Untitled Document

4.Presentation of Hydrochemical Information

| 4.1. Data Set of Initial Measurements.
| 4.2. Gridded Climatic Fields of the Objective Analysis.
| 4.3. Profiles, Transects and Fields.

4.1. Data Set of Initial Measurements

All the materials of hydrochemical observations, available to the authors, were accumulated in digital data set of initial measurements in the same format, as they had been stored in different sources. We had no opportunity to collect hydrochemical information only from primary sources. For example, some information was used that had been collected by NODC from different sources and placed in the Atlas of the World Ocean 2000. Therefore, the collected data set of initial data is rather heterogeneous by quality.

The data set of initial measurements was not subjected to quality control of observations. Therefore, it contains errors of different type: wrong coordinates, time, measurement errors, wrong measurement units, errors of operators by data input in tables, etc. According to our assessment, total percentage of rejects for different characteristics varies from 5% to 15% (See Table 3.1., Section 3).

Nevertheless, it has been assumed appropriate to place all the initial information in the Atlas, according to the following arguments. Methods of measurement quality control can be altered in the process of hydrochemical information accumulation. It may be supposed that attitude will vary in future to those data that were rejected according to the procedure accepted in this Atlas. Therefore, it is important to keep the information in its primary form for future investigators.

The data set of initial measurements is placed in the directory "Data" on CD-ROM (ASCII file AO_CHEM.TXT). This format allow us to use the data in the mode of the software Ocean Data View (Schlitzer 2001). The Ocean Data View is attached.

For convenience of possible calculations and data manipulation, the data set of initial measurements was loaded in the database of hydrochemical data (DBHD) by management of DBMS VisualFoxPro 3.0. The database is of a relation character and consists of the following two tables mutually interconnected by the attribute "unique station number in the DBHD".

The table of hydrochemical station general attributes (Headers) contains the following:

- Unique station number in the DBHD (un);
- Name of vessel or research platform (cruise);
- Number of the station in the cruise (expedition);
- Date of station performance (dat);
- Geographical coordinates of the station (lat, lon);
- Station depth (depth);
- Quality flag of the general attributes of this station (fq_st).

The table of hydrochemical data at these stations (Data_chem) contains the following attributes:

- Unique station number in the DBHD (un);
- Observation depth (level) [m];
- Reliability flag of the observation depth (fq_level);
- Concentration of dissolved oxygen at the observation depth (oxy);
- Reliability flag of the concentration of dissolved oxygen (fq_oxy);
- pHB [Buch units] at the observation depth (phb);
- Reliability flag of the pHB (fq_phb);
- Alkalinity (Alk) [mg-equivalent/l] at the observation depth (alk);
- Reliability flag of the alkalinity (fq_alk);
- Silicate [ µmol/l] at the observation depth (sil);
- Reliability flag of the silicate (fq_sil);
- Phosphate [ µmol/l] at the observation depth (po4);
- Reliability flag of the phosphate (fq_po4);
- Nitrite [ µmol/l] at the observation depth (no2);
- Reliability flag of the nitrite (fq_no2);
- Nitrate [ µmol/l] at the observation depth (no3);
- Reliability flag of the nitrate (fq_no3).

4.2. Gridded Climatic Fields of the Objective Analysis.

The database of the hydrochemical data, that had passed the quality control, was used for the objective analysis (See Section 3). Working array contained concentrations of dissolved oxygen, phosphate, silicate, pH, total alkalinity, nitrite and nitrate for each year at the standard depths. Geographical coordinates of each station were converted to coordinates of the Lambert projection which had been also used for construction of fields of the hydrochemical characteristics in nodes of the regular grid. Synoptic and meso-scale variations of the hydrochemical characteristics were not taken into account, they were considered as a statistical noise. Appropriate filtration was carried out on the basis of the EOF decompositions described in Section 3.4.

The array of values at the standard depths was subjected to spectral analysis with a use of procedures described in Section 3.4. Eigenvalues and values of the principal components were obtained in the result of this analysis, and gridded climatic fields of the hydrochemical elements were calculated on their basis. The grid with grid spacing 200 km is demonstrated in Fig. 4.1.

Distribution fields of phosphate and silicate at 5 m depth are shown as examples in Fig. 4.2. Maps constructed on the basis of data of the statistical analysis for boxes with centers located in the grid nodes are shown for comparison in the same figures. As one can see in these figures, results of the objective analysis correspond closely to results of the statistical analysis.

Numerical values of the gridded climatic fields (dissolved oxygen, phosphate, silicon, pHB, total alkalinity, nitrite and nitrate) are placed in the subdirectory "Gridded_Data\Txt" as the ASCII-files.

Fig. 4.1. Square grid (a - 200x200 km) used for calculation of climatic characteristics of the hydrochemical elements. Characteristics were calculated for centers of the squares.

a | b
c | d

Fig. 4.2. Phosphate [µ mol/l] , summer, 5 m depth: a - mean value in squares 200x200 km (17 - number of stations); b - gridded field.

Silicate [ µmol/l] , winter, 5 m depth: c - mean value in squares 200x200 km (17 - number of stations); d - gridded field.

4.3. Profiles, Transects and Fields.

Results of the statistical and objective analysis were used for construction of vertical and horizontal distributions of the hydrochemical elements in the Arctic Ocean.

Data of the statistical analysis and data interpolated at the standard depths were used for construction of vertical profiles.

Climatic values of the elements at the standard depths, obtained using the objective analysis, were used for construction of the transects (Fig. 4.3.). Examples of the mean profiles of silicate in Square No. 5 and vertical climatic silicate distribution at Transect No. 12 (See Fig. 4.3) are shown in Fig. 4.4 and 4.5. The vertical profiles of the elements and their distribution at the transects are given in WEB-version.

Fig. 4.3. Scheme of transects and squares, for which vertical profiles were calculated

a | b

Fig. 4.4. Mean profiles and values (data at the standard depths) of silicate concentration [µ mol/l] (a - winter, b - summer) for square No. 5 200x200 km (See Fig. 4.3).

Fig. 4.5. Silicate distribution [ µmol/l], Transect No. 12 (See Fig. 4.3), winter.

Element values at the standard depths, obtained in the result of the statistical and objective analysis, were used for construction of climatic maps.