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Messages - jliukas

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1
Arctic sea ice / Re: The 2019 melting season
« on: July 27, 2019, 10:09:53 AM »
I have just returned from Croatia. Thanks to everyone for the condolences. In coming days, I'll try and get things in order here on the Forum.

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Arctic sea ice / Re: The 2019 melting season
« on: July 24, 2019, 06:05:53 PM »
Re: the icebreaker.
According to this article the ship had to return due to a leakage in the propellerhouse. The thicknes of the ice was not a problem. The icebreaker was built in Italy and was one year late due to construction problems, according the article. https://www.nrk.no/troms/forskningsskipet-_kronprins-haakon_-skadet-etter-mote-med-is-1.14636312

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Arctic sea ice / Re: The 2019 melting season
« on: July 07, 2019, 02:08:22 AM »
The ice looks like shit.


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Arctic sea ice / Re: The 2018 melting season
« on: September 01, 2018, 01:19:12 AM »
It's that time of year again, when we see that extent hasn't dropped as low as we feel it ought to have, and so we try to change the definition...

I think instead of 15% concentration Extent we should focus on assessing 50% concentration Extent. 15% takes a lot of areas that are basically 85% ice- free into account.

[... snip ... Discussion of posts where Ned W compares the standard extent data to what it would look like with a 30% threshold instead of 15% ...]

further, while it is great that you calculated that, perhaps you'd post the math behind it for verification and then nobody ever said that it must be 30%, perhaps the critical percentage is not 30% but another threshold. to follow this up it would take a few runs with different threshold to compare and the numbers to verify, after all, where are 30% numbers available, i did not find them which is why i was not able to do my own calculations?

[...] if we have a huge area  of 50% ice and 50% water no-one can tell that the result do not differ by at least the 35% that are usually counted and now are not, after al 35% is about a third, hence cannot be insignificant to my understanding

Personally, I think basic logic dictates that if an area is more water than ice, then it should be considered water. 15% as an arbitrary threshold is bizarre. If you look at my map prediction for Sep 1, a 50% threshold will be almost exactly as I predicted.

This comes up every year.  15% is what the community uses, all of the data (except older DMI) are based on it.  If we start making predictions about a 30 or 40 or 50% threshold, all it does is ensure that it will be prohibitively difficult to compare them to anything else, quantitively.

If this year's "50%-extent" is X million km2 ... Is that low, high, or average?  Nobody will know!  Because for every previous year, we have "15%-extent" data.

However ... As noted above, I did go back and reprocess all the NSIDC concentration maps to calculate a "30%-extent", and posted the results in the other thread here:

https://forum.arctic-sea-ice.net/index.php/topic,2223.msg164660.html#msg164660

On the next page following that one there's a post by me with a csv file with the results.

Magnamentis wants that redone for other thresholds, and wants me to post "the math" for verification purposes.  The "math" involved is merely (a) reprojecting all the ice concentration maps into an equal-area projection, and then (b) counting up the number of grid cells that exceed whatever threshold you want.  (A further complication is the "pole hole" whose size changes...) If there's a lot of interest I'd be willing to rerun the processor for different thresholds.

The thing is, though, so far at least it doesn't have any non-trivial effect on the long-term trend in extent.  As Neven predicted...   So the payoff for doing it is pretty small.


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Arctic sea ice / Re: 2018 sea ice area and extent data
« on: August 17, 2018, 06:44:57 AM »

I'm happy to have this thread polluted with calls for action. 

Please don't.  This is "2018 sea ice area and extent data."  There are other places in the forum for such topics.  Please don't disrespect the community here.

6
Arctic sea ice / Re: The 2018 melting season
« on: August 12, 2018, 05:23:33 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-08-11...

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Arctic sea ice / Re: Latest PIOMAS update (July mid-monthly update)
« on: July 19, 2018, 11:47:05 AM »
Here are several regional charts based on the data from Wipneus. This time I am focusing on this year's laggards - Kara, Beaufort and the ESS, in addition to my usual chart summing up all the regions typically participating in the September volume minimum.
As can be seen, Kara has done some catching up, Beaufort and ESS are still lagging, and the "Inner+" is still keeping up with the leaders.

8
Arctic sea ice / Re: The 2018 melting season
« on: July 15, 2018, 11:03:36 PM »



Quote

The polar cell has in effect collapsed, and a Ferrell circulation is in effect with low level incoming winds feeding lows, and their upper level outflows feeding high pressure systems covering the central north Pacific and Atlantic Oceans.

So, we have low pressure above the Arctic and a high pressure system in the Atlantic and the central north Pacific? We do have those every summer. What is the big deal? Attached is the average MSLP for 1979-2015 July.
I would call 2018 a "substantial departure" from ^. The ATL Hadley is now displaced extremely far N.

I would also ask that people use common sense re: Hudson Bay. Look at satellites. The ice is clearly still there. It is melting. But arguing over output from a model when satellites clearly show REALITY also shows how many here seem to prefer CPUs vs. common sense. This should not be an argument that takes up multiple pages in multiple threads.

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Arctic sea ice / Re: The 2018 melting season
« on: July 15, 2018, 09:32:36 PM »
I think the recent heat in this forum is the result that it was one of the first places where people come together to discover the possibility that the Arctic Ocean could become ice free very soon. Then, when the weather and fluctuations have deferred that ultimate but possible outcome from realising, people have become disappointed as too little, or too slowly things are happening. Rest assured, when that sad day sooner or later comes, there is little to nothing to celebrate, despite shortened shipping lanes to Asia. In the mean time, let's keep our forum civilised and avoid accusations or conspiracy claims.  :o

10
Arctic sea ice / Re: The 2018 melting season
« on: May 28, 2018, 12:38:10 AM »
The AMOC is not simple and the reports on it can be quite confusing because there are different measures of AMOC activity. Moreover, one part of the AMOC can be more active than another part.

There are peer reviewed reports of a general long-term slow down of the AMOC. I take no issue with those reports. The AMOC was relatively quite active between 1988 and 1995 when the Arctic oscillation was strongly positive. The far north Atlantic and the Arctic was very stormy in that period and cold fresh water in the Beaufort gyre was flushed and replaced with warm Atlantic water. After 1995 there was a general slow down in the AMOC as high pressure tended to dominate over the Arctic ocean. There was a severe slow down in the AMOC in 2010. It lead to a build up of tropical Atlantic heat, a bad hurricane season and a slowing of the Gulf Stream that caused flooding at Norfolk Va and other sea level sensitive areas on the U.S. east coast. After that, by some measures, the AMOC picked up.

My statements about the AMOC this late winter and spring are based on Mercator ocean profiles, the persistent Greenland vortex at 500mb and the persistent storms that the vortex has been producing. What many readers don't seem to appreciate is that the warm SST pattern, off of the southeastern and mid-Atlantic states of the U.S. , is a feature that is quite deep. It's not just warm surface waters. The north wall of the Gulf stream goes down over 1000m.




Likewise, the cold anomaly in the subpolar gyre reflects the effects of continued storms that have maintained deep water formation in the Labrador sea into late spring.





The cooling of the tropical Atlantic over the past month is the result of stronger than normal trade winds that moved tropical heat into the subtropics and temperate regions.



To put it simply, the weather patterns this spring are normal patterns that have been intensified by an excess of heat in the northern hemisphere's oceans. The intensification of northward heat transport by the atmosphere is reflected downwards into the ocean. The end result is that the European - Atlantic side of the Arctic is heating up very rapidly this spring. I won't repeat showing the Levitus et all heat content map here, but it shows anomalous heat entering the Arctic from the Atlantic - not good for sea ice.


11
Arctic sea ice / Re: 2018 sea ice area and extent data
« on: May 28, 2018, 12:06:15 AM »
There is  a thread called northern hemisphere snow cover.
This thread is about 2018 arctic sea ice extent and area data.

So - geroff.

12
Arctic sea ice / Re: The 2018 melting season
« on: May 23, 2018, 06:36:09 PM »
Here is a first pass at ice classification based on its provenance (origin history) implied by the 233 day time series a couple posts back. Modulo subsequent translocation and plastic deformation, this provides a rough prediction of what ice will remain where in mid-September.

The two Ascat-based posterization slides give a more nuanced version under the assumptions that Ascat roughness ~ ice age ~ ice thickness ~ location coldness ~ susceptibility to melt. That has worked out fairly well for recent years, though the Great Arctic Cyclone of early August 2012 is missing from the Ascat archive available.

Jaxa images come from a very different instrument but its posterization-prediction is not dissimilar from Ascat. It has more potential for melt pond tracking (pinkish regions) but weather artifacts bring in considerable ambiguity.

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