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Messages - Maplike

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Arctic sea ice / Re: The 2019 melting season
« on: June 26, 2019, 04:01:38 PM »
Area and extent are imperfect indicators, but at least can be directly and fairly reliably measured, unlike, say, volume. Area and extent numbers and maps from the various outfits that produce them (NOAA, uni Bremen, Jaxa ...) stay in general agreement while what volume maps exist are much more idiosyncratic.

My main idea is that we stop referring to changes in area and extent as "melting" or "freezing."  Volume measures, however imperfect, indicate melt or freeze.  Although long-term trends in area and extent measures are certainly correlated with melt/freeze, short term changes in the extent and area measures do not necessarily indicate overall melting or freezing situation. Extent can increase due to dispersion etc., even where there is overall melting. I think using the shorthand of "melt" or "freeze" with area and extent measures may be a source of confusion sometimes.

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Arctic sea ice / Re: The 2019 melting season
« on: June 25, 2019, 11:18:40 PM »
Hi folks,

Long time (well 3 or 4 years) lurker, throwing in my tuppence worth.

Although I graduated in Physics (focussing on Atmospheric Physics) 40 years ago, and have closely followed climate change since then, I'm no scientific expert, so I'm enormously grateful for all the info posted in the forum and I follow posts avidly on a daily basis.

My thoughts ...

1) We are all (scientists particularly) conditioned to analyse data and give them an elevated status, even when we know there are inaccuracies, caveats and relevant externalities. While sea ice extent is a great indicator of trend, it is only really useful at September minimum to show the trend - and even then conditions leading up to the annual minimum can change the final outcome appreciably.

2) Volume/thickness is key. Yet, as far as I can see, no-one seems to be able to measure it accurately (again, measurements published are useful to show trends, but otherwise, unreliable). The clear trend is that thickness is dropping, but by how much? It doesn't matter how much the extent is, but if the thickness is 1mm, it's going to all disappear in a few days, whatever has happened in similar conditions in previous years...

3) ... and I think that's what's missing from all the extent/area predictions I see on the forum. We can guess at thickness, we see the structure is changing (responsible, I believe, for ice fragility, leading to greater extent on the Atlantic side), but all of a sudden - and no-one knows when - we will see a collapse. My guess (and it's just that) is one autumn soon, the ice will break up and a lot of it flushed out of Fram/Barents. It would probably happen in the late summer when thickness is lowest, and might happen too late for all the ice to be flushed out, leading to a winter re-freeze over the whole of the Arctic, only for the job to be completed the following year.

What's clear to me is the structure of the Arctic sea ice is changing. It seems to be becoming more fragile. This will probably lead to greater extent (possibly area) before over a single year or maybe two it will all go - and we'll all be surprised as the data didn't warn us. Because nature is like that - earthquakes, lightning strikes, volcanoes, atomic quantum levels - the pressure builds, nature tries desperately to maintain the equilibrium, then it suddenly snaps, moves to a different equilibrium state and then desperately tries to maintain that.

As I say, just a few thoughts, and thanks again to all contributors to this forum. It's riveting.

S.

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Arctic sea ice / Re: The 2019 melting season
« on: June 18, 2019, 11:28:20 PM »
SMOS_beige_pixels.png]a record low dry ice area[/url] for 16 June.

Wow.   Hardly a dry ice in the house.       ;)

(Thanks for the link and explanation to SMOS)

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Arctic sea ice / Re: The 2019 melting season
« on: April 27, 2019, 03:42:23 PM »
According to the NSIDC chart, sea ice extent has been recovering, albeit minutely, in the past couple of days. How does this gel with the weather discussion here? Does it mean anything? Should we expect to see a rapid drop in the next few days?
...
Welcome Maplike to the ASIF (Arctic Sea Ice Forum)!
When the Arctic weather appears to be 'bad' and extent doesn't drop, some interpret this to mean the ice is breaking up and spreading, allowing SIA (sea ice area) to decline while maintaining SIE (sea ice extent).  [For frequently used abbreviations, see Glossary.]

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Arctic sea ice / Re: The 2019 melting season
« on: April 27, 2019, 11:14:15 AM »
According to the NSIDC chart, sea ice extent has been recovering, albeit minutely, in the past couple of days. How does this gel with the weather discussion here? Does it mean anything? Should we expect to see a rapid drop in the next few days?
There are often discussions on what might be future extreme weather events, e.g. this one due to start building up this weekend and maximising next week.

However, in the last few days conditions have not been that good for sea ice loss and this shows up in the data. i.e. sea ice extent today depends on what happened before and what is happening now, not what might happen in the future.

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