Metadata for Seaglider Surveys at Ocean Station Papa: Bin-Averaged Profiles, Currents, and Independent Oxygen Data ------------------------------------------------------------- RELATED CODE (RECOMMENDED): A MATLAB script, "OSP_SG_surveys_bin_data_load_and_plot.m", is available at github.com/noelpelland/SG-at-OSP/. This script provides examples of how to load and manipulate the data in this archive in MATLAB. The script also uses the data to reproduce some selected figures from Pelland et al. [2016] and Pelland et al. [submitted]. ------------------------------------------------------------- FILENAMES: (1) SG_at_osp_bin_avg_data.nc (2) SG_at_osp_DAC_data.nc (3) Pelland_et_al_SG_Surveys_III_Winkler_O2_Samples_at_OSP_2008_09.csv SOURCE: University of Washington School of Oceanography, Eriksen Seaglider Group, Noel Pelland (nap2@uw.edu) and Charles Eriksen (eriksen@uw.edu). Oyxgen data in File 3 were calculated from measurements collected by the S. R. Emerson (University of Washington, emerson@uw.edu) and R. C. Hamme (University of Victoria, rhamme@uvic.ca) research groups. COLLECTION DATES: 8 June 2008 to 2 April 2010. COLLECTION LOCATIONS: Gulf of Alaska and along Line P, North Pacific Ocean. DESCRIPTION OF PROJECT: Individual Seaglider autonomous underwater vehicles were deployed in three consecutive missions, surveying a 50 km by 50 km region surrounding a NOAA Ocean Climate Stations mooring at Ocean Station Papa [OSP; 50N, 145W] in the southern Gulf of Alaska. Seagliders sampled pressure, temperature, salinity, oxygen, and optical properties during continuous profiling of the top 1000 m of the ocean. Seaglider data were also used to estimate average currents in the top 1000 m during every descent/ascent profiling cycle. Seaglider profile data are available at the original sampling resolution at the National Oceanographic Data Center (https://www.nodc.noaa.gov/; NCEI accession numbers 0155762, 0155598, and 0155879). CONTENTS OF ARCHIVE: This archive includes Seaglider profile data that have been averaged in regular vertical bins (file 1 in Filenames above), average currents in the top 1000 m estimated from Seagliders (file 2), and oxygen samples collected independently from research vessels at OSP, which were used to postcalibrate Seaglider oxygen data (file 3). ------------------------------------------------------------- ORGANIZATION OF FILES: (1) SG_at_osp_bin_avg_data.nc is a netCDF file with 23 variables. Each variable contains 536297 values. Each value is one vertical depth bin within one Seaglider profile. (2) SG_at_osp_DAC_data.nc is a netCDF file with 7 variables. Each variable contains 1912 values. Each value corresponds to a unique Seaglider descent/ascent cycle. (3) Pelland_et_al_SG_Surveys_III_Winkler_O2_Samples_at_OSP_2008_09.csv is a comma-separated value file with 10 data columns. Each column contains 14 rows. Each row corresponds to a unique bottle cast performed from a research vessel at OSP. ------------------------------------------------------------- FILE (1) "SG_at_osp_bin_avg_data.nc" Seaglider profile data that have been averaged in regular vertical bins. NOTES: Temperature, salinity, and oxygen sensors, sampling, and processing are described in Pelland [2015] and Pelland et al. [2016]. Postcalibration methods for the oxygen optode sensors -- based on comparison to Winkler titration of seawater samples collected in the mixed layer from research vessels at OSP -- are described in Pelland [2015]. Sensors and processing methods for the optical variables are described in the supporting information of Pelland et al. [submitted]. These data have also previously been reported and used in the analyses of Pelland et al. [2017]. Both salinity variables - "salin" and "salin_interp" - were processed with a conductivity offset within each deployment, and salinity measurements were corrected for the thermal inertia of the conductivity sensor and position difference between the conductivity sensor and thermistor, as described in Pelland et al. [2016]. Some cycles are omitted due to lack of convergence of the iterative procedure used to correct for thermal inertia effects. The salinity profiles used to generate the bin-average data here were processed with an older (circa 2011) version of the Seaglider processing code than the results in the NODC archive. The differences between these processing schemes is generally small in comparison to the stated accuracy of the salinity samples. For the June 2008-August 2008 deployment, deeper than 100 m, the maximum absolute difference in salinity between the two processing versions was 0.0022 and 99% of differences were 1.1x10^-4 or less. Similarly, in the second (August 2008-June 2009) and third (June 2009-April 2010) deployments, 99% of differences were less than 1.6x10^-4. There were larger differences in the transition layer shallower than 100 m, where the instrument sample rate was often insufficient for either processing scheme to correct for thermal inertia effects on the conductivity sensor. This prompted the interpolation of salinity as a function of temperature in the transition layer, as described in Pelland [2015] and Pelland et al. [2016]. The salinity variable that includes this interpolation is "salin_interp" in this file. Bin-averaging was performed on data within +/- one bin depth interval in either direction. In other words, there is overlap in the vertical extents of adjacent bins. For example, the value in a depth bin centered at 4 m depth is an average of samples collected between 2 m and 6 m depth, the value at 6 m depth is an average of samples between 4 m and 8 m depth, and so on. Seawater properties were estimated during Seaglider processing using the now-obsolete EOS-80 MATLAB Seawater Toolbox: http://www.cmar.csiro.au/datacentre/ext_docs/seawater.htm. Missing values are set to NaN. The variables "o2_sat_frac_postcal" and "o2_postcal" are based on optode samples adjusted to independent oxygen measurements within the surface mixed layer (file 3) and are evaluated in the top 200 m only [Pelland et al., submitted]. These variables are set to NaN at greater depths. VARIABLES: 'bin_number' - Unique number for each entry within each variable (i.e., a "row number" or sample number) 'cyc' - Unique vehicle cycle number, equal to: [cycle number within a deployment] + (deployment number - 1)x1000, where deployment number = 1, 2, or 3 'pitch' - Vehicle pitch sign [-1 = descent, 1 = ascent] 't' - Time, MATLAB date convention [decimal days since Jan-0-0000] [UTC] 'lon' - Longitude [deg E] 'lat' - Latitude [deg N] 'dep' - Bin center depth [m, converted from pressure using EOS-80 seawater toolbox] 'temp' - in situ Temperature [deg C] 'salin' - Salinity [PSU] with correction for thermal inertia effects and deep salinity offset, but no interpolation in transition layer below mixed layer 'sigmat' - Sigma-t [kg m^-3, calculated using EOS-80 seawater toolbox] 'salin_interp' - Salinity [PSU] with correction for thermal inertia effects, deep salinity offset, AND interpolation in transition layer below mixed layer [this is the variable reported in Pelland et al. 2016] 'ptemp' - Potential temperature referenced to surface [deg C, calculated using EOS-80 seawater toolbox] 'sigmatheta' - Sigma-theta referenced to surface [kg m^-3, calculated using EOS-80 seawater toolbox] 'o2' - Optode-measured oxygen concentration [micromol kg^-1], calculated using optode dphase and vehicle temperature, but with NO postcalibration to bottle samples 'o2_sat' - Oxygen concentration at saturation equilibrium [micromol kg^-1] calculated from Garcia and Gordon [1992] with Benson and Krause coefficients 'o2_sat_frac_postcal' - Optode-measured oxygen concentration as a fraction of concentration at saturation equilibrium, postcalibrated following comparison to bottle samples at OSP 'o2_postcal' - Optode-measured oxygen concentration [micromol kg^-1], postcalibrated following comparison to bottle samples at OSP 'scatter_counts_700nm' - Optical backscatter digital sensor counts, 700 nm channel 'scatter_counts_470nm' - Optical backscatter digital sensor counts, 470 nm channel 'fluor_counts' - Fluorescence digital sensor counts 'b_bp_700nm' - Particulate scattering coefficient b_bp [m^-1], 700 nm channel, estimated using factory-calibrated scale factor and field-determined dark counts 'b_bp_470nm' - Particulate scattering coefficient b_bp [m^-1], 470 nm channel, estimated using factory-calibrated scale factor and field-determined dark counts 'rel_chl_a_fluor_channel' - Relative "chlorophyll a" [mg m^-3] derived from fluorescence digital counts, estimated using factory-calibrated scale factor and field-determined dark counts. The factory-calibrated scale factor does not necessarily represent the scale factor appropriate for the phytoplankton community at OSP and should not be interpreted quantitatively without comparison to independent field data. ------------------------------------------------------------- FILE (2) "SG_at_osp_DAC_data.nc" Seaglider depth-average current estimates for each vehicle descent/ascent cycle. NOTES: Processing methods and errors for depth-average current estimates are discussed in Pelland [2015] and Pelland et al. [2016]. As with "SG_at_osp_bin_avg_data.nc", some cycles are omitted due to lack of convergence of the iterative procedure used to correct for thermal inertia effects on the conductivity sensor. VARIABLES: 'tot_cycle_number' - Unique number for each entry within each variable (i.e., a "row number" or sample number) 'cyc' - Unique vehicle cycle number, equal to: [cycle number within a deployment] + (deployment number - 1)x1000, where deployment number = 1, 2, or 3 't' - Cycle midpoint time, MATLAB date convention [decimal days since Jan-0-0000] [UTC] 'lon' - Cycle midpoint longitude [deg E] 'lat' - Cycle midpoint latitude [deg N] 'U_DAC' - Zonal component of depth-averaged current estimated for this cycle [m s^-1] 'V_DAC' - Meridional component of depth-averaged current estimated for this cycle [m s^-1] ------------------------------------------------------------- FILE (3) "Pelland_et_al_SG_Surveys_III_Winkler_O2_Samples_at_OSP_2008_09.csv" Average oxygen concentrations in the mixed layer from Winkler titrations of seawater samples collected from independent research vessel visits to OSP. NOTES: These are averages of bottle samples collected by the S. R. Emerson (University of Washington, emerson@uw.edu) and R. C. Hamme (University of Victoria, rhamme@uvic.ca) research groups. VARIABLES: 'Cast_Date_Time_UTC' - Date and time at which vessel cast was performed [UTC] 'MLD_m' - Estimated mixed layer depth [m] [increase in density of 0.03 kg m^-3 from reference depth nearest 10 m] 'N_Samples_in_ML' - Number of bottle samples in mixed layer 'ML_avg_O2_Concentration_mumol_per_kg' - Average oxygen concentration from bottle samples in mixed layer [micromol kg^-1] 'ML_avg_Pct_Supersat' - Oxygen percent supersaturation, where concentration at saturation equilibrium is calculated from Garcia and Gordon [1992] with Benson and Krause coefficients 'Cast_lat_deg_N' - Cast latitude [deg N] 'Cast_lon_deg_E' - Cast longitude [deg E] 'Vessel' - Vessel name 'Cruise_Number' - Vessel cruise number 'Event_Number' - Cast event number within this cruise ------------------------------------------------------------- REFERENCES Garcia, H. E. and Gordon, L. I. [1992] Oxygen Solubility in Seawater: Better Fitting Equations. Limnology and Oceanography 37(6), 1307-1312. Pelland, N. A. [2015] Eddy Circulation, Heat and Salt Balances, and Ocean Metabolism: Observations from a Seaglider-Mooring Array at Ocean Station Papa. Ph.D. Thesis. Seattle, WA, USA: University of Washington. http://hdl.handle.net/1773/35285 Pelland, N. A., Eriksen, C. C., and Cronin, M F. [2016] Seaglider surveys at Ocean Station Papa: Circulation and water mass properties in a meander of the North Pacific Current. Journal of Geophysical Research: Oceans 121, 6816–6846. https://doi.org/10.1002/2016JC011920 Pelland, N. A., Eriksen, C. C., and Cronin, M. F. [2017] Seaglider surveys at Ocean Station Papa: Diagnosis of upper-ocean heat and salt balances using least squares with inequality constraints. Journal of Geophysical Research: Oceans 122, 5140–5168. https://doi.org/10.1002/2017JC012821 Pelland, N. A., Eriksen, C. C., Emerson, S. R., and Cronin, M. F. Seaglider surveys at Ocean Station Papa: Oxygen kinematics and upper-ocean metabolism. Submitted to the Journal of Geophysical Research: Oceans.