In 1997, the 121 m Lomonosovfonna ice core was drilled in Svalbard. As of mid-2009, when Hu McCulloch and I wrote CA posts on this core, nothing had been published on
O18 values prior to AD1400 nor had any Lomonosovfonna data been archived, even for the post-1400 period.
Both Hu McCulloch and I, in separate CA posts here and here, speculated that the withheld O18 values prior to AD1400 would elevated values. A digital version of the pre-1400 data became available this week in connection with Hanhijarvi et al and confirmed our surmise, as shown below.
The figure below shows Lomonosovfonna O18 values back through the MWP as calculated from data in the SI to Hanhijarvi, Korhola and Tingley. As Hu and I had surmised, the O18 values prior to AD1400 (denoted by dotted line) were elevated.
Figure 1. The Hanhijarvi et al SI provided reconstructed temperature at Longyearben using Lomonosovfonna. The post-1400 portion was a linear transformation to O18 data at NOAA (used in Tingley and Huybers 2013). The O18 plotted here used the linear transformation to recover the underlying O18 values.
Lomosovfonna O18 values after AD1400 had been shown in a number of articles by Isaksson and coauthors.
Hu’s and my interest in pre-1400 Lomonosovfonna data had been prompted in 2009 by the publication of a multiproxy reconstruction of sea ice by Macias Fauria and coauthors, including Elizabeth Isaksson, claiming that sea ice was unprecedented since AD1200. In the post, I observed that a related article by the coauthors (Grinsted et al 2006) showed that “washout indices” at Lomonosovfonna were at much higher than modern levels prior to AD1200, but, by sheer coincidence, the reconstruction began in AD1200.
The reconstruction used d18O measurements from Lomonosovfonna, Svalbard, but Macias Fauria refused to provide the data (see CA post here). Macias Fauria said that the data had to be obtained from Elisabeth Isaksson, disregarding the fact that Isaksson was a coauthor of the article.
Hu McCulloch took up the issue in a CA post entitled Svalbard’s Lost Decades, forcefully challenging Grinsted, who had commented on other CA threads, to explain the omission of this portion of their record. Grinsted responded in comments, but failed to provide a satisfactory explanation. Nor was Grinsted more responsive to requests for pre-1400, also pointing the finger at Isaksson.
Lomonosovfonna was again used later in 2009 in a multiproxy reconstruction by Kinnard et al. Kinnard et al provided an excellent archive, including a digital version of post-1400 Lomonosovfonna that is a slightly smoothed version of the data now available.
The post-1400 version of Lomosovfonna was also used in 2009 by Tingley in the first draft of what was recently published as Tingley and Huybers 2013.Tingley and Huybers 2013 discuss a post-1400 reconstruction using ice core O18, with a network almost identical to Kinnard’s, including the post-1400 portion of Lomonosovfonna. I’ll return to this reconstruction in a separate post.
In May 2011, Isaksson archived the post-1400 data at NOAA (see here), citing Macias Fauria et al – making me wonder whether Macias Fauria used Lomonosovfonna data in their reconstruction between 1200 and 1400.
In July 2011, in a little noticed article (Divine et al 2011 here), Isaksson and coauthors showed pre-1400 data in the following graphic (but did not archive the data):
Isakkson and coauthors observed:
However, both the reconstructed winter temperatures as well as indirect indicators of summer temperatures suggest the Medieval period before the 1200s was at least as warm as at the end of the 1990s in Svalbard.
Later in 2011, I reviewed the comprehensive Arctic O18 data from Kinnard et al 2009 here. I observed that the Kinnard Hockey Stick was not observable in the long O18 data and therefore had to come from something else, illustrating this with the following graphic.
Figure 4. CA comparison of long O18 data from Kinnard et al 2009 to their reconstruction.
In their SI, Tingley and Huybers 2013 show a post-1400 reconstruction using Arctic O18 values, but draw opposite conclusions. I’ll return to this in another post.
Postscript: The dating of the bottom portion of the core appears to have changed dramatically between Macias Fauria et al 2009 and Divine et al 2011, increasing the earliest dates by about 400 years (from the 12th century to about AD770). Because of the exponential thinning of ice cores, early dates are tremendously sensitive (particularly in short cores) to the estimate of the thinning parameter, as shown in the following graphic from Divine et al 2011: