Dataset: Seaglider Profiles

Latitude and longitude (parameter names lat and lon) were measured at the surface and interpolated when the glider was at depth.  Parameter name GPS value id indicates measurements while glider was at the surface (value=1) or interpolated while diving (value=0).  No interpolation or smoothing was performed on other data. 

Temperature and salinity (parameter names temp and sal):  Temperature and salinity data were calculated using pre deployment calibration coefficients.  Further correction to temperature and conductivity was applied to NAB08 SG140 dataset based on the R/V Knorr calibration cast.  A first-order lag correction was applied to raw measurements of temperature and conductivity (due to temperature latency).  For each dive, out of range measurements and spikes (3 interquartile ranges above or below the median in windows of 15 contiguous measurements) were flagged and replaced with NaNs, which were repopulated by linear interpolation.  Data were smoothed with an 11-point median filter.  Parameters potemp and sigma_0 were calculated from the smoothed temp and sal datasets.  For more details, see Seaglider_CTD_Calibration-NAB08.pdf.

Dissolved oxygen, O2 (parameter name O2_cal):  Oxygen data from the Aanderaa optode were corrected for time lags in oxygen and temperature.  Winkler oxygen bottle data from glider – ship and float-ship calibration profiles, as well as concurrent glider – float profiles were used to determine the appropriate gain and offset.  The resulting oxygen has an error of ±2 µmol kg-1.  For more details, see Oxygen_glider_float_Calibration-NAB08.pdf. 

Particulate backscattering coefficients, bbp (parameter names bbp470, bbp700): Backscattering digital counts were converted to β at 117° by subtracting factory-provided dark counts and multiplying by factory calibration scale factors, modified based on measurements and calculations of Sullivan et al. (subm.)  Sensors were calibrated before the experiment and after the experiment. β at 117° was converted to bbp (m-1) by subtracting β of seawater (Zhang et al., 2009) and multiplying by 2πβ (where β = 1.132).  Ship-glider calibration profiles were used to produce fully cross calibrated data sets only for bbp at 700 nm (m-1).  The other backscattering coefficient (bbp at 470 (m-1)) is calculated using the factory calibrations only since the ship had only one backscatter sensor, i.e., bbp700.  For more details, see Backscatter_Calibration-NAB08.pdf.

Particulate organic carbon (POC) derived from bbp(700) (parameter name POC_bbp):  The regression to convert ship downcast bbp at 700 nm to POC is:
POC (mg C m-3) = bbp (700)_downcast  (m-1) * 35800 (mg C m-2) – 16.2 (mg C m-3); r2 = 0.81.
Because all backscatter sensors were cross calibrated with the ship CTD downcast, this regression was directly applied to glider bbp at 700 nm to compute glider POC.  For more details, see KN193-03 BOTTLE metadata and POC_cp_bbp_Calibration-NAB08.pdf.

Chlorophyll fluorescence (parameter names chl_raw):  Chlorophyll fluorescence measured by glider ECOPuck BB2F was cross-calibrated with other chlorophyll fluorometers by ship-glider calibration profiles and converted to volts.  Dark voltage (median in situ dark voltage = 0.083 volts) was subtracted from cross-calibrated values to obtain chlorophyll fluorescence in volts. The ECOPuck was calibrated before and after the experiment. For more details: Seaglider_chl_Calibration.pdf.