World's Longest Canyon Discoverd Under Greenland's Ice

[pikaia]

A canyon running for at least 460 miles (750 kilometers) has been discovered under Greenland's ice. This could influence the melting of the ice. "...the newly discovered canyon could boost the breakup of one of the coastline's briskly retreating glaciers."

http://www.livescience.com/39289-greenland-longest-canyon-discovered.html

[Espen]

Yes there will proably be a few surprises when more local maps are made from this new knowledge.

[Stephen]

Of course if all the ice melts then the sea level around Greenland will drop by more than 100 metres because of the fingerprint effect.  So everything changes.

[sidd]

Here is a link to Greenland bedrock maps based on the new Bamber data

http://membrane.com/sidd/greenland-2013/

You can see the canyon and the troughs feeding Jacobshawn.

sidd

[sidd]

Also i believe the fingerprint effect is only a few centimetres if all the ice melted on Greenland. Speaking of that, see my previous post.

sidd

[Stephen]

Also i believe the fingerprint effect is only a few centimetres if all the ice melted on Greenland. Speaking of that, see my previous post.

sidd

Recent articles (new scientist magazine in particular) lead me to believe that the sea level at the Greenland coast would drop by more than 100 metres and up to 3 metres at the Scotland coast.  So I'd be interested to know where you get that "few centimetres" value from.

[OldLeatherneck]

Recent articles (new scientist magazine in particular) lead me to believe that the sea level at the Greenland coast would drop by more than 100 metres ..................

How much of that 100 meter drop would be due to the isostatic rebound of the Greenland land mass and how much of it would be due to the loss of the gravitational effect the current ice sheet has on sea  levels surrounding Greenland?

Also,  if sea levels surrounding Greenland drop 100 meters, how much will that affect Global Mean Sea Levels??

[Lennart van der Linde]

A new paper by Marzeion & Levermann estimates at most 8 meters of lowering around Greenland and Antarctica for 3 degrees C of warming and about 7 meters of mean global sea level rise, if I read figure 1 in their supplementary information correctly:
http://iopscience.iop.org/1748-9326/9/3/034001/media/erl491558suppdata.pdf

The full article is about the threat of SLR to world cultural heritage:
http://iopscience.iop.org/1748-9326/9/3/034001/article

It seems still a quite conservative estimate, compared to the risks that Rohling et al 2013 see:
http://www.nature.com/srep/2013/131212/srep03461/pdf/srep03461.pdf

They think at least 9 meters of global mean SLR in the long run is probably almost inevitable by now.

[sidd]

Re: fingerprint effect

I was wrong, please see my post

https://forum.arctic-sea-ice.net/index.php/topic,526.msg21364/topicseen.html#msg21364

sidd

[Stephen]

Re: fingerprint effect

I was wrong, please see my post

https://forum.arctic-sea-ice.net/index.php/topic,526.msg21364/topicseen.html#msg21364

sidd

Thanks for the response.  Seems unfair that those North Atlantic nations responsible for increased GHG will mostly escape this particular effect.

[Lennart van der Linde]

New Scientist does indeed quote Mitrovica as saying sea level may fall 100 meters at the Greenland coast:
http://www.newscientist.com/article/mg21829151.900-where-melting-ice-means-retreating-seas.html

Did they misquote him, or am I missing something?

[crandles]

missing something? Timescale perhaps

from
http://en.wikipedia.org/wiki/Post-glacial_rebound

Studies have shown that the uplift has taken place in two distinct stages. The initial uplift following deglaciation was almost immediate due to the elastic response of the crust as the ice load was removed. After this elastic phase, uplift proceeded by slow viscous flow so the rate of uplift decreased exponentially after that. Today, typical uplift rates are of the order of 1 cm/year or less. In northern Europe, this is clearly shown by the GPS data obtained by the BIFROST GPS network.[1] Studies suggest that rebound will continue for about at least another 10,000 years. The total uplift from the end of deglaciation depends on the local ice load and could be several hundred metres near the centre of rebound.

[Lennart van der Linde]

No, GIA is not the same as this specific gravitational effect. Here a colleague of Mitrovica says that melting of WAIS would also lower sea level there by about 100 meters:
http://news.harvard.edu/gazette/story/2010/12/ice-sheet-in-peril-gravity-to-rescue/

It's a negative feedback, but unclear how strong. And other info seems to indicate the lowering will be about the opposite of global mean rise.

[Shared Humanity]

Re: fingerprint effect

I was wrong, please see my post

https://forum.arctic-sea-ice.net/index.php/topic,526.msg21364/topicseen.html#msg21364

sidd

Thanks for the response.  Seems unfair that those North Atlantic nations responsible for increased GHG will mostly escape this particular effect.

Not entirely. U.S. Gulf Coast and Atlantic Coast (particularly the mid Atlantic) are going to see higher than average SLR.

Miami's fate is sealed due to approaching SLR, most of southeast Florida actually, which I believe will be abandoned by the end of this century.

http://www.rollingstone.com/politics/news/why-the-city-of-miami-is-doomed-to-drown-20130620

Edit: I actually believe Miami will be abandoned well before the end of the century but I did not want to sound like an alarmist.