Antarctica boundary in a global mesh

[brey]

In a global mesh context what is the best way to represent Antarctica? The ice boundary (L5 in full resolution GSHHS) fits best with the DEMs. I presume that whether you have an ice model on/off would make a difference. Any thoughts @josephzhang8 @WPringle ?

[josephzhang8]

Hi George: I checked my SMS files and I used L5 GHHS there. It's important to use RTopo2 to represent the bathymetry in Antarctica. I have not carefully tested the sensitivity to the boundary there. I did however test a simple ice shelf model (with atmos pressure acting as surrogate for ice shelf) using the data in RTopo/ice_base to represent the shelf height. The (short term) results seem to be close so I did not pursue further. That's a fascinating area to work in the future. Regards, ------------------------------- Joseph Zhang (804)684 7595 (office) SCHISM web: http://ccrm.vims.edu/schism/ From: George Breyiannis ***@***.***> Sent: Sunday, February 5, 2023 6:59 AM To: oceanmodeling/Management ***@***.***> Cc: Y. Joseph Zhang ***@***.***>; Mention ***@***.***> Subject: [Ocean Modeling Collaboration] Antarctica boundary in a global mesh (Discussion #13) [EXTERNAL to VIMS received message] In a global mesh context what is the best way to represent Antarctica? The ice boundary (L5 in full resolution GSHHS) fits best with the DEMs. I presume that whether you have an ice model on/off would make a difference. Any thoughts @josephzhang8<https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fjosephzhang8&data=05%7C01%7Cyjzhang%40vims.edu%7C3cd72f5d179e488730e808db0770568c%7C8cbcddd9588d4e3b9c1e2367dbdf1740%7C0%7C0%7C638111951314261032%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=ssFICYQYOPoQ7ziJmt%2FjpTCTZMTxbc29WOk22ah91Pw%3D&reserved=0> @WPringle<https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2FWPringle&data=05%7C01%7Cyjzhang%40vims.edu%7C3cd72f5d179e488730e808db0770568c%7C8cbcddd9588d4e3b9c1e2367dbdf1740%7C0%7C0%7C638111951314261032%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=Zo7N6%2B7cOvrutXNYHEQeY9rd8g5om8Z4d0GfC3w2FWc%3D&reserved=0> ? - Reply to this email directly, view it on GitHub<https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Forgs%2Foceanmodeling%2Fdiscussions%2F13&data=05%7C01%7Cyjzhang%40vims.edu%7C3cd72f5d179e488730e808db0770568c%7C8cbcddd9588d4e3b9c1e2367dbdf1740%7C0%7C0%7C638111951314417316%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=Duc%2Bq7rW2pgq%2Fjbg9Wcg53zVry6SZUNV4RlcbdoJwGA%3D&reserved=0>, or unsubscribe<https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fnotifications%2Funsubscribe-auth%2FAFBKNZYKTQJ7PALBBSN2DCDWV6IXNANCNFSM6AAAAAAURXMK2U&data=05%7C01%7Cyjzhang%40vims.edu%7C3cd72f5d179e488730e808db0770568c%7C8cbcddd9588d4e3b9c1e2367dbdf1740%7C0%7C0%7C638111951314417316%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=YcrKXN1rHVWHUEdq401vKIhEHjxaeQxlRpkxzPE2pps%3D&reserved=0>. You are receiving this because you were mentioned.Message ID: ***@***.******@***.***>>

[WPringle]

In a global mesh context what is the best way to represent Antarctica? The ice boundary (L5 in full resolution GSHHS) fits best with the DEMs. I presume that whether you have an ice model on/off would make a difference. Any thoughts @josephzhang8 @WPringle ?

Use the GSHHS_f_L6 grounding-line boundary, not the ice boundary. Then you need to use the DEM giving the difference between the ice surface and the bedrock to get the depths under the ice. So can't just use GEBCO. See Section 2.4 of:
Pringle, W. J., Wirasaet, D., Roberts, K. J., & Westerink, J. (2021). Global Storm Tide Modeling with ADCIRC v55: Unstructured Mesh Design and Performance. Geoscientific Model Development, 14(2), 1125–1145. https://doi.org/10.5194/gmd-14-1125-2021

[brey]

Which one of the files here should I use as the DEM?

[josephzhang8]

I used: RTopo-2.0.1_30sec_Antarctica_data.nc Regards, ------------------------------- Joseph Zhang (804)684 7595 (office) SCHISM web: http://ccrm.vims.edu/schism/ From: George Breyiannis ***@***.***> Sent: Saturday, February 11, 2023 12:53 PM To: oceanmodeling/Management ***@***.***> Cc: Y. Joseph Zhang ***@***.***>; Mention ***@***.***> Subject: Re: [oceanmodeling/Management] Antarctica boundary in a global mesh (Discussion #13) [EXTERNAL to VIMS received message] Which one of the files here<https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdoi.pangaea.de%2F10.1594%2FPANGAEA.856844%3Fformat%3Dhtml%23download&data=05%7C01%7Cyjzhang%40vims.edu%7C7b3788001efc45a4d67408db0c58c928%7C8cbcddd9588d4e3b9c1e2367dbdf1740%7C0%7C0%7C638117347696884694%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=8RBLtQyo48WaXDgYA4Xo3m0BMjosByTTmgYscfrWHfM%3D&reserved=0> should I use as the DEM? - Reply to this email directly, view it on GitHub<https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Forgs%2Foceanmodeling%2Fdiscussions%2F13%23discussioncomment-4944654&data=05%7C01%7Cyjzhang%40vims.edu%7C7b3788001efc45a4d67408db0c58c928%7C8cbcddd9588d4e3b9c1e2367dbdf1740%7C0%7C0%7C638117347696884694%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=xrSiBL2lHn0VjktSqROg%2FrGni4E%2BcBenX1xA0j9E4YU%3D&reserved=0>, or unsubscribe<https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fnotifications%2Funsubscribe-auth%2FAFBKNZ67MR7ZSYEMWRMPM6TWW7GW5ANCNFSM6AAAAAAURXMK2U&data=05%7C01%7Cyjzhang%40vims.edu%7C7b3788001efc45a4d67408db0c58c928%7C8cbcddd9588d4e3b9c1e2367dbdf1740%7C0%7C0%7C638117347696884694%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=X%2Bs0pIObYi7EzYH2mScQmKzgo2P3%2B45azEUv0n9hP5g%3D&reserved=0>. You are receiving this because you were mentioned.Message ID: ***@***.******@***.***>>

[brey]

In the RTopo-2.0.1_30sec_Antarctica_data.nc there are several variables:

<bound method DatasetAggregations.var of <xarray.Dataset>
Dimensions:              (londim: 43201, latdim: 4801)
Coordinates:
    lon                  (londim) float32 ...
    lat                  (latdim) float32 ...
Dimensions without coordinates: londim, latdim
Data variables:
    bedrock_topography   (latdim, londim) float32 ...
    ice_base_topography  (latdim, londim) float32 ...
    surface_elevation    (latdim, londim) float32 ...
Attributes:
    Title:        RTopo-2 global topography data set, Antarctic sector
    Author:       Janin Schaffer and Ralph Timmermann
    Institution:  Alfred Wegener Institute, Helmholtz Centre for Polar and Ma...
    Source:       Compilation of several original or gridded data sets
    References:   Schaffer, J., R. Timmermann, J.E. Arndt, S.S. Kristensen C....
    Version:      2.0
    Comment:      Use ncview -no_auto_overlay for a simple and efficient data...>

I assume that we use the bedrock_topography. True?

[WPringle]

@brey I use ice_base_topography minus bedrock_topography to get the depths under ice shelves. When ice_base_topography is zero/no ice then it will be bedrock_topography

[pmav99]

For the record, there is a newer dataset for under ice bathymetry: paper and data

They provide the water depth directly so you don't need to bother with multiple files. The relevant product is WATER_HEIGHT_ANTGG2022.tif

On average it gives larger depths for under-ice. Not sure if/how this translates to a measurable difference on a global model. If we find the time we should run a test to compare it with RTopo