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| Dataset Title: | [NBP1702 Dissolved Th and Pa] - Depth profiles of seawater dissolved 232Th, 230Th, and 231Pa from RVIB Nathaniel B. Palmer cruise NBP1702 from January to March 2017 (Water Mass Structure and Bottom Water Formation in the Ice-age Southern Ocean) 
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| Institution: | BCO-DMO (Dataset ID: bcodmo_dataset_813379) |
| Information: | Summary
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Attributes {
s {
Station_ID {
Byte _FillValue 127;
String _Unsigned "false";
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String bcodmo_name "station";
String description "Station number";
String long_name "Station ID";
String units "unitless";
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String bcodmo_name "date";
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String units "unitless";
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time {
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String ioos_category "Time";
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String source_name "Start_ISO_DateTime_UTC";
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String time_origin "01-JAN-1970 00:00:00";
String time_precision "1970-01-01T00:00Z";
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End_Date_UTC {
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End_Time_UTC {
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End_ISO_DateTime_UTC {
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Float64 colorBarMinimum -180.0;
String description "Start longitude";
String ioos_category "Location";
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String standard_name "latitude";
String units "degrees North";
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End_Longitude {
Float32 _FillValue NaN;
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Float64 colorBarMaximum 180.0;
Float64 colorBarMinimum -180.0;
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String nerc_identifier "https://vocab.nerc.ac.uk/collection/P09/current/LONX/";
String standard_name "longitude";
String units "degrees East";
}
Event_ID {
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String units "unitless";
}
Sample_ID {
Byte _FillValue 127;
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Byte actual_range 1, 23;
String bcodmo_name "sample";
String description "Sample number";
String long_name "Sample ID";
String nerc_identifier "https://vocab.nerc.ac.uk/collection/P02/current/ACYC/";
String units "unitless";
}
depth {
String _CoordinateAxisType "Height";
String _CoordinateZisPositive "down";
Float64 _FillValue NaN;
Float64 actual_range 4.513, 5247.235;
String axis "Z";
String bcodmo_name "depth";
String description "Sample depth";
String ioos_category "Location";
String long_name "Sample Depth";
String nerc_identifier "https://vocab.nerc.ac.uk/collection/P09/current/DEPH/";
String positive "down";
String standard_name "depth";
String units "m";
}
Th_230_D_CONC_BOTTLE_xucmu6 {
Float32 _FillValue NaN;
Float32 actual_range 0.65, 17.06;
String bcodmo_name "trace_element_conc";
String description "Dissolved Th-230 concentration";
String long_name "Th 230 D CONC BOTTLE Xucmu6";
String units "uBq/kg";
}
SD1_Th_230_D_CONC_BOTTLE_xucmu6 {
Float32 _FillValue NaN;
Float32 actual_range 0.03, 0.26;
String bcodmo_name "trace_element_conc";
String description "One standard deviation of Th_230_D_CONC_BOTTLE_xucmu6";
String long_name "SD1 Th 230 D CONC BOTTLE Xucmu6";
String units "uBq/kg";
}
Flag_Th_230_D_CONC_BOTTLE_xucmu6 {
Byte _FillValue 127;
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Byte actual_range 1, 2;
String bcodmo_name "q_flag";
Float64 colorBarMaximum 150.0;
Float64 colorBarMinimum 0.0;
String description "Quality flag for Th_230_D_CONC_BOTTLE_xucmu6";
String long_name "Flag Th 230 D CONC BOTTLE Xucmu6";
String units "None";
}
Th_232_D_CONC_BOTTLE_bwiimj {
Float32 _FillValue NaN;
Float32 actual_range 0.0168, 0.1426;
String bcodmo_name "trace_element_conc";
String description "Dissolved Th-232 concentration";
String long_name "Th 232 D CONC BOTTLE Bwiimj";
String units "pmol/kg";
}
SD1_Th_232_D_CONC_BOTTLE_bwiimj {
Float32 _FillValue NaN;
Float32 actual_range 6.0e-4, 0.0023;
String bcodmo_name "trace_element_conc";
String description "One standard deviation of Th_232_D_CONC_BOTTLE_bwiimj";
String long_name "SD1 Th 232 D CONC BOTTLE Bwiimj";
String units "pmol/kg";
}
Flag_Th_232_D_CONC_BOTTLE_bwiimj {
Byte _FillValue 127;
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Byte actual_range 1, 2;
String bcodmo_name "q_flag";
Float64 colorBarMaximum 150.0;
Float64 colorBarMinimum 0.0;
String description "Quality flag for Th_232_D_CONC_BOTTLE_bwiimj";
String long_name "Flag Th 232 D CONC BOTTLE Bwiimj";
String units "None";
}
Pa_231_D_CONC_BOTTLE_yq8ckw {
Float32 _FillValue NaN;
Float32 actual_range 0.43, 8.39;
String bcodmo_name "trace_element_conc";
String description "Dissolved Pa-231 concentration";
String long_name "Pa 231 D CONC BOTTLE Yq8ckw";
String units "uBq/kg";
}
SD1_Pa_231_D_CONC_BOTTLE_yq8ckw {
Float32 _FillValue NaN;
Float32 actual_range 0.03, 0.55;
String bcodmo_name "trace_element_conc";
String description "One standard deviation of Pa_231_D_CONC_BOTTLE_yq8ckw";
String long_name "SD1 Pa 231 D CONC BOTTLE Yq8ckw";
String units "uBq/kg";
}
Flag_Pa_231_D_CONC_BOTTLE_yq8ckw {
Byte _FillValue 127;
String _Unsigned "false";
Byte actual_range 1, 3;
String bcodmo_name "q_flag";
Float64 colorBarMaximum 150.0;
Float64 colorBarMinimum 0.0;
String description "Quality flag for Pa_231_D_CONC_BOTTLE_yq8ckw";
String long_name "Flag Pa 231 D CONC BOTTLE Yq8ckw";
String units "None";
}
Th_230_D_XS_CONC_BOTTLE {
Float32 _FillValue NaN;
Float32 actual_range 0.62, 16.96;
String bcodmo_name "trace_element_conc";
String description "Dissolved Th-230 concentration corrected for the dissolution of lithogenic minerals, thereby isolating the dissolved Th-230 produced by decay of dissolved uranium";
String long_name "Th 230 D XS CONC BOTTLE";
String units "uBq/kg";
}
Th_230_D_XS_CONC_BOTTLE_ERR {
Float32 _FillValue NaN;
Float32 actual_range 0.03, 0.27;
String bcodmo_name "trace_element_conc";
String description "One standard deviation of Th_230_D_XS_CONC_BOTTLE";
String long_name "Th 230 D XS CONC BOTTLE ERR";
String units "uBq/kg";
}
Th_230_D_XS_CONC_BOTTLE_FLAG {
Byte _FillValue 127;
String _Unsigned "false";
Byte actual_range 1, 2;
String bcodmo_name "q_flag";
Float64 colorBarMaximum 150.0;
Float64 colorBarMinimum 0.0;
String description "Quality flag for Th_230_D_XS_CONC_BOTTLE";
String long_name "Th 230 D XS CONC BOTTLE FLAG";
String units "none";
}
Pa_231_D_XS_CONC_BOTTLE {
Float32 _FillValue NaN;
Float32 actual_range 0.43, 8.39;
String bcodmo_name "trace_element_conc";
String description "Dissolved Pa-231 concentration corrected for the dissolution of lithogenic minerals (see metadata for full explanation)";
String long_name "Pa 231 D XS CONC BOTTLE";
String units "uBq/kg";
}
Pa_231_D_XS_CONC_BOTTLE_ERR {
Float32 _FillValue NaN;
Float32 actual_range 0.03, 0.55;
String bcodmo_name "trace_element_conc";
String description "One standard deviation of Pa_231_D_XS_CONC_BOTTLE";
String long_name "Pa 231 D XS CONC BOTTLE ERR";
String units "uBq/kg";
}
Pa_231_D_XS_CONC_BOTTLE_FLAG {
Byte _FillValue 127;
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String bcodmo_name "q_flag";
Float64 colorBarMaximum 150.0;
Float64 colorBarMinimum 0.0;
String description "Quality flag for Pa_231_D_XS_CONC_BOTTLE";
String long_name "Pa 231 D XS CONC BOTTLE FLAG";
String units "none";
}
}
NC_GLOBAL {
String access_formats ".htmlTable,.csv,.json,.mat,.nc,.tsv,.esriCsv,.geoJson,.odvTxt";
String acquisition_description
"Dissolved data:
Water samples were collected with a Sea-Bird Electronics CTD carousel fitted
with 24 12-liter PVC Niskin bottles.The carousel was lowered from the ship
with steel wire. Niskin bottles were equipped with nylon-coated closure
springs and Viton O-rings. After collection seawater was drained with Teflon-
lined TygonTM tubing and filtered through Pall AcropakTM 500 filters on deck
(gravity filtration, 0.8/0.45 \\u03bcm pore size) into Fisher I-Chem series 300
LDPE cubitainers. Approximately 5L was collected per desired depth. Prior to
the cruise, the tubing, filters and cubitainers were cleaned by immersion in
1.2 M HCl (Fisher Scientific Trace Metal Grade) for 4-5 days. Once filtered,
samples were adjusted to a pH ~2 with ultra-clean 6 M HCl (Fisher Scientific
OPTIMA grade), double-bagged, stored in pallet boxes until the end of the
cruise and then at room temperature once shipped to the participating
laboratories analysis.
Analytical methods for dissolved radionuclides:
LDEO:
In the on-shore laboratory, seawater samples were weighed to determine
sample size, taking into account the weight of the cubitainer and of the acid
added at sea. Then weighed aliquots of the artificial isotope yield monitors
229Th (20 pg) and 233Pa (0.5 pg) and 15 mg dissolved Fe were added to each
sample. After allowing 1 day for spike equilibration, the pH of each sample
was raised to 8.3-8.7 by adding ~12 mL of concentrated NH4OH (Fisher
Scientific OPTIMA grade) which caused iron (oxy)hydroxide precipitates to
form. Each sample cubitainer was fitted with a nozzle cap, inverted, and the
Fe precipitate was allowed to settle for 2 days. After 2 days, the nozzle caps
were opened and the pH~8.3-8.7 water was slowly drained, leaving only the iron
oxyhydroxide precipitate and 250-500mL of water. The Fe precipitate was
transferred to centrifuge tubes for centrifugation and rinsing with Milli-Q
H2O (>18 M\\u03a9) to remove the major seawater ions. The precipitate was then
dissolved in 16 M HNO3 (Fisher Scientific OPTIMA grade) and transferred to a
Teflon beaker for a high-temperature (180-200\\u00b0C) digestion with HClO4 and
HF (Fisher Scientific OPTIMA grade) on a hotplate in a HEPA-filtered laminar
flow hood. After total dissolution of the sample, another precipitation of
iron (oxy)hydroxide followed and the precipitate was washed with Mill-Q H2O,
centrifuged, and dissolved in 12 M HCl for a series of anion-exchange
chromatography using 6 mL polypropylene columns each containing a 1 mL bed of
Bio-rad resin (AG1-X8, 100-200 mesh size) and a 45 \\u03bcm porous polyethylene
frit (Anderson et al. 2012). The final column elutions were dried down at
180\\u00b0C in the presence of 2 drops of HClO4 and taken up in approximately 1
mL of 0.16 M HNO3/0.026 M HF for mass spectrometric analysis.
Concentrations of 232Th, 230Th and 231Pa were calculated by isotope dilution,
relative to the calibrated tracers 229Th and 233Pa added at the beginning of
sample processing. Analyses were carried out on a Thermo-Finnegan ELEMENT XR
Single Collector Magnetic Sector ICP-MS, equipped with a high-performance
Interface pump (Jet Pump), and specially-designed sample (X) and skimmer (Jet)
cones to ensure the highest possible sensitivity. All measurements were made
in low-resolution mode (\\u2206m/M\\u2248300), peak jumping in Escan mode across
the central 5% of the flat-topped peaks. Measurements were made on a
MasCom\\u2122 SEM; 229Th, 230Th,231Pa and 233Pa were measured in Counting mode,
while the 232Th signals were large enough that they were measured in Analog
mode. Two solutions of SRM129, a natural U standard, were run multiple times
throughout each run. One solution was in a concentration range where 238U and
235U were both measured in counting mode, allowing us to determine the mass
bias/amu (typical values varied from -0.01/amu to 0.03/amu). In the other,
more concentrated solution, 238U was measured in Analog mode and 235U was
measured in Counting mode, yielding a measurement of the Analog/Counting
Correction Factor. These corrections assume that the mass bias and Analog
Correction Factor measured on U isotopes can be applied to Th and Pa isotope
measurements. Each sample measurement was bracketed by measurement of an
aliquot of the run solution, used to correct for the instrumental background
count rates. To correct for tailing of 232Th into the minor Th and Pa
isotopes, a series of 232Th standards were run at concentrations bracketing
the expected 232Th concentrations in the samples. The analysis routine for
these standards was identical to the analysis routine for samples, so we could
see the changing beam intensities at the minor masses as we increased the
concentration of the 232Th standards. The 232Th count rates in our Pa
fractions are quite small, reflecting mainly reagent blanks, compared to the
232Th signal intensity in the Th fraction. The regressions of 230Th, 231Pa,
and 233Pa signals as a function of the 232Th signal in the standards was used
to correct for tailing of 232Th in samples.
Water samples were analyzed in batches of 15. Procedural blanks were
determined by processing two 4-5 L of Milli-Q water in an acid-cleaned
cubitainer acidified to pH ~2 with 6 M HCl as a sample in each batch. An
aliquot of two intercalibrated working standard solutions of 232Th, 230Th and
231Pa, SW STD 2010-1 referred to by Anderson et al. (2012) and SW STD 2015-1
which has lower 232Th activity (more similar to Pacific seawater conditions),
were also processed like a sample in each batch. Samples were corrected using
the pooled average of all procedural blanks run during processing of NBP1702
samples, with the exception of two batches (30 samples). It was discovered
that the 233Pa spike added to these batches also contained ~0.4fg of 231Pa.
The samples which had this contaminated spike added were blank corrected for
231Pa using the average 231Pa values in the two procedural blanks run in each
of those two batches. The average procedural blanks (not including two batches
with high 231Pa in the 233Pa spike) for 232Th, 230Th, and 231Pa were 3.2 pg,
0.25 fg, and 0.01 fg respectively.
Derived Parameters:
Th_230_D_XS_CONC_BOTTLE \\- The dissolved excess Th-230 concentration refers
to the measured dissolved Th-230 corrected for a contribution of Th-230 due to
the partial dissolution of uranium-bearing minerals, or lithogenics. Thereby
the dissolved excess represents solely the fraction of Th-230 produced in the
water by decay of dissolved uranium-234. We estimate the lithogenic Th-230
using measuring dissolved Th-232 and a lithogenic Th-230/Th-232 ratio of
4.0e-6 (atom ratio) as determined by Roy-Barman et al. (2002) and a conversion
factor to convert picomoles to micro-Becquerels.
Th_230_D_XS_CONC_BOTTLE = Th_230_D_CONC_BOTTLE \\u2013 4.0e-6 *1.7473e5 *
Th_232_D_CONC_BOTTLE
Pa_231_D_XS_CONC_BOTTLE \\- The dissolved excess Pa-231 concentration refers to
the measured dissolved Pa-231 corrected for a contribution of Pa-231 due to
the partial dissolution of uranium-bearing minerals, or lithogenics. Thereby
the dissolved excess represents solely the fraction of Pa-231 produced in the
water by decay of dissolved uranium-235. We estimate the lithogenic Pa-231
using measuring dissolved Th-232 and a lithogenic Pa-231/Th-232 ratio of
8.8e-8 (atom ratio) which is derived from assuming an average upper
continental crustal U/Th ratio (Taylor and McClennan, 1995) and secular
equilibrium between Pa-231 and U-235 in the lithogenic material. An additional
conversion factor is needed to convert picomoles to micro-Becquerels.
Pa_231_D_XS_CONC_BOTTLE = Pa_231_D_CONC_BOTTLE \\u2013 8.8e-8 * 4.0370e5 *
Th_232_D_CONC_BOTTLE
The correction for dissolved 231Pa and 230Th derived from dissolution of
lithogenic particles, when calculating xs230Th and xs231Pa is small.
Therefore, even for a sample where the 232Th, used to make the correction, is
flagged as bad, the error contributed in calculating xs230Th nd xs231Pa is
small, so they are flagged as questionable (2).\\u00a0See the Processing
Description for complete\\u00a0quality flag definitions.";
String awards_0_award_nid "810778";
String awards_0_award_number "OPP-1542962";
String awards_0_data_url "http://www.nsf.gov/awardsearch/showAward.do?AwardNumber=1542962";
String awards_0_funder_name "NSF Office of Polar Programs (formerly NSF PLR)";
String awards_0_funding_acronym "NSF OPP";
String awards_0_funding_source_nid "713360";
String awards_0_program_manager "Michael E. Jackson";
String awards_0_program_manager_nid "806862";
String cdm_data_type "Other";
String comment
"Depth profiles of seawater dissolved 232Th, 230Th, and 231Pa
from RVIB Nathaniel B. Palmer cruise NBP1702
PI: Robert F. Anderson (LDEO)
Co-PI: Martin Q. Fleisher (LDEO)
Contact: Frank J. Pavia (LDEO)
Version date: 03 June 2020";
String Conventions "COARDS, CF-1.6, ACDD-1.3";
String creator_email "info@bco-dmo.org";
String creator_name "BCO-DMO";
String creator_type "institution";
String creator_url "https://www.bco-dmo.org/";
String data_source "extract_data_as_tsv version 2.3 19 Dec 2019";
String dataset_current_state "Final and no updates";
String date_created "2020-05-28T20:17:06Z";
String date_modified "2020-06-04T20:11:49Z";
String defaultDataQuery "&time<now";
String doi "10.26008/1912/bco-dmo.813379.1";
Float64 Easternmost_Easting -169.598;
Float64 geospatial_lat_max -53.958;
Float64 geospatial_lat_min -66.841;
String geospatial_lat_units "degrees_north";
Float64 geospatial_lon_max -169.598;
Float64 geospatial_lon_min -173.907;
String geospatial_lon_units "degrees_east";
Float64 geospatial_vertical_max 5247.235;
Float64 geospatial_vertical_min 4.513;
String geospatial_vertical_positive "down";
String geospatial_vertical_units "m";
String history
"2024-12-30T17:24:58Z (local files)
2024-12-30T17:24:58Z https://erddap.bco-dmo.org/erddap/tabledap/bcodmo_dataset_813379.html";
String infoUrl "https://www.bco-dmo.org/dataset/813379";
String institution "BCO-DMO";
String instruments_0_acronym "Niskin bottle";
String instruments_0_dataset_instrument_nid "813444";
String instruments_0_description "A Niskin bottle (a next generation water sampler based on the Nansen bottle) is a cylindrical, non-metallic water collection device with stoppers at both ends. The bottles can be attached individually on a hydrowire or deployed in 12, 24, or 36 bottle Rosette systems mounted on a frame and combined with a CTD. Niskin bottles are used to collect discrete water samples for a range of measurements including pigments, nutrients, plankton, etc.";
String instruments_0_instrument_external_identifier "https://vocab.nerc.ac.uk/collection/L22/current/TOOL0412/";
String instruments_0_instrument_name "Niskin bottle";
String instruments_0_instrument_nid "413";
String instruments_0_supplied_name "24 12-liter PVC Niskin bottles";
String instruments_1_acronym "CTD Sea-Bird";
String instruments_1_dataset_instrument_nid "813443";
String instruments_1_description "Conductivity, Temperature, Depth (CTD) sensor package from SeaBird Electronics, no specific unit identified. This instrument designation is used when specific make and model are not known. See also other SeaBird instruments listed under CTD. More information from Sea-Bird Electronics.";
String instruments_1_instrument_external_identifier "https://vocab.nerc.ac.uk/collection/L05/current/130/";
String instruments_1_instrument_name "CTD Sea-Bird";
String instruments_1_instrument_nid "447";
String instruments_1_supplied_name "Sea-Bird Electronics CTD";
String instruments_2_acronym "ICP Mass Spec";
String instruments_2_dataset_instrument_nid "813446";
String instruments_2_description "An ICP Mass Spec is an instrument that passes nebulized samples into an inductively-coupled gas plasma (8-10000 K) where they are atomized and ionized. Ions of specific mass-to-charge ratios are quantified in a quadrupole mass spectrometer.";
String instruments_2_instrument_external_identifier "https://vocab.nerc.ac.uk/collection/L05/current/LAB15/";
String instruments_2_instrument_name "Inductively Coupled Plasma Mass Spectrometer";
String instruments_2_instrument_nid "530";
String instruments_2_supplied_name "Thermo-Finnegan ELEMENT XR Single Collector Magnetic Sector ICP-MS";
String instruments_3_dataset_instrument_nid "813445";
String instruments_3_description "A machine with a rapidly rotating container that applies centrifugal force to its contents, typically to separate fluids of different densities (e.g., cream from milk) or liquids from solids.";
String instruments_3_instrument_name "Centrifuge";
String instruments_3_instrument_nid "629890";
String keywords "bco, bco-dmo, biological, bottle, bwiimj, chemical, conc, data, dataset, date, depth, dmo, end, End_Date_UTC, End_ISO_DateTime_UTC, End_Latitude, End_Longitude, End_Time_UTC, erddap, error, event, Event_ID, flag, Flag_Pa_231_D_CONC_BOTTLE_yq8ckw, Flag_Th_230_D_CONC_BOTTLE_xucmu6, Flag_Th_232_D_CONC_BOTTLE_bwiimj, iso, latitude, longitude, management, oceanography, office, Pa_231_D_CONC_BOTTLE_yq8ckw, Pa_231_D_XS_CONC_BOTTLE, Pa_231_D_XS_CONC_BOTTLE_ERR, Pa_231_D_XS_CONC_BOTTLE_FLAG, preliminary, sample, Sample_Depth, Sample_ID, sd1, SD1_Pa_231_D_CONC_BOTTLE_yq8ckw, SD1_Th_230_D_CONC_BOTTLE_xucmu6, SD1_Th_232_D_CONC_BOTTLE_bwiimj, start, Start_Date_UTC, Start_Time_UTC, station, Station_ID, Th_230_D_CONC_BOTTLE_xucmu6, Th_230_D_XS_CONC_BOTTLE, Th_230_D_XS_CONC_BOTTLE_ERR, Th_230_D_XS_CONC_BOTTLE_FLAG, Th_232_D_CONC_BOTTLE_bwiimj, time, xucmu6, yq8ckw";
String license "https://www.bco-dmo.org/dataset/813379/license";
String metadata_source "https://www.bco-dmo.org/api/dataset/813379";
Float64 Northernmost_Northing -53.958;
String param_mapping "{'813379': {'Start_ISO_DateTime_UTC': 'flag - time', 'Sample_Depth': 'flag - depth', 'Start_Longitude': 'flag - longitude', 'Start_Latitude': 'flag - latitude'}}";
String parameter_source "https://www.bco-dmo.org/mapserver/dataset/813379/parameters";
String people_0_affiliation "Lamont-Doherty Earth Observatory";
String people_0_affiliation_acronym "LDEO";
String people_0_person_name "Robert F. Anderson";
String people_0_person_nid "50572";
String people_0_role "Principal Investigator";
String people_0_role_type "originator";
String people_1_affiliation "Lamont-Doherty Earth Observatory";
String people_1_affiliation_acronym "LDEO";
String people_1_person_name "Martin Q. Fleisher";
String people_1_person_nid "51612";
String people_1_role "Co-Principal Investigator";
String people_1_role_type "originator";
String people_2_affiliation "Lamont-Doherty Earth Observatory";
String people_2_affiliation_acronym "LDEO";
String people_2_person_name "Frank J. Pavia";
String people_2_person_nid "643657";
String people_2_role "Contact";
String people_2_role_type "related";
String people_3_affiliation "Woods Hole Oceanographic Institution";
String people_3_affiliation_acronym "WHOI BCO-DMO";
String people_3_person_name "Shannon Rauch";
String people_3_person_nid "51498";
String people_3_role "BCO-DMO Data Manager";
String people_3_role_type "related";
String project "SNOWBIRDS";
String projects_0_acronym "SNOWBIRDS";
String projects_0_description
"NSF Award Abstract:
Scientists established more than 30 years ago that the climate-related variability of carbon dioxide levels in the atmosphere over Earth's ice-age cycles was regulated by the ocean. Hypotheses to explain how the ocean regulates atmospheric carbon dioxide have long been debated, but they have proven to be difficult to test. Work proposed here will test one leading hypothesis, specifically that the ocean experienced greater density stratification during the ice ages. That is, with greater stratification during the ice ages and slower replacement of deep water by cold dense water formed near the poles, the deep ocean would have held more carbon dioxide, which is produced by biological respiration of the organic carbon that constantly rains to the abyss in the form of dead organisms and organic debris that sink from the sunlit surface ocean. To test this hypothesis, the degree of ocean stratification during the last ice age and the rate of deep-water replacement will be constrained by comparing the radiocarbon ages of organisms that grew in the surface ocean and at the sea floor within a critical region around Antarctica, where most of the replacement of deep waters occurs. Completing this work will contribute toward improved models of future climate change. Climate scientists rely on models to estimate the amount of fossil fuel carbon dioxide that will be absorbed by the ocean in the future. Currently the ocean absorbs about 25% of the carbon dioxide produced by burning fossil fuels. Most of this carbon is absorbed in the Southern Ocean (the region around Antarctica). How this will change in the future is poorly known. Models have difficulty representing physical conditions in the Southern Ocean accurately, thereby adding substantial uncertainty to projections of future ocean uptake of carbon dioxide. Results of the proposed study will provide a benchmark to test the ability of models to simulate ocean processes under climate conditions distinctly different from those that occur today, ultimately leading to improvement of the models and to more reliable projections of future absorption of carbon dioxide by the ocean.
The proposed work will add a research component to an existing scientific expedition to the Southern Ocean, in the region between the Ross Sea and New Zealand, that will collect sediment cores at three to five locations down the northern flank of the Pacific-Antarctic Ridge at approximately 170°W. The goal is to collect sediments at each location deposited since early in the peak of the last ice age. This region is unusual in the Southern Ocean in that sediments deposited during the last ice age contain foraminifera, tiny organisms with calcium carbonate shells, in much greater abundance than in other regions of the Southern Ocean. Foraminifera are widely used as an archive of several geochemical tracers of past ocean conditions. In the proposed work the radiocarbon age of foraminifera that inhabited the surface ocean will be compared with the age of contemporary specimens that grew on the seabed. The difference in age between surface and deep-swelling organisms will be used to discriminate between two proposed mechanisms of deep water renewal during the ice age: formation in coastal polynyas around the edge of Antarctica, much as occurs today, versus formation by open-ocean convection in deep-water regions far from the continent. If the latter mechanism prevails, then it is expected that surface and deep-dwelling foraminifera will exhibit similar radiocarbon ages. In the case of dominance of deep-water formation in coastal polynyas, one expects to find very different radiocarbon ages in the two populations of foraminifera. In the extreme case of greater ocean stratification during the last ice age, one even expects the surface dwellers to appear to be older than contemporary bottom dwellers because the targeted core sites lie directly under the region where the oldest deep waters return to the surface following their long circuitous transit through the deep ocean. The primary objective of the proposed work is to reconstruct the water mass age structure of the Southern Ocean during the last ice age, which, in turn, is a primary factor that controls the amount of carbon dioxide stored in the deep sea. In addition, the presence of foraminifera in the cores to be recovered provides a valuable resource for many other paleoceanographic applications, such as: 1) the application of nitrogen isotopes to constrain the level of nutrient utilization in the Southern Ocean and, thus, the efficiency of the ocean?s biological pump, 2) the application of neodymium isotopes to constrain the transport history of deep water masses, 3) the application of boron isotopes and boron/calcium ratios to constrain the pH and inorganic carbon system parameters of ice-age seawater, and 4) the exploitation of metal/calcium ratios in foraminifera to reconstruct the temperature (Mg/Ca) and nutrient content (Cd/Ca) of deep waters during the last ice age at a location near their source near Antarctica.
Note: Project Acronym \"SNOWBIRDS\" = Silicon and Nitrogen Observed in the Water column Biologic Isotope Records During Sedimentation";
String projects_0_end_date "2020-05";
String projects_0_geolocation "Pacific Southern Ocean (170ºW from 67ºS to 54ºS)";
String projects_0_name "Water Mass Structure and Bottom Water Formation in the Ice-age Southern Ocean";
String projects_0_project_nid "810779";
String projects_0_project_website "https://www.snowbirdstransect.org/";
String projects_0_start_date "2016-06";
String publisher_name "Biological and Chemical Oceanographic Data Management Office (BCO-DMO)";
String publisher_type "institution";
String sourceUrl "(local files)";
Float64 Southernmost_Northing -66.841;
String standard_name_vocabulary "CF Standard Name Table v55";
String summary "This dataset contains depth profiles of seawater dissolved 232Th, 230Th, and 231Pa from cruise NBP1702 (GEOTRACES-compliant).";
String time_coverage_end "2017-02-28T17:01Z";
String time_coverage_start "2017-01-29T02:32Z";
String title "[NBP1702 Dissolved Th and Pa] - Depth profiles of seawater dissolved 232Th, 230Th, and 231Pa from RVIB Nathaniel B. Palmer cruise NBP1702 from January to March 2017 (Water Mass Structure and Bottom Water Formation in the Ice-age Southern Ocean)";
String version "1";
Float64 Westernmost_Easting -173.907;
String xml_source "osprey2erddap.update_xml() v1.5";
}
}
Data Access Protocol (DAP) and its
selection constraints.
The URL specifies what you want: the dataset, a description of the graph or the subset of the data, and the file type for the response.
Tabledap request URLs must be in the form
https://coastwatch.pfeg.noaa.gov/erddap/tabledap/datasetID.fileType{?query}
For example,
https://coastwatch.pfeg.noaa.gov/erddap/tabledap/pmelTaoDySst.htmlTable?longitude,latitude,time,station,wmo_platform_code,T_25&time>=2015-05-23T12:00:00Z&time<=2015-05-31T12:00:00Z
Thus, the query is often a comma-separated list of desired variable names,
followed by a collection of
constraints (e.g., variable<value),
each preceded by '&' (which is interpreted as "AND").
For details, see the tabledap Documentation.