Arctic Sea Ice : Forum

Cryosphere => Greenland and Arctic Circle => Topic started by: RaenorShine on April 12, 2015, 05:37:37 PM

Title: Greenland 2015 Melt Season
Post by: RaenorShine on April 12, 2015, 05:37:37 PM
NSIDC have bought up their Greenland Today site for this season (hat tip to Andy from San Diego on robertscribblers blog for pointing this out!), and that is when I've started this thread for the past couple of years.

As previous years I'll be posting regular comments on Melt Area (calculated from satellite measurements by NSIDC http://nsidc.org/greenland-today/ (http://nsidc.org/greenland-today/)) and Surface Mass Balance (calculated by a DMI model and reported on Polar Portal http://polarportal.dk/en/groenlands-indlandsis/nbsp/isens-overflade/ (http://polarportal.dk/en/groenlands-indlandsis/nbsp/isens-overflade/) and DMI's own site http://www.dmi.dk/en/groenland/maalinger/greenland-ice-sheet-surface-mass-budget/ (http://www.dmi.dk/en/groenland/maalinger/greenland-ice-sheet-surface-mass-budget/)).

The melt season proper will not really start until the middle of May, but we may start seeing the early signs shortly.

A couple of things of note from over the winter.

The statistical relationship between ice sheet reflectivity and total melt loss broke down in 2013 according to this release from DMI http://polarportal.dk/en/nyheder/arkiv/nyheder/ice-sheet-surprises/ (http://polarportal.dk/en/nyheder/arkiv/nyheder/ice-sheet-surprises/). Daily albedo images (from satellite data) are reported on the Polar Portal, but they will not be using this to estimate total loss (that is Surface Mass Balance and Glacial Runoff), but instead  this will only be reported on a 3 month+ delay in GRACE Data.

Both Polar Portal and NSIDC have issued a summary of the 2014 melt season
The winter of 2014/2015 has added a lot more Surface Mass Balance than average (although we seem to be gradually returning to mean.http://polarportal.dk/fileadmin/polarportal/surface/SMB_curves_LA_EN_20150411.png (http://polarportal.dk/fileadmin/polarportal/surface/SMB_curves_LA_EN_20150411.png). What is striking is that this is almost all on the Southern tip and East coast of Greenland, with the North and West of Greenland significantly below average. http://polarportal.dk/fileadmin/polarportal/surface/SMB_map_LA_acc_EN_20150411.png (http://polarportal.dk/fileadmin/polarportal/surface/SMB_map_LA_acc_EN_20150411.png).

With El Nino providing record tempuratures and sea ice at a very low level we should be in for another interesting melt season.
Title: Re: Greenland 2015 Melt Season
Post by: RaenorShine on April 17, 2015, 10:55:11 AM
The southern tip of Greenland had one of the first bursts of surface melt around the edges of the sheet on 15/4 according to the NSIDC measurements.

DMI showed a large gain in Surface Mass Balance from a storm over the same area, so this may well be rain falling on to the snow (tempuratures were just above freezing according Weather Underground stations in the area)
Title: Re: Greenland 2015 Melt Season
Post by: RaenorShine on April 24, 2015, 10:41:37 AM
Since my last update we've continued th have a lot of precipitation on the south east coast, which has given a fairly large uptick in DMI's Surface Mass Balance  (ending on Wednesday). This hasn't all been falling as snow though, and NSIDC have shown a couple of small upticks in melt area as seen last week also.

Over the past couple of days DMI have been showing slight SMB loss along the edges of the sheet along the South East Coast, the first signs of the melt season proper beginning, but still being more than offset by precipitation elsewhere.
Title: Re: Greenland 2015 Melt Season
Post by: johnm33 on April 24, 2015, 07:24:32 PM
Any possibility that the limb of yellow heading east was an outburst of fresh water from Greenland
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fpuu.sh%2FhpkTK%2F3c0394036f.jpg&hash=ac45d01a8a0847ae160719537b5c75a5)
There's a similar feature on the SSH.
From http://www7320.nrlssc.navy.mil/GLBhycomcice1-12/arctic.html (http://www7320.nrlssc.navy.mil/GLBhycomcice1-12/arctic.html)
Title: Re: Greenland 2015 Melt Season
Post by: RaenorShine on April 28, 2015, 10:15:32 AM
Any possibility that the limb of yellow heading east was an outburst of fresh water from Greenland

As I understand, a lot of the sea ice on the east of Greenland comes via Fram Strait export and is carried by currents southward.

The DMI Surface Mass Balance model shows its first negative value (just) for the year today, this is more to do with lack of precipitation than extensive melt this early in the season, with very little melt showing on NSIDC.
Title: Re: Greenland 2015 Melt Season
Post by: johnm33 on April 29, 2015, 10:00:29 AM
Any possibility that the limb of yellow heading east was an outburst of fresh water from Greenland

As I understand, a lot of the sea ice on the east of Greenland comes via Fram Strait export and is carried by currents southward.

The DMI Surface Mass Balance model shows its first negative value (just) for the year today, this is more to do with lack of precipitation than extensive melt this early in the season, with very little melt showing on NSIDC.
Your right. Having looked for too long at Greenland, finding nothing, I finally went back beyond the 6th and wind conditions then were conducive to driving some of the southbound ice east, but not enough to cross the 15% threshold.
Title: Re: Greenland 2015 Melt Season
Post by: RaenorShine on May 06, 2015, 03:41:35 PM
All is still very quiet on the melt front, but there is also very little gain since the large storm ended nearly 2 weeks ago, bringing the SMB graph back very close to the average YTD gain.

NSIDC is showing only the odd pixel for a day or 2 (with none today), but no sustained melt.

Polar Portal have restarted the albedo anomaly plots on their surface page (http://polarportal.dk/en/groenlands-indlandsis/nbsp/isens-overflade/ (http://polarportal.dk/en/groenlands-indlandsis/nbsp/isens-overflade/)). It looks very average so far, with few major deviations from the 2000-2009 average values.
Title: Re: Greenland 2015 Melt Season
Post by: RaenorShine on May 21, 2015, 10:38:41 AM
With parts of the arctic breaking heat records you might expect a earlier start to the melt season in Greenland, but it has been quiet so far, with only one day of slight negative Surface Mass balance (SMB) on DMI, and no days where over 5% of the sheet has melted.

DMI has shown two large precipitation events (14 May and 19-20 May) that have kept the Year to date SMB above the average for this time of year. As the current storm moves northward, there is a glimmer of increased melt on the SE coast.

The snow storms have also whitened the icesheet, taking off the slight anomoly that was developing in the south. This will slow melt for a week or so until it gets back to where it was.

NSIDC shows one pixel of surface melt for 19/5, so all is quiet here also.

Title: Re: Greenland 2015 Melt Season
Post by: RaenorShine on June 03, 2015, 06:49:31 PM
After yet another storm a couple of days ago (which bought the mass gain this year to above average), the Greenland melt season seems to be getting underway. The past 2 days DMI have reported a 1Gt mass loss per day,and NSIDC have the melt area climbing steadily (although still below average).

Title: Re: Greenland 2015 Melt Season
Post by: BornFromTheVoid on June 05, 2015, 04:29:30 PM
Current AMA on the science sub reddit: https://www.reddit.com/r/science/comments/38nt2y/science_ama_series_pulling_the_plug_melting_ice/ (https://www.reddit.com/r/science/comments/38nt2y/science_ama_series_pulling_the_plug_melting_ice/)

Science AMA Series: Pulling the plug: Melting ice and draining lakes on the Greenland Ice Sheet. We’re Laura Stevens and Dr. Sarah Das, glaciologists at MIT and the Woods Hole Oceanographic Institution, here to talk about all things ice! AMA!

Yesterday we published a paper in Nature on supraglacial lake drainages on the Greenland Ice Sheet. Supraglacial lakes form on the surface of the ice sheet during the summer, when temperatures get above freezing in the daytime. In a 2008 study, we discovered that these lakes, some of which are miles wide, can drain in a matter of hours through long cracks known as hydro-fractures that open in the lakebed. These drainage events send a flood of meltwater comparable to Niagra Falls thousands of feet straight down to the bottom of the ice sheet. The meltwater causes the ice to temporarily speed up, moving more ice to the edge of the ice sheet where it calves off into the ocean as icebergs. It’s important to know where and when lakes will drain in order to predict how fast the ice sheet is moving and how much the ice sheet contributes to sea level rise.
Since that study in 2008 we have been working hard to figure out what triggers these hydro-fractures, and what that might mean for the future of the ice sheet (and for people elsewhere on the planet) in a warming climate. We do this by traveling every summer to lakes on the ice sheet via helicopter, setting up GPS stations around the lakes, and then using our measurements to observe how the ice sheet surface moves during lake drainage events. We found that enough meltwater gets down to the bottom of the ice sheet before the lake drains to cause the ice sheet surface to be pushed up and stretched. This stretching causes new fractures to form, and once one of those fractures intersects the lake, water from the lake drives the crack open and the lake is history.
We will be back at 1:00 pm EDT (10:00 am PDT, 5:00 pm UTC) to answer your questions about Greenland lakes, global warming, or the life of a scientist doing research on the ice sheet. AMA!
Title: Re: Greenland 2015 Melt Season
Post by: RaenorShine on June 09, 2015, 10:32:04 AM
Greenland is still quiet on the melt front.

Jason box posted the following

http://www.meltfactor.org/blog/greenland-melt-season-kicks-off-slowly-in-2015/ (http://www.meltfactor.org/blog/greenland-melt-season-kicks-off-slowly-in-2015/)

Quote
Greenland melt season kicks off slowly in 2015; the new abnormal

Sitting here in Kangerlussuaq west Greenland expecting not a large melt year. Like another late melt season, 2013, a sticky atmospheric circulation pattern in the past 5 months has favored cold air transport down the west coast of the island.

............
Title: Re: Greenland 2015 Melt Season
Post by: Yuha on June 21, 2015, 12:42:36 PM
It really was a cold May in Greenland. According to NOAA (http://www.ncdc.noaa.gov/sotc/global/201505):

Quote
All of Greenland, but particularly notable in the far northeast, was colder than average for May. Danmarkshavn was 4.6°C (8.3°F) below its 1961–1990 average, the coldest May temperature since records began there in 1949.
Title: Re: Greenland 2015 Melt Season
Post by: Nightvid Cole on June 21, 2015, 06:49:01 PM
We are now having our first "big" melting event for the year:


Title: Re: Greenland 2015 Melt Season
Post by: Neven on June 21, 2015, 07:48:57 PM
Bound to go up with clear skies and higher temps forecast for all of Greenland.
Title: Re: Greenland 2015 Melt Season
Post by: Lord M Vader on June 22, 2015, 07:57:46 PM
After a very slow start to the melt season the melting rate have ramped up and yesterdays melting was above 2 sigma... Let's see if this continues or not...

//LMV
Title: Re: Greenland 2015 Melt Season
Post by: Nightvid Cole on June 23, 2015, 07:04:38 PM
Maybe it's just me, but with a bit of head tilting and staring, I believe I am seeing the entire southern 1/3 of Greenland to be darkening, indicating surface melt:



Title: Re: Greenland 2015 Melt Season
Post by: Juan C. García on June 23, 2015, 09:34:06 PM
We are now having our first "big" melting event for the year:

The melting increase in only two days:
Title: Re: Greenland 2015 Melt Season
Post by: Rubikscube on June 23, 2015, 10:43:26 PM
The hammering has just begun, with no end in sight. I will almost expect NSIDC melt to cross into >50% territory and stay there.
Title: Re: Greenland 2015 Melt Season
Post by: Nightvid Cole on June 24, 2015, 01:45:45 AM
CCI has above-freezing temps going quite high on the ice sheet soon on the Eastern portion  :o

Title: Re: Greenland 2015 Melt Season
Post by: A-Team on June 24, 2015, 06:11:43 PM
Weather has been distinctly balmy at Hans Island.
Title: Re: Greenland 2015 Melt Season
Post by: Rubikscube on June 26, 2015, 10:51:53 PM
Still just about 30% of Greenland experiencing surface melt according to both NSIDC and DMI. Can't quite see why there is so little melting in the south, but at least the heat elsewhere shouldn't be going anywhere anytime soon.

And there a weather station on Hans Island :o
Title: Re: Greenland 2015 Melt Season
Post by: Nightvid Cole on July 03, 2015, 02:02:10 PM
CCI hints at a plume of 20-40mm precipitable water forming off Greenland's west coast in a week, carried in by Southerly winds. This is exactly what we saw in 2012 in the 1-2 days immediately preceding the monster melt.  :o
Title: Re: Greenland 2015 Melt Season
Post by: Paddy on July 03, 2015, 09:24:54 PM
And the melt extent is exceeding 2 SD above the mean again (http://nsidc.org/greenland-today/).

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fnsidc.org%2Fgreenland-today%2Fimages%2Fgreenland_melt_area_plot_tmb.png&hash=afe55687c0d0d588c8b1042adb71fdb2)
Title: Re: Greenland 2015 Melt Season
Post by: marcmczero on July 04, 2015, 02:10:53 AM
The Arctic GFS 7 day forecast now showing a sustained period of high pressure over Greenland. Also higher pressure spreading over the Arctic.

http://cci-reanalyzer.org/Forecasts/ (http://cci-reanalyzer.org/Forecasts/)

Am I right in thinking a major melt might be starting especially in conjunction with such high temperatures being recorded over areas that encircle the Arctic.
Title: Re: Greenland 2015 Melt Season
Post by: TenneyNaumer on July 06, 2015, 01:14:20 AM
The difference between this year and last year is really quite remarkable:

http://manati.star.nesdis.noaa.gov/ascat_images/ice_image/msfa-NHe-a-2015185.sir.gif (http://manati.star.nesdis.noaa.gov/ascat_images/ice_image/msfa-NHe-a-2015185.sir.gif)

http://manati.star.nesdis.noaa.gov/ascat_images/ice_image/msfa-NHe-a-2014185.sir.gif (http://manati.star.nesdis.noaa.gov/ascat_images/ice_image/msfa-NHe-a-2014185.sir.gif)
Title: Re: Greenland 2015 Melt Season
Post by: oren on July 06, 2015, 07:39:16 AM
The difference between this year and last year is really quite remarkable:

http://manati.star.nesdis.noaa.gov/ascat_images/ice_image/msfa-NHe-a-2015185.sir.gif (http://manati.star.nesdis.noaa.gov/ascat_images/ice_image/msfa-NHe-a-2015185.sir.gif)

http://manati.star.nesdis.noaa.gov/ascat_images/ice_image/msfa-NHe-a-2014185.sir.gif (http://manati.star.nesdis.noaa.gov/ascat_images/ice_image/msfa-NHe-a-2014185.sir.gif)

Impressive
Title: Re: Greenland 2015 Melt Season
Post by: Stephen on July 06, 2015, 09:21:47 AM
The Arctic GFS 7 day forecast now showing a sustained period of high pressure over Greenland. Also higher pressure spreading over the Arctic.

http://cci-reanalyzer.org/Forecasts/ (http://cci-reanalyzer.org/Forecasts/)

Am I right in thinking a major melt might be starting especially in conjunction with such high temperatures being recorded over areas that encircle the Arctic.

Yes, I'm wondering that too having just read Michael Hauber's post in the 2015 Melting Season Thread
Title: Re: Greenland 2015 Melt Season
Post by: wili on July 06, 2015, 10:00:16 PM
rs is now covering the record rate of melt going on on GIS right now:

https://robertscribbler.wordpress.com/2015/07/06/greenland-melt-extent-breaks-50-on-july-4-2-standard-deviation-line-shattered-yet-again/
Title: Re: Greenland 2015 Melt Season
Post by: A-Team on July 06, 2015, 11:22:26 PM
I fixed the Modis image posted by Robert S so the smoke is more clearly visible and recognizable as such (and not to be confused with ice eddies coming down the Fram). The image shows Scoresby Sund (whale's jaw) at about 71º N, so across from Jakobshavn and ~200 km up. It is not so easy to track this smoke over long distances and attribute an origin.
Title: Re: Greenland 2015 Melt Season
Post by: plinius on July 06, 2015, 11:44:02 PM
I fixed the Modis image posted by Robert S so the smoke is more clearly visible and recognizable as such (and not to be confused with ice eddies coming down the Fram). The image shows Scoresby Sund (whale's jaw) at about 71º N, so across from Jakobshavn and ~200 km up. It is not so easy to track this smoke over long distances and attribute an origin.

Though I have my doubts that one should draw a causal connection between the current smoke and the current melt. Also taking a lot of the anthropogenic soot out of the picture... the main problem is the crap that is already in the snow and coming out when the snow is melting. If you've ever been in the midwest at snow melt after a couple of weeks, you'd be tempted to mine that as a coal seam...
Title: Re: Greenland 2015 Melt Season
Post by: A-Team on July 07, 2015, 08:26:02 AM
Right, though in the dry snow zone which is most of Greenland (eg Summit @ 3,216 m), melt is so rare that there is little opportunity for concentration of impurities. A 2014 study there established that the 1889 and 2012 events were pushed into melting conditions (∼1.1 MJ m−2) by boreal forest fires (eg high black carbon + ammonia) --  the higher temperatures seen in 1785 weren't enough.

In fact, melting criteria hadn't been met since 1189. Andreas Muenchow sets the oft-muddled Holocene melt history straight at the second link, per the GISP2 core. Note a key justification for the brand new Renland ice cap core was *all* the other Greenland cores are in the unfavorable brittle ice zone for the central Holocene, so it's advisable to wait until the dust settles out on their analysis.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4050608/ (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4050608/)
http://icyseas.org/2012/07/24/record-warming-and-melting-of-greenland/ (http://icyseas.org/2012/07/24/record-warming-and-melting-of-greenland/)

I found the original link to the larger smoke image which seems to have been a featured NASA gallery image.
http://rapidfire.sci.gsfc.nasa.gov/cgi-bin/imagery/single.cgi?image=GreenlandSea.A2015184.0430.1km.jpg (http://rapidfire.sci.gsfc.nasa.gov/cgi-bin/imagery/single.cgi?image=GreenlandSea.A2015184.0430.1km.jpg)

Not knowing the height of the smoke, I looked at the wind direction at all constant pressure surfaces provided at nullschool, settling on the 700 kPa (~3500 m) as plausible for the smoke. I couldn't see how to move nullschool back four days to the date and UTC of the Modis image though surely this is stored somewhere.

A moderate anticyclone, not atypically, was circling around Greenland meaning the smoke was moving down the coast to the SW, not off into the North Atlantic. Siberia looked to be a likelier source than N Canada.

http://earth.nullschool.net/#current/wind/isobaric/700hPa/orthographic=-31.09,69.14,2028 (http://earth.nullschool.net/#current/wind/isobaric/700hPa/orthographic=-31.09,69.14,2028)
Title: Re: Greenland 2015 Melt Season
Post by: AbruptSLR on July 07, 2015, 05:56:29 PM

The linked Mashable article discusses the current high rate of ice surface melting in Greenland (see the two attached images):

http://mashable.com/2015/07/06/greenland-melt-season-speeds-up/ (http://mashable.com/2015/07/06/greenland-melt-season-speeds-up/)

Title: Re: Greenland 2015 Melt Season
Post by: Tor Bejnar on July 07, 2015, 06:28:19 PM
See the comparison of 2015 with 2012 (below map) from the Polar Portal (http://polarportal.dk/en/groenlands-indlandsis/nbsp/isens-overflade/).  The start of the melt is late, but this year may try to play catch-up.
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fpolarportal.dk%2Ffileadmin%2Fpolarportal%2Fsurface%2FSMB_combine_SM_acc_EN_20150706.png&hash=99520af48f019e45b2cdfe81d5811c29)
Title: Re: Greenland 2015 Melt Season
Post by: Paddy on July 07, 2015, 07:48:58 PM
I like that cumulative melt graph.  Very handy for getting an overall picture of the year so far.
Title: Re: Greenland 2015 Melt Season
Post by: Paddy on July 10, 2015, 12:15:02 PM
NSIDC melt extent has dipped below the 2 SD line (http://nsidc.org/greenland-today/).  Still pretty high though.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fnsidc.org%2Fgreenland-today%2Fimages%2Fgreenland_melt_area_plot.png&hash=bb4c0434cb1a81b3599cecbb2f4a6c90)

Similarly, the change in surface mass balance (http://polarportal.dk/en/groenlands-indlandsis/nbsp/isens-overflade/) is hovering around 2 SD away from the mean.  Over the year as a whole, it's still well behind 2012's big drop, though.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fpolarportal.dk%2Ffileadmin%2Fpolarportal%2Fsurface%2FSMB_curves_LA_EN_20150709.png&hash=5f6dc774966680a1e1817d6df7ea19b8)
Title: Re: Greenland 2015 Melt Season
Post by: Daniel B. on July 10, 2015, 03:08:21 PM
As evident in the graphs, the cold North Atlantic is inhibiting melt this year.  I doubt that the reent melting will enable Greenland to catch up to past years.
Title: Re: Greenland 2015 Melt Season
Post by: Nightvid Cole on July 11, 2015, 12:21:43 AM
Based on my eyeballing of today's melt from MODIS/Terra 4km, there should be an uptick when NSIDC updates tomorrow, since the melting surface area has expanded and only the region inside the orange polygons is not melting, AFAICT:

Title: Re: Greenland 2015 Melt Season
Post by: Nightvid Cole on July 11, 2015, 09:24:31 PM
Well, NSIDC melt did not go up as I expected. Their map shows high melt in the Northeast part, but not in the southern part. This is a little weird - even the ADS/VISHOP RGB suggests more melt over southern Greenland than that (though less than on July 9th.)

I wonder why these sources seem to be a bit misaligned...
Title: Re: Greenland 2015 Melt Season
Post by: Paddy on July 18, 2015, 09:33:19 AM
New monthly nsidc report released on 17th July. Apparently albedo's at a record low http://nsidc.org/greenland-today/ (http://nsidc.org/greenland-today/)
Title: Re: Greenland 2015 Melt Season
Post by: Paddy on July 29, 2015, 11:51:24 PM
Greenland melt seems to be dropping a bit:

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fnsidc.org%2Fgreenland-today%2Fimages%2Fgreenland_melt_area_plot.png&hash=bb4c0434cb1a81b3599cecbb2f4a6c90)

Meanwhile, the accumulated mass balance over the year so far has already dropped below that in the average year, but is well behind that in 2012:

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fpolarportal.dk%2Ffileadmin%2Fpolarportal%2Fsurface%2FSMB_curves_LA_EN_20150728.png&hash=99da0b7b72125830a9dfbd886efe93c9)
Title: Re: Greenland 2015 Melt Season
Post by: Paddy on August 23, 2015, 11:46:02 PM
Looks like we're almost at the end of the melt season now:

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fnsidc.org%2Fgreenland-today%2Fimages%2Fgreenland_melt_area_plot.png&hash=bb4c0434cb1a81b3599cecbb2f4a6c90)

Comparing to previous years... seems like we've been in similar territory to 2011, or slightly surpassing it, rather than the recent "rebound" years of 2013-14, or the peak melt year of 2012.  (https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fnsidc.org%2Fgreenland-today%2Ffiles%2F2015%2F01%2FGrnToday_20Jan2015_Fig3.png&hash=f9a5c9cc0e171bb3b2999a98ae0f3d7f)
Title: Re: Greenland 2015 Melt Season
Post by: sidd on August 29, 2015, 07:25:33 AM
http://nsidc.org/greenland-today/ (http://nsidc.org/greenland-today/)

Prof. Box has interesting comments on the firn aquifer, that it is draining toward the coast, but that it is spreading inland and rising toward the surface. That last little little bit worries me because not only do we have a) phase change from ice to water b) in a porous phase structure c) whose connectivity is near the percolation limit

a) is a critical triple point and c) is a critical point, we got a complicated phase transition of ice to water complicated by a transition in the structure as the solid phase melts or freezes, _but even if it didn't do that, we are at its percolation point_

I have done calculation and experiments on phase transitions in porous media, and percolation transitions in porous media, and phase transitions in porous media near the percolation point, but not one where the porous medium was one that participated in the phase transition.

The math is quite difficult, and the heat and mass transport equations must be a joy if you try to do the microscopic phase transition calculation, but perhaps renormalization flow enables one wiser than me to make helpful statements.

Dr. Fettweis has a nice page:
http://climato.be/cms/index.php?climato=2015-melt-season-over-greenland-simulated-by-mar (http://climato.be/cms/index.php?climato=2015-melt-season-over-greenland-simulated-by-mar)

sidd
Title: Re: Greenland 2015 Melt Season
Post by: Benje on September 23, 2015, 09:44:04 AM
Has the overall Greenland mass balance movement for 2015 been estimated or calculated anywhere yet as the polarportal still shows only 2014 data from GRACE


http://polarportal.dk/fileadmin/polarportal/mass/Grace_curve_La_EN_20150400.png (http://polarportal.dk/fileadmin/polarportal/mass/Grace_curve_La_EN_20150400.png)
Title: Re: Greenland 2015 Melt Season
Post by: jai mitchell on September 24, 2015, 06:28:14 AM
Has the overall Greenland mass balance movement for 2015 been estimated or calculated anywhere yet as the polarportal still shows only 2014 data from GRACE


http://polarportal.dk/fileadmin/polarportal/mass/Grace_curve_La_EN_20150400.png (http://polarportal.dk/fileadmin/polarportal/mass/Grace_curve_La_EN_20150400.png)

http://beta.dmi.dk/en/groenland/maalinger/greenland-ice-sheet-surface-mass-budget/ (http://beta.dmi.dk/en/groenland/maalinger/greenland-ice-sheet-surface-mass-budget/)
Title: Re: Greenland 2015 Melt Season
Post by: Benje on September 24, 2015, 01:00:56 PM
Thanks Jai but the figures and graphs do not include the effects of calving and so show an increase in the mass balance (before calving) as against the recent downward trend after calving, which is what I like to track.
The only data I have seen on the overall loss are the un-updated ones that I referred to.

But I am grateful for the link as I had previously failed to realise that calving was not included in those graphs and was puzzled by the positive mass balance gain versus the statements elsewhere of negative gain.

Do you have any ideas on sites showing the after-calving figures for 2015 melt season?
Title: Re: Greenland 2015 Melt Season
Post by: A-Team on September 24, 2015, 02:00:29 PM
Quote
Looks like we're almost at the end of the melt season now
Using the daily melt curve in Paddy's post for 15 April to 15 Sept and taking area under the curves (by pixel count), it turns out that 2015 was an above-average year in terms of its average melt percentage (11.1%) compared to the 1981-2010 average of 9.8%. That appears mostly attributable to higher melt from mid-June to mid-July.

In terms of localizing to key 'meltsheds' of Greenland's fast-moving glaciers during the Landsat-8 era, I would say Petermann saw far less meltwater than 2013-14, Jakobshavn was also below average but not by much, and Zachariae had quite a cold year.

It's not so easy on Jakobshavn to accurately measure ice volume calved because of never-ending revisions of ice depth at the calving front and ice stream velocity that varies both with season and across stream width; most papers content themselves with a single idealized central flowline whose speed is opportunistically assessed (path/row matched cloud-free Landsat return pairs).
Title: Re: Greenland 2015 Melt Season
Post by: Espen on September 24, 2015, 10:12:20 PM
The big difference this season was the North Western part of Greenland, where many of the outlet glaciers saw major changes (read retreat) just to mention a few: parts of Upernavik, Giesecke Isfjord, the Sverdrup "Delta" of glaciers and here especially Kjer Gletscher, and not to forget Nunatakassap Sermia a very impressive glacier placed between a rock and and a hard place!
Helheim also saw some marginal retreat.
And while we are at it Steensby Gletscher did it again against the odds!
Zachariae moved, but not the way it did in 2014.
And then of course the debatable Jakobshavn where a lot of experts came up with a lot of new measure standards of how to size a calving!!
Title: Re: Greenland 2015 Melt Season
Post by: diablobanquisa on October 08, 2015, 01:34:15 PM
GRACE data updated until July:

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fimages.meteociel.fr%2Fim%2F8182%2FGrace_combine_Sm_EN_20150700_zll3.png&hash=8741a8f97e2687b2b313ab93d904ea85)

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fimages.meteociel.fr%2Fim%2F3007%2FGrace_curve_La_DK_20150700_shb8.png&hash=fd07c1cb37efceaad717ff67d2ae2896)

http://polarportal.dk/en/groenlands-indlandsis/nbsp/total-masseaendring/ (http://polarportal.dk/en/groenlands-indlandsis/nbsp/total-masseaendring/)