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willaguiar / Panan_HT_ASC

Evaluation of Cross-slope-heat-transport and ASC speed in different resolutions of the Panantarctic model
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Differences in CSHT between panan01 and OM2-01 (+validation) #1

Open willaguiar opened 1 year ago

willaguiar commented 1 year ago

Here we can compare how the CSHT changes between Panan01 and OM2-01. Those two simulations have the same bathymetry and surface forcing, and therefore differences are likely due to ocean model dynamics

willaguiar commented 1 year ago

Here is a quick comparison of the Cross-slope-heat-transport between OM2-RYF run, and Panan-01.

[a] Annual Mean Total CSHT

The top curve has the binned CSHT+zonal convergence. Model's curves are fairly similar, with panan-01 having 8 TW less of poleward heat transport than OM2. HTplusZC

When we check the CSHT (no ZC) and the Zonal convergence separately (all cumsum), we can see that the curves do differ, but that difference is compensated by the Zonal convergence (which seems to have mostly negative values, and oscillate less on Panan-01). CSHT_no_ZC ZC

Nevertheless, in terms of validation of panan-01, the total CSHT value and CSHT+ZC curve seem reasonable.

[b] Seasonal Cycle

The maximum Southward heat transport present in OM2 in February, is weaker in panan-01. This weaker summer heat transport on panan-01 likely explains the 8TW difference in annual mean transport seen in [a]. Seasonal Cycle

Because this a summer difference, I thought it would be worth to look at sea ice differences (e.g., could larger sea ice cover in panan-01 be weakening surface summer Ekman transport?). However, it seems that close to the coast and to the 1km isobath, SIC is lower on Panan-01 than OM2 in DJF, so perhaps sea ice cover cannot explain this difference.. Unless the big panan DJF increase in sea ice cover offshore of Weddell Sea is altering atm-ocean heat fluxes and diminishing the overall surface HT to Antarctica.

Code used here

willaguiar commented 1 year ago

Some additional thoughts I thought are important to register:
I - Why is the zonal convergence so different between the simulations? on OM2 the zonal convergence seem to oscillate more along the contour than on panan-01. Does that mean that ASC representation differs substantially between simulations (Maybe less crossing back-and-forth of the 1km isobath on panan-01)?

II- Although the total CSHT calculated for the simulations seem similar, they differ by 8 TW, or ~20%. And that should be purely due to different ocean/sea-ice models, since both simulations have same forcing and bathymetry.

III - When we see the CSHT values for the IAF simulation of ACCESS-OM2-01, we see that they oscillate up to -120 TW. The years that are used to force the RYF simulations are just years with particularly low oscillations in the CSHT (maximum CSHT of ~60 TW, and minimum 0 TW on 1991). We should keep that in mind when analyzing our results.