Seasonal mean Arctic Ocean climatology calculated from the archived data (ADAM: Arctic ocean Data Archive for Model validation & data assimilation) beta-version 2016.08.16 by Hiroshi Sumata (AWI) contact address: hiroshi.sumata@awi.de

The yellow colored data were used to calculate statistics for the data screening, but not used to calculate the climatology.

Spatial distribution of archived TS data (1980-2015) Figure 1: Distribution of archived TS data at (a) 0 - 20m depth range and (b) 200 - 250m depth range.

1. Duplication check applied for the archived data The duplication check was performed by comparisons of all combination of point measurements, not by comparisons of vertical CTD profiles. The first duplication check was performed based on difference of geographical location, temperature, salinity, time stamp, and measurement depth. The second duplication check was performed by difference of time stamp and distance [km] between the two measurement (in order to avoid the effect of meridinan convergence toward the North Pole) If duplications are found, a datum from reliable source is retained. 2. Remove apparently false data Temperature values below -2.2 degree or over 40 degree are removed as false data. Salinity values below 0 psu or over 40 psu are removed as false data. If the measurement depth is more than 20m deeper than the sea floor (defined by merged-IBCAO-ETOPO5), the data are removed. Data are retained only if both temperature and salinity are given by valid values (i.e., if one of the values is missing or false data, the data are removed). 3. Combined grid-based and area-based statistical screening Define 111 × 111 km squared grid cell (1 × 1 degree at the Equator scale) over the entire Arctic. Define mean and standard deviation of temperature and salinity at each grid cell and at each depth level by all data contained in the surrounding 555× 555 km (5 × 5 degree) area. (Figure 3) Apply a grid-based statistical screening with μ±5σ threshold in each grid cell and depth level (repeat twice) Define mean and standard deviation of temperature and salinity in each basin-wide area according to the area division shown in Figure 2b. Apply area-based statistical screening with μ±5σ threshold below 750m depth (repeat twice). (Figure 4, 5 and 6)

(b) Area mask for statistical screening 1. Amerasian Basin (depth > 1000m) 2. Amerasian shelf & shelf slope (0 < depth < 1000m) 3. Siberian shelf & shelf slope (0 < depth < 1000m) 4. Eurasian Basin (depth > 1000m) 5. Barents, Kara Sea and shelf slope (0 < depth < 1000m) 6. GIN Sea (depth > 1000m) Figure 2: (a) division of vertical levels. The archived TS data are classified into 50 levels according to their measurement depth. Data from an identical CTD profile are averaged over each depth range and regarded as one measurement. (b) Area mask for statistical screening. In the 2nd step of statistical screening, the archived data are classified into 6 different area according to their geographical location, and area-based screening is applied.

(b) (a) (c) (d) (e) Figure 3: Statistics used for grid-based statistical screening:(a) number of data used to define mean and standard deviation on each 1 x 1 degree grid cell, spatial distribution of (b) mean and (c) standard deviation of temperature and those of salinity (d, e).

Fig. 4: Temerature (left panel) and salinity (right panel) distribution in the Amerasian basin (see Figure 2b for area definition) after a combined statistical screening. The blue dots denote data distribution after the screening, while the light-blue (green) dots denotes data removed by grid-based (area-based) statistical screening. The red line denotes the mean (µ) in each depth level after the screening, the solid and dotted black lines indicate μ±5σ and μ±10σ in each depth level, respectively.

Calculate seasonal mean climatology by spatial & temporal intnerporation Define 4 seasons by JFM (season = 1), AMJ(season = 2), JAS(season = 3), OND(season = 4). Calculate seasonal mean climatology of temperature and salinity by the average of data contained in each 1 x 1 degree grid cell. If the number of available data at a certain grid cell is less than 3, climatology is not defined on the cell. If the climatological value is not defined after the 3rd step, no seasonal interpolation/extraporation are done. Program: prog_v12_frank/archive_data_gridding_seasonal_int.f90 Output data: archive_v12_QC2_3_DPL_checked_2d_seaosn_int.nc