International circumpolar compilation of nutrient concentration data from Antarctic land-fast sea ice

Brief description

This dataset is an international circumpolar compilation of currently available macronutrient concentration data from Antarctic land-fast sea ice cores collected at locations around Antarctica between 1997 and 2021, covering the full seasonal cycle. These data have been compiled from peer-reviewed publications, field reports, data repositories and direct contributions from researchers and research teams from across the international scientific community working in sea-ice biogeochemistry. The dataset includes concentrations of nitrate, nitrite, ammonium, phosphate and silicic acid, as well as ancillary measurements (e.g., ice temperature, salinity and other biogeochemical measurements) where available. Observations of sea-ice properties were also taken at the time of sampling, including ice thickness, texture, structure and age, snow thickness, and freeboard level, and can be used to contextualise the biogeochemical data.

A total of 245 geo-referenced fast-ice cores are included in the compilation; 21 cores from the Indian Sector, 70 from the West Pacific Sector, 67 from the Ross Sea, 85 from the West Antarctic Peninsula, and 2 from the Weddell Gyre. 232 cores were from first-year ice, 12 cores were from multi-year ice and 1 was from second-year ice. Samples of sub-ice platelet layer ice and interstitial water (n=111) were collected in some studies and are included where available.

For fast-ice cores, most of the nutrient concentrations were measured as bulk nutrient concentrations of melted ice core sections (n=1914). Cores were collected from fast ice using ice corers (0.09 to 0.14 m diameter) and cut into sections of lengths ranging from 0.05 to 0.75 m (mean 0.15 m, median 0.12 m). Sections were cut using clean stainless-steel saws and then melted in the dark at ambient temperature or ≤4°C. A small number of measurements are from sea-ice brine samples, obtained by centrifugation of ice core sections (lengths 0.20 to 0.75 m, mean 0.34, median 0.30, n=22).

Nutrient concentrations were measured in filtered and unfiltered samples, either in laboratories on Antarctic research stations/ships shortly after melting or centrifugation, or in home laboratories following storage at ≤-18°C or by fixing with mercuric chloride and refrigeration at ≤4°C. The nutrient concentrations in this compilation are mostly from automated or manual colorimetric analysis (e.g., Hydes et al., 2010). Some studies analysed ammonium (NH4+) concentrations using ortho-phthaldialdehyde (OPA) and fluorometry (Holmes et al., 1999). Specific analytical protocols varied across studies, but in general calibration standards were prepared using artificial seawater or low-nutrient seawater with salinities similar to the samples being analysed to avoid matrix effects. Across all studies, recommended procedures were followed as closely as possible (Becker et al., 2020).

Nutrient concentrations from the sub-ice platelet layer were measured in unconsolidated platelets that were sieved and melted, in interstitial waters that were separated by sieving or filtration, and in mixtures of platelets and interstitial waters that were not separated. Analysis was conducted as for melted ice core sections.

The data are provided in two spreadsheets in .csv format. Henley-et-al-2023_Antarctic-fast-ice-nutrients_final.csv contains all data from ice cores and melted ice core sections. Henley-et-al-2023_Antarctic-fast-ice-nutrients_platelet.csv contains all data from the sub-ice platelet layer. Both spreadsheets contain all available data and supporting metadata. Each column heading is intended to be as informative as possible, and is given and described below.

These data were funded by the following bodies/projects:

Australian Antarctic Science project 4546
Other Australian Government funding: ASCI000002, SR200100008
Also UK Natural Environment Research Council grant NE/K010034/1

This data compilation and analysis were carried out under the auspices of the Scientific Community on Oceanic Research (SCOR) working group on Biogeochemical Exchange Processes at Sea-Ice Interfaces (BEPSII; WG-140).

This data compilation is the focus of Henley et al., 2023, Marine Chemistry. This paper provides more information about the data provided here and presents a detailed analysis of the results and scientific findings. This paper should be read by any person interested in using this compiled dataset and used alongside the dataset to inform and support any further analysis.

Column A – numerical order of data provided in the compilation
Cruise/Field Campaign – name of cruise or field campaign
Study (ice properties and nutrients) – name of study where ice properties and nutrients were measured, or name of data provider
Ice type (fast/pack) – ice type; for this compilation all ice core data are from fast ice
Ice type (age) – age of ice, in categories of first-year ice, second-year ice or multi-year ice
Ice texture (cruise/campaign) – ice texture described for the cruise or field campaign
Ice texture (section) – ice texture described for the ice core or section sampled
Comments (ice properties) – any additional comments recorded by the field team with respect to ice properties
Station Number – number or name of sampling station
Date (YYYYMMDD) – sampling date in the format YYYYMMDD
Date (DD/MM/YYYY) – sampling date in the format DD/MM/YYYY
Julian day – sampling date in the format julian day
Latitude – latitude of sampling location in decimal degrees
Longitude – longitude of sampling location in decimal degrees
Ice Core ID – ice core identifier code or name, as provided
Instrument type – name or description of instrument used for ice coring
Corer diameter (m) – diameter of ice corer, in metres
Ice Thickness (core length, m) – ice thickness determined from length of ice core, in metres
Snow Thickness (m) – snow thickness on top of sea ice, in metres
Freeboard (m) – the difference between the height of the sea ice upper surface and the seawater surface, in metres. A positive freeboard shows that the sea ice surface is above that of seawater; a negative freeboard shows that the sea ice surface is below that of seawater.
Comments (general) – any additional comments recorded by the field team
Extrapolation – whether all measurements were made directly or some extrapolated from other measurements. In the vast majority of cases, all measurements were made directly (Extrapolation = no). Where Extrapolation = yes, details of extrapolation are provided in Comments (general).
Ice Thickness (measured, m) – ice thickness measured by various methods. Where this differs from Ice Thickness (core length, m), measured ice thickness was greater than the length of core sampled and was measured as described in Comments (general).
Core depth (average, m) – depth of mid-point of core section, from top of core, in metres
Core depth (average, %) – depth of mid-point of core section, from top of core, normalised to ice core length, in percent
Core depth (T, m) – depth at which ice core temperature was measured, from top of core, in metres
Temperature (deg C) – ice core temperature in degrees Celsius
Lower Limit of Salinity Depth range (m) – depth of bottom of section for salinity measurement, from top of core, in metres
Upper Limit of Salinity Depth range (m) – depth of top of section for salinity measurement, from top of core, in metres
Salinity – salinity of melted ice core section, no units
Lower Limit of d18O Depth range (m) – depth of bottom of section for d18O measurement, from top of core, in metres
Upper Limit of d18O Depth range (m) – depth of top of section for d18O measurement, from top of core, in metres
d18O (‰) – stable isotope composition of oxygen (d18O) in melted ice core section, in per mille
Lower Limit of Chlorophyll Depth range (m) – depth of bottom of section for chlorophyll measurement, from top of core, in metres
Upper Limit of Chlorophyll Depth range (m) – depth of top of section for chlorophyll measurement, from top of core, in metres
Chlorophyll (ug.L-1) – chlorophyll concentration of melted ice core section, in µg L-1
Lower Limit of POC Depth range (m) – depth of bottom of section for POC measurement, from top of core, in metres
Upper Limit of POC Depth range (m) – depth of top of section for POC measurement, from top of core, in metres
POC (umol.L-1) – particulate organic carbon (POC) concentration of melted ice core section, in µmol L-1
Lower Limit of PON Depth range (m) – depth of bottom of section for PON measurement, from top of core, in metres
Upper Limit of PON Depth range (m) – depth of top of section for PON measurement, from top of core, in metres
PON (umol.L-1) – particulate organic nitrogen (PON) concentration of melted ice core section, in µmol L-1
Lower Limit of Nitrate Depth range (m) – depth of bottom of section for nitrate measurement, from top of core, in metres
Upper Limit of Nitrate Depth range (m) – depth of top of section for nitrate measurement, from top of core, in metres
Nitrate+Nitrite (umol.L-1) – nitrate+nitrite concentration of melted ice core section, in µmol L-1
Nitrate [NO3-] (umol.L-1) – nitrate concentration of melted ice core section, in µmol L-1
Lower Limit of Nitrite Depth range (m) – depth of bottom of section for nitrite measurement, from top of core, in metres
Upper Limit of Nitrite Depth range (m) – depth of top of section for nitrite measurement, from top of core, in metres
Nitrite [NO2-] (umol.L-1) – nitrite concentration of melted ice core section, in µmol L-1
Lower Limit of Ammonium Depth range (m) – depth of bottom of section for ammonium measurement, from top of core, in metres
Upper Limit of Ammonium Depth range (m) – depth of top of section for ammonium measurement, from top of core, in metres
Ammonium [NH4+] (umol.L-1) – ammonium concentration of melted ice core section, in µmol L-1
Lower Limit of Phosphate Depth range (m) – depth of bottom of section for phosphate measurement, from top of core, in metres
Upper Limit of Phosphate Depth range (m) – depth of top of section for phosphate measurement, from top of core, in metres
Phosphate [PO43-] (umol.L-1) – phosphate concentration (measured as total soluble reactive phosphorus) of melted ice core section, in µmol L-1
Lower Limit of Silicic Acid Depth range (m) – depth of bottom of section for silicic acid measurement, from top of core, in metres
Upper Limit of Silicic Acid Depth range (m) – depth of top of section for silicic acid measurement, from top of core, in metres
Silicic Acid [Si(OH)4] (umol.L-1) – silicic acid concentration (measured as total dissolved silicon) of melted ice core section, in µmol L-1
Lower Limit of DOC Depth range (m) – depth of bottom of section for DOC measurement, from top of core, in metres
Upper Limit of DOC Depth range (m) – depth of top of section for DOC measurement, from top of core, in metres
DOC (umol.L-1) – dissolved organic carbon (DOC) concentration of melted ice core section, in µmol L-1
Lower Limit of DON Depth range (m) – depth of bottom of section for DON measurement, from top of core, in metres
Upper Limit of DON Depth range (m) – depth of top of section for DON measurement, from top of core, in metres
DON (umol.L-1) – dissolved organic nitrogen (DON) concentration of melted ice core section, in µmol L-1
Nitrate+Nitrite_sal (umol.L-1) – nitrate+nitrite concentration of melted ice core section, normalised to seawater salinity value of 34.3, in µmol L-1
Nitrate [NO3-]_sal (umol.L-1) – nitrate concentration of melted ice core section, normalised to seawater salinity value of 34.3, in µmol L-1
Nitrite [NO2-]_sal (umol.L-1) – nitrite concentration of melted ice core section, normalised to seawater salinity value of 34.3, in µmol L-1
Ammonium [NH4+]_sal (umol.L-1) – ammonium concentration of melted ice core section, normalised to seawater salinity value of 34.3, in µmol L-1
Phosphate [PO43-]_sal (umol.L-1) – phosphate concentration of melted ice core section, normalised to seawater salinity value of 34.3, in µmol L-1
Silicic Acid [Si(OH)4]_sal (umol.L-1) – silicic acid concentration of melted ice core section, normalised to seawater salinity value of 34.3, in µmol L-1

The majority of columns are common between both spreadsheets. The only columns where the platelet ice spreadsheet differs from the ice core one are as follow.

Ice type (platelet) – type of sample from sub-ice platelet layer. plate/int = mixed platelet ice and interstitial waters; UPI = unconsolidated platelet ice; IW = interstitial water; BI = bottom ice; GI = granular ice. In each case, further details are given in Comments (ice properties) and Comments (general). Where IW is accompanied by a depth, this is the depth from the top of the platelet layer (interface with bottom ice) in centimetres.
Ice Thickness (m) – ice thickness determined from lengths of ice cores, in metres
Depth (#, m) – depth of sampling from the top of the platelet layer (interface with bottom ice), in metres, or depth code as provided

For questions about this dataset please contact Dr Sian Henley using the contact details provided.


References used in dataset description

Becker, S., Aoyama, M., Woodward, E. M. S., Bakker, K., Coverly, S., Mahaffey, C., and Tanhua, T. (2020). GO-SHIP Repeat Hydrography Nutrient Manual: The Precise and Accurate Determination of Dissolved Inorganic Nutrients in Seawater, Using Continuous Flow Analysis Methods. Frontiers in Marine Science, 7. doi: 10.3389/fmars.2020.581790

Holmes, R. M., Aminot, A., Kerouel, R., Hooker, B. A., and Peterson, B. J. (1999). A simple and precise method for measuring ammonium in marine and freshwater ecosystems. Canadian Journal of Fisheries and Aquatic Sciences, 56(10), 1801-1808. doi: 10.1139/cjfas-56-10-1801

Hydes, D. J., Aoyama, M., Aminot, A., Bakker, K., Becker, S., Coverly, S., Daniel, A., Dickson, A. G., Grosso, O., Kerouel, R., van Ooijen, J., Sato, K., Tanhua, T., Woodward, E. M. S., and Zhang, J. Z. (2010). Determination of Dissolved Nutrients (N, P, SI) in Seawater With High Precision and Inter-Comparability Using Gas-Segmented Continuous Flow Analysers. In E. M. Hood, C. L. Sabine, and B. M. Sloyan (Eds.), The GO-SHIP Repeat Hydrography Manual: A Collection of Expert Reports and Guidelines. Version 1. (Vol. IOCCP Report Number 14). doi: http://dx.doi.org/10.25607/OBP-15

Lineage

Progress Code: completed

Statement: Contributed data were quality-controlled by individual data contributors, and then the compiled dataset underwent further quality control and quality assurance checks. Any data identified as being erroneous or unreliable were removed prior to data analysis and interpretation and are not included in this compilation.