Posted by Eeyore on December 18, 2008, 2:11 pm
patrick.earthcharterfoundation@gmail.com wrote:
> Temperatures in the Arctic are rising much faster than elsewhere on
> Earth resulting from a shift in global climate patterns and the sea
> ice on the North Pole melting much quicker than expected.
Irrelevant. Floating sea ice doesn't affect sea level when it nelts.
Graham
Posted by harry on December 19, 2008, 2:25 pm
On Dec 19, 5:51 am, david.willi...@bayman.org (David Williams) wrote:
> -> Irrelevant. Floating sea ice doesn't affect sea level when it nelts.
> -> Graham
> It does. Seawater is salty. Salty water is denser than fresh water. An
> iceberg displaces an amount of seawater equal to its own mass. When it
> melts, the volume of freshwater it produces is greater than the
> previously displaced volume of seawater. So the total volume increases,
> causing sea level to rise.
> Ice floating on a freshwater lake would not cause a rise in level. But
> oceans are not lakes.
> dow
But as the ice melts, it contracts. Which is why it was floating in
the first place.
And why pipes burst when they freeze.
Another factor is that as the glaciers disappear, the land rises as it
is relieved of their wieght. Adjacent land sinks. This is
happening in the UK right now. The Northern bit is rising & the
Southern bit is sinking. This due to the glaciers from the last ice
agemelting.
Posted by Tim Jackson on December 19, 2008, 5:35 pm
harry wrote:
> On Dec 19, 5:51 am, david.willi...@bayman.org (David Williams) wrote:
>> -> Irrelevant. Floating sea ice doesn't affect sea level when it nelts.
>>
>> -> Graham
>>
>> It does. Seawater is salty. Salty water is denser than fresh water. An
>> iceberg displaces an amount of seawater equal to its own mass. When it
>> melts, the volume of freshwater it produces is greater than the
>> previously displaced volume of seawater. So the total volume increases,
>> causing sea level to rise.
>>
>> Ice floating on a freshwater lake would not cause a rise in level. But
>> oceans are not lakes.
>>
>> dow
>
> But as the ice melts, it contracts. Which is why it was floating in
> the first place.
> And why pipes burst when they freeze.
> Another factor is that as the glaciers disappear, the land rises as it
> is relieved of their wieght. Adjacent land sinks. This is
> happening in the UK right now. The Northern bit is rising & the
> Southern bit is sinking. This due to the glaciers from the last ice
> agemelting.
The ice contracts but it still weighs the same and even after
contraction it still occupies slightly more volume than the same weight
of sea water simply because it is fresh water, and salt water is denser.
Yes I'm standing on a piece of formerly glaciated UK, in a glacial
valley. Yes the land is still rebounding from the last ice age. But no,
adjacent land doesn't sink, as such, although a solid mass might tilt a
bit. If you get off a boat it rises, and may pitch a little but the
adjacent boat doesn't sink. But this has little to do with the next
century's sea levels, the rising land may apparently lower sea level
locally and may displace a little sea, and so raise levels globally, but
most of it was above sea level anyway and it is a slooow process taking
tens of thousands of years. Remember how long ago the last ice age was?
Tim Jackson
Posted by harry on December 21, 2008, 3:37 pm
> harry wrote:
> > On Dec 19, 5:51 am, david.willi...@bayman.org (David Williams) wrote:
> >> -> Irrelevant. Floating sea ice doesn't affect sea level when it nelts.
> >> -> Graham
> >> It does. Seawater is salty. Salty water is denser than fresh water. An
> >> iceberg displaces an amount of seawater equal to its own mass. When it
> >> melts, the volume of freshwater it produces is greater than the
> >> previously displaced volume of seawater. So the total volume increases,
> >> causing sea level to rise.
> >> Ice floating on a freshwater lake would not cause a rise in level. But
> >> oceans are not lakes.
> >> dow
> > But as the ice melts, it contracts. Which is why it was floating in
> > the first place.
> > And why pipes burst when they freeze.
> > Another factor is that as the glaciers disappear, the land rises as it
> > is relieved of their wieght. Adjacent land sinks. This is
> > happening in the UK right now. The Northern bit is rising & the
> > Southern bit is sinking. This due to the glaciers from the last ice
> > agemelting.
> The ice contracts but it still weighs the same and even after
> contraction it still occupies slightly more volume than the same weight
> of sea water simply because it is fresh water, and salt water is denser.
> Yes I'm standing on a piece of formerly glaciated UK, in a glacial
> valley. Yes the land is still rebounding from the last ice age. But no,
> adjacent land doesn't sink, as such, although a solid mass might tilt a
> bit. If you get off a boat it rises, and may pitch a little but the
> adjacent boat doesn't sink. But this has little to do with the next
> century's sea levels, the rising land may apparently lower sea level
> locally and may displace a little sea, and so raise levels globally, but
> most of it was above sea level anyway and it is a slooow process taking
> tens of thousands of years. Remember how long ago the last ice age was?
> Tim Jackson
There is both salt water ice and fresh water ice.
Fresh water ice is from glaciers sliding into the sea where this
happens.
But the sea also freezes making salt water ice.
Posted by Tim Jackson on December 21, 2008, 5:32 pm
harry wrote:
>> harry wrote:
>
> There is both salt water ice and fresh water ice.
> Fresh water ice is from glaciers sliding into the sea where this
> happens.
> But the sea also freezes making salt water ice.
Sea ice is water crystallising from solution, and does not contain much
salt: much less than sea water. Such fractional crystallization is a
well known method of purifying liquids, as an alternative to distillation.
Tim
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> Earth resulting from a shift in global climate patterns and the sea
> ice on the North Pole melting much quicker than expected.