from: Phil Jones <p.jonesatXYZxyz.ac.uk>
subject: Re: [Fwd: Your Submission]
to: "Bo Vinther" <boatXYZxyz.ku.dk>, k.briffaatXYZxyz.ac.uk, ddjatXYZxyz.ku.dk, hbcatXYZxyz.ku.dk, kkaatXYZxyz.ku.dk, sigfusatXYZxyz.ku.dk, boatXYZxyz.ku.dk
Bo et al,
I went onto the QSJ web site and found the comments from Rev 1, so
am attaching them.
Rev 1 says a lot, but all is positive and shouldn't take too long to include.
Some of the necessary responses will make useful additions to the paper.
A few may even have helped Rev 2. As for Rev 2, they also appear to want
much more detail and much more justification for what has been done. They
also seem to contradict themselves a couple of times. I'm much happier with
fishing than relying on theory, so give me correlations any day!
What would likely placate them the most would be plots with correlations between
SW Greenland, Stykkisholmur and the long Angmassalik record on E Greenland.
The length of the paper will likely increase, so it would be worth considering
putting one or two parts into Appendices if this is possible.
At 02:24 09/07/2008, Bo Vinther wrote:
Dear Phil, Keith, Dorthe, Katrine, Sigfus and Henrik
I have received the reviews on our seasonal O18 manuscript for QSR. As far
as I can see Reviewer 1 is very positive and has some suggestions for
improvements while Reviewer 2 finds the paper too specialized and is
unhappy with the statistics and in general sceptic of the results we
The editor wants us to revise the paper - which I intend to do - but
probably not before late August when I return from the field. Luckily that
does not seem to be a problem.
I will mail you all a draft revised version of the paper as well as a
point by point response to the reviewers comments as soon as I have this
All the best
---------------------------- Original Message ----------------------------
Subject: Your Submission
From: "Quaternary Science Reviews" <JQSRatXYZxyzevier.com>
Date: Tue, July 1, 2008 10:53 am
Ms. Ref. No.: JQSR-D-08-00106
Title: Climatic signals in multiple highly resolved stable isotope records
Quaternary Science Reviews
Dear Dr. Bo M Vinther,
Reviewers have now commented on your paper. You will see that they are
advising that you revise your manuscript. Both referees see important and
novel work in your paper but raise some significant issues regarding the
processing,interpretation and presentation of the data. Although referee
1 suggests that the paper is too specialised for QSR, I disagree and think
that a suitably revised paper has the potential to make an important
contribution to the journal.
I ask that if you wish to revise your paper, you submit a detailed
response to the specific comments raised by each referee. It is likely,
given the nature of the comments raised, that I will send the revised
manuscript out for re-review.
For your guidance, reviewers' comments are appended below.
To submit a revision, please go to http://ees.elsevier.com/jqsr/ and login
as an Author.
Your username is: bmv
Your password is: vinther6573
On your Main Menu page is a folder entitled "Submissions Needing
Revision". You will find your submission record there.
Quaternary Science Reviews
Reviewer #1: see attached pdf file
Reviewer #2: The authors separate high-resolution isotope records from 20
ice cores in Greenland (14 after stacking) into winter and summer
timeseries, on the basis of correlations with Greenland and Iceland
instrumental temperature records. They argue that the winter data are more
spatially coherent than summer data, and have a stronger climate signal
(despite more noise in winter). They then use 3 long records to extend the
analysis back to ~600 AD. The most interesting result is the better
correlation of winter isotope timeseries with borehole temperature
inversions than summer and annual timeseries, but the differences are seen
most readily before ~1300 AD. Curiously, the winter isotope data exhibit a
millennial-scale cooling trend that is similar to the well-known NH
temperature reconstructions, which are primarily derived from summer
sensitive tree-rings. The authors do not discuss this last point. The
writing is, for the most part, clear and well-organized.
It is an interesting analysis, and I am impressed that the seasonal
splitting can be done, yielding some promising results, especially the
borehole-isotope comparison. Unfortunately, the analysis raises more
questions than it answers, and has insufficient detail and explanation of
methodology. Furthermore, the referencing and discussions are quite
limited, and as such the manuscript does not seem appropriate for a review
journal like QSR. I think the paper requires major revision before being
re-submitted, perhaps to a more specialized journal. The following major
issues should be addressed, followed by a number a minor issues.
One) The limitations and assumptions of diffusion modeling. What
parameters drive the diffusion model? How were these estimated? What is
the sensitivity of the results to different choices of parameters?
Two) On what physical basis is the 50/50 split between winter and summer
What about the seasonality of precipitation? It is different in SW
Greenland vs central and E Greenland? See Bromwich et al (1998, JGR 103,
Three) Misleading interpretation of Figures 2 and 3.
The authors have optimized the correlations of isotopes with a small set
of temperature records. I think it is always dangerous to explain a
variable like del 18-O in terms of a two-parameter model (SW Greenland and
Stykkisholmur), without any regard to the physical processes driving the
isotope signal. The model is bound to be over-fit (if only conceptually)
by forcing the data into this simple 2-parameter framework; the analysis
borders on "fishing" for correlation "bites."
In figure 2, there are little differences in correlations for isotope
fractions from 50-100%, whereas there are comparatively large differences
in the choice of instrumental data, especially in panel b. In panel 3a,
there is both a dependency on isotope fraction (improves as more data are
included) and a dependency on how many months included in the temperature
record (improves systematically from 2 to 12 months selected, especially
in panel a). This improvement is not logical at face value, as the
"summer" isotopes are poorly correlated with summer temperature (July-Aug
and Jun-Sep curves are at the bottom in 3a!!), and better correlated as
more winter data are included from the instrumental record. Furthermore,
winter centering works better for SW Greenland, whereas summer centering
works better for Stykkisholmur temperatures. Does this have something to
do with the seasonality of precipitation?
I would conclude first, that in most cases, including more than 50%
isotope data leads to better correlations with temperature, and it doesn't
hurt that much in the other cases (in panel 2a for example, where the max
correlation only drops from ~0.68 to ~0.65 from 50% to 100%). In this
regard, it is apparently the exclusion of winter data that hurt the
correlations more than the inclusion of summer data. Second, it seems to
me that the correlations have a stronger dependency on the selection of
instrumental data than on the selection of isotope fraction. This is the
opposite conclusion of the authors, who argue that the splitting of the
isotope records fundamentally alters the interpretation of the records. I
don't think our interpretations are altered that much, as we have known
about NAO signals in Greenland isotopes for a long time (going back at
least to White et al, 1997, JGR, 102 C12, 26425-26439), before any
seasonal splitting was done. Furthermore, we cannot reach a
conclusion about the merit of winter-centering vs summer-centering the
year, as it depends on which instrumental record is used.
Four) It is not explained how field correlations are derived from the 14
point observations in Figures 7,8,9,10,13,14,15, and 16. How are these
maps derived from 14 sites? There appears to be at most, 3 levels of
correlation in each map. Why not show the correlation and regression
coefficients for each ice core record?
Fifth) The statistical significance of correlations is not assessed, and
the authors use inconsistent criteria for discussing significance.
Six) Are the winter and summer data really independent? Why do the PC
patterns in Figures 10 and 16 look so similar? What is the correlation
between PC1-summer and PC1-winter? It should be near zero, but it doesn't
look like that is the case.
Seven) The coherency among records is only partly assessed. It would be
helpful to show the correlations among the 14 records. The differences in
level of variance explained in summer vs winter PCs, and the correlations
in tables 3 and 4, aren't different enough to convince me that summer
records are less coherent than winter records. If summer is less noisy,
shouldn't summer be more coherent?
Eight) Incomplete referencing and discussion, especially since this is
supposed to be a review article. Vinther and colleagues are not the first
to evaluate the NAO and temperature signals in Greenland ice cores. I am
surprised at the omission of White et al 1997, the more recent work of
Schneider and Noone (2007; JGR, 112, D18105, doi:10.1029/2007JD008652),
and others. There is no discussion of any physics, or of any modeling
studies (e.g. Werner and Heimann, 2002, JGR 107 D1, 10.1029/2001JD00253)
that might support (or not) the results.
Introduction, pg2: It's claimed that the NAO is the dominant mode of the
NH. But the North Atlantic is not the entire Northern Hemisphere! An
objective analysis of the entire NH SLP field reveals the
hemispheric-scale Northern Annular Mode/Arctic Oscillation to be the
dominant mode (e.g Quadrelli and Wallace, 2004, J Clim 17, 3728). The NAO
can be viewed as part of this larger mode, but is not by itself the
Data section 2.2: It is not explained how representative the Stykkisholmur
record is of E Greenland temps.
Diffusion section 2.1: It is not explained which parameters were inputs
into the diffusion model, and how these were chosen.
Seasons, section 3.3: The seasonality of precip is not addressed. You
can't assume that del 18 O max/mins universally equal temp max/mins across
the ice sheet, and that the max/mins occur at the same time of year
Pages 5-6: See my major comments above. The 50/50 split seems too
arbitrary, and the claim of independence of summer and winter is not
demonstrated. Are PCs1 of summer and winter independent? What is the
physical basis of these correlations?
In this and all following sections, statistical significance has been
Section 4, pg 6: How do you define SNR?
Pg 7, top paragraph: If lower variability is forced on the S Greenland
isotope timeseries, why not do the same to the instrumental data to make a
more straightforward comparison?
Pg 8: If PCs 2 and 3 are statistical noise, how can you use them to reach
a conclusion about the influence of the Central Greenland ice divide on
air masses? This assertion is also not supported by the regressions on Fig
Pg 9, section 6.1: I suspect that all of the correlations below 0.25 or so
are not significant, so there is not really a clear SW-NE reduction in
significance, just noise. The significance level also depends on the
auto-correlation of the timeseries, which is not shown. So a lower
correlation in the NE sector could be more significant than a higher
correlation in the SW sector.
Pg 10, section 6.4 and Table 4: It is not demonstrated that 34.9 % for
summer and 39.9% for winter are statistically different, if you were to
say, look at the error bars on the eigenvalues. If PC2 and PC3 are more
meaningful in summer than winter, why do summer and winter loading
patterns look virtually identical?
Pg 11-12, section 7.1: Neglect to mention that the effective resolution of
the borehole inversions decreases back in time, which may affect the
correlations, and the ability of the borehole record to resolve the
high-frequencies seen in the isotopes. Also, DYE3 borehole has larger
amplitude variation than GRIP, which is not explained. What are the
correlations among the timeseries in Figs 19 and 20, so that we can see
that winter is clearly better? For DYE3, why do the annual and summer fits
look pretty good for 1300-1970, but not prior to 1300?
Pg 12: It might not be helpful to include summer isotope data to compare
with winter and annual temps, but the exclusion of winter data to compare
with annual temps is probably the bigger issue.
Section 7.2: The discussion of Table 4 is difficult to follow. It appears
to me the C/G correlations are better for summer and annual than for
winter, the D/C correlation is similar across seasons, and the D/G
correlation only works for winter. Why not use a C/G stack or a D/C stack
that is good for all seasons?
How do these stacks compare with PC1, and are they better/worse correlated
with instrumental temperatures?
How does a D/G isotope stack compare with stacked D/G borehole records?
Section 8, pg 13: ".the summer data are much less influenced by noise and
significant atmospheric pressure patterns can be identified, even down to
the third summer del 18 O PC." At what point in the manuscript are
"significant atmospheric pressure patterns" shown for summer? In section
6.5, if one cannot interpret PCs1-2, it is not valid to interpret PC3.
TABLE1: It would be helpful to list the time span covered by the ice core
records, and an indication of which records were stacked together. This
would be more useful than the drill year & core length.
Prof. Phil Jones
Climatic Research Unit Telephone +44 (0) 1603 592090
School of Environmental Sciences Fax +44 (0) 1603 507784
University of East Anglia
Norwich Email p.jonesatXYZxyz.ac.uk