| 13 May 2026
Sea ice variability and links to East Siberian permafrost carbon remobilization during the last glacial-interglacial transition
Abstract. Sea ice in plays a central role in the polar climate system. In recent decades, the rapid decline of Arctic sea ice has triggered cascading effects the albedo effect and gas/heat transfer in polar regions. Investigations of earlier warming events, such as the Preboreal/Early Holocene (PB/EH, 11–8 kyr B.P), Bølling-Allerød (B/A, 14.7–12.9 kyr B.P), and Dansgaard Oeschger event 3 (DO-3, 28–27.5 kyr B.P), likely hold clues on climate system responses to changes in Arctic sea ice. This study explores the history of sea ice over the Southern Lomonosov Ridge and its potential relation to permafrost carbon remobilization. Sea ice conditions over the last 27 kyrs were reconstructed through a combination of the sea ice biomarker IP25 (Ice-proxy 25) and marine phytoplankton biomarkers (brassicasterol and dinosterol) from the chronologically well-constrained core 31-PC, sampled at the Southern Lomonosov Ridge during the SWERUS-C3 expedition in 2014. The reconstruction allowed for a direct comparison with previously published terrestrial organic carbon (terrOC) remobilization history from the same core. Our findings revealed a seasonal sea ice cover between 27–26 kyr B.P after the DO-3 warm event, which likely caused more heat and moisture transport from ocean to land and strengthened permafrost thawing along the nearby coastline. A perennial sea ice cover then developed and persisted throughout the Last Glacial Maximum (LGM) to the Younger Dryas (YD), including over the entire B/A warm period. Due to sea-level rise during Meltwater Pulse 1A (MWP 1A, 14.7–13.5 kyr B.P), terrOC remobilization during B/A was rapid but its magnitude smaller when compared to PB and DO-3 in 31-PC, and other records from the Arctic. These records collectively suggest that sea-level rise, rather than sea ice conditions, exerts the primary control on coastal erosion during B/A, while we propose that the perennial sea ice cover may have limited wave-induced coastal erosion on the continental shelf bordering the southern Lomonosov Ridge. A sharp reduction and breakup of the perennial sea ice was observed from the PB to the Early Holocene. Contrary to the B/A, Meltwater Pulse 1B during PB triggered significant coastal erosion and massive terrOC remobilization concurrent with the sea ice decline. The absence of sea ice in parallel to larger coastal erosion compared to B/A implies the role of waning sea ice in enhancing permafrost carbon mobilization along the coastline in this period. In accordance with sea ice records from other Arctic seas, the Holocene record exhibited a period of gradual sea ice expansion. Taken together, these findings highlight sea ice extent as a possible factor regulating coastal permafrost carbon remobilization during the last deglaciation.
The manuscript „Sea ice variability and links to East Siberian permafrost carbon remobilization during the last glacial-interglacial transition“ by Eriksson et al. addresses the important aspect of coastal erosion contributing organic carbon to the Arctic Ocean during time intervals of climate warming. The authors specifically investigate sea ice conditions recorded in a sediment core from the southern Lomonosov Ridge throughout the past 27 ka and how these may have impacted the stability of permafrost in the Laptev Sea region. By means of the sea ice biomarker IP25, phytplankton and terrestrial biomarkers, the authors provide a continuous record documenting periods of permanent sea ice cover during peak glacial times versus reduced sea ice cover during the Holocene and a variable organic matter export from land reaching the core site. Drawing on previously published data from the sediment core, the authors interpret this input of terrigenous organic matter in the context of coastal and permafrost erosion driven by changes in sea-ice cover and/or sea level rise. The manuscript is generally well written and the data a valuable contribution to the assessment of ice-ocean-land interactions and I hence recommend publication. However, the manuscript also exhibits some weaknesses, regarding the interpretation of own but also of previously published data. In several instances, relevant literature has not been adequately taken into account, and some published findings are represented inaccurately or interpreted in a manner that is not fully consistent with the original reports (see detailed comments below). Addressing these issues would further strengthen the manuscript and improve its scientific rigor. Regarding the interpretation if either sea ice or sea level change drove coastal erosion and organic matter export during the deglacial, it would, for example, be helpful to include a sea level record in one of the figures and to also discuss local records investigating deglacial sea level rise in the Laptev Sea (e.g. Bauch et al., 2001; Taldenkova et al., 2013). More specific comments are listed below.
Line 10: something is wrong with the wording here
Line 11: please correct here and elsewehre B.P. (not B.P)
Line 15: (Ice Proxy 25)
Line 21: delete ‘over’
Line 35: delete ‘with’
Line 39: here, you could also mention the role played by expanded sea ice in shifting the westerly winds southward (and thus reducing the impact of warm/moist air on permafrost) – see e.g. Vandenberghe et al. (2012)
Lines 40-41: Vaks et al. (2020) is maybe not the best reference regarding “past periods of abrupt climate change” as their study rather deals with the onset of perennial sea ice cover affecting moisture transport 400 kyrs ago
Line 53: (Ice Proxy with a 25 carbon atom skeleton; Belt et al., 2007)
Line 53: I suggest to rephrase: “the application of IP25 is limited by two scenarios that result in the lack of IP25: the absence of an ice cover (which serves as the habitat for the sea ice diatoms that synthesise IP25), and the presence of a permanent and thick ice cover that limits the light penetration through the ice and, consequently, the growth of sea ice diatoms (Müller et al., 2009)”.
Line 71: please specify that it is Late Pleistocene
Line 120: replace ‘content’ with ‘compounds’
Line 133: “Identification of IP25 was based on the retention times of the compound in reference sediments”. Were at least some of the samples analyzed in full scan mode (to get mass spectra)? This would be very helpful for a more reliable identification of IP25. The C25 HBI monoene and diene have a very similar retention time and often overlap, and here mass spectra would be crucial for a proper identification of IP25.
Line 136-137: have any instrumental response factors been considered for the quantification of the HBIs and sterols? If not, this is ok, but please state it as it may be relevant for quantitative comparisons with other published records.
Line 155: please add a sentence on how the fluxes were determined
Lines 196-197: “The DO-3 event (28-27.5 kyr B.P) is likely recorded in 31-PC (spanning 27.2 ± 2.3/-1.4 kyr B.P”. Looking at figure 3 and lines 155 -157, there seem to be no data points covering the DO-3 event. The first signals date to 27.2 ka - so the discussion of DO-3 is a bit misleading here. It may be helpful if you further explain the age model uncertainty for this section of the core and indicate this in the figure.
Line 198: seasonal sea ice ‘cover’ (not ‘conditions’)
Line 202: seasonal sea ice ‘cover’ (not ‘conditions’)
Line 219- 221: this sounds like a concluding remark and I suggest moving this sentence to the conclusion accordingly - and please remove one of the two ‘impacts’
Line 231: please explain HS-1
Line 233: I suggest to rephrase “...that thick sea ice inhibited the growth of open-water phytoplankton but also hindered ice algae growth by limiting light penetration through the ice”
Line 237-238: could polynyas have played a role here, too?
Lines 244 and following: this line of reasoning is a bit difficult to follow. Just a few lines earlier, you state that other records from the Laptev Sea indicate seasonal or ice-free conditions at the continental shelf during HS-1. Since these sites are located closer to the coast, the argument that a permanent ice cover (recorded at 31-PC on the southern Lomonosov Ridge) would have reduced coastal erosion does not hold up.
Lines 247-249: here, you note that permanent sea ice cover minimized the erosion/input of older carbon, whereas pre-depositional 14C ages reach their maximum between 26 and 24 ka (Fig. 5)
Line 274: I suggest to delete “in the context of sea ice”
Line 278: in addition to sea level rise, could it be that atmospheric warming has also contributed to the increased thawing of older permafrost deposits?
Line 279: looking at figure 5, MWP-1A (14.5 – 14 ka BP) actually coincides with a drop in pre-depositional 14C ages...
Line 284: same comment as above for HS-1: permanent sea ice at site 31-PC but seasonal/ice-free conditions at more coastal sites in the Laptev Sea during the B/A permitting coastal erosion
Line 296: During the PB/EH transition,
Line 300: I guess you mean “warm early (not late) Holocene” - however, Hörner et al. (2016) identify a decreasing sea ice cover during the early Holocene
Line 303 and 304: again, Hörner et al. (2016) (and Lin et al. 2024) actually report a decrease in sea ice cover during the early Holocene. The PIP25 record of core PS51/154-11 shown in figure 4 is a bit misleading here as Hörner et al. (2016) point out that additional (freshwater-derived) brassicasterol affects the interpretation of this lipid as phytoplankton marker in this time interval (which also limits its usefulness for calculating the PIP25 index). Maybe core PS51/159 discussed by Hörner et al. (2016) is better suited?
Line 309-311: looking at the pre-depositional ages of core 31-PC in figure 5, there is just one data point reflecting an old (ca. 15000 year) 14C-OC age at ca. 9 ka (while MWP-1B occured distinctly earlier at ca. 11.3 ka BP) – I suggest to rephrase this sentence
Line 321: “...phytoplankton and sea ice algae productivity”
Line 336: “...using the sea ice biomarker IP25 and open-water algae biomarkers...”
Figures
References
Bauch, H.A., Mueller-Lupp, T., Taldenkova, E., Spielhagen, R.F., Kassens, H., Grootes, P.M., Thiede, J., Heinemeier, J. and Petryashov, V.V. (2001) Chronology of the Holocene transgression at the North Siberian margin. Global and Planetary Change 31, 125-139.
Müller, J., Massé, G., Stein, R. and Belt, S.T. (2009) Variability of sea-ice conditions in the Fram Strait over the past 30,000 years. Nature Geoscience 2, 772-776.
Stein, R., Frederichs, T., Fahl, K., Geibert, W., Matthiessen, J., Niessen, F., Vogt, C., Sassenroth, C. and Bazhenova, E. (2025) A 430 kyr record of ice-sheet dynamics and organic-carbon burial in the central Eurasian Arctic Ocean. Nature Communications 16, 3822.
Taldenkova, E., Bauch, H.A., Stepanova, A., Ovsepyan, Y., Pogodina, I., Klyuvitkina, T. and Nikolaev, S. (2013) Reprint of: Benthic and planktic community changes at the North Siberian margin in response to Atlantic water mass variability since last deglacial times. Marine Micropaleontology 99, 29-44.
Vandenberghe, J., Renssen, H., Roche, D.M., Goosse, H., Velichko, A.A., Gorbunov, A. and Levavasseur, G. (2012) Eurasian permafrost instability constrained by reduced sea-ice cover. Quaternary Science Reviews 34, 16-23.