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Account Deleted

In addition, blog Lora Koenig

http://dartmouthigert.wordpress.com/2012/07/21/new-summit-melt-layer/

"I arrived at Summit Station on July 13th, while traveling with the
Joint Science and Education Program (JSEP) for a short visit to the
camp. When we arrived, Summit Station had been experiencing above
freezing temperatures for multiple days prior to our arrival and a
melt layer formed on the near surface snow. I have been studying the
physical properties of the top layers of the ice, the firn, at Summit
and NEEM for my Ph.D. research. Recently, I have been focused on the
melt layers present in both firn cores because they occur very
infrequently. At Summit, there is only one other melt layer besides
the melt layer from this past week and this previous melt layer dates
to 1889."

Dana1981

Neven, we'd like to re-post this on SkS if you don't object.

Believe it or not, Monckton and Heartland argued just a few days ago that Greenland has gained ice over the past few decades. Major face-palm.

Neven

Be my guest, Dana. It's one big copypaste anyhow, so I don't see how you need my permission. :-)

Anthony Watts went into ultrafast downplay mode, so the forces of delay must be really displeased with this news. There's no need really. However, if it happens again within a lot less than 150 years...

Account Deleted

"Believe it or not, Monckton and Heartland argued just a few days ago that Greenland has gained ice over the past few decades."

It's a complicated question. I recently found an old news.

http://p38assn.org/glacier-girl.htm
http://p38assn.org/glacier-girl-recovery.htm
"Well, maybe not as simple as that, seeing how it was 268 feet of ice."

The plane crashed in 1942 in 1992 was covered by nearly 100 meters of snow and ice.

AmbiValent

If Greenland would keep exactly the same amount of ice over time, it would still be normal for objects to be covered with ice. Because Greenland would still lose ice all around its edges, new snow and ice on top of the old one - and any objects left there - would be needed to compensate the loss.

So one would have to check whether the gain by new ice outweighed the ice loss around the edges. It may well be the case that Greenland's ice mass indeed grew between 1942 and 1992, since it was generally a cooler era than the rapid warming era we have now (maybe due to all the sulfur in the air working against the greenhouse effect).

But if Greenland is losing albedo in an area, this means in this area ice was not gained but actually lost, because the ice covering the dust and soot had melted, allowing it to become denser, increase absorption and cause the albedo loss.

So independently of whether Greenland had gained ice in the last century, right now it's losing ice, and rapidly.

Account Deleted

"Because Greenland would still lose ice all around its edges, new snow and ice on top of the old one - and any objects left there - would be needed to compensate the loss."

Example
http://nsidc.org/cryosphere/sotc/images/jakobshavn_retreat.jpg

Neven

I've added an update to the post. Greenland is hot! Figuratively and literally speaking.

Dana N

Neven - the Monckton/Heartland claim was that Greenland has gained ice since 1992, so it actually is not complicated in this case!

Richardjtelford

Does anybody know the evidence for this statement "Ice cores from Summit show that melting events of this type occur about once every 150 years on average"?

The ice core from Summit analysed by Kaitlin Keegan only goes back to 1750 and has just a single melt layer in 1889. Hardly sufficient information to say melt layers occur ever 150 years - a statement that the WUWT is using to claim that nothing unusual is happening. I have not been able to find archived data on melt layers on the long cores from Summit.

Andy Lee Robinson

When will we know if this unusually widespread melt led to, or will lead to a change in mass balance?

How are the moulins and supraglacial lakes doing compared with previous years?

The recent video of the surging Watson River was fairly impressive, but how did its flow rate differ from the average for the time of year?

Was this representative of all rivers draining from the icesheet?

rayduray on Climate Crocks mentioned that the Watson River flow rate was 3.5 million litres per second - that's 3,500 x 86400 = 300 million tonnes per day, or nearly 1 km3 of water every 3 days! For just one river! Is this correct?

Multiply by the number of rivers and their relative flow rates, and it could be a truly awesome amount of melting this year.

dorlomin

The ocean temperatures around Greenland have been very, shall I say impressive, over the past few weeks.

Not really a suprise to see something this dramatic.

Kris

Arcticicelost80 stated


The plane crashed in 1942 in 1992 was covered by nearly 100 meters of snow and ice.

Thus the plane has sunk for about 100 m deep into the ice.

After all, sinking, it's that what boulders and heavy objects do in moving ice fields, don't they?
The same reason why people fallen into a glacier reappear only 50-100 or even 150 years later at the tongue of a glacier.

Andreas Muenchow

River discharge from Watson River, Greenland:

It appears that best estimates of annual averages are perhaps closer to 250 m^3/s which is slightly smaller than the discharge from the Delaware River (330 m^3/s). This does not mean that peak discharges cannot reach much larger values, but a short pulse may not reflect the importance of this element in the mass balance of Greenland. My source is http://www.the-cryosphere.net/6/199/2012/tc-6-199-2012.pdf that I still have to read more careful than a 10 minute browse. I wonder if there are other gauged rivers around Greenland and if a scaling law exists that relates catchment area (and/or temperature and/or something) to discharge for land-based glaciers or ice sheets. I know such laws exist for mid-latitude rivers as well as Alaska's many streams and rivers ... but Greenland?

rayduray

Hi Andy Lee,

You ask:

"The recent video of the surging Watson River was fairly impressive, but how did its flow rate differ from the average for the time of year?"

From what I've read, this event was a unique anomaly. The flow exceeded any previous flooding event by a factor of 2.

The huge flow of water was most likely due to glacial dam giving way and draining a significant body of trapped, hidden water. This happens with some frequency in Iceland, but has been rare in Greenland. A similar phenomenon has been studied in the western U.S. Glacial Lake Missoula http://en.wikipedia.org/wiki/Glacial_Lake_Missoula has been well-researched over the past few decades. Here's one of my favorite videos about these gargantuan flood events: http://www.youtube.com/watch?v=r1MNpYb5YCA

***
"Was this representative of all rivers draining from the icesheet?"

No. This was a unique situation. Of course in a warming world, we can expect more such unique events never before observed.

***
"rayduray on Climate Crocks mentioned that the Watson River flow rate was 3.5 million litres per second - that's 3,500 x 86400 = 300 million tonnes per day, or nearly 1 km3 of water every 3 days! For just one river! Is this correct?"

You math seems good. But keep in mind that this event was an outlier.

-Ray

Wipneus

Head line of Dutch Volkskrant , a normally scientific correct newspaper:

"IJs Groenland in vier dagen vrijwel weggesmolten "

"Greenlands ice has melted almost completely away in four days"

AmbiValent

If you add in "surface" after "ice" the headline would be correct. But usually nobody cares about surface ice melting, just whether the main ice remains or melts, so somebody probably misunderstood the true content of the news.

crandles

>>The plane crashed in 1942 in 1992 was covered by nearly 100 meters of snow and ice.

>Thus the plane has sunk for about 100 m deep into the ice.

>After all, sinking, it's that what boulders and heavy objects do in moving ice fields, don't they?

Not sure sunk is the right word as it may imply going down faster than surrounding ice. Talk of boulders and heavy objects compounds this error. A plane is going to be light compared to ice.

Surely it is much more a case of add snow and ice above the object while ice below moves downhill.

.

GRACE tells us greenland is losing mass but when did GRACE start and how well did we know the mass balance between 1992 and GRACE start? If not very well, can we be sure there wasn't much change from river discharge rates or something?

Seeing glaciers retreat may well mean we knew there was mass loss around edges but did we know whether it might be outweighed by mass gain at high altitude?

Philippe Terrier

Here is the last GFS temperature forecast for Saturday afternoon:

http://img837.imageshack.us/img837/7664/rtavn905.png

New global melt event ?

Rob Dekker

Wipneus,
I seems that the Volkskrant realised their mistake.
They mellowed it out to :
'Groot deel' bovenkant landijs Groenland aan het smelten
with the first line :
Een gedeelte van de toplaag van het landijs op Groenland is half juli zo snel gesmolten dat onderzoekers van NASA...
Did Monckton or WUWT make a similar correction to their statements ?

Rob Dekker

Richardjtelford said

The ice core from Summit analysed by Kaitlin Keegan only goes back to 1750 and has just a single melt layer in 1889. Hardly sufficient information to say melt layers occur ever 150 years - a statement that the WUWT is using to claim that nothing unusual is happening.


I second that opinion.
The Greenland ice sheet cores record more than 100,000 years of climatic history from the summit.
Did nobody analyse melting lines in these cores earlier than 1750 ?
If not, why not ?

Philippe Terrier

"I second that opinion.
The Greenland ice sheet cores record more than 100,000 years of climatic history from the summit.
Did nobody analyse melting lines in these cores earlier than 1750 ?
If not, why not ?"

An hypothesis could be that "melting lines" are only visible in fresh, not fully transformed ice, i.e. only at the top of ice cores...

Philippe Terrier

I found a relevent reference from Dr Keegan:

http://adsabs.harvard.edu/abs/2011AGUFM.C33C0661K

The reference to previous melting events probably comes from this study, not yet published (only a congress abstract)

Glacierchange.wordpress.com

How will the cat in the hat clean up all of that pink? The impact of higher albedo and higher temps are reinforcing of each other. The result will be bigger impacts on the glaciers ending on land and small Greenland Ice Caps. Mernild et al (2012) has focussed on these. The area around De Reste Bugt Glacier emphasizes this too.

Wipneus

Holocene GISP2 melt years:

http://www.gisp2.sr.unh.edu/DATA/alley1.html

Data from: Alley, R.B. and S. Anandakrishnan. Variations in melt-layer frequency in the GISP2 ice core: implications for Holocene summer temperatures in central Greenland. Annals of Glaciology 21, 64-70 (1995)

Account Deleted

Philippe Terrier, thanks for the interesting link.

http://adsabs.harvard.edu/abs/2011AGUFM.C33C0661K
"A core from the CO2 firn-air sampling site at NEEM was retrieved in July 2009, and the physical properties of the firn have been analyzed. In the 81m of analyzed firn core, two regions containing ice layers were identified at depths of 29m and 46m. Isotopic analysis provides a depth-age scale that dates these layers to be from 1935 and 1879, respectively."

But NEEM site is not a Summit. This is the north-west Greenland.
http://neem.dk/about_neem/

Account Deleted

Wipneus, GISP2 is a Summit. It is on the topic.

http://www.gisp2.sr.unh.edu/DATA/alley1.html
Before 1950 there was only one new case of melting (probably in 1879).
During the medieval warming 4 cases were melting.

rayduray

Cross-posting from Dr. Jeff Master's blog on this topic:

http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=2160

Ben Burch

Dark objects on ice sink can even when they are "lighter" than the ice and even if there is no snowfall at all. Mechanism is that sun warms the object, and the water drains away under it or evaporates away from the margins. The density difference doesn't matter much with a solid you are melting your way into.

rayduray

Consider Greenland for your next up-and-coming-paradise-above-the-Arctic-Circle vacation! A land of the Magical Midnight Sun and Million Star Accommodations!

http://www.youtube.com/watch?v=dOnnHoFp5SE&feature=related

Grypo.wordpress.com

http://www.igsoc.org/annals.old/21/igs_annals_vol21_year1995_pg64-70.pdf

This is the paper that can put the '150 years' comment in proper context. See the figures. A significant amount of melt years occurred during the Mid-Holocene Optimum. The average over the last 4000 years is about every 250-300 years. This includes the MWP where seven of the last 8 occurred, meaning, before a few weeks ago 1889 was the only occurrence in the last 800-900 years or so. Dr. Alley's hypothesis is that these clusters of melts over 6000 years ago were do to high summer insolation.

Is that unprecedented enough for ya kiddies?

Grypo.wordpress.com

I forgot to include that Alley deduces a large temperature drop over the Holocene because of this data.

Neven

Is that unprecedented enough for ya kiddies?

No! It never must have occurred before in the history of our property, or else it doesn't count!

Apocalypse4Real

Hmmm....

Let's do some rough math and speculation... Alley concluded that we have experienced a 1.3 degree cooling at GISP2 in the last 7.5 ka.

According to the NOAA State of the Climate
Global Analysis for June, 2012,

"The average combined global land and ocean surface temperature for June 2012 was 0.63°C (1.13°F) above the 20th century average of 15.5°C (59.9°F)."

Furthermore,

"The Northern Hemisphere land and ocean average surface temperature for June 2012 was the all-time warmest June on record, at 1.30°C (2.34°F) above average.

http://www.ncdc.noaa.gov/sotc/global/

One could presume that the 1.3C change in temp for June 2012 (or July) compared to the last century effected Greenland as well. This begins to place a perspective on the cooling vs melt frequency.

Now we revisit Alley's melt frequencies (in "Results")

Average for 0-10000 BP is 1/153 yrs.
Average for 5500-8500 BP is 1/82 yrs.
Average for 1000-4000 BP is 1/250 yrs.

If his melt frequency assumption for approx 7500 ka ago is based upon 1.3 C above the current temps - it seems we are negating that very quickly. That would seem to put us back to a potential 1/82 year occurence.

Perhaps it is more frequent - or will rapidly become more frequent. In his "Calibration" section for GISP2 with Site A melt data he mentions a statistical correlation for temp vs melt.

"Assuming that the summertime temperatures have the same standard deviation for GISP2 and site A over the study period, that standard deviation must be 3.5°C so that a 2°C increase in temperature causes a 7.5-fold increase in melt frequency, based on examination of standard statistical tables for the integral of the normal distribution."

While this dealt with temperature difference between two sites in relation to melt frequency - is it reasonable, or statistical to assume that the same ratio would hold for an increase in frequency for the same location with a 2 C increase in temperature over time?

I hope someone will correct me and enlighten us.

Werther

It is not important to debate whether Dome melt as a singularity is exceptional, unprecedented or whatever. It happened before under natural variety.
What is important is the multi-year rise of melt rate for the GIS as a whole. This features a clear graph starting around 125 km3, varying around 250, topping at 550 during 2010 and this year on course for maybe 700. This may be hard to establish as unprecedented. But it isn’t hard to imagine where this is going under constant forcing and emerging feedback. The South Dome is under siege and prone to raise sea level. On the worst IPCC scenario path…

James Benison

Well, this melt may prove to be not very exceptional after all. In fact, based on the forecast it may happen again this weekend.

Philippe Terrier

" Well, this melt may prove to be not very exceptional after all. In fact, based on the forecast it may happen again this weekend."

Indeed, last GFS forcasts all greenland above 0°C:

http://img849.imageshack.us/img849/3793/rtavn6052.png

Wunderground forcast for Summit: +1 max on Saturday:

http://www.wunderground.com/cgi-bin/findweather/hdfForecast?query=Summit+greenland

Peter Ellis

The historical data is based on ice layers in the firn (compacted snow). Therefore, to be distinguishable, you'd need significant snowfall to occur in between two melt periods, to produce distinct icy layers. I don't know what the resolution is, but it certainly won't be on the order of days, more likely years.

So, however many times the temperature goes above freezing this year, for comparison to the historical data we just have to call it a "melt year" and leave it at that, I think.

Peter Ellis

Put another way, I don't think the snowfall (if any) in the last 6 days will be suffcient to produce distinct layers if there's another melt episode (or two, or three) this year. In a century's time it'll just show up as one layer.

Seke Rob

From the little while ago Rutgers snow *reasoned* anomaly from the observed on various maps and current developments, looking very much forward what they are going to report for cover in the weekly data for July. Not due out until later in first week of August.

Espen Olsen

The opening of the North East and North West passages this season will probably not be many days apart.

none

Not even sure the NWP will open at all if McClure Strait doesn't get unblocked at the western end somehow, currently choked with heavy multiyear ice...

Nightvid Cole

What about at the lower altitudes, if Summit will rise above freezing for the 6th time this month?

Neven

Not even sure the NWP will open at all if McClure Strait doesn't get unblocked at the western end somehow, currently choked with heavy multiyear ice...

I was surprised to see on yesterday's satellite image that McClure Strait is actually almost free of ice. It's the eastern part of the NWP that seems to be the problem. If it is a problem, because the clouds are still blocking that portion. Either way, almost all of the ice seems to be melting in situ.

Kris

Rob stated first:

The Greenland ice sheet cores record more than 100,000 years of climatic history from the summit.
Did nobody analyse melting lines in these cores earlier than 1750

and then asked:

If not, why?

Well, for a starter you would need a 2 km deep drill right to the bottom of the ice shell. Which implies the need for heavy tools and materials, and above all a massive investment in money and resources.

It had been done at Antartica, a drill trough a 2 km thick ice layer to the surface of a frozen lake (a lake with a Russion name which I don't recall for now).

Obviously, the reasons for Russians and Americans to spend all that taxpayers money at Antartica come from a military-strategic scope, in order to claim as much territory as possible for a starter.

As the latter isn't feasible at Greenland, it's only about research and science there.
And far less of money available. (-:

Artful Dodger

Werther wrote: "On the worst IPCC scenario path…"

hmm, perhaps "hors catégorie" is apropos (h/t dana1981).

Michael Fliss

Kris,

From Wikipedia on Summit Camp deep drill: "On July 1,1993, the bedrock was reached."

http://en.wikipedia.org/wiki/Summit_Camp

More information on Summit, Greenland: http://www.esrl.noaa.gov/gmd/obop/sum/index.html

me.yahoo.com/a/nSjChi4X3vr8X3DRw93GkY1.cerja.8nvWk-

Richardjtelford said

The ice core from Summit analysed by Kaitlin Keegan only goes back to 1750 and has just a single melt layer in 1889. Hardly sufficient information to say melt layers occur ever 150 years - a statement that the WUWT is using to claim that nothing unusual is happening.


I second that opinion.
The Greenland ice sheet cores record more than 100,000 years of climatic history from the summit.
Did nobody analyse melting lines in these cores earlier than 1750 ?
If not, why not ?
Posted by: Rob Dekker | July 25, 2012 at 12:18

Yes they did the results are here going back 10,000 years.

http://www.gisp2.sr.unh.edu/DATA/alley1.html

Note: "Well-preserved annual layers can be counted confidently, with only 1% errors for the age of the end of the Younger Dryas 11,500 years before present."


Twemoran

Kris

For the last 10.000 years check this graph from gisp2

http://www.gisp2.sr.unh.edu/DATA/alley1.html

Just count the green lines.

Much older cores are available, but the Holocene is probably enough for our purposes.

Terry

Twemoran

oops - looks like we both posted the same data at the same time.

The 150 year scenario was an average of the Holocene, which was very misleading.

Terry

Peter Ellis

Hmm, not that misleading. For events occurring a century or more apart, you need to average over 1000 years or so to get an idea of the true average rate. Doing that, you see that over the last 4000 years, the 1000-year smoothed value has been hovering around 0.04, i.e. one melt year every 250 years. Sure, it's a bit longer than the stated 150, but it's close enough that it's not grossly misleading - and averaging over the whole historical record negates claims of cherry-picking.

The most accurate statement would be that melt years this intense are somewhere between a 1/250 year event and 1/60 year event, being more common during the Holocene optimum 6-8000 years ago when the Earth's orbital tilt favoured (local) Northern Hemisphere warming. But you won't fit that into a newspaper article >:-)

Twemoran

Pete

Undoubtedly accurate, but there are other ways of expressing how unusual the event is.

How about "Only once since Columbus's discovery of America" or "Only twice since the signing of the Magna Charta"

Probably cherry picked, but relating historic events to the data might make an effective headline.

The thing I drew from the chart was that averaging events that occur in clusters can be misleading. The most recent cluster occurred in the Viking Age with a long dry period following that.

Terry

Artful Dodger

Jason Box provided a good graphic on his blog (links above) about the energy budget at the Greenland summit. It seems an increase of <1 w/m^2 was enough to nudge the summit into a melt. So with the solar cycle peaking in 2013, we will likely see another summit melt event next year.

me.yahoo.com/a/nSjChi4X3vr8X3DRw93GkY1.cerja.8nvWk-


Based on the data at Summit given in GISP2 the rate of occurrence there is ~15/4000 years, since it’s such a rare event it’s reasonable to model it as a Poisson process, with a λ of 0.375 (per century). Over the last 4000 years that’s a mean expectation of 0.375/century with a variance of 0.375. From a Poisson analysis you’d expect ~27 centuries without a melt, ~10 centuries with one melt year, ~2 centuries which is in reasonable agreement with the data. As usual with such data it's quite normal to see clustering, going further back doesn't make sense though because of the significant increase in insolation then.

Phil.

Bob Wallace

1889. The Great Johnstown Flood.

"The great storm had its origin on the California coast on May 26. From the Pacific to the Atlantic seaboard, heavy rains accompanied the disturbance…. The storm had general characteristics which made it unusual for such an extensive change of weather. The storm moved at an unusually slow pace, and at a regular speed. High temperatures were shown in some areas; while low temperatures from frost to snow prevailed in others. Local storms in this vast cyclonic movement were unusually violent. Saturation was dense and rainfall enormous.

A pressure area over the Atlantic Ocean turned the winds to a south-to-east direction although they usually moved from south to west. The changed direction of the ocean winds, coupled with the normal west-to-east movement of the storm current, forced the winds with their huge rainfall into a comparatively small area over the crest of the Alleghenies, –three low pressure areas from the west, southwest, and southeast “met in a dire embrace upon the summits of the Allegheny mountains.”"

http://www.jaha.org/edu/flood/why/rain_greatstorm.html

Perhaps some weather sleuthing is in order....

cynicus

Statistics is a great tool, but physical causes are better. When Greenland gets hotter you expect more Summit melt occurrences, no matter how often it happened in the past.

SteveMDFP

Bob Wallace,

Thanks for the fascinating contribution. It seems 1889 was a very odd year of weather. I found this interesting:
http://www.sciencedaily.com/releases/2012/06/120614131059.htm

"This past March was the second warmest winter month ever recorded in the Midwest, with temperatures 15 degrees above average. The only other winter month that was warmer was December of 1889, during which temperatures were 18 degrees above average. Now, MU researchers may have discovered why the weather patterns during these two winter months, separated by 123 years, were so similar...."

idunno

arcticnews has some interesting graphs, etc from Sam Carana:

http://arctic-news.blogspot.co.uk/2012/07/greenland-is-melting-at-incredible-rate.html

Neven

A comment I made over at SkS:

I didn't give it much thought, as I figured it was entirely irrelevant to the event itself, but now that I have thought about it, I find it amazing that Koenig has said this and even more amazing that the people over at NASA put this quote in. They handed the fake skeptics everything they needed to mislead and obfuscate on a silver platter.

Glacierchange.wordpress.com

The melt event is a signature event, but short term. The longer term issue of ice sheet mass balance for 2012 is indicated by the extent of bare ice, as this is the best single indicator of overall mass balance annual variation. Notice the bare ice graph, fourth down from Xavier Fettweis's lab.

Philippe Terrier

@Glacierchange

Thank your for the data !

Is the plot regularly updated ?

Philippe Terrier

Summit, top of Greenland Ice Sheet (3199m), reports O°C / 32°F.

http://www.summitcamp.org/status/webcam/

Actually, temperature is constantly above -4C/25F since about 36 hours:

http://www.summitcamp.org/status/environmental/?period=week

A new massive melting event ?


Glacierchange.wordpress.com

An excellent temperature graph provide by Chris Shuman, NASAfrom the Greenland Summit puts 2012 in perspective versus other years.

Bernard Vatant

http://rapidfire.sci.gsfc.nasa.gov/imagery/subsets/?subset=Arctic_r02c03.2012212.terra.250m

Looks like multi-years fast ice is giving way everywhere in this northeastern coast. Can experts confirm? Will this ease the way out through Fram?

Espen Olsen

Hi Bernard,

Yes the fast ice in Jøkelbugt is on the move now, it is the first time since 2004 - 5 I believe, it is not happening each year, normally this fast ice dont block the "Fram Export", and the Fram situation has been very stationary for the last 2 weeks.
It will be interesting to watch if there are any reactions from the 2 Giant Glacier 79th and Zachariae, since there is no sea/fast ice to stop an eventually calving. This area (Jeokelbugt) is probably also where you will find the biggest differences of many since 2007, so I will suggest you to watch this area for next month, there could some big actions!

Espen Olsen

Philip,

Yes I know the ice breaks up in the area, but not this early, you are comparing day 248 with day 213, and the result last year was the ice stayed as it normally do, but this year I am pretty sure it will be far a way in the sea somewhere on day 248.

Philippe Terrier

"An excellent temperature graph provide by Chris Shuman, NASAfrom the Greenland Summit puts 2012 in perspective versus other years."

The graph has been updated with the end-of-july "heat wave" event:

http://jcet.umbc.edu/2012/07/nasa-72412-press-release-green.html

Neven

Thanks, Philippe!

Jim_pettit

Here's another just-published NOAA press release (Summer Weighing Heavily on Greenland Ice Sheet). It contains the Greenland Summit temperature graph (made easier to read by the subtraction of most colors), alongside two Greenland-centered hemispherical images, one showing May-July 700 mb pressure anomalies, and the other showing 700 mb temperature anomalies.

Pretty astounding, really---and small wonder the ice pulled such a vanishing act.

idunno

An interesting article from Richard Black reports on Danish research suggesting that Greenland melts in spurts, e.g. from 1985 to 1993, and from 2005 to 2010...

http://www.bbc.co.uk/news/science-environment-19095069

Artful Dodger

New online article in the Aug 2, 2012 Scientific American, with a Slideshow:
Greenland Meltdown Driven by Collapse of Glaciers at Ocean Outlets

Werther

Preluding any official publications on GIS mass balance for this year are some clues from proposed AGU fall-meetings ( FI http://fallmeeting.agu.org/2012/eposters/eposter/c51b-0784/).

Apparently a warm summer like this year has implications for the formation of ice out of firn/snow. The assumptions, with which actual measurements are calculated into reliable mass balance estimates, have to be renewed.
Other subjects announced for the meeting will be informative too. Like new research op surface height change, the effect of micro-organisms on the ice etc.
To have a clear view on the relevance of this summers melt, it would be great when a presentation on actual mass balance will be presented at the AGU meeting.

Meanwhile, I’m working on the MODIS day 191-196 tiles on Greenland. I chose the days because snow/cloud cover looked to be at minimum.
I’m trying to define/CAD the ice boundary at that time. It is a hell of a task, I’ve spent about 30 hours on it and have app. another 20% to do. While it could give a quite good area calculation, it will also enable to make out differences with the other 3 available years.

Eyeballing hasn’t got me very far. I hope this work will provide a basic insight whether a geographically noticeable retreat has started.
If so, and combined with what’s already published on mass loss, it would be another sign that icesheets react quickly to climate change. And that any arguement like the melt process would take at least hundreds of years are irrelevant in today’s circumstances.

LRC

Found this: http://imbie.org/imbie-2012/results/
What is scary is that the curve of the charts at the bottom seem to following a similar trend as to the collapse of the Arctic Ice. This also shows beyond question that what is happening in the Antarctic is not the ice extent, but the ice balance. Not only that, I believe that although the East is looking great for now, it is hiding the fact that although still very cold is in fact warming and once it hits that magic temp will collapse there also.

Werther

Photobucket

GIS limits 10-14 July 2012.

For what its worth... I finally fixed the outer boundary of the icesheet in CAD on the MODIS tiles.
I know...it looks a bit 'pale', but I just wanted to share this baby of mine with you.
Some first data: the line is 55.790 km1 long (my...I digitized 173.761 points in the polyline). The area is 1.793.564 km2.

I'm off to get some sleep, but I'll be back on this when I find time to compare this to the earlier years.

Neven

Wow, that's awesome, Werther.

Werther

GIS evaluation 2009-2012 … some first impressions.

I couldn’t wait to get the corresponding 2009 MODIS tiles under the CAD-digitalized ice/snow-limit 10-14 July 2012 polyline.
I’m planning to put specific info on a map. That will take some time, so here is a first general impression.

On the South-Southwest there’s noticeable retreat. That goes for most glacierfronts (200-1500 m) as well as for the snow/ice limit on the fjells and around the nunatakkers (average about a pixel-width; 200-300 m).

The mountainous east side holds steady. There are even some glacierfronts that have extended. A part of the coast between Tasiilaq and Scoresbysund even had less snow and remaining landfast ice in July '09 than last July.

The North is also steady. No surprise that Peterman Glacier stands out, but so does loss on the Humboldt and some other, smaller outlet glaciers.

I feel relieved that the retreat looks not as bad as in my worrisome musings.

Nevertheless, the progressive retreat in SW Greenland is considerable.
On the mountain ridge in the SE there could be some snow accumulation, but not enough to compensate.

There’s FI the melt zone to investigate further, which could tell something about the lowering of the sheet surface. For now, what I found fits well with the mean average mass balance totals for the last three years and the supposed big 2012 loss. Relatively big. There’s still an incredible lot of ice out there.

Oh yes. I have to add some of the restrictions I made while digitalizing.

I took the limit of consistent snow/ice. That left out stand-alone icecaps, like FI Fade Isblink.
The same goes for inside ice/snowfree ‘polynia’s’. There are a d***** lot of nunatak strikes in the mountainous parts and some large ice/snowfree landscapes within the sheet north of Scoresby Sound.

Werther

To add some more info on the posts above, I have roughly calculated the margins min/max for what is supposed to be the large 2012 mass loss.
I found retreat '09-'12 in the SW on app. 15000 km1 of the total 56000 km1 icesheet limit. It would correspond with app. 3000 km2.
The mean sheet thickness being 1400 m1, that area would correspond with 4000 km3.
The edge is a lot thinner than the mean thickness. But the equivalent melt extended over a much larger part of the sheet.

The minimum loss is hard to be imagined less than that of 2010 (500 km3), the maximum could even be as large as 1000 km3.

LRC

Can not find any references at this time by googling (probably asking wrong info), but I seem to remember seeing a program about the problems scientist are now having getting good quality ice cores in Greenland because the deterioration of the ice even at depths. Is this true and if so would not that signal the the ice fields are in even greater trouble then we can imagine?

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