What’s below the Greenland Ice?

By Andy May

An interesting PNAS article discusses the deepest portion of the Camp Century Greenland Ice core. It is not paywalled. The researchers, led by Andrew Christ (Dept. of Geology, University of Vermont) found evidence of an ice-free vegetated environment at the base of the Camp Century ice core roughly one million years ago. This means the glaciers, which are currently 1.4 km (0.9 miles) thick, at the Camp Century location completely melted and reformed sometime between 0.7 and 1.4 million years ago. The Camp Century location, along with other deep ice core locations, are shown in Figure 1.

The Greenland Ice Sheet was complete by 7.5 Ma (million years ago) and grew substantially between 3.3 and 2.7 Ma. So, generally we are discussing a period of time when Greenland was usually very much like today.

Figure 1. Camp Century location and Greenland Ice cross section.

The sediments below the ice, contain well-preserved fossil plants and other paleo-evidence of an ice-free environment at the Camp Century location. Macrofossils were also found at NGRIP, but in ice. Photographs of the macrofossils found in the Camp Century core are shown in Figure 2.

Figure 2. Macrofossil microphotographs and leaf wax concentrations from the basal cores.

The basal sediment portion of the Camp Century core is 3.4 meters thick. The researchers divided it into three units. The evidence suggests that the most recent sediment layer experienced melting and refreezing between 0.7 and 1.4 Ma. In Figure 3 we show Javier’s illustration of the past million years.

Figure 3. Javier’s figure of the last 25 “MIS” interglacials, with 0.7 to 1.4 Ma marked. The δ18O (change in the oxygen 18 ratio) pseudo-temperature anomaly is high, but not particularly unusual, for MIS 25, and the 65°N insolation anomaly is unusually high. Perhaps this is when the melting occurred.

Figure 4 shows the entire possible interval for the Camp Century melting event from Tzedakis, et al. (2017).

Figure 4. Orbital obliquity peaks are shaded in gray, the black line is the caloric summer half-year insolation at 65°N, the red circles are insolation maxima nearest the onset of interglacials, black diamonds are continued interglacials, light blue triangles are failed interglacials. The orange line is the δ18O stack representing temperature. The upper numbers are MIS numbers for interglacials and the lower are kyrs (thousands of years) before present or the number of a continued interglacial or a failed interglacial. The “Mid-Pleistocene Transition” toward lower-frequency higher-amplitude glacial cycles is apparent near MIS 38/37. Source Tzedakis, et al., Nature, 2017.

The earlier portion of the time of the melting is near the “Mid-Pleistocene Transition,” about 1.25 Ma. The Mid-Pleistocene transition (MPT) is a time defined by the total energy required for an interglacial to begin and be successful. Before 1.5 Ma, less total energy was required to melt the glacial ice and enter an interglacial period like today. The amount of energy required increases with time until about 0.6 Ma, when it leveled off, see Figure 5. The period of possible total melting seen in the Camp Century core, at 77°N and 61°W, is essentially the breadth of the Mid-Pleistocene transition.

Figure 5: Temperature peaks for the last 2.6 million years separated into successful interglacials (red dots), failed interglacials (blue triangles), continued interglacials (black diamonds) and uncertain assignments (open symbols). The dashed black line separates successful interglacials from unsuccessful interstadials with only two misclassifications (59 and 63). The ramp in the dashed line is the “Mid-Pleistocene transition.” The Y axis is the effective “melting” energy, that is the mean summer solstice insolation peak. Source: After Tzedakis, et al., 2017.

During the MPT transitional period, the stability of the northern ice sheet was in flux. As Figures 3 and 4 show, MIS 31 (1.7 Ma) and MIS 25 (9.6 Ma) were unusually warm and occurred during a period with few very cold glacials. In fact, the glacial periods prior to 600K years ago, just weren’t as cold as the glacials of the past 600K years. The Dye ice core suggests it was ice free between 424 and 374 ka (MIS-11), but Dye is much farther south than Camp Century (see Figure 1). MIS 11 is just after the end of the MPT.

The gold curve in figure 4 is δ18O, an oxygen isotope ratio that varies linearly with surface temperature. It peaks during MIS intervals. The other curve in Figure 4 is the 65°N insolation. These curves are also shown in Figure 3, where they are easier to read.

The current elevation of the underlying sediment layer at Camp Century is 500 meters above mean sea level, removing the 1.4 km. of overlying ice would result in a rebound of about 950 meters in roughly 10,000 years. So, if conditions were the same when the ice melted, the elevation would eventually be about 1,400 meters.


It is hard to draw any firm conclusions from the data shown in this article, but I find it very interesting, and it is a well written paper, it is recommend reading. It is amazing that the Greenland ice sheet completely melted to 77°N. However, that it occurred during the MPT is less surprising, since it was clearly a climatically unstable time. This geological event does not affect the current climate debate, but it does show that natural forces can cause extreme changes in climate.

Figures 3, 4 and 5 show how much colder glacial periods are in the past 600K years, than they were in the previous two million years. We currently live in a bitterly cold portion of Earth’s history. Something to think about, when governments are trying to force us back into the Little Ice Age (roughly 1300 to 1850) by limiting CO2 emissions.

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May 11, 2022 2:16 pm

Any sign of Biden’s brain?

Gordon A. Dressler
Reply to  Scissor
May 11, 2022 2:44 pm

My understanding is the scientists involved are far from completing their microscopic examinations of the ice cores.

Reply to  Scissor
May 11, 2022 5:52 pm

They didn’t actually do any Microbiology work or nano particles search on the samples unfortunately !

Reply to  Don
May 12, 2022 11:39 am

If they had, they might have found Biden’s brain

Tom Halla
May 11, 2022 2:25 pm

Considering the Little Ice Age was known for war, pestilence, and famine, anyone who thinks that was some sort of Golden Age of climate has serious problems.

Gordon A. Dressler
Reply to  Tom Halla
May 11, 2022 2:54 pm

Most AGW/CAGW alarmists indeed consider it to have been a “Golden Age” for climate because there was, simply put, no large scale sources of anthropogenic CO2 emissions . . . and hence, no possibility for there to have been climate change™ back then.

On the other hand, other AGW/CAGW alarmists—notably among them Michael Mann—are working feverously, night and day, to erase or adjust-away the Little Ice Age from climate records.

peter schell
Reply to  Gordon A. Dressler
May 12, 2022 6:27 am

I thought they already had.

Don’t they claim the little ice age, and the Medieval warm period, were just regional, and the actual climate of the earth was far more moderate and it is only recently that the entire world began to warm at an unprecedented rate?

I find it a bit like arguing about bible stories with a true believer. The bible is factual because the bible says it is.

Reply to  Tom Halla
May 12, 2022 7:43 pm

Aren’t war, famine, and persilence major pastimes of today’s world?

Rud Istvan
May 11, 2022 2:39 pm

Saw this paper about the bottom of the ‘lost’ Camp Century ice core when it first came out. Thanks to Andy for brining it here.

Figure 5 gives a further reason why it was tundra at the bottom of the core, so no year round ice. Until about 1mya, the glacial duration was about 45ky, yet the interglacials were about as now at 10-15ky. Then ‘suddenly’ the glacial duration switched to about 110ky. So to a first order approximation, at the bottom of Camp Century core there was less than half as much ice to melt, but the same amount of time to melt it.

I have searched, but not yet found a plausible reason for the switch to doubled glacial duration. Plate tectonics should be too slow. The Black Sea deluge happened way after. It just did, and we don’t know why.

Reply to  Rud Istvan
May 11, 2022 3:03 pm

I have searched, but not yet found a plausible reason for the switch to doubled glacial duration.

The most likely reason is very simple. The planet has been cooling for the past 55 million years. After Antarctica glaciation the cooling accelerated, and during the Pleistocene the cooling approached 1ºC per million years. Antarctica is limited by the ocean, but the Arctic is surrounded by land. As ice sheets expanded outside the Arctic the amount of ice became too large to melt during the warming phase of a Milankovitch obliquity cycle (41 kyr). The planet started skipping one cycle until so much ice accumulates that it triggers powerful negative feedbacks, like a spring pulled too far. For example much of the ice accumulates over continental platforms that are inundated as the sea level rises, and water quickly melts lots of ice. The result is that the cycle becomes 82 kyr long. But also interglacials become warmer when they are finally produced. When eccentricity is very high the 41 kyr periodicity briefly happens. The final average is around one interglacial every 73 kyr. The 100 kyr cycle is a myth. The last glacial period was unusual as it skipped two interglacials so the past interglacial happened 123 kyr before the Holocene. This had not happened before, but the astronomical reasons are clear. Tzedakis has explored them.

Once this interglacial is over we will have to wait about 70,000 years for the next (82 kyr spacing minus 12 kyr Holocene).

Since the MPT it seems the planet is no longer cooling, but stable in the present very cool condition. We’ll have to wait tens of millions of years before the ice age is over.

So be patient with the climate.

Rud Istvan
Reply to  Javier
May 11, 2022 3:33 pm

Thanks Javier. That is the first cogent explanation I have read after years of searching.

Reply to  Javier
May 11, 2022 5:16 pm

The more interesting question is – what caused the end of the last glacial episodes?

It was linked to the NH winter warming cycle but that cycle was less intense than previous cycles where glaciation only moderately reversed and then continued in the next cooling phase.

Nicholas McGinley
Reply to  Javier
May 12, 2022 9:53 am

One thing to note is that the location is not far from the coastline.
So this statement:
It is amazing that the Greenland ice sheet completely melted to 77°N”,

is not supported by the data.
All that was required is for the margin of the ice to move inland a ways.

Nicholas McGinley
Reply to  Andy May
May 12, 2022 2:37 pm

Ok, that is different of course.
The evidence shows that at that location, plants were growing so it can be inferred there was no ice for some extended period of time.

Reply to  Rud Istvan
May 11, 2022 4:57 pm

Rud Istvan

Unless you get to conclude to a clear simple logical definition of Climate, than there will very unlikely to be a sadisfactory answer to your question.

Well, perhaps!


Rud Istvan
Reply to  whiten
May 11, 2022 5:20 pm

There has been an official AMS one I have used for decades:
climate is the envelope of weather over a period of at least 30years.

Now a legit criticism of that is, since many roughly 60 cycle weather patterns are discernible, it should double. But if warmunists did that, climate alarm would collapse.

Reply to  Rud Istvan
May 12, 2022 8:10 am

Yep, there you have it Rud… no hope you appreciating ever an answer to your question!

M. Cycles climate theory cares not about the 30 years weather cycles, and any other explanations outside the premise of this theory in regard to real Climate in long term, will also have no much chance with you or any one regarding climate as a 30 years weather cycles.

A 30 years weather cycle in climate terms only useful supposedly only for understanding and addressing the supposed modern era (anthropogenic) Climate Change.

The main and only defining parameter of Climate is the thermal variation in long term (millennia scale), either of the (global) Atmosphere or more precisely/complex one of
the (global) Surface-Atmosphere coupling.

And also there is other important and essential other parameters and indicators, in tight relation to Climate, to address, analyze, theorize and hopefully better understand Climate.

Such as:

Cryosphere variation, global ice content variation, sea level variation,
atmospheric CO2 concentration variation, the aridity factor variation.
All considered in long term.

Maybe, if you address and consider the definition of Climate in this particular way, you may have a better chance on reaching an answer to your question.


Last edited 1 year ago by whiten
Reply to  Rud Istvan
May 11, 2022 5:10 pm

about as now at 10-15ky

Half a precession cycle.

The globe entered the current cycle of glaciation about 500 years ago when perihelion last occurred before the austral summer solstice.

Boreal winters are now in a cooling phase and that means more NH winter precipitation as snow. Not yet accumulating but that will be observed within the current millennium. Without intervention, the land masses abutting the North Atlantic will again be covered in mile high ice that will persist for three or four precession cycles.

Gordon A. Dressler
May 11, 2022 2:42 pm

Hmmm . . . in the above article I did not see any reference to “all that liquid water” that others claim exists under the Greenland ice sheet, at the ice/land interface, that is asserted to be causing all that “slip slidin’ away” (with tip of the hat to Paul Simon for the phrase) and the asserted resulting “accelerated” loss of ice volume.

Maybe it’s there and just not revealed by the few ice core samples taken down to bedrock, as indicated in the article’s Figure 1?

Rud Istvan
Reply to  Gordon A. Dressler
May 11, 2022 3:38 pm

Whether or not there is liquid water under the Greenland Ice Sheet, it can NEVER ‘slip slide’ away. Greenland geologically is bowl shaped, and the vast majority of its ice in inside the rocky bowl.
Illustrations and explanations in essay ‘Tipping Points’ in ebook Blowing Smoke.

Reply to  Rud Istvan
May 11, 2022 4:24 pm

This is what the topography of Greenland looks like without ice.

Gordon A. Dressler
Reply to  RexAlan
May 11, 2022 5:32 pm

RexAlan and Rud Istvan,

Hmmm . . . ancient impact crater from an oblique asteroid or comet strike, since filled in with ice? It would have to have been a huge one!

Even though that graphic is likely exaggerated in the vertical dimension, I don’t believe the uniformly encircling border elevation could be explained by the actions of plate tectonics acting on the Greenland land mass.

Any geologist care to comment on forces that caused Greenland’s bowl shaped land surface?

Yes, I do need to read “Blowing Smoke”.

Reply to  Gordon A. Dressler
May 11, 2022 5:39 pm

The weight of the ice sheet has sinked the inland of Greenland giving it a bowl shape. Most of the northern high latitudes are still rebounding thousands of years after that weight was lifted by the Holocene melting. The weight of the ice sheets is just unbelievable.

Bryan A
Reply to  Javier
May 12, 2022 5:36 am

And much of the interior is below sea level so the central portion is far more likely to become either a large lake or possibly inland sea with salt water intrusion. Kind of like a large archipelago

Gordon A. Dressler
Reply to  Javier
May 12, 2022 7:47 am

But how to explain the rather sharp vertical delineation on the exterior surfaces of the bowl-shape . . . why isn’t the height-to-base ratio on the outside of the elevated bowl “edges” much more gradual than what in seen on the inside of the bowl “edges”?

The color coding of the (probably) exaggerated vertical scale indicated in RexAlan’s posted graphic shows a much more rapid drop in height on the exterior surface of edges than on interior surface of the same edges.

Would the underlying rock have THAT MUCH resistance to lateral displacement resulting from the pressure of the interior ice mass?

Reply to  Gordon A. Dressler
May 12, 2022 8:21 am

But how to explain the rather sharp vertical delineation on the exterior surfaces of the bowl-shape

That I don’t know, but I would guess that by the same mechanism that the sides of a cirque glacier are also steep. Lateral displacement of the ice on its way out is very powerful at eroding rock.

Greenland can be considered as a huge cirque glacier with several exits to the sea.

Last edited 1 year ago by Javier Vinós
May 11, 2022 2:43 pm

Has Greenland’s position on the planet changed in the past million years?

Gordon A. Dressler
Reply to  Tom.1
May 11, 2022 2:58 pm

No. Ref: Scotese’s beautiful animation of plate tectonics at

Dave Fair
Reply to  Gordon A. Dressler
May 11, 2022 5:58 pm

Fantastic! Particularly impressive was the rapid progression of the chunk later called India slamming into Asia, shoving the Himalayas higher and higher.

Nicholas McGinley
Reply to  Gordon A. Dressler
May 12, 2022 10:27 am

He has a whole channel with dozens of these…just click on his name and go to the videos tab.
This one is actually six years old…he has many newer ones.
(3) Christopher Scotese – YouTube

Richard Page
Reply to  Tom.1
May 11, 2022 3:01 pm

Not much in the past million years – it is moving steadily northwards but has only moved about 08 degrees in the past 100 million years.

May 11, 2022 2:43 pm

Figures 3, 4 and 5 show how much colder glacial periods are in the past 600 million years

That million should be thousand

May 11, 2022 4:12 pm

Anyone else wondering what MIS abbreviates? I did, and the original paper defines it as Marine Isotope Stage.

Reply to  Wayne Raymond
May 12, 2022 7:48 am

While there’s only 16 protons in every oxygen atom, in any one atom, there’s a variable number of neutrons, the different neutron counts are called the (isotopes) of oxygen. If there are more neutrons in an atom, that is a heaver atom, if less, it is a light atom. As you can guess, a water molecule H2O with lighter oxygen is more likely to evaporate than a heavier atom. When there’s more ice tied up in glaciers, there’s less light oxygen atom water molecules in the sea, because the glacial ice was made from snow, which is evaporated water, which is more likely to be a water molecule with light oxygen than a heavy oxygen. Then, the corals and other calcium shelled animals make calcite CaCO3 from the existing sea water, calcite crystals also precipitate naturally from warm sea water. The shelly bodies of these animals, and precipitated minerals are preserved in the bottom sediments i.e. limestone. Sediment drilling programs drill through the limestone, and measure the weight of the oxygen isotopes in the calcite (CaCO3) in the limestone. This gives us a good idea about how much light oxygen was missing from sea water, which tells us how much light oxygen was was tied up in glacial ice. When the ice melts, the light water is returned to the sea, and the amount of light oxygen water is recorded in the sediments.

This is how we know the dates of the glacial and interglacial periods.

Reply to  Lil-Mike
May 12, 2022 12:21 pm

16 protons?
A bum boatie, here, missed something in Chemistry, I fear.


May 11, 2022 5:02 pm

Something to think about, when governments are trying to force us back into the Little Ice Age (roughly 1300 to 1850) by limiting CO2 emissions.

CO2 has zero direct impact on the energy balance.

More CO2 is altering the biosphere, which affords a significant benefit in moderating local weather and even larger scale weather patterns by increasing atmospheric moisture levels.

Clearing forests to make way for wind turbines and solar farms will be detrimental to the climate while returning more CO2 to the atmosphere is beneficial.

Reply to  RickWill
May 11, 2022 5:46 pm

This is an interesting study on the contribution trees in the Amazon make to large-scale weather patterns:

The reasons for the delayed onset of the wet season are not completely understood, but the new study adds evidence to the idea that deforestation is playing a role. Reducing the trees available to produce moisture would naturally reduce the forest’s cloud-building capacity. If deforestation slowed the increase in transpiration to the point that it could no longer trigger a rainy season, rains wouldn’t begin till the ITCZ arrived at the end of the year.

Deep convection is the reason water remains on the surface of the Earth. It is a vital process for all life on Earth. Trees and associated soil moisture enhance deep convection over land by adding to the level of precipitable water. That means cyclic convection begins earlier and extends the wet season.

Reply to  RickWill
May 11, 2022 5:51 pm

CO2 has zero direct impact on the energy balance.

Is that an article of faith? Climate is a religion for a lot of people. The evidence that we have is that it should have an effect different from zero. We just don’t know how much effect. But we are doing the experiment, aren’t we?

Thus human beings are now carrying out a large scale geophysical experiment of a kind that could not have happened in the past nor be reproduced in the future. Within a few centuries we are returning to the atmosphere and Oceans the concentrated organic carbon stored in sedimentary rocks over hundreds of millions of years. This experiment, if adequately documented, may yield a far-reaching insight into the processes determining weather and climate.

Revelle, R. and Suess, H.E., 1957. Carbon dioxide exchange between atmosphere and ocean and the question of an increase of atmospheric CO2 during the past decadesTellus9 (1), pp.18-27.

Reply to  Andy May
May 11, 2022 10:19 pm

The feedback through deep convection is so powerful that it swamps any other other radiative effect.

Open ocean surface temperature cannot exceed 30C for more than a few days. At 30C the surface insolation matches the surface heat loss so that is where it limits. Until CO2 gets sufficient to alter the atmospheric mass, it is not going to change the energy balance.

Sea ice still persists at both poles to limit heat loss so the lower temperature is also reaching its limit.

No climate model incorporates deep convection and its temperature limiting process. This is the most important climate process for life existing on Earth and it is not even considered in climate models.

May 11, 2022 5:35 pm

Awesome post Andy…👍🍻

I referenced the Christ paper in this post…


However, it definitely merited a dedicated post… 🍻

Reply to  David Middleton
May 11, 2022 5:47 pm

Thanks Dave

Geoff Sherrington
May 11, 2022 7:29 pm

“Diamict”, that word on the images of bottom-of-hole samples, might not be known to non-geological people. Here is one description from a net search:
“Diamict (diamictite when a rock) is a nongenetic umbrella term for any poorly sorted deposit regardless of depositional environment. Man-made concrete is a diamictite. Sliding glaciers produce a wide range of diamicts that contain admixtures of most textural classes ranging from clay to large boulders. These diamict facies are specifically identified as till because they were deposited directly by ice. A till (tillite: rock) is a specific genetic term for a diamict deposited directly from ice either terrestrially on land or in the glaciomarine realm.” Geoff S

May 11, 2022 9:22 pm

Crazy, he. We need more CO2 not less.

May 12, 2022 10:00 am

Where there are plants there are usually people.

Clyde Spencer
May 12, 2022 10:06 am

The basal silty ice can probably be explained by the ice shearing over the top of the irregular bedrock topography. It was quite evident in the tunnel at Camp Tuto where I worked.

May 12, 2022 9:08 pm


Thanks for bringing forward a science article that appears to be politically unbiased and presents basic facts. If I were Elon Mush I would fund many more of these types of blog articles.

Ian MacCulloch
May 12, 2022 11:22 pm

This is a most important paper. The authors are to be greatly congratulated.

The cores all point to continuous ice accumulation for their respective locations with the oldest at Camp Century (ca 1,000,000 yrs BP) and the most recent GISP2 (428,000 yrs BP). These rates of accumulation are quite constant with little or no gaps in between years let alone thousands of years. This all points to the constant accumulation of ice regardless of the changes in other events such as CO2 levels, sea levels, etc. This phenomenon is also present in Vostok 3 where the age at the base is approximately 830,000 years BP.

So Vostok and Camp Century when fully drilled and dated should give an approximate time intersection of 1,000,000 years BP. All well and good and suggests a major climate event turnaround in both Greenland and Antarctica.

However, GISP2 located about 1,000 km south of Camp Century has time stratigraphic issues given that the basement intercept is much younger than those at Camp Century and Vostok 3.

GISP2 reports similar climates to those of the other main control cores.

So the contradiction in all of this is that there are no measurable changes in the rates of accumulation of the ice cores. Certainly obvious changes in the accumulation rate that would correlate with the 6 or so glacial cycles since the formation of the ice column at Camp Century are characteristically absent.

So perhaps the base of the Pleistocene should be timed to coincide with the basement evidence of Camp Century and indeed Vostok 3 or whenever a core hole in this area is drilled through to the basement.

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