Arctic sea-ice depth ~2x higher than previous configs

[kieranricardo]

Our current CM3 config has ~2x higher Arctic sea ice depth/volume (but same area) as previous configs and CM2 quarter degree (which roughly matched obs). Unsure if same issue is present in OM3 or is something coupling related.

[kieranricardo]

Same issue in OM3 (run /g/data/ol01/access-om3-output/access-om3-025/25km-iaf-test-for-AK-expt-7df5ef4c/datastore.json):

[MartinDix]

Maps of the ice thickness would be interesting. Is it in the same place in both models?

[kieranricardo]

@MartinDix here's an average over the 20th year for OM3 and CM3:

[MartinDix]

See also ACCESS-Community-Hub/access-om3-paper-1#21. Includes links to AK's scripts for polar plots.

[kieranricardo]

Here plots of 60N+ with a stereographic projection (year 4 ice thickness annual average):

[kieranricardo]

The stuck ice points don't show up well in the contours, here's the points (or more specifically triangles in the Delaunay with points) with > 20m average grid cell ice thickness:

[kieranricardo]

In year 40:

CM3 NH ice vol: 42.1773624811162
CM3 NH ice vol (< 20m): 42.08263095959721

OM3 NH ice vol: 42.57503908062145
OM3 NH ice vol (< 20m): 34.380561207942186

So while ice > 20m explains some (only ~30-40% - not all) of the OM3 excess ice volume (agrees with @anton-seaice 's plot here ACCESS-Community-Hub/access-om3-paper-1#20 (comment)), something else is happening in CM3. Maybe using where advection is inactive directly instead of using icethickness as a proxy will give more decisive results.

[kieranricardo]

Similar results using umask to look at only cells with active advection:

CM3 NH ice vol: 42.1773624811162
CM3 NH ice vol (advection active): 41.10585699280989

OM3 NH ice vol: 42.57503908062145
OM3 NH ice vol (advection active): 34.256747771964505

[ofa001]

Thanks @kieranricardo, I was about to go and look for stuck CM3 points you beat me to it. I think the difference is between CM3 v OM3 in the Arctic besides the stuck points is what i already mentioned the wind effect blowing the ice to strongly towards the Siberian coast, too much melting on the Canadian/Alaskan coast in summer the dynamic ice volume rate of change terms shows this, and the melt pond impact once the ice gets so thick that the majority of the ice in summer remains in category 5 'topographic ponds' only work in categories 1-4.

If you redo your (really nice) plots from year 4 for year 20 you would see the impact of these processes on the cumulative annual volume in OM3 v CM3 more clearly.

[access-hive-bot]

This issue has been mentioned on ACCESS Hive Community Forum. There might be relevant details there:

https://forum.access-hive.org.au/t/access-cm3-technical-meeting-minutes/5429/4