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Freegrass

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Re: "Stupid" Questions :o
« Reply #3150 on: April 15, 2020, 05:03:41 PM »
I don't think you're wrong. Sublimation requires energy, and if water evaporates (or ice sublimates) into dry air, this leads to a drop in localized temperature.

The Arabs were famous for having flowing water and even small fountains next to their pavilions and maqhaas, as a low-technology air conditioner, utilizing the cooling effect of evaporation.

Same will happen with ice even in cold circumstances - if the air is very dry then some ice will sublimate and the air gets even colder. But of course, warm dry air is a true ice killer (e.g. foehn winds or the Chinook, the adiabatic effect often causing surprisingly hot air to stream over ice and snow), and dry and sunny weather also sees ice and snow disappear very quickly.
Does sublimation happen in the arctic when high pressure makes way for low pressure?
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Re: "Stupid" Questions :o
« Reply #3151 on: April 15, 2020, 10:02:09 PM »
I'm thinking sublimation occurs whenever the air is dry, temps matter less, so if dry wind passes over the ice and sublimation occurs just how much does that cool the ice? Another Q. is if there's any spume and that dries in the same wind how fast does the now airborne salt cool down the ice?
To be clear i'm suggesting that dry air at say -2C passes over ice at -6C and having passed the ice is now at -8C or maybe -20C.

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Re: "Stupid" Questions :o
« Reply #3152 on: April 17, 2020, 08:36:34 PM »
I was wondering if anyone could help me understand the latest graph Zack labe posted?

https://twitter.com/ZLabe/status/1251170252735430658

http://psc.apl.uw.edu/research/projects/piomas-20c/

Does this mean one mode shows more melt and is correct or?

oren

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Re: "Stupid" Questions :o
« Reply #3153 on: April 17, 2020, 09:25:35 PM »
I think it means that the 20th century volume reconstruction by PIOMAS (of which I am not very familiar) more or less matches the shape of the satellite-era volume as modeled by PIOMAS, and correctly reconstructs the decline since 1990, although it does not match the absolute modeled value.
I would expect the more "correct" value is the satellite-era PIOMAS.

kassy

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Re: "Stupid" Questions :o
« Reply #3154 on: April 18, 2020, 12:39:41 PM »

Caution: There are some differences between the standard PIOMAS data set and PIOMAS-20C as illustrated in the paper. Simple concatenation of the two to extend of either is not recommended. We hope to at some point create a data set that is inter-calibrated.


So lets see the paper:

https://journals.ametsoc.org/doi/10.1175/JCLI-D-19-0008.1

PIOMAS-20C, an Arctic sea ice reconstruction for 1901–2010, is produced by forcing the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) with ERA-20C atmospheric data. ERA-20C performance over Arctic sea ice is assessed by comparisons with measurements and data from other reanalyses. ERA-20C performs similarly with respect to the annual cycle of downwelling radiation, air temperature, and wind speed compared to reanalyses with more extensive data assimilation such as ERA-Interim and MERRA. PIOMAS-20C sea ice thickness and volume are then compared with in situ and aircraft remote sensing observations for the period of ~1950–2010. Error statistics are similar to those for PIOMAS. We compare the magnitude and patterns of sea ice variability between the first half of the twentieth century (1901–40) and the more recent period (1980–2010), both marked by sea ice decline in the Arctic. The first period contains the so-called early-twentieth-century warming (ETCW; ~1920–40) during which the Atlantic sector saw a significant decline in sea ice volume, but the Pacific sector did not. The sea ice decline over the 1979–2010 period is pan-Arctic and 6 times larger than the net decline during the 1901–40 period. Sea ice volume trends reconstructed solely from surface temperature anomalies are smaller than PIOMAS-20C, suggesting that mechanisms other than warming, such as changes in ice motion and deformation, played a significant role in determining sea ice volume trends during both periods.

and further on:

Using the trends from the respective runs to estimate relative sea ice volume loss, we have lost 65% of the total Arctic sea ice volume in September from 1979 to 2010 using PIOMAS-20C. This number is reduced to 55% for PIOMAS. Ice loss for the ice volume maximum in April is smaller, with 41% for PIOMAS-20C and 35% for PIOMAS. The greater volume loss trends in PIOMAS-20C relative to PIOMAS arise from the fact that ice thickness in the Beaufort and Chukchi Seas is larger in PIOMAS-20C during the early 1980s than for PIOMAS. Extending the period through 2016 shows a total volume loss of 72% for September and 35% for April from PIOMAS.

Trend differences arise mostly from sea ice volume differences during the early 1980s when the two reconstructions show the largest differences. Examining ice thickness differences from ThickCDR provides additional clues. ThickCDR data from 1979 to 1984 from U.S. submarines shows a small bias (−0.03 m) for PIOMAS-20C and a larger one for PIOMAS (−0.61 m). Therefore, PIOMAS-20C ice thickness may indeed reflect ice thickness during the early 1980s more accurately than PIOMAS. Ice-ocean model integrations with atmospheric forcing fields from different reanalysis datasets (Lindsay et al. 2014; see their Fig. 13) but without data assimilation, also showed that the integration using NCEP-R1 forcing had substantially lower volume during the early 1980s. While this is supportive of our previous result that PIOMAS provides a conservative estimate of sea ice volume loss (Schweiger et al. 2011), we do not believe it provides sufficient evidence to decide which of the simulations provides the more accurate estimate of sea ice volume and trend. Instead the differences should be viewed as a measure of the uncertainty in the reconstructed sea ice volume in either dataset.

So they are basically comparing two models.

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kassy

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Re: "Stupid" Questions :o
« Reply #3155 on: April 18, 2020, 12:49:40 PM »
I have a question of my own.

It is related to the above post and some stuff about keels mentioned recently.

The US submarine data mentioned above would be from radar?

What is the newest sub data climate scientists got to use?

Could we send a small submersible with a radar to measure the ice from below? (In theory)

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Zinc_wit

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Re: "Stupid" Questions :o
« Reply #3156 on: April 18, 2020, 01:54:20 PM »
Thanks for the answers Oren and Kassy!
Much appreciated.

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Re: "Stupid" Questions :o
« Reply #3157 on: April 18, 2020, 02:46:01 PM »
I have a question of my own.

It is related to the above post and some stuff about keels mentioned recently.

The US submarine data mentioned above would be from radar?

Perhaps... ping...ping...  Sonar will reflect from any solid surface, and subs need it to find safe places to surface.

ps: I wonder f the Russians have released any of their data.
pps: those subs are still at it.
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Freegrass

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Re: "Stupid" Questions :o
« Reply #3158 on: April 18, 2020, 04:58:50 PM »
Could we send a small submersible with a radar to measure the ice from below? (In theory)
Unrelated, but I've had this question in my head now for many many years...

Is it possible to create a submersible device that recharges its own battery by going up and down in the water column? When I became a diver 25 years ago, I learned a lot about water pressure, and the immensity of it in the oceans. I immediately starting thinking of ways to harness this potential energy, and one of the ways to harness this energy is by going up and down in the water column.

But then you bump into Newton... Conservation of energy... The energy you collect at the bottom of the ocean will be needed to bring that device back up to the surface... So that's a zero sum game...

And then one day the light came on... Currents! What if we made some kind of underwater kite, that uses the currents to go up and down in the water column? That way you use the energy of motion to overcome Newton...

And what about the tags you attach to whales? Whales go up and down... So it should be easy to recharge the battery, right?

And then small submarines... They also go up and down by using wings and a propeller. So can't they be designed in a way that they could stay submerged perpetually?

I guess now I'm not gonna get rich with this idea if it works?  :-[ ;) ;D
I lack the mathematical skills to do the calculations. So can anyone put me out of my misery? Has this been thought of before?  :-\
« Last Edit: April 18, 2020, 05:11:23 PM by Freegrass »
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ruffed

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Re: "Stupid" Questions :o
« Reply #3159 on: April 18, 2020, 05:08:04 PM »
stop playing with yourself

oren

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Re: "Stupid" Questions :o
« Reply #3160 on: April 18, 2020, 06:37:20 PM »
FG, many have come up with ideas that somehow use free energy indefinitely. However, conservation of energy should have told you they are impossible. So forget the imagined riches.
Of course, pouring a few millions into maintaining a small fleet of submersibles that recharge themselves occasionally and measure the ice (and water temps) from below shouldn't be a big problem if someone actually cared enough to do it. The same goes for a large array of mass balance buoys, hopefully integrated with cameras uploading photos to the web. Yet the budgets mostly seem to be missing, and what we get are only occasional projects.

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Re: "Stupid" Questions :o
« Reply #3161 on: April 18, 2020, 06:52:20 PM »
I guess now I'm not gonna get rich with this idea if it works?

Be sure of this: If you manage to build the Perpetuum Mobile, you will get rich AF!  ;D
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Freegrass

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Re: "Stupid" Questions :o
« Reply #3162 on: April 18, 2020, 07:39:21 PM »
Of course, pouring a few millions into maintaining a small fleet of submersibles that recharge themselves occasionally and measure the ice (and water temps) from below shouldn't be a big problem if someone actually cared enough to do it.
So many sub-ocean technologies have to resurface to recharge themselves. I'm just wondering why nobody ever thought about using piezoelectric energy.
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mitch

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Re: "Stupid" Questions :o
« Reply #3163 on: April 18, 2020, 08:26:40 PM »
The big problem for a fleet of AUV's measuring ice thickness is the energy expended to ping on the subsurface of the ice.  This take significant energy, and batteries don't release energy well when they are cold. So, one has to work out how to recharge the AUV's.

The 2nd problem is tracking the AUV depth, since any depth error translates into an ice thickness issue.  It is possible to use pressure as a depth measure, but must correct for the salinity of the water, since adding salt to fresh water makes about a 3% difference going to ocean salinity. 

Freegrass

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Re: "Stupid" Questions :o
« Reply #3164 on: April 18, 2020, 08:34:21 PM »
The big problem for a fleet of AUV's measuring ice thickness is the energy expended to ping on the subsurface of the ice.  This take significant energy, and batteries don't release energy well when they are cold. So, one has to work out how to recharge the AUV's.

The 2nd problem is tracking the AUV depth, since any depth error translates into an ice thickness issue.  It is possible to use pressure as a depth measure, but must correct for the salinity of the water, since adding salt to fresh water makes about a 3% difference going to ocean salinity.
Couldn't you solve the second problem by pinging both top and bottom? When you know the topography, you should know where you are, no? Maybe with AI?
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Tor Bejnar

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Re: "Stupid" Questions :o
« Reply #3165 on: April 18, 2020, 10:46:39 PM »
https://qz.com/1483333/electricity-with-underwater-energy-kites-may-soon-take-off/
Quote
The physics of underwater kites are similar to those in the air. High-flying “wings” are tethered to the seabed with a cable. Each kite flies a massive figure eight pattern. As water flows over its 12-meter wingspan, the kite swoops through the current producing kinetic energy (movement). Turbines attached to the wing spin, converting this into electricity. As it “flies” at least 20 meters below the surface, the kite can move at several times the speed of the current.
Makani kites:  airborne wind energy

I wonder if underwater kites could be attached to MYI floes, rather than to the seabed.  AUVs could return to charging stations when needed. ...

I don't think this will happen by this coming NH summer!
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uniquorn

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Re: "Stupid" Questions :o
« Reply #3166 on: April 23, 2020, 01:39:13 PM »
Any ideas on what happened to mosaic Thermistor buoy T72 on apr13. The case still appears to be on ice as the near surface air temperatures are similar to other buoys in the area, yet the ice temperatures beneath it have risen to closer to water temperature.


« Last Edit: April 23, 2020, 01:46:53 PM by uniquorn »

blumenkraft

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Re: "Stupid" Questions :o
« Reply #3167 on: April 23, 2020, 02:07:16 PM »
Uniquorn, they are now in Atlantic waters. Could have been a (smallish) warm current from the south, no?
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uniquorn

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Re: "Stupid" Questions :o
« Reply #3168 on: April 23, 2020, 03:55:11 PM »
Thanks for the quick response. I should have explained the chart better.
Before apr13: (approximate numbers)
Thermistors 1-25 were above the ice recording near surface air temps
25-30 were probably snow
30-130 were ice
>130 were ocean

So ocean temperatures haven't altered much but the ice temperature has risen significantly. Looking at today's recent data the surface appears to be be melting changing rapidly.
« Last Edit: April 23, 2020, 07:52:17 PM by uniquorn »

blumenkraft

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Re: "Stupid" Questions :o
« Reply #3169 on: April 23, 2020, 07:35:19 PM »
Sorry, Uniquorn. Should have read that more closely.
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uniquorn

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Re: "Stupid" Questions :o
« Reply #3170 on: April 23, 2020, 08:11:28 PM »
No problem. I just can't think of a scenario that warms up the ice but leaves the buoy operational with the top of the thermistor strip continuing to record air temperature. Maybe a very close shave with a ridge event, causing nearly 2m thick ice to go horizontal? A really close lead?
Temps are dropping at the surface suggesting freezing (not melting)
« Last Edit: April 23, 2020, 08:20:09 PM by uniquorn »

oren

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Re: "Stupid" Questions :o
« Reply #3171 on: April 24, 2020, 02:45:15 AM »
Very strange.
It appears from the behavior of the chart in post #3166 like an inundation with seawater at the top of the ice.

johnm33

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Re: "Stupid" Questions :o
« Reply #3172 on: April 24, 2020, 01:35:54 PM »
Sunshine? small amount of heating from current? small hollow caused by wind action on 'string'? water running down 'string?

kassy

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Re: "Stupid" Questions :o
« Reply #3173 on: April 24, 2020, 04:22:04 PM »
There was a warming event after the 13th or so it looked like on the second GIF. But then i don´t know how strange this behaviour is or what the normal patterns look like. The ridge event should mess with the top thermistors? So i would think the lead more likely.

How much of these are around now?
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Re: "Stupid" Questions :o
« Reply #3174 on: April 25, 2020, 03:07:43 PM »
There are still 10 active Tbuoys, 11 if T69 is included.
T72 is settling down again now, refreezing towards a more normal temperature profile

Interesting how quickly the ice temperature rose though.
« Last Edit: April 25, 2020, 04:07:07 PM by uniquorn »

uniquorn

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Re: "Stupid" Questions :o
« Reply #3175 on: April 25, 2020, 07:22:39 PM »
Maybe something like this happened only on a much larger scale
https://twitter.com/sthendric/status/1253646129587261440
Water possibly forced to the surface
« Last Edit: April 25, 2020, 07:31:36 PM by uniquorn »

oren

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Re: "Stupid" Questions :o
« Reply #3176 on: April 25, 2020, 11:49:31 PM »
I think only seawater has enough heat capacity to bring the core ice temp up so fast. Plus the fact ice surface temp jumped to that of Arctic seawater.

PragmaticAntithesis

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Re: "Stupid" Questions :o
« Reply #3177 on: May 01, 2020, 12:27:34 AM »
I've noticed a persistent ridge in thickness going North from Svalbard, through the North Pole, and into the ESS. What's causing this ridge? (Or am I actually looking at an ice thickness valley coming from the Fram Strait and going North to the ESS?)
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Re: "Stupid" Questions :o
« Reply #3178 on: May 02, 2020, 11:18:00 PM »
Twice I've asked a stupid question about salt and ice, well here are two answers
"Although the hydration process gives off heat, this is more than compensated for by the heat absorbed during the initial decomposition of the salt into ions. In other words, the total process of dissolution--decomposition into ions plus hydration--absorbs heat. This can easily be demonstrated: pour some water into a glass and test its temperature with your finger. Add some salt, stir, and test it again. The temperature will have decreased.

The actual reason that the application of salt causes ice to melt is that a solution of water and dissolved salt has a lower freezing point than pure water. When added to ice, salt first dissolves in the film of liquid water that is always present on the surface, thereby lowering its freezing point below the ices temperature. Ice in contact with salty water therefore melts, creating more liquid water, which dissolves more salt, thereby causing more ice to melt, and so on. The higher the concentration of dissolved salt, the lower its overall freezing point. There is a limit, however, to the amount of salt that can be dissolved in water. Water containing a maximum amount of dissolved salt has a freezing point of about zero degrees Fahrenheit. Therefore, the application of salt will not melt the ice on a sidewalk if the temperature is below zero degrees F.

To understand why water containing dissolved salt has a lower freezing point than pure water, consider that when ice and water are in contact there is a dynamic exchange at the interface of the two phase states. Because of thermal vibrations in the ice, a large number of molecules per second become detached from its surface and enter into the water. During the same period of time, a large number of water molecules attach themselves to the surface of the ice and become part of the solid phase. At higher temperatures, the former rate is faster than the latter and the ice melts. At lower temperatures the reverse is true. At the freezing point the two rates are equal. If salt is dissolved in the water, the rate of detachment of the ice molecules is unaffected but the rate at which water molecules attach to the ice surface is decreased, mainly because the concentration of water molecules in the liquid (molecules per cubic centimeter) is lower. Hence, the melting point is lower.

John Margrave, a chemistry professor at Rice University, explains.

All icy surfaces in fact contain small puddles of water. Because salt is soluble in water, salt applied to such surfaces dissolves. Liquid water has what is known as a high dielectric constant, which allows the ions in the salt (positively charged sodium and negatively charged chlorine) to separate. These ions, in turn, react with water molecules and hydrate that is, form hydrated ions (charged ions joined to water molecules). This process gives off heat, because hydrates are more stable than the individual ions. That energy then melts microscopic parts of the ice surface. Thus a substantial amount of salt spread over a large surface can actually thaw the ice. In addition, if you drive over the ice in your automobile, the pressure helps force the salt into the ice and more of this hydration occurs." from https://www.scientificamerican.com/article/why-do-we-put-salt-on-icy/
Also found out that 00F is the coldest you can make water by adding salt.
So I'm assuming that airborne salt from waves splashing seawater into the air as leads open and close will be carried some small distance before settling on ice, that ice then has an enhanced 'wet' signature until the cold dry arctic ice reduces its temperature by evaporation to somewhat below 255K [00F] 235K? https://go.nasa.gov/3bYLMsX

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Re: "Stupid" Questions :o
« Reply #3179 on: May 03, 2020, 03:44:46 AM »
Twice I've asked a stupid question about salt and ice, well here are two answers
<snip>
The best place for these is "basic questions about melting physics" thread

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Re: "Stupid" Questions :o
« Reply #3180 on: May 06, 2020, 08:40:49 PM »
I've noticed that PIOMAS and DMI are in disagreement over volume numbers. The DMI is claiming that 2020 is a record low for volume for May 5th, while PIOMAS claims volume is currently around the 2010's average and 2017 was significantly lower than any other year on this day.

How do the two insitutions differ in the way they measure sea ice volume, and what does a difference this dramatic between the different volume measurements indicate?
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Re: "Stupid" Questions :o
« Reply #3181 on: May 06, 2020, 08:50:37 PM »
There is a thread dedicated to the topic, PA. :)

Link >> https://forum.arctic-sea-ice.net/index.php/topic,8.msg262954.html#new
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Re: "Stupid" Questions :o
« Reply #3182 on: May 06, 2020, 10:04:30 PM »
I've noticed that PIOMAS and DMI are in disagreement over volume numbers. The DMI is claiming that 2020 is a record low for volume for May 5th, while PIOMAS claims volume is currently around the 2010's average and 2017 was significantly lower than any other year on this day.

How do the two insitutions differ in the way they measure sea ice volume, and what does a difference this dramatic between the different volume measurements indicate?

The DMI data doesn't pass the smell test and is incongruent with the more reliable 2D data from JAXA. Some people are just interested in looking for a rationale to hype the melt season.

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Re: "Stupid" Questions :o
« Reply #3183 on: May 07, 2020, 03:24:00 AM »
There is a thread dedicated to the topic, PA. :)

Link >> https://forum.arctic-sea-ice.net/index.php/topic,8.msg262954.html#new
DMI volume should be discussed in its own specific thread:
https://forum.arctic-sea-ice.net/index.php/topic,3076.0.html
I have cross-posted the question there.

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Re: "Stupid" Questions :o
« Reply #3184 on: May 07, 2020, 04:29:33 AM »
I don't think a question can ever be "stupid"... You can be ignorant, an amateur, a newbie, or a child. But never stupid! Because stupid people wouldn't be able to find this forum...  ;)
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Re: "Stupid" Questions :o
« Reply #3185 on: May 07, 2020, 05:32:52 AM »
Hi Freegrass, you state that a question can never be stupid. Then you write that this is so because there are no stupid people on this forum. That contradicts your first statement because it means that questions CAN be stupid, just not from non-stupid people.

I think that 'stupid' (low intelligence) people can ask very interesting questions and I think that high intelligence people can ask 'stupid' (uninteresting, obvious answer, basic knowledge) questions.
I don't think the meaning of 'stupid' in 'stupid people' and 'stupid question' are in the same context. What might a 'low-intelligence' question mean?

Good that the thread title has double quotes around the word.
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Re: "Stupid" Questions :o
« Reply #3186 on: May 07, 2020, 07:40:55 AM »
I think the title is apt for this forum.
It gives you the freedom to ask a question and know it is going to be excepted and maybe even answered no matter what it is .

We are only "smart" apes after all.
We don't have to always be 100% correct  humor and sarcasm is allowed and welcome .

Glen Koehler

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Re: "Stupid" Questions :o
« Reply #3187 on: May 19, 2020, 11:04:10 PM »
      What are useful criteria to interpret the impact of high and low pressure systems on the Arctic Sea Ice? 

       I think Neven said last year that pressure over 1033 hPa was a threshold for strong effect from high pressure. 

      I don't have an equivalent value for low pressure other than that the Great Arctic Cyclone in August 2012 was unprecedented for reaching 966 hPa for an extended period over a large area.

      So I am proposing 1030 or higher on the high side as a threshold for major impact and 980 or lower on the low side.  I suspect it may not be as simple as fixed threshold levels, esp. for the low-pressure impact.  The proximity and difference between adjacent low and high-pressure systems could be the determining factor in wind speed and effect on the ice.  But a rule of thumb for interpreting high and low-pressure readings would be useful.

igs

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Re: "Stupid" Questions :o
« Reply #3188 on: May 20, 2020, 12:27:45 AM »
      What are useful criteria to interpret the impact of high and low pressure systems on the Arctic Sea Ice? 

       I think Neven said last year that pressure over 1033 hPa was a threshold for strong effect from high pressure. 

      I don't have an equivalent value for low pressure other than that the Great Arctic Cyclone in August 2012 was unprecedented for reaching 966 hPa for an extended period over a large area.

      So I am proposing 1030 or higher on the high side as a threshold for major impact and 980 or lower on the low side.  I suspect it may not be as simple as fixed threshold levels, esp. for the low-pressure impact.  The proximity and difference between adjacent low and high-pressure systems could be the determining factor in wind speed and effect on the ice.  But a rule of thumb for interpreting high and low-pressure readings would be useful.


I think it is less about the pressure itself but about the general rotation and the relation between that and the rotation of a pressure system.


Means:


If the arctic ice is generally rotating clockwise a pressure syste that rotates clockwise would compact the ice while a pressure system that would rotate against the ice rotation would disperse it.


Most of the time the ice is rotating clockwise which is why highs that rotate clockwise would compact the ice and vice versa.


Arctic means norther hemisphere, an important point because south of the equator it's the other way around.


Knowledge that does not increase every day will decrease every day !

oren

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Re: "Stupid" Questions :o
« Reply #3189 on: May 20, 2020, 07:19:24 AM »
Glen, this is far from my area of expertise (if there is any) but it strongly depends on the time of year. From my layman's knowledge, high pressure brings with it clear skies, thus is the most dangerous in June and July. Low pressure - if extreme - brings with it Ekman pumping and is most dangerous in August when the water is warmer. And the difference between high and low pressure is what decides the wind, with the most dangerous setup is such that the wind would result in strong export, thus a low over the Barents is more dangerous.

bluice

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Re: "Stupid" Questions :o
« Reply #3190 on: May 23, 2020, 12:40:04 PM »
Is there a known correlation between Hudson Bay and CAA melting? Intuitively it would make sense that frozen Hudson would protect ice in the CAA. Then again, these two areas only share very little direct connections.

We are seeing rapid melting in Hudson ATM and I’m wondering if this will affect CAA also.

gerontocrat

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Re: "Stupid" Questions :o
« Reply #3191 on: May 23, 2020, 01:03:52 PM »
I don't think a question can ever be "stupid"... You can be ignorant, an amateur, a newbie, or a child. But never stupid! Because stupid people wouldn't be able to find this forum...  ;)

"Because stupid people wouldn't be able to find this forum..."

It took me a long, long time to find this forum.
And then it was by accident.
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Jump

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Re: "Stupid" Questions :o
« Reply #3192 on: May 23, 2020, 11:02:55 PM »
So my stupid question is about the sea ice graph
https://nsidc.org/arcticseaicenews/charctic-interactive-sea-ice-graph/
For a while I have wondered what is the cause for the change in melt rate in June. On individual years it is hard to see but when you look at the interquartile range or interdecile range there is a clear elbow in the graph.
I joined the forum to ask this question, I usually follow the melt season in the same way that I check the weather, however I had often wondered about the shape of this graph but hadn't read anything about it. Thanks (hope I have put his in the right place)

nanning

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Re: "Stupid" Questions :o
« Reply #3193 on: May 24, 2020, 04:28:35 AM »
Quote from: gerontocrat
It took me a long, long time to find this forum.

Same here.
And my 'by accident' was a comment somewhere in the Guardian written by someone called 'gerontocrat'.
"It is preoccupation with possessions, more than anything else, that prevents us from living freely and nobly" - Bertrand Russell
"It is preoccupation with what other people from your groups think of you, that prevents you from living freely and nobly" - Nanning S. Poelsma
Prisons in your head!

Bruce Steele

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Re: "Stupid" Questions :o
« Reply #3194 on: May 24, 2020, 06:15:58 AM »
Back in 2012 I had come across the Jim Pettit “ death spiral “ graph and the internet pointed me to this post about it on Neven’s “Arctic Sea ice Blog” Aug 3 2012. Neven put out a Cyclone Warning two days later.

https://neven1.typepad.com/blog/2012/08/piomas-august-2012.html

Thanks Neven . And to Jim and everyone who helped .

oren

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Re: "Stupid" Questions :o
« Reply #3195 on: May 24, 2020, 07:38:40 AM »
Welcome Jump. The first post is the hardest.
I think the June change of melting pace has to do with the geographics of the Arctic. The High Arctic is surrounded by land on most sides. Beyond that are the peripheral seas. In April most extent reductions are in the periphery as thevsun get progressively higher in the sky, but the easy to melt ice mostly runs out during May. In June losses are mostly in the Inner Basin, which thanks to its higher thickness and stabilizing land borders can resist melting much longer. The extent loss rate gap is caused by the need to breach the surrounding land fortress.
I am sure this can all be better quantified. Also take a look at the regional extent graphs of the various seas, this will help explain it better.

oren

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Re: "Stupid" Questions :o
« Reply #3196 on: May 24, 2020, 08:03:44 AM »

oren

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Re: "Stupid" Questions :o
« Reply #3197 on: May 24, 2020, 08:12:54 AM »
A more detailed response to the "June elbow", using the regional NSIDC extent graphs:
* Okhotsk and Bering mostly melt in April and early May.
* Kara and Laptev only start melting in June, the same applies to the Beaufort and Chukchi.
* The landlocked and huge Hudson (forgotten in my earlier response) also starts melting only in June, but then has extensive and predictable losses.
* The only seas losing extent linearly during May are Barents, Greenland and Baffin.

Thus when the main engines die out but the other haven't begun we get the May slowdown, in turn causing the June "elbow".
I get the feeling that if Hudson Bay was taken out of the stats, that elbow could disappear.

blumenkraft

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Re: "Stupid" Questions :o
« Reply #3198 on: May 24, 2020, 09:06:36 AM »
The fact that (average) temperatures go positive around this time could also be a factor contributing to the 'elbow', no?

Hello and welcome, Jump. :)
Unlearn things daily.