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Frankd 1977

Neven,

A bit off topic, but congratulations for going from 91 followers to 131 followers in just 2 months. That is over a 40% increase!!!
A statistic to be proud of. You have created a place for people concerned about (and actively studying) arctic sea ice from novice to ret. climate scientist to get together and share what is on their minds. Well done sir!

Artful Dodger

Hi Neven,

I think the sentence:

"2012 is currently over 1 million and almost 600K km3 below the 2010 and 2011 minimums respectively."

should be amended to read "over 1 thousand and almost 600 km3 below".

Total Arctic sea ice volume was currently about 3,407 cubic km on Sep 3, 2012.

Cheers,
Lodger

Protege Cuajimalpa

Just to make a highlight, the 2012 average thickness is higher compared to 2010 and 2011, because as at page of PIOMAS tells: "While ice volume continued to decrease through August, the average ice thickness increased in August (Fig 3) as areas covered by thin ice became ice free leaving thicker ice behind."

Wipneus

600K km3

Now we are talking about it, it hurts a bit to the eye to read "600 Kelvin cubic-kilometer".

Neven

it hurts a bit to the eye to read "600 Kelvin cubic-kilometer"

Yes, that's pretty hot, eh? This classic mistake has now been fixed. Thanks, Lodger.

And thanks, Frankd 1977.

Artful Dodger

"Damn you, entropy!"

(learned that in 'thermogodamits' class ;^)
--
Cheers!
Lodger

Doomcomessoon

I just started to wonder how above average temperatures over the main ice cap effect the PIOMAS numbers compared to how it effect the SIA and SIE numbers. I would guess that PIOMAS numbers are more affected, but is there any real difference?

Also, during the next ten days it is predicted that the air temperatures, above much of what is left of the ice cap, will stay 5-10 degrees celsius above normal. Will that alone have a signifacant impact on any of the numbers, or is the sun and wind conditions much more important in September?

me.yahoo.com/a/nSjChi4X3vr8X3DRw93GkY1.cerja.8nvWk-

In response to Wipneus the use of multiple prefixes is an abomination and it would be much better if the standard SI practices were followed. However in this field the use of the km as the base unit seems unshakeable! For example the proper unit for reporting the area should be the Gm^2 (= million km^2) and for volume Gm^3 (=km^3).

Phil.

me.yahoo.com/a/nSjChi4X3vr8X3DRw93GkY1.cerja.8nvWk-

That should be Tm^2 of course. :-)

It makes the calculation of thickness really simple:
3 Tm^3/ 2.5 Tm^2 = 1.2 m

Phil.

Wipneus

hmmm, I would interpret Gm^2 as (Gm)^2

(because it works that way in 1 km^2 = 10^6 m^2)

me.yahoo.com/a/nSjChi4X3vr8X3DRw93GkY1.cerja.8nvWk-

That's because km^2 isn't correct SI usage, in SI the prefix is applied after the primary unit raised to the appropriate power. Therefore Gm^2 is correctly G(m^2). Remember that the prefix is shorthand for the associated powers of ten so Gm^2 represents 10^12 m^2.

Phil.

Wipneus

Dont think so.

From the site of "the Bureau International des Poids et Mesures" on SI prefixes:

The grouping formed by a prefix symbol attached to a unit symbol constitutes a new inseparable unit symbol (forming a multiple or submultiple of the unit concerned) that can be raised to a positive or negative power and that can be combined with other unit symbols to form compound unit symbols.

Examples: 2.3 cm3 = 2.3 (cm)3 = 2.3 (10–2 m)3 = 2.3 x 10–6 m3

http://www.bipm.org/en/si/si_brochure/chapter3/prefixes.html

So Gm is the inseparable unit and you cannot interpret Gm^2 as G(m^2)

Kevin O'Neill

Phil, Giga is the prefix for 1 billion (1E9); Mega is the prefix for 1 million (1E6).

To avoid the confusion over units and prefixes the best solution I've found is to express everything in scientific notation and base units. If writing a report I would state 2.4 km^2 as 2.4E6 m^2. This requires one more character to write, but eliminates any misunderstanding.

Of course any change makes direct comparison with past data (old charts, graphs, etc.) more difficult.

D

People screw up exponentiation and multiple dimensions problems in the metric system all the time.


2^2m =/= 2m^2

Anyway, when doing volumes and areas, I have even caught professional scientists in both physics and meteorology fields making weird mistakes repeatedly.

"Ten Square Kilometers," equaling "Ten kilometers times one kilometer," should be written 10km^2.

so:

10km^2 = 10km * 1km

or

10km^2 = 5km * 2km

etc.

However, in some contexts you are multiplying a known area by a scalar, such as tiles. Suppose you want to cover ten meters length using tiles of 1m^2 area, then it is written as:

10m^2 = 10 * 1m^2


Common mistake is squaring the scalar when it is already implied in the language:

"ten square kilometers" =/= 100km^2.

Unfortunately, the English language can be confusing and the context needs to be known in some situations.

1km^3 = (1e9)m^3

10km^3 = (1e10)m^3

A cube of length 2km on each edge is 8km^3, not 2km^3, which is a common mistake.

An extra "K" in shorthand for "multiply by another thousand," and/or an extra three zeros are also common mistake in metric, perhaps because people over-think when writing short-hand, and create redundant symbols.

Espen Olsen

D,

Nice having my elementary school arithmetic updated!!

D

Espen Olsen:

I know it's elementary school, but these are the most common mistakes I've seen in math involving units of measure.

LRC

Nothing really new in this report other a very interest 3D animation of PIOMAS.
http://www.climatecentral.org/news/arctic-has-lost-enough-ice-to-cover-canada-and-alaska-14971/

FrankD

With the mandatory incorrect attribution, LRC. The graph, of course, is not a "U. of Washington animation of sea ice volume readings from a computer model".

Andy, if you see this, you might want to put a caption on future iterations of that video, to avoid rancour about incorrect attribution - we had some angst here a little while back with Wipneus' PIOMAS graphs...plus, there's no reason you shouldn't get the credit for your own creative work.

IdiotTracker


"Damn you, entropy!"

I heard a rumor that that had happened. Unfortunately, Hell was destroyed by heat death soon after.

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