.
This dataset is a part of a larger dataset for this study that also contains CTD data, discrete data as well as eDNA sequencing data. This dataset includes temperature, salinity, pressure, oxygen and pH timeseries collected by Seabird SBE37SMP-ODO MicroCATs (CTDox) and Deep SeapHOx (CTDphox) instruments, as well as current velocity, direction and acoustic backscatter collected by RDI Teledyne Workhorse Sentinel 300 kHz Acoustic Doppler Current Profilers (ADCP) (600 kHz for mooring HVIN4) from moorings deployed at the five different locations HVNV, HVSV, HVNA, HVSA, HVIN in Hvalfjörður, Iceland. 
At each location, there have been between 1 and 4 mooring deployments. There is one data file for each deployment and each instrument (14 files for CTDox, 4 files for CTDphox, and 14 files for ADCP). File naming convention (example): HVIN3_CTDphox_61m_20250217_20250428.csv: HVIN (location name), 3 (third deployment period), CTDphox (instrument type), 61m (nominal depth), deployment date (yyyymmdd), recovery date (yyyymmdd). Metadata (mooring name, position, time, pressure/depth) is provided in each data file. Note that ADCP current velocity components are referenced to true north (both quality-controlled and raw data); magnetic declination has been taken account for.
Quality controlled data has been checked for deck values, outliers, and initial sensor adjustment after deployment. Salinity, dissolved oxygen and pH have been corrected to match calibrated CTD profiles and discrete sample data taken at nearby stations during  cruises in the same project. Temperature data was not corrected as differences between moorings and CTD profiles proved insignificant. ADCP data was quality-controlled wrt. deck values, pitch/roll <20°, outliers (current velocity >3 m s-1), bins affected by surface echo (shallower than 12.5% of the ADCP depth), and above surface bins. In the quality controlled data, data failing any of these criteria has been set to 9999.0. 
For all variables, quality flags following Copernicus standard (https://doi.org/10.13155/59938) are provided; flag values are 1 good data, 4 bad data (outliers, and values during sensor adjustment or above surface), 5 value changed (adjusted to match calibrated CTD and discrete sampling data), 7 nominal value (nominal depth if no pressure sensor), 9 missing value (on deck). 
Uncorrected raw data including all deck and above surface values is provided as well. 
CTD, oxygen and pH timeseries are provided in csv format. ADCP data is provided in netCDF format, following Copernicus Marine In Situ netCDF Format Manual 2.1.0 (https://doi.org/10.13155/59938) specifications.