SWOTALIS Moorings data south of New Caledonia: temperature, salinity, currents, pressure

This dataset was collected from three subsurface mooring lines deployed south of New Caledonia in March 2023, during the SWOTALIS-1 cruise, and recovered in November 2023 during the SWOTALIS-4 cruise onboard the R/V Antea. Moorings were equipped with instruments to measure temperature, salinity and currents throughout the full water column at three locations beneath the SWOT satellite fast-sampling phase tracks. Two mooring lines are beneath the SWOT swaths (M1 and M3), and one in the nadir gap (M2). Next to Mooring M3, a cage (C3) was also deployed at the bottom of the ocean to measure bottom pressure and currents.
Mooring M1 (Longitude= 167°20.505’E, Latitude= 23°29.067’S, Depth: 560m)
Mooring M2 (Longitude=167°34.174E, Latitude= 23°15.872S, Depth 1201m)
Mooring M3 (Longitude= 167°48.883’E, Latitude= 23°06.7285’S, Depth: 577m)
Cage C3 (Longitude= 167°48.621’E, Latitude= 23°06.682’S, Depth: 582m) The SWOTALIS campaign was a series of four cruises scheduled between March and November 2023 on the R/V Antéa. The aim of these campaigns was to observe fine-scale ocean structures in the region of the seamounts south of New Caledonia, a biodiversity hotspot. The SWOTALIS campaigns were planned to coincide with the SWOT Fast Sampling Phase. In the region of the seamounts south of New Caledonia, ocean hydrodynamics are complex. Tidal currents, encountering these topographical obstacles, generate internal tides which induce mixing on the slopes and impact benthic and pelagic ecosystems. Small eddies (~1-50 km) and filaments are also present. Disentangling these processes represent a challenge in this area. To help exploit and interpret the SWOT satellite data as effectively as possible, the SWOTALIS campaigns took place just before and during the Fast Sampling Phase, under a one-day SWOT track. The objectives of SWOTALIS were as follows: (i) to better understand the processes of internal tide generation and the interactions between internal tide propagation and ocean eddies (ii) to better understand the sea level signature of these internal waves and other fine-scale dynamic structures, and their observability by the SWOT satellite.
This dataset contains raw and quality controlled (QC'ed) instrument data from the three moorings. The data include temperature, salinity, velocity and pressure measurements from instruments deployed on the three moorings. The different files available are the following:
Level 1:  data for each mooring organized by instrument type. Temperature measurements are from Seabird SBE37 microcat, RBR duet, RBR concerto and RBR solo sensors (all of them also record pressure except RBR solo sensors). Salinity was measured by Seabird SBE37 microcat and RBR concerto sensors. Current velocities of the quasi full water column were measured by upward-and downward-looking Workhorse Acoustic Doppler Current Profilers (ADCPs) operating at 75 Hz or 300 kHz, with a vertical bin size dz = 16 m. Complementary measurements were provided by Nortek Aquadopp single-point current meters. The high-accuracy bottom pressure recorder  deployed in cage C3 is a RBRQuartz BPR.
Level 1 processing includes for the correction of time clocks, accounting for time-clock offsets and drifts. Time clocks were intercompared with a calibrated PC time before deployment and after recovery when available, allowing us to estimate initial offsets and temporal drift. When both were available, clock drift was corrected and variables were linearly interpolated onto corrected time stamps. For instruments lacking such intercomparisons, no correction could be applied; however, observed offsets and drifts were generally on the order of seconds. Level 2: Level 2 processing includes the interpolation of all time series onto a common regular time grid. Time stepping intervals vary from 30 s for RBR Solos to 20 min for ADCPs. We interpolated all time series with a time step of dt = 10 min, sufficient to resolve (super)tidal variability. Level 3: Level 3: processing includes the vertical binning onto a regular grid with spacing dz = 16 m, corresponding to the ADCP bin size. Not all instruments were equipped with pressure sensors (i.e. RBR Solo). For these, depths were estimated using nominal instrument spacing along the mooring line, accounting for mooring bending under horizontal currents. Specifically, depths were inferred assuming a constant bending angle α between neighboring instruments. For example, given known depths at z1, z2, the depth at z3 was estimated as z3 = z2 − ((z1−z2)/d12) d23, where d12 and d23 are nominal distances between instruments and cos(α) = (z1−z2)/d12. Level 4: Level 4 processing includes linear interpolation (without extrapolation) of all time series to account for data gaps within the water column (except salinity). Missing data near the surface and bottom were later reconstructed for isotherm displacements using a modal projection onto climatological vertical mode.