Anthony Watts has posted an article (
archived here) about the new discovery of two lakes under the ice sheet in north west Greenland.
The paper is by a team led by Steven J. Palmer of the Scott Polar Research Institute at Cambridge. It's published in Geophysical Research Letters (GRL) and is
available on-line (open access).
The lakes are about 500 m above sea level, right up in the north west corner. The radar transect shows that Lake 1 (L1) is >1.1 km long and Lake 2 (L2) is > 2.4 km long. The lakes are located in a 980 km2 drainage basin and positioned 16.0 km and 11.5 km from the nearest ice divide, respectively. The location and other details of the two lakes are shown below. (As always, click the image for a larger view):
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Figure 1: Flight-line map and derived bed elevation from NW Greenland. (a) Regional context of the study area shown on a Landsat image acquired on 1 August 2002, showing radar flightlines (red lines), the ice divide (dashed black line) and the settlement of Qaanaaq (white circle). (b) Subglacial bed elevations (colour) derived from airborne ice thickness measurements along flightlines. Black lines delineate contours of basal hydraulic potential, thick black lines show the inferred extent of observed subglacial lakes, and dashed black lines show possible previous larger extent.
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It must feel great to be part of the team that made a new discovery like this one. They've obviously been looking for some time. I came across
another paper in which researchers were predicting where the most likely locations were for lakes in Greenland based on models, but it didn't look as if they had these ones on their radar (so to speak).
Figure 2 in the
Palmer paper shows the radar evidence for the lakes.
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Figure 2. Radar evidence for subglacial lakes. Radargrams showing data acquired along flightlines labelled in Figure 1, showing subglacial lakes (L1 and L2) on profile A-A’ (GOG2/F04T01a), with bed reflection strength shown below. Areas of sub-horizontal and brightly reflecting bed on profiles B-B’ (20120510_01_035) and C-C’ (20120510_01_074) are indicated by white bars below the radargrams. These areas could indicate the presence of saturated sediment at the bed, and therefore may indicate previous subglacial lake extent.
Source: Palmer13 GRL |
As it says in the description above and elsewhere in the paper, the reflectance of the bed suggested to the researchers that the lake may have been larger in the past. From their paper, they surmise the lakes might previously have been three times larger.
Contrast Greenland lakes with Antarctic subglacial lakes
Unlike the lakes in Antarctica, which
as far as I can gather are fully contained under the ice, these Greenland lakes may be being fed by water from the outside, through cracks in the ice and they could be being fed by a nearby surface lake. Here is an animation of a subglacial lake system in Antarctica for comparison:
As
described on YouTube, the animation of subglacial Antarctic lakes shows the "dynamics of subglacial water exchange and what it looks like from space. Starting from an artist's concept of the Antarctic surface we move down to a cross section of the ice sheet with lakes hidden deep beneath. As pressure is exerted on one lake, the water in it is forced to an adjacent lake. This water movement results in elevation changes at the surface over both lakes, detectable by NASA satellites. The camera then moves to a 'top-down' view of a system of these hidden lakes and streams before dissolving into observed satellite data."
And
from NASA, which was the source of the animation:
Water moving between subglacial lakes can explain elevation changes in ice stream surfaces. This animation shows modeled behavior of subglacial lakes. Depending on the pressure of overlying ice, water can pool in unusual places. Unlike a water body with no ice overhead, a subglacial lake might form on the top of a hill if it is surrounded by ice that exerts tremendous pressure.
Another thing is that the ice is 750 m and 809 m thick over the newly discovered Greenland lakes. Not as thick as the ice over the lakes in Antarctica. So they are colder. Apparently ice sheets are coldest near the top and get warmer as you go deeper, being warmed by earth beneath.
You can read more about the discovery
in the paper itself or from the
press release from Cambridge.
From the WUWT comments
There were a few comments that made me wonder if more people are sending up WUWT. I'd have said most of them would have had to have been from fake deniers, except for the fact that I recognise the names from other articles. They range from "scientists don't know nuffin" to individual commenters claiming to know all there is to know about everything - and various in-betweens. (
Archived here.)
Latitude didn't read the bit about the lakes lying below about 800 m of ice... (oh, I just noticed Latitude was talking about feet not metres. How quaint :) So maybe he did read it) ...and says he doesn't believe the scientists when they write that "the newly discovered lakes are most likely fed by melting surface water draining through cracks in the ice", because:
November 27, 2013 at 6:09 pmGreenland is a bowl…and I serious doubt if a “crack” is over 2 thousand 600 feet deep
Michael P thinks there is nothing that can be learnt from any scientific investigation of the lakes because they've been there too long. He says:
November 27, 2013 at 6:41 pm
“Subglacial lakes are likely to influence the flow of the ice sheet, impacting global sea level change. The discovery of the lakes in Greenland will also help researchers to understand how the ice will respond to changing environmental conditions.”
Discovering the lakes now does not mean they have not been there for centuries or millenia. If the lakes have been there for a long time then they have been influencing the flow of the ice sheet for a long time and will have no added impact to sea levels. The conjecture is stupefying
norah4you hasn't a clue about where the newly discovered lakes are located, and points to a map of the western and southern settlements and says "scientists don't know nuffin":
November 27, 2013 at 7:04 pm
Discovered? Known by historians interested in old maps. Also written about in at least two sources from 12th-14th century. What scientist discovering the lakes don’t seem to know is that the ice above periodically was open, according to one of the sources, before 1341 and that the freezing of thick ice above came very quickly. Same freezing as made ‘Garden under Sandet’ in a few years going from a wealthy farm with lots of animals (stables in building show that) to an under thick ice long forgotten civilisation. Please read: Garden under Sandet, archeurope.com
Here's a map showing the settlements in southern Greenland, which
Norah4you pointed to, and the newly discovered lakes.
Steve Reddish didn't bother to read the paper or he would have found the answer to his first question. At least he read the press release Anthony posted. He says:
November 27, 2013 at 7:24 pm
“The two lakes are each roughly 8-10 km2, and at one point may have been up to three times larger than their current size.”
How was it determined that the lakes were previously larger? The “may have” seems to mean that they are guessing.
“The discovery of the lakes in Greenland will also help researchers to understand how the ice will respond to changing environmental conditions.”
Apparently their guess is that global warming is reducing the size of the lakes. Thus these lakes are affecting the flow rate of the ice sheet less and less.
SR
DHF thinks the scientists just made it up:
November 27, 2013 at 11:58 pm
Looks like another hilarious chapter in the climate fiction chronicle.
johnmarshall says all the scientists in Greenland can pack up and go home, because he, johnmarshall, knows everything there is to know about Greenland:
November 28, 2013 at 2:24 am
greenland ice sheet sits in a deep depression in the crust caused by to weight of the ice thus limitig any outward movement. These lakes have been there for thousands of years and have caused no movement to date.
IIRC,
Bruce Cobb has been tagged as a scientific
illiterati before and shows no sign of changing. It's hard to tell whether he's arguing that scientists should not look for answers to scientific questions or whether he's arguing that they should, but they should all be of independent means and not only work for no pay, but should finance their own expeditions out of their own pockets. He says:
November 28, 2013 at 4:39 am
“Because the way in which water moves beneath ice sheets strongly affects ice flow speeds, improved understanding of these lakes will allow us to predict more accurately how the ice sheet will respond to anticipated future warming.”
And there it is; the requisite money-grubbing anti-science quote. They don’t have a clue what effect if any, these recently-discovered lakes might have, but the hope appears to be that they’ve discovered some sort of positive feedback, or Trenberth’s infamous “arctic death spiral”.
Dave in Canmore could have read a bit more before writing, but at least his brain seems to be working unlike most of the others at WUWT:
November 28, 2013 at 8:30 am
“The ice in Greenland is also thinner than that in Antarctica, resulting in colder temperatures at the base of the ice sheet. ”
I find this surprising. Antarctica ice thickness is generally >2km thick while Greenland ice thickness is generally >1km. Is there really a difference in insulation between 1km of ice and 2 ?
What’s Up With That?
Jimbo says that these scientists shouldn't be asking and answering questions. And then proceeds to ask a lot of questions - duh!:
November 28, 2013 at 8:33 am
Why don’t these Calamastrologists just say we discovered a couple of sub-glacial lakes and leave it at that. How do we know these lakes weren’t there in 1900, 1925, 1940 1,000 years ago, 2,000 years ago? Oh, we do know because they say it might have been larger in the past!!! What does this tell me about the future of the ice sheet? What do they know? Is this just a discovery followed by a whole pile of guesswork?
gymnosperm thinks that experts in the cryosphere are not "serious scientists" and know nothing about ice and says:
November 28, 2013 at 9:04 am
” The thicker Antarctic ice can act like an insulating blanket, preventing the freezing of water trapped underneath the surface.”
Really? All that ice in Greenland isn’t enough “insulation”? These sorts of ad hoc preconceptions have no place in serious science.
Billy Liar must be joking when he says:
November 28, 2013 at 9:41 am
Do they have any evidence that the lakes weren’t there before they just discovered them?
Cambridge was once a great university (pre-AGW).
Palmer, Steven J., Julian A. Dowdeswell, Poul Christoffersen, Duncan A. Young, Donald D. Blankenship, Jamin S. Greenbaum, Toby Benham, Jonathan Bamber, and Martin J. Siegert. "Greenland subglacial lakes detected by radar." Geophysical Research Letters (2013). DOI: 10.1002/2013GL058383
