OSI SAF (sea ice drift)¶

EUMETSAT OSI SAF Global Low Resolution Sea-Ice Drift (OSI-405-d) / Global Low Resolution Sea-Ice Drift data record (OSI-455) and Interim Climate Data Record (OSI-435)

Available

At a glance¶

Note on period: OSI-455 covers 1991-01-01 to 2020-12-31 (both hemispheres, year-round). The demonstrational ICDR OSI-435 starts on 2021-01-01 and covers 2021–2025 (the product page gives no exact last date). The NRT OSI-405 series runs from 2009 and is updated daily as of 2026-10-12 (the FTP prod folder holds the last 31 days; the archive folder holds the full record). We could not open the THREDDS or FTP listings, so the date of the latest file was not checked.

Overview¶

Gridded sea-ice drift vector fields for both hemispheres, retrieved by EUMETSAT OSI SAF from passive microwave (AMSR2 and AMSR3; formerly SSM/I, SSMIS and AMSR-E) and ASCAT scatterometer imagery with the Continuous Maximum Cross-Correlation (CMCC) method. The NRT product OSI-405-d delivers 48-hour displacements on a 62.5 km polar stereographic grid every day. The climate data record OSI-455 gives year-round 24-hour displacements on the 75 km EASE2 grid for 1991–2020, with summer seasons gap-filled by a free-drift model forced with ERA5 10 m winds. Every vector carries an uncertainty (1 standard deviation) and a status flag.

What changes with the successor¶

OSI-405-c → OSI-405-d¶

Transition: 2025-03

On 4 March 2025 all distribution channels switched from OSI-405-c to OSI-405-d. The method, grid and 48-hour displacement are unchanged; the update moved files to NetCDF4, switched ASCAT from Metop-B to Metop-C and changed the global attributes. Removal of SSMIS input (17 July 2025) and the move to AMSR3 (1 September 2026) followed under the same product ID.

Sources: OSI SAF service message #3193 (2025-03-03): New sea ice emissivity and LR sea ice drift products · OSI-405-d product page · OSI SAF — Implications of the end of SSMIS data on OSI SAF products · OSI SAF service message #3571 (2026-08-31): Operational release of AMSR3-based sea-ice products on 1st September 2026

Available variables¶

Variables in the merged files (multi-oi for OSI-405-d, merged for OSI-455) as listed in the OSI-405-d PUM v1.9 and the OSI-455 PUM v1.0. Variable names are mostly the same in both products; only the per-vector time offsets differ (dt0/dt1 in OSI-405-d, t0/t1 in OSI-455). The fill value for floating-point variables is -1e10.

instantaneous mean accumulated maximum minimum static — instantaneous: value at the time stamp · mean/accumulated/maximum/minimum: over the indicated interval · static: does not change with time

Ice displacement¶

Position and time¶

Quality information¶

The full variable list is in the official documentation.

How to get the data¶

• OSI SAF product page — OSI-405-d (near real time) — Web / FTP (ftp://osisaf.met.no/prod/ice/drift_lr/ last 31 days, ftp://osisaf.met.no/archive/ice/drift_lr/ full archive) / EUMETCast No login needed
  • The FTP server has merged and single_sensor folders. EUMETCast carries only the merged (multi-sensor) files.
• MET Norway THREDDS — OSI SAF sea-ice drift catalogue — THREDDS / OPeNDAP / HTTP No login needed
  • No account needed. The climate data record (OSI-455) is at https://thredds.met.no/thredds/catalog/osisaf/osisaf_cdrseaicedrift.html
• OSI SAF product page — OSI-455 (climate data record, 1991–2020) — FTP (ftp://osisaf.met.no/reprocessed/ice/drift_lr/v1/) / THREDDS / EUMETSAT Data Store No login needed
  • Merged files are under merged/YYYY/MM/; per-sensor and ERA5-wind files are under single_sensor//YYYY/MM/.
• OSI SAF product page — OSI-435 (demonstrational ICDR, 2021–2025) — FTP (ftp://osisaf.met.no/reprocessed_test/ice/drift_lr_icdr/v1) / THREDDS No login needed
  • A demonstrational climate product, served from the test FTP area (reprocessed_test); no DOI or recommended citation yet.
• C3S Climate Data Store — Sea ice drift daily gridded data derived from satellite observations — Web download / CDS API
  • Redistribution of OSI-455 (1991–2020, version 1.0). Requires an ECMWF account; no updates expected.
• Copernicus Marine — SEAICE_GLO_SEAICE_L4_NRT_OBSERVATIONS_011_001 — Web download / copernicusmarine toolbox
  • NRT redistribution listed on the OSI-405-d product page. Requires a Copernicus Marine account.

Example code¶

Opens an OSI-405-d Northern Hemisphere merged file downloaded from FTP or THREDDS. File names follow ice_drift_polstere-625_multi-oi-.nc (times as YYYYMMDDhhmm). OSI-455 files follow ice_drift__ease2-750_cdr-v1p0-_24h-.nc (the source part is left out for merged files); check the exact names in the FTP listing.

import numpy as np
import xarray as xr

ds = xr.open_dataset("ice_drift_nh_polstere-625_multi-oi_202401011200-202401031200.nc")
dX = ds["dX"].squeeze()            # km, 48-hour displacement along grid x
dY = ds["dY"].squeeze()
flag = ds["status_flag"].squeeze()

# Actual elapsed time per vector = (time_bnds[1] + dt1) - (time_bnds[0] + dt0)
tb = ds["time_bnds"].squeeze().values
span_s = (tb[1] - tb[0]) / np.timedelta64(1, "s") + ds["dt1"].squeeze() - ds["dt0"].squeeze()

speed_cm_s = np.hypot(dX, dY) * 1e5 / span_s       # km -> cm; mean speed over the period
good = flag >= 20                                  # 20-30: valid vectors (30 = nominal quality)
print(float(speed_cm_s.where(good).mean()), "cm/s")

Practical tips¶

• dX and dY are displacements in km over 48 h (OSI-405-d) or 24 h (OSI-455), along the grid x and y axes rather than east and north. Before comparing with winds or currents, divide by the elapsed time and recompute the direction from the start (lat, lon) and end (lat1, lon1) positions.
• OSI-405-d is issued daily but each file spans 48 h, so consecutive files overlap by 24 h. Account for this when building daily series or counting independent samples.
• Summer melt makes satellite tracking unreliable. OSI-405-d has summer vectors (NH 1 May–1 Oct, SH 1 Nov–1 Apr) only in the merged files, and most OSI-455 summer values (NH Jun–Sep, SH Nov–Feb) come from the ERA5-wind free-drift model. Use status_flag to see where each vector comes from.
• OSI-455 combines different inputs over time (SSM/I and SSMIS near 90 GHz, AMSR-E and AMSR2 at 36.5 GHz), and its merged files fill remaining gaps by spatial interpolation and wind vectors. Its grid (75 km EASE2) and period (24 h) also differ from OSI-405-d (62.5 km polar stereographic, 48 h), so do not splice the two into one series.
• For a CDR-consistent record after 2020, the demonstrational ICDR OSI-435 (2021–2025) is currently the only option. It has no DOI yet and lives in the reprocessed_test folder, so record the product ID and download date in publications and check later whether it becomes operational.

Notices and change history¶

References for your paper¶

Dataset citation¶

NRT — OSI-405-d — DOI 10.15770/EUM_SAF_OSI_NRT_2007

@misc{osisaf405d,
  author    = {{EUMETSAT Ocean and Sea Ice Satellite Application Facility}},
  title     = {Global Low Resolution Sea Ice Drift, {OSI-405-d}},
  year      = {2025},
  publisher = {EUMETSAT OSI SAF},
  doi       = {10.15770/EUM_SAF_OSI_NRT_2007}
}

Climate data record — OSI-455 (v1, 1991–2020) — DOI 10.15770/EUM_SAF_OSI_0012

@misc{osisaf455,
  author    = {{EUMETSAT Ocean and Sea Ice Satellite Application Facility}},
  title     = {Global Low Resolution Sea Ice Drift data record 1991-2020 (v1, 2022), {OSI-455}},
  year      = {2022},
  publisher = {EUMETSAT OSI SAF},
  doi       = {10.15770/EUM_SAF_OSI_0012}
}

C3S CDS copy of OSI-455 (the CDS page gives only the DOI) — DOI 10.24381/8e7af13d

Reference papers¶

OSI-455 climate data record paper — DOI 10.5194/essd-15-5807-2023

@article{lavergne2023drift,
  author  = {Lavergne, Thomas and Down, Emily},
  title   = {A climate data record of year-round global sea-ice drift from the {EUMETSAT} {Ocean and Sea Ice Satellite Application Facility} ({OSI SAF})},
  journal = {Earth System Science Data},
  volume  = {15},
  number  = {12},
  pages   = {5807--5834},
  year    = {2023},
  doi     = {10.5194/essd-15-5807-2023}
}

CMCC motion-tracking method paper — DOI 10.1029/2009JC005958

@article{lavergne2010cmcc,
  author  = {Lavergne, T. and Eastwood, S. and Teffah, Z. and Schyberg, H. and Breivik, L.-A.},
  title   = {Sea ice motion from low-resolution satellite sensors: An alternative method and its validation in the {Arctic}},
  journal = {Journal of Geophysical Research: Oceans},
  volume  = {115},
  number  = {C10},
  pages   = {C10032},
  year    = {2010},
  doi     = {10.1029/2009JC005958}
}

Acknowledgements¶

Under CC BY 4.0 you must include attribution to "EUMETSAT OSI SAF" and give the DOI of each product used (OSI-405-d, OSI-455). The demonstrational ICDR OSI-435 has no DOI or recommended citation as of October 2026; cite the product ID, FTP path and download date instead.

Information on the datasets used in this study was compiled with the help of the Korean Climate Data Navigator (KCDN) (Sim, 2026; https://doi.org/10.5281/zenodo.23300923).

Links¶

• OSI-405-d Product User Manual (PUM v1.9)
• OSI-405 Algorithm Theoretical Basis Document (ATBD v1.5)
• OSI-405 Scientific Validation Report (SVR v6.0)
• OSI-455 Product User Manual (PUM v1.0)
• OSI-455 Algorithm Theoretical Basis Document (ATBD v1.0)
• Implications of AMSR2 being replaced by AMSR3 on OSI SAF products
• Learn OSI SAF sea ice — training notebooks (EUMETSAT)