BCO-DMO ERDDAP
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Row Type Variable Name Attribute Name Data Type Value
attribute NC_GLOBAL cdm_data_type String Other
attribute NC_GLOBAL Conventions String COARDS, CF-1.6, ACDD-1.3
attribute NC_GLOBAL creator_email String info at bco-dmo.org
attribute NC_GLOBAL creator_name String BCO-DMO
attribute NC_GLOBAL creator_url String https://www.bco-dmo.org/ (external link)
attribute NC_GLOBAL doi String 10.26008/1912/bco-dmo.925726.1
attribute NC_GLOBAL Easternmost_Easting double -105.7
attribute NC_GLOBAL geospatial_lon_max double -105.7
attribute NC_GLOBAL geospatial_lon_min double -115.2
attribute NC_GLOBAL geospatial_lon_units String degrees_east
attribute NC_GLOBAL geospatial_vertical_max double 3500.0
attribute NC_GLOBAL geospatial_vertical_min double 6.0
attribute NC_GLOBAL geospatial_vertical_positive String down
attribute NC_GLOBAL geospatial_vertical_units String m
attribute NC_GLOBAL infoUrl String https://www.bco-dmo.org/dataset/925726 (external link)
attribute NC_GLOBAL institution String BCO-DMO
attribute NC_GLOBAL license String The data may be used and redistributed for free but is not intended\nfor legal use, since it may contain inaccuracies. Neither the data\nContributor, ERD, NOAA, nor the United States Government, nor any\nof their employees or contractors, makes any warranty, express or\nimplied, including warranties of merchantability and fitness for a\nparticular purpose, or assumes any legal liability for the accuracy,\ncompleteness, or usefulness, of this information.
attribute NC_GLOBAL sourceUrl String (local files)
attribute NC_GLOBAL summary String Understanding the cycling of chromium (Cr) and how chromium stable isotopes (δ53Cr) are altered in response to different processes in the modern ocean is important in our interpretation of marine sedimentary δ53Cr records, a promising redox proxy. Therefore, it is crucial to investigate the geochemical processes of Cr in reducing environments such as oxygen deficient zones (ODZs). In this study, we investigated the cycling of Cr in the Eastern Tropical North Pacific (ETNP) ODZ by analyzing the [Cr] and δ53Cr of total dissolved Cr and Cr(III). Our Cr(III) data at two inshore stations shows profile features and Cr reduction isotopic fractionation factor (-1.5‰) similar to an offshore station in a previous study. We also observed significant Cr scavenging signals in the upper 1000 meters (m) throughout the ODZ with an inshore-offshore variability in its magnitude. Specifically, anoxic bottom waters on the continental slope see the greatest Cr scavenging with heaviest δ53Cr (+1.85‰). Our estimates of the scavenged Cr isotopic composition are within error of the anoxic and euxinic marine sedimentary δ53Cr. This implies that the vertical transport of Cr to the seafloor and subsequent diagenesis may not generate significant isotopic fractionation for Cr. This is the first thorough investigation into the Cr cycling in the ETNP ODZ and demonstrated promising usage of marine sedimentary δ53Cr as a redox proxy for ancient oceans.\n\nIn the ODZ, oxygen is consumed by degrading sinking particles and reaches extremely low levels (too low to support aerobic life) from 100m to 800m depth. However, microbes that can use other oxidants such as nitrate to metabolize organic carbon live there, and we showed that they also convert soluble anionic chromate Cr(VI) to cationic Cr(III), about half of which is scavenged onto sinking particles and removed to the seafloor. This reduction is accompanied by preferential reduction of light Cr isotopes, so the Cr(III) is 1.3‰ lighter than the source Cr(VI). The removal of part of this light Cr(III) by scavenging leaves the residual total Cr heavier than the source Cr. The analyzed samples listed here were chosen to be from the center and margins of the ETNP ODZ and over extremely reducing continental margin sediments.
attribute NC_GLOBAL title String [Total dissolved Cr concentration and isotopic composition in the ETNP from RR1804-05 and KM1919-20] - Total dissolved chromium (Cr) concentration and isotopic composition in the Eastern Tropical North Pacific from samples collected on R/V Roger Revelle and R/V Kilo Moana in April-May 2018 and Sept-Oct 2019 (Cr Isotope Oceanography of the Eastern Tropical North Pacific Ocean)
attribute NC_GLOBAL Westernmost_Easting double -115.2
variable Cruise String
attribute Cruise long_name String Cruise
attribute Cruise units String unitless
variable Station String
attribute Station long_name String Station
attribute Station units String unitless
variable Latitude float
attribute Latitude actual_range float 15.1, 27.1
attribute Latitude long_name String Latitude
attribute Latitude units String degrees_north
variable longitude float
attribute longitude _CoordinateAxisType String Lon
attribute longitude actual_range float -115.2, -105.7
attribute longitude axis String X
attribute longitude ioos_category String Location
attribute longitude long_name String Longitude
attribute longitude standard_name String longitude
attribute longitude units String degrees_east
variable depth int
attribute depth _CoordinateAxisType String Height
attribute depth _CoordinateZisPositive String down
attribute depth actual_range int 6, 3500
attribute depth axis String Z
attribute depth ioos_category String Location
attribute depth long_name String Depth
attribute depth positive String down
attribute depth standard_name String depth
attribute depth units String m
variable CTD_Oxygen float
attribute CTD_Oxygen actual_range float 0.63, 231.18
attribute CTD_Oxygen long_name String Ctd_oxygen
attribute CTD_Oxygen units String micromoles per kilogram (umol/kg)
variable total_dissolved_Cr float
attribute total_dissolved_Cr actual_range float 2.26, 5.02
attribute total_dissolved_Cr long_name String Total_dissolved_cr
attribute total_dissolved_Cr units String nanomoles per kilogram (nmol/kg)
variable total_dissolved_d53Cr float
attribute total_dissolved_d53Cr actual_range float 0.6, 1.85
attribute total_dissolved_d53Cr long_name String Total_dissolved_d53cr
attribute total_dissolved_d53Cr units String permil (‰)

 
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