wmo-im
Add new sea ice variable: Sea-ice stage of development
Introduction
The stage of development of sea ice is related to the age and thickness of the ice, defined in terms of classes. It is primarily relevant to ice operations such as marine transportation, but is also useful in meteorological and climatological studies.
Amendment details
| notation | name | definition |
|---|---|---|
| TBD | Sea-ice stage of development | The Stage of Development of sea ice is defined as classes of sea ice related to age and ice thickness. The classes as defined by ice thickness in WMO-259 (Sea Ice Nomenclature) are: No stage of development, Nilas/ice rind (< 10 cm), Young ice (10-30 cm), Gray ice (10-15 cm), Gray-white ice (15-30 cm), First-year ice (30-200 cm), Thin first-year ice (30-70 cm), Thin first-year ice, first stage (30-50 cm), Thin first-year ice, second stage (50-7- cm), Medium first-year ice (70-120 cm), Thick first-year ice (> 120 cm), Old ice, Second-year ice, Multi-year ice, Ice of land origin, Undetermined or unknown. The last four classes are not directly related to thickness. |
Requestor(s)
Group: Global Cryosphere Watch (GCW). POCs:
Jeff Key ([email protected]), University of Wisconsin Petra Heil, University of Tasmania and Australian Antarctic Division, ([email protected]) Rodica Nitu, WMO, ([email protected])
Stakeholder(s)
National and international ice services as well as the scientific community.
Applications or Systems
- [x] OSCAR/Surface
- [x] OSCAR/requirements
- [ ] GAWSIS
- [ ] Radar/DB
- [ ] OceanOPS
- [ ] WHOS
- [ ] WDQMS
- [ ] GBON Compliance Monitor
- [ ] Other
Expected impact of change
LOW
Consultations
Stage of Development is defined in WMO Sea Ice Nomenclature (WMO No. 259, volume 1 – Terminology and Codes, Volume II – Illustrated Glossary and III – International System of Sea-Ice Symbols), March 2014. (https://library.wmo.int/records/item/41953-wmo-sea-ice-nomenclature)
Statement of Guidance for Cryosphere Applications (draft; https://docs.google.com/document/d/1Zl34oVvWNMO8VXBgDFpo08CK4bFDL6cU62flGCoz8yM/edit?usp=sharing)
Sea ice experts in and outside of the Global Cryosphere Watch were consulted on the importance of this variable.
Data exchange
No response
Comments
No response
https://github.com/wmo-im/tt-wigosmd/wiki/Meeting.2025.04.17 notes: Jeff introduced this proposal; he noted that is categorical and it is used a lot; Rosie Bisset will work on this
There are still 3 basic parameters for sea ice applications - CT, SoD, form of floating ice - full stop, with all others including SIT on further places, so that a simple change of SoD(s) to either single SIT value or SIT interval would not smoothly work as several physical sea-ice parameters are described by SoD including potential SIT interval, snow height interval, strength, viscosity. I would say, discussion on SoD during the recent years goes in spiral.
Code table 1-01-03.csv ObservedVariableOcean Observed variable - measurand (ocean)
with path: Ocean/Cryosphere/Sea ice
this is similar to issue #592, because the categories are part of the definition. Do we also want to create a sub-register with these categories instead?
Additional feedback was received from sea ice experts in the GCW expert network via email correspondence. The general consensus was that SoD is a complex categorical variable, widely used within the sea ice community, that can be classified not only by age and thickness, but also by other physical parameters. To reflect this feedback, the definition has been rephrased slightly and the class definitions have been expanded. Additionally, in response to feedback received from Anna and the Task Team on WIGOS Metadata, a sub-register has been added, including definitions for each of the classes of SoD, as defined by the Sea Ice Nomenclature (WMO No. 259, volume 1 – Terminology and Codes, Volume II – Illustrated Glossary and III – International System of Sea-Ice Symbols), March 2014. https://library.wmo.int/records/item/41953-wmo-sea-ice-nomenclature). The comments received via email but not otherwise added in this comment section, are included here for completeness.
Petra H. (email correspondence): Not a variable, so should not be created. Issue: Legacy and referred to in WMO nomenclature but creating as a variable in OSCAR is the wrong pathway. OSCAR = Observing Systems Capability Analysis and Review tool -> Stage of development is a derived variable. and OSCAR is not equal WMO nomenclature.
Vasily S. (email correspondence): sea-ice stage of development is a variable both for NWP and real-time monitoring and the climate monitoring described by 'classes', is fully similar to the 'cloud type' variable (https://space.oscar.wmo.int/variables/view/cloud_type), hence, having (or not having) 'SoD' in OSCAR is same as having (or not having) the 'cloud type' variable. SoD is a directly, routinely observed variable at the stations, ships, aircraft. Metric will be class.
Stefan K. (comment on Github parent issue): Stage-of-development: Difficult, this seems to be a categorical quantity, difficult to measure quantitatively, being potentially closely linked to the ECV quantity sea ice age.
Anna: this is similar to issue #592, because the categories are part of the definition. Do we also want to create a sub-register with these categories instead?
Thomas L. (email correspondence): This is clearly used in part of the community. It looks like the intersection of sea-ice age (categories) and thickness (ranges) but it does not mean that it is always derived as such (expert knowledge on ships, SAR-based retrievals,...).
[..]
Petra H. (email correspondence): Not a variable, so should not be created. Issue: Legacy and referred to in WMO nomenclature but creating as a variable in OSCAR is the wrong pathway. OSCAR = Observing Systems Capability Analysis and Review tool -> Stage of development is a derived variable. and OSCAR is not equal WMO nomenclature. [..] IMHO, even a variable derived from an observation needs proper terminology and definition. So, if it relies on observations and there is a request to include it from the community, it can be considered for the WIGOS vocabulary. Whether it is used in OSCAR is perhaps a different question. If it is considered an 'observed quantity' by the experts, it can be included.
That a good explanation and clarification, @joergklausen. It is observed, just not measured with a meter stick or a voltage differential, etc.
https://github.com/wmo-im/tt-wigosmd/wiki/Meeting.2025.06.12 notes:
@jeffrkey review comments and finalize proposal as needed
Similar to issue #593, the sub-register has been removed, following the decision made during the last TT-WIGOSMD: https://github.com/wmo-im/wmds/issues/593#issuecomment-2966732670
I updated the reference to the wmo publication slightly in the definition.