Measurements of physical oceanography and acoustic propagation near Jan Mayen, 26 October 2022 to 13 November 2022

Data Summary Northern Ocean Rapid Surface Evolution (NORSE) is an Office of Naval Research Departmental Research Initiative focusing on characterizing the key physical parameters and processes that govern the predictability of upper-ocean rapid evolution events occurring in high latitudes. This data set includes acoustic receptions from moored and drifting sources recorded on the Persistent Acoustic Observation System (PECOS), as well as physical oceanography measurements from moorings, Fast CTD (FCTD), and Drogued Buoy Air-Sea Interaction System (DBASIS). Acoustic Data The acoustic data were collected by PECOS, which has a 8192 Hz sample rate. For the NORSE experiment, PECOS was configured as a vertical linear array (VLA), which consisted of 52 hydrophones equally spaced 7.25 m apart with the deepest hydrophone 6.0 m above the seafloor. PECOS collected 24-min-long recordings every 4 h. This data set includes receptions from the moored source, located 42.4 km away on the north side of Jan Mayen Channel, as well as signals from a drifting source housed on DBASIS 1, which was deployed near PECOS and moved to the northeast over a period of several days. The mean depth of the moored source was 99.4 m and varied between 98.7 to 100.2 m over the course of the study. The source broadcast a 135-s linear frequency modulated (LFM) signal with a bandwidth of 500 to 1500 Hz. The signals were broadcast every four hours beginning on 26 October 2022 at 04:00 UTC and ending on 13 November 2022 at 04:00 UTC for a total of 109 broadcasts. The received signals were recorded on the PECOS VLA, pulse compressed, and plotted as a function of receiver depth to observe the depth-dependent structure of the measured signal arrivals. The DBASIS 1 source broadcast six 4.1-s LFM signals per minute for twenty minutes, twice per hour (48 times per day). The bandwidth was 610 to 890 Hz. The sequence was repeated for 40 minutes each hour for the duration of the deployment. The nominal depth of the source was 100 m. The signals were pulse compressed, and 10 arrivals were incoherently averaged to increase the signal-to-noise ratio. Although the source broadcast hourly with a relatively high duty cycle, the PECOS system only recorded data every four hours. A representative set of arrivals from the DBASIS 1 source was analyzed every four hours to examine the spatial evolution of the arrival structure as the range between source and receiver opened. There two netCDF files for the acoustic recordings; one for the signals from the moored (Acoustic_MooredSource.nc) and one for the signals from drifting source (Acoustic_DriftingSource.nc). Each file includes the approximate time vector in seconds (the clocks were not time aligned to facilitate a calculation of absolute travel time), the depth of each of the 52 hydrophones in meters below the sea surface, and the pulse compressed time series of the measured signal in decibels. Within each netCDF file, the variables for each recording are labeled by date:Signal_YYYY_MM_DD_HHDepth_YYYY_MM_DD_HHTime_YYYY_MM_DD_HH Mooring Data Four moorings were deployed to support NORSE. Three moorings were deployed on the south side of Jan Mayen Channel, with two of these moorings [known as the Persistent Acoustic Observation System (PECOS) and East Jan Mayen Ridge (JMR) moorings] designed to complement each other, positioned 0.7 km apart on the crest of East JMR near the 425 m isobath. The PECOS mooring included four RBR-duets sensors and four MAT1 tilt sensors. The nearby East JMR mooring included 11 RBR-solos and five Sea-Bird Scientific conductivity-temperature-depth recorders (SBE-37 CTDs) as well as three ADCPs to measure currents over the entire water column. The Jan Mayen Channel (JMCh) mooring, located on the 1585 m isobath, was 3.6 km north of PECOS, aligned in the direction of the source mooring. The JMCh mooring included 12 SBE-56 thermistors, seven SBE-37 CTDs, and two SBE-39 temperature-pressure recorders as well as four ADCPs (RDI Instruments 75 kHz and 300 kHz Workhorses and Nortek 55 kHz and 100 kHz Signatures) and two single-point current meters (Aanderaa Seaguard RCM with CTD). The fourth mooring, located on the the bathymetric rise on the north side of JMCh on the 1165 m isobath, housed the acoustic source. The source mooring included 12 SBE-56 thermistors, two SBE-37 CTDs, one RBR-duet, and one MAT-1 tilt sensor. The data from the PECOS and source moorings for the period from 26 October 2022 to 13 November 2022 are included in this data set. The data from the JMCh mooring are avaliable from the Norwegian Marine Data Centre (Fer, Ilker; Brakstad, Ailin (2025), Physical oceanography data from the Jan Mayen Channel mooring during the NORSE experiment, 26 October 2022 – 19 November 2023 [dataset] Norwegian Marine Data Centre https://doi.org/10.21335/NMDC-683103695). The East JMR mooring will be made avaliable at later date. There are netCDF files for the physical oceanography data recorded by insturments on the PECOS mooring (PO_PECOSMooring.nc) and Source mooring (PO_SourceMooring.nc). For all insturments, the nominal depth and timestamps in days after 1 January 2022 for the measurements are included. The SBE-56 thermistors are provide temperature data in degrees C, the RBRduets also include pressure in decibars, and the SBE-37 CTDs also provide salinity in psu. The MAT1 sensors provide temperature data in degrees C, three-axis acceraltion in g's, and three-axis magnetic flux in milliGauss. FCTD Data The FCTD system is deployed from a ship and consists of a tethered profiler with a RBR Concerto CTD and an altimeter.The instrument was raised and lowered with a direct drive electric winch at vertical speeds of approximately 5 m/s while the ship was steaming at a speed of 2.5 to 3 m/s. Sampling was focused on transects across JMCh (Lines 1, 2, 5, and 6), over the ridge (Lines 3 and 4), and over the bathymetric rise north of the source (Line 7). During a transect, the FCTD profiled from the sea surface to a depth of 200 to 500 m with the maximum depth extent being a trade-off between collecting data at depth and horizontal resolution. The FCTD_all_grouped.nc in stores the full data struct array by writing every element as its own group (/line_001, /line_002, …), so each line is self-contained with exactly the variables you chose to keep (e.g., lat, lon, depth, T, S, SA, CT). Within each group, time is saved twice: once as the raw MATLAB datenum (time_matlab) and once as a human-readable string (time_str). Other variables, like T, keep their original M×N (or higher) shapes without padding, so different lines can have different dimensions. To use the data, you simply open the group you want and read its variables; for example, in MATLAB you can load /line_001/T and /line_001/depth and then plot temperature with depth using contourf(1:size(T,2), depth, T); set(gca,'YDir','reverse'); colorbar. DBASIS Data The essential elements of the Drogued Buoy Air-Sea Interaction System (DBASIS) system are: (1) a WHOI surface buoy carrying high-quality surface meteorological instruments, a data logger, and satellite (Iridium) transmitters, (2) a Scripps Wirewalker profiling instrument package to measure temperature, salinity, velocity, and bio-optical properties at high vertical resolution, (3) fixed-depth subsurface instruments for temperature, salinity, and velocity, and (4) several hundred meters of jacketed wire rope and some depressor weights. Two DBASIS buoys were deployed in support of the NORSE 2022 cruise. DBASIS 1 included an acoustic source at a fixed depth of 100 m with two profiling wire walkers spanning from the surface to the source, and from the source to a depth of 300 meters. DBASIS 2 had a single Wirewalker that collected profiles from the surface to a depth of 500 m. The DBASIS WireWalker dataset is contained in DBASISall_grouped.nc and organized as a collection of sections, each saved as an independent group within the NetCDF file under the naming scheme WW_Section_###. Every section contains the key variables needed to reconstruct the sections: 'time' (both in raw MATLAB datenum and human-readable string form), geographic position ('lat', 'lon'), 'depth' (P stored as depth), and hydrographic properties ('T', 'S', 'SA', 'CT'). The sections are intentionally kept separate so that their native dimensions are preserved. Section WW_Section_1 is DBASIS-2 WireWalker, while WW_Section_2--WW_Section_4 correspond to different depth ranges of the DBASIS-1 WireWalker (upper, lower, and upper-repeat). The variables PT (potential temperature) and SA (Absolute Salinity) were computed using the TEOS-10 Gibbs Seawater (GSW) Oceanographic Toolbox. These quantities were derived from in-situ temperature (T), salinity (S), and pressure (depth) following the standardized GSW algorithms. Example to read:section = '/WW_Section_001';time = ncread(ncFile, [section '/time_matlab']); % numeric datenumT = ncread(ncFile, [section '/T']);S = ncread(ncFile, [section '/S']); Water Type Bundaries T-S diagrams were used to identify water types and understand their properties and relationships. After reviewing the water masses present in the Nordic Seas, a composite T-S diagram based on the FCTD measurements collected in and around the JMCh were examined to identify the water types observed within the study area. The water types are specific to the observations in JMCh in the fall 2022, and they are related to established water masses in the Nordic Seas through their temperature, salinity, and density properties. Three low-density water types composing the surface mixed layer in the region are identified: (1) a surface warm water type, made up of the warmest range of MNAW, (2) a surface mixed water type, also derived from Modified Norwegian Atlantic Water (MNAW) but exhibiting distinct T–S characteristics likely reflecting mixing with fresher, Arctic-origin surface waters; and (3) a surface cold water type, associated with Arctic Surface Water (ASW), though slightly warmer than the classical definition in earlier studies. Three additional water types represent contributions beneath the surface mixed layer: (4) an intermediate Atlantic water type, composed of MNAW and Modified Atlantic Water (MAW), (5) an intermediate Greenland Sea water type, and (6) a dense intermediate water type, combination the densest ranges fo Greenland Sea Arctic Intermediate Water (GSAIW) and dense Atlantic Water (dAW). Among these, the intermediate Atlantic type is particularly prominent. It spans a broad mixing line in T–S space, reflecting the wide range of property combinations.