At last! Greenland research confirms common sense

We've been told for years that the Greenland ice-sheet is "melting faster than expected", so contributing more meltwater to sea-level rise. We've been told that meltwater percolates to the base of glaciers, providing lubrication that speeds up movement of the ice towards the sea. This last claim has always seemed to me to be counter-intuitive - glaciers may be melting at the surface in summer, but surely the ice temperature drops with depth? Surely the meltwater would freeze before it reached the rock at the base of the ice? It seems that simple common sense backed by actual research (none of the "experts" postulating meltwater lubrication had taken any measurements) has triumphed over scientific supposition. A paper published in Nature just over a week ago (9th. November 2012) is revealingly titled Greenland ice-sheet contribution to sea-level rise buffered by meltwater storage in firn (J. Harper, N. Humphrey, W. T. Pfeffer, J. Brown & X. Fettweis). The abstract reads

Surface melt on the Greenland ice sheet has shown increasing trends in areal extent and duration since the beginning of the satellite era. Records for melt were broken in 2005, 2007, 2010 and 2012. Much of the increased surface melt is occurring in the percolation zone, a region of the accumulation area that is perennially covered by snow and firn (partly compacted snow). The fate of melt water in the percolation zone is poorly constrained: some may travel away from its point of origin and eventually influence the ice sheet’s flow dynamics and mass balance and the global sea level, whereas some may simply infiltrate into cold snow or firn and refreeze with none of these effects. Here we quantify the existing water storage capacity of the percolation zone of the Greenland ice sheet and show the potential for hundreds of gigatonnes of meltwater storage. We collected in situ observations of firn structure and meltwater retention along a roughly 85-kilometre-long transect of the melting accumulation area. Our data show that repeated infiltration events in which melt water penetrates deeply (more than 10 metres) eventually fill all pore space with water. As future surface melt intensifies under Arctic warming, a fraction of melt water that would otherwise contribute to sea-level rise will fill existing pore space of the percolation zone. We estimate the lower and upper bounds of this storage sink to be 322±44 gigatonnes and 1,285(+388-262) gigatonnes, respectively. Furthermore, we find that decades are required to fill this pore space under a range of plausible future climate conditions. Hence, routing of surface melt water into filling the pore space of the firn column will delay expansion of the area contributing to sea-level rise, although once the pore space is filled it cannot quickly be regenerated.

Co-author Neil Humphrey of Wyoming University is quoted in the university news sheet

“We’re not saying Greenland is not melting,” Humphrey says. “What we’re saying is it will be one to two decades longer before we start seeing the melt.”

That’s because Humphrey and other researchers’ data -- collected on the western flank of the Greenland Ice Sheet from 2007-2009 -- shows that the water generated by repeated recent melt events penetrates deeply into the snow and firn (partially compact snow). This fills the pore space and diminishes the amount of meltwater that actually runs off into the ocean.

As future surface melt intensifies due to Arctic warming, a fraction of meltwater -- that would otherwise add to the rise in sea levels -- fills tens of meters of existing pore space of the percolation zone. The percolation zone is a region of the accumulation area that is perennially covered by snow and firn, Humphrey says.

What happens to the water that "penetrates deeply into the snow and firn"?

“The snow is so deep and so cold that, even though it’s melting, the melt infiltrates into the lower, colder snow and refreezes,” Humphrey says. “We calculate there is one to two decades of pore space within the snowpack. You get denser snowpack. After 10 or 20 years, it (the pore space) fills up.”

However, after this healthy dose of science, the prof. drops into the realm of fantasy (is he concerned about protecting his funding?)

“While other people (scientists) are predicting up to a one-half foot sea rise by 2050, we’re actually saying our data shows that any rise that will occur will be delayed by one or two decades,” says Humphrey of the paper he termed as “controversial.” “A half-foot rise is significant. Half of Florida would be under water. New Orleans would be gone.”

A "half-foot" is of course six inches, or 15 cm. Is he really suggesting that half of Florida is just 15 cm above current high tides? Just when I thought that scientists were abandoning advocacy in favour of traditional research and actual fact.....

Making it up (1) - "Study finds Greenland's ice cover is sliding into the ocean"

This is the start of a new series to run in parallel with "Disconnects in Logic". Both have and will be a source of amusement and debunking hyperbole, unjustified conclusions and predictions, and plain outright lies at the same time.

"Click Green" (you're ahead of me, I can tell) trumpets the apocalyptic headline "Study finds Greenland's ice cover is sliding into the ocean" . The contradiction between headline and article is striking - it's becoming common when the environment, wildlife, "climate change" or "global warming" are discussed, or new research summarised. Apart from the fact that most of the Greenland ice sheet covers the depressed interior of the landmass, and has as much chance of "sliding into the ocean" as a pool ball in a pocket has of "sliding onto the table", what does the first paragraph actually say?

Like snow sliding off a roof on a sunny day, the Greenland Ice Sheet may be sliding faster into the ocean due to massive releases of meltwater from surface lakes, according to a new study by the University of Colorado Boulder-based Cooperative Institute for Research in Environmental Sciences.

As usual, the caveat is "may be", which as so often is the case in alarmist articles, becomes "is" in the headline.

During a typical catastrophic lake drainage, about 1 million cubic meters of meltwater - which is equivalent to the volume of about 4,000 Olympic swimming pools - funnels to the ice sheet's underside within a day or two. Once the water reaches the ice sheet's belly that abuts underlying rock, it may turn the ice-bed surface into a Slip 'N Slide, lubricating the ice sheet's glide into the ocean. This would accelerate the sea-level rise associated with climate change.

Alternatively, however, the lake drainages may carve out sub-glacial "sewers" to efficiently route water to the ocean. "This would drain the ice sheet's water, making less water available for ice-sheet sliding," Colgan said. That would slow the ice sheet's migration into the ocean and decelerate sea-level rise.

"Alternatively, however..." means they don't know, and what's more, the researchers openly admit it.

"Lake drainages are a wild card in terms of whether they enhance or decrease the ice sheet's slide," Colgan said. Finding out which scenario is correct is a pressing question for climate models and for communities preparing for sea-level change, he said.

So they, we, (and the "Click Green" author) don't actually know what's happening. All that is known is that the meltwater "lakes" suddenly disappear, and it's assumed they've drained away. I say assumed, because

For the study, the researchers developed new feature-recognition software capable of identifying supraglacial lakes in satellite images and determining their size and when they appear and disappear. "Previously, much of this had to be double-checked manually," Colgan said. "Now we feed the images into the code, and the program can recognize whether a feature is a lake or not, with high confidence and no manual intervention."

If such a lake "disappears" then, it might be because the water's drained away, as postulated, or possibly it's refrozen, and wouldn't be recognised by the software. First they don't know what the drainage mechanism is, whether meltwater is actually "lubricating" the base of the ice, and the real "sceptic in the room", don't even know if the lake hasn't simply refrozen. Headline fail, alarmism alert, interesting study, shame about the lack of any firm conclusions.

I really aught to start a third new series "Displaying Your Ignorance", 'cos I LOL when I saw this "schoolboy howler" on redOrbit - "Greenland Slipping Away"

Massive releases of meltwater from surface lakes may be causing Greenland to slide ever faster into the ocean, according to a new study by the University of Colorado Boulder-based Cooperative Institute for Research in Environmental Sciences (CIRES).

What's Greenland sliding on I wonder, Santa's Sleigh? Hold on tight, Greenlanders! Wheeee!

The Guardian shows its naked bias

The Himalayas and nearby peaks have lost no ice in past 10 years, study shows

"Meltwater from Asia's peaks is much less then previously estimated, but lead scientist says the loss of ice caps and glaciers around the world remains a serious concern"

The Grauniad (an affectionate, or otherwise, nickname for the Guardian, which in the days of movable type was prone to side-splitting typos) may sometimes display an apparent lack of bias in its reporting of environmental and climate science, but a sceptical eye can often spot the face behind the mask. It's so with the above article. Those worried or even alarmed about apparent (I choose the word with care) ice-loss worldwide should rejoice in the news about Himalayan ice. I see no rejoicing here; indeed there's a whiff of disappointment throughout.

There's an obligatory picture of a an (apparently) melting glacier with this caption:

Hopar glacier in Pakistan. Melting ice outside the two largest caps - Greenland and Antarctica - is much less then previously estimated, the study has found.

That only interpretation I can put on that is that ice loss in Greenland and Antarctica is not "much less then previously estimated", but must be the same or more than previously estimated. However, the article, by omission, implies that the study didn't cover Greenland and Antarctica. The Grauniad agonises over melting icecaps, so why didn't they mention that the study was global? Perhaps it's that the study also revised estimates for Greenland and Antarctica - downwards from IPCC estimates, but similar to more recent estimates. Was the Grauniad disappointed?

Here's where their bias is revealed. We have what is being widely acknowledged as the most reliable estimates to date for the Himalayas

However, the scientist who led the new work is clear that while greater uncertainty has been discovered in Asia's highest mountains, the melting of ice caps and glaciers around the world remains a serious concern.

Are they really saying that the study reveals "greater uncertainty"? Check it out -

Recent contributions of glaciers and ice caps to sea level rise
Thomas Jacob John Wahr W. Tad Pfeffer Sean Swenson
Nature (2012)

Here's the abstract:

Glaciers and ice caps (GICs) are important contributors to present-day global mean sea level rise. Most previous global mass balance estimates for GICs rely on extrapolation of sparse mass balance measurements representing only a small fraction of the GIC area, leaving their overall contribution to sea level rise unclear. Here we show that GICs, excluding the Greenland and Antarctic peripheral GICs, lost mass at a rate of 148±30 Gt/yr from January 2003 to December 2010, contributing 0.41±0.08 mm/yr to sea level rise. Our results are based on a global, simultaneous inversion of monthly GRACE-derived satellite gravity fields, from which we calculate the mass change over all ice-covered regions greater in area than 100 km2. The GIC rate for 2003–2010 is about 30 per cent smaller than the previous mass balance estimate that most closely matches our study period. The high mountains of Asia, in particular, show a mass loss of only 4±20 Gt/yr for 2003–2010, compared with 47–55 Gt/yr in previously published estimates. For completeness, we also estimate that the Greenland and Antarctic ice sheets, including their peripheral GICs, contributed 1.06±0.19 mm/yr to sea level rise over the same time period. The total contribution to sea level rise from all ice-covered regions is thus 1.48±0.26 mm/yr, which agrees well with independent estimates of sea level rise originating from land ice loss and other terrestrial sources.

"Most previous global mass balance estimates for GICs rely on extrapolation of sparse mass balance measurements representing only a small fraction of the GIC area, leaving their overall contribution to sea level rise unclear" - that's where the uncertainty was. I hope the Guardian writers' disappointment doesn't last - there's bound to be some natural disaster or extreme weather event soon soon to give an opportunity to wheel out and polish their now time-worn and expected phrase "while it's not possible to ascribe any particular event to [global warming|climate change|rising sea levels] (choose one)" ..... and go on to effectively do just that. Good old Grauniad - at least they're predictable, unlike climate or weather.

So predictable, in fact, that they have to wheel out a Bristol University glaciologist, Prof Jonathan Bamber:

"I believe this data is the most reliable estimate of global glacier mass balance that has been produced to date," said Bamber. He noted that 1.4 billion people depend on the rivers that flow from the Himalayas and Tibetan plateau: "That is a compelling reason to try to understand what is happening there better."

He added: "The new data does not mean that concerns about climate change are overblown in any way. It means there is a much larger uncertainty in high mountain Asia than we thought. Taken globally all the observations of the Earth's ice – permafrost, Arctic sea ice, snow cover and glaciers – are going in the same direction."

Notice that? He says that "the most reliable estimate of global glacier mass balance that has been produced to date" means that "there is a much larger uncertainty in high mountain Asia than we thought". Silly me thought that reliable estimates reduced uncertainty. It just proves that I'm not cut out to be a glaciologist, especially one who clearly thinks that the "rivers that flow from the Himalayas and Tibetan plateau" rely almost exclusively on glacier melt. See the end of my post A Cool Look at Glaciers for a published refutation of that myth.

The study clearly supports what many have been saying for years - that studies of (at most) a few hundred of the estimated 150,000 glaciers worldwide are almost worthless, like attempting to assess population health by visiting hospitals. Few glaciologists (at least the vocal kind) seem to be interested in other than "sick" glaciers. That's what's wrong with so-called "mainstream" environmental and climate science (and reporting) - accentuate the unusual and ignore the normal.