the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 09 Feb 2024
In-situ parameters, nutrients and dissolved carbon distribution in the water column and pore waters of Arctic fjords (Western Spitsbergen) during a melting season
Abstract. A nutrient distribution such as phosphate (PO₄³⁻), ammonium (NH₄⁺), nitrate (NO₃⁻), dissolved silica (Si), total dissolved nitrogen (TN), dissolved organic nitrogen (DON) together with dissolved organic carbon (DOC) and inorganic carbon (DIC), was investigated during a high melting season in 2021 in the western Spitsbergen fjords (Hornsund, Isfjorden, Kongsfjorden and Krossfjorden). Both the water column and the pore water were investigated for nutrients and dissolved carbon distribution and gradients. The water column concentrations of most measured parameters such as PO₄³⁻, NH₄⁺, NO₃⁻, Si, and DIC showed significant changes among fjords and water masses. In addition, pore water gradients of PO₄³⁻, NH₄⁺, NO₃⁻, Si, DIC and DOC revealed significant variability between fjords and are likely substantial sources of the investigated elements for the water column. The obtained dataset reflects differences in hydrography and biogeochemical ecosystem function of the western Spitsbergen fjords and may form the base for further modelling of physical oceanographic and biogeochemical processes within the investigated fjord systems. All data described in this paper are stored in the Zenodo online repository https://doi.org/10.5281/zenodo.10523197 (Szymczycha et al., 2024).
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RC1: 'Comment on essd-2024-13', Wytze Lenstra, 02 Apr 2024
I have read the manuscript “In-situ parameters, nutrients and dissolved carbon distribution in the water column and pore waters of Arctic fjords (Western Spitsbergen) during a melting season” submitted by Saghravani and co-authors. The manuscript describes a dataset submitted to Zenodo that describes both physical and chemical parameters of 4 Fjords on the Western Side of Spitsbergen (water column and porewater). Physical and chemical analysis are well applied and the data seems of good quality. I agree with the reviewer that this is a valuable data set to share and only have minor comments.
Detailed comments
L47: Is Atlantification not the same as sea ice losses?
L87: I think the authors mean a north-east to south west orientation.
L111: "Seawater pH was measured 10ml of seawater was filtered.." check text
Section 2.2.2 I see that for the porewater data there are quite some numbers missing, which might need some explanation in the methods section.
L135: check size of letters
Section 3.1. I find this section a bit hard to read because of all the abbreviations that for me are not very common. It might become better when figure 2 is plotted close to the text, however currently there is no reference to Fig. 2 in this section. Additionally, it might help to also plot the water masses as a "section plot" with potential T on the Y axis and distance on the x axis. I leave this upto the authors.
L154: Krossfjorden is marked yellow not grey
L163: (at 25°C) is mentioned after pH
L209. I find point two here a bit detailed compared to the other two. I would remove it. Also because there are more (micro)nutrients that can limit primary productivity such as iron and manganese.
Fig. 4 This figure is a bit unreadable. maybe it would hep if the authors plot three figures next to each other instead of 4.
Fig 5. This figure is a bit unreadable. maybe it would hep if the authors plot three figures next to each other instead of 4.
Fig. 6. There is an l missing after mmo and umo in the unit of the figures.
Krossfjorden 265 (marked grey). (actually marked yellow)
Citation: https://doi.org/10.5194/essd-2024-13-RC1 -
RC2: 'Comment on essd-2024-13', Astrid Hylen, 15 Apr 2024
General comments
Saghravani and co-authors present an extensive dataset of physical and chemical parameters from the water column and porewater at a multitude of sites in the western Svalbard fjord system. The data collection and chemical processing generally seem to be of high quality, and the dataset is likely to be valuable for future use. However, there are discrepancies between data presented in the manuscript and the spreadsheet provided through Zenodo, parts of the methodology need to be expanded, and figures should be improved. I would also recommend a language review to improve readability.
Specific comments
The salinity and temperature data in Figure 2 seem to consist of binned data from the CTD casts. However, only salinity and temperature values from the discrete depths where water samples were collected are included in the data spreadsheet on Zenodo. The full dataset should be added.
The Cl- concentration data are not represented properly in the manuscript; the data spreadsheet contains water column [Cl-] data, but this is not mentioned in the main text. Several of the water column [Cl-] values are 0, which I suspect is an error (should they be NA?). There is also a 0 value in one of the pore water profiles, which is not included in Figure 6. If suspected outliers have been excluded from figures, I suggest making a note in the data spreadsheet.
Statistical results are presented throughout the text, but in most cases it is not clear which test that have been used. A paragraph about statistics/calculations should be added to the methods section.
L156-170: I don’t really see the point of this comparison. This division of data mainly shows the effect of stratification. I suggest removing this piece of text; there is a clearer discussion about the distribution of parameters between fjords and water masses later in the text.
L193-201: I disagree with this approach and do not see how it is of value to the manuscript. The pore water profiles occasionally display peaks close to the sediment-water, indicating production and possible release of the compound to the water. By taking an average of 5 cm, these details are erased. As such, the method does not give valuable information about whether the sediment is a source or a sink of these dissolved compounds. There is also no basis for using 5 cm rather than another value. It would be more relevant to point out any large-scale trends in profiles between fjords, and if there are individual profiles that stand out (and possible reasons as to why – situated by a river mouth, in a local depression, etc.).
Section 2.2.2: There are many values missing from the pore water data. Is this due to a lack of pore water, or caused by analytical issues?
Technical corrections
L87-99: Invert the order of the paragraphs about Krossfjorden and Kongsfjorden, as the paragraph about Krossfjorden refers to information about Kongsfjorden.
L104: Add uncertainties for the temperature, salinity and oxygen measurements. Add oxygen sensor model.
L106-107: Move the information about the pH measurements to section 2.2.1.
L107-108: Please add the inner diameters of the core liners.
L111: Part of the sentence seems to be missing.
L114: Were the filters pre-combusted?
L118-119: Were the Rhizons inserted directly into the cores through pre-drilled holes in the core liner? Or were the cores sliced before pore water extraction?
L121-122: Add volume and concentration of the HgCl2 used.
Section 2.2.3: Most commonly the "nitrate" analysed is nitrate+nitrite. Is that the case here too, or is it only nitrite?
L130: Add information about the uncertainty of the Cl- analysis.
Section 3.1: Could you add a table with the defining characteristics for each water mass (salinity and temperature ranges, see Cottier et al. 2005)?
Figure 1: Please add extent indicators in the overview map, and annotate the panels according to the journal’s requirements (e.g., a, b, c, d). Correct the coordinates of the individual fjord maps, they do not agree with the overview map. If the bathymetry of the fjords is available, this would make a valuable addition to the maps as it would give clearer information about the areas surrounding the stations.
Figure 2: Since potential temperature is presented on the y axis, the isopycnals should be expressed as potential density anomalies rather than density anomalies (is this done?). The sign for the density anomaly is σt (potential density anomaly: σθ), not δ0. Do the colours really represent density, as the colours do not match the isopycnal lines? It would be more suitable to show e.g., depth with colour. Please ensure that the axes are the same for all panels to make comparisons easier. Annotate the panels according to the journal’s requirements.
Figure 3: I appreciate that it is difficult to represent large amounts of data in one figure, but these graphs are hard to read. The main purpose of this figure seems to be to show the differences between fjords and water masses. I suggest plotting the profiles in a grid of parameters versus fjords (for the graphs to be large enough, this might require splitting the figure into two, e.g., parameters more and less influenced by biology). This would also allow data points to be coloured by water mass, which would help with the discussion about how the origin of the water affects its chemical composition. Furthermore, I would add lines between the datapoints in each profile.
Figure 4: I suggest removing this figure, see comment on L156-170.
Figure 5: This figure is also very hard to read. Firstly, have one legend and placing it underneath all the graphs. Secondly, decrease the number of columns in the graph grid to three or even two, otherwise everything is too small to read. Thirdly, I suggest marking groups that are not significantly different with the same letters, rather than adding p values to the graph – it is currently not clear if the “significantly different” water mass is different to other water masses within the same fjord, or to the same water masses in other fjords, or both.
Figure 6: Like with figure 4, I suggest plotting the profiles in a grid of parameters versus fjords, and to add lines between the points in the individual profiles. The titles of the x axes are missing an l in ‘mol’.
Figure 7: I think this figure can be removed, see comment on L193-201.
Citation: https://doi.org/10.5194/essd-2024-13-RC2
Data sets
In-situ parameters, nutrients and dissolved carbon distribution in the water column and pore waters of Arctic Fjords (Western Spitsbergen) during a melting season B. Szymczycha et al. https://doi.org/10.5281/zenodo.10523197
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