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Author Topic: Latest PIOMAS update (November mid monthly update)  (Read 632868 times)

slow wing

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Re: Latest PIOMAS update (mid July update)
« Reply #2000 on: July 18, 2017, 03:26:40 PM »
Thanks Wipneus, always interesting!

So the current ice thickness contours are fairly simple in shape: nearly triangular at 1.75m, 1.50m, 1.25m and weighted to the Atlantic side; and with the Pacific side filled out to form more of a trapezoid at the 1.00m contour.

At this time of year, would we expect it to melt out to around the 1.25m triangular contour?

If so then the Pacific side is going to look very blue come September, as in the past years 2007, 2012 and 2016.

Just eye-balling it, call the 1.25m triangle as having a 2600 km base and 2000 km height, so half-base-times-height would be an end-of-melt-season extent of roughly 2.6 million square kilometers. That is somewhere close to the 2012 record of 3.18 in those units if we add in some extra bits e.g. in the CAA. (Very rough estimate only! It just says it's plausible we could have another low year - perhaps a record or close to a record. Whether that happens or not is still up to the weather and the ocean currents.)
« Last Edit: July 18, 2017, 03:44:50 PM by slow wing »

marcel_g

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Re: Latest PIOMAS update (mid July update)
« Reply #2001 on: July 18, 2017, 03:50:59 PM »
Thanks Wipneus, always interesting!

So the current ice thickness contours are fairly simple in shape: nearly triangular at 1.75m, 1.50m, 1.25m and weighted to the Atlantic side; and with the Pacific side filled out to form more of a trapezoid at the 1.00m contour.

I kind of expect some of that 1.0m contour to survive, considering how cloudy the last week or so has been. A lot of that depends on where the winds blow the ice over the next month or so, and whether all the rain that Climate Reanalyzer has been showing all over the ice has indeed been rain, rather than snow. If the winds blow the pack over the now open peripheral seas, then a lot of the 1m and even thicker ice will melt too.

Who knows though, maybe large areas of the ice have been absorbing heat and are ready to go poof.

Thomas Barlow

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Re: Latest PIOMAS update (mid July update)
« Reply #2002 on: July 18, 2017, 04:23:26 PM »
An update to the Inner Basin volume chart. The gap to 2012/2011 closed by ~300km3, which is ~200km3 more than expected by my "method" and a sign of lowering probabilities for records. My next extrapolations were shifted upwards accordingly. In my next post I will attempt to find out which region contributed the most to this.
Thanks for the graph! Great to see !
It would be interesting to see if the CAA is making a difference to the overall here ( I think you include CAA?).
On its own the Inner Basin graph may look different without all that thick ice stuck in the CAA this year (compared to 2016 and 2012).
You don't have Baffin Bay in there right?

In other words, there appears to be more volume in the CAA this year than in these other years shown below. So that could skew the main Arctic Ocean volume figure.

DMI - I took out Arctic basin just to focus on looking at CAA
(I know they changed their method over the years, but this is close enough visually.)
« Last Edit: July 18, 2017, 04:48:36 PM by Thomas Barlow »

Thomas Barlow

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Re: Latest PIOMAS update (mid July update)
« Reply #2003 on: July 18, 2017, 04:42:44 PM »
Just for comparison here is the CAA at in Sept. 2016

oren

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Re: Latest PIOMAS update (mid July update)
« Reply #2004 on: July 18, 2017, 04:55:41 PM »
TB, I dislike DMI volume comparisons as I find the volume model unreliable.
In any case, my table shows 2017 having some more volume in the CAA. In absolute figures it's 579 km3 vs. 462 in 2012. It's not a huge difference though.

Thomas Barlow

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Re: Latest PIOMAS update (mid July update)
« Reply #2005 on: July 18, 2017, 05:35:59 PM »
An update to the Inner Basin volume chart. The gap to 2012/2011 closed by ~300km3

In any case, my table shows 2017 having some more volume in the CAA. In absolute figures it's 579 km3 vs. 462 in 2012. It's not a huge difference though.
Right, so for the Arctic Ocean, the gap closed in on 2012 by <200km3, not ~300km3 ? :-)
Thanks again !  Great work!
« Last Edit: July 18, 2017, 05:42:04 PM by Thomas Barlow »

magnamentis

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Re: Latest PIOMAS update (mid July update)
« Reply #2006 on: July 18, 2017, 05:53:31 PM »

I kind of expect some of that 1.0m contour to survive, considering how cloudy the last week or so has been. A lot of that depends on where the winds blow the ice over the next month or so, and whether all the rain that Climate Reanalyzer has been showing all over the ice has indeed been rain, rather than snow. If the winds blow the pack over the now open peripheral seas, then a lot of the 1m and even thicker ice will melt too.

Who knows though, maybe large areas of the ice have been absorbing heat and are ready to go poof.

there is not much surface melting needed to deal with a meter in july because as far as i understand, bottem melt will almost eat one meter alone ( at least close to ) hence 1 meter ice in july to my understanding is more or less doomed to a very high degree, even if not 100% in all places, depending on currents and other factors like cyclone paths later in the season.
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Thomas Barlow

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Re: Latest PIOMAS update (mid July update)
« Reply #2007 on: July 18, 2017, 05:54:51 PM »
Thanks again to Oren for the Inner Basin Graph.
I think this is the most interesting information going on right now.

Just for fun, I did try to make an adjustment (in red) for the CAA, by adding about 100+ km3 more loss, to indicate Arctic Ocean only as of now, and even though it does not make much difference right now, I intuit it does change the potential trajectory a little, which over time, could be a lot.
A lot of the Arctic Ocean is clearly vulnerable, especially if the next 2 months are warmer than usual. ( I consider the Arctic Ocean separate from everything else, since I think that at some point, a phase transition (tipping point - ie. collapse) is reached, because it is an ocean - not a fjord.)
« Last Edit: July 19, 2017, 05:19:43 PM by Thomas Barlow »

Wipneus

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Re: Latest PIOMAS update (mid July update)
« Reply #2008 on: July 19, 2017, 07:15:19 PM »
Fram daily export was more negative than positive in the first 15 days in July. IOW it was more like import, all according to the PIOMAS model.

Pi26

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Re: Latest PIOMAS update (mid July update)
« Reply #2009 on: July 19, 2017, 07:50:13 PM »
Fram daily export was more negative than positive in the first 15 days in July. IOW it was more like import, all according to the PIOMAS model.

Yes, it was more like an import of a Trojan Horse   :-\

Pavel

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Re: Latest PIOMAS update (mid July update)
« Reply #2010 on: July 21, 2017, 03:01:24 PM »
The remaining ice in the Pacific side (which all FYI) will reach the zero thickness by the end of season. The SIE and volume minimun can be definitely lower than 2012

A-Team

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Re: Latest PIOMAS update (mid July update)
« Reply #2011 on: July 21, 2017, 04:12:51 PM »
remaining ice in the Pacific side (which is all FYI) will reach zero thickness
Briefly, as I am headed out to 'Glacier' Nat'l Park for two weeks.

Pavel is raising a critical point here, that Piomas does not track ice that formed from open water last fall (and winter!) and indeed seems oblivious to its current distribution.

For this, we want the NSIDC weekly sea ice age animation (which is available through Mar 2017). Tschudi et al have shown this is -- unsurprisingly -- a reasonably accurate proxy for sea ice thickness:

Comparisons of ice age and thickness estimates derived from both ICESat (2004–2008) and IceBridge (2009–2015) reveal that the relationship between age and thickness differs between these two campaigns, due in part to the difference in area of coverage. Nonetheless, sea ice thickness and age exhibit a direct relationship when compared on pan-Arctic or regional spatial scales. [free full: http://www.mdpi.com/2072-4292/8/6/457/htm]
Hycom, though positioning itself as a thickness resource, also tracks sea ice age, perhaps unintentionally through its palette design (oscillating grayscale over hue). Not only that, it is the only ice map that ventures out into the coming week. In a bland summer like this one, that has been working quite well.

This +AO/+NAO pattern has been very persistent, with very few breaks since last fall. Quite remarkable.(Csnavywx's post #2994)
The new ice will not be of a uniform thickness depending on how cold the air and water have been where its arms have drifted, but given the winter these differences will be fairly small and the ice thinner and weaker than say adjacent 2nd year ice. Thus it will melt out sooner. You can see that development underway below for the long arm of 1st year ice extending Svalbard-ward (arrows).

Thus it doesn't matter whether Hycom's absolute thickness is better or worse than Piomas if it's being used for tracking first year ice.

The lower two animations use wip's recent concentration maps to illustrate the puzzling anomaly of this year relative to July of 2016 in the Beaufort. Here the second frame seeks to remove cloud and storm artifacts by taking the darkest pixel in the stack which works fairly well when the ice is not moving much as clouds are transient and whiter. The 4th frame grays show the standard deviation in each pixel stack. (These are gif operations in ImageJ.)
« Last Edit: July 21, 2017, 04:45:08 PM by A-Team »

Wipneus

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Re: Latest PIOMAS update (mid July update)
« Reply #2012 on: July 25, 2017, 08:25:27 AM »
giceday was updated to 22nd July.

Here are the volume numbers 1-22 July (day 182-203):

array([ 11.91,  11.7 ,  11.48,  11.27,  11.07,  10.88,  10.65,  10.41,
        10.21,  10.04,   9.86,   9.68,   9.5 ,   9.25,   9.02,   8.83,
         8.68,   8.52,   8.34,   8.16,   7.99,   7.82])


Volume gap with 2012 still exists,  about 0.1 [1000km3], hardly significant.

Remember that giceday-derived numbers do not replicate exactly with the gridded thickness and official volume numbers.


Cid_Yama

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Re: Latest PIOMAS update (mid July update)
« Reply #2013 on: July 25, 2017, 08:31:20 AM »
Thank You.

Wipneus

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Re: Latest PIOMAS update (mid July update)
« Reply #2014 on: July 25, 2017, 08:59:18 AM »
The area per thickness category is shown for 22 July. See my previous posts for an explanation.

My naive interpretation:
- Until 2007 all ice thicker than 0.26 m survived until the September minimum, the less than 0.26 m ice survived partly;
- After 2007 the ice below 0.26 m is almost always gone at the September minimum. For most years that is it, but in 2008, 2012 and 2016  thicker ice (up to 0.71 m) melts as well.

So assuming 2017 will be an average post 2007 year we can take the >0.26 m thickness line as proxy for the final September min.

This would predict the area minimum about the same as in 2010 and 2011, but as 2012 and 2016  show, a much lower result can not be ruled out.


oren

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Re: Latest PIOMAS update (mid July update)
« Reply #2015 on: July 25, 2017, 09:35:43 AM »
Thank you Wipneus (for the 100th time) for the data and the very interesting analysis. It seems 2017 leads in the thicker categories (>1.46, >2.61) but lags in the thinner ones (>0.26, >0.71) which could lead to a higher area/volume ratio at the minimum, making a record area very unlikely based on this data, but a record volume potentially more achievable.

Looking at a close-up of the total volume, 2017 continues to lead using the same gradient as the other low years, but 2012 could take the lead in the first half of August thanks to a certain GAC.
Note: Extrapolation now takes the 2nd-lowest loss (out of the 4 low years) instead of the lowest loss.
« Last Edit: July 25, 2017, 09:44:14 AM by oren »

Neven

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Re: Latest PIOMAS update (mid July update)
« Reply #2016 on: July 25, 2017, 09:53:52 AM »
Oh boy, this is getting exciting.  ;D 8)
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iceman

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Re: Latest PIOMAS update (mid July update)
« Reply #2017 on: July 25, 2017, 02:39:07 PM »
   ... It seems 2017 leads in the thicker categories (>1.46, >2.61) but lags in the thinner ones (>0.26, >0.71) which could lead to a higher area/volume ratio at the minimum, making a record area very unlikely based on this data, but a record volume potentially more achievable.
   ....
Not sure I follow your reasoning.  My take on the graph is that (relative to recent years) 2017 has proportionately less area in the thicker places.  If so, wouldn't we expect the area/volume ratio to drop faster than usual between now and the minimum?

Tor Bejnar

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Re: Latest PIOMAS update (mid July update)
« Reply #2018 on: July 25, 2017, 03:33:56 PM »
What I notice on Wipneus's graph is the September 10 plots used to be (1980 & 90s) consistently above the 0.26m plot and in recent years (starting in 2007, I believe) has tended towards being at or between the 0.26 and 0.71m plots.  I would suggest September 10, 2017 will follow this trend, and with a greater likelihood of it being closer to the 0.71m plot than the 0.26m plot. 

There won't be a record low ice volume, however, unless the minimum drops below the .71m point.  As there is more <0.26m ice than there was in 2012 (or 2016) on July 22, this might happen.

Disclamer:  Wipneus's graph shows the trends.  Weather will determine the details.  :)
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jdallen

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Re: Latest PIOMAS update (mid July update)
« Reply #2019 on: July 25, 2017, 05:26:00 PM »
What I notice on Wipneus's graph is the September 10 plots used to be (1980 & 90s) consistently above the 0.26m plot <snip>

Disclamer:  Wipneus's graph shows the trends.  Weather will determine the details.  :)
Very much in accord with this.  I think the key here is, unlike measuring area or extent, wip's strategy is actually a proxy for estimated heat uptake.  If I were building and placing buoys, I'd add sensors to measure full spectrum radiation.   There is a *partial proxy for *that* in the form of the voltages coming off of buoy solar arrays, but that's not complete. 
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oren

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Re: Latest PIOMAS update (mid July update)
« Reply #2020 on: July 25, 2017, 05:57:18 PM »
   ... It seems 2017 leads in the thicker categories (>1.46, >2.61) but lags in the thinner ones (>0.26, >0.71) which could lead to a higher area/volume ratio at the minimum, making a record area very unlikely based on this data, but a record volume potentially more achievable.
   ....
Not sure I follow your reasoning.  My take on the graph is that (relative to recent years) 2017 has proportionately less area in the thicker places.  If so, wouldn't we expect the area/volume ratio to drop faster than usual between now and the minimum?
Note that curently 2017's area/volume ratio is much higher than 2012 was at this point. It should drop faster, but still remain higher than 2012 at minimum.
Let me lay down my reasoning, as it took me a while to figure it out again...:

Typically the >0.26 figure determines the minimum, and in low years it's somewhere between the >0.26 and >0.71. At most, it drops a little below the >0.71.
As 2017 has a higher >0.26 area, (and slightly higher >0.71 as well) compared to 2012, it is not a natural candidate for breaking the area record, as 2012 had a freak August.
2016 is a case in point. It had a GAC in August, and indeed managed to crash the area, but looking at Wipneus' chart might explain why no record was achieved - the July >0.26 and >0.71 figures were too high.
So 2017 will need a freakier August than 2012 and 2016 to achieve an area record. Mostly it needs a bigger GAC. (Not saying it can't happen, just that it has a lower likelihood - when judging by this PIOMAS data).

OTOH, 2017 has the lowest ever July figures for the >1.46 and >2.61 ice types. So its final distribution at minimum could be expected to have lower average thickness = lower volume/area = higher area/volume compared to 2012. Meaning a low volume record is still possible without an area record.

ghoti

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Re: Latest PIOMAS update (mid July update)
« Reply #2021 on: July 25, 2017, 05:59:10 PM »
If I were building and placing buoys, I'd add sensors to measure full spectrum radiation.   

I'm actually very surprised the buoys don't have net radiometers on them. Used to be standard equipment for all micro-meteorology set ups. (okay my experience with this was 35 years ago but still...)

DavidR

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Re: Latest PIOMAS update (mid July update)
« Reply #2022 on: July 26, 2017, 03:01:05 AM »
Wipneus's graph appears to indicate that there is a greater area of thin ice and smaller area of thick ice than in 2012.  All the ice that is likely to  melt out can be classified as thin (< 0.71) for this analysis.

This means that  the same amount of volume loss, from July 22nd, as in 2012 should see a greater extent loss than 2012.  2012 had a very low volume loss after June 30th so there is no reason why 2017 can not acheive the same volume loss and hence a greater extent loss than 2012.

The 2012 GAC did NOT produce a larger volume loss than other years and some analyses have suggested that the record low extent was going to occur anyway because of the thinness of the ice. This years ice is even thinner, and at June 30th was about 2% thinner than 2012.

Tigertown

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Re: Latest PIOMAS update (mid July update)
« Reply #2023 on: July 26, 2017, 03:48:27 AM »
 DavidR
The 2012 GAC did NOT produce a larger volume loss than other years and some analyses have suggested that the record low extent was going to occur anyway because of the thinness of the ice. This years ice is even thinner, and at June 30th was about 2% thinner than 2012.

I really liked a point FishOutofWater made a day or two ago. The main pack still has fresh cool meltwater* near, under, and around it due mostly to lack of disturbances recently. Whether we see an extraordinary late melt may depend on how much storm and wave activity we see in the Arctic in the coming weeks. Enough wind and drift to pull water up from the deep, if persistent, could also do the trick. Don't forget late export via the CAA, Nares, and Fram.

* I wouldn't much count on that anywhere any light could pass through because of low concentration or thinner ice.

FishOutofWater

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Re: Latest PIOMAS update (mid July update)
« Reply #2024 on: July 26, 2017, 04:52:10 AM »
Thanks, Tigertown. My comment is supported by maps at Mercator Ocean. I would post those maps, but the ones that have the most useful information have different baselines, so my interpretations are based on repeated viewing of multiple maps. The Mercator ocean maps with a fixed baseline bottom out at -1 Celsius, shown in dark blue. At 30 meters depth that's all of the central Arctic ocean and most of the peripheral seas. The salinity maps are useful for tracking the intrusion of warm, salty Atlantic water along the Eurasian side of the Arctic ocean. The water loses most of its heat as it moves into the Arctic along the continental shelf break, but keeps most of its salinity.

Bottom melt is likely to be slow in the central Arctic over the next six weeks because the water under the ice is colder than it was last year based on Mercator Ocean maps. This situation was caused by the cool cloudy weather.

Rob Dekker

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Re: Latest PIOMAS update (mid July update)
« Reply #2025 on: July 26, 2017, 09:35:19 AM »
Very interesting discussion. Thank you everyone !

A while ago I postulated that the main question is : "does the Arctic summer melt 'extent' or does it melt 'volume' ?".

Intuitively one would expect the latter ; that a given summer provides a given amount of heat which would melt a given amount of volume of ice regardless of where that ice resides.

But it seems that the picture is more complicated than that.

Melting 'extent' lowers albedo, which suggests that thin ice would increase melting rates. Arctic amplification and all that. But even that is not certain, since it takes time for lower latitudes to warm up, and thus this ice might actually slow volume melt rates especially in the latter part of the season when insulation dwindles.

Either way, its remarkable that even now, at the end of July, neither PIOMAS volume numbers nor NSIDC extent and area numbers can tell us where this season is going.
It's yet again an exciting melting season.

Tigertown

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Re: Latest PIOMAS update (mid July update)
« Reply #2026 on: July 26, 2017, 12:19:21 PM »
Mentioning albedo, look at the whole pack. It is degrading in places where the concentration is lower and the ice is thinner. Where the pack is tighter and thicker, the ice seems to be holding out better.
Zoom in for better view of July 25th,2017.

magnamentis

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Re: Latest PIOMAS update (mid July update)
« Reply #2027 on: July 26, 2017, 06:52:36 PM »

Disclamer:  Wipneus's graph shows the trends.  Weather will determine the details.  :)

this while one day bottom melt will see to a surprise, when? who knows.

Tigertown came up with a nice analogy to termites, the moment it's visible the house falls appart but again, when? no-one can say for sure.
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Tigertown

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Re: Latest PIOMAS update (mid July update)
« Reply #2028 on: July 30, 2017, 08:19:33 AM »
Let's see. About 6,000 km3 sounds about right for the close of July.

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Re: Latest PIOMAS update (mid July update)
« Reply #2029 on: July 31, 2017, 11:56:50 AM »
The Danes, those damn vikings. I feel like I am about to throw a grenade in the thread. Ouch.

Below is what Denmark's Polar Portal has about volume and thickness.(http://polarportal.dk/en/havisen-i-arktis/nbsp/sea-ice-extent)
The volume graph shows a major slowdown in volume reduction.  I know many have severe doubts about their product but ...?
PIOMAS for July is due later this week?
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JayW

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Tor Bejnar

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Re: Latest PIOMAS update (mid July update)
« Reply #2031 on: July 31, 2017, 02:32:17 PM »
"Here's some 4 meter thick ice north of Hudson Bay according to DMI."
About a quarter (by my visual reckoning) of that 4-meter thick ice is still there!
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Tigertown

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Re: Latest PIOMAS update (mid July update)
« Reply #2032 on: July 31, 2017, 03:21:36 PM »
That's funny. Looks like DMI is at 7k+ km3 and JAXA is at about 5k. PIOMAS should come out in the middle. Not bad now, but I fear it may not stop dropping in a timely manner this year.

FredBear

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Re: Latest PIOMAS update (mid July update)
« Reply #2033 on: July 31, 2017, 05:51:41 PM »
Best clear day I found was July 22.  Here's some 4 meter thick ice  north of Hudson Bay according to DMI.

https://worldview.earthdata.nasa.gov/?p=arctic&l=VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor,Graticule,Reference_Labels(hidden),Reference_Features(hidden),Coastlines&t=2017-07-22&z=3&v=-2747565.536763592,-3276764.4458222506,-128570.57878258463,-657678.7228899474&r=44.9878



Think that is Foxe Basin - ice went to creamy mush weeks ago (see:- Stupid Questions :o
« Reply #1154 on: June 21, 2017, 08:06:28 PM » ) but never melts like mush but just swirls around! Is the basin shallow or mixing bad? The area also ends up with a creamy-coloured shoreline (which must be some sort of organism not ice?).
« Last Edit: July 31, 2017, 06:05:33 PM by FredBear »

oren

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Re: Latest PIOMAS update (mid July update)
« Reply #2034 on: July 31, 2017, 06:26:43 PM »
The Danes, those damn vikings. I feel like I am about to throw a grenade in the thread. Ouch.

Below is what Denmark's Polar Portal has about volume and thickness.(http://polarportal.dk/en/havisen-i-arktis/nbsp/sea-ice-extent)
The volume graph shows a major slowdown in volume reduction.  I know many have severe doubts about their product but ...?
PIOMAS for July is due later this week?
DMI is unreliable especially around the minimum. Besides local phenomena that don't match the actual ice, their refreeze point is too early and doesn't make sense at all. Why not start a thread about DMI volume? Or start/find a thread to compare DMI vs. PIOMAS and research which is more accurate. I don't think it adds much here in the PIOMAS thread. I doubt it is indicative of coming PIOMAS numbers one way or the other.

gerontocrat

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Re: Latest PIOMAS update (mid July update)
« Reply #2035 on: July 31, 2017, 06:39:36 PM »
An observer such as I has not the expertise to research why the sensors and algorithms from the various satellites and scientific institutes come up with such different results on volume. Maybe some genius somewhere will crack the technical problems. I hope so. Until then I guess one sticks to one set of results. Consistency and multi-year trends matter most?
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Re: Latest PIOMAS update (mid July update)
« Reply #2036 on: July 31, 2017, 06:50:43 PM »
An observer such as I has not the expertise to research why the sensors and algorithms from the various satellites and scientific institutes come up with such different results on volume. Maybe some genius somewhere will crack the technical problems. I hope so. Until then I guess one sticks to one set of results. Consistency and multi-year trends matter most?

One set of results in the threat devoted to that set -- and yes, consistency and trends.  Separate topics for comparing sets of results -- for estimating skill.

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Re: Latest PIOMAS update (mid July update)
« Reply #2037 on: July 31, 2017, 07:08:29 PM »
A passing comment or comparison about the other models tends to satisfy my curiosity. I can't imagine a thread for them. PIOMAS is the one, until proven otherwise.

Ned W

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Re: Latest PIOMAS update (mid July update)
« Reply #2038 on: August 03, 2017, 02:05:24 PM »
While we wait for the July monthly PIOMAS number, I thought I'd try my hand at predicting what it will be.  Here are the recent July monthly PIOMAS volumes:

2007   12.119
2008   14.154
2009   12.833
2010   10.244
2011   09.546
2012   09.264
2013   10.538
2014   11.951
2015   11.649
2016   10.257

and last month's (June's) value was 15.415.

I made a simple multivariate statistical model to predict this (the model's variables are a closely held secret...).  Here's the graph of modeled vs observed.  Blue points are the data used to make the model (1979-1999).  Gold points are hindcast data withheld for testing (2000-2016).  Red point is the prediction for 2017.



My prediction for July:  8.85, 95% CI 8.16 to 9.57. Chance of a new record low for July = 87%.

DavidR

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Re: Latest PIOMAS update (mid July update)
« Reply #2039 on: August 03, 2017, 03:24:52 PM »

I made a simple multivariate statistical model to predict this (the model's variables are a closely held secret...).  Here's the graph of modeled vs observed.  Blue points are the data used to make the model (1979-1999).  Gold points are hindcast data withheld for testing (2000-2016).  Red point is the prediction for 2017.


The increased rate of loss is very  evident from this graph. In the first  20 years the volume dropped by  bout 5K km^3. In the 17 years since then the loss has doubled. Even without a further increase in rate of loss there doesn't appear to  be much chance of ice after 2030. And that is for July! Not September!
 

Richard Rathbone

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Re: Latest PIOMAS update (mid July update)
« Reply #2040 on: August 03, 2017, 04:06:20 PM »

The increased rate of loss is very  evident from this graph. In the first  20 years the volume dropped by  bout 5K km^3. In the 17 years since then the loss has doubled. Even without a further increase in rate of loss there doesn't appear to  be much chance of ice after 2030. And that is for July! Not September!

July has if anything, a reduced rate of loss (the PIOMAS anomaly has almost always been at its lowest in June for the past decade, because June now has historically high melt rates, but July has melt rates that are low by historic standards)

My guess is 9.1 (8.9 was reasonable using the end June value, but the intermediate values show low loss rates)

oren

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Re: Latest PIOMAS update (mid July update)
« Reply #2041 on: August 03, 2017, 05:51:08 PM »
I don't know about the monthly number but my expectation for July 31st is around 6550-6600 km3, with some upside to 6800 to account for what seemed like a slow second half of the month. Just using basic extrapolation, not a model.

Ned W

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Re: Latest PIOMAS update (mid July update)
« Reply #2042 on: August 03, 2017, 06:07:31 PM »
Here is PIOMAS monthly volume, 1979-present, by month, scaled relative to the 1980-1989 average and smoothed with a 10-year LOESS function.



The biggest change has been in September.  Then there are symmetric pairs of months:
2nd and 3rd biggest change:  October & August
4th and 5th biggest change: November & July
6th and 7th:  December & June

Then the symmetry breaks down.  January has decreased faster than May, and February faster than March/April.

Ned W

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Re: Latest PIOMAS update (mid July update)
« Reply #2043 on: August 03, 2017, 06:18:42 PM »
I don't know about the monthly number but my expectation for July 31st is around 6550-6600 km3, with some upside to 6800 to account for what seemed like a slow second half of the month. Just using basic extrapolation, not a model.
OK, I can go with daily PIOMAS, instead of monthly. For July 31st I'd say 6.22, with a 95% CI of 5.50 to 6.94.

magnamentis

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Re: Latest PIOMAS update (mid July update)
« Reply #2044 on: August 03, 2017, 06:22:23 PM »
Here is PIOMAS monthly volume, 1979-present, by month, scaled relative to the 1980-1989 average and smoothed with a 10-year LOESS function.



The biggest change has been in September.  Then there are symmetric pairs of months:
2nd and 3rd biggest change:  October & August
4th and 5th biggest change: November & July
6th and 7th:  December & June

Then the symmetry breaks down.  January has decreased faster than May, and February faster than March/April.

in direct reply without reducing the value of those graphs for now, i want to repeat an earlier remark that once we get lower and lower the loss relative to earlier years are becoming smaller and smaller.

the month we gonna hit zero could be an august and the change could be very tiny.

what i'm heading at is that the lower we get the higher a small change is in percent and the more we gonna have to take naked compared numbers with a prise of salt and/or relativate them IMO

EDIT: i'm fully aware that we are far from zero volume, it's just the example that explains my point best.
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Blizzard92

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Re: Latest PIOMAS update (mid July update)
« Reply #2045 on: August 03, 2017, 08:32:27 PM »
My PIOMAS sea ice volume/thickness plots have all been updated for July 2017 at http://sites.uci.edu/zlabe/arctic-sea-ice-volumethickness/
UC Irvine - Earth System Science Ph.D. Candidate
Cornell University - Atmospheric Sciences B.Sc.

Twitter: @ZLabe
Website: http://sites.uci.edu/zlabe/

Ned W

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Re: Latest PIOMAS update (mid July update)
« Reply #2046 on: August 03, 2017, 09:21:50 PM »
July monthly average is 9.151 -- slightly higher than my prediction (8.85) but not too far (less than 1 sigma).

Ned W

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Re: Latest PIOMAS update (mid July update)
« Reply #2047 on: August 03, 2017, 09:25:06 PM »
And the July 31st daily value is 6.725 -- again, a bit higher than I'd guessed, and right around what Oren expected.  Nice!

Ned W

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Re: Latest PIOMAS update (mid July update)
« Reply #2048 on: August 03, 2017, 09:26:08 PM »
My PIOMAS sea ice volume/thickness plots have all been updated for July 2017 at http://sites.uci.edu/zlabe/arctic-sea-ice-volumethickness/
Nice visualizations, Zachary.  Very cool.

Tigertown

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Re: Latest PIOMAS update (mid July update)
« Reply #2049 on: August 03, 2017, 09:59:38 PM »
And the July 31st daily value is 6.725 -- again, a bit higher than I'd guessed, and right around what Oren expected.  Nice!
I think that is in better shape than any of us would have guessed. Yep. Oren takes home the prize on this one.