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OffTheGrid

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Re: HYCOM
« Reply #150 on: June 14, 2021, 12:45:01 AM »
<Vulcanism spam removed. O>
« Last Edit: June 14, 2021, 02:05:21 AM by oren »

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Re: HYCOM
« Reply #151 on: June 14, 2021, 03:28:08 AM »
I suppose if it melts this quickly none of it really matters...


At the end of 2020 melt season HYCOM shows no ice thicker than 2.4 meters. While I am not certain on the exact numbers ice can not thicken much beyond about 2 meters in a single season. The 2 m ice does not thicken to 4 m in a single season more like 2.5 m. Again I don't know the exact numbers. Ice thicker than that is formed by pressure ridging. When HYCOM shows 4 m ice I imagine it is either ridges or chunks of ice pushed together. When the melt season relieves that pressure I picture most of the thickness of those pressure ridges collapsing and some of the stacked rubble as well. As HYCOM is primarily a navigational aid and not a climate tool when it shows 4 m ice in an area it is most likely indicating that there is ridging up to 4 m in an area and not that the ice is 4 m thick throughout. I think this is a probable explanation for your longstanding concern that HYCOM shows thick ice melting too quickly. If I am right in this scenario some nearby open ocean and a shift in wind would tend to reduce maximum ice thickness rather quickly.

uniquorn

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Re: HYCOM
« Reply #152 on: June 14, 2021, 02:39:03 PM »
Thanks, so possibly max thickness per grid, not average thickness. That could explain the apparent rapid melt and requires more careful interpretation. It might also mean they are modelling thin ice as even thinner, though maybe thin ice has less ridging so avg would be closer to max.

Background info regarding thickening over 2m, this buoy in the Beaufort thickened ice and snow from 2.1m to 2.46m (36cm) but looking at just the bottom sounder shows an increase of only 13cm with bottom melt continuing well into January.

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Re: HYCOM
« Reply #153 on: Today at 03:12:51 AM »
Yes it is a navigation guide so it indicates thickest ice. But some Individual thicker floes have been identified by buoys and in person measurement. I speculate it is as an 95% confidence limit of a distribution. As in 95% of the thicknesses are below this level. It may be simpler than that it may just be the maximum thickness the model predicts I do not know.


I do not think it is appropriate to include the model forecast with the model reanalysis. Reliability wise the forecast has all the problems of any weather forecast added to it. My estimation is that as a predictive product it is not all that great. In my antidotal experience it tends to show ice melting out much faster than the reanalysis product shows. Last year I made some assertions about melting based on the product. It seemed like every time melting took longer than it predicted.


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Re: HYCOM
« Reply #154 on: Today at 03:27:37 AM »
Background info regarding thickening over 2m, this buoy in the Beaufort thickened ice and snow from 2.1m to 2.46m (36cm) but looking at just the bottom sounder shows an increase of only 13cm with bottom melt continuing well into January.
I have looked at data from the buoy threads from time to time but it is not something I have spent much time on. Are you saying the bottom sounder is more reliable and it only increases 13 cm? Or are you implying something else?