Chronology: 2 – Greenland and Oxygen Isotopes

The mainstream chronologies and temperature reconstructions derived from the Greenland ice cores are primarily based upon the analysis of “δ18O” [aka “delta 18O”] values.

Ice-core-isotope

The first step towards calculating a “δ18O” value is to determining the ratio of Oxygen18 to Oxygen16 found in a sample of water extracted from the ice core.

delta 18O

The “δ18O” value then calculated as a relative deviation from a selected standard value.

delta 18O calulation
http://www.iceandclimate.nbi.ku.dk/research/past_atmos/past_temperature_moisture/isotopes_delta_notation/

A four year benchmarking exercise clearly shows the annual variability in “δ18O” values and their close association with temperature on the Greenland ice cap at an altitude of about 3,200 metres.

delta 18O benchmark
http://www.iceandclimate.nbi.ku.dk/research/strat_dating/annual_layer_count/ice_core_dating/

This very limited benchmark clearly establishes for the early 1990s:

1) A normal range of “δ18O” values between -45.5 and -25.5
2) A minimum “δ18O” value of -45.5 during the winter.
3) A maximum “δ18O” value of -25.5 during the summer.
4) A midpoint “δ18O” value of -35.5 for an average year.

A ten metre sample from the Central Greenland ice core Crête [which is deemed to cover the period 1939 to 1956] is very supportive of the benchmark midpoint “δ18O” value of -35.5 that was established for the early 1990s.

However, the minimum and maximum values are less extreme and this indicates that annual ice core samples tend to merge towards their midpoint “δ18O” value with depth.

Central Greenland ice core Crête

Having established benchmark values for “δ18O” and completed a reality check on the Greenland Crête ice core we are now equipped to analyse the premier ice core from Greenland: NGRIP.

Ngrip-epica-do18
http://en.wikipedia.org/wiki/North_Greenland_Ice_Core_Project

The most surprising aspect of the NGRIP “δ18O” values [graphed in black above] is that they fall almost entirely within the GRIP benchmark “normal range” of -45.5 to -25.5.

Initially the NGRIP ice core “δ18O” are close to the benchmark midpoint “δ18O” value of -35.5.

The subsequent plunge into an oscillating range between [roughly] -45 and -37 has been deemed by the mainstream to represent the last “ice age” with a midpoint annual temperatures [based upon the benchmark] ranging from -34C to -50C.

However, the NGRIP data does also allow for an alternative hypothesis where the plunge in “δ18O” values is associated with a “warmer climate” where snowfall was predominately limited to winter.

The two opposing scenarios should create signatures that are easy to differentiate in the ice core.

The mainstream “ice age” scenario is associated with huge annual ice accumulations that fed the vast ice sheet covering parts of North America. This implies that any dust entrapped within the snow during the “ice age” would be sparsely distributed and the associated ice core should be visibly “clear”.

The alternative “warmer climate” hypothesis is associated with an ice core that is visibly “dirty” because any entrapped dust would become concentrated in the remnant icecap during the summer melt season. The remnant ice cap may have partially retreated to the uplands of Greenland or have been confined in Greenland’s central lakes as residual multiyear ice.

Topographic_map_of_Greenland_bedrock
http://en.wikipedia.org/wiki/Greenland

The NGRIP “δ18O” data indicates that the climate transition occurred approximately halfway down the ice core at a depth of about 1,500 metres.

NGRIP_depth and d18O
http://www.iceandclimate.nbi.ku.dk/research/climatechange/glacial_interglacial/

Surprisingly, the Greenland GISP2 ice cores provide a visual clue that the NGRIP ice core might be “dirty” below 1,500 metres.

Ice Cores by Depth
http://earthobservatory.nasa.gov/Features/Paleoclimatology_IceCores/

The Greenland GRIP ice core from 3,029 metres also suggests that the NGRIP ice core might be “dirty” below 1,500 metres.

Frozen Annals - GRIP last ice core from 3029 metres
FROZEN ANNALS – Greenland Ice Cap Research
Willi Dansgaard
http://www.iceandclimate.nbi.ku.dk/publications/FrozenAnnals.pdf

The following radar image of the Greenland ice cap shows that [roughly] the lower half of the ice cap is “dirty” because it produces a stronger radar reflection [lighter in the image].

Greenland Radar

The following radar image of the Greenland NGRIP ice cap definitively confirms that the lower half of the NGRIP ice core is “dirty” because it produces a strong radar reflection.

Greenland NGRIP Radar

This 150 km long section of radar data collected around NorthGRIP shows a flat bedrock (the thick dark line close to the bottom of the picture is the bedrock echo) but undulating internal layers. The shape of these layers is created by changing basal melt rates along the sections. Where the layers dip down the basal melt rate is highest. Credit: CReSIS

http://www.iceandclimate.nbi.ku.dk/research/flowofice/internal_layers/

Unfortunately, for the mainstream, the evidence is firmly stacked against any “ice age” being recorded in the Greenland ice cap because the “dirty” evidence shows the climate was warmer before the Holocene.

Anybody left wonder about the final upturn in the NGRIP “δ18O” to -32 should remember that NGRIP drilled to a depth of about 135 metres below sea level and encountered water. The “δ18O” of -32 indicates that this was melt water with an appropriate “δ18O” for mid-July 2003.

Unusually, there is melting at the bottom of the NGRIP core – believed to be due to a high geothermal heat flux locally.

http://en.wikipedia.org/wiki/North_Greenland_Ice_Core_Project

On July 17th 2003 the drilling at NorthGRIP reached bedrock at a depth of 3084.99 m , and the drilling was terminated.

http://www.gfy.ku.dk/~www-glac/ngrip/index_eng.htm

Therefore, the NGRIP ice core “δ18O” data does not provide any supporting evidence of an “ice age” and the NGRIP ice core data does not terminate in the Eemian interglacial.

Overall, the mainstream narrative represents a massive “confirmation bias” failure.

Footnote:
The density of ice approaches a peak of 917 kg/m3 in ice cores at a depth of about 200 metres and [therefore] can be disregarded as an issue when analysing the radar images below this depth.

When a density of 830 kg/m3 is reached at a depth of approx. 80 m, all air passages between the crystals are sealed off so that air only exists in closed bubbles. This defines the transition from firn to ice. With increasing depth, the air in the bubbles is compressed and the density approaches 917 kg/m3 which is the density of glacier ice. It is impossible to compress the ice any further, and at greater depths, the thinning of the layers only happens through deformation of ice by ice flow.

Ice Density

http://www.iceandclimate.nbi.ku.dk/research/flowofice/densification/

See also:
Chronology: 1 – Ice Cores
https://malagabay.wordpress.com/2013/06/18/chronology-ice-cores/

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5 Responses to Chronology: 2 – Greenland and Oxygen Isotopes

  1. malagabay says:

    NASA has an interesting article regarding the 2012 Greenland summer melt season.

    Greenland’s surface ice cover melted over a larger area than at any time in more than 30 years of satellite observations.

    Nearly the entire ice cover of Greenland, from its thin, low-lying coastal edges to its 2-mile-thick center, experienced some degree of melting at its surface, according to measurements from three independent satellites analyzed by NASA and university scientists.

    On average in the summer, about half of the surface of Greenland’s ice sheet naturally melts. At high elevations, most of that melt water quickly refreezes in place. Near the coast, some of the melt water is retained by the ice sheet and the rest is lost to the ocean. But this year the extent of ice melting at or near the surface jumped dramatically. According to satellite data, an estimated 97 percent of the ice sheet surface thawed at some point in mid-July.

    This extreme melt event coincided with an unusually strong ridge of warm air, or a heat dome, over Greenland. The ridge was one of a series that has dominated Greenland’s weather since the end of May. “Each successive ridge has been stronger than the previous one,” said Mote. This latest heat dome started to move over Greenland on July 8, and then parked itself over the ice sheet about three days later. By July 16, it had begun to dissipate.

    Even the area around Summit Station in central Greenland, which at 2 miles above sea level is near the highest point of the ice sheet, showed signs of melting. Such pronounced melting at Summit and across the ice sheet has not occurred since 1889, according to ice cores analyzed by Kaitlin Keegan at Dartmouth College in Hanover, N.H. A National Oceanic and Atmospheric Administration weather station at Summit confirmed air temperatures hovered above or within a degree of freezing for several hours July 11-12.

    “Ice cores from Summit show that melting events of this type occur about once every 150 years on average. With the last one happening in 1889, this event is right on time,” says Lora Koenig, a Goddard glaciologist and a member of the research team analyzing the satellite data. “But if we continue to observe melting events like this in upcoming years, it will be worrisome.”

    http://www.nasa.gov/home/hqnews/2012/jul/HQ_12-249_Greenland_Ice_Sheet_Melt.html

    Steven Goddard follows up on this NASA article and very kindly includes a graph of the Mean Daily Temperature at the Greenland Summit Camp for 2012-13.

    Mean Daily Temperature at the Greenland Summit Camp for 2012-13
    Understanding The Greenland Ice Sheet Meldown
    http://stevengoddard.wordpress.com/2013/06/29/understanding-the-greenland-ice-sheet-meldown/

    The graph clearly shows that the GRIP Benchmark “interglacial” temperature range should be calibrated from [at least] 0C down to -60C.

    This implies an interglacial “δ18O” range of -23.00 down to -50.50 which boldly underlines the notion that the “ice age” was warmer in Greenland with winter snow and a summer melt season.

  2. malagabay says:

    Regarding melting “once every 150 years on average” the Greenland DYE-3 ice core shows melting events in [roughly]: 1960, 1885 and 1820.

    This looks more like “once every 64 years” on average [with 2012 included].

    Greenland DYE-3 Melting Events
    http://www.iceandclimate.nbi.ku.dk/research/flowofice/densification/

  3. malagabay says:

    The benchmark annual “δ18O” signal gradually diffuses with depth and eventually disappears.

    The mainstream report that the annual “δ18O” signal disappears in the GRIP ice core after about 14,000 years which [coincidentally] is at the end of the “ice age” in the GRIP data.

    However, the annual “δ18O” signal could also have disappeared after 14,000 years because the GRIP “ice age” was actually warmer with winter snow and a summer melt season that diffused [melted] the “δ18O” signal.

    The evident volatility of the “δ18O” record in the subsequent “ice age” period is far more supportive of the alternative hypothesis that the “ice age” was in fact warmer than today.

    Greenland GRIP d18O

    GRIP 20 year del18O values back to 122 kyrs BP.
    Chronology is ss09sea or GRIP2001. Not accurate for Holocene.
    Johnsen, S.J., D. Dahl-Jensen, N. Gundestrup, J.P. Steffensen,
    H.B. Clausen, H. Miller, V. Masson-Delmotte, A.E. Sveinbjorndottir,
    and J. White, Oxygen isotope and palaeotemperature records from
    six Greenland ice-core stations: Camp Century, Dye-3, GRIP, GISP2,
    Renland and NorthGRIP, Journal of Quaternary Science, 16 (4), 299-307, 2001

    http://www.gfy.ku.dk/~www-glac/data/grip-ss09sea-cl-20yr.stp

    How far back in time the annual layers can be identified depends on the thickness of the layers, which again depends on the amount of annual snowfall, the accumulation, and how deep the layers have moved into the ice sheet.

    In cores from high-accumulation drill sites like the South Greenland DYE-3 ice core drilling (snowfall about 56 cm of ice equivalent per year), annual layers can still be identified from the stable isotope data about 8000 years back in time, while the annual layers are only barely distinguishable in δ18O data from NGRIP where the annual accumulation is 19 cm.

    http://www.iceandclimate.nbi.ku.dk/research/strat_dating/annual_layer_count/ice_core_dating/

    Due to the diffusion processes, the limit of safe annual layer detection using δ18O / δD measurements is about 8500 years ago in the DYE-3 ice core.

    More favourable conditions at the summit of the Greenland ice sheet has permitted successful identification of annual layers from δ18O data in more than 14,000 year old ice from the GRIP ice core, while the NGRIP and NEEM ice cores cannot in general be dated using δ18O data alone.

    http://www.iceandclimate.nbi.ku.dk/research/strat_dating/annual_layer_count/diffusion/

    The ice core evidence is clearly indicating that the mainstream have [through confirmation bias] completely misinterpreted the historic record and have everything back to front.

    According to the GRIP ice core:

    Greenland has been getting colder for about 10,000 years with a melt season roughly every 64 years.

    Between 10,000 and 15,000 years ago Greenland traumatically moved to a colder climate regime.

    Before 15,000 years ago Greenland experienced a warmer climate with frequent summer melt seasons.

  4. Pingback: Methane Myopia: 5 – Ice Core Science | MalagaBay

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