Dataset Overview

This product represents a single-point-of-access, quality-controlled collection of basic shipboard hydrographic data (temperature, salinity, and nutrients). These were sampled by select programs of the US National Oceanic and Atmospheric Administration (NOAA) in Alaska waters, including the Gulf of Alaska (GOA), Bering Sea (BS), and Chukchi Sea (CS). Data coverage is 1974-2021 (CTD) or 2001-2021 (nutrient). Data sources and methodology are fully described in Mordy et al. (2025, "A compendium of temperature and salinity profiles and discrete nutrients from selected NOAA programs in Alaska", Scientific Data) and are briefly summarized here.

NOAA's Pacific Marine Environmental Laboratory (PMEL) was established in 1973, and thereafter began environmental studies in Alaska waters that focused on the physical dynamics of the GOA, eastern BS, and CS. In 1984 a new program was established between PMEL and NOAA's Alaska Fisheries Science Center (AFSC) now known as Ecosystems and Fisheries-Oceanography Coordinated Investigations (EcoFOCI). This program was initially focused on the Gulf of Alaska relating to the walleye pollock fishery and then expanded into the Bering Sea and to other fish species, with subsequent expansion into the Chukchi Sea. Long-term mooring sites were established and maintained, along with repeated hydrographic and biological surveys to monitor the seasonal and interannual dynamics of these ecosystems. In 1999, the AFSC Environmental Monitoring and Assessment program (EMA) program began to survey fish populations over the southeastern BS, as part of the Bering-Aleutian Salmon International Survey (BASIS); these gridded surveys were later extended to the northern BS and CS. This data compendium integrates archival oceanographic sampling from all of these sources.

The goals of this compendium dataset were to concatenate these sources into a single product, assess data quality and provide additional quality control measures, along with simple derived variables for ease of use. Temperature and salinity profiles have been reviewed and vetted for outliers. Archival cast location and time were screened based on the implied minimum vessel speed between profiles and corrected where possible based on digitized cruise logs. Reported bottom depth data were screened for agreement with sampling depth and corrected where possible. A version of salinity with suspect portions of profiles automatically deleted was constructed and included alongside archival data. Derived variables were estimated to augment the nutrient dataset, including dissolved inorganic nitrogen, and variables intended to help quickly identify whether samples are located in the surface mixed layer. These procedures and their results are described fully in Mordy et al. (2025). This product complements the archiving of individual cruise data at the National Centers for Environmental Information and other repositories; cross-reference information and links to these repositories are included where available.

File Description

The product assembles data from multiple cruises and years into five files. CTD data are contained in two netCDF files, which differ in the maximum depth extent that is included. Nutrient data are presented identically in two formats (netCDF and comma-separated-values). The fifth file includes cruise summary data.

The five data files:

• (1) ACOD_CTD_v1.0.nc
  A netCDF-4 file containing temperature and salinity profile data and metadata. CTD data are stored as 2-dimensional arrays of profiles versus pressure and time.
• (2) ACOD_CTD-250_v1.0.nc
  Identical to (1), but truncated to include only the top 250 dbar of data.
• (3) ACOD_NUT_v1.0.nc
  A netCDF-4 file containing nutrient data at discrete depths along with temperature and salinity from item (1), metadata, some derived quantities (e.g., total dissolved inorganic nitrogen [DIN]), and quality flags. Nutrient data are stored as 1-dimensional columns for each variable.
• (4) ACOD_NUT_v1.0.csv
  A version of (3) that is stored in a comma-separated-values format.
• (5) ACOD_CRUISE_v1.0.csv
  A comma-separated-values table containing cruise summary metadata.

The vertical coordinate for the data is pressure in units of dbar. Other collected or sampled variable types exist in some of the original data sets but have been excluded from this data product. NetCDF files in this data product adhere to the Climate and Forecast (CF) Metadata Conventions, version 1.8. Missing data are indicated by 1.0e35 in netCDF files, and NA in the nutrient csv file (4). All flags follow WOCE flagging conventions (Swift, 2008); 2=acceptable measurement, 3=questionable measurement, 4=bad measurement, 5=not reported.

Salinity Quality Control Variables

In (1)-(2), salinity variables appended with "_with_QC_applied" have suspect salinity regions deleted. Portions of profiles to be deleted were identified using an automated procedure, locating errors sufficient to cause a statically unstable profile (negative square buoyancy frequency N²) that exceeds a set threshold (N² < -1x10^-4 s^-2). This process is described fully in Mordy et al. (2025).

Salinity data prior to April 1987, stored in the variables "Salinity_PPT" or "Salinity_PPT_with_QC_applied", are of lower quality in some cruises and should be inspected prior to use.

Detailed File Contents/Variables

CTD Files (1)-(2)

PROFILE - arbitrary full-dataset profile number (1 to 27917), used to index profiles.
TIME - profile time in days since 1900-01-01.
LONGITUDE - profile longitude in degrees east.
LATITUDE - profile latitude in degrees north.
BOTTOM_DEPTH - bottom depth in meters as recorded in original cruise records. This variable is populated where available but missing in some instances.
REGION - profile geographic region (Gulf of Alaska, Bering Sea, Chukchi Sea).
CRUISE_NUMBER - arbitrary full-dataset cruise number for each profile. Cruise numbers can be cross-referenced to ACOD_CRUISE_v1.0.csv.
CRUISE_NAME - cruise name for each profile.
CAST - cast number within each cruise.
PRESSURE - pressure grid (dbar) on which profile data are stored.
Temperature - profile temperature (degrees C) in a 2-d array of dimensions [PROFILE] x [PRESSURE].
Salinity_PPT - profile salinity in a 2-d array of dimensions [PROFILE] x [PRESSURE]. This variable stores data from older cruises (pre-August 1995) reporting data in units of "Parts Per Thousand".
Salinity_PPT_with_QC_applied - same data as in variable "Salinity_PPT", but with suspect regions deleted as described above.
Salinity_PSS - profile salinity in a 2-d array of dimensions [PROFILE] x [PRESSURE]. This variable stores data from newer cruises (August 1995-on) reporting Practical Salinity.
Salinity_PSS_with_QC_applied - same data as in variable "Salinity_PSS", but with suspect regions deleted as described above.

Nutrient Files (3)-(4)

SAMPLE - arbitrary full-dataset sample number (1 to 45357) used to index nutrient samples, present in file (3) only (NetCDF file).
CRUISE_NUMBER - arbitrary full-dataset cruise number for sample profile. Cruise numbers can be cross-referenced to ACOD_CRUISE_v1.0.csv.
CRUISE_NAME - cruise name for sample profile.
CAST - sample profile cast number within each cruise.
BOTTLE_NUMBER - Niskin sample number within a profile. This variable is populated where available but missing in some instances.
PRESSURE - nutrient sample pressure (dbar).
TIME - sample profile time in days since 1900-01-01.
LONGITUDE - sample profile longitude in degrees east.
LATITUDE - sample profile latitude in degrees north.
BOTTOM_DEPTH- sample profile bottom depth in meters as recorded in original cruise records. This variable is populated where available but missing in some instances.
REGION - sample profile geographic region (Gulf of Alaska, Bering Sea, Chukchi Sea).
NO3 - nitrate concentration in micromoles per liter.
NO3_QC - status/quality flag for nitrate concentration. As noted above, flags follow WOCE flagging conventions (Swift, 2008); 2=acceptable measurement, 3=questionable measurement, 4=bad measurement, 5=not reported. For Ocean Data View (ODV) users working with the .csv file (4), manually renaming a flag variable as, e.g. for NO3, "NO3_FLAG_W", will allow ODV to easily link the quality control flag with the parameter of interest.
NO2 - nitrite concentration in micromoles per liter.
NO2_QC - status/quality flag for nitrite concentration.
NH4 - ammonium concentration in micromoles per liter.
NH4_QC - status/quality flag for ammonium concentration.
PO4 - phosphate concentration in micromoles per liter.
PO4_QC - status/quality flag for phosphate concentration.
H4SiO4 - orthosilicic acid concentration in micromoles per liter.
H4SiO4_QC - status/quality flag for orthosilicic acid concentration.
DIN - sample dissolved inorganic nitrogen (DIN) concentration in micromoles per liter. DIN is calculated as the sum of NO3, NO2, and NH4 variables; where any of these variables is missing, DIN is also missing.
DIN_QC - status/quality flag for DIN concentration.
DIN0 - alternate sample dissolved inorganic nitrogen (DIN0) concentration in micromoles per liter. DIN0 is calculated as for DIN (NO3+NO2+NH4), but if either NO2 or NH4 is missing, these concentrations are assumed to be zero. However, if NO3 is missing, DIN0 is also missing.
DIN0_QC - status/quality flag for DIN0 concentration.
NUT_COMMENT - comments/notes on sample characteristics, where applicable.
Temperature - CTD profile temperature (degrees C) interpolated to sample bottle depth.
Salinity - CTD profile Practical Salinity (PSS-78) interpolated to sample bottle depth, using the "Salinity_PSS_with_QC_applied" variable from (1)-(2). Nutrient data are reported starting in 2001, after the transition of salinity from PPT to Practical Salinity.
MLD10 - sample profile mixed-layer depth (dbar) from 10 dbar reference, based on 0.03 kg m^-3 density increment.
ILD10 - sample profile isothermal-layer depth (dbar) from 10 dbar reference, based on 0.2 degrees C temperature increment of either sign.
Delta_Sig10 - difference in density (sigma-t, kg m^-3) between sample depth and 10 dbar reference, in sample profile.
Delta_T10 - difference in temperature (degrees C) between sample depth and 10 dbar reference, in sample profile.\

Cruise Table (5)

CRUISE_NUMBER - arbitrary full-dataset cruise number, referenced in CTD and nutrient files.
CRUISE_NAME - cruise name as assigned in EcoFOCI/EMA records.
VESSEL - research vessel used for cruise.
Number_of_Casts - number of casts from each cruise included in the data product.
Total_Nutrient_Samples - number of rows in the nutrient data product files that correspond to this cruise.
First_Cast - date of first cast included in the data product.
Last_Cast - date of last cast included in the data product.
Min_Latitude_degN, Max_Latitude_degN, Min_Longitude_degE, Max_Longitude_degE - lat/lon coordinates of bounding box containing all casts from this cruise in the data product.
SalQC_Proportion_of_Casts_Applied - the proportion of casts in a cruise in which any data were deleted, located in the "Salinity_*_with_QC_applied" salinity variables.
SalQC_Mean_Vertical_Extent_dbar - in casts where salinity data were deleted, the average vertical extent deleted.
SalQC_Mean_Extent_Still_Unstable_dbar - in all casts, the average vertical extent of data remaining below a lower threshold for instability [N^2^ < -1x10^-5^ s^-2^], after QC application to salinity profiles.
Accession - where available, NCEI accession number(s) for repository data associated with this cruise.
Program - where available, NOAA program or project that was the subject of this cruise. Acronyms used in the Program field are listed below.
Link - where available, link to any lower-level archival data associated with this cruise, which may include other variable types not part of the ACOD product.
Region - geographic region(s) covered by this cruise (GOA: Gulf of Alaska, BS: Bering Sea, CS: Chukchi Sea).

Program Field Acronyms
AFSC: NOAA Alaska Fisheries Science Center
AOOS: Alaska Ocean Observing System
Arctic EIS: Arctic Ecosystem Integrated Survey
ARCWEST: Arctic Whale Ecology Study
ARI: NOAA Arctic Research Initiative
BASIS: Bering Arctic Subarctic Integrated Survey
BEST: Bering Sea Ecosystem Study
BOEM: Bureau of Ocean Energy Management
BOEMRE: Bureau of Ocean Energy Management, Regulation, and Enforcement
BSIERP: Bering Sea Integrated Ecosystem Research Program
CHAOZ: CHukchi Acoustic, Oceanographic, and Zooplankton
EcoFOCI: Ecosystem and Fisheries Oceanography Coordinated Investigations
EMA: NOAA AFSC Ecosystem Monitoring, and Assessment
FOCI: Fisheries Oceanography Coordinated Investigations
GLOBEC: Global Ocean Ecosystem Dynamics
GOAIERP: Gulf of Alaska Integrated Ecosystem Research Program
GOAIERP-LTL: Gulf of Alaska Integrated Ecosystem Research Program-Lower Trophic Level
GOAIERP-UTL: Gulf of Alaska Integrated Ecosystem Research Program-Upper Trophic Level
IARC: International Arctic Research Center
IGOSS: Integrated Global Ocean Service System
IMS-UAF: Institute of Marine Sciences, University of Alaska-Fairbanks
MACE: AFSC Midwater Assessment and Conservation Engineering Program
MIZEX: Marginal Ice Zone Experiment
NMFS: National Marine Fisheries Service
NMML: National Marine Mammal Laboratory
NOS: National Ocean Service
NPCREP: North Pacific Climate Regimes and Ecosystem Productivity
NPMR, NPMRP: North Pacific Marine Research
NPRB: North Pacific Research Board
NSF: National Science Foundation
OCC: Ocean Carrying Capacity (GLOBEC)
OCSEAP: Outer Continental Shelf Environmental Assessment Program
OER: NOAA Office of Ocean Exploration and Research
PacTOP: Pacific Tsunami Observational Program
PMEL: Pacific Marine Environmental Laboratory
RACE: AFSC Resource Assessment and Conservation Engineering Program
RUSALCA: Russian-American Long-Term Census of the Arctic
SEBS: Southeast Bering Sea
SEBSCC: Southeast Bering Sea Carrying Capacity
SECM: Southeast Coastal Monitoring
SSL: Steller Sea Lion
TAO: NOAA Tropical Atmosphere Ocean Array
UAF: University of Alaska Fairbanks

Usage Notes

These data are free for public use under the CC0 1.0 license.

If you use or publish these data we request that you cite both the data set (DOI: 10.5061/dryad.gf1vhhn0t) and the data description article (Mordy et al, 2025). Additionally, please notify authors herein of any related publications.