the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Ice-core data used for the construction of the Greenland Ice-Core Chronology 2005 and 2021 (GICC05 and GICC21)
Dorthe Dahl-Jensen
Hubertus Fischer
Katrin Fuhrer
Steffen Bo Hansen
Margareta Hansson
Christine Schøtt Hvidberg
Ulf Jonsell
Sepp Kipfstuhl
Urs Ruth
Jakob Schwander
Marie-Louise Siggaard-Andersen
Giulia Sinnl
Jørgen Peder Steffensen
Anders M. Svensson
Bo Vinther
Abstract. We here describe, document, and make available a wide range of data sets used for annual layer identification in ice cores from DYE-3, GRIP, NGRIP, NEEM, and EGRIP. The data stem from detailed measurements performed both on the main deep cores and shallow cores over more than forty years using many different setups developed by research groups in several countries, and comprise both discrete measurements from cut ice samples and continuous-flow analysis data.
The data series were used for the construction of the Greenland Ice-Core Chronology 2005 (GICC05) and/or the revised GICC21. Now that the underlying data are made available, we also release the individual annual layer positions of the GICC05 time scale which are based on these data sets.
We hope that the release of the data sets will stimulate further studies of the past climate taking advantage of these highly resolved data series covering a large part of the interior of the Greenland ice sheet.
Sune Olander Rasmussen et al.
Status: open (until 21 Apr 2023)
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RC1: 'Comment on essd-2022-361', Eric Wolff, 06 Mar 2023
reply
This contribution provides the datasets that underlie the production of the GICC05 and subsequently the GICC21 age scales. These have been described in many papers over a few years and some of the datasets listed here have been published in Pangaea or elsewhere already, with a significant number being provided publicly for the first time here. It is hugely welcome to see these datasets made available: they provide evidence for the decisions made in making the age scales, they provide the options for other groups to assess the quality of those scales, and they document a history going back 4 decades that should not be lost. I know some members of the ice core community have been frustrated that such data were not available, so it’s great to see the effort made to document and provide the data. Thank you! These are important data and must certainly be published.
The text itself is a nice description that is not very controversial. I have suggested few minor additions or edits. I also took a brief look at the new datasets provided. I found one significant issue that will need to be addressed. I also have some questions about what is not here: I doubt this will require changes to the data, but maybe small additions to the text just to set these data in context.
Major comment: Dye 3 ECM. Somehow the number of significant figures in both depth and acidity have been reduced to the point where the data are unuseable (depths given only as metres so that many data have the same depth). Please revise this dataset.
Additional comment on data: The file providing the annual layer depths is done for GICC05, but for GICC21 we are simply referred to the supplement to Sinnl et al (2022). This is OK but it leaves the reader who has found the GICC05 layers unaware that for the last 3.8 kyr they have been superceded. I realise this may be hard to do but wouldn’t it be valuable to add a column giving the corresponding depths (even if only for 1 site) for GICC21 until 3.8 ka b2k, so that the reader knows they are better to use? This is just a question of copying some columns from that supplement and would have the added value of making the GICC21 data available in a more regular database.
Line 25,26: it would be useful to include in the abstract that GICC05 is to 60 ka and GICC21 so far to 3.8 ka.
Line 166 “discretely” should be “discrete”.
Line 195. I think ueq or uequiv but no “.” Would be normal. I do wonder why ECM data are supplied as H+ (which the paper admits is uncalibrated) rather than as what was measured, ie current. Possibly this is simply a question of what level of product has been stored but maybe it is worth a comment?
Line 204, 268, 355/7 etc “ammonium” not “Ammonium” unless it starts a sentence. Same for other ions, please check this or the copy editors might look out for it.
Section 3.2. I guess they were not used in the layer counting but it might be worth mentioning for context that GRIP DEP data are available at 2 cm resolution at https://www.ncei.noaa.gov/access/paleo-search/study/17845
Line 230. Come on, we need to see the elastic band! (no need to respond to this).
Line 268. I appreciate that the abstract to the dataset warns that CPH ammonium and STO lithium may be unreliable, but by the time one has downloaded the tab file as an Excel, that warning is lost. I feel it should be clearly mentioned in the metadata within the file; I also question the value of publishing data you believe to be wrong.
Line 292. You mention that Fuhrer et al analysed the ammonium data. Again for context would it be worth mentioning that Fuhrer et al (1999) analysed the Ca data? (Fuhrer, K., Wolff, E. W., and Johnsen, S. J.: Timescales for dust variability in the Greenland Ice Core Project (GRIP) ice core in the last 100,000 years, J. Geophys. Res., 104, 31043-31052, 1999.). Maybe you feel that because they didn’t use the high resolution there is no relevance, and I would understand that.
Line 310. McConnell spelling.
Citation: https://doi.org/10.5194/essd-2022-361-RC1 -
AC1: 'Reply on RC1', Sune O. Rasmussen, 06 Mar 2023
reply
Thank you, Eric, for your comments. I will take these into account when revising the manuscript. A few remarks to your comments are found below.
Best regards and thank you for your efforts editing the GICC papers,
Sune---
Major comment: Dye 3 ECM. Somehow the number of significant figures in both depth and acidity have been reduced to the point where the data are unuseable (depths given only as metres so that many data have the same depth). Please revise this dataset.
Thanks for spotting this. I have contacted PANGAEA and will sort this out as soon as I get a reply. It is likely a file conversion error.
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Additional comment on data: The file providing the annual layer depths is done for GICC05, but for GICC21 we are simply referred to the supplement to Sinnl et al (2022). This is OK but it leaves the reader who has found the GICC05 layers unaware that for the last 3.8 kyr they have been superceded. I realise this may be hard to do but wouldn’t it be valuable to add a column giving the corresponding depths (even if only for 1 site) for GICC21 until 3.8 ka b2k, so that the reader knows they are better to use? This is just a question of copying some columns from that supplement and would have the added value of making the GICC21 data available in a more regular database.
GICC21 applies to more cores than GICC05, and I fear that the data file will be very unhandy to use if we merge GICC05 with GICC21 layer positions plus the other supporting material that comes with GICC21. I suggest that we make a clear reference in the metadata of the GICC05 annual layer to the location of the corresponding GICC21 spreadsheet which has both the annual layer positions and a GICC05-GICC21 transfer table. Then all users will know that a newer time scale is available.
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Line 195. … I do wonder why ECM data are supplied as H+ (which the paper admits is uncalibrated) rather than as what was measured, ie current. Possibly this is simply a question of what level of product has been stored but maybe it is worth a comment?
Yes, this is indeed the reason: The data files available to us (and used for GICC05) were the tentatively calibrated H+ records, not the original measurments. I will add a comment.
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Line 268. I appreciate that the abstract to the dataset warns that CPH ammonium and STO lithium may be unreliable, but by the time one has downloaded the tab file as an Excel, that warning is lost. I feel it should be clearly mentioned in the metadata within the file; I also question the value of publishing data you believe to be wrong.
We do not think that the data are wrong, but as described in section 3.4, they may be subject to larger bias than for other species due to the analytical setup. The warning also appears on the PANGAEA data page and will this accompany the data in the downloaded Excel file.
Citation: https://doi.org/10.5194/essd-2022-361-AC1 -
RC2: 'Reply on AC1', Eric Wolff, 07 Mar 2023
reply
That all sounds fine Sune (and I accept your arguments about the annual layers sheet and other issues). Thank you.
Citation: https://doi.org/10.5194/essd-2022-361-RC2
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RC2: 'Reply on AC1', Eric Wolff, 07 Mar 2023
reply
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AC1: 'Reply on RC1', Sune O. Rasmussen, 06 Mar 2023
reply
Sune Olander Rasmussen et al.
Data sets
Electrical conductivity measurements (ECM) from the DYE-3 ice core, Greenland Sune Olander Rasmussen, Steffen Bo Hansen, Dorthe Dahl-Jensen, Jakob Schwander, Jørgen Peder Steffensen, and Bo Møllesøe Vinther https://www.pangaea.de/tok/5e1cd34a4b5e89a1c44bacb72c13b4f37d401b47
Electrical conductivity measurements (ECM) from the GRIP ice core, central Greenland Sune Olander Rasmussen, Steffen Bo Hansen, Christine Schøtt Hvidberg, Dorthe Dahl-Jensen, Steffensen, and Jørgen Peder Steffensen https://www.pangaea.de/tok/b0b8821b04a2edc52b1702bd67b00e2208ac025b
DYE-3 ice core detailed water-isotope data Sune Olander Rasmussen and Bo Møllesøe Vinther https://www.pangaea.de/tok/8c79195d8f4a9eae2d6a4ab51d791054510adee9
DYE-3 4B ice core detailed water isotope data Sune Olander Rasmussen and Bo Møllesøe Vinther https://www.pangaea.de/tok/5944c0168ecaeb78eb676c5aa3c340235a240136
DYE-3 18C ice core detailed water isotope data Sune Olander Rasmussen and Bo Møllesøe Vinther https://www.pangaea.de/tok/e6c800c6349d47c296a3dd65b19c13c9844af500
GRIP ice core detailed water isotope (δ18O) data Sune Olander Rasmussen and Bo Møllesøe Vinther https://www.pangaea.de/tok/a3e8f9e8be16d3daceff023cfcee9c792650130c
NorthGRIP ice-core record of major ions measured using ion chromatography covering the last two millennia and additional short Holocene sections Marie-Louise Siggaard-Andersen, Margareta E. Hansson, Jørgen Peder Steffensen, Ulf Jonsell, and Sune Olander Rasmussen https://www.pangaea.de/tok/8f591eb20fb0c9f7b0208ef3e84c86f98cfcd748
High-resolution impurity data from the GRIP ice core Hubertus Fischer, Sune Olander Rasmussen, and Katrin Fuhrer https://www.pangaea.de/tok/415ba47735cfe879651c292b2268a873c33549b1
High-resolution dust concentrations from the NGRIP2 ice core Sune Olander Rasmussen and Urs Ruth https://www.pangaea.de/tok/a0c2f9b2da6ea3231bc6bc585ba61001a81ca2ad
Greenland Ice-Core Chronology 2005 (GICC05) annual layer depths for various Greenland ice cores Sune Olander Rasmussen, Anders M. Svensson, and Bo Møllesøe Vinther https://www.pangaea.de/tok/023c71d6caa354bd56a7e51c48aca102f823d7c1
Sune Olander Rasmussen et al.
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