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Climate Change and Sea Level.

post #1 of 10
Thread Starter 

In my lecture notes it says

Schneider claims in his study that sea level change is the most dramatic and visible

effect of global warming.

Factors effecting present day sea level change include

1) Thermal expansion of the oceans

2)Total volume of water increasing due to melting of mountain glaciers

then it adds that water additions from large ice sheets is more complicated? Does anyone have any idea why this is? Or any science behind the complexity.


I know that the contribution to sea level rise from the melting of ice sheets is minimal, because most of the ice is underwater, but what about the ice sheet on greenland and antarctica? i have a feeling im missing something simple here?


Also do people agree with schnieder that sealevel change is the most dramatic effect of climate change in the 21st century?


 EDIT: Iv just thourght is it something to with increasing percipitation in anatarctica, and changes in the hydrological cycle?



Edited by snixx - Mon, 05 Jan 2009 10:00:58 GMT

Edited by snixx - Mon, 05 Jan 2009 10:07:23 GMT
post #2 of 10

ice sheets are floating so dont directly contribute to sea level rise, but they hold back glaciers which do. the movement of glaciers is very complicated with the back pressure from the coastal ice sheet only ine factor, and they are learningmore all the time. also, there is the 'albedo positive feedback' effect, where as floating ice melts, more open water is exposed to summer sun, and as it is a lot darker (lower albedo) it absorbs more energy as heat rather than reflecting it.


another complicating factor for sea level rise is dams, we are not seeing quite all the 'real' rise as more water is being stored especially in big dams in places like china.

post #3 of 10
Thread Starter 

That makes sense. I Knew about the albedo effect, which is pretty concerning as it could mean the ice melting is going to speed up. I never thorght about the mega damms, but now i do that also makes sense, as that would alter the hydrological cycle, as more water would be in storage. Does anyone know how much the hydrological cycle is altered through damming, locally and globaly? Have there been any studies done on this?

post #4 of 10
Thread Starter 

on second thourghts isnt the dammed water just making up for all the draining of water done so the land that was previously marsh / water logged can be used for agriculture and can be built on?

post #5 of 10


Edited by gerda - Mon, 05 Jan 2009 15:04:15 GMT
post #6 of 10

a quick google found what i think is the article i read about dams;

Dams mask sea level rise
March 13, 2008


....The Taiwanese researchers used the International Commission on Large Dams' World Register of Dams to calculate the volume of water — some 10,800 cubic kilometers (2,600 cubic miles) — that is stored in more than 29,000 reservoirs worldwide. They then used data on when dams were built to calculate annual sea level rise had water not been retained by dams. They found that sea levels would have climbed by an "essentially constant" 2.46 millimeters per year over the past eight decades...



good point about the drainage, i can only assume it is a much smaller effect, as water levels in wetlands are generally pretty shallow. there would be speeding up of water transfer over a season rather than a big long term reduction of water held in the bogs.

post #7 of 10

Aren't the Greenland and Antarctic ice sheets land-based?  I'm pretty sure that they'll add to the sea level rise significantly as they melt.


The effects of sea level rise are pretty dramatic, but then again at the moment the rise is also happening fairly slowly.  In future decades when the rise is happening more quickly perhaps it will be the most dramatic and visible effect, but I don't really think that's the case right now.  Probably the most visible current effect is the melting of Arctic sea ice, in my opinion.  The Northwest Passage opened, and the Arctic could be ice free in the summer within 5 years.  That's pretty dramatic.

post #8 of 10

The partial pressure of saturated water vapour increases by 0.8 mm Hg from 14 to 15 C.  Multiplying the fractional change in pressure by the mass of the atmosphere, the extra storage with a 1 C rise is 5.4 E 15 kg and the corresponding sea level change would be 15 mm.  The atmosphere is not staturated, so the actual number will be less.  The sea level rise is reduced because a warmer atmosphere holds more water.

post #9 of 10

how embarrasing! yes of course, i was talking about ice shelves! sorry snixx.

you lecture notes are following the ipcc i reckon, who didnt have much evidence of big ice sheets getting unstable, and as you say, increased precitipation in east antarctica especially

but recent measurements of thickness (by satellite) and speed (by men on sleds with flags brrr!) are showing a much more volatile picture, ice streams speeding and slowing on a timescale of days (probably related to movement of water between various lakes at the base of the ice).



post #10 of 10
Thread Starter 

Thankyou everyone for your answers, there very interesting. Im taking it the satellite data can be found on NOAA, im looking forwards to taking a look, but as moving back to uni today, it will have to wait until iv finished packing. Plus iv got the more boring human geography modules to get to grips with first!


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