Study Sea Ice (SSI)

This project aims to map the behaviour of sea ice.

The following three sea ice datasets from the Copernicus Marine Environment Monitoring Service are each less than 10 GiB.

• SEAICE_ANT_SEAICE_L4_NRT_OBSERVATIONS_011_012 is "Antarctic Ocean - Sea Ice Edge from SAR".
• SEAICE_ARC_SEAICE_L3_NRT_OBSERVATIONS_011_014 is "Sea Ice Thickness derived from merging CryoSat-2 and SMOS ice thickness".
• SEAICE_BAL_SEAICE_L4_NRT_OBSERVATIONS_011_004 is "Baltic Sea - Sea Ice Concentration and Thickness Charts".
  • The User Manual states that "The SAR-based products have an individual grid depending on the source SAR data. The ice chart grid-based products have a fixed grid of 1223 (x) by 1445 (y) grid points, int latlong coordinate system. The upper left corner is (x,y)=(9.0,66.2) degrees, and the resolution is (dx,dy)=(0.018,0.009) degrees. The reference ellipsoid is WGS84". This statement does agree with the values in the NetCDF (but only if you don't care about sub-percentage level differences).
  • The User Manual states that: "Geographical coverage = Baltic Sea 9°E 🡪 30°30’E ; 53°40’N 🡪 66°N" and "Horizontal resolution = 1km". This statement does not agree with the values in the NetCDF.
  • The User Manual states that: "The nominal resolution is about 1km". This statement does not agree with the values in the NetCDF (unless "about" means "to within 20% of").
  • The User Manual states that the NetCDF schema is:

dimensions:
    time = 1 ;
    xc = 3812 ;
    yc = 2980 ;

variables:
    int time(time) ;
        time:long_name = "reference time of sea ice file" ;
        time:units = "seconds since 1981-01-01 00:00:00" ;
    float yc(yc) ;
        yc:axis = "Y" ;
        yc:long_name = "y-coordinate in Cartesian system" ;
        yc:units = "m" ;
    float xc(xc) ;
        xc:axis = "X" ;
        xc:long_name = "x-coordinate in Cartesian system" ;
        xc:units = "m" ;
    float lat(yc, xc) ;
        lat:long_name = "latitude" ;
        lat:units = "degrees_north" ;
    float lon(yc, xc) ;
        lon:long_name = "longitude" ;
        lon:units = "degrees_east" ;
    char crs ;
        crs:grid_mapping_name = "polar_stereographic" ;
        crs:straight_vertical_longitude_from_pole = 0.f ;
        crs:latitude_of_projection_origin = 90.f ;
        crs:standard_parallel = 90.f ;
        crs:false_easting = 0.f ;
        crs:false_northing = 0.f ;
        crs:proj4_string = "+proj=stere lon_0=0.0 lat_ts=90.0 lat_0=90.0 a=6371000.0 b=6371000.0" ;
    short ice_concentration(time, yc, xc) ;
        ice_concentration:long_name = "sea ice concentration" ;
        ice_concentration:standard_name = "sea_ice_area_fraction" ;
        ice_concentration:units = "%" ;
        ice_concentration:coordinates = "lon lat" ;
        ice_concentration:grid_mapping = "crs" ;
        ice_concentration:source = "met.no" ;
        ice_concentration:_FillValue = -99s ;
        ice_concentration:scale_factor = 1.f ;
        ice_concentration:add_offset = 0.f ;
    short concentration_range(time, yc, xc) ;
        concentration_range:long_name = "concentration range" ;
        concentration_range:units = "%" ;
        concentration_range:coordinates = "lon lat" ;
        concentration_range:grid_mapping = "crs" ;
        concentration_range:_FillValue = -99s ;
        concentration_range:comments = "Range of the analyzed ice concentration value" ;

If you register for a free account at Copernicus Marine Environment Monitoring Service you can then put your account information in a file called "~/.netrc" using the format machine nrt.cmems-du.eu login USERNAME password PASSWORD. Then, after installing lftp, you can download datasets with a command along the lines of lftp -c "open --user USERNAME ftp://nrt.cmems-du.eu; mirror -ep Core/SEAICE_BAL_SEAICE_L4_NRT_OBSERVATIONS_011_004/ Copernicus/SEAICE_BAL_SEAICE_L4_NRT_OBSERVATIONS_011_004/". This command can be repeated later to just update your local mirror with new files.

Workflow

1. Download the entire SEAICE_BAL_SEAICE_L4_NRT_OBSERVATIONS_011_004 dataset (by running lftp as outlined above)
2. Check the data (by running step0_checkData.py)
3. Create PNG maps of Baltic Sea sea ice concentration (by running step1_createMaps.py)
4. Create CSV histograms of Baltic Sea sea ice concentration (by running step2_createHistograms.py)
5. Create PNG plots of Baltic Sea sea ice concentration (by running step3_createPlots.py)
6. Create PNG frames and MP4 videos of Baltic Sea sea ice concentration (by running step4_createFrames.py)

Output

The output of step2_createHistograms.py is:

Summarising ...
The highest single non-zero occurrence is 370,494.9 km².
The highest 100%-concentration equivalent occurrence is 373,040.8 km².
Saving trends ...
2018 = 6,990,036.8 km².day
2019 = 4,144,119.0 km².day
2020 = 1,464,738.5 km².day
2021 = 4,572,266.4 km².day
2022 = 5,082,399.6 km².day
2023 = 4,369,252.4 km².day
2024 = 6,867,013.0 km².day
2025 = 2,669,228.0 km².day
2026 = 6,344,515.5 km².day

Dependencies

SSI requires the following Python modules to be installed and available in your PYTHONPATH.

• matplotlib
• numpy
• PIL
• pyguymer3
• scipy
• shapely