Before we get to my geological perspective of the Greenland Ice Sheet (GrIS), let’s first have a look at the NASA perspective:
Greenland Ice Loss 2002-2016
The mass of the Greenland ice sheet has rapidly declined in the last several years due to surface melting and iceberg calving. Research based on observations from the NASA/German Aerospace Center’s twin Gravity Recovery and Climate Experiment (GRACE) satellites indicates that between 2002 and 2016, Greenland shed approximately 280 gigatons of ice per year, causing global sea level to rise by 0.03 inches (0.8 millimeters) per year. These images, created from GRACE data, show changes in Greenland ice mass since 2002. Orange and red shades indicate areas that lost ice mass, while light blue shades indicate areas that gained ice mass. White indicates areas where there has been very little or no change in ice mass since 2002. In general, higher-elevation areas near the center of Greenland experienced little to no change, while lower-elevation and coastal areas experienced up to 13.1 feet (4 meters) of ice mass loss (expressed in equivalent-water-height; dark red) over a 14-year period. The largest mass decreases of up to 11.8 inches (30 centimeters (equivalent-water-height) per year occurred along the West Greenland coast. The average flow lines (grey; created from satellite radar interferometry) of Greenland’s ice converge into the locations of prominent outlet glaciers, and coincide with areas of high mass loss.
However, the rate of ice loss has more than doubled in less than a decade. The rate of ice loss over the 2008 to 2009 period was 286 gigatonnes per year.
Wait a second! Manhattan-sized icebergs don’t look very big compared to the GrIS. Did you ever wonder why melting ice and calving icebergs are always compared to Olympic-sized swimming pools, Empire State Building-enclosing ice cubes, Manhattan Islands and Grand Duchies of Luxembourg? Why aren’t these catastrophic events ever compared to the size of the GrIS itself? Could it be that they don’t appear very catastrophic, or even anomalous, when compared to the GrIS?
How Big is the Greenland Ice Sheet?
According to U.S. Geological Survey Professional Paper 1386–A (2012), the volume of the GrIS is 2,600,000 km3. The USGS cites a 1954 reference for this number and also cites Bamber et al., 2011, which puts the volume at 2,900,000 km3. Bamber has subsequently upped his estimate to 2,960,000 km3. This is funny. Either the GrIS added 360,000 km3 of ice from 1954-2013 at a time when NASA said the GrIS was losing 4,089 km3 or the uncertainty of the volume of the GrIS is about 1,000 times the annual ice loss that is asserted with such precision by Amazing GRACE.
How Does the Recent Ice Loss Compare to the Volume of the Greenland Ice Sheet?
According to Kjeldsen et al., 2015, the GrIS lost over 9,900 km3 of ice from 1900-2010 and an article in The Economist asserted that the GrIS lost 375 Gt/yr (409 km3/yr) from 2011-2014.
1900–1983
75.1 ± 29.4 gigatonnes per year
1983–2003
73.8 ± 40.5 gigatonnes per year
2003–2010
186.4 ± 18.9 gigatonnes per year
km³/yr
gigatonnes/yr
1900–1983
(82)
(75)
1983–2003
(81)
(74)
2003–2010
(203)
(186)
2011-2014
(409)
(375)
Here’s a graphical depiction of this projected up to 2017:
99.58% of the Greenland Ice Sheet has not melted since 1900.
For a little more perspective, let’s convert this to ice cubes.
Based on the asserted loss of ice since 1900, the GrIS has lost the equivalent of a Lake Superior-sized ice cube. However the GrIs remained larger than the Gulf of Mexico (by volume) despite losing a Lake Superior. The Gulf of Mexico has a volume of about 2.5 million km3. If the GrIS melted, the volume of water would be about 2.71 million km3. Before losing Lake Superior, the water volume was 2.72 million km3.
That’s all well and good for the 20th and early 21st centuries; but it doesn’t provide much of a geological perspective.
A Geological Perspective of the Greenland Ice Sheet
How does all this compare to the evolution of the GrIS in the Late Pleistocene and Holocene? For this perspective, I relied on Tabone et al., 2017. They devised a model to simulate how the GrIS has evolved over the past 250,000 years.
To study how oceanic changes impact the evolution of the GrIS over the last glacial cycles, we performed a set of sensitivity tests by perturbing the two key parameters of the basal melting rate equation (Eq. 10): the estimated present-day submarine melting Bref and the heat-flux coefficient κ. For each experiment we ran an ensemble of simulations over the GrIS domain throughout the last 250 ka. In this study the model is initialised by the present-day Greenland topography (Bamber et al., 2013), the characteristic relaxation time for the lythosphere is set to 3 ka and the sea level is maintained constant in time at its present-day value.
[…]
Figure 2 shows the evolution of the grounded ice volume (a) and area (b) for the simulations obtained for different values of the reference melting rate Bref and κ = 0. In this experiment the maximum ice volume reached at glacial times ranges between 3.2-3.9 million km3, just 8-32 % higher than the observed present-day ice volume (Bamber et al., 2013), suggesting that under constant oceanic forcing, the GrIS is limited to a configuration close to that of nowadays. The highest glacial ice volume is reached by imposing a null basal melting to the GrIS margins (Bref = 0), which corresponds to a simulation forced solely by paleo atmospheric variations.
Figure 2 from abone et al., 2017. It’s interesting to note how the GrIS reached its maximum volume just before the Eemian and current interglacial. It’s also interesting to note that the Eemian GrIS shrank so rapidly. Recent studies indicate that temperatures in Central Greenland were 5-8 °C warmer during the Eemian than they are today.
Using the maximum basal melting scenario (Bref = 40), I tacked the modern GrIS volume profile on to the model.
Who would have guessed that the “Anthropocene” GrIS is actually larger than it was during the Late Pleistocene? WUWT? X-axis is in calendar years AD(BC).
Notice something funny? The GrIS may have actually been smaller than it currently is from 35 ka to 15 ka. And, this actually might make sense. Of course, the lower basal melting scenarios would reverse this… And they would also make the modern ice loss even more geologically insignificant.
Greenland Ice Sheet Stratigraphy
The image below is a GPR (ground-penetrating radar) cross-section of the GrIS. It is literally a work of art. GPR is analalogous in many ways to the reflection seismic data that we use in oil & gas exploration. If you click on this link, you will see a full-size image of the cross-section. Note that most of the ice is above the 12 ka horizon. This is very close to the Pleistocene-Holocene boundary. It indicates that most of the ice was deposited since the end of the last Pleistocene glacial stage (ice age in layman’s terms).
Distilling Art from the Figures of Science: “This is a cross-section through the Greenland ice sheet collected with airborne ice-penetrating radar. The radar echogram is displayed as a 3D surface illuminated from above, creating the illusion of texture and emphasizing the layered internal structure of the ice sheet. Composition by Michael Wolovick.”
Earlier in this post I took a swipe at NASA for having the wrong perspective of the GrIS. Maybe I was mistaken… Or maybe NASA is a science savant… Because this is from NASA:
Greenland Ice Sheet Stratigraphy
Visualizations by Cindy Starr Released on January 23, 2015
For nearly a century, scientists have been studying the form and flow of the Greenland Ice Sheet. They have measured the change in the elevation of the surface over time using satellites. They have drilled ice cores in the field to reveal a record of what the past climate was like. They have flown aircraft over the surface of the ice sheet laden with instruments to gleen information about the interior of the ice sheet and the bedrock below.
Now a new analysis of this data has revealed a three dimensional map of the age of the ice sheet. This visualization shows this new 3D age map of the Greenland Ice Sheet, explains how it was created and describes the three distinct periods of climate that are evident within the ice sheet.
The airborne GPR coverage of the GrIS is quite impressive:
Greenland Ice Sheet Stratigraphy: “This print resolution still image shows the flight lines where aircraft have flown over the surface of Greenland collecting data on the ice sheet. Lavender lines indicate flights flown by Operation IceBridge while gray lines indicate prior flights.”
The GPR profiles are tied to ice cores in much the same manner that we tie seismic lines to wells:
Greenland Ice Sheet Stratigraphy: “This image shows the layers from radargram data that were collected by an Operation Ice Bridge flight over the Greenland ice sheet on May 2, 2011. An overlay of colored lines traced along layers indicates the age of individual layers across the ice sheet. The age layers are colored by the period colour, with Holocene layers shown in green and those from the last ice age shown in blue. Labels indicate the age of various layers. The 1966 Camp Century ice core is shown on the left.”
One common feature is that the volume of Holocene ice appears to be as large or larger than the volume of Pleistocene ice.
Greenland Ice Sheet Stratigraphy: “This print resolution image shows one cross-section of the age of the Greenland Ice Sheet as determined by MacGregor et al. (See citation under the ‘More Details…’ button below) Layers determined to be from the Holocene period, formed during the past 11.7 thousand years, are shown in Green. Age layers accumulated during the last ice age, from 11.7 to 115 thousand years ago are shown in blue. Age layers from the Eemian period, more than 115 thousand years old are shown in red. Regions of unknown age are filled with a flat gray colour.”
It’s particularly notable that in Central Greenland there is still a significant remnant of Eemian ice. In much of Central Greenland about 12,000 years worth of Holocene ice is thicker than over 100,000 years of Pleistocene ice. This is due to the fact that glacial stages (AKA ice ages) are very cold and very dry. The snow accumulation rate during the Holocene has been much higher than that of the last Pleistocene glacial stage.
How Does the Recent Melting of the Greenland Ice Sheet Compare to the Early Holocene?
Short answer: Same as it ever was. Vinther et al., 2009 reconstructed the elevations of four ice core sites over the Holocene. There has been very little change in elevation of the two interior ice core sites (NGRIP and GRIP), while the two outboard sites (Camp Century and DYE3) have lost 546 and 342 m of ice respectively.
Most of the melting since the beginning of the Holocene has occurred on the outboard, lower elevation portions of the GrIS – Same as it ever was. X-axis is in calendar years AD(BC). Elevation reconstruction data from Vinther et al., 2009. Map from Weißbach et al., 2015.Elevation profiles: End Pleistocene and 2000 AD.
Conclusion
From this geological perspective, the Greenland Ice Sheet is not behaving badly.
References
Bamber, J. L., J. A. Griggs, R. T. W. L. Hurkmans, J. A. Dowdeswell, S. P. Gogineni, I. Howat, J. Mouginot, J. Paden, S. Palmer, E. Rignot, and D. Steinhag. A new bed elevation dataset for Greenland.The Cryosphere, 7, 499–510, 2013 www.the-cryosphere.net/7/499/2013/ doi:10.5194/tc-7-499-2013.
Kjeldsen, Kristian K., Niels J. Korsgaard, Anders A. Bjørk, Shfaqat A. Khan, Jason E. Box, Svend Funder, Nicolaj K. Larsen, Jonathan L. Bamber, William Colgan, Michiel van den Broeke, Marie-Louise Siggaard-Andersen, Christopher Nuth, Anders Schomacker, Camilla S. Andresen, Eske Willerslev & Kurt H. Kjær. Spatial and temporal distribution of mass loss from the Greenland Ice Sheet since AD 1900.Nature volume 528, pages 396–400 (17 December 2015) doi:10.1038/nature16183.
Sutterley, Tyler C., Isabella Velicogna, Beata Csatho, Michiel van den Broeke, Soroush Rezvan-Behbahani and Greg Babonis. Evaluating Greenland glacial isostatic adjustment corrections using GRACE, altimetry and surface mass balance data. Published 15 January 2014 • 2014 IOP Publishing Ltd. Environmental Research Letters, Volume 9, Number 1.
Tabone, Ilaria, Javier Blasco, Alexander Robinson, Jorge Alvarez-Solas, and Marisa Montoya. The sensitivity of the Greenland ice sheet to glacial-interglacial
oceanic forcing.Clim. Past Discuss., https://doi.org/10.5194/cp-2017-127. Manuscript under review for journal Clim. Past. Discussion started: 8 November 2017.
Vinther, B.M., S.L. Buchardt, H.B. Clausen, D. Dahl-Jensen, S.J. Johnsen, D.A. Fisher, R.M. Koerner, D. Raynaud, V. Lipenkov, K.K. Andersen, T. Blunier, S.O. Rasmussen, J.P. Steffensen, and A.M. Svensson. 2009. Holocene thinning of the Greenland ice sheet.Nature, Vol. 461, pp. 385-388, 17 September 2009. doi:10.1038/nature08355.
Weißbach, S., A. Wegner, T. Opel, H. Oerter, B. M. Vinther and S. Kipfstuhl. Spatial and temporal oxygen isotope variability in northern Greenland – implications for a new climate record over the past millennium.Clim. Past, 12, 171–188, 2016 www.clim-past.net/12/171/2016/ doi:10.5194/cp-12-171-2016.
Williams, R.S., Jr., and Ferrigno, J.G., eds., 2012, State of the Earth’s cryosphere at the beginning of the 21st century–Glaciers, global snow cover, floating ice, and permafrost and periglacial environments: U.S. Geological Survey Professional Paper 1386–A, 546 p.
Fun Stuff
The Cold War connections to some of the ice core sites is really cool! The DYE-2 and DYE-3 ice core locations were once part of the DEW Line.
DYE-2 – a relic from a not so distant past
The dart is still in the dartboard and the beer is still on the counter in the bar. So untouched is DYE-2. Slowly, the weather and wind have encroached and in a few years it will probably be difficult to get in and see this unique, American cold war relic on the ice sheet in Greenland.
Text: Toke Brødsgaard, greenland today July 2015
There is an air of mystery when you move around the now abandoned DYE-2 radar station which is located quite a long way out on the ice cap in Greenland. The site remains so untouched that it is as if everyone left the place at the same time when it was abandoned in October 1988.
Moving around the build-ing, you can see rooms, bars and workshops in the same state in which they were left. The only evidence that time has passed, is that the weather has broken some windows and the snow has sneaked in and disturbed the peace.
[…]
Map showing the »Distant Early Warning (DEW) Line« which DYE-2 was part of.
The Distant Early Warning Line
DYE-2 was a major undertaking. At its most active, there were 60 men at the station. The fact that the building was able to accommodate such a large staff during periods when it was impossible to go outside because of cold and storms says a lot about its size.
Strategically, DYE-2 was in an important position, since it was a part of the Distant Early Warning (DEW) radar line. It was established to warn of any Soviet air attacks against the USA during the cold war. The DEW Line consisted in Greenland of DYE-1, which is located just outside Sisimiut, DYE-2 and DYE-3, which are located further to the east on the Greenland ice sheet and DYE-4 which is located not far from Kulusuk in East Greenland.
DEW was a chain of a total of 60 radar stations stretching over a 5,800km long line along the 69th parallel north from Alaska over Canada via Greenland to Iceland. The actual radar chain was active from July 31st 1957 until the end of the 1980s.
The main trench at Camp Century in Greenland led to an underground city carved out of the ice. PICTORIAL PARADE/ARCHIVE PHOTOS/GETTY IMAGES
Mysterious, ice-buried Cold War military base may be unearthed by climate change
By Julia Rosen Aug. 4, 2016 , 11:00 AM
It sounds like something out of a James Bond movie: a secret military operation hidden beneath the Greenland Ice Sheet. But that’s exactly what transpired at Camp Century during the Cold War.
In 1959, the U.S. Army Corps of Engineers built the subterranean city under the guise of conducting polar research—and scientists there did drill the first ice core ever used to study climate. But deep inside the frozen tunnels, the corps also explored the feasibility of Project Iceworm, a plan to store and launch hundreds of ballistic missiles from inside the ice.
The military ultimately rejected the project, and the corps abandoned Camp Century in 1967. Engineers anticipated that the ice—already a dozen meters thick—would continue to accumulate in northwestern Greenland, permanently entombing what they left behind.
Now, climate change has upended that assumption. New research suggests that as early as 2090, rates of ice loss at the site could exceed gains from new snowfall. And within a century after that, melting could begin to release waste stored at the camp, including sewage, diesel fuel, persistent organic pollutants like PCBs, and radiological waste from the camp’s nuclear generator, which was removed during decommissioning.
If these predictions come to pass, the researchers… [blah, blah, blah]…
Thank you, David Middleton, and commenters for an excellent scientific discussion — one of the gems of WUWT. Beautiful enough to save for colleagues, friends and family who are interested in researching truths, and the interesting variety of geological/climate states of Mother Earth.
jsuther2013
March 23, 2018 3:13 pm
I read the article but not the comments. For perspective, why not put the zero point on some of those graphs? That would show just how trivial the variation really is.
Because Greenland has been continuously glaciated since at least the Mid-Pliocene. The lowest volume of the GrIS over the past 250,000 years, supported by any evidence is about 2 million km^3.
“Earliest Pleistocene” would be more correct if you refer to an ice-cap covering lowland areas as well. The Kap Köbenhavn formation seems to be the last time most of Greenland was ice-free, and that was about 2.4 million years ago.
The highlands of East Greenland have been glaciated much longer, at the very least since the Late Eocene, 40 million years ago. That is when IRD (Ice Rafted Debris) first shows up in Fram Strait, which means that there were tidewater glaciers.
The minimum Pleistocene volume may well have been somewhat smaller than 2 million km3. IRD studies have shown that during the MIS 11 interglacial the icecap probably separated into a northern and a southern dome and (admittedly loose) dating of the sub-ice sediments at Dye-3 also indicates that it may have been ice-free at this time. Dye-3 is close to the “saddle” between the two major domes.
For those who wonders how IRD can tell how large the ice-cap was, Greenland consists of several geological provinces with distinct rock types and –ages. IRD consists of rocks that are being actively eroded by glaciers calving into the ocean. During the Eemian (MIS 5e) interglacial IRD off south Greenland consists of rock from all provinces, indicating a continuous (or at least almost continuous) ice cover from north to south. During MIS 11 rocks from one province (near the “saddle”) are missing, strongly suggesting two separate ice-caps. The absence is not absolute proof though, since there may have been ice inland that did not calve into the ocean.
It’s funny how IRD or dropstones are evidence of colder climates… yet the warmunists claim that the increased calving of icebergs is evidence of Gorebal Warming.
Yogi Bear
March 23, 2018 5:03 pm
The cross section nicely helps in explaining why the global sea level was higher 6000-8000 years ago.
@ur momisugly David Middleton. You know about 1000 times what I know about glaciers. I have asked this question many times here on WUWT.
Why are the largest and longest tidewater glaciers in the northern and southern hemispheres not retreating but advancing, as are the smaller mountain glaciers (some, not all) ? I have never gotten a clear scientific answer to this question. Sorry to use Wackapedia as a ref., but you can find this/these results in other links.
Brüggen Glacier: “…Now about 66 km (41 mi) in length, it is the longest glacier in the southern hemisphere outside Antarctica…” https://en.wikipedia.org/wiki/Br%C3%BCggen_Glacier
Hubbard Glacier: Hubbard is the largest tidewater glacier in North America… https://en.wikipedia.org/wiki/Hubbard_Glacier
Taku Glacier: “Taku Glacier is a tidewater glacier located in Taku Inlet in the U.S. state of Alaska, just southeast of the city of Juneau. Recognized as the deepest and thickest alpine temperate glacier known in the world, the Taku Glacier is measured at 4,845 feet (1,477 m) thick.[1] It is about 58 kilometres (36 mi) long, and is largely within the Tongass National Forest.”
It is the largest glacier originating in the Juneau Ice field, also a tidewater glacier. https://en.wikipedia.org/wiki/Taku_Glacier
All of these glaciers mentioned are advancing. Most start at very high altitudes.
There are other large tidewater glaciers in Alaska and South America which are advancing.
My basic question would be: Why are these largest glaciers advancing, while many (not all) smaller lower mountain glaciers generally retreating?
At a guess: more precipitation. This is at least as important as temperature. For example there is considerable evidence that the EAIS (East Antarctic Ice Sheet) thickens during interglacials, and very strong evidence that glaciation in the Transantarctic Mountains was much more extensive during the warm Pilocene.
Also note the virtual absence of glaciers in Eastern Siberia, now and during the ice-ages, despite the lowest temperatures outside Antarctica.
My personal analogy is to the icemaker in my freezer. Does it overflow with ice when the temperature in the freezer is too warm? No.
Glaciers are always moving. They may move at a glacially slow pace, but they don’t often sit still.
The “consensus” school of thought says that Greenland’s outlet glaciers are moving more quickly due to increased lubrication from the drainage of glacial lakes formed by increased surface meltwater. The meltwater percolates down through fractures in the ice to form moulins… https://en.m.wikipedia.org/wiki/Moulin_(geomorphology)
This leads to an increase in the rate of iceberg calving and frantic headlines about Manhattan-sized icebergs.
The funny thing is that when I took geomorphology about 10 years before Al Gore and James Hanson invented Gorebal Warning, increased rates of iceberg calving were indicative of colder climates. “Dropstones,” out-of-place rocks in marine sediments, carried out to sea by icebergs and dropped to the seafloor as the iceberg melted, are generally associated with colder climates. See my discussion of Jakobshavn Isbrae, Greenland’s largest outlet glacier, towards the end of this post… https://wattsupwiththat.com/2012/08/17/2012-the-year-greenland-melted-aka-alarmists-gone-wild/
Off the top of my head, I don’t know the specific answers to your questions. I’ll see what I can dig up.
Most, but not all, glaciers have been retreating since the end of neoglaciation (~1850). For about 5,000 years before, most were advancing, reaching their maximum Holocene extent during the Little Ice Age.
I’ve always heard the Brüggen called the Pio XI glacier.
whiten
March 24, 2018 12:08 pm
I will offer another line of thought here.
The actual assessment of the Greenland ice sheet as it stands, heavily relies in the history of ice, which when used produces an artifact that actually makes that ice history very dubious and not quite acceptable unless crazy acrobatics in thought and rationale considered…..makes really difficult to accept.
That assessment there, in consideration of the actual ratio of the mas of “blue” ice versus “green” ice happens to be that way due to a history of ice that consist with a glacial period of a ~100k years span versus a warm trend of ~10k years.
This is a “product” that mainly spring out as shown due to the ice history when trying to mend it with the rest of the data, and from the outset it confuses the ice history, as per that history of ice to be correct a lot of silly acrobatics are required to maintain it, while actually the prospect of that never being possibly achievable.
That ratio is not possible, but is considered as such because while there is not much you can do about the overall mas of ice and the age of ice, otherwise you have to depart from the ice history as it stands….
That ratio is a calculated estimate very much weighted by the history of ice, aka the ~100k years glacial period, and, leading to a very “stiff” ratio condition between “glacial” ice and “non “glacial” ice, where not much room or tolerance there in the variation of the conditions, meaning that any little variation subjecting out side this term or projection outside this term will clearly have to be considered as a result of a non natural force.
All this, from what I can see, it happens to be this way simply as a result of refusing to reconsider the history of ice.
The only point that can be making a difference if reconsidered.
When you look at that “green” ice mass and the ratio of it to the “blue” ice mass, you are looking at possibly one of the proofs of the ice history refutation, as that history stands thus far, a proof that refutes 100k years glacial periods.
And that ratio can not be explained or maintained unless crazy acrobatics considered, like being able to explain and be supported by data and rationale, how Greenland not gaining any extra ice during a glacial period…..and also when Greenland in a warm period during interglacial must have an average temp of +10 to +15C for at least a 5k years duration…..
and still this may not be good enough to support the estimation of that ice ratio between “blue” and “green” ice .
cheers
Sorry tty, but is the only “key” that you can play to get out of the conundrum there, the rest of the “keys” change no much, provided that you consider the problem with the conundrum there….otherwise please do stick with it….but consider my point, the produced artifact of the ratio of glacial versus interglacial ice as per that ice history stands as a refutation of the process where all these “keys” become non valid.
But still considering to adjust for the only “key” that will make the difference, the ice history, can allow for a better produced artifact, a very much different ratio which may validate the process and the “keys”
Hopefully you get my point.
Not considering the change of the ice history, means a stack condition with the conundrum….
That happens to be the only one way out…as far as I can tell.
thanks
cheers
GRACE was a good scientific experiment that lasted longer than expected. As an experiment it allowed researchers to identify issues with remote sensing platforms that are hopefully resolved with GRACE FO. As an accurate measurement of global ice mass and water it is not – large errors remain in the data.
Time‐variable gravity observations of ice sheet mass balance: Precision and limitations of the GRACE satellite data. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/grl.50527
Aliasing errors discussed here
ftp://ftp.csr.utexas.edu/pub/ggfc/papers/Seo_et_al_2008.pdf
Post-processing removal of correlated errors in GRACE data
https://www.researchgate.net/publication/228770590_Post-processing_removal_of_correlated_errors_in_GRACE_data
An analytical method for error analysis of GRACE-like missions based
on spectral analysis
https://arxiv.org/pdf/1609.08860.pdf
The role of accelerometer data calibration within GRACE gravity field recovery: Results from ITSG-Grace2016 Instrument degradation from battery power loss.
https://www.sciencedirect.com/science/article/pii/S0273117716304409
Thank you, David Middleton, and commenters for an excellent scientific discussion — one of the gems of WUWT. Beautiful enough to save for colleagues, friends and family who are interested in researching truths, and the interesting variety of geological/climate states of Mother Earth.
I read the article but not the comments. For perspective, why not put the zero point on some of those graphs? That would show just how trivial the variation really is.
Because Greenland has been continuously glaciated since at least the Mid-Pliocene. The lowest volume of the GrIS over the past 250,000 years, supported by any evidence is about 2 million km^3.
“Earliest Pleistocene” would be more correct if you refer to an ice-cap covering lowland areas as well. The Kap Köbenhavn formation seems to be the last time most of Greenland was ice-free, and that was about 2.4 million years ago.
The highlands of East Greenland have been glaciated much longer, at the very least since the Late Eocene, 40 million years ago. That is when IRD (Ice Rafted Debris) first shows up in Fram Strait, which means that there were tidewater glaciers.
The minimum Pleistocene volume may well have been somewhat smaller than 2 million km3. IRD studies have shown that during the MIS 11 interglacial the icecap probably separated into a northern and a southern dome and (admittedly loose) dating of the sub-ice sediments at Dye-3 also indicates that it may have been ice-free at this time. Dye-3 is close to the “saddle” between the two major domes.
For those who wonders how IRD can tell how large the ice-cap was, Greenland consists of several geological provinces with distinct rock types and –ages. IRD consists of rocks that are being actively eroded by glaciers calving into the ocean. During the Eemian (MIS 5e) interglacial IRD off south Greenland consists of rock from all provinces, indicating a continuous (or at least almost continuous) ice cover from north to south. During MIS 11 rocks from one province (near the “saddle”) are missing, strongly suggesting two separate ice-caps. The absence is not absolute proof though, since there may have been ice inland that did not calve into the ocean.
It’s funny how IRD or dropstones are evidence of colder climates… yet the warmunists claim that the increased calving of icebergs is evidence of Gorebal Warming.
The cross section nicely helps in explaining why the global sea level was higher 6000-8000 years ago.
Yogi,
The whole planet was a lot warmer than now during the Holocene Climatic Optimum, but not as hot as the Eemian, the previous interglacial.
@ur momisugly David Middleton. You know about 1000 times what I know about glaciers. I have asked this question many times here on WUWT.
Why are the largest and longest tidewater glaciers in the northern and southern hemispheres not retreating but advancing, as are the smaller mountain glaciers (some, not all) ? I have never gotten a clear scientific answer to this question. Sorry to use Wackapedia as a ref., but you can find this/these results in other links.
Brüggen Glacier: “…Now about 66 km (41 mi) in length, it is the longest glacier in the southern hemisphere outside Antarctica…”
https://en.wikipedia.org/wiki/Br%C3%BCggen_Glacier
Hubbard Glacier: Hubbard is the largest tidewater glacier in North America…
https://en.wikipedia.org/wiki/Hubbard_Glacier
Taku Glacier: “Taku Glacier is a tidewater glacier located in Taku Inlet in the U.S. state of Alaska, just southeast of the city of Juneau. Recognized as the deepest and thickest alpine temperate glacier known in the world, the Taku Glacier is measured at 4,845 feet (1,477 m) thick.[1] It is about 58 kilometres (36 mi) long, and is largely within the Tongass National Forest.”
It is the largest glacier originating in the Juneau Ice field, also a tidewater glacier.
https://en.wikipedia.org/wiki/Taku_Glacier
All of these glaciers mentioned are advancing. Most start at very high altitudes.
There are other large tidewater glaciers in Alaska and South America which are advancing.
My basic question would be: Why are these largest glaciers advancing, while many (not all) smaller lower mountain glaciers generally retreating?
At a guess: more precipitation. This is at least as important as temperature. For example there is considerable evidence that the EAIS (East Antarctic Ice Sheet) thickens during interglacials, and very strong evidence that glaciation in the Transantarctic Mountains was much more extensive during the warm Pilocene.
Also note the virtual absence of glaciers in Eastern Siberia, now and during the ice-ages, despite the lowest temperatures outside Antarctica.
Precipitation is often more important than temperature.
My personal analogy is to the icemaker in my freezer. Does it overflow with ice when the temperature in the freezer is too warm? No.
Glaciers are always moving. They may move at a glacially slow pace, but they don’t often sit still.
The “consensus” school of thought says that Greenland’s outlet glaciers are moving more quickly due to increased lubrication from the drainage of glacial lakes formed by increased surface meltwater. The meltwater percolates down through fractures in the ice to form moulins…
https://en.m.wikipedia.org/wiki/Moulin_(geomorphology)
This leads to an increase in the rate of iceberg calving and frantic headlines about Manhattan-sized icebergs.
The funny thing is that when I took geomorphology about 10 years before Al Gore and James Hanson invented Gorebal Warning, increased rates of iceberg calving were indicative of colder climates. “Dropstones,” out-of-place rocks in marine sediments, carried out to sea by icebergs and dropped to the seafloor as the iceberg melted, are generally associated with colder climates. See my discussion of Jakobshavn Isbrae, Greenland’s largest outlet glacier, towards the end of this post…
https://wattsupwiththat.com/2012/08/17/2012-the-year-greenland-melted-aka-alarmists-gone-wild/
Off the top of my head, I don’t know the specific answers to your questions. I’ll see what I can dig up.
Most, but not all, glaciers have been retreating since the end of neoglaciation (~1850). For about 5,000 years before, most were advancing, reaching their maximum Holocene extent during the Little Ice Age.
I’ve always heard the Brüggen called the Pio XI glacier.
I will offer another line of thought here.
The actual assessment of the Greenland ice sheet as it stands, heavily relies in the history of ice, which when used produces an artifact that actually makes that ice history very dubious and not quite acceptable unless crazy acrobatics in thought and rationale considered…..makes really difficult to accept.
That assessment there, in consideration of the actual ratio of the mas of “blue” ice versus “green” ice happens to be that way due to a history of ice that consist with a glacial period of a ~100k years span versus a warm trend of ~10k years.
This is a “product” that mainly spring out as shown due to the ice history when trying to mend it with the rest of the data, and from the outset it confuses the ice history, as per that history of ice to be correct a lot of silly acrobatics are required to maintain it, while actually the prospect of that never being possibly achievable.
That ratio is not possible, but is considered as such because while there is not much you can do about the overall mas of ice and the age of ice, otherwise you have to depart from the ice history as it stands….
That ratio is a calculated estimate very much weighted by the history of ice, aka the ~100k years glacial period, and, leading to a very “stiff” ratio condition between “glacial” ice and “non “glacial” ice, where not much room or tolerance there in the variation of the conditions, meaning that any little variation subjecting out side this term or projection outside this term will clearly have to be considered as a result of a non natural force.
All this, from what I can see, it happens to be this way simply as a result of refusing to reconsider the history of ice.
The only point that can be making a difference if reconsidered.
When you look at that “green” ice mass and the ratio of it to the “blue” ice mass, you are looking at possibly one of the proofs of the ice history refutation, as that history stands thus far, a proof that refutes 100k years glacial periods.
And that ratio can not be explained or maintained unless crazy acrobatics considered, like being able to explain and be supported by data and rationale, how Greenland not gaining any extra ice during a glacial period…..and also when Greenland in a warm period during interglacial must have an average temp of +10 to +15C for at least a 5k years duration…..
and still this may not be good enough to support the estimation of that ice ratio between “blue” and “green” ice .
cheers
The “ice history” is pretty solid since it is based on counting annual layers.
In Greenland, the layers are relatively thick, particularly during the Holocene.
Sorry tty, but is the only “key” that you can play to get out of the conundrum there, the rest of the “keys” change no much, provided that you consider the problem with the conundrum there….otherwise please do stick with it….but consider my point, the produced artifact of the ratio of glacial versus interglacial ice as per that ice history stands as a refutation of the process where all these “keys” become non valid.
But still considering to adjust for the only “key” that will make the difference, the ice history, can allow for a better produced artifact, a very much different ratio which may validate the process and the “keys”
Hopefully you get my point.
Not considering the change of the ice history, means a stack condition with the conundrum….
That happens to be the only one way out…as far as I can tell.
thanks
cheers