Relative phase between tidal and solar cycles influences the heating of a coral atoll lagoon
Cite this dataset
Merrigan, Sarah et al. (2024). Relative phase between tidal and solar cycles influences the heating of a coral atoll lagoon [Dataset]. Dryad. https://doi.org/10.5061/dryad.00000008t
Abstract
The residence time of water within reef-lagoon systems is of first-order importance to biogeochemical cycles and reef ecosystem functions. Circulation, mixing, and water renewal within these systems is highly dependent upon the geometry of the reef as well as wave, tide, and wind forcing. We are motivated to understand the physical driving a recent warming event as well as observed hypoxia-related fish kills and seagrass dieoff events in Dongsha Atoll lagoon, a 28 km wide coral atoll in the South China Sea. Though extensive work has been done on hypoxia events in temperate coastal systems, there remains a lack of understanding regarding the dynamics of these events in shallow tropical waters. Hydrographic observations were collected in summer 2019 to examine circulation and ocean-lagoon exchange in Dongsha Atoll lagoon. We construct a heat budget for the Dongsha Atoll lagoon to understand the physical processes governing lagoon circulation and ocean-lagoon exchange. We examine the influence of tides, winds, waves, advective exchange, and surface heating on lagoon heating and flushing time. Results show that surface heat fluxes drive rapid heating of the lagoon by approximately 1.5°C over the 22 day study period. Advective transport over the reef flat from tide- and wave-driven flows is an important component of oceanlagoon exchange that is balanced by a net outflow through the channels on subtidal timescales. Specifically, a near phase-locked interaction between diurnal solar forcing and near-diurnal tidal exchange drives persistent advective cooling over the reef flat. Estimated flushing times for the Dongsha Atoll lagoon range from 2.7 to 3.2 days for spring and neap tide, respectively.
README: Relative phase between tidal and solar cycles influences the heating of a coral atoll lagoon.
https://doi.org/10.5061/dryad.00000008t
The presented observations are part of a larger study of internal wave propagation around Dongsha Atoll Sinnett et al. 2022; Ramp et al. 2022). We used measurements of currents, pressure, and temperature in and surrounding the lagoon (channels, reef flat, forereef), as well as meteorological measurements taken on Pratas Island collected from 20 May 2019 - 09 June 2019.
Water temperature in the lagoon was measured on two fixed vertical moorings in the north and south lagoon, two vertically profiling moorings (WireWalkers, Rainville and Pinkel (2001)) in the east and west lagoon, and on bottom moored thermistors at various locations around the lagoon. Water temperature was measured in both the north channel (NCH) and south channel (SCH) on fixed vertical moorings and on the reef flat by a bottom moored thermistor. determined from a pre-deployment calibration bath. Corrected temperatures are within 0.055 $\degC$. Additionally, water temperature and salinity were measured with depth approximately every 2 days throughout the study period by a SonTek YSI Castaway CTD at three stations at the west, center, and east lagoon.
Water velocities were measured by three 1200kHz Teledyne RDI Workhorse Acoustic Doppler Current Profilers (ADCPs), one in the north channel, one in the south channel, and one on the east reef flat. Pressure in the lagoon was recorded by a SBE-37 on the north lagoon mooring, reef flat pressure was recorded by the east reef flat ADCP and offshore pressure by a bottom mounted ADCP located on the 10 m mooring on the east forereef, outside of the lagoon. The meteorological data used in this study was measured at the airport located on Pratas Island. Measurements include precipitation and shortwave radiation sampled at 1-minute intervals. Offshore conditions including wind speed, wind direction, significant wave height, and direction were obtained from the European Center for Medium-Range Weather Forecasts (ECMWF) ERA5 1-hour data on a 30-km grid (Hersbach et al. 2020)
*Instrumentation and mooring names below refer to Table 1 in the manuscript text. *
** File names, instrument locations, instrument types, and variable names with units are listed below**
- 10madcp.nc:
20o 41.987, 116o 55.421
Teledyne RDI Workhorse ADCP
measurements included: pressure (dbar), time ( Gregorian time)
- * 20madcp.nc:*
20o 41.963, 116o 55.536
Nortek AWAC
measurements included: pressure (dbar), Significant wave height (m), time (Gregorian time)
- Dongsha_T_bottom_mounted.txt:
Temp sensors: various depths as listed in file
locations: north channel: 20.75o 116.73o
north west: 20.72o 116.78o
north: 20.75o 116.84o
east: 20.70o 116.89o
east reef: 20.70o 116.89o
south east: 20.65o 116.86o
south: 20.63o 116.80o
south reef: 20.61o 116.80o
south west: 20.65o 116.75o
center: 20.68o 116.82o
measuring: time (gregorian), temperature (C)
- NCH_vel.nc:
20o 43.676, 116o 45.338
Current meter: Teledyne RDI Workhorse ADCP
measuring: E: East/West velocity per depth bin (m/s)
N: North/South velocity per depth bin (m/s)
temp: temperature per depth bin (C)
pressure: pressure at instrument (dbar)
bin size: height of depth bins (m)
time: timestep ( Gregorian time)
- RBRcon_065801_WWW_data.txt:
20° 41.065, 116° 47.012
RBR Concerto (CTD), profiling whole water column
measuring: Time (UTC),Conductivity(S/m),Temperature(C),Pressure(dbar),Dissolved oxygen(mg/L),Backscatter(m⁻¹sr⁻¹),Chlorophyl(μg/L)l,CDOM (ppb),Sea pressure ,Depth (m),Salinity(psu),Specific conductivity(S/m),Density anomaly(dbar),Speed of sound(m/s),Dissolved Oxygen concentration (mg/L)
- RF_vel.nc:
20o 41.976, 116o 54.145
Current Meter: Teledyne RDI Workhorse ADCP
measuring: E: East/West velocity per depth bin (m/s)
N: North/South velocity per depth bin (m/s)
temp: temperature per depth bin (C)
pressure: pressure at instrument (dbar)
bin size: height of depth bins (m)
time: timestep ( Gregorian time)
- sbe37_11248_nch_5p6mab.csv:
20o 43.670, 116o 45.336
SBE 37, 5.6 mab
measuring: time (julian days)
temperature (C)
salinity (psu)
pressure (dbar)
oxygen (mg/l)
oxygen temperature (C)
nitrogen saturation (mg/l)
depth (m)
density (kg/m^3)
conductivity (S/m)
- sbe37_14032_lnm_13p5mab.csv:
20o 43.533, 116o 49.274
measuring: time (Julian days)
temperature (C)
salinity (psu)
pressure (dbar)
depth (m)
density (kg/m^3)
conductivity (S/m)
- sbe37_15212_wwe.cnv:
20° 41.377, 116° 52.753
SBE37 (CTD), profiling whole water column
measuring: time (julian days)
temperature (C)
salinity (psu)
pressure (dbar)
oxygen (mg/l)
oxygen temperature (C)
nitrogen saturation (mg/l)
depth (m)
density (kg/m^3)
conductivity (S/m)
- SBE39_1376_NCH_0p4mab.csv:
20o 43.670, 116o 45.336
SBE 39, 0.4 mab
measuring: temperature (C), pressure (dbar), time (UTC)
- SBE39_05172_SCH_5p6mab.csv:
20o 39.035, 116o 43.403
SBE 39, 5.6 mab
measuring: temperature (C), pressure (dbar), time (UTC)
* SBE39_05173_LSM0p4mab.csv:
20o 38.700, 116o 49.939
SBE 39, 0.4 mab
measuring: temperature (C), pressure (dbar), time (UTC)
- SBE56_01123_LNM4.0mab.csv:
20o 43.533, 116o 49.274
** **SBE 56, 4 mab
measuring: time (UTC), temperature (C)
- SBE56_03176_LSM9.5mab.csv:
20o 38.700, 116o 49.939
SBE 56, 9.5 mab
measuring: time (UTC), temperature (C)
- SBE56_03177_LNM11.5mab.csv:
20o 43.533, 116o 49.274
SBE 56, 11.5 mab
measuring: time (UTC), temperature (C)
- SBE56_03958_LSW.csv:
20o 39.639, 116o 46.336
SBE 56, ~10 m depth
measuring: time (UTC), temperature (C)
- SBE56_03959_LNM14mab.csv:
20o 43.533, 116o 49.274
SBE 56, 14 mab
measuring: time (UTC), temperature (C)
- SBE56_05483_LNM7.5mab.csv:
20o 43.533, 116o 49.274
SBE 56, 7.5 mab
measuring: time (UTC), temperature (C)
- SBE56_06957_LSM13mab.csv:
20o 38.700, 116o 49.939
SBE 56,13 mab
measuring: time (UTC), temperature (C)
- SBE56_06963_CableReefVal.csv:
20° 42.005' ,116° 54.564'
SBE 56, ~1 m depth
measuring: time (UTC), temperature (C)
- SBE56_06972_LSM5.5mab.csv:
20o 38.700, 116o 49.939
SBE 56, 5.5 mab
measuring: time (UTC), temperature (C)
- SBE56_08980_LNW.csv:
20o 43.075, 116o 46.864
SBE 56, ~10 m depth
measuring: time (UTC), temperature (C)
- SCH_vel.nc:
20o 39.035, 116o 43.403
** **Current meter: Teledyne RDI Workhorse ADCP
measuring: E: East/West velocity per depth bin (m/s)
N: North/South velocity per depth bin (m/s)
temp: temperature per depth bin (C)
pressure: pressure at instrument (dbar)
bin size: height of depth bins (m)
time: timestep ( Gregorian time)
- SoloT_101044_SCh3mab_data.txt:
20o 39.035, 116o 43.403
RBR SoloT, 3 mab
measuring: time (UTC), temperature (C)
- SoloT_101045_LSM1p5mab_data.txt:
20o 38.700, 116o 49.939
RBR SoloT, 1.5 mab
measuring: time (UTC), temperature (C)
- SoloT_101200_SCh0p4mab_data.txt:
20o 39.035, 116o 43.403
RBR SoloT, 0.4 mab
measuring: time (UTC), temperature (C)
- SoloT_101201_NCh3mab_data.txt:
20o 43.670, 116o 45.336
RBR SoloT 3 mab
measuring: time (UTC), temperature (C)
Description of the data and file structure
Raw data files for the observational platforms used in this manuscript are provided and analyzed in the methods described above and in the paper. The locations of the various instrument platforms referred to in the data files are also listed in the previous section.
Methods
The presented observations are part of a larger study of internal wave propagation around Dongsha Atoll Sinnett et al. 2022; Ramp et al. 2022). We used measurements of currents, pressure, and temperature in and surrounding the lagoon (channels, reef flat, forereef), as well as meteorological measurements taken on Pratas Island collected from 20 May 2019 - 09 June 2019.
Water temperature in the lagoon was measured on two fixed vertical moorings in the north and south lagoon, two vertically profiling moorings (WireWalkers, Rainville and Pinkel (2001)) in the east and west lagoon, and on bottom moored thermistors at various locations around the lagoon. Water temperature was measured in both the north channel (NCH) and south channel (SCH) on fixed vertical moorings and on the reef flat by a bottom moored thermistor. determined from a pre-deployment calibration bath. Corrected temperatures are within 0.055 $\degC$. Additionally, water temperature and salinity were measured with depth approximately every 2 days throughout the study period by a SonTek YSI Castaway CTD at three stations at the west, center, and east lagoon.
Water velocities were measured by three 1200kHz Teledyne RDI Workhorse Acoustic Doppler Current Profilers (ADCPs), one in the north channel, one in the south channel, and one on the east reef flat. Pressure in the lagoon was recorded by a SBE-37 on the north lagoon mooring, reef flat pressure was recorded by the east reef flat ADCP and offshore pressure by a bottom mounted ADCP located on the 10 m mooring on the east forereef, outside of the lagoon.
The meteorological data used in this study was measured at the airport located on Pratas Island. Measurements include precipitation and shortwave radiation sampled at 1-minute intervals. Offshore conditions including wind speed, wind direction, significant wave height, and direction were obtained from the European Center for Medium-Range Weather Forecasts (ECMWF) ERA5 1-hour data on a 30-km grid (Hersbach et al. 2020)
Funding
National Science Foundation, Award: NSF-OCE1753317