7 replies to this topic

[Saintpeter]

Just been watching frozen planet and had an apiphony. If water levels are rising due to ice caps melting, where did the wather that makes up the ice caps come from? Or has earth gained a few trillion litres extra water since the last ice age.

[BornFromTheVoid]

The ice caps would have developed like glaciers. Essentially, the amount of snowfall has to exceed the summer melt, and over-time it builds up and compacts, becoming ice.
When this happens, the sea levels drop. About 12,000 years ago, sea levels were around 40m below todays levels.
In the end, all the water comes from the oceans. Oceans levels will drop when the ice spreads, and rise back up when the ice melts. No extra water needs to be added to the system.

[paul tall]

The sea is in the same place now as it was when I was a child 30 years ago. No sea level rise in that time then, no problem. Not scientific I know, but it'll do for me.

[Gray-Wolf]

If we look to when the Earth had no ice caps last time we can see sea levels up to 60 metres higher than todays.

Any losses from the east Antarctic ice sheet are an issue that would be better if we could avoid them!

Sadly the warm water causing the issues down the peninsula through to Pine Island seem destined to hit the Ross ice Embayment and any losses from this shelf could lead to the total collapse of it as the weight of glaciers behind snowplough the remaining shelf out over open water before the ice can gain purchase and freeze to the sea bed below.

[leicesternosnowzone]

The water that makes up the continental ice sheets was intially in the oceans, as the ice sheet melts (as is happening in Greenland and in some parts of Antarctica today) the water returns to the oceans causing sea levels to rise. During the last deglaciation sea levels are thought to have been 6-7m higher than today- to give some idea thats aprroximately equivalent to the whole Greenland ice sheet melting and would cause major problems for the majority of coastal cities- London, New York, Amsterdam and a lot more. I think most research suggests that a catastrophic melting of the East Antarctic ice sheet is currently unlikely but as Gray-wolf says that would be at least an additional 60m of sea level rise. The last time Earth had no ice caps was 35Myrs ago (and IMO we are currently still quite a long way away from that situation happening again) and most estimates suggest sea level was 100-200m higher during that period- the changing volume of ocean basins also played a role in this so this scale of sea level rise couldn't be reached simply by melting the water stored in ice sheets.

Sea level and ice sheets both respond more slowly to atmospheric changes than surface temperatures do i.e ice sheet melting lags behind temperature changes, hence paul tall's comment about the sea being in the same place as 30 years ago. I think tide gauges show sea level rises of approx 20cm since 1900, this doesn't sound like much but countries such as Bangladesh and the Maldives have already been affected.

[Waterspout]

Gray-Wolf, on 09 December 2011 - 08:39 , said:

If we look to when the Earth had no ice caps last time we can see sea levels up to 60 metres higher than todays.

Any losses from the east Antarctic ice sheet are an issue that would be better if we could avoid them!

Sadly the warm water causing the issues down the peninsula through to Pine Island seem destined to hit the Ross ice Embayment and any losses from this shelf could lead to the total collapse of it as the weight of glaciers behind snowplough the remaining shelf out over open water before the ice can gain purchase and freeze to the sea bed below.

It's a good job then that the Antarctic has not warmed at all in the past 50 years, if anything cooled slightly. The natural calving you talk about is quite a normal process, and any year on year changes that do occur are down to changes in Ocean currents which happen on a local level over decadal periods, and is also quite normal.

There is no science I know of which is warning of a " total collapse" of any Ice Shelves in the Antarctic. In fact mainstream science, and infact BBC TV programmes,tend to steer clear of the opposites trends at our Southern Polar Icecap as they don't exactly fit in with the concenus opinion concerning the Warming that did occur from 1950-2000, globally.

[laserguy]

Waterspout, on 13 December 2011 - 15:39 , said:

. The natural calving you talk about is quite a normal process.....

It always amuses me to see those global warming propaganda clips on teevee where they show huge slabs of ice breaking off and they make out as if it's melting. A five year-old can see that's not the case at all. Such clips are inevitably followed by brief footage (almost like a subliminal message) of a cooling tower belching out a vast cloud of water vapour,with the clear intention of having the great unwashed believe that the cloud is CO2 and that there must therefore be a link to that non-event,before moving on to the main news of the day like Cheryl Cole's new puppy being treated to a massage or somesuch....

[Gray-Wolf]

I'm sorry Waterspout but you appear to be looking at one russian station (as guided by the denialists?) and not the evidence on the ground? What of Larson A and B? what of Wilkins? by next year I will add 'What of Pine Island' . None of these are merely 'Calving', they are the loss of an ice shelf ( with the consequences we measure for the glaciers the shelf used to hold firm behind them).

Wake up to the reality of what occurred to the peninsula that thrusts itself out beyond the influence of the Circumpolar wind/current. If our abuse of fridge coolants have caused issues with the stratospheric ozone then it will impact the troposphere below. If you doubt this then 'fear not' the warm water has now ducked under this 'gate' into the Antarctic (as the loss of Wilkins showed) . We are now down to the P.I.G. with Ross next in line. When we lose Ross we'll pick up this conversation on the lack of 'warming' in Antarctica?