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Author Topic: System for evaluating melting seasons ??  (Read 2647 times)

Rich

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System for evaluating melting seasons ??
« on: June 29, 2019, 03:55:38 AM »
I'm thinking out loud here about a rating system for melt seasons and I'll use 2019 as an example. I'll consider it similar to evaluating a baseball player where a guy like Mike Trout is considered the best because he does so many things well, but is not necessarily the best in any single attribute

Ultimately, ice melts as a new result of it's intersection with heat. There are a lot of ways that can come about.

1. Atmospheric Heat (2019 score 8.5 / 10)

Plenty of early season heat. Recent scorching heat off Siberia. Consistency in terms of maintaining a positive anomaly throughout.

2. Ocean Heat (10 / 10)

The Pacific side is off the charts and the Atlantic is sporting a 0.5C positive anomaly.

3. Insolation / Albedo Reduction (8.5/10)

A fair amount of high pressure systems and early season open water.

4. Wind damage (6 / 10)

The Beaufort cyclone is a good example of this. Turned the gyre into rubble. Exposed a lot of surface area to ocean heat. We've also seen a tailwind pushing Laptev open water toward the pole and are now seeing Pacific water coming through the Bering Strait.

Not in the league with the 2012 GAC.

5. Export - Wind and Current (10/10)

Nares has been open. Fram has been steady. Perhaps the most important feature of the season has been the wind assisted push of ice to warm water to the Beaufort, Barents and Fram.

6. Rain (1/3)

Not much rain to speak of this year.  ;)

7. Starting Point (4.5 / 5)

2019 started the year from a low max. Less work to do.

8. Intangibles / Momentum (2/2)

Here's a category that gives the reviewer a little bit of leeway. I'll give 2019 some bonus points for strong momentum and no letup.

All in all, we come up with a score of 50.5 out of 60 possible and that is for a season that is ranking among the leaders in many categories.

This is just a straw man / food for thought. It's clear that there is a challenge in evaluating a season and benchmarking vs prior years. A system like this is intended to steer the focus toward the root causes of the end result and is easily accessible in terms of understanding.

No pride of ownership here. If someone sees a useful variant of this, feel free to run with it.

Neven

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Re: System for evaluating melting seasons ??
« Reply #1 on: June 29, 2019, 10:16:37 AM »
It's a good idea, but a lot of work, because I would suggest to do this for every month.
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oren

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Re: System for evaluating melting seasons ??
« Reply #2 on: June 29, 2019, 12:29:37 PM »
I would add PIOMAS volume, ice age distribution from NSIDC, Tealight's AWP, Wipneus's Inner Basin area.

kassy

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Re: System for evaluating melting seasons ??
« Reply #3 on: June 29, 2019, 05:50:06 PM »
Are you sure it is 8.5/10 , 10/10? It´s hard to make each of those measures as objective as possible.

I use a crude system.

Whatever happens early on is not that important because it is the summer that decides the fate of the ice. And the seas that melt out all years don´t really matter so i watch the developments in the Central Arctic Seas where the ice is.

And in the long run i watch the freeze seasons to see which fringe areas stay open longest.

The rating that counts is the actual lowest end state of the ice which is just the beginning state for next year. 

It´s like horse racing. You want to know which horse wins, whatever they are doing by turn 2 is not important even if we get accurate mm distances.

It would be cool to have objective data on 1-6 but we don´t have those so we are stuck with SIE and SIA.
Þetta minnismerki er til vitnis um að við vitum hvað er að gerast og hvað þarf að gera. Aðeins þú veist hvort við gerðum eitthvað.

Neven

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Re: System for evaluating melting seasons ??
« Reply #4 on: June 29, 2019, 06:10:43 PM »
First you have to determine categories, like Rich has done. Then you have to assign weight to each category. And then you need a multiplier based on ranking. For instance, all the categories combined are 100 points, and you say that SLP is worth 15 points. You then compare all years since 2005 for SLP in June, that would be 15 years in total. If you think that 2019 is number 2 (by eyeballing, of course), the 15 points of the SLP category would be multiplied by 14 = 210 points.

You do that every month, and then accumulate the points. I would start in April, or maybe May.

The hardest thing is assigning weight to each category. And determining categories isn't easy, either, and they would probably change from month to month. It really would be a lot of work. I sort of do it, in an inconsistent way, for melting momentum, and still can't say anything for sure.
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magnamentis

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Re: System for evaluating melting seasons ??
« Reply #5 on: June 29, 2019, 06:20:45 PM »
that's how i decided in the past which cars to purchase (when i had many LOL)

FUN aside, this is a great idea, i suggest using excel to begin with because later, onc would like to improve the table, make changes to it etc., there will always be a solid base that remains calculated and that is structured in the right order.

further i would NOT add piomas as a criteria because as much it has a value to compare PIOMAS seasons with each other because the flaws are persistent, to add obviously falsa data to a new model would make that anyways difficult task almost impossible.

all models are somehow flawed, hence one should at least reduce the know errors to the absolute possible minimum.

either way this is IMO a great idea, a bit biased probably because this is exactly who i do evaluations for many things to keep track of the various factors and being able to adapt their weight and values should need arise.
« Last Edit: June 29, 2019, 06:44:56 PM by magnamentis »

Sterks

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Re: System for evaluating melting seasons ??
« Reply #6 on: June 29, 2019, 06:47:02 PM »
Thanks for this Rich, nice work.
To start, I would give more weight to early momentum

and would use European metrics, that is, Leo Messi for analogous (tho he's a 10 in just about anything in football/soccer)

Sterks

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Re: System for evaluating melting seasons ??
« Reply #7 on: June 29, 2019, 08:35:40 PM »
Early NH Spring and land snow cover melt out too

be cause

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Re: System for evaluating melting seasons ??
« Reply #8 on: June 29, 2019, 10:15:26 PM »
I agree with Sterks re early momentum .. I forecast a top 2 year on !st March based on my daily observations throughout the freezing season combined with Uniquorn's animation . I remember being rather excited early in 2016 that there would be open ocean at the pole . Then ,as Gerontocrat's perfectly timed graph of dispersion ( melting season post 2835) shows , whereas in 2012 ice compacted in August , in 2016 ice dispersed . A year that could have easily held the record instead becomes a footnote . And no open ocean at the pole . b.c.

 
 
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 + 2 = 2021 + 1 .. it's 2022 !

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Re: System for evaluating melting seasons ??
« Reply #9 on: June 29, 2019, 11:51:19 PM »
Rich, we use a cheap low energy computer here to store all our data. It could probably calculate all the variables you consider relevant. Considering the small outlay and information input  you could offer the forum I think it's a 'no brainer' to buy one.

Rich

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Re: System for evaluating melting seasons ??
« Reply #10 on: June 30, 2019, 01:20:29 AM »
Thanks for the feedback and positive reception folks.

I don't sense that there is a hard quantification to be achieved here by me. If someone else wants to...fine with me.

As indicated previously, the purpose of the metric is to try and ground the discussion in the fundamentals which drive the melting result. As an ice wrecking entity, the 2019 melting season appears to have no weakness and I'm trying to come up with an objective framework for assessing it. I'm all for acknowledging uncertainty  about weather to come in the remainder of the season, but the thing that we're currently watching is like a Cat 5 hurricane spinning in the ocean. It's a beast and we shouldn't be shy about acknowledging that.

Perhaps in a few weeks I'll update it and give it a pronoun (Naming suggestions welcome...hurricanes have the Dvorak Scale...) I'll give some thoughts to the suggestions posted here as well.

One last thing. I don't have the benefit of experience when it comes to prior melt seasons so my benchmarking of various attributes is more intuitive.

Once again, thanks for the encouragement.

Rich

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Re: System for evaluating melting seasons ??
« Reply #11 on: July 02, 2019, 03:39:26 PM »
.

1. Atmospheric Heat (2019 score 8.5 / 10)

Plenty of early season heat. Recent scorching heat off Siberia. Consistency in terms of maintaining a positive anomaly throughout.

2. Ocean Heat (10 / 10)

The Pacific side is off the charts and the Atlantic is sporting a 0.5C positive anomaly.

3. Insolation / Albedo Reduction (8.5/10)

A fair amount of high pressure systems and early season open water.

4. Wind damage (6 / 10)

The Beaufort cyclone is a good example of this. Turned the gyre into rubble. Exposed a lot of surface area to ocean heat. We've also seen a tailwind pushing Laptev open water toward the pole and are now seeing Pacific water coming through the Bering Strait.

Not in the league with the 2012 GAC.

5. Export - Wind and Current (10/10)

Nares has been open. Fram has been steady. Perhaps the most important feature of the season has been the wind assisted push of ice to warm water to the Beaufort, Barents and Fram.

6. Rain (1/3)

Not much rain to speak of this year.  ;)

7. Starting Point (4.5 / 5)

2019 started the year from a low max. Less work to do.

8. Intangibles / Momentum (2/2)

Here's a category that gives the reviewer a little bit of leeway. I'll give 2019 some bonus points for strong momentum and no letup.

All in all, we come up with a score of 50.5 out of 60 possible and that is for a season that is ranking among the leaders in many categories.


I'm going for a little update and slight downgrade of 2019.

Atmospheric and ocean heat were a combined 18.5 / 20 in the initial pass. I'm downgrading here for two reasons. The intense heat near the Laptev has receded and is replaced by less acute heat in other areas. The other reason is that most of the positive heat anomaly is located in areas where the ice is already gone. That warm water / air on the Pacific side isn't optimally placed to do damage. CAA will get more action.

New score 16 / 20.

Rain

I'll bump this up to from 1/3 to 2/3. We're going to get some on the Pacific side with modest warmth and plenty of wind.

Composite score down from 50.5 to 49.

Momentum is still solid. We've lost > 2.3n km2 of area in 3 weeks and the Final Four of 2018 (CAB, CAA, ESS, and Beaufort) have lost > 100k in the last 2 days.

I'm learning as I go here. Not always pretty. I don't mind my ignorance being revealed, but important to be respectful of others. I get a zero this week. Ciao.


Glen Koehler

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Re: System for evaluating melting seasons ??
« Reply #12 on: August 19, 2022, 04:01:14 PM »
    This thread died, but given the continued evolution of the ASI it still seems like a useful idea if anybody has time for a data analysis project.  I don't recall seeing a multi-faceted index of ASI health in the annual Arctic Report card and other reports.  Even if the selection of indicators and weighting is necessarily arbitrary and based on guesswork, it would be still be an interesting index to watch (and argue about!). 

     It might be interesting to have a thread on Atlantification, Pacification, Trans-Arctic drift, Farm/Nares export, and other ocean-scale influences on the ASI.  Overall ocean warming and salinity changes drive about 60% of ASI decline vs. 40% atmospheric.  I don't know if there are changes in current and drift occurring, but Atlantification seems to be a progressive event, and Pacific water inflow is also important.

      We have daily weather to monitor the above water surface influences so that, along with top side imagery, is how we track the ASI.  But there is actually more impact happening below the water line, though much less monitoring information to track and predict that influence, so we don't pay much attention to it.  I don't know if there are observations and metrics comparable to what we use on the atmospheric side.  One foundation would be ocean water temperature measures from the fleets of buoys that Uniquorn and others monitor. If there is a suite of other such measures it would be useful to have them aggregated into one place for a synoptic view of the bottom side situation.  I'm all talk and no action as far as doing such an aggregation, but if there are good measures it would be interesting to at least learn what they are and where they are posted.
   
     Came upon the "System for Evaluating..." thread while looking for a place to post an interesting study about Davis Strait export.  (Davis Strait export collects from the Nares Strait and also the garlic press openings through the CAA).  The continuous flow through the Nares Strait this year has me wondering how Davis Strait export volume in 2022 will compare to past years.

Multiyear Volume, Liquid Freshwater, and Sea Ice Transports through Davis Strait, 2004–10.  2014.  B. Curry, C. M. Lee, B. Petrie, R. E. Moritz, and R. Kwok. DOI: https://doi.org/10.1175/JPO-D-13-0177.1

    "Davis Strait is a primary gateway for freshwater exchange between the Arctic and North Atlantic Oceans including freshwater contributions from west Greenland and Canadian Arctic Archipelago glacial melt. Data from six years (2004–10) of continuous measurements collected by a full-strait moored array and concurrent high-resolution Seaglider surveys are used to estimate volume and liquid freshwater transports through Davis Strait, with respective annual averages of −1.6 ± 0.5 Sverdrups (Sv; 1 Sv ≡ 106 m3 s−1) and −93 ± 6 mSv (negative sign indicates southward transport). Sea ice export contributes an additional −10 ± 1 mSv of freshwater transport, estimated using satellite ice area transport and moored upward-looking sonar ice thickness measurements. Interannual and annual variability of the net transports are large, with average annual volume and liquid freshwater transport standard deviations of 0.7 Sv and 17 mSv and with interannual standard deviations of 0.3 Sv and 15 mSv. Moreover, there are no clear trends in the net transports over the 6-yr period. "

and "Reanalysis of Davis Strait mooring data from the period 1987–90, compared to the 2004–10 measurements, reveals less arctic outflow and warmer, more saline North Atlantic inflow during the most recent period."




The minus values in the charts indicate southward flow.
« Last Edit: August 20, 2022, 02:14:44 AM by Glen Koehler »
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oren

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Re: System for evaluating melting seasons ??
« Reply #13 on: August 20, 2022, 12:44:17 AM »
Good points Glen (as usual). I think what we are missing are more objective regional or Arctic wide metrics. Besides extent, area and some volume measures, average temps and pressures, we are missing a lot of what goes down in 3-D and below the ice. How to change this, I'm not sure.

Quote
a full-strait moored array and concurrent high-resolution Seaglider surveys
This would be very helpful in Nares and main CAA passages, and in the wider Fram and Bering if feasible. But if it's not a permanent feature with real time or near real time data, it won't help much.
Having data for 1987-90 and 2004-2010, analyzed after the fact, doesn't help any current melting season to compare to previous ones, even though it provides good data for scientific papers and PhD-level analyses.

binntho

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Re: System for evaluating melting seasons ??
« Reply #14 on: August 22, 2022, 04:06:55 PM »
Overall ocean warming and salinity changes drive about 60% of ASI decline vs. 40% atmospheric.

Where do you get these numbers from?
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Glen Koehler

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Re: System for evaluating melting seasons ??
« Reply #15 on: August 23, 2022, 01:28:30 AM »
Overall ocean warming and salinity changes drive about 60% of ASI decline vs. 40% atmospheric.

Where do you get these numbers from?
     I can't recall the specific source, just that it really surprised me to read that ocean SST was more important than weather so I made a note to tuck that one away into my memory bank - which is usually pretty good but certainly not infallible.  Alas, I went looking through my scantily noted collection of ASI journal articles just now and can't find the smoking gun.  Instead of a journal article, it might have been in an IPCC report or one of the annual Arctic Report Cards.  I will check through files I have tucked away for those sources.

     The short answer for now is "I don't know where I got that from".  But it may be worse than that.  In looking through the journal articles Ding et al "Influence of high-latitude atmospheric circulation changes on summertime Arctic sea ice" DOI: 10.1038/NCLIMATE3241 uses a 60% figure for the contribution of atmospheric warming on ASI decline, and the rest being internal variability.  Which is completely different than my "60% ocean and 40% atmosphere" statement.

     Hoping for quick redemption before having to wade through IPCC tome looking for a source of the 60:40 ocean:atmosphere statement, I thought it might be useful to check in with my favorite synoptic ASI article Stroeve and Dirk 2018 .  I know that wasn't the source, but since they summarize what is causing ASI decline, I thought they might have something say about the ocean influence.  But this sentence from their intro only convicted me more: 
"Most of the observed changes in the sea-ice cover are driven by anthropogenic warming from increasing atmospheric greenhouse gas concentrations (e.g. Notz and Marotzke 2012, IPCC 2013, Notz and Stroeve 2016), amplified by internal variability (e.g. Ding et al 2017, Notz 2017)."

"These drivers do, however, not affect the sea ice directly, but instead they modify the atmospheric and oceanic forcing on the ice cover, which then in turn cause the sea-ice cover to shrink and thus serve to visualize the often invisible changes in the atmosphere and in the ocean"

     That leaves open the possibility of AGW raising ocean temperatures that then transport the heat into the Arctic Ocean as a major driver of ASI decline.  But it doesn't say that.   

"Obviously, rising air temperature is a prime suspect for driving increased sea ice melt. This is first based on the simple fact that ice melts faster the warmer it is, but is further made plausible by the very robust linear relationship between the long-term trend in the spatial coverage of Arctic sea ice and the long-term trend in global mean near-surface air temperature, both in model simulations and in the observational record"

"A study by Burgard and Notz (2017) has found that CMIP5 models disagree on whether the anomalous heating of the Arctic Ocean, and thus the loss of Arctic sea ice, primarily occurs
through changes in vertical heat exchanges with the atmosphere (as is the case in 11 CMIP5 models), primarily through changes in meridional ocean heat flux (as is the case in 11 other CMIP5 models) or through a combination of both (as is the case in 4 CMIP5 models). This suggests that our understanding of how precisely the heat for the observed sea ice melt is provided to the sea ice is still surprisingly limited."

     Stroeve and Notz go on to discuss oceanic pathways (Atlantic and Pacific water infiltration), but don't get anywhere close to supporting the 60:40 ocean:atmosphere statement.
"Changing state of Arctic sea ice across all seasons", Julienne Stroeve and Dirk Notz 2018 Environ. Res. Lett. 13 103001.

     Some support for the ocean heat contribution comes from Decuypère et al 2022 - "The Arctic has experienced a dramatic decrease in its sea ice cover over the past four decades. One of the main drivers of this intense melting is ocean heat transport from lower latitudes into the Arctic. "

"A better representation of OHT is needed to improve projections of sea ice extent (SIE), as the ocean is one of the main drivers of sea ice loss and variability in the Arctic (Bitz et al., 2005)."

"Decadal variability in ocean heat transport explains a large fraction of decadal variability in sea ice extent" 
     But they also say "At interannual timescale, the impact of ocean heat transport on sea ice extent is limited to the shelf regions". 

     And the 60:40 ocean:atmosphere claim gets dinged pretty hard by this statement in a section titled "Impact of OHT on SIE at a Pan-Arctic Scale" -   
"The trends in the September SIE in the Medium and High resolutions are around −0.6 × 10^6 km2/model decade (significant at the 95% confidence level), much smaller in absolute value than the observed trend of −1.6 million km2/model decade in the satellite era."
Decuypère, M., Tremblay, L. B., & Dufour, C. O. (2022). Impact of ocean heat transport on Arctic sea ice variability in the GFDL CM2-O model suite. Journal of Geophysical Research: Oceans, 127, e2021JC017762. https://doi.org/10.1029/2021JC017762

     My understanding of that statement is that OHT accounts for about 0.6/1.6 of SIE decline, i.e. about 38%, not 60%.  (Though they also note that the model simulations from which these values are derived consistently underestimate ASI decline).

     There is this from Bitz et al. 2005:  "In regions where the ice edge extends relatively far equatorward, absorbed solar radiation is the largest component of the ocean energy budget, and the large seasonal range of insolation causes the ice edge to traverse a large distance. In contrast, at relatively high latitudes, the ocean heat flux convergence is the largest component and it has a relatively small annual range, so the ice edge traverses a much smaller distance there."
    Bitz, C. M., Holland, M. M., Hunke, E. C., & Moritz, R. E. (2005). Maintenance of the Sea-Ice Edge, Journal of Climate, 18(15), 2903-2921.  https://journals.ametsoc.org/view/journals/clim/18/15/jcli3428.1.xml

     But this is defensive posturing to patch over the fact that I cannot recall where I got the 60:40 statement.  I don't think innocent until proven guilty applies in the court of science blogs.  Instead, it is the opposite, i.e. you have to back up what you say with credible sources, i.e. you're guilty of speculating until proven innocent.  My case is not looking good so far.  While I'm not ready to plead guilty of memory malfeasance and throw myself to the mercy of the court, until further notice of finding of the source I must retract that statement.  :-X 
« Last Edit: August 23, 2022, 01:50:41 AM by Glen Koehler »
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Glen Koehler

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Re: System for evaluating melting seasons ??
« Reply #16 on: August 23, 2022, 02:23:43 AM »
Not the source of the 60:40 statement, but good review of oceanic warming of ASI by David Docquier and Torben Koenigk 2021 Environ. Res. Lett. 16 123002.  https://iopscience.iop.org/article/10.1088/1748-9326/ac30be

"The CESM-LE large ensemble (1850–2100, using RCP8.5 scenario) suggests that ∼80% of the rapid sea-ice declines in the Arctic are correlated with increased ocean heat transport, mainly at the Barents Sea Opening and Bering Strait (Auclair and Tremblay 2018)."

--------------------------------------------

"What’s causing this decline in minimum sea ice extent? The short answer is our changing climate. But the more specific answer is that Arctic sea ice is increasingly being thinned not just by warm air from above but by ever-warmer waters from below.  In fact, in a recently published
scientific study my colleagues and I looked at why sea ice was melting in the eastern Arctic Ocean and showed that the influence of heat from the interior of the ocean has now overtaken the influence of the atmosphere."

"Arctic sea ice is being increasingly melted from below by warming Atlantic water"  Tom Rippeth.
 The Conversation.  Sept. 18, 2020.  https://theconversation.com/arctic-sea-ice-is-being-increasingly-melted-from-below-by-warming-atlantic-water-144106

Journal article:  Polyakov, I. V., Rippeth, T. P., Fer, I., Alkire, M. B., Baumann, T. M., Carmack, E. C., Ingvaldsen, R., Ivanov, V. V., Janout, M., Lind, S., Padman, L., Pnyushkov, A. V., & Rember, R. (2020). Weakening of Cold Halocline Layer Exposes Sea Ice to Oceanic Heat in the Eastern Arctic Ocean, Journal of Climate, 33(18), 8107-8123. Retrieved Aug 23, 2022, from https://journals.ametsoc.org/view/journals/clim/33/18/jcliD190976.
« Last Edit: August 23, 2022, 03:27:13 AM by Glen Koehler »
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binntho

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Re: System for evaluating melting seasons ??
« Reply #17 on: August 23, 2022, 02:25:11 PM »
Thanks Glen, I personally would guess (if asked) that melting caused by ocean heat and atmospheric heat were similar in magnitude - and 60/40 is as likely as 40/60.

Perhaps the bigger question should be whether the ratio is changing. I suspect it may be increasing in favour of ocean-driven melt, and much of the literature you quote above seems to supports that.
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