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Apocalypse4Real

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Greenland Melt Impacts 2012
« on: March 02, 2013, 10:26:11 PM »
Thought I'd put in the link to Tedesco's November 30, 2012 paper in Greenland ice melt impacts during 2012

The Cryosphere Discuss., 6, 4939–4976, 2012
www.the-cryosphere-discuss.net/6/4939/2012/
doi:10.5194/tcd-6-4939-2012

Evidence and analysis of 2012 Greenland
records from spaceborne observations,
a regional climate model and reanalysis
data


M. Tedesco1, X. Fettweis2, T. Mote3, J. Wahr4, P. Alexander1,5, J. Box6, and
B. Wouters4,7
1The City College of New York, The City University of New York, New York, NY 10031, USA
2University of Liege, Liege, Belgium
3University of Georgia, Athens, GA 30602, USA
4Department of Physics and Cooperative Institute for Research in Environmental Sciences,
University of Colorado, Boulder, CO 80309, USA
5The Graduate Center of the City University of New York, New York, NY 10031, USA
6The Ohio State University, Columbus, OH, USA
7School of Geographical Sciences, University of Bristol, Bristol, UK
Received: 24 October 2012 – Accepted: 15 November 2012 – Published: 30 November 2012
Correspondence to: M. Tedesco (mtedesco@sci.ccny.cuny.edu)
Published by Copernicus Publications on behalf of the European Geosciences Union.

Abstract

A combined analysis of remote sensing observations, regional climate model (RCM)
outputs and reanalysis data over the Greenland ice sheet provides evidence that multiple
records were set during summer 2012. Melt extent was the largest in the satellite
era 5 (extending up to 97% of the ice sheet) and melting lasted up to  two months
longer than the 1979–2011 mean. Model results indicate that near surface temperature
was 3 standard deviations () above the 1958–2011 mean, while surface mass
balance was 3 below the mean and runoff was 3.9 above the mean over the same
period. Albedo, exposure of bare ice and surface mass balance also set new records,
10 as did the total mass balance with summer and annual mass changes of, respectively,
−627 Gt and −574 Gt, 2 below the 2003–2012 mean.
We identify persistent anticyclonic conditions over Greenland associated with
anomalies in the North Atlantic Oscillation (NAO), changes in surface conditions (e.g.
albedo) and pre-conditioning of surface properties from recent extreme melting as ma15
jor driving mechanisms for the 2012 records. Because of self-amplifying positive feedbacks,
less positive if not increasingly negative SMB will likely occur should large-scale
atmospheric circulation and induced surface characteristics observed over the past
decade persist. Since the general circulation models of the Coupled Model Intercomparison
Project Phase 5 (CMIP5) do not simulate the abnormal anticyclonic circulation
20 resulting from extremely negative NAO conditions as observed over recent years, contribution
to sea level rise projected under different warming scenarios will be underestimated
should the trend in NAO summer values continue.



Gray-Wolf

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Re: Greenland Melt Impacts 2012
« Reply #1 on: March 04, 2013, 03:33:03 PM »
It will be very interesting to see if the pressure anoms do hold up this year with the Arctic winter showing a differing synoptic this past winter?

Have we notched up to the next level or has some 'natural' augmentation begun to fall out of the forcing?

If we do see ac similar pressure anom to those of recent years I feel it will be safe to say that it is the Arctic Amplification driving it and ,if so we must brace ourselves for a collapse in the G.I.S. albedo and the emergence of a short span doubling of mass loss from the ice sheet?

It will be interesting to see if we suffer another year with periods of extreme surface melt (further extensive surface melt up to the 97% we saw last year) and how the likes of WUWT will deal with the recurrance (having pinned their colours to a 160 odd year cycle for such events)?
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JackTaylor

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Re: Greenland Melt Impacts 2012
« Reply #2 on: April 03, 2013, 11:26:12 PM »
http://www.livescience.com/28399-clouds-greenland-ice-melt.html

has an article about an article in the journal Nature (pay walled)

"The culprit behind the record-shattering level of ice melting in Greenland in 2012 may have been low, thin clouds, new research suggests."

StuartC

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Re: Greenland Melt Impacts 2012
« Reply #3 on: April 03, 2013, 11:52:08 PM »
http://www.livescience.com/28399-clouds-greenland-ice-melt.html

has an article about an article in the journal Nature (pay walled)

"The culprit behind the record-shattering level of ice melting in Greenland in 2012 may have been low, thin clouds, new research suggests."

Climate Central also has an article about this paper.  Michael Lemonick has interviewed lead author Ralf Bennartz, an atmospheric scientist at the University of Wisconsin:

Bennartz and his colleagues can’t say at this point whether last summer’s cloudiness portends a trend. “The Arctic tends to be a cloudy place,” said Julienne Strove, of the National Center for Atmospheric Research, an expert on Arctic ice, in an interview, “and last summer was cloudier in general as you had several storms enter the Arctic.” In theory, clouds could be on the increase, as warmer temperatures force more water to evaporate from the oceans.

 “If those clouds had not been around there would not have been a melt event,” Bennartz said. “If they had been thicker, there also would not have been a melt event like the one we saw. What we do not know is what role clouds are going to play in the future."

The instruments he and his colleagues used to study clouds have only been in place for three years, which is too short a time to detect any sort of trend. Warming temperatures alone, however, would likely increase melting over the rest of the century even without significant increases in cloud cover.


Then he goes on to something that may be of even more significance to us here:

The new study raises the question of whether clouds played a role, not only in the melting of Greenland, but also in last summer’s record melting of sea ice in the Arctic Ocean.

I don't think I've seen the role cloud cover might play in melting sea ice mentioned before - can anyone fill us in about this?

http://www.climatecentral.org/news/clouds-helped-cause-greenlands-record-melting-last-summer-15824
« Last Edit: April 04, 2013, 12:03:59 AM by StuartC »
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crandles

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Re: Greenland Melt Impacts 2012
« Reply #4 on: April 04, 2013, 05:51:33 AM »

The new study raises the question of whether clouds played a role, not only in the melting of Greenland, but also in last summer’s record melting of sea ice in the Arctic Ocean.

I don't think I've seen the role cloud cover might play in melting sea ice mentioned before - can anyone fill us in about this?

http://www.climatecentral.org/news/clouds-helped-cause-greenlands-record-melting-last-summer-15824

Here is a brief mention on Realclimate (23 Jan 13):

Quote
the extremely warm summer of 2012 clearly involved anomalous weather conditions — a particular pattern of pressure anomalies over the northern high latitudes (e.g. Tedesco et al. (2012)) that may also partly account for the exceptional low sea ice cover that year. The 2012 event, however, gives us a flavor of what the future is likely to bring. It will be very interesting to watch the satellite imagery over Greenland in the next decade and beyond.

http://www.realclimate.org/index.php/archives/2013/01/the-greenland-melt/

Tedesco et al 2012:
http://www.the-cryosphere-discuss.net/6/4939/2012/tcd-6-4939-2012.html

(I've only read the abstract linked. The 37 page paper (18MB freely linked from abstract ref above) may take a bit longer to read and digest to check for relevance.)

Edit: actually all three occurrences of the word "sea" are followed by level so there doesn't appear any mention of sea ice. So I am not sure how or from where the "partly account for the exceptional low sea ice cover that year" comes. Possibly a paper that wasn't published at that stage? Possible the paywalled Bennartz you are referring to?
« Last Edit: April 04, 2013, 06:11:43 AM by crandles »

crandles

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Re: Greenland Melt Impacts 2012
« Reply #5 on: April 04, 2013, 06:48:10 AM »


Not identical but worryingly similar to Fig 10 of Tedesco linked above? Fig 10 is JJA whereas above image is JFM; does that matter?
« Last Edit: April 04, 2013, 01:56:24 PM by crandles »

slow wing

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Re: Greenland Melt Impacts 2012
« Reply #6 on: April 04, 2013, 10:59:26 AM »
Crandles, the image isn't showing for me.

dorlomin

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Re: Greenland Melt Impacts 2012
« Reply #7 on: April 04, 2013, 01:38:32 PM »
Surface mass balance model intercomparison for the Greenland ice sheet


Quote
Abstract. A number of high resolution reconstructions of the surface mass balance (SMB) of the Greenland ice sheet (GrIS) have been produced using global re-analyses data extending back to 1958. These reconstructions have been used in a variety of applications but little is known about their consistency with each other and the impact of the downscaling method on the result. Here, we compare four reconstructions for the period 1960–2008 to assess the consistency in regional, seasonal and integrated SMB components. Total SMB estimates for the GrIS are in agreement within 34% of the four model average when a common ice sheet mask is used. When models' native land/ice/sea masks are used this spread increases to 57%. Variation in the spread of components of SMB from their mean: runoff 42% (29% native masks), precipitation 20% (24% native masks), melt 38% (74% native masks), refreeze 83% (142% native masks) show, with the exception of refreeze, a similar level of agreement once a common mask is used. Previously noted differences in the models' estimates are partially explained by ice sheet mask differences. Regionally there is less agreement, suggesting spatially compensating errors improve the integrated estimates.

Modelled SMB estimates are compared with in situ observations from the accumulation and ablation areas. Agreement is higher in the accumulation area than the ablation area suggesting relatively high uncertainty in the estimation of ablation processes. Since the mid-1990s each model estimates a decreasing annual SMB. A similar period of decreasing SMB is also estimated for the period 1960–1972. The earlier decrease is due to reduced precipitation with runoff remaining unchanged, however, the recent decrease is associated with increased precipitation, now more than compensated for by increased melt driven runoff. Additionally, in three of the four models the equilibrium line altitude has risen since the mid-1990s, reducing the accumulation area at a rate of approximately 60 000 km2 per decade due to increased melting. Improving process representation requires further study but the use of a single accurate ice sheet mask is a logical way to reduce uncertainty among models.
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crandles

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Re: Greenland Melt Impacts 2012
« Reply #8 on: April 04, 2013, 01:57:22 PM »
Crandles, the image isn't showing for me.

Sorry, hopefully now corrected.

HeisenIceBerg

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Re: Greenland Melt Impacts 2012
« Reply #9 on: April 04, 2013, 06:52:45 PM »
This video was just posted today on the Climate Crocks blog.  Jason Box briefly talks about what has been causing the increasingly large amount of melt of the GIS in summer, and how it relates to arctic summer sea ice loss.



Original source: http://climatecrocks.com/2013/04/04/the-paradox-of-cold-continents-warm-arctic/
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AbruptSLR

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Re: Greenland Melt Impacts 2012
« Reply #10 on: June 23, 2013, 05:17:33 PM »
The attached image is from a presentation by Maria Tsukernik, Amanda Lynch, Maya Wei and Irina Gorodetskaya that can be found at the following website:

http://amrc.ssec.wisc.edu/meetings/meeting2013/program.shtml

While this image is not directly related to the July 2012 GIS melt event; nevertheless, this image shows that an Atmospheric River brushed the southern tip of Greenland on July 9th to 10th, 2012 on its way to the UK (where it caused flooding).  My concern is that several decades in the future, with continued global warming, such Atmospheric River, AR, event could transport episodically significant quantities of rain to the southern portions of the GIS (as a note, for the next few decades, until sufficient warming occurs, such AR events could deliver significant quantities of snowfall to Southern Greenland).   

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Sigmetnow

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Re: Greenland Melt Impacts 2012
« Reply #11 on: July 10, 2013, 08:29:08 PM »
Joe Romm's article linked below quotes Professor Edward Hanna from the University of Sheffield’s Department of Geography and Prof. Jennifer Francis about whether “unusual changes in atmospheric jet stream circulation caused the exceptional surface melt of the Greenland Ice Sheet (GrIS) in summer 2012.”

“Our research found that a ‘heat dome’ of warm southerly winds over the ice sheet led to widespread surface melting. These jet stream changes over Greenland do not seem to be well captured in the latest Intergovernmental Panel on Climate Change (IPCC) computer model predictions of climate change, and this may indicate a deficiency in these models. According to our current understanding, the unusual atmospheric circulation and consequent warm conditions of summer 2012 do not appear to be climatically representative of future ‘average’ summers predicted later this century."

http://thinkprogress.org/climate/2013/06/17/2169321/exceptional-2012-greenland-ice-melt-caused-by-jet-stream-changes-that-may-be-driven-by-global-warming/
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ghoti

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Re: Greenland Melt Impacts 2012
« Reply #12 on: July 24, 2013, 10:30:26 PM »
This study covers relatively old data on how melt affects flow speeds.

http://www.nasa.gov/content/goddard/like-butter-study-explains-surprising-acceleration-of-greenlands-inland-ice/#.UfA3xI1wqbo

I really wonder how much larger an impact the 2012 melt had on flow.

Sigmetnow

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Re: Greenland Melt Impacts 2012
« Reply #13 on: July 27, 2013, 04:42:03 PM »
Rolling Stone has a great article on Jason Box which includes recent time on Jakobshavn Glacier on his Dark Snow project.

http://www.rollingstone.com/greenland-melting#ixzz2aFyKZV2F
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