Naked Science Forum

Life Sciences => The Environment => Topic started by: thedoc on 30/12/2014 13:30:01

Title: Are the polar caps melting due to declining salt levels?
Post by: thedoc on 30/12/2014 13:30:01

Emile David Shaw asked the Naked Scientists:
   
I had a theory regarding the melting of the polar caps.

What if it had to do with the salt levels declining?
 
There is this drink or more like a concoction that I mix up every once in a while. It consists of any gas drink, like sprite or Est, with a touch of lemon and some Salt. Every time I sprinkle the salt  over the ice before adding the liquid and sometimes I leave it like that for some time, but one day I became fascinated with the reaction it caused with the ice. The ice didn't melt, even after I added the drink, the ice stuck together like glue and didn't even break apart for a few hours. Depends on how much salt I added.  

Sometimes even the most complex scientific equation adds up to something very simple and usually missed by the naked human eye. Science can't solve everything, sometimes we should just add some nature and let things evolve naturally instead of forcing science onto it.

What do you think?

Title: Re: Are the polar caps melting due to declining salt levels?
Post by: evan_au on 30/12/2014 16:51:57

The phenomenon is described here: http://en.wikipedia.org/wiki/Freezing-point_depression
It is used to clear ice off roads, in radiator anti-freeze, and was even used in early attempts at making ice-cream commercially.

As I understand it, when you add salt to an ice/water mixture, as the salt dissolves in the water, it absorbs energy from the environment - which depresses the freezing point of the water, and makes the ice colder than the typical -4C of a household freezer.

Quote from: Emile David Shaw

What if it had to do with the salt levels declining? [in the ice?]

The polar ice-caps consist of fresh water. On land or in icebergs it comes from compressed snow (fresh water). On the sea, it is frozen seawater; the freezing process excludes almost all salt (ie if you melted it, it would be drinkable fresh water).

So the salt is not being removed from the ice, because there was none there in the first place.

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What if it had to do with the salt levels declining? [in the ocean?]

Salt is not being removed from the oceans at any measurable rate - this would have a very visible effect on the carrying capacity of the world's ocean-going ships. Changes in salinity would also impact many species of ocean life.

The only place where salt is being sequestered in any significant amount is probably in the Dead Sea, which is cut off from the oceans, and its river inflow has been cut off for agriculture and drinking water. It takes these extreme desert conditions to remove salt from water.

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Sometimes even the most complex scientific equation adds up to something very simple

I am afraid that the trend in melting of the polar ice-caps is due to the increased temperatures we have experienced over the past century slowly seeping into the continental ice-masses, causing more of it to melt than to fall as snow (averaged over a 10 year period). These increased temperatures have also seeped into the bulk of the ocean, leading to reduced sea ice (again, averaged over a 10 year period).

So I think that the explanation really is quite simple: increased temperatures tend to melt ice.

Where it gets contentious is when the reduced ice cover is mentioned in the same context as the increase in atmospheric CO₂ over the past century. That association attacks the very foundation of our "Western" economic and societal values; these values had one upheaval during the industrial revolution, which delivered immense power into the hands of industrialists, and (more recently) another upheaval when cheap oil and electricity delivered similar power into the hands of John Doe & Jill Smith - but at the cost of further increases in  CO₂ emissions.

But the scientific truth of something is not determined by our societal values.
This is in contrast to a sociologist or an economist who would say that the truth of something is determined by our societal values.

Title: Re: Are the polar caps melting due to declining salt levels?
Post by: CliffordK on 30/12/2014 17:41:00

If more fresh water is added to the oceans (glacier melt), there may be changes in the salinity of the ocean, at least locally. 

On a global scale, this may be offset somewhat by all of the mined salt being added back into circulation.