Cryosphere > Greenland and Arctic Circle

Greenland 2014 Melt Season

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The melt continues across Greenland, with DMI showing the SMB daily loss for 16/6 increasing to almost 4Gt (a new YTD record), despite increased precipitation across the southern peninsula.

The high melt area on the NSIDC site (30% and still on the way up) is already higher than anything seen until July last year, but its not on the scale of 2012 yet, which hovered around 40% for most of June and July with the huge peak of 90% of the ice sheet showing melt in July 2012.

Because of the recalibration it's difficult to compare the DMI values. Their 2013 values were more or less matching 2012 throughout June, with an 8Gt daily SMB loss around now.

I have three questions which are of general nature, but also affect the amount of water discharge from Greenland somewhat, so i hope it's OK if i ask them here.

At , i read that bedrock temperature in central Greenland is "somewhat higher" than -13C.

1. How much is "somewhat"?
2. Is there any near-real-time monitoring of bedrock temperatures in Greenland, with data being available to public?
3. Is there any maps for how deep (in meters) Greenland permafrost is?

With the melt going like it does right now and like it did 2 years ago, bedrock temperatures are to increase (with all the water going under the ice sheet, it's inevitable). The big reason behind my interest is not this melt season (it's secondary), - but the possible scenario of ice sheet itself (most of it) eventually sliding down into the ocean, once bedrock temperatures are high enough (as long as it's below ~0C widely enough, the bedrock itself will keep being freezed "into" the ice sheet, preventing it from moving anywhere; but with above 0C temperatures deep enough under the surface - geo gradient they call it, do they? - and with above 0C water coming from above from melts, sooner or later bedrock will happen to get above 0C for most of its surface, i guess, and then much/most of ice sheet may just slide down - amount of potential energy all that ice has due to being that high above sea level - is tremendous).

The first record domino of the 2014 melting season is down.

Weather station KPC_U, which located in the north easternmost corner of Greenland not far from Zachariae Isstrøm, is reporting that 16. June 2014 saw a peak temperature of 5,73 C, which happens to be the highest temperature recorded since the station begun operating in 2008.

One might argue this isn't the record that will be discussed the most by generations to come, but it is never the less a record :D.

to answer your questions, F. Tnioli,

1. ice core temperatures suggest bedrock temperatures around -10 to -13 degrees at some points
That ist important, because you only have some few points where the temperature is known. It is not very likely that the bedrock is colder, because ice is a very good thermal insulator. it is much more likely that temperature are around minus 2 to minus 5 degrees at many points because oft the heat flow inside the bedrock. (geothermal gradient)

2. No, as long as i know there are no continuous measurements of bedrock temperatures.  This is not necessary either, because the temperature will not exceed a temperature around the melting point of water which is dependent of the overlying pressure and i guess this will be the bedrock temperature  at many points. Melting at these point is only possible due to geothermal heat flow. Meltwater from above will certainly be in thermal equilibrium in this deep due to heat exchange under its way.

3. No, you cant measure it due to far too much ice overlaying the bedrock, but i guess that at most places there will not be much permafrost under the ice shield due to geothermal heat flow.

4. (which you did not ask) The entire ice cap can not just slide downhill, because Greenlands bedrock topography is like a salad bowl, very deep down in the middle (600 m under Sea level) and Mountains around it. Extraction of the ice is only possible through outlet glaciers like Peterman, Zachariae (see this forum) or others or surface melting. Water percolating down will not have above 0 temperatures but exact 0 degrees. It will eventually refreeze inside the ice shield, and warming it from inside, but not melting it. The important fact about this heat accumulation inside the ice shield is, that the viscosity of the ice is very strong dependent of the temperature. The warmer it is, the faster the glaciers are moving.

NSIDC Melt area has increased to around 35% well over the 2sd area. Melt is around all the coasts, and across the saddle between the north and south sheets.


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