Greenland 2018 melt season

[Alexander555]

As far as i understand it, the oceans are warming up. They are not cooling down. Or do you not agree with that ?

[Alexander555]

Gerontocrat, what caused that big spike in melt in the beginning of June ?

[oren]

A weather system came in, temps rose above zero over large area, the sun added its thing, and melt spiked.

[gerontocrat]

 A brief spell of very warm air coming in from the south.

ps : There will be an inland Greenland Sea when the two or three kms of ice on top have melted. We will both be dead and buried by then (as will London, New York, Shanghai, Florida etc)

[oren]

A brief spell of very warm air coming in from the south.

ps : There will be an inland Greenland Sea when the two or three kms of ice on top have melted. We will both be dead and buried by then (as will London, New York, Shanghai, Florida etc)

And when arctic sea ice area actually increases in winter because of that, the deniers will say we are recovering...

[Alexander555]

There was more snow this winter. So the flow of meltwater was also bigger. And probably that meltwater  is colder than the seawater. And it's fresh water. So maybe the toplayer of the sea in that area, or the water just below the ice, for the places where there was ice. Was colder than normal or a bigger area than normal. That can explain why the melt at Greenland stayed below average for a while. But why that unusual big spike ? Maybe the warmer water just builded up below that colder layer. And there was more easy ice to melt, because it was delayed. And probably some warm winds from that warm area in the Atlantic . And more melt than normal , normaly caused a bigger flow of meltwater at Greenland, so the melting dropped again. But normaly the big flows of meltwater should be gone now, and that hot area in the Atlantic is still there.

[Tor Bejnar]

As far as i understand it, the oceans are warming up. They are not cooling down. Or do you not agree with that ?

Read 'all about' the Arctic Ocean Cold Blob in Wikipedia
Yes, the Atlantic is warming. But yes, there is a cold blob southeast of southern Greenland.  (This image shows cold blob in the Labrador Sea as well.)

[Brigantine]

When we're talking about how "melt" spiked, can we distinguish between
1) a large area of 1+mm of melt, and
2) a large mass or volume of melt, even if it mostly occurs within a small area.

From those graphs, it looks like a wide area experienced some small amount of melting, but the amount of ice that actually melted by mass or volume was underwhelming and net SMB hasn't actually decreased yet. Calling that a spike in melt is a misleading description.

[oren]

Yes. It's important to understand what the numbers and graphs mean, and what they don't mean.
From the DMI website:

These two maps show the area on the Greenland Ice Sheet where melt has occurred on the previous two days. The figure is shaded red where the model indicates melt of more than 1 mm / day. The total percentage of the ice sheet where melt has occurred is written at the top of the map.

The graph to the right of the maps shows the percentage of the area of the Greenland ice sheet that has melted every day this season on the blue curve. This can be compared with the dark grey curve that is the average melt area over the period of 1981-2010. The light grey band shows the differences from year to year as the range of each day through this period leaving out the most extreme high and low values each day.

This melt map only shows areas where melt has happened. It does not include evaporation directly from the ice sheet surface or show how much snow and ice has melted. Much of the melt water will refreeze in the surface snow layers rather than running off the ice sheet, this process is included in the calculations of surface mass balance which is why the melt area appears different to the surface mass balance plots above.

[gerontocrat]

(https://www.dmi.dk/en/groenland/maalinger/greenland-ice-sheet-surface-mass-budget/)

Images as at 24th June attached..

Melt continues though now down to just a bit above average , precipitation average to low, but SMB in minimal or zero decline.

June has been an odd month so far. Until the end of May accumulated SMB was looking really average. Then despite higher than average daily melt  accumulated SMB is now 50+ gt above average.

To add to comments above about the melting simply meaning 1+mm of observed melt on the day, the melt since it began (early) has been concentrated on both the southern east and west coastal areas (as one would expect). 1+ mm per day for (say 20) days means 20+ mm of cumulative melt of which some must result in run-off in the direction of the sea. I wonder how much effect that has on the glaciers at the coastal fringe ?

ps:- the Arctic melting season has also slowed in June.

[RoxTheGeologist]

There are already places much further north where there is no snow or ice at this moment. And if the hot blob in the Atlantic becomes permanent. Than why should we not get a little sea in Greenland ? Juan C posted the pic a couple months ago.

Note that this is the current basal topography. Greenland will endure post glacial rebound as the ice sheet melts. For each km of ice, expect the topography to raise by about 300m - 400m (effectively you replace the mass of the ice removed by the same mass of rock, it depends on the density of the rock). The thickest parts of ice sheet are about 3km, so one would expect around a km of uplift.

I'd imagine the ice cut valleys and lakes will be spectacular, but there is unlikely to be a sea.

[Alexander555]

When we're talking about how "melt" spiked, can we distinguish between
1) a large area of 1+mm of melt, and
2) a large mass or volume of melt, even if it mostly occurs within a small area.

From those graphs, it looks like a wide area experienced some small amount of melting, but the amount of ice that actually melted by mass or volume was underwhelming and net SMB hasn't actually decreased yet. Calling that a spike in melt is a misleading description.

Maybe my interpretation is a little wrong. But than you can tell me what the blue spike represents. Because it looks like a spike. It goes from almost zero to almost the double of what it normaly is at that time. I understand what the red in the left picture means. I'm not sure what the blue line on the other pic represents. The scale on the left side indicates 100 on the top. So is it a % of the total surface that is melting. Or is it a volume .......?

[Alexander555]

It's ok, i see it. The blue line is for the % we have today. The 25 %.

[oren]

Correct. And it's the % of the surface in melting condition. Wet top.

[gerontocrat]

https://www.dmi.dk/en/groenland/maalinger/greenland-ice-sheet-surface-mass-budget/

2017-18 Year to June 30

In June, despite a spike in melt as a % of area, Surface Mass Balance did not decline until very late in the month. As a result, SMB is 75+GT above the average for the time of year. Arctic Sea Ice melt also slowed down markedly in June though may have picked up in the last week.

On average there are just 2 months left for the Greenland SMB to continue to reduce (i.e. melt).

[gerontocrat]

https://www.dmi.dk/en/groenland/maalinger/greenland-ice-sheet-surface-mass-budget/

As at 4th July 2018

In the first 2 weeks of June a spike in melt as a % of area made me think perhaps a lively melt season was upon us. But no. melt has been at or near average consistently since then. Slightly above average precipitation also meant Surface Mass Balance did not decline until very late in the month.

SMB is now approaching 100 GT above the average for this date. This below average melt mirrors that of Arctic Sea Ice extent and area.

On average there are just under 2 months left for the Greenland SMB to continue to reduce (i.e. melt).

[gerontocrat]

Interesting contrast between NSIDC and DMI.

[mostly_lurking]

Interesting contrast between NSIDC and DMI.

Does NSIDC also use the >1mm criteria ?

[gerontocrat]

Interesting contrast between NSIDC and DMI.

Does NSIDC also use the >1mm criteria ?

I always thought so but having just read all the notes on https://nsidc.org/greenland-today/ and the links -I don't know. Well well.

[gerontocrat]

https://www.dmi.dk/en/groenland/maalinger/greenland-ice-sheet-surface-mass-budget/

As at 8th July 2018

SMB is now 100 GT above the average for this date. This below average melt mirrors that of Arctic Sea Ice extent and area. On average there are just under 2 months left for the Greenland SMB to continue to reduce (i.e. melt).

Last year the story was about SMB increasing above average. This year so far it turning out to be the same story.

[Darvince]

Does NSIDC also use the >1mm criteria ?

I always thought so but having just read all the notes on https://nsidc.org/greenland-today/ and the links -I don't know. Well well.

This is pure speculation on my part, but I have noticed that the product "RGB (36V,36H,18V)" on JAXA shows white on the Greenland sheet in the same places at the same time as NSIDC's melting pixels.

[gerontocrat]

Does NSIDC also use the >1mm criteria ?

I always thought so but having just read all the notes on https://nsidc.org/greenland-today/ and the links -I don't know. Well well.

This is pure speculation on my part, but I have noticed that the product "RGB (36V,36H,18V)" on JAXA shows white on the Greenland sheet in the same places at the same time as NSIDC's melting pixels.

In addition, https://nsidc.org/greenland-today/ in its 2016-2017 analysis refers to and make use of DMI's SMB data. I can't see NSIDC not noting any significant difference in how they measure this stuff.
So my answer is yes, unless proved otherwise.

ps: NSIDC's analysis of last year and the data in the links are well worth reading.
pps: Greenland ice Mass loss video attached. Sooper-dooper.

[gerontocrat]

https://www.dmi.dk/en/groenland/maalinger/greenland-ice-sheet-surface-mass-budget/

As at 11th July 2018

SMB is now about 110 GT above the average for this date, the anomaly  increasing at around 4 to 6 Gt per day over the last week. This below average SMB loss mirrors that of the Arctic Sea Ice extent. On average there are under 50 days left for the Greenland SMB to continue to reduce (i.e. melt).

Last year the story was about SMB increasing above average. This year so far it turning out to be the same story, but for a totally different reason - last year being from large winter and spring snow fall, this year from lack of melt.

[gerontocrat]

https://www.dmi.dk/en/groenland/maalinger/greenland-ice-sheet-surface-mass-budget/

As at 13th July 2018

Melt increased to above average, and so has precipitation. Result is loss of SMB continues well below average.

Last year the story was about SMB increasing above average (see last graph attached). This year so far it may turn out to be the same story at the end, but for a totally different reason - last year being from large winter and spring snow fall, this year from lack of melt in the last 2-3 months of the brief arctic summer.

[Darvince]

No remarkable melting area increase, but first "big" melting loss of the year per DMI:

[gerontocrat]

No remarkable melting area increase, but first "big" melting loss of the year per DMI:

Low precipitation combined with above average melt percent did the trick. But I think precipitation will be higher again over the next few days. (and after that Greenland is looking dry). But how much will be rain and how much snow, and I don't know how DMI calculates how much rain stays on the ice sheet and how much runs off and increases mass loss to the sea.

[mostly_lurking]

Last+this year mass budget in one pic.

[gerontocrat]

https://www.dmi.dk/en/groenland/maalinger/greenland-ice-sheet-surface-mass-budget/

As at 17th July 2018


Since the end of May, melt has been mostly at or (as now) well above average. Nevertheless, since that date Surface Mass Balance (SMB) has barely reduced at all. Indeed, SMB is approaching 150 GT above the 30 year average. With melt above average, there can be only once cause - precipitation since the end pof may well above average.

In contrast, although last year the story was also about SMB increasing well above average. it was for a totally different reason - last year being from large winter and spring snow fall.

On average there are now well under 50 days left for the Greenland SMB to reduce (i.e. melt).

[oren]

Last+this year mass budget in one pic.

Don't forget this is not the whole mass budget, and therefore it's not necessarily correct to combine the two years. This is only the surface mass balance - precipitation and top melt, but does not include calving and terminus melting.
Of course, its still very good news that the SMB anomaly is positive in the last couple of years. It just doesn't mean that the GIS mass actually increased by these numbers. Here's a chart updated to Jan 2017 of the net measured GIS mass change.

[gerontocrat]

Last+this year mass budget in one pic.

Clever-clogs!

[gerontocrat]

Last+this year mass budget in one pic.

Don't forget this is not the whole mass budget, and therefore it's not necessarily correct to combine the two years. This is only the surface mass balance - precipitation and top melt, but does not include calving and terminus melting.

It is important for people to read the full screed on https://www.dmi.dk/en/groenland/maalinger/greenland-ice-sheet-surface-mass-budget/

I came across a denier elsewhere (or was it a stray who drifted into the ASIF?) using this data to claim Greenland was accumulating ice.
 
Just think, Oren, we may be getting GRACE follow-on data by the end of 2018 or at latest Spring 2019. The at will be very interesting.

[oren]

We may be getting GRACE follow-on data by the end of 2018 or at latest Spring 2019. The at will be very interesting.

Very interesting indeed, especially as the DMI data is derived from a model, while GRACE measures the actual ice sheet mass (with some uncertainty of course). And especially as it seems there has been a bit of a slowdown in Greenland calving activity (at least judging by Jakobshavn and by the number of new posts in the Greenland sub-forum).

[mostly_lurking]

Of course, its still very good news that the SMB anomaly is positive in the last couple of years. It just doesn't mean that the GIS mass actually increased by these numbers. Here's a chart updated to Jan 2017 of the net measured GIS mass change.

1 ) I'm happy that somebody here is happy when the ice doesn't melt   Quite rare.
2)  Is the data on that graph updated only till Jan 2017 because of GRACE?

[oren]

Of course, its still very good news that the SMB anomaly is positive in the last couple of years. It just doesn't mean that the GIS mass actually increased by these numbers. Here's a chart updated to Jan 2017 of the net measured GIS mass change.

1 ) I'm happy that somebody here is happy when the ice doesn't melt   Quite rare.
2)  Is the data on that graph updated only till Jan 2017 because of GRACE?

1. The psychology of ASIF surfing is rather complex... but one must be able to tell good from baf.
2. Honestly I just did a quick google image search, and picked the latest one I could find, but quite possibly it's related to lack of GRACE data.

[gerontocrat]

Of course, its still very good news that the SMB anomaly is positive in the last couple of years. It just doesn't mean that the GIS mass actually increased by these numbers. Here's a chart updated to Jan 2017 of the net measured GIS mass change.

1 ) I'm happy that somebody here is happy when the ice doesn't melt   Quite rare.
2)  Is the data on that graph updated only till Jan 2017 because of GRACE?

1. The psychology of ASIF surfing is rather complex... but one must be able to tell good from baf.
2. Honestly I just did a quick google image search, and picked the latest one I could find, but quite possibly it's related to lack of GRACE data.

The GRACE satellites lasted well belong their design life - it was going to be a once off. But the data it collected, of which Arctic and Antarctic Ice loss was but a fraction, spawned over 6,000 scientific papers. Real data - not models.

But the satellites decayed and were finally retired and sent to oblivion in summer 2017. The new GRACE project is looking fabulous - the new technology on board is awesome.

https://gracefo.jpl.nasa.gov/

[mostly_lurking]

.
2. Honestly I just did a quick google image search, and picked the latest one I could find, but quite possibly it's related to lack of GRACE data.

So in the best 2 positive years in Greenland in a long while we don't really have any idea what the situation is. After last year I think I saw the were saying "We think" that there was a small net positive (instead of the assumed usual 200GT yearly loss).

[S.Pansa]

So in the best 2 positive years in Greenland in a long while we don't really have any idea what the situation is. After last year I think I saw the were saying "We think" that there was a small net positive (instead of the assumed usual 200GT yearly loss).

Some ideas are out there, for instance the 2017-season-summary from the DMI:

At the end of the SMB year that started on the 1st September 2016 and went through to the 31st August 2017, and not including the loss of icebergs, about 544 Gt more snow fell on the surface of the ice sheet than melted and ran into the ocean, compared to an average for 1981 to 2010 of about 368 Gt at the same point in the year.  ... Greenland on average loses around 500 Gt of ice each year from calving and submarine melt processes. If we subtract this from our figure of 544 Gt for the SMB it would suggest Greenland gained a small amount of ice this year.

Even more interesting perhaps the Arctic report Card by NOAA:

GRACE satellite gravity estimates obtained following Velicogna et al. (2014) and Sasgen et al. (2012), available since 2002, indicate that between April 2016 and April 2017 (the most recent 12-month period of reliable data) there was a net ice mass loss of 276 ± 47 Gt (Fig. 3; 2-sigma uncertainty). The 2016-2017 net loss is greater than the April 2015-April 2016 mass loss (191 ± 28 Gt, see Arctic Report Card 2016) and close to the average April-to-April mass loss (255 ± 7 Gt) for 2003-2017 (Sasgen et al., 2012). The updated trends of total ice mass loss for the 15-year GRACE period are, respectively, 264 Gt/yr (Velicogna et al., 2014), and 270 Gt/yr (Sasgen et al., 2012).

See also the attached figure 3.
The difference might stem from the different timeframes (Sept-August vs. April-April)

[gerontocrat]

https://nsidc.org/greenland-today/
https://www.dmi.dk/en/groenland/maalinger/greenland-ice-sheet-surface-mass-budget/

2018 Melting Season Data

While SMB net loss is lower than average, melt itself is quite impressive.

[mostly_lurking]

On the melt-map they show melting in areas where there was -5c and lower. How is that logical? Even if it did it for some reason it would freeze right up.

[gerontocrat]

On the melt-map they show melting in areas where there was -5c and lower. How is that logical? Even if it did it for some reason it would freeze right up.

Perhaps the sun was shining. How DMI's (and NSIDC's) algorithms work is certainly a mystery to me, and maybe (like Microsoft Windows) not totally understood by anybody.

Hence we need the magic of the new GRACE follow-on to give us real physical data.

[Phil.]

On the melt-map they show melting in areas where there was -5c and lower. How is that logical? Even if it did it for some reason it would freeze right up.

As DMI say:
" The snow and ice model from one of DMI’s climate models is driven every six hours with snowfall, sunlight and other parameters from a research weather model for Greenland, Hirlam-Newsnow, and since 1 July 2017 the HARMONIE-AROME weather model. We can thereby calculate the melting energy, refreezing of melt water and sublimation (snow that evaporates without melting first)."

So they allow for refreezing.  In the places you refer to it could either be melting due to sunlight and evaporating or could be sublimating.

[gerontocrat]

https://www.dmi.dk/en/groenland/maalinger/greenland-ice-sheet-surface-mass-budget/

As at 23rd July 2018


At the moment, melt is below average, and precipitation is also low. Net effect is SMB loss a bit below average. As a result, current SMB continues to approach 150 GT above the 30 year average.

In contrast, although last year the story was also about SMB increasing well above average. it was for a totally different reason - last year being from large winter and spring snow fall.

On average there are now well under 50 days left for the Greenland SMB to reduce (i.e. melt).

[mostly_lurking]

On average there are now well under 50 days left for the Greenland SMB to reduce (i.e. melt).

Looking at the graphs it looks like 30 days or less of possible SMB reduction. There is a bit of melting in September but mostly negated by the incoming snow. Last year SMB decline stopped around Aug 10th

[gerontocrat]

https://www.dmi.dk/en/groenland/maalinger/greenland-ice-sheet-surface-mass-budget/

As at 26 July 2018


When melt is high, precipitation seems also mostly above average. When melt is low, precipitation is often higher than average, but not by much. SMB was supposed to be on the decline since the beginning of June. Apart from one, maybe two days, SMB decline has been persistently below average. As a result, current SMB looks like it is now 150 GT above the 30 year average.

In contrast, although last year the story was also about SMB increasing well above average. it was for a totally different reason - last year being from large winter and spring snow fall.

On average there are now, on average, only  about 20 days left for the Greenland SMB to reduce (i.e. melt). Of course, there may be surprises to come.

[gerontocrat]

https://www.dmi.dk/en/groenland/maalinger/greenland-ice-sheet-surface-mass-budget/

As at 29 July 2018

Commentary mostly unchanged.

When melt is high, precipitation seems also mostly above average. When melt is low, precipitation is often higher than average, but not by much. SMB was supposed to be on the decline since the beginning of June. Apart from one, maybe two days, SMB decline has been persistently below average. As a result, current SMB looks like it is now more than 150 GT above the 30 year average.

Maybe a large melt happening Monday  Tuesday, and maybe less precipitation forecast - that could change things a bit.

In contrast, although last year the story was also about SMB increasing well above average. it was for a totally different reason - last year being from large winter and spring snow fall.

On average there are now, on average, only about 17 days left for the Greenland SMB to reduce (i.e. melt). Of course, there may be surprises to come.

(I wonder when NASA will start giving us ice-sheet mass data from GRACE follow-on - testing must be nearing the end).

[mostly_lurking]

...snip
(I wonder when NASA will start giving us ice-sheet mass data from GRACE follow-on - testing must be nearing the end).

As the conspiracy theory nut I predict when they do start giving new data there will be a sudden jump to the the worse (less ice mass)-"It's much worse than we thought!!"
 

[gerontocrat]

https://www.dmi.dk/en/groenland/maalinger/greenland-ice-sheet-surface-mass-budget/

As at 31 July 2018

Commentary mostly unchanged.

When melt is high, precipitation seems also mostly above average. When melt is low, precipitation is often higher than average, but not by much. SMB was supposed to be on the decline since the beginning of June. Apart from one, maybe two days, SMB decline has been persistently below average. As a result, current SMB looks like it is now more than 150 GT above the 30 year average.

A large melt did happen Monday (40%) & Tuesday (46% highest for year to date), with less precipitation - that did change things a bit - another day, making two days sine June 1, where SMB loss was above average. Note also the intensity of melt on the WEST coast - effect on glaciers?

In contrast, although last year the story was also about SMB increasing well above average. it was for a totally different reason - last year being from large winter and spring snow fall.

On average there are now, on average, only about 15 days left for the Greenland SMB to reduce (i.e. melt). Of course, there may be surprises to come.

I wonder when NASA will start giving us ice-sheet mass data from GRACE follow-on - testing must be nearing the end.

Note: GRACE gives the change in Ice-Sheet Mass, which is SMB gain less Glacial Calving loss. The assumption is that SMB gain in the DMI Sept-Aug year is about 400GT, and calving loss about 600GT on average, giving a net annual Ice Sheet Mass loss of about 200 GT. GRACE data to 2017 showed that net mass loss was increasing substantially over time.

So SMB is just half the story. We need the other half.

[oren]

The Greenland melt does feel (similar to 2017) much more subdued than previous years. If true it's very good news as it buys us time (that we currently squander). GRACE will tell, hopefully soon.

[mostly_lurking]

Note: GRACE gives the change in Ice-Sheet Mass, which is SMB gain less Glacial Calving loss. The assumption is that SMB gain in the DMI Sept-Aug year is about 400GT, and calving loss about 600GT on average, giving a net annual Ice Sheet Mass loss of about 200 GT. GRACE data to 2017 showed that net mass loss was increasing substantially over time.

So SMB is just half the story. We need the other half.

Except last year which was about even or slight gain if I remember.

[gerontocrat]

Note: GRACE gives the change in Ice-Sheet Mass, which is SMB gain less Glacial Calving loss. The assumption is that SMB gain in the DMI Sept-Aug year is about 400GT, and calving loss about 600GT on average, giving a net annual Ice Sheet Mass loss of about 200 GT. GRACE data to 2017 showed that net mass loss was increasing substantially over time.

So SMB is just half the story. We need the other half.

Except last year which was about even or slight gain if I remember.

As we will never have GRACE data for 2017 or most of 2018 then the best that can be hoped for is an interpolation of the GRACE early 2017 and the GRACE follow-on late 2018 data. But yes, the DMI 2017 report says 2017 likely zero +/- a bit depending on glacial calving.

But after that, if one can get the daily SMB data from DMI, one should be able to see SMB gain/loss vs losses from calving at various points through the year. That would be interesting.