Deprecate or expand Sea-ice characteristics (code 404) and Sea-ice type (code 407) with additional variables

[jeffrkey]

Introduction

This request is to deprecate or expand Sea-ice characteristics (code 404) and Sea-ice type (code 407) with additional variables that provide more detailed and useful information on sea-ice characteristics. The current variable "Sea-ice characteristics" is defined by properties such as albedo, temperature, and melt ponds, but the measuring unit (%) cannot provide any information on those properties.

The situation is similar for the variable "Sea-ice type", the definition of which includes characteristics such as age and roughness. The measuring unit is a class. While a categorical variable could represent various age, roughness, and density classes, those properties are better represented with continuous values rather than discrete classes.

The codes, names, and definitions of the existing variables are given in the "Amendment details" section below. It is proposed to replace those variables with, at a minimum, the individual properties that are in their definitions. Another option is to retain the two existing variables and add new variables. The sea ice variables that the requestors deem as important include, but are not limited to:

Surface albedo of sea-ice, which may or may not be snow-covered
Melt pond fraction
Stage of development
Age
Floe size

Other variables of interest are:

Leads (fractures) and polynya characteristics (width, orientation)
Ridged ice fraction
Surface state (dry, melting, etc.)

The existing (not proposed) variables are:

notation	name	definition
404	Sea-ice characteristics	Sea-ice surface characteristics (albedo, meltpond, dust, snow properties, temperature)
407	Sea-ice type	Variable convolving several factors (age, roughness, density, etc.). Accuracy expressed as number of classes. Actually [ classes^-1 ] is used, so that smaller figure corresponds to better performance as usual.

Amendment details

(update 19 March by amilan17)

• Retire
  • Sea-ice characteristics
  • Sea-ice type
• Add
  • Surface albedo of sea-ice, which may or may not be snow-covered
  • Melt pond fraction
  • Stage of development
  • Age
  • Floe size

Requestor(s)

Group: Global Cryosphere Watch (GCW)
POCs:

Jeff Key (jeff.key@wisc.edu), University of Wisconsin
Petra Heil, University of Tasmania and Australian Antarctic Division, petra.heil@utas.edu.au
Rodica Nitu, WMO, rnitu@wmo.int

Stakeholder(s)

National and international ice services, e.g., US National Ice Center, North American Ice Service, Norwegian Ice Service; scientific community for remote sensing validation, meteorological/climatological and modeling applications

Applications or Systems

• OSCAR/Surface
• OSCAR/requirements
• Radar/DB
• OceanOPS
• WHOS
• WDQMS
• GBON Compliance Monitor
• Other

Expected impact of change

MEDIUM

Consultations

GCW Sea Ice Best Practices team and other GCW sea ice experts; GCW Cryosphere and Polar Observations (CRYORA) team
Belén Martín Míguez, Ocean Earth System Category (ESAC)
Statement of Guidance for Cryosphere Applications, Sea Ice Pilot Study (draft; https://drive.google.com/file/d/1rDshrNSQSTYAU9FihlrjIl1CJ402GvSU/view?usp=drive_link)

Comments

No response

[IARC2000]

The logical decision is to depreciate both, Sea-ice characteristics (code 404) and Sea-ice type (code 407). These are not measurable, and in general do not sure the same units.
Instead primary sea-ice variables superceeding sea-ice characteristics will be:

• "Sea-ice temperature",
• "Sea-ice meltpond",
  Plus snow variables, which should not be sitting under sea ice but under snow.
  Plus "surface albedo", "meltpond areal coverage", "meltpond long-axis", meltpond short-axis",
  I am not convinced about dust... Suggest to have it dealt with as part of surface albedo measurements, but if needed "(surface) impurities" could be included with a unit of ppm.

My recommendation is the depreciate "sea-ice type" completely. If there are any sea-ice, snow or other variables that need to be included then these should be added as separate variables.

In conclusion, amalgamated variables are not measurands and cannot be replicated, including in numerical models.

[mohntorte]

Stefan Kern:
I very much support deprecation of the two variables "sea ice type" and "sea ice characteristics" for the sake of enhancing the granularity and our means to better quantify the state of the sea ice cover by introducing new, better to observe quanities.

I note that sea ice albedo has been already an ECV quantity of the sea ice ECV in the last GCOS-IP from October 2022.

I note further that sea ice age has been already an ECV quantitiy of the sea ice ECV in the last GCOS-IP from October 2022 and is the target of a recently accepted new ESA project to generate / improve existing ECV quantity climate data products.

Whether or not "melt-pond fraction" should make it into a new variable needs to be discussed. On the one hand, it makes a lot of sense because there is a growing set of data products of this quantity and it is a very useful quantity to enhance summer-time sea ice concentration data sets known to exhibit considerable biases during summer. On the other hand, we should be prepared for comments from the community regarding that it might be sufficient to know the surface albedo because potentially the most important influence of melt ponds in the Climate System is the influence on albedo and net surface shortwave radiation balance.

I suggest to try to better define the alternative quantities in terms of the units and which sub-quantities would be required (and are measurable); I give a go ...

Leads and fractures: Number and/or frequency per area [1/m²] / width [m] / length [m] / orientation [unit = ?]

Polynyas and openings: width [m] / area [m²] / frequency of occurrence ?

Ridges: ridged ice fraction [percent] / ridge height [m] / orientation [unit = ?]; it might make sense to take into account what can be estimated / observed currently from satellite data: the sea ice topography (preferably underneath a satellite sensor overpath) and the pure existence of ridges.

Floe size: floe area [m²], perimeter [m], aspect ratio ?, number of floes per area [1 /m²], floe size distribution in known area [unit ?]

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.

Surface-state: Difficult to measure as well: wet / dry ... level / ridged ... snow-covered / bare ... more, but how to measure quantitatively? Seems to be a categorical parameter as well.

I think these last two variables kind of complement each other.

[TomLav]

I support deprecation of the two variables "sea ice type" and "sea ice characteristics" and replacing them with more "physical / measurable" variables. I will follow the proposal for new variables with interest, but have nothing to contribute right now.

[amilan17]

https://github.com/wmo-im/tt-wigosmd/wiki/Meeting.2025.02.20 notes:
Anne will "own" the issue

[PaoloLeoniIT]

This information could be useful for us.
https://nsidc.org/learn/parts-cryosphere/sea-ice/science-sea-ice#:~:text=The%20World%20Meteorological%20Organization%20(WMO,3.9%20to%2011.8%20inches)%20thick.

(I haven't yet found the main WMO source cited on this webpage. I will update you asap)

This source could support our task
https://gcos.wmo.int/site/global-climate-observing-system-gcos/essential-climate-variables/sea-ice

[kamauanne-cpu]

Dear Paolo, Thank you for the useful information you sent. I will open the links too search for whatever is supportive. Kind regards, Anne.

…

On Thu, Feb 20, 2025 at 5:48 PM Paolo Leoni ***@***.***> wrote: This information could be useful for us. https://nsidc.org/learn/parts-cryosphere/sea-ice/science-sea-ice#:~:text=The%20World%20Meteorological%20Organization%20(WMO,3.9%20to%2011.8%20inches)%20thick . (I haven't yet found the main WMO source cited on this webpage. I will update you asap) This source could support our task https://gcos.wmo.int/site/global-climate-observing-system-gcos/essential-climate-variables/sea-ice — Reply to this email directly, view it on GitHub <#579 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/BK3CDEWSWULG5GYZSCUZCWD2QXTLNAVCNFSM6AAAAABXPKLUJSVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDMNZRG4ZDAMZTHE> . You are receiving this because you were assigned.Message ID: ***@***.***> [image: PaoloLeoniIT]*PaoloLeoniIT* left a comment (wmo-im/wmds#579) <#579 (comment)> This information could be useful for us. https://nsidc.org/learn/parts-cryosphere/sea-ice/science-sea-ice#:~:text=The%20World%20Meteorological%20Organization%20(WMO,3.9%20to%2011.8%20inches)%20thick . (I haven't yet found the main WMO source cited on this webpage. I will update you asap) This source could support our task https://gcos.wmo.int/site/global-climate-observing-system-gcos/essential-climate-variables/sea-ice — Reply to this email directly, view it on GitHub <#579 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/BK3CDEWSWULG5GYZSCUZCWD2QXTLNAVCNFSM6AAAAABXPKLUJSVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDMNZRG4ZDAMZTHE> . You are receiving this because you were assigned.Message ID: ***@***.***>

[amilan17]

Dear @jeffrkey @IARC2000 @mohntorte, As primary contributors to this issue and others, we kindly request that your GitHub profile includes your full name and affiliation. If you don't want to do this, please email me the information instead (amilan at wmo.int). Thank you.

[IARC2000]

This information could be useful for us. https://nsidc.org/learn/parts-cryosphere/sea-ice/science-sea-ice#:~:text=The%20World%20Meteorological%20Organization%20(WMO,3.9%20to%2011.8%20inches)%20thick.

(I haven't yet found the main WMO source cited on this webpage. I will update you asap)

This source could support our task https://gcos.wmo.int/site/global-climate-observing-system-gcos/essential-climate-variables/sea-ice

Dear Paolo.
Thank you for exploring this request. - The NSIDC info is very generic on the topic of sea ice, and I suspect not written with the intention to provide exact definitions. I see it as "101 to sea ice".

Best wishes, Petra

[amilan17]

@jeffrkey The scope of this proposal is very broad. To help keep the proposals clean and straightforward, I recommend creating a sub-issue for each newly proposed variable. Also, please note that each code should have a name and a definition. It is also helpful to cite WMO publications or other sources for these definitions.

[kamauanne-cpu]

I appreciate the comprehensive input of the cryosphere experts into the sea-ice characteristics (code 404) and the sea-ice type (code 407).
Thank you all.