Signs of Arctic climate change

And when I say 'Arctic', I of course automatically imply 'Northern Hemisphere'. You know, the place where most of the world's agriculture is based.

One thing I have noticed this melting season, is how high pressure areas persistently remained over Greenland (causing, for instance, the decrease in reflectivity all over the ice sheet):

But what I didn't know, is that this is something that apparently started in 2007, having all kinds of consequences for Northern Hemisphere weather patterns. This is again from the Dosbat blog, where Chris Reynolds is on a roll:

Last year I posted "Summer Daze." In that post I detailed a new pattern of atmospheric behaviour centred on high pressure over Greenland, this pattern is new since 2007, and as I showed is a robust change since the 1950s in NCEP/NCAR data.

Well, it's happened again this year...

The pattern I showed consisted of strongly anomalous high pressure over Greenland surrounded by a ring of tendency to low pressure anomalies. I used NCEP/NCAR monthly analysis to examine it, source data. As with all atmospheric patterns, in some years it was stronger than others, and there was interannual variability in the details of the pattern, but taking a succession of years it was seen to be a common pattern. The robustness of this pattern and its unusual nature is highlighted by taking the average pressure fields for batches of years and subtracting one batch from another. The pattern of the post 2007 period survives this method, still being present for any 5 year period subtracted from the period 2007 to 2011. As could be seen from the original Summer Daze post, this process shows that the pattern doesn't occur regularly in the past in the way it has done since 2007.

This year the pattern is textbook perfect.

Chris goes on to explain what this means for UK summer weather and wonders if perhaps, possibly, maybe, this persistent blocking pattern could have something to do with disappearing Arctic sea ice. Read the whole article here.

I'm sure Chris will have more to say about this, and scientific experts won't be slow to follow.

Comments

[Lennartvdl]

Mauri,

Thanks for the response and the link to Pfeffer (2011); very nice overview. To me as a lay person it gives the impression that ice sheet behaviour is not yet well enough understood to make confident projections for 2100 and further.

So I'm wondering to what extent Hansen and Sato have a point when they say:
"The kinematic constraint may have relevance to the Greenland ice sheet, although the assumptions of Pfeffer at al. (2008) are questionable even for Greenland. They assume that ice streams this century will disgorge ice no faster than the fastest rate observed in recent decades. That assumption is dubious, given the huge climate change that will occur under BAU scenarios, which have a positive (warming) climate forcing that is increasing at a rate dwarfing any known natural forcing. BAU scenarios lead to CO2 levels higher than any since 32 My ago, when Antarctica glaciated. By mid-century most of Greenland would be experiencing summer melting in a longer melt season. Also some Greenland ice stream outlets are in valleys with bedrock below sea level. As the terminus of an ice stream retreats inland, glacier sidewalls can collapse, creating a wider pathway for disgorging ice."

Are they simply wrong, or could they be right that ice streams could disgorge ice faster than the fastest rate observed in recent decades?

You say:
"To date all of the changes we have seen in our glaciers and ice sheets fit our understanding of their dynamics. The timing of the onset of changes has been faster and more widespread than any of us anticipated, but the actual dynamics fit very well."

So even if the dynamics so far have been understood, how certain can we be that changes this century (and later) won't be faster than Pfeffer et al (2008) think possible?

And what about those processes that Pfeffer (2011) says are not yet well enough understood to model them? If Arctic sea ice is able to surprise the scientific models as it is doing now, why not the ice sheets as well? Especially since apparently many relevant feedbacks/processes have not been incorporated in the sea ice models, nor in other climate models.

To me this seems not only relevant for adaptation, but even more so for mitigation. A rate of SLR of say 1-2 m/century or 3-4 m/century could make a big difference for adaptation chances, so would be also very relevant for mitigation decisions. Pfeffer (2011) speaks about the 'fat tail' of the PDF of potential SLR and the difficulty in estimating the probabilities. So I suppose for now we'll have to be satisfied with expert judgement.

So as an expert, how serious do you think the risk is of rates of SLR of 4-5 m/century in coming centuries, as Hansen & Sato seem to think possible/probable under BAU?

Thanks for any further reply,

Lennart van der Linde

[Lennartvdl]

Seke Rob,

Tell Hansen and Schellnhuber not to worry any longer, since they seem to think a runaway 'Venus Effect' on Earth is not entirely impossible. Or maybe they changed their minds recently?

[Climate Changes]

Well, 40 years ago we couldn't begin to imagine that the Arctic Ice would be gone by 20..? :P

[Twemoran]

The questions I have relating to the GIS are related to possible alteration of the topography by recent glacial changes.

Are any fjords presently being widened, straightened or deepened by glacial outflow. and is this a problem that we would expect to increase in the near term.

My understanding is that the surfaces on which the ice is presently grounded may be either bedrock, or a rock/gravel surface that might be much more easily cut through than bedrock. Are there any studies that indicate which surfaces are more prevalent, or whether there are areas that could be breached allowing oceanic waters to penetrate into the below sea level regions far inland from the present shores.

Thanks
Terry

[Lennartvdl]

A paper from January this year on the (remote) possibility of the runaway 'Venus Syndrome':
http://arxiv.org/abs/1201.1593

As noted Hansen and Schellnhuber have also speculated on this possibility and seem to think it's not even as remote as this paper concludes.

[Lennartvdl]

Hansen wrote on the 'Venus Syndrome' in his Storms of my Grandchildren' and spoke about it in this talk in 2008 (pp.22-24):
http://www.columbia.edu/~jeh1/2008/AGUBjerknes_20081217.pdf

Schellnhuber talked about this risk in his talk in Oxford in 2009 (pp.16-18):
http://www.eci.ox.ac.uk/4degrees/ppt/1-1schellnhuber.pdf

For audio/video of this talk see:
http://www.eci.ox.ac.uk/4degrees/programme.php

Would be nice if they wrote a paper about it.

[Climate Changes]

@Lennartvdl
That's some great stuff. :)

"How much a forcing must be maintained to cause rgw? Our models blow up before the oceans boil, but it suggests that perhaps runaway conditions could occur with added forcing as small as 10/20 W/m2."

I'd guess that humans would've d-evolved, moved to another planet or gone extinct before the water would boil but Hansen's right in saying that we should be thinking of runaway as a possibility, if not for future generations/life.

[Twemoran]

OT
There appears to be water showing in the most inland range of possibly the NordenSkold or Hisinger Glacier, r02c03, most visible with aqua.

Seems too far from any other open areas, and I can't seem to get arctic.io's split zoom to load right know so can't be sure.

Terry

[Alice]

present and for a long time, and water is still here, I'd not worry on that front for a longer while... Maybe the next incarnation of HSS will.
http://www.wholesalesneakershop.com/

[Otto Lehikoinen]

http://obuoy.datatransport.org/monitor#buoy6/weather looks like buoy#6 has hit the waterline, or maybe it's been picked up too, does someone know?

[Otto Lehikoinen]

Oops, I apparently hit the midnight image, the buoy is still on ice.

[Otto Lehikoinen]

http://obuoy.datatransport.org/monitor#buoy8/webcam is far out above Siberia.

[Derek]

A nice sea level map.

http://www.bbc.co.uk/news/science-environment-19702450