AABW transport

[PaulSpence]

https://github.com/COSIMA/cosima-recipes/blob/main/DocumentedExamples/Zonally_Averaged_Global_Meridional_Overturning_Circulation.ipynb

[xiliangdiao]

The subpolar cell start to seperate into two parts from year 2050 and thereafter, I think maybe we can use the WMT to explain this.

[xiliangdiao]

[xiliangdiao]

Now I have some interesting results for the MOC part, too. My basic idea is that we can use the 1000m depth line to seperate the DSW overflow part and the open ocean deep convection part. Actually, based on the results, these two part in the MOC will also seperate with each other in the climate change scenario at about year 2050 (see the figuresabove).

The shelf part shows a clear linear trend under calimte change scenario (maybe due to the salinity is the dominate factor), as the density decreases linearly, thus the DSW overflow induced MOC should also show a clear decreasing trend in both strength and density.

While the open-ocean deep convection part seems still can produce very dense water in the late stage (year 2090) of the climate change scenario (possibly due to the temperature is the dominate factor now). The open-ocean deep convection part is not that linear, and seems still have a instrinsic 40-50 years period oscillation pattern there (based on our previuos analyzation, but seems not that strong now). At the late stage, the AABW that denisity bigger than 37.25 seems all come from the open-ocean deep convection part, this no-linear pattern may then make the MOC trend more complex and harder harder to predict.

[PaulSpence]

Thanks for the plots. The MOC variability is pretty intense! A couple suggestions are:

i) Would be cool to look at annual mean time-series of the upper Deacon cell and AABW (bottom cell). Does the upper cell go from >25Sv in 2010 to ~15sv 2020 and >30Sv by 2030?

ii) Is there a control simulation (no climate change) that you can compare the variability to? If so, would be great to compare times-series of MOC transport

iii) when does the polynya kick happen (years)? The lower-cell seems to overall weaken ... except for increase in 2060.

iv) why does the upper-cell strengthen so much? Is the SAM wind response really strong to global warming?

v) I'm a little confused by your CDW labels in the transformation plots. CDW should be getting lighter right (e.g. -ve transformation)

vi) decompose the transformation into salt and heat components. Maybe plot spatial maps of them, overlayed with isopycnals so we can see what is happening where, and compare to the control simulation.

I think you are right that the watermass transformation is interesting. Do you have an age tracer in the model?

Thanks for sharing your work and being patient while I am at sea!

[xiliangdiao]

polynya kick happen (year)

[xiliangdiao]

The sig1 value here is smaller than Li qian et al (2023) and Morrison et al (2020) paper result

[xiliangdiao]

[xiliangdiao]

I have made two water age plots just in the bottom model cell (one inside the OODC period and one is not inside the OODC period).

For the Ross Sea shelf region, the DSW outflow from the Drygalski Trough, Joides Trough, and Glomar Challenger Trough seems good. While where the DSW outflow from the Weddell Shelf is hard to distinguish for me. Any suggestions for this plot? About how to show the DSW outflow better?

[PaulSpence]

can you show just the age in the bottom cell? or depth integrated for density>aabw threshold. see fig 1 here: https://www.science.org/doi/10.1126/sciadv.aav2516

[xiliangdiao]

My plots is the water age just in the model bottom cell! I choose them by using a small program already here.