OT: Modelling the Greenland ice sheet

On Monday, June 24, 2019 at 6:00:34 PM UTC+2, upsid...@downunder.com wrote:
On Mon, 24 Jun 2019 07:35:54 -0700 (PDT), Bill Sloman
bill.sloman@ieee.org> wrote:

On Monday, June 24, 2019 at 2:35:28 PM UTC+2, upsid...@downunder.com wrote:
On Mon, 24 Jun 2019 04:06:37 -0700 (PDT), Bill Sloman
bill.sloman@ieee.org> wrote:

On Sunday, June 23, 2019 at 8:05:25 PM UTC+2, upsid...@downunder.com wrote:
On Sun, 23 Jun 2019 08:16:42 -0700 (PDT), Bill Sloman
bill.sloman@ieee.org> wrote:

On Friday, June 21, 2019 at 4:07:49 PM UTC+2, upsid...@downunder.com wrote:
On Fri, 21 Jun 2019 05:28:55 -0700 (PDT), Bill Sloman
bill.sloman@ieee.org> wrote:

Thus week's Proceedings of the (US) National Academy of Science had a slightly worrying paper on the economics of the disintegration of the Greenland ice sheet

https://www.pnas.org/content/116/25/12261.abstract?etoc

The worrying part is that economists who wrote it don't seem to have got the idea that the ice sheet could suddenly start sliding off in large chunks, as ice sheets have been known to do in the not all-that-geological past, like at the end of the most recent ice age.

To help the ice to flow, first liquid water is needed e.g. in ice
lakes during the summer, gravasses are needed so that the water will
suddenly flow under the ice and there act as a lubricant between ice
and stone to help the ice flowing downwards.

Of course this applies only on ice that is currently above sea level.
Due to the huge ice pressure, the ground sinks up to 1 km. The ice
below sea level doesn't flow anywhere, until the ground pops up due to
isostacy in the next 10000 to 50000 years (about 1 cm/year).

The recent event you seem to refer in North America must have been a
situation in which a large area has been surrounded by mountains and a
huge lake formed inside it, with possible icebergs floating around. At
some point, the stones broke and a huge flood was created, making deep
scars into the geology. Most likely just a one off event, not a normal
mechanism.

An ice sheet sliding off into the sea is always a one-off event. They don't slide back up hill again.

The problem is that ice sheets would take a long time to melt in situ.

There are multiple examples of glaciers melting in situ.

Ice sheets are bigger and thicker than glaciers.

Melting a a mile or so thick layer of ice takes quite a while.

https://en.wikipedia.org/wiki/Terminal_moraine

dumping gravel at the edge of the glacier.This is not the same as
eskers https://en.wikipedia.org/wiki/Esker

We have both types in Finland.

But you haven't got an ice sheet.

I do not know what is your definition for ice sheet or continental
glacier see https://en.wikipedia.org/wiki/Ice_sheet

I was talking of the Fenno-Scandic ice sheet, which was a part of the
Weichsel glacier https://en.wikipedia.org/wiki/Weichselian_glaciation

The terminal moraine and eskers I referenced are remnants of the
Fenno-Scandic ice sheet.

There's a terminal morraine where I am at the moment - in Nijmegen in the Netherlands. It's a heap of rocks and dirt that collected here when the Rhine was a glacier, and melted here when the flowing ice got warm enough.

It built up over the hundred thousand-odd years that the Rhine was a glacier.

If an ice sheet had slid off here into the ocean (it didn't because there's no ocean handy), it would have slid off over the top of the accumulated rocks.

The existence of a terminal morraine is not evidence that an ice sheet didn't slide off over the area. The rocks that get into ice sheets can stay in the ice until the chunk of ice is well out to sea - as evidenced by the "accidentals" on the floor of the North Atlantic.

BTW, how was the Doggers bank formed ?
Click to expand...

Do your own googling.

https://en.wikipedia.org/wiki/Dogger_Bank

Apparently the likelist explanation is a morraine, but that says nothing about when the relevant glciers were flowing, and from where.

Anyway, look at the big picture. There was a huge amount of ice that
needed to be melted. Now the question is, what was the source of the
energy? Clearly it was the Sun.
Click to expand...

Originally.

From the end result (molten ice) it is irrelevant how that energy was
transferred from the Sun into the ice, directly by radiation or
indirectly by first warming air or water and then let it melt the ice.

With floating ice, the heat transfer is more effective (faster),
since it now occurs also from below. Anyway, the total energy needed
to melt a kilogram of ice is the same (333 kJ/kg), regardless of
heating method.
Click to expand...

The oceans store a lot of heat, and the process of melting floating ice bergs taps that - the sea water that gets cooled around the ice berg sinks (if it warmer than 4C, and ocean water tends to be warmer than that) and pushes up warmer water from below. The fresh water coming off the ice-berg messes with this a bit, but it takes a lot bigger mass of warmish water to melt an iceberg than the volume of fresh water produced.

My original question was, how much warmer the air would have been, if
not that much solar energy would have been required to melt the pesky
glacial ice?
Click to expand...

It's probably the wrong question - as I said ocean water stores a lot of heat, and the temperature deep ocean water isn't tighly coupled the temperature of the air above it (or its CO2 content for that matter). Time constants of 800 years show up for both.

--
Bill Sloman, Sydney
 
On Mon, 24 Jun 2019 07:35:54 -0700 (PDT), Bill Sloman
<bill.sloman@ieee.org> wrote:

On Monday, June 24, 2019 at 2:35:28 PM UTC+2, upsid...@downunder.com wrote:
On Mon, 24 Jun 2019 04:06:37 -0700 (PDT), Bill Sloman
bill.sloman@ieee.org> wrote:

On Sunday, June 23, 2019 at 8:05:25 PM UTC+2, upsid...@downunder.com wrote:
On Sun, 23 Jun 2019 08:16:42 -0700 (PDT), Bill Sloman
bill.sloman@ieee.org> wrote:

On Friday, June 21, 2019 at 4:07:49 PM UTC+2, upsid...@downunder.com wrote:
On Fri, 21 Jun 2019 05:28:55 -0700 (PDT), Bill Sloman
bill.sloman@ieee.org> wrote:

Thus week's Proceedings of the (US) National Academy of Science had a slightly worrying paper on the economics of the disintegration of the Greenland ice sheet

https://www.pnas.org/content/116/25/12261.abstract?etoc

The worrying part is that economists who wrote it don't seem to have got the idea that the ice sheet could suddenly start sliding off in large chunks, as ice sheets have been known to do in the not all-that-geological past, like at the end of the most recent ice age.

To help the ice to flow, first liquid water is needed e.g. in ice
lakes during the summer, gravasses are needed so that the water will
suddenly flow under the ice and there act as a lubricant between ice
and stone to help the ice flowing downwards.

Of course this applies only on ice that is currently above sea level.
Due to the huge ice pressure, the ground sinks up to 1 km. The ice
below sea level doesn't flow anywhere, until the ground pops up due to
isostacy in the next 10000 to 50000 years (about 1 cm/year).

The recent event you seem to refer in North America must have been a
situation in which a large area has been surrounded by mountains and a
huge lake formed inside it, with possible icebergs floating around. At
some point, the stones broke and a huge flood was created, making deep
scars into the geology. Most likely just a one off event, not a normal
mechanism.

An ice sheet sliding off into the sea is always a one-off event. They don't slide back up hill again.

The problem is that ice sheets would take a long time to melt in situ.

There are multiple examples of glaciers melting in situ.

Ice sheets are bigger and thicker than glaciers.

Melting a a mile or so thick layer of ice takes quite a while.

https://en.wikipedia.org/wiki/Terminal_moraine

dumping gravel at the edge of the glacier.This is not the same as
eskers https://en.wikipedia.org/wiki/Esker

We have both types in Finland.

But you haven't got an ice sheet.

I do not know what is your definition for ice sheet or continental
glacier see https://en.wikipedia.org/wiki/Ice_sheet

I was talking of the Fenno-Scandic ice sheet, which was a part of the
Weichsel glacier https://en.wikipedia.org/wiki/Weichselian_glaciation

The terminal moraine and eskers I referenced are remnants of the
Fenno-Scandic ice sheet.

There's a terminal morraine where I am at the moment - in Nijmegen in the Netherlands. It's a heap of rocks and dirt that collected here when the Rhine was a glacier, and melted here when the flowing ice got warm enough.

It built up over the hundred thousand-odd years that the Rhine was a glacier.

If an ice sheet had slid off here into the ocean (it didn't because there's no ocean handy), it would have slid off over the top of the accumulated rocks.

The existence of a terminal morraine is not evidence that an ice sheet didn't slide off over the area. The rocks that get into ice sheets can stay in the ice until the chunk of ice is well out to sea - as evidenced by the "accidentals" on the floor of the North Atlantic.
Click to expand...

BTW, how was the Doggers bank formed ?

Anyway, look at the big picture. There was a huge amount of ice that
needed to be melted. Now the question is, what was the source of the
energy ? Clearly it was the Sun.

From the end result (molten ice) it is irrelevant how that energy was
transferred from the Sun into the ice, directly by radiation or
indirectly by first warming air or water and then let it melt the ice.

With floating ice, the heat transfer is more effective (faster),
since it now occurs also from below. Anyway, the total energy needed
to melt a kilogram of ice is the same (333 kJ/kg), regardless of
heating method.

My original question was, how much warmer the air would have been, if
not that much solar energy would have been required to melt the pesky
glacial ice ?
 
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