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Author Topic: On the importance of conserving mass in sea ice models  (Read 2669 times)

snowhare

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On the importance of conserving mass in sea ice models
« on: May 12, 2013, 04:53:35 AM »
I spotted http://arxiv.org/abs/1305.0629 on arXiv today. It discusses a problem with current models where they don't conserve mass when modelling decaying sea ice. It suggests this may be a reason that current models appear to be vastly underestimating melting.

ChrisReynolds

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Re: On the importance of conserving mass in sea ice models
« Reply #1 on: May 12, 2013, 08:15:25 AM »
Thanks,

My immediate thought on reading the abstract was whether this could explain the recent spring melt anomaly in PIOMAS. The reverse seems to be the case.

PIOMAS uses the basic formulation of Hibler, which is what this paper is talking about. However it seems to me that by assimilating sea ice concentration data (observed) that PIOMAS may be overcoming the problem of free running non-assimilating models (GCMs). This could be a major reason why PIOMAS is showing a steeper volume decline. Although there are other reasons.

The issue for me at present is understanding why around the summer equinox the PIOMAS spring volume decline stops and volume anomalies then rise and plateau, precisely when the ice edge has retreated to within the Arctic Ocean and concentration assimilation would be expected to have maximum effect.

Should the spring volume anomaly continue into the summer? If so that would imply that summer minimum volume would be lower than PIOMAS shows.

I need to let my sub-conscious work on this and re-read two sections later this morning.

Richard Rathbone

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Re: On the importance of conserving mass in sea ice models
« Reply #2 on: May 12, 2013, 03:21:01 PM »
Its going to depend just how PIOMAS assimilates, but it will tend to have the same problem with not melting enough that the GCMs have. It just not nearly as bad because its getting corrected from observations while the GCMs aren't.

Its a horrible flaw in the models. Essentially the climate has already moved into a state where they are only valid for parts of the earth where the polar conditions have negligible affect on the climate.