the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Regional variations in mineralogy of dust in ice cores obtained from northeastern and northwestern Greenland over the past 100 years
Naoko Nagatsuka
Kumiko Goto-Azuma
Koji Fujita
Yuki Komuro
Motohiro Hirabayashi
Jun Ogata
Kaori Fukuda
Yoshimi Ogawa-Tsukagawa
Kyotaro Kitamura
Ayaka Yonekura
Fumio Nakazawa
Yukihiko Onuma
Naoyuki Kurita
Sune Olander Rasmussen
Giulia Sinnl
Trevor James Popp
Dorthe Dahl-Jensen
Abstract. To investigate regional and temporal variations in the sources and atmospheric transport processes for mineral dust deposited on the Greenland Ice Sheet, we analysed the morphology and mineral composition of dust in an ice core from northeastern Greenland (East Greenland Ice-Core Project, EGRIP), representing the period from 1910 to 2013, using scanning electron microscopy and energy-dispersive X-ray spectroscopy, and compared the results with those previously obtained for an ice core from northwestern Greenland (SIGMA-D). The composition of the SIGMA-D ice-core dust, comprising mostly silicate minerals, varied on a multi-decadal timescale due to an increased contribution of minerals originating from local ice-free areas during recent warming periods. In contrast, for the EGRIP ice-core dust, also consisting mostly of silicate minerals, there was relatively low compositional variation among the samples, suggesting that the mineral sources have not changed dramatically over the past 100 years. The subtle variation in the EGRIP ice-core mineral composition is likely due to a minor contribution of local dust. The type of silicate minerals differed significantly between the two ice cores; micas and chlorite, which form in cold dry regions, were abundant in the EGRIP ice core, whereas kaolinite, which forms in warm humid regions, was abundant in the SIGMA-D ice core. This indicates that the EGRIP ice-core dust likely originated from different geological sources than those for the SIGMA-D dust. A back-trajectory analysis indicated that the ice-core dust was transported from Northern Eurasia and North America to the EGRIP site, and that the contribution from each source was likely smaller and larger, respectively, than those for the SIGMA-D ice core. Furthermore, the higher illite content in the EGRIP ice core suggests dust transportation from Asian deserts. Although the back-trajectory analysis suggests that most of the air mass that arrived at the EGRIP site came from the Greenland coast, the mineral grain size and composition results showed that the local dust contribution was likely small.
- Preprint
(3606 KB) - Metadata XML
- BibTeX
- EndNote
Naoko Nagatsuka et al.
Status: open (until 27 Oct 2023)
-
RC1: 'Comment on egusphere-2023-1666', Anonymous Referee #1, 14 Sep 2023
reply
In this manuscript Nagatsuka and colleagues analyze the mineral content of dust particles in a shallow ice core from central Greenland, and estimate the potential source contribution through backtrack trajectory modeling. They compare their results with a similar core drilled further west and published previously.
The main contribution of this manuscript are the detailed mineralogical analyses of this new shallow core since 1910. Although the results are new, they are rather incremental and it is not clear how these new data are improving our knowledge of Central Greenland dust advection or source contribution. That dust in central Greenland mostly originates from distant sources (mostly in East Asia) and not local ones was already known from other cores. This study mostly repeats this result at higher resolution. In addition, the authors imply links between their results with recent warming in Greenland, which is poorly supported since any kind of analyses including Atlantic and Pacific oscillations are missing. Finally, the discussion of volcanic particles is mostly a literature review without any contribution from this manuscript.
For these reasons I suggest to reject this manuscript as it does not include sufficient scientific advances for Climate of the Past. Instead, I suggest to publish these results in a more specialized journal.
Major Comments:
The authors mostly compare their results with an ice core from northeast Greenland (sigma-d) for which similar data are available. However, the comparison to central Greenland, east Greenland (Renland) and southeast Greenland (Dye-3) should be included in the discussion. In particular, the comparison with NGRIP should be made, as the claim that EGRIP represents Eastern Greenland and NGRIP central Greenland is a bit shaky, considering both sites are at similar altitudes and quite close to each other.
The authors group Europe and NorthEast Asia, as well as Africa and SouthEast Asia into single potential source areas in their analysis. Considering the long debate about Asian, European and African dust sources for Greenland, these should probably be split into four, unless the authors can justify their choice.
The authors talk about trends in the data in various sections of the manuscript, in particular comparing the last 20 years with the mid-section of the core. In particular, the authors imply that the recent warming has been responsible for various changes in dust mineralogy and concentrations. But looking at the complete record, these look more like multidecadal oscillations to me and should not be described as trends. Although recent warming in Greenland may have been responsible for some of the observed changes, such a hypothesis has to be put in context with the complete oscillations shown in the records. The authors briefly mention NAO at some point, but the link between their record and various Atlantic and Pacific oscillations should be discussed in much more details.
Minor Comments:
Line 18: Abstract could benefit from a more general introductory phrase at the beginning.
Line 33-34: Since Greenland is an island, all air masses must come from a coast. Be more precise.
Line 38: 100,000 years seems a bit short for the geological timescale, although I am not a geologist and may be wrong. Maybe Milankovitch timescale?
Line 42: “ice-core dust shows…”. Also this is only shown for Central Greenland, not the whole of Greenland.
Line 44-45: This is not at all the message of Svensson et al., 2000. Generally, I very much doubt that the seasonal variability in dust advection to Greenland is due to climate change…
Line 46: Not “predict”. “estimate” maybe.
Line 47: “partly responsible”. Grain size and partial melt is very important as well for albedo.
Line 53-58: The message of these phrases is unclear. Are you suggesting to collect dust from outcropped ice in the ablation zone to measure old dust? Or just dust in fresh snow on the surface? Then why talk about the movement of ice and dust through the ice sheet?
Line 60: Ujvari et al. used Hf not Pb.
Line 75: Can you give some references to support that hypothesis?
Line 117: Is the Beckman CC located in a normal laboratory or a clean room or a laminar flow bench? What kind of aperture tube was used?
Line 145, Table 1: Why is South America included as a possible source for Type A particles? I’m not saying it’s wrong (although I do doubt it), but I wonder why it was included in the list.
Lines 171-174: Snow cover fractions vary substantially from one model to another. Please provide and uncertainty estimate due to the choice of the model.
Lines 209-216: What do the numerical ranges indicate? 1-sigma range? If so how were the mean and standard deviations calculated?
Citation: https://doi.org/10.5194/egusphere-2023-1666-RC1 -
AC1: 'Reply on RC1', Naoko Nagatsuka, 23 Sep 2023
reply
We appreciate the anonymous referee #1 for taking the time to review our manuscript and giving helpful suggestions and comments.
Please find the responses to the referee comments in the pdf file attached.
-
AC1: 'Reply on RC1', Naoko Nagatsuka, 23 Sep 2023
reply
Naoko Nagatsuka et al.
Naoko Nagatsuka et al.
Viewed
HTML | XML | Total | BibTeX | EndNote | |
---|---|---|---|---|---|
227 | 73 | 12 | 312 | 5 | 6 |
- HTML: 227
- PDF: 73
- XML: 12
- Total: 312
- BibTeX: 5
- EndNote: 6
Viewed (geographical distribution)
Country | # | Views | % |
---|
Total: | 0 |
HTML: | 0 |
PDF: | 0 |
XML: | 0 |
- 1