Everything you cited is in km^2; that is area; aka "extent"
This is not volume; aka km^3
Yes... the AREA of the sheet of ice covering the oceans is INCREASING (just slightly mind you)
However, the VOLUME of ice on the oceans is DECREASING (quite significantly)
I feel like we're missing some fundamentals.
Volume is a cubic dimension. Length x Width x Height
Extent is a square dimension. It is the Length x Width (AREA) of the largest side of an object.
http://hypertextbook.com/facts/2001/JuliaSherlis.shtml
lets calculate EXTENT
paper: 8.5*11 = 93.5 square inches (you called this cube)
block of wood: 6x6 = 36 square inches
The paper has more EXTENT
93.5/36 = 2.59
The paper has an EXTENT 2.59 times greater than the block of wood
Now lets calculate the volume in each product:
paper = 8.5*11*0.004 = 0.374 cubic inches
block of wood = 6*6*6 = 216 cubic inches
The block of wood has more VOLUME
216/0.374 = 577.5
The block of wood has a VOLUME 577.5 times greater than the paper
Which then brings us to the data from your links:
So the Northern Hemisphere is showing -6.9% EXTENT loss per decade and the Southern Hemisphere is showing a measly 1.2% EXTENT gain per decade.
Meanwhile...
If we refer back to our VOLUME chart:
We see October VOLUME was 17 in 1979 and is only 5 in 2012.
That's 70% loss of VOLUME in 33 years.
30% VOLUME loss per decade
In summary per decade:
30% VOLUME loss in all oceans
1.2 % AREA gain in southern hemisphere
6.9 % AREA loss in northern hemisphere
It seems quite cherry picked to focus on the 1.2% area gain in this context:
While the surface area (EXTENT) covered by ice is just slightly larger, in just the southern hemisphere, each decade... the THICKNESS (third dimension of volume) of the ice on the oceans is significantly less everywhere.
Further... the AREA loss in the northern hemisphere is greater than the AREA gain in the southern hemisphere. So as a whole... there is a net loss in VOLUME
AND AREA in the world's oceans.
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