the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Oceanographic monitoring in Hornsund fjord, Svalbard
Abstract. Several climate-driven processes take place in the Arctic fjords. These include ice-ocean interactions, changes in biodiversity and ocean circulation patterns, as well as coastal erosion phenomena. Conducting long-term oceanographic monitoring in the Arctic fjords is, therefore, essential for better understanding and predicting global environmental shifts. Here we address this issue by introducing a new hydrographic dataset from Hornsund, a fjord located in south-western part of Svalbard archipelago. Hydrographic properties have been monitored with vertical temperature, salinity and depth profiles in several lo- cations across the Hornsund fjord from 2015 to 2023. From 2016 onward dissolved oxygen and turbidity data are available for the majority of casts. The dataset contributes to the so far infrequent observations especially in spring and autumn and extends the observations typically concentrated in the central fjord to the areas adjacent to the tidewater glaciers. Because sediment discharge from glaciers and land is an inseparable part of the glacier-ocean interactions, the suspended sediment concentration in the water column as well as the daily sedimentation rate adjacent to the tidewater glaciers are monitored with regular water sampling and bottom-moored sediment traps. Here we present the planning and execution of the monitoring campaign from the collection of the data to the post-processing methods. All datasets are publicly available at the repositories referred to in the Data availability section of this manuscript.
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RC1: 'Comment on essd-2024-153', Anonymous Referee #1, 14 Jun 2024
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General comments
The manuscript describes the establishment of oceanographic monitoring in Hornsund fjord in Svalbard covering nine years. The description includes the initial large monitoring effort, which is the basis for recommending a revised smaller monitoring program with fewer stations. The monitoring program adds to both the seasonal and cross fjord observations of the fjord. Thus, also considering the large impact from climate change on the Arctic, I find that this monitoring is unique for Hornsund and certainly useful for future (re)use in understanding impact from climate change in the Arctic.
Generally, the paper is well written, but with a few minor issues outlined below. The dataset is well described in the manuscript, but also here a few clarifications are needed, see comments below. For continued monitoring, I suggest that recurring calibration procedures are established, especially for salinity. The authors refer to the use of TEOS-10 and here I am a bit puzzled that the authors do not mention Absolute Salinity and Conservative Temperature. To conclude, I suggest minor revision of the manuscript.
Regarding the data files, there are a few issues ranging from minor to serious, see specific comments on data below. I believe that these issues are easily solved, but new revised data files must be uploaded before the manuscript is accepted.
Specific comments
Please follow TEOS-10 guidelines: “published values of salinity should be specifically identified as being either Practical Salinity with the symbol SP or Absolute Salinity with the symbol SA” (citation from https://www.teos-10.org/). This should be done throughout the manuscript as well as in the data files.
Line 42: Here, you mention Winter Cooled Water for the first time. Please describe this water mass briefly for the reader not familiar with the area.
Line 136-139: In line 122 you say “over 50” stations, but here they are about 100. It is not clear how many belong to the monitoring program and how many to “various research projects”. Please clarify.
Line 182-183: I find that you are very specific here, mentioning subjective commitment of persons. I would think that this falls within “availability of staff”. Please delete or rewrite.
Line 235: I find it weird that low salinity values mostly occur, when there is no freshwater flux to the fjord. Please clarify.
Line 243: On what basis did you choose these lower limits? Please clarify.
Technical corrections
Check the use of comma’s. E.g. line 41 “In recent years, warming …”; line 122 “Initially, the hydrographic …” and elsewhere.
Line 37: “… relatively little studied.” Check language and consider rephrasing.
Line 47: “… to occupy larger extent…” Check language and consider rephrasing.
Line 70 and 74: There are more than one survey, right? Thus, should be “Hydrographic surveys…. have” and “The surveys contribute to…”
Line 123 and 127: Table 1 only includes 11 stations. I suggest to move the reference to Table 1 from line 123 to line 127.
Line 194: replace “early years” with “first years”.
Line 279: delete “one” in “the other one”
Line 312: Insert space in mgl-1.
Line 436: Delete one of the “financed by”.
Figure 1, legend: You describe the yellow star in the text for 1c, but the star is much more visible in 1b. Please move this part to text for 1b.
Table 1. second line: “between” instead of “netween”. Comma after “In addition, “
Figure 2: Here, you are plotting data from stations BuBW_01 and BuBW_04, but I cannot find station BuBW_04 in Figure 1. Please add it to the map.
Figure 4: The plus-signs in (b) are not very visible and it is hard to see their colours. Please change to a filled symbol.
There is no reference to Appendix A. Please indicate the offset issue in the text and add reference to the appendix.
Specific comments on data
Hornsund-fjord_CTD: When plotting all oxygen data with depth, one profile stands out with increasing oxygen with depth. This is visible in the depth range ~75m to ~170m, where the profile ends with two lower values. Please check the data.
Hornsund-fjord_CTD_suppl: The variable “Depth Water” seems to be identical to “Temp”. This is a serious error.
The Dissolved oxygen concentration is missing.
Hornsund-fjord_SR: A minor issue: I was not able to import the data to Matlab using the import tool, as only the first two columns were visible. After deleting the header info, the problem was solved. Please check, if there is an issue in the shift from header to data. The other files were okay.
Citation: https://doi.org/10.5194/essd-2024-153-RC1 -
RC2: 'Comment on essd-2024-153', Anonymous Referee #2, 28 Jun 2024
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Review of „Oceanographic monitoring in Hornsund fjord, Svalbard” by Korhonen et al.
The ESSD paper by Korhonen et al. describes a monitoring activity in Hornsund Fjord. The focus is on oceanographic measurements at a few selected sites in the fjord, complemented with some sediment studies. The monitoring was initiated almost one decade ago and is composed of ~monthly occupations via small boat from the Polish Polar station. The paper is generally well-written and clear, but some questions remain that are specific to the monitoring activities and the expected scientific goals, which I would encourage the authors to address before publication of the paper.
The way I read the manuscript, the main focus of the activities is to understand the influence of the warm Atlantic water on the fjord, mainly in order to monitor the future of the numerous glaciers in the region. The main focus is therefore on the oceanographic conditions in the fjord, but considering the oceanography focus, I am slightly surprised by the choices of instruments that are being used. The main CTDs used are made by SAIV and Valeport, and based on the specifications (low sampling frequency, coarse conductivity accuracy) do not seem ideal for thorough oceanographic monitoring. Why does the program not use “standard” Seabird (for instance SBE16) or RBR instruments, which are equally easy to handle and arguably may provide better data quality? Is this a funding decision only?
The introduction could discuss the larger-scale importance of Hornsund fjord. Is the fjord only of regional importance or would for instance enhanced glacial melt have any impact on the exchange with the water masses and circulation outside of the fjord? Greenland melt of course is on much larger magnitude with much higher impact on climate, but maybe it would be good to put the Svalbard glaciers into perspective. The introduction (line 33-35) talks about ecosystem, nutrients, chemical composition. Can you provide more background on the ecosystem? Is the fjord productive, is it important for fish, birds, mammals? If part of the monitoring interest is on the ecosystem, why does the list of sampling parameters not include anything besides oxygen and turbidity? To me it is not clear, why the second focus of the program besides oceanography is on sediment traps/turbidity (line 73-74). Is this only to catch runoff from land and glaciers or also to capture biological productivity within the water column?
Also, in the introduction, it is stated that tides, winds, coastal trapped waves are important transport drivers. These processes occur on shorter temporal scales than is covered by ~monthly CTD casts. Considering, that the program includes mooring sediment traps already, would moored oceanographic instruments not be useful additions to cover the higher temporal scales? I am probably overshooting the goals of the monitoring here, so I apologise. However, along the same lines, how was the spatial station coverage determined? Lines 123-127 state that the data collected earlier indicated that it was not necessary to sample so densely spaced. This sounds pretty vague, is there a more quantitative way to underline the choice, for instance with Rossby Radius arguments?
Some more specific comments below:
172-173: The BUBW01 example used to state that the horizontal differences are small seems to be from a really small side arm. Is this a representative example?
182 “…subjective commitment of the person…” sounds quite unprofessional. Is the irregular sampling coverage going to affect upcoming analyses?
205 remind the reader of the water depths at the 2 sediment trap sites here
229 it probably would be more up to date to present the data as conservative temperature and absolute salinity
248-252 about running the sensor into the bottom: perhaps think of using a 5m (or so) lead line with a weight below the CTD. This way the user can feel once the weight is at the seafloor and reduce the lowering speed to avoid running the CTD into the ground, which apparently affects the data quality
253 “the data are compressed to 1 dbar”. What does that mean exactly? Sampling with 0.5 Hz and a lowering speed of 0.4m/s (but often faster) results in 1 or less sample per meter. This seems unnecessarily coarse and might be one argument to use other CTDs.
Fig 1: PPS and the yellow star is not easy to find
Fig 6, 285-294: I find that the characteristics described in the text are not entirely easy to see in the figures.
299-300: also really difficult to see. Might be the choice of colors or maybe it’s just my eyes…
Fig. 7: why is Hansbukta chosen? Are tides important there? In such a shallow bay with tides and other mixing mechanisms it may not be surprising to have a homogeny water body. The vertical lines are kind of difficult to see, at least in my version.
Fig6/7: is there really no sea ice at all in Hornsund during winter? The near-freezing temperatures do seem to suggest complete overturning and ice formation during winter and stratification and warming during summer.
345 If knowing the exact depth is important, one could attach a small pressure sensor to the device
399 Seabird not Seebird
Citation: https://doi.org/10.5194/essd-2024-153-RC2
Data sets
Hydrographic observations from Hornsund fjord, Svalbard, 2015-2023 M. Moskalik et al. https://www.pangaea.de/tok/ff2d7cae4caf74f1d0ced10abdb74b86ea553883
Hydrographic observations from Hornsund fjord, Svalbard, 2015-2023 from supplementary stations M. Moskalik et al. https://www.pangaea.de/tok/d435cda9d594c9650df01f222977125a500b352f
Sedimentation rate from Hornsund fjord, Svalbard, 2015-2023 M. Moskalik et al. https://www.pangaea.de/tok/1c4eb8cbfa59320a1db28df347e25c49bd94a649
Suspended sediment concentration from Hornsund fjord, Svalbard, 2015-2023 M. Moskalik et al. https://www.pangaea.de/tok/418c50529e1283e442bdf142db901a92cc865eb3
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