This dataset includes over 20,000 depth profiles collected with underwater gliders in a total of 18 missions between 2008 and 2023. The glider missions were centered at the long-term sampling site of the Hawaii Ocean Time-series (HOT) program, Station ALOHA (22°45′N, 158°W), within the North Pacific Subtropical Gyre. The gliders were equipped with sensors to measure temperature, salinity, pressure, dissolved oxygen concentration, chlorophyll a concentration from fluorescence (excitation/emission lambda = 470/695 nm), and the particulate backscattering coefficient at three wavelengths (lambda = 470 nm, 700 nm, and either 650 or 660 nm depending upon mission). Vertical profiles down to at least 200 m were collected for all sensors over periods of several months per mission. Chlorophyll a and oxygen concentrations are calibrated with discrete observations. Particulate backscattering coefficients are corrected with an additional dark subtraction. This dataset differs from the raw data files in that it is quality controlled, calibrated, and corrected. Raw data files can be found at https://hahana.soest.hawaii.edu/seagliders/index.php. The glider observations were collected over the years by Dr. Karl, with different funding sources (including NSF) to investigate carbon cycle processes in the oligotrophic North Pacific Subtropical Gyre. Dr. Ferron and Dr. Barone received NSF funding to conduct a re-analysis of this comprehensive dataset in order to characterize metabolic rates and understand their patterns of variability. Dr. Garcia conducted the data processing that resulted in this curated dataset. Steve Poulos operated the Seagliders in all missions.

Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
  • BCO-DMO Processing Description
• Related Publications
• Related Datasets
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

Vertically resolved data were collected by underwater Seagliders, which are guided autonomous underwater vehicles developed at the University of Washington’s Applied Physics lab (Eriksen et al., 2001). The Seagliders were piloted either in a circular or 'bowtie' pattern for several months in each mission around Station ALOHA.

Gliders were equipped with the sensors to measure temperature and salinity (Seabird CT Sail), pressure (Paine Electronics 211-75-710-05 and Kistler 4260M00), dissolved oxygen (Aandera models 5013 and 4330), chlorophyll fluorescence and optical backscatter at three wavelengths: 470 nm, 700 nm, and either 650 or 660 nm (WET Labs ECO Triplet ).

The raw observations were quality-controlled, accounting for known sensor responses and deviations from factory calibrations. Detailed descriptions of the data processing, quality control metrics, and calibration methods are provided by Garcia et al. (2023; https://doi.org/10.5281/zenodo.10247019). Quality control steps included a pitch angle test (to detect density inversions), global and regional range tests, stuck value test, biofouling evidence test, and visual inspection. If a test passed, the data were assigned a QC value of 1 (‘good data’). If a test failed (e.g. out of range or density inversion tests), data were flagged, either as ‘questionable data’ (QC = 3) or as ‘bad data’ (QC = 4). All quality control flags and adjustments (i.e. calibration and correction parameters) are preserved in each mission’s file.  Code for all processing steps is available on GitHub: https://github.com/cathygarcia/SeagliderDataprocessing.

Data processing steps for each variable are summarized below:

Temperature, Conductivity, Salinity, and Potential Density Anomaly

• - Both temperature and conductivity profiles were lag corrected.
• - Practical salinity was calculated using the Gibbs Seawater Toolbox, McDougall et al., 2011 (gsw_SP_from_C.m), and then converted to absolute salinity (gsw_SA_from_SP.m). 
• - Potential density anomaly was calculated with respect to a reference water pressure of 0 db using the Gibbs Seawater Toolbox (gsw_sigma0.m).

Dissolved oxygen concentrations

• - Raw optode phase values proceeded through a series of corrections to account for the effects of temperature, salinity, pressure, and time response in addition to sensor drift (Bittig et al., 2018, Barone et al., 2019).
• -  Optode phase values were converted to dissolved oxygen concentrations, and re-calibrated using discrete Winkler measurements. 

Chlorophyll a

• - Factory-calibrated chlorophyll a observations were re-calibrated using discrete measurements of either HPLC chlorophyll a (16 missions) or fluorometric chlorophyll a (2 missions).
• - Daytime chlorophyll a values are not quench corrected, and may be lower than actual values. It is recommended to use nighttime profiles near the surface. 
• - Additionally, a spike flag is included based on published protocol (Briggs et al., 2011).

Backscattering coefficient due to particles (bbp)

• - Factory-calibrated bbp values could have a large offset, that was not expected based on natural variability.
• - A mission-specific deep dark correction (1st percentile of bbp at 190-200 m) was subtracted for each bbp dataset. Both the uncorrected and corrected data are available.
• - Additionally, a spike flag is included based on published protocol (Briggs et al., 2011).

Submitted files processed with the BCO-DMO tool Laminar.

Submitted files named:

sg146_4_qc_pass.xlsx, sg146_6_qc_pass.xlsx, sg146_9_qc_pass.xlsx
sg146_5_qc_pass.xlsx, sg146_7_qc_pass.xlsx sg147_4_qc_pass.xlsx
sg148_11_qc_pass.xlsx sg148_16_qc_pass.xlsx sg148_8_qc_pass.xlsx
sg148_12_qc_pass.xlsx sg148_6_qc_pass.xlsx sg148_9_qc_pass.xlsx
sg511_21_qc_pass.xlsx
sg512_1_qc_pass.xlsx sg512_3_qc_pass.xlsx sg512_4_qc_pass.xlsx
sg626_1_qc_pass.xlsx, sg626_4_qc_pass.xlsx

Using the BCO-DMO laminar data processing tool, loaded each submitted seaglider Excel file with the naming format of _qc_pass.xlsx where is the lower-cased deployment value, e.g. sg146_4. The datasets span from 2008 to 2023. The sheets labeled ‘Data’ were used.

Added columns for any parameters not recorded for the deployment so that all files contain the same parameters, e.g. if the parameter bbp500 is missing, add an empty parameter column named bbp500. Parameters added are one or more of the following: oxygen, bbp500, bbp600, bbp700.

Added columns to hold the corresponding seaglider deployment, platform, and mission number for each data file.

Renamed the parameter ‘time’ to the BCO-DMO parameter name ‘ISO_DateTime_UTC’ to better represent the parameter contains UTC datetime values in the ISO8601 format.

Rounded the latitude and longitude values from 10 to 8 digit precision which is approximately a resolution of 1.11 mm.

Save these processed datasets to CSV files with the naming pattern 928732_suppl_seaglider_obs_sta_aloha_sg
.csv.

These files by deployment mission are included as supplemental files on the BCO-DMO dataset page.

Then the datasets by deployment mission were combined by year. The deployment years 2010 and 2011 overlapped, so they were combined into one dataset file.

These datasets by year were saved to CSV files of the naming format 928732_suppl_seaglider_obs_sta_aloha_.csv, e.g. the 2008 dataset is named 928732_suppl_seaglider_obs_sta_aloha_2008.csv and the 2010-2011 dataset is named 928732_suppl_seaglider_obs_sta_aloha_2010_2011.csv.

Finally, all the datasets organized by year were combined into a single dataset file named 928732_v1_seaglider_observations_sta_aloha_2008_2023.csv.

Coverage: North Pacific Subtropical Gyre

NSF Award Abstract:
Aquatic photosynthesis and respiration rates regulate the flux of organic matter into the ocean’s interior, a process that impacts Earth’s climate by sequestering carbon dioxide from the atmosphere and that provides most of the energy necessary to support the requirements of the organisms inhabiting the dark depths of the ocean. Recent improvements in sensor technology enabled the estimation of photosynthesis and respiration using accurate measurements of the concentration of oxygen dissolved in seawater collected by autonomous underwater vehicles and floats, even in regions of the ocean with low biological activity such as the subtropical gyres.

This project is analyzing data collected in the North Pacific ocean during 7 years using autonomous underwater vehicles in order to obtain an unprecedented number of estimates of metabolic rates for a region of the ocean that is representative of one of the largest oceanic ecosystems. This novel analysis helps constrain the amount of oxygen produced in the sea and improves our understanding of how variations in photosynthesis and respiration influence the flux of organic carbon towards the bottom of the ocean. Two undergraduate students from the University of Hawaii are supported and trained as part of this project. This project is analyzing publicly available observations of temperature, salinity, dissolved oxygen, chlorophyll fluorescence, and optical backscatter collected using underwater gliders in the North Pacific Subtropical Gyre between 2008 and 2014 (>1,000 days of observations). The analyses are used to: (i) quantify in situ rates of gross primary production and respiration in the mixed layer from diel oxygen oscillations, and determine their short-term variability and seasonality; (ii) quantify the net biological oxygen production (both in the mixed layer and in the lower euphotic zone) and determine its seasonality; (iii) quantify annual net community production, from which one can infer the net biological flux of organic C into the ocean’s interior; and (iv) assess how temporal changes in biomass are linked to changes in metabolic rates by comparing oxygen-based metabolic rates with optical proxies of phytoplankton biomass (backscatter and chlorophyll fluorescence). This investigation will better constrain the role of the ocean in regulating Earth’s climate by improved understanding of the mechanisms driving the temporal variability of metabolic rates in the oligotrophic ocean that covers a large fraction of our planet.