by Hans Erren, Posted 10 February 2004
For the compaction and inversion simulation we take a simple A/age compaction relationship, the actual formula doesn't matter really as will be clear further on. As input dataset we take an accumulation that varies in a cyclical way between 0.5 and 2.5 meters:
Using a compaction factor of 0.03*age yields:
Now If we would simply use the inverse function, the reconstruction would be perfect. However, if we round the compacted data to the nearest centimeter, a dramatic change gets visible in the inverted data.
Note that the early reconstruction even exceeds the input!
If we compare this simulation with the actual reconstructed data of core 1, the similarity is striking. (Black crosses: simulation, red crosses: Quelccaya core 1 reconstruction):
Rounding of layer thicknesses to the nearest centimeter leads to accumulation reconstruction artifacts. As the used compaction formula is not mentioned in TMBK1985 nor at the NOAA archive, Lonnie Thompson was asked for the original core log data. After a reminder he responded as follows on 10 March 2004:
So we are are left with an interpreted accumulation log, without direct access to the core log data. The worrisome side is that this interpreted dataset is a cornerstone of the preferred millenium climate reconstruction of the IPCC.Dear Hans: Just returned from China! Unfortunately, those logs are all hand done. These data where not put on electronic format. We have just redrilled the Quelccaya ice cap in 2003 and brought back two frozen ice cores and will be producing a new log based on this new data. Unfortunately, right we are processing Bona-Churchill ice cores and the new Quelccaya and Coropuna cores are in the cue. Sorry I can not be more helpful on these old data sets. best wishes, Lonnie
 Mann, M.E., R.S. Bradley, and M.K. Hughes. 1999. Northern hemisphere temperatures during the past millennium: Inferences, uncertainties, and limitations, Geophysical Research Letters 26:759-762. http://www.people.virginia.edu/~mem6u/mbh99.html
 Thompson, L., 1992, Quelccaya Ice Core Database. IGBP PAGES/World Data Center-A for Paleoclimatology Data Contribution Series # 92-008. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA. ftp://ftp.ngdc.noaa.gov/paleo/icecore/trop/quelccaya/q83cor1.txt
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