Cryosphere and ocean variability in Kane Basin since the 18th century: insights from two marine multi-proxy records

Kvorning, Anna Bang; Sicre, Marie-Alexandrine; Luetzenburg, Gregor; Schmidt, Sabine; Andersen, Thorbjørn Joest; Klein, Vincent; Georgiadis, Eleanor; Limoges, Audrey; Giraudeau, Jacques; Bjørk, Anders Anker; Larsen, Nicolaj Krog; Ribeiro, Sofia

doi:10.5194/egusphere-2025-2641

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https://doi.org/10.5194/egusphere-2025-2641

Preprints

08 Jul 2025

| 08 Jul 2025

Cryosphere and ocean variability in Kane Basin since the 18th century: insights from two marine multi-proxy records

Anna Bang Kvorning, Marie-Alexandrine Sicre, Gregor Luetzenburg, Sabine Schmidt, Thorbjørn Joest Andersen, Vincent Klein, Eleanor Georgiadis, Audrey Limoges, Jacques Giraudeau, Anders Anker Bjørk, Nicolaj Krog Larsen, and Sofia Ribeiro

Abstract. Nares Strait, a marine gateway connecting the Arctic Ocean with northern Baffin Bay, is characterised by the formation of a seasonal ice bridge between Canada and Greenland, that prevents the southward export of multiyear sea ice. Recent observations indicate increasing instability in sea-ice formation, particularly evident in Kane Basin, which either freezes over or remains open during winter and spring depending on ice-bridge dynamics. The Kane Basin is influenced by contrasting ocean currents in its eastern and western sides, as well as by the Humboldt Glacier, Greenland’s widest marine-terminating glacier. Kane Basin is a critical region due to its pronounced sensitivity to cryospheric and oceanic changes. However, its long-term environmental history, particularly in the eastern sector, remains poorly constrained prior to the satellite era. Here, we present two multi-proxy sediment core records from opposite sides of Kane Basin, spanning from the 18th century to the present, that we compare with Humboldt Glacier frontal positions since 1965 CE. Clear spatial differences are evident across the basin in terms of sediment delivery, primary productivity, and the source of organic matter. Both records also reveal temporal changes, transitioning from cold sea-surface conditions with extensive sea ice during the Little Ice Age (peaking around 1900 CE), towards more open and stratified waters, accompanied by increased primary production from approximately 1950 CE to the present.

Received: 04 Jun 2025 – Discussion started: 08 Jul 2025

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RC1:
'Comment on egusphere-2025-2641', Anonymous Referee #1, 29 Jul 2025
In this study, the authors generated two paleoenvironmental records from the western and eastern edges of Kane Basin to understand the sedimentological, environmental, and oceanographic changes in the Nares Strait, a region where multiyear sea ice can export from the Arctic to the North Atlantic, over the recent past (~1750 - present). The authors found that the depositional environment is different between the western and eastern side of Kane Basin, and further found a decrease in sea ice since the 1950s based on biomarker evidence, as well as a change in glacial runoff and increased stratification, both evident from observations of the IRD, increased primary productivity and a change in assemblage composition in the sedimentary records. Based on these results, the authors concluded that the sea ice cover, ocean stratification and increased freshwater input in this region are already undergoing changes.

I think it is useful to have these new records to better understand how high-latitude regions with significant ocean-ice sheet-sea ice interactions is changing over time, especially since these regions are undergoing rapid changes due to anthropogenic climate change. Below are my comments/suggestions that I hope would improve this manuscript.

Major comments:
The majority of the introduction/motivation was pretty well laid out in the paper, however, I think including and clarifying the following components would help make the introduction/motivation of this study more complete:
Perhaps it is obvious to most paleoceanographers/paleoclimatologists, but I think there’s a missing link between the importance of studying this region, which is elegantly stated in L34-78, and why we need to specifically generate these proxy records to study this region, which is not clear here.

Perhaps this is just me, while I don’t doubt the importance, I find the motivation of reconstructing changes on both sides of the basin a bit unclear — do we analyze both sites because we expect them to change differently owing to the distinct oceanographic conditions? Or we want to see whether they are changing synchronously?

With regards to studying western and eastern sides of the basin, while I agree that it is important to study both sides of Kane basin, it is a bit unclear to me what the spatial difference between the sites imply. To me, the introduction made it sound like the oceanographic conditions are different between the two sites, so naturally I expect the biogeochemical and sedimentological properties to be different as well. So, the differences found between the two records are unsurprising, at least to me. I think it would be great if the authors could clarify the implications and novelty of the results regarding the spatial difference, so that it would be clear why this is important and interesting.

How the age model was built and the uncertainties associated with it was estimated are both a bit unclear to me. More detail comments can be found below in the minor comments.

I personally don’t find the evidence in section 4.2 particularly strong. Here, the authors argued that the IRD layers coincided with the decrease in front position and increase in discharge. However, looking at figure 6, there are two issues: a) the retreat line doesn’t really correspond to the ice discharge line — this is probably still fine because both datasets have their own uncertainties and that ice discharge and glacier retreat are not exactly the same thing, but b) I would also argue that the discharge in the 1970s-1990s don’t really match with the IRD layer, where one can place the discharge either in the 1970, or another peak around 1985. While I don’t doubt there’s a connection between the IRD layers and the ice discharge, I just find that the evidence presented here is a bit weak.

While I believe the authors have kind of done that in section 4.4, I feel like there needs to be a stronger connection between the results and interpretations presented in this study and what we are observing in the satellite era in the conclusion section. Specifically, I think it is important to highlight the new knowledge we learned about variability in the Kane Basin that was previously not attainable using solely the satellite record and also putting the recent change into a longer-term context.

Minor comments:
Section 2.1 (L92-96): I have a hard time wrapping my head around on how the age-depth model was calculated and how the extrapolations as done. It would be good if the authors could clarify what they meant by (1) deriving the MAR from the profile of Pbxs against cumulative mass, (2) using MAR to establish the chronology, and (3) how they extrapolated the chronology further back in time (i.e., what kind of extrapolation was done).

Section 2.2: What are the measurement uncertainties associated with TOC and TN? The reason I’m asking is because the TOC and TN content in both cores seem pretty low, which makes me slightly worried about interpreting TOC, TN and C:N values.

In section 2.5, it would be great to briefly explain how the balance of flexibility and overfitting was achieved, was it through applying a specific criterion or through analyzing specific properties of the model (e.g., residuals)?

Figure 6: It would be great to explain how the age uncertainty was determined in the figure. Based on my read, there’s no quantification of age uncertainties, aside from the Cs Pb measurements that are shown in Figure A1.

Figure 7: How was the PIpP25 index divided into extended ice cover, marginal ice zone and variable/less ice cover?

Figure 7: I believe the PIpP25 shown here is not the same term used throughout the text: PIP and PIP25 were used instead.

Figure 7: On a related note, I don’t think the PDIP25 and PBIP25 indices were discussed/introduced in the text.

Figure 7: I don’t think the temperature is the GRIP ice core record per se, but is a borehole temperature at the GRIP ice core site instead.

Figure A1: It would be good to explain what the range of uncertainties the ‘whiskers’ of each dot represent.
Citation: https://doi.org/10.5194/egusphere-2025-2641-RC1
RC2: 'Comment on egusphere-2025-2641', David Harning, 21 Nov 2025

Kvorning and co-authors present multi-proxy reconstructions from two sediment cores in Kane Basin, northwest Greenland. Despite that the records come from environmentally different locations, the results generally suggest that trends in sea ice and productivity are similar (although with some spatial differences) between the two over the last several centuries. I found the study design and record selection to be interesting, and think the data analyses generally support the conclusions (I appreciated the inclusion the GAMs!). In my following comments, you will see that I mostly have questions about method details and data presentation. I generally had similar thoughts to the other reviewer’s major comments, particularly related to bigger picture linkages, so I will try not to repeat those here. Following revisions, this manuscript would be a nice fit for Climate of the Past.

Specific comments:
L36: Need reference.
L42: Instead of retreated, “separated” may be more precise
L44: Instead of oceanographic conditions, I would suggest “environmental” conditions as you don’t really discuss the oceanographic differences in the east per se, more the glacier. If there are oceanographic differences, please clarify. It may be helpful to have a dedicated and more detailed (but brief) section on local oceanography following the introduction.
L47: Start sentence with “on the eastern side” to better follow prior sentence and highlight contrast.
L58: I’s unfortunately not yet published, but the preprint by Lenetsky et al. (2025) shows that you can still get a polynya without ice bridges. This goes against the paradigm, and although I’m not suggesting the authors need to include this ref since not published, I figured it would be interesting if they weren’t already aware.
L71: Do these studies have the resolution and age control to track polynya instability for the last 4 decades? If so, I had not realized!
Figure 1: First, I suggest changing the font color in panel A to white or something light for place name labels are currently hard to read. Second, did Ribeiro et al. (2021) map the NOW’s modern extent - is there a better ref here? Third, the gray dashed line for the Last Ice Area runs through Greenland and down into Baffin Bay so I don’t think this is correctly drawn. Fourth, the “enlarged view” panel B is about the same scale as panel A. I would suggest revising the figure to make this a full panel perhaps so that the reader to more easily see the geography of Kane Basin. Or just remove panel B and highlight the extent of panel C in panel A. Finally, for panel D, it would be helpful to highlight where coastal boundaries are under snow/ice. Also highlight the extent of these images in panel A or B.
L88: Please provide brief description of storage conditions for subsamples post sampling. This is important for organic proxies, e.g., TOC and lipids.
L95: What program was used to make the age model? I would suggest using a Bayesian approach (e.g., rbacon) that can account for age uncertainty for proxy sample depths.
L114: Please include further details on analytical standards used to correct for linearity, drift, etc., and what the stable isotope are in reference to (e.g., VPDB, Air).
L115: What does “combined” refer to? What two methods are being used here? Please clarify.
L124: How many measurements were made per a sample to create the average? If the standard deviation of these is large enough to be seen in plots, it would be good to include there and discussed where relevant in text.
L132: I think HBI III being a marginal ice zone marker is an oversimplification. See studies by Amiraux et al. (2019, 2021) and Harning et al. (2023) from the area on the seasonal production and modern distribution of HBI III.
L139: Please include sterol standards as well.
L142: Blowing down to complete dryness can result in the loss of volatile lipids. Is this what was actually done? Standard procedure for lipid analyses is typically to blow down under N2 most of the way, and let the remaining solvent evaporate on its own under a hood.
L147: No alkenone data is reported so this can be removed from GC-MS analyses. Also, please provide further information on analyses, i.e., GC oven program, GC column, etc.
L149: It’s unclear if your RF was calculated over a range of standard concentrations or not. Please clarify.
L150: Please provide reference for sterol mass spectra used as well, Belt et al. (2007) is just for HBIs.
L156: What c-value was used? Harning et al. (2023), Kolling et al. (2020), other? I think it would also be worth mentioning and somehow folding into the discussion is that PIP25 analyses from Baffin Bay surface sediment are not always consistent with inferred sea ice conditions (Kolling et al., 2020; Harning et al., 2023).
L174: I would suggest including PCA with GAMs (in the following section) into a single section on data analyses, or something similar.
L175: Can you briefly state the purpose of Hellinger transformation? I imagine most people reading this paper will not be familiar.
L185: How was overfitting determined when selecting your k?
L199: These grain size ranges are not shown in Fig 2, please include them there if referenced as is.
L204: Phrasing awkward. Edit to “In addition, several distinct IRD layers found in 6.2BC…” and remove mentioning of core from end of sentence.
Figure 2: Clarify that concentrations are ug/g TOC in axis labels, if they are presented this way. If normalized to g sed, please denote as ug/g sed here and throughout text. The reference for d13C is VPDB, not PDB. Instead of “organic isotopic composition” rephrase as “carbon stable isotopes”. 14C is also an organic carbon isotope but radiogenic.
L209 (and throughout): Please include standard deviation, or some quantitative form of error, if stating averages. Is this mean or median?
L215: Are there any differences in C/N ratios between open water and sea ice associated organic matter?
Figure 3: Sea ice and terrestrial labels on panel b are confusing, please clarify what they are indicating.
L226: Why were sterols only analyzed in one core? This should be mentioned up front in the methods as well – it feels a little hidden.
L231: Include reference for first sentence.
L232 (and throughout): When mentioning concentrations, please note/clarify whether normalized to g sed or g TOC, instead of just g.
L239: Given that age uncertainties differ for the oldest portions of each record and that different environmental conditions exist for the two sites, I would suggest also performing these PCA analyses on each individual record. Do the trends hold up?
L241: Is 2000-2014 labeled as 2000-2009 in the figure? Please check. I also don’t know if this clustering is true. The two time periods plot in separate quadrants.
L248: For Brig., this is also in a different quadrant than the others. Therefore, I think the period 1950-2000 is also important for Brig. as it is “pulling” Brig. into the bottom left quadrant.
Figure 4: Can you plot the samples too please? Also please plot the 0 lines in light gray or something to more easily visualize the quadrants. What do the different colors for taxa mean?
L264: Would be helpful to reiterate the TOC range of each record separately here at the end of the sentence.
L271: Is this d13C value mean or median? Also please specify plus/minus error.
L274: Same comment as above for C/N.
Figure 5: It would be helpful to provide depths of sample slides here for reference
L301: As the Pacific water is also rich in nutrients, it would be helpful here to have some numbers on how these water masses differ re nutrients. This info could also be placed in the background near the front of the ms, and referenced briefly here again. For the latter, I would encourage a short section of the manuscript focused on local oceanography following the introduction.
L305: Can you hypothesize how/why this would occur? As written it is too vague.
Figure 6: For the mean annual change rates calculated from multiple frontal positions, it would be helpful to plot the raw data as well, or some st dev for those years.
L334: Spell out LIA - I don’t think there is a need to abbreviate. This will also avoid any potential confusion with the other LIA (Last Ice Area).
L337: It looks like some of the decreasing trends for GAMS start before - looking at significant changes could be helpful as to me, some of these trends look flat (see example from Schneider et al., 2024). Also, was the uppermost sample excluded from GAM? If not, then it is accounted for in the model. Being one data point it just may not be significant enough to impact the trend so I suggest rephrasing to acknowledge this.
L346: I would not say these are “notable”. The range is actually quite small compared to Holocene records of these biomarkers from the region (e.g., Georgiadis et al., 2020; Detlef et al., 2021; Jackson et al., 2021; Harning et al., 2025). I would suggest changing to minimal to reflect this. This would then precede your GAM conclusions well.
Figure 7: What is PIpP25 and where do c-values come from? Please clarify as different local c-values in Baffin Bay impact inferred sea ice conditions (see Harning et al., 2023). Why no GAM for PIP? Please also darken gray vertical bars, they are hard to see.
L383: I’m not sure you’ve mentioned failed ice bridge formation in the discussion yet. Can you make the connection clearer?
L395: Again, this isn’t quite true based on modeling but okay since the contrary evidence is still in preprint.

Technical comments:
L50: Remove with
L110: I think these first two paragraphs should be one
L209 (and throughout): Spaces between number and units. % is a unit
L228: remove “the” before brassicasterol and dinosterol

References
Amiraux, R., Smik, L., Köseoğlu, D., Rontani, J.-F., Galindo, V., Grondin, P.-L., Babin, M., Belt, S.T., 2019. Temporal evolution of IP25 and other highly branched isoprenoid lipids in sea ice and the underlying water column during an Arctic melting season. Elementa-Sci. Anthrop., 7, 1–23.
Amiraux, R., Archambault, P., Moriceau, B., Lemire, M., Babin, M., Memery, L., Massé, G., Tremblay, J.-E., 2021. Efficiency of the sympagic-benthic coupling revealed by n-3 fatty acids, IP25 and other highly branched isoprenoid analyses of two filter-feeding Arctic benthic molluscs: Mya truncate and Serripes groenlandicus, Org. Geochem., 151, 104160.
Detlef, H., Reilly, B., Jennings, A., Jensen, M.M., O’Regan, M., Glasius, M., Olsen, J., Jakobsson, M., Pearce, C., 2021. Holocene sea-ice dynamics in Petermann Fjord in relation to ice tongue stability and Nares Strait ice arch formation. The Cryosphere 15, 4357-4380.
Georgiadis, E., Giraudeau, J., Jennings, A., Limoges, A., Jackson, R., Ribeiro, S., Massé, G., 2020. Local and regional controls on Holocene sea ice dynamics and oceanography in Nares Strait, Northwest Greenland. Marine Geology, 442, 106115.
Harning DJ, Holman, B, Woelders, L, Jennings, AE, Sepúlveda J, 2023. Biomarker characterization of the North Water Polynya, Baffin Bay: Implications for local sea ice and temperature proxies. Biogeosciences 20, 229-249.
Harning DJ, Jennings AE, Holman B, Kelleher RV, Feng S, Brooks NKS, Andrews JT, Marchitto T, Sepúlveda J, 2025. Spatiotemporal variability in the Holocene extent of Pikialasorsuaq (North Water Polynya), Baffin Bay. Paleoceanography and Paleoclimatology 40, e2025PA005153.
Kolling, H. M., Stein, R., Fahl, K., Sadatzki, H., de Vernal, A., Xiao, X., 2020. Biomarker distributions in (sub)‐Arctic surface sediments and their potential for sea‐ice reconstructions. Geochemistry, Geophysics, Geosystems, 21(10), e2019GC008629.
Lenetsky, J., Jahn, A., Ugrinow, P., Wyburn‐Powell, C., Patel, R., Zanowski, H., 2025. Future Sea ice‐ocean and biological productivity changes in the North Water Polynya region under policy relevant warming levels. Earth. Preprint. https://doi.org/10.31223/X55X6J
Schneider, T., Castañeda, I.S., Zhao, B., Krüger, S., Salacup, J.M., Bradley, R.S., 2024. Tracing Holocene temperatures and human impact in a Greenlandic Lake: Novel insights from hyperspectral imaging and lipid biomarkers. Quaternary Science Reviews 339, 108851.

Citation: https://doi.org/10.5194/egusphere-2025-2641-RC2

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Short summary

We compare two marine sediment cores collected from contrasting locations in Kane Basin, northwest Greenland. The two sites differ in terms of sedimentation rates, primary production, and organic matter composition and source. Despite these spatial differences, both records reveal a similar long-term trend, a shift from cold, heavy sea ice influenced conditions between ca. 1750–1900 CE, towards more open, fresher, and biologically productive waters beginning around 1950 CE.


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