History of early polar ice cores

From time to time the US military produce historical works.

Chester Langway[1] in retirement wrote this work to commemorate a 50th anniversary. Published by the US Army Corps of Engineers.

Ice core CO2 and temperature, lead or lag, ongoing saga

Argument over whether the two long ice cores, EPICA and Vostok are evidence of CO2 leading or lagging temperature has been going on ever since the core data was published. I assume the reader knows this.

A snippet has turned up as a result of an article at Bishop Hill.

Republished images as an aide memoir for the subject

Figure 1, click full size

Plots, own work. Pertinence, read on.

The Bishop Hill article is from an anonymous teacher of statistics where a cross-disipline dispute arose.

What if the Vostok core is like polar ice?

With the last post I hope I demonstrated how a very simple regular function, a planet orbit, causes a more complex modulation of sea ice, something which does not seem to be generally understood.

Look back a couple of posts and you will see Vostok ice core plots.

What I have done now is flip the temperature proxy data upside down. This ought to roughly represent ice and puts the data the same way around as the earth sea ice plots. More ice is upward, melt is downwards.

I then used a very crude approximation to some kind of orbital signal, actually locks in at 103ky.

This is known wrong in relation to orbits (explain more in a moment) but food for thought.

Do you now see why the widespread notion that sharp melts cannot come from a simple stimulation is a highly questionable assumption? It should be considered feasible and with no magic or particular non-linearity.

Assistance

I would appreciate assistance with very long orbital period calculation. I have the capability to carry out some novel experimentation using accurate orbital data, which I do not have.

One of the very interesting features is apparently the variation in the eccentricity of the earth orbit on these very long timescales, ie. it varies with at least two periods. I hope the reason why this is so interesting is not lost on the reader.

Epica Vostok resampled composite

I won’t say much here now, busy.

This seems to confirm a huge date mistmatch between the two sets of ice core data.

This is a deliberately large plot. Contact me if you need data or help.

Composite of signal processing resampled data from two ice cores

Simplest way to provide data is an export to XLS format of work, warts and all.

Contains usable resampled data and originals

Added later, easiest way to provide data is export to XLS, is scruffy workfile

epica-1

Vostok ice core, part 2

See part 1 if you haven’t.

Seemed a good test to see if I could reproduce the temperature vs. CO2 lead lag result but using signal processing, data resampling. Turns out  the CO2 data is even worse than the isotope ratio temperature data, fewer data points and sampled at different dates.

Easy. I applied identical processing to both datasets and then figured out how to time shift one of them. To my surprise there is a very high correlation, r2=0.82, at least given the preprocessing used. The quick and dirty way to do the time shift was apply an offset at the decimate stage, simply picks off data at a different point. (this is valid)

If I have done this right it is about 1,500 years for best fit of rise and fall. I then aligned the datasets and plotted (Y axis reacaled and offset CO2 by hand so the data roughly matches on one scale)  for an eyeball.

Time co-incident plot of temperature and CO2

There is obviously a lot going on but there it is visibly on one plot.

A net dig shows a work by Jo Nova (know the name, no idea who she is)

http://joannenova.com.au/global-warming/ice-core-graph/

That says 800 years and seems to cite others.

Ref

http://www.ncdc.noaa.gov/paleo/metadata/noaa-icecore-2453.html

ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/vostok/co2nat.txt

Vostok ice core, part 1

An ongoing development is better handling irregularly sampled data. This is a very hard problem with no pure solution.

After a lot of investigation and experimentation I have concluded that NDFT/NDFT are of little use, solve nothing, kicks straight back into the input data must be good. Usually involved is approximating and other heuristics.

Looks hard. Run away.

Raw data overlaid with a resampled dataset

For what I am doing a good solution is fix up the dataset using signal processing, kind of trivial, although it will seem black magic to outsiders. (why no blue, pink, white, transparent magic?)

A key is keeping the human brain in the loop, each case is likely to be different with no one size fits all.

I’ve coded up the hard part for a human as an extension of one software package.

Seems to work nicely, as above, the test dataset. Vostok original data sampling ranges from 60 through 600 years.

An XLS with the original data and resample dataset is here vostoke-temperature-a

Reference

 http://www.ncdc.noaa.gov/paleo/metadata/noaa-icecore-2453.html

 ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/vostok/deutnat.txt

The dataset is now clean and trivial for normal tools.

And for those who like first difference…

Hiding anything? Nope. The 1st diff does of course have high frequency noise but is surprisingly small. Only clear term in the part not shown is ~4044y. No idea what that is if anything.

More to be done, always is.