README FILE FOR 2022 BERING STRAIT CTD DATA           Version 25th Feb 2024
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This is an archive of CTD data from the 2022 Bering Strait mooring cruise.

The cruise was funded by the NSF-Arctic Observing Network grants:
- PLR-1758565 (PIs: Woogate and Peralta-Ferriz). 
- PLR-2153942 (PIs: Woogate and Peralta-Ferriz). 

The data are from a ~ 12 day cruise 
- on the US vessel Norseman II 
- from 8th - 19th Sept 2022
- sailing from and to Nome, Alaska, USA 
- to the Bering Strait and southern Chukchi Sea.
The cruise was also to service oceanographic moorings in the strait and those
data are archived separately. 

This is an archive of both hydrographic and bottle data.
A total of 111 science casts (125 including test casts) were taken and are 
included in this archive.
Water samples were taken for salinity (20) and nutrients (169) from the CTD
rosette and these data are included in this archive.
A separate pumping system was used to take trace metal (and accompanying
nutrient) samples during this cruise (lead: Laramie Jensen).  These data
are archived separately.

Stations were taken in US waters near mooring locations and on sections
in the Bering Strait and southern Chukchi Sea.  See cruise report,
accompanying event log and data headers for map, station locations, 
calibration, and processing details. 

The data are taken using an SBE9-11plus system, recording 
- pressure 
- temperature (dual system)
- conductivity (dual system)
- oxygen (dual system)
- fluorescence
- turbidity
connected also to an
- SUNA nitrate sensor, recording both internally and with the CTD data. 

A total of 169 samples were taken for nutrients, on 35 casts, to map
nutrient properties in the Bering Strait and southern Chukchi Sea region.
A total of 20 samples were taken for salinity on 5 casts, to check
bottle firing protocols. 

For an overview of previous and on-going Bering Strait mooring work,
please see http://psc.apl.washington.edu/BeringStrait.html.

For details of the measurements and their interpretation, please see:
   Woodgate, R.A., K.M.Stafford and F.G.Prahl (2015) A synthesis of
   year-round interdisciplinary mooring measurements in the Bering
   Strait (1990-2014) and the RUSALCA years (2004-2011), Oceanography
   28(3):46-67, doi:10.5670/oceanog.2015.57

Please cite that reference for the data. 

For queries, please contact:
   Rebecca Woodgate   woodgate@uw.edu   (206) 221-3268
   Polar Science Center, Applied Physics Lab, University of Washington (UW)
   1013 NE 40th, Seattle, WA  98105-6698   USA

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Meta data
=========

1) Platform: SBE9-11plus CTD rosette system (eleven 2.5l niskins) on board the RV Norseman II
  (one niskin place taken for the SUNA nitrate sensor)

2) Project title: Bering Strait

3) Data collection dates: 8th - 19th Sept 2022

4) PI:   Rebecca Woodgate (woodgate@uw.edu)

5) Data collection method:
     Hydrographic casts with water samples for nutrients and salinity

6) Data calibration method:
   = CTD:
	  Instrument calibrated by manufacturers some time prior and shortly
	after deployment.  Some post cruise calibrations found to give poor
	agreement to salinity samples.  The following cals, a mixture of
	pre and post cals, were used for the final data product. 
        Pressure calibrated June 2019 (precal)
        Temperature1 calibrated December 2022 (postcal)
        Temperature2 calibrated January 2021 (precal)
        Conductivity1 calibrated December 2022 (postcal)
        Conductivity2 calibrated February 2021 (precal)
        Oxygen1&2 calibrated November 2022
        Fluorescence / Turbidity calibrated  March 2010
     All times are given in GMT.
     All positions and times are from the ship's NMEA.
     For SBEs, calibration and processing details are in file header.

     = Salinity water samples:
	Collected to WOCE standards (3 rinses of bottle and cap)
	Analyzed at UW Marine Chemistry Lab to UNESCO 1994 JGOFS standards with
           resultant accuracy of 0.002psu
	Collected to verify bottle firing protocols.

     = Nutrient water samples:
	Collected to WOCE standards (3 rinses of bottle and cap).
	Samples filtered during collection (0.45micron 25mm Sterlitech filter)
	Samples frozen immediately after collection, and returned to UW frozen
           immediately after the cruise
	Analyzed at UW Marine Chemistry Lab to UNESCO 1994 JGOFS standards wth
           minimum detection limits of 
           0.03uM(PO4), 0.45uM(SO4), 0.18uM(NO3), 0.01uM(NO2), 0.09uM(NH4)
	See data header for more details.  

     = SUNA nitrate sensor data:
      In 2022, the SUNA nitrate data taken on the hydrographic sections were collected both on-board the SUNA 
(raw data) and with the CTD profile data via Seasave, the latter using a nominal calibration which is just a 
linear fit to the returned voltage.  While these raw two data sets are close in value, they are ~4uM higher 
than nitrate values from the bottle samples.  
      The on-board SUNA raw data were then processed using Seabird’s UCI software to apply a temperature and 
salinity correction to the bromide spectrum (see Sakamoto et al., 2009, doi: 10.4319/lom.2009.7.132), using 
temperature and salinity data from the CTD interpolated onto the times of the raw SUNA data.  This correction 
was run using both pre-cruise and post-cruise SUNA reference updates (i.e., short (order 1min) runs of the SUNA 
measuring in distilled water to correct the zero reading).  The two resultant data sets differ only by a 
constant (~0.2uM this year) and were closer to the bottle data   (rms error 1.6 or 1.4 uM, pre or post).  
     Since, compared to the bottle data, a significant drift in the SUNA data (~2uM) was evident over the 
course of the cruise, we combined the pre-cal and the post-cal SUNA data sets using a linear weighting by 
record number, such as to interpolate from the pre-cal at the start of the cruise to the post-cal by the end 
of the cruise.  This pre-post data set agreed with the bottle data to ~1.5uM (rms error). 
     Both before and after the cruise, we performed an extra calibration test at sea, making typically five 
to seven 1min SUNA runs, sampling either distilled water or a 20uM standard of nitrate solution made at UW 
(typically two or four distilled water runs, and three standard runs).  These runs showed the SUNA typically 
underestimated the standard by ~2uM, and some drift between pre-cruise and post-cruise still remained.  
Thus, for both pre and post at sea calibrations, we computed the offset between the pre-post data and at 
sea calibration and created a time-varying offset by interpolating between the pre and the post values 
weighted by record number, and applied a final correction by removing this time-varying offset from the 
pre-post data.  
      This final data set agreed with bottle samples to 0.6uM (rms error), with a mean offset to bottle 
data of -0.34uM (i.e., mean SUNA data are 0.34uM less than mean bottle data).    
      Note that these comparisons were all done comparing the SUNA data to the nitrate+nitrite of the 
bottle sample.  However, SUNA runs performed with a 20uM nitrite standard (made at UW), gave readings 
of 8uM instead of the 20uM expected.  This suggests that the SUNA reading is not nitrate+nitrite, but 
nitrate + (8/20)xnitrite, i.e., nitrate+0.4*nitrite, and thus the bottle values used for comparison 
were (1-0.4)*nitrite too high.   In this year, nitrite values were low, (maximum 0.14uM, mean 0.07uM), 
yielding a mean correction of only 0.04uM ((1-0.4)*0.07)).  While this implies the average fit of the 
SUNA is better than originally thought, (only 0.27uM less than the corrected bottle data), these 
differences are far smaller than the rms error of the data (0.6uM) and thus are not considered further, 
since this nitrite issue does not affect the final data (as ultimately that depends on the at sea 
calibrations, which were with a pure nitrate solution), but only affects the comparison to the bottle data.
     In summary, for 2022
- nitrate values in raw SUNA data (separate files) and .hex/xmlcon Seasave files are on average ~4uM 
greater than bottle data
- using Seabirds UCI temperature salinity correction and interpolating (by record number) between 
pre and post SUNA reference updates, this error can be reduced to ~1.5uM.
- by applying a further drift correction based on at-sea comparison to distilled water and a UW-made 
20uM nitrate standard solution, agreement of final data to bottle data is ~0.6uM
While .hex and .xmlcon files reflect the uncorrected SUNA data, the processed .cnv files archived 
here have been updated to contain corrected SUNA data, as indicated by ‘corSUNA’ in the file name.  
	

7) Instrumentation used:
     Sea-Bird SBE9-11plus system sampling at 24Hz with
         two SBE3F temperature sensors
         two SBE4C conductivity sensors
         two SBE43 Oxygen sensors
         one Wetlabs FLNTURT fluorescence/turbidity sensor
         one Seabird SUNA nitrate+nitrite sensor
         two SBE pumps
	Seabird 12 nisken rosette (2.5l, one bottle removed to accomodate other senors)
     Seabird SUNA nitrate sensor with 10mm pathlength

8) Quality control procedures:
     Basic quality control provided by Rebecca Woodgate.
     CTD processing by SBE software as described in cruise report and file headers. 
     SUNA processing as described above and in cruise report.
     Fluorescence/turbidity sensor cleaned prior to each cast. 

9) Data format:
	CTD:  standard Seabird output files,
              Bstrait22nn.hex data - as collected
              Bstrait22nnn.hdr data - as collected
              Bstrait22nnn.bl data - as collected  (not used by our processing)
              Bstrait22.... XMLCON - calibration coefficients
              Bstrait22nnnA00B15AdvOx2CTML7m4m18p5mndpDMF17corSUNA
                - processed data (at native time resolution) with corrected SUNA data
              Bstrait22nnnA00B15AdvOx2CTML7m4m18p5mndpDMF17corSUNABADCS010.cnv
                - processed data averaged to 1m bins from downcast with corrected SUNA data
              nnn gives cast number (see event log)
              Time (GMT), Latitude and longitude are recorded in the data files	
	SALINITY: 
	      original .xlsm file from UW Marine Chemistry,
	      ascii file of data, including 2s average of final CTD data at bottle firing 
	NUTRIENTS: 
	      Summary of nutrient samples locations, times, bottle numbers (xlsx)
              original .xls files from UW Marine Chemistry,
	      ascii file of data, including 2s average of final CTD data at bottle firing 
        SUNA:
              RAW SUNA files A00022.CSV to A0000071.CSV and instrument calibration and set up files.
              Time (GMT) is recorded in the data files.
              Corrected SUNA data have been added to the processed CTD data
      
10) Data collection problems:
	As no altimeter was used on the cruise, total water depth is recorded only in
	the cruise event log.  Reading there is ship's echosounder, depth below keel. 
	Add 2-3m to this to obtain full water depth.

	CTD data:
	Casts 0-4, 7-8 are on deck runs
	Casts 5-6, 9-14 were to check bottle firing
	Thus first science cast of the cruise is cast 15, and last cast is cast 125
        Casts 26, 37 and 55 – have times of corrected SUNA data drop out.  In full resolution data, 
           these are marked with a dummy value of -99.  Unfortunately this value is not recognized by 
           the Seasave bin averaging program as dummny and thus bin averages of these bins are erroneous.  
           However, for these files, the resultant values are all negative  and thus can easily be identified..  
	Cast 60 has bad data on the upcast
	Cast 65 has bad oxygen1 data on the upcast, oxygen2 is ok
	Recording of SUNA data to CTD problematic for casts 57 to 66 inclusive,
           however, data recorded internally on the SUNA are good, and these correct data
           are included in the final processed CTD files.  
  
     Salinity (from conductivity) senors (using postcal for C1, and precal for C2)
	  show an offset of <0.005psu.  See cruise report for more details. 
	With postcal, oxygen data agree to ~ 1% saturation. See cruise report for more details

11) Other related data sets:
       This data set is a part of a suite of measurements made in the
       Bering Strait almost continuously since 1990, often supported by
	  hydrographic data.  Mooring and past hydrographic data have
       already been archived at NODC/NCEI.
       For details see
        http://psc.apl.washington.edu/BeringStrait.html
        http://www.eol.ucar.edu/projects/sbi/
        http://sbi.utk.edu/
        http://www.nodc.noaa.gov
       Since 2000, CTD sections have been run in the Bering Strait on
       the mooring cruises.  These data are also accessible via the http
       links above.

12) Conditions for use or citation:
       Data freely available
       Please, as a courtesy, contact the PIs before using these data and cite as
           Woodgate, R.A., K.M.Stafford and F.G.Prahl (2015) A synthesis of
             year-round interdisciplinary mooring measurements in the Bering
             Strait (1990-2014) and the RUSALCA years (2004-2011), Oceanography
             28(3):46-67, doi:10.5670/oceanog.2015.57

13) Data qualifications or warnings:
       See also Data collection problems.
       SBE data: Standard Sea-Bird limitations apply
           - pressure 0.015% of FSR (6800m), i.e., ~ 1m (calibration suggests 0.6m)
           - temperature 0.001degC
           - Conductivity 0.0003S/m
               Combined errors equivalent to salinity error of ~0.008psu
	  Salinity samples - accuracy 0.002psu
	  Nutrient samples - Minimum Detection Limits are:
              0.03uM(PO4), 0.45uM(SO4), 0.18uM(NO3), 0.01uM(NO2), 0.09uM(NH4)


14) Grant numbers:
      Work funded by:
      - National Science Foundation (NSF) Arctic Observing Network (AON)
      program, grants:
		- PLR-1758565 (PI: Woodgate and Peralta-Ferriz)
		- PLR-2153942 (PIs: Woogate and Peralta-Ferriz). 


15) Sample repository locations:
        National Ocean Data Center/National Centers for Environmental
          Information (http://www.nodc.noaa.gov)
        University of Washington (http://psc.apl.washington.edu/HLD)

16) Please use the following citation for these data:
   Woodgate, R.A., K.M.Stafford and F.G.Prahl (2015) A synthesis of
       year-round interdisciplinary mooring measurements in the Bering
       Strait (1990-2014) and the RUSALCA years (2004-2011), 
       Oceanography, 28(3):46-67, doi:10.5670/oceanog.2015.57

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FILE LISTING
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Total number of files:  691 including 5 subdirectories.
Total number of casts: 125 (111 without test casts)
Total number of salinity samples:   20
Total number of nutrient samples:  169


Size (b)   Name
---------  ----
= Metadata file (1 file)
    18343 Bering_Strait_CTD_Sept2022_NSFAON_ReadMe_versFeb2024.txt

= Cruise report (1 file)
 11130277 BeringStrait2022CruiseReport_Norseman2_versFeb2024wEL.pdf

= Separate copy of event log (1 file)
    76587 BeringStrait2022_EventLog_FINAL.xlsx

.. and the 5 subdirectories: 

== One subdirectory of SBE .hex, .hdr, .bl and .XMLcon calibration files (376 files)
./BeringStrait2022CTD_hexhdrblandXMLCON:
Bstrait22nnn.hex, .hdr, .bl files (one per cast) where nnn is cast number, e.g.
       762 Bstrait22001.bl
       849 Bstrait22001.hdr
     28821 Bstrait22001.hex
and one XMLCON calibration file (which yields uncorrected SUNA data)
     10073 BSTRAIT22_finalcruisecal_combinedpreandpost.xmlcon

== One subdirectory of processed data at native time resolution (125 files),
including corrected SUNA data 
./BeringStrait2022CTD_processed:
Bstrait22nnnA00B15AdvOx2CTML7m4m18p5mndpDMF17corSUNA.cnv where nnn is cast number, e.g.,
    115177 Bstrait22001A00B15AdvOx2CTML7m4m18p5mndpDMF17corSUNA.cnv

== One subdirectory of processed data averaged to 1m bins from the down cast (125 files)
including corrected SUNA data
./BeringStrait2022CTD_Binaveraged:
Bstrait22nnnA00B15AdvOx2CTML7m4m18p5mndpDMF17corSUNABADCS010.cnv, where nnn is cast number, e.g.,
     15724 Bstrait22001A00B15AdvOx2CTML7m4m18p5mndpDMF17corSUNABADCS010.cnv

== One subdirectory of nutrient and salinity bottle data (8 files) 
./BeringStrait2022CTD_Bottledata_nutrientsandsalinity:
with salinity files:
  6272  BeringStrait_2022_Salinitysamples_vers2ndApr2023.txt - final data file with header
 27415  BeringStrait2022_EditedSaltsAnalysisFile_salt1.xlsm  - original analyis file
and nutrient files:
 41725  BeringStrait_2022_NutrientSampleswithCTDdata_vers25thFeb2024.txt - final data file with header
 18650  BStrait2022_SummaryofNutrientLogs.xlsx - summary of nutrient bottle logs
     and 4 files of original bottle analyses
 68608  BeringStrait2022_OrigNutAnalysisFile_bering2301.xls
 69632  BeringStrait2022_OrigNutAnalysisFile_bering2302.xls
 69632  BeringStrait2022_OrigNutAnalysisFile_bering2303.xls
 67584  BeringStrait2022_OrigNutAnalysisFile_bering2304.xls
     (file name is ...bering23... as samples were analyzed in Jan 2023)

== One subdirectory of raw (uncorrected) SUNA data and calibration files (54 files)
./BeringStrait2022CTD_RawSUNAdata:
two reference update files (G=precruise, H=postcruise)
     16063 SNA1916G.cal
     16165 SNA1916H.CAL
one instrument package file
   1049248 SUNA_1916_001.xml
and 51 data files for pre cruise calibrations, cruise data and post cruise calibrations
    A0000mmm.CSV, with mmm from 22 to 72 inclusive, e.g.,
   1265826 A0000022.CSV

+++++++++ END OF FILE LISTING ++++++++++++++++++++++++++++++ 