Spatial variability in ASC strength and cross-slope heat transport [Task 2]

[adele-morrison]

Can we find any relationship between the spatial variations in time mean ASC strength and cross slope heat transport? We could do this on very local scales, or group by regions (fresh, warm, dense). We could try using different measures of ASC strength (max speed, structure, position). We could also try different vertical integrations of cross-slope heat transport (e.g. depth integrated vs integrated over lower layers only or in certain density classes).

[willaguiar]

Update on this issue.

We have calculated interpolated the ASC along-slope speed into the classic contour of the cross-slope heat transport so we can do regional and poit-by-point correlations. Here is a summary of the results so far:

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Point by point spatial correlations between mean ASC speed along the contour and HT The idea here is to test if regions with stronger ASC have weaker heat transport. for this I ... ... calculated the mean ASC speed in each point of the contour ... calculated the mean HT in each point of the contour ( including the zonal convergence in the calculation) ... Correlated HT as f(long) and the ASC speed as f(long).

The correlation is pretty slow, except by a band of East Weddell Sea (Longitudes >-20W)

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Point by point spatial correlations between mean ASC and HT standard deviations The point here is to test if regions with strong ASC variability present strong variability in the Cross-slope-heat transport for this I ... ... calculated the standard deviation of ASC speed in each point of the contour ... calculated the standard deviation of HT in each point of the contour ( including the zonal convergence in the calculation) ... Correlated sd(HT) as f(long) and the sd(ASC) speed as f(long).

Results show that as ASC variability increases, HT variability also increases, but the correlation is still very small ( very big spread)

Conclusion. No consistent correlation can be seen spatially, exception is perhaps a small region in East Weddell sea.

[willaguiar]

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Point by point correlations between ASC and HT timeseries The idea is here is to identify which locations have a good correlation between variables for this I ... ... extracted the monthly Series of HT and ASC in each contour point ... Calculated the correlation between the series in each point plot on top is the mean binned ASC(blue) and HT(orange) for reference

here it seems that there is a high variability in the correlations along the contour, except by a region in East Weddell sea [20W to 50E] where correlations are consistently negative and close to -1. This seem to be the same region where the points are close to the regression curve in the top plot of this post.

more coming on east Wendell sea...

[willaguiar]

For East Weddell Sea Mean ASC speed and HT in this region seem to be negatively correlated (r=-0.82). With weak summer ASC leading to strong poleward heat transport. But heat transport seem to shift directions here, with strong ASC being related to strong northward heat transport.

This "good" correlation is present in this surface-intensified region of the ASC. SO it could mean a few things:

• Strong ASC surface variability is retained in the vertical mean of the ASC speed in this surface-intensified ASC region
• Low ice cover during summer enhances the poleward surface (Ekman) heat transport, in the same time where ASC is at its minimum. So this strong correlation could be just a synchronous variability of the seasonal cycle

biases: all this analysis is based on monthly mean ASC speed.

For future analysis: Separate analysis into density layers, use daily output, filter seasonal cycle (Ekman transport is dominating the heat transport here?)

Suggestions are more than welcome! code here