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kassy

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Re: "Stupid" Questions :o
« Reply #2650 on: September 26, 2019, 07:59:28 PM »
Does extracting oil and gas from underground cause subsidence?
It does. That is why we are stopping the gas production in the Groningen area. Quakes (very minor ones) are damaging houses.

If the millimeter or two is the actual number it is not that relevant compared to sea level rise.
That is at 0,3 cm per year (and bound to go up).

Is the area around the Persian Gulf sinking a millimeter or two a year, exacerbating SLR?

Land sinking does not make SLR worse but it makes the area effected more vulnerable to flooding.
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gerontocrat

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Re: "Stupid" Questions :o
« Reply #2651 on: September 26, 2019, 08:42:17 PM »
Here's one I could have put in the Oil & Gas thread, but just in case it's stupid, I'll put it here.
Does extracting oil and gas from underground cause subsidence? For example, is the area around the Persian Gulf sinking a millimeter or two a year, exacerbating SLR?
Yes, it did belong in the Oil & Gas thread, but, 

Forget SLR, minimal impact.

But... (not only Oil & Gas - over-extraction of groundwater causing big problems in some megacities, e.g. Tehran, Mexico City).  Not talking about a millimetre or two per year, but can be tens of centimetres of ground slump per year in the most vulnerable places. 

Count the ways mankind is screwing up the joint, they are legion.

Also happened in California during the unregulated 30's and 40's - the Trump Vision for the future.

Earthquakes in Oklahoma since fracking started.

https://www.forbes.com/sites/trevornace/2018/03/28/massive-oil-fields-in-texas-are-heaving-and-sinking-at-alarming-rates/#32c0a536c8b3

From a 2006 Paper.
https://www.researchgate.net/publication/242757170_SUBSIDENCE_PREDICTION_CAUSED_BY_THE_OIL_AND_GAS_DEVELOPMENT
Quote
Abstract:
Oil and gas development from underground reservoirs disturbs original rock mass balance. The tending of the rock mass to achieve a new, even only temporary balance is manifested in the movements of the ground surface. Movements can affect ground infrastructure like offshore platforms, pipelines and buildings.

1.  Introduction
Surface subsidence of areas where oil, gas and water are exploited are a serious problem in various parts of the World. In the coastal regions, vertical movements of the surface may result in flooding or generate extra costs for securing the banks.

Such problems were encountered, e.g. in the area of Maracaibo Lake in Venezuela (ca. 3.5 m – maximum subsidence), Mexican Gulf, in California (ca. 10 m – maximum subsidence) and in Japan. The subsidence troughs may be huge in size and the damage to the objects standing on them is comparable to those in the mining areas. Considerable deformations of surface usually can be found in the places where thick fluid reservoirs occur and the host rocks have compaction qualities.
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Richard Rathbone

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Re: "Stupid" Questions :o
« Reply #2652 on: September 27, 2019, 09:45:00 PM »
It depends on the reservoir, some are a lot more dependent on the pressure of the fluid in them than others, but if they are sensitive, subsidence can be pretty fast. I don't know about the Persian Gulf, but 10s of cm per year has happened as a result of oil and gas extraction as well as groundwater extraction.


ajouis

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Re: "Stupid" Questions :o
« Reply #2653 on: October 02, 2019, 02:57:07 AM »
When i worked on a glacier, the black ash that was on it actually insulated the ice, do you know if it still hold up at macro level or if the type of matter (volcanic ash) is important? Would be interested to hear of other phenomenas in the arctic where something doesn t work out as usual.

wallen

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Re: "Stupid" Questions :o
« Reply #2654 on: October 02, 2019, 07:15:58 AM »
When you look at Worldview and see the "Blackout " area extending daily, is this the extending limit of 24 hour darkness or a visual limitation of the satellite as the Arctic progresses toward winter.

nanning

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Re: "Stupid" Questions :o
« Reply #2655 on: October 02, 2019, 10:19:02 AM »
When i worked on a glacier, the black ash that was on it actually insulated the ice, do you know if it still hold up at macro level or if the type of matter (volcanic ash) is important? Would be interested to hear of other phenomenas in the arctic where something doesn t work out as usual.

What do you mean by "insulated the ice"?
Was there direct sunshine on the black ash? I expect it would heat up.
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ajouis

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Re: "Stupid" Questions :o
« Reply #2656 on: October 02, 2019, 11:44:47 AM »
When i worked on a glacier, the black ash that was on it actually insulated the ice, do you know if it still hold up at macro level or if the type of matter (volcanic ash) is important? Would be interested to hear of other phenomenas in the arctic where something doesn t work out as usual.

What do you mean by "insulated the ice"?
Was there direct sunshine on the black ash? I expect it would heat up.
Funnily enough the part with the ash thawed slower than the rest, as far as I understand because while the ash heated up, it reduced much of the radiation and convection heat towards the ice by sheltering it, leaving only very inefficient conduction to transmit the extra energy from the ash to the ice, which transmits less energy than the heat tranports on normal ice.

nanning

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Re: "Stupid" Questions :o
« Reply #2657 on: October 02, 2019, 05:13:53 PM »
<snip>
Funnily enough the part with the ash thawed slower than the rest, as far as I understand because while the ash heated up, it reduced much of the radiation and convection heat towards the ice by sheltering it, leaving only very inefficient conduction to transmit the extra energy from the ash to the ice, which transmits less energy than the heat tranports on normal ice.

Thank you very much for this information ajouis! I thought that the, by the radiation, heated black ash would melt down into the ice.
Your observation makes sense to me. Of course convection is a much stronger effect than thermal conduction. I understand better now :) .
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dnem

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Re: "Stupid" Questions :o
« Reply #2658 on: October 02, 2019, 06:13:04 PM »
I'm pretty sure the standard view of this is that atmospheric deposition of dark particles on clean ice reduces albedo and increases melt.

https://insideclimatenews.org/news/19042018/greenland-ice-sheet-melting-climate-change-arctic-pollution-sea-level-rise-algae-black-carbon

In areas near the edge of the ice sheet, things get even more interesting: a carpet of microbes and algae mixed with dust and soot, a short-lived climate pollutant, is darkening the ice sheet, absorbing the sun's rays and accelerating the melting of the ice.

New research shows this dark zone is growing.

binntho

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Re: "Stupid" Questions :o
« Reply #2659 on: October 02, 2019, 08:26:08 PM »
When i worked on a glacier, the black ash that was on it actually insulated the ice, do you know if it still hold up at macro level or if the type of matter (volcanic ash) is important? Would be interested to hear of other phenomenas in the arctic where something doesn t work out as usual.

This sounds right and can easily be observed on Icelandic glaciers. Apparently a layer of a few mm is enough to insulate the ice  causing black ridges and bumps. The ash is volcanic with fairly large grainsize.
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Tor Bejnar

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Re: "Stupid" Questions :o
« Reply #2660 on: October 02, 2019, 10:43:38 PM »
Layers of rock debris (e.g., from landslides falling onto the ice) on top of a glacier are well know to protect the ice from melting. Exceptional example from dreamstime.com

Obviously, this picture shows that not all rock debris actually protects the ice!
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dnem

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Re: "Stupid" Questions :o
« Reply #2661 on: October 03, 2019, 12:06:59 AM »
Jason Box Dark Snow Project:
https://www.darksnow.org

Wikipedia Dark Snow Project
https://en.wikipedia.org/wiki/Dark_Snow_Project
Background
"Soot darkens snow and ice, increasing solar energy absorption, hastening the melt of the cryosphere."[1] The soot comes in part from wildfires, of which there were many in 2012. Also in 2012, almost all of the surface of Greenland was observed to be melting.[9] The increase in size of the wildfires may itself be a result of global warming.[5] Jason Box has been studying Greenland for 20 years.

binntho

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Re: "Stupid" Questions :o
« Reply #2662 on: October 03, 2019, 09:01:56 AM »
Jason Box Dark Snow Project:
https://www.darksnow.org

Wikipedia Dark Snow Project
https://en.wikipedia.org/wiki/Dark_Snow_Project
Background
"Soot darkens snow and ice, increasing solar energy absorption, hastening the melt of the cryosphere."[1] The soot comes in part from wildfires, of which there were many in 2012. Also in 2012, almost all of the surface of Greenland was observed to be melting.[9] The increase in size of the wildfires may itself be a result of global warming.[5] Jason Box has been studying Greenland for 20 years.

We are talking about different things here. Soot from wildfires (and other sources) often called black carbon are never in sufficient amounts to create a thick blanket on ice. So their effect will always be to hasten melt.

Volcanic ash on the other hand can easily form layers several cm thick, and pumice is very insulating. Seeing black ridges of pumice-protected ice is very common in Iceland, and from personal experience I know that 1 or 2 mm of pumice is enough to slow down melt.
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Peter Ellis

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Re: "Stupid" Questions :o
« Reply #2663 on: October 04, 2019, 12:15:38 AM »
Pumice is also foamy with a lot of trapped air, which makes it an excellent insulator.

dnem

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Re: "Stupid" Questions :o
« Reply #2664 on: October 04, 2019, 01:06:29 PM »
For sure. The original post that started this used the phrase "black ash" which to me sounded like soot or black carbon.

binntho

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Re: "Stupid" Questions :o
« Reply #2665 on: October 05, 2019, 01:14:00 PM »
For sure. The original post that started this used the phrase "black ash" which to me sounded like soot or black carbon.
A very natural mistake to make since in Icelandic volcanic ash is normally black and looks more like sand than pumice. Even so it still has good insulation properties since the individual grains are very rough and even at times frothy, unlike sand which is smooth-grained.
because a thing is eloquently expressed it should not be taken to be as necessarily true
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Thomas Barlow

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Re: "Stupid" Questions :o
« Reply #2666 on: October 07, 2019, 12:03:40 AM »
Is there a mean for yearly sea ice extent comparing year to year?
Not sure how you would do that, but maybe there is a general method?  Maybe adding monthly averages up for each year? Or weekly?


« Last Edit: October 07, 2019, 02:31:06 PM by Thomas Barlow »

dnem

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Re: "Stupid" Questions :o
« Reply #2667 on: October 07, 2019, 02:42:11 PM »
gerontocrat frequently posts a running 365 day average on the Area and Extent thread that somewhat captures what you're looking for.

Niall Dollard

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Re: "Stupid" Questions :o
« Reply #2668 on: October 14, 2019, 11:55:24 PM »
I posted this originally in the Mike Horn expedition thread :

But here is a question. Mike mentions he was about 87 N. Should the sun be below the horizon by this date ? I plugged this lattitude into a couple of online solar angle calculators and they are saying max angle is circa -4 degrees ie below the horizon.

https://keisan.casio.com/exec/system/1224682277

To still see the sun you would need to be near 82 N (according to the online calculations).

Or maybe the calculations are not taking into account the flattening at the poles ? 


binntho

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Re: "Stupid" Questions :o
« Reply #2669 on: Today at 07:21:48 AM »
Good question Niall. Over on the Mosaic thread A-Team posted a picture of two ships meeting in the polar "night" on Oktober 3rd, presumably around 85N, and it certainly looks a lot more like "early twilight" to me. But less than two weeks after equinox I guess it makes sense for that location, even if the sun doesn't tecnnically rise.

The image above is apparently from Oktober 13th, some three weeks after equinox, and according to my favourite solar altitude calculator, the sun should not rise at all on that date at 87N.

Judging by the picture, the sun is at perhaps 0.2 degrees, which would place the location at no further north than ~82N for that date as far as I can work out.
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slow wing

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Re: "Stupid" Questions :o
« Reply #2670 on: Today at 11:10:14 AM »
I posted this originally in the Mike Horn expedition thread :

But here is a question. Mike mentions he was about 87 N. Should the sun be below the horizon by this date ? I plugged this lattitude into a couple of online solar angle calculators and they are saying max angle is circa -4 degrees ie below the horizon.

https://keisan.casio.com/exec/system/1224682277

To still see the sun you would need to be near 82 N (according to the online calculations).

Or maybe the calculations are not taking into account the flattening at the poles ?

Agree it is puzzling. However, there is some refraction of sunlight in the atmosphere. Wikipedia says that at sunset it is 35.4' -- so more than half a degree. So that accounts for a small part of the discrepancy.

This website, which includes refraction, says there is no direct sunlight but still 4h19 minutes of "civil twilight" at 87N, even now on 15th October, which is two days after the photo.


binntho

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Re: "Stupid" Questions :o
« Reply #2671 on: Today at 11:12:35 AM »
Wonder what "uncivil twilight" looks like ...  :o
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Tor Bejnar

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Re: "Stupid" Questions :o
« Reply #2672 on: Today at 02:58:48 PM »
Aren't search engines wonderful?
Quote
title: an uncivil twilight summary: Is everyone here make-believe? — Baelfire/Wendy/Peter. —..... Neverland was nothing like Bae had thought it would be like. He'd thought there'd be no responsibilities, no rules—but of course, that had been a delusion brought on by Peter Pan's flute.
and, less cherry:
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In The Colder Case Series,  Uncivil Twilight is the 1925 case about the trial of S.C. Stone …
Arctic ice is healthy for children and other living things.