An appraisal of ancient Earth’s climate dynamics is crucial for understanding the modern climate system and predicting how this might change in the future. Major climate-shift events in the Earth’s past demonstrate the scale, duration and response of the climate system to various global and local climate stressors.   

More than 650 million years of deep-time paleoclimate changes are archived in the sedimentary succession of Svalbard; an archipelago located in the Norwegian High Arctic. The excellently outcropping geological successions of Svalbard date back to the Proterozoic, and record both temporal and spatial changing climatic and environmental conditions strongly linked to the northward continental drift of the archipelago from southern hemisphere in Precambrian to its present-day Polar latitudes.

The oldest deposits that record major climatic events and associated environmental perturbations in Svalbard include tillites related to several Cryogenian glacial events and the overlying Ediacaran carbonates. The Lower Paleozoic succession documents episodes of marine biodiversification, including the Great Ordovician Biodiversification Event (GOBE), which is linked to cooling of previously warm tropical oceans. The arid to semi-arid climate of the Devonian promoted a terrestrial plant diversification. The Lower Carboniferous coal-bearing strata were deposited in humid and tropical climate settings prevailing in northern Pangea. The Upper Carboniferous-Lower Permian succession consists of interbedded carbonates, evaporites and red siliciclastics, including remains of paleokarst. The continued northward drift into subtropical latitudes promoted a change back to arid to semi-arid climates, occurring during the overall global icehouse conditions. During the Late Permian, marine sponges were occupying most of the ecological niches, leading to the deposition of weathering-resistant spiculites. But these ecosystems were rapidly and dramatically impacted by the End Permian Mass Extinction (EPME), which lasted well into the Early Triassic.

By the Mesozoic, Svalbard was approaching mid-latitudes. The exposed in Svalbard deposits of Triassic mega-delta features evidence for a temperate or humid climate, indicated by thick coal beds that transitioned to an arid climatic environment at the end of the Triassic and Early Jurassic succession with caliche and calcareous soil profiles. The Lower Cretaceous strata (deposited at c. 66 °N) record several cold snaps despite the overall greenhouse climate characterizing the period and most notably the global crisis associated with the Aptian oceanic anoxic event 1a (OAE1a).

By the Paleogene, Svalbard had reached Arctic latitudes, and as characterised by overall moderate to warm temperate climate, punctuated by warming episodes, including the Palaeocene–Eocene Thermal maximum (PETM). The Neogene cooling is missing from onshore records, but high-resolution glacial climate evidence exists offshore and from geomorphology and unconsolidated strata of Late Quaternary-Holocene age.

In this contribution, we synthesize former and ongoing studies of deep-time paleoclimate in Svalbard and provide knowledge gaps to optimize the use of Svalbard as an archive for deep-time paleoclimate research. The exceptional exposures, accessibility, and completeness of the 650 million long sedimentary records makes Svalbard unique archive for deep-time paleoclimate research. In addition to Svalbard’s excellent outcrops, fully cored research and coal exploration boreholes provide an excellent foundation for further research with minimal environmental consequences.

How to cite: Smyrak-Sikora, A., Augland, L. E., Betlem, P., Grundvåg, S.-A., Helland-Hansen, W., Jelby, M. E., Jensen, M. A., Jochmann, M. M., Johanessen, E. P., Jones, M. T., Koevoets-Westerduin, M., Lord, G. S., Mørk, A., Olaussen, S., Planke, S., Senger, K., Stemmerik, L., Vickers, M., Śliwińska, K. K., and Zuchuat, V.: Deep-time paleoclimate archive in High Arctic, Svalbard, Norway, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7172, https://doi.org/10.5194/egusphere-egu22-7172, 2022.

One of the most dramatic warming episodes of the Mesozoic occurred near the Pliensbachian-Toarcian transition (Early Jurassic). The occurrence of abundant exotic clasts and glendonites in marine strata of Siberia suggests cold conditions during the late Pliensbachian, which may have led to the episodic growth of high latitude ice-sheets. These conditions ended abruptly during the early Toarcian when temperature rose rapidly across an episode of global biogeochemical perturbation known as the Toarcian Oceanic Anoxic Event (T-OAE). The rapid marine transgression coinciding with the T-OAE onset has been tentatively attributed to the rapid demise of these polar ice-sheets, which possibly released large amounts of methane in the atmosphere through permafrost thawing. Nevertheless, the scarce quantitative estimates of Pliensbachian-Toarcian temperatures have exclusively been obtained from low paleolatitude sites. Plus, existing temperature records are mostly based on oxygen isotope thermometry and hence remain equivocal in the absence of constraints on the ocean oxygen composition of Pliensbachian-Toarcian oceans and its temporal variability. Clumped isotope (Δ₄₇) data from aragonite bivalve shells from one NE Siberian site have recently provided the first quantitative evidence for extreme Toarcian polar warmth, with marine temperature estimates exceeding ~15°C north of the Anabar shield. In this study, we present new Δ₄₇ data from bivalve samples from Tyung River, south of the Anabar shield that allow to substantially expand this record both spatially and temporally. Clumped isotope data from aragonite shells confirm elevated marine temperatures (~13°C) at the end of the T-OAE in polar areas some 850 km away from the previous record. Upper Pliensbachian calcite shells of Harpax collected from coastal to deltaic, boulder-bearing deposits of a nearby site record much lower temperature (~3°C) and extreme ¹⁸O-depletion of environmental waters (δ¹⁸O = -6.5‰VSMOW). These results provide the first quantitative evidence for near-freezing polar temperatures during the Late Pliensbachian, which is a key prerequisite for the hypothesis of episodic ice-sheet growth prior to the T-OAE. Beyond glacio-eustasy, our new data offer a rare glimpse of extreme changes in polar temperatures across a transition from coldhouse to greenhouse climate and will certainly prove useful for future earth system simulations of Mesozoic climates. 

How to cite: Letulle, T., Suan, G., Rogov, M., Daëron, M., Vinçon-Laugier, A., Lutikov, O., Reynard, B., Montagnac, G., and Lécuyer, C.: First quantitative constraints on the Pliensbachian-Toarcian warming in polar regions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7286, https://doi.org/10.5194/egusphere-egu22-7286, 2022.

The Eocene bryozoans reveal a spectacular diversification in the stratigraphical column of the LMF, Seymour Island, showing a great variation in the colony growth-forms and taxonomy enhanced by a great radiation of a new taxa (Hara 2001).

The very base of the sandy, transgressive series in the lowermost part of the LMF (Telm1) includes loosely encrusting (membraniporiform), and unizooidal, flexible articulated or rooted colonies (catenicelliform), which are either taxonomically and morphologically different from the overlying fauna. At present such bryozoans are widely distributed in the tropical-warm temperate latitudes particularly deposited in the shallow-water settings (Hara 2015).

The massive, hemisperical cerioporine cyclostomes, reminiscent of the Cretaceous in the Northern Hemisphere and differently-shaped multilamellar cheilostomes represented by numerous new taxa are dominant biota in the lower part of Telm1-2 (Hara 2001, 2002).

The free-living lunulitiform, disc-shaped colonies, which occur in the middle part of the LMF (Telm4-Telm5), are characteristic for the warm, shallow-self environment with a temperature range of 10 to 29°C. Environmentally, lunulitids are absent when the bottom sediments is lower than 10-12°C. At present they inhabit the circumpolar to warm-temperate waters (Hara et al. 2018). They have bimineralic skeletons, with the traces of aragonite, which is indicative for the temperate shelf environment, sandy and often shifting substrate.

The bryozoans from the upper part of the LMF (Telm6-Telm7) are scarce, either represented by in-situ lepraliomorph biostrome layer up to 5 cm thick or poorly-preserved sole fragments of the bryozoans associated with penguins and fish remains.

Changes in the biotic composition of the diversified bryozoan biota of the late early Eocene-late Eocene in the stratigraphical column of the LMF mark a distinct environmental and climatic events, referred to EECO, MECO, and EOT for the upper part of this formation.

The isotopic δ¹⁸O analyses of the bryozoan skeletons from the lower part of the La Meseta Fm. show the temperature range from 13.4°C to 14.6°C (according to the equation given by Anderson & Arthur 1983; unpublished Hara 2021; what is consistent with isotopic data of other marine macrofaunal fossil records (see Ivany et al. 2008).

Anderson T.F., and Arthur M.A.1983. Stable isotopes of oxygen and carbon and their application to sedimentologic and paleoenvironmental problems. SEPM Short Course, 10: 1-151.

Hara U. 2001. Bryozoans from the Eocene of Seymour Island, Antarctic Peninsula. Palaeontologia Polonica 60: 33-155.

Hara U., 2002. A new macroporid bryozoan from Eocene of Seymour Island, Antarctic Peninsula, Polish Polar Research, 23: 213-225.

Hara U. 2015. Bryozoan internal moulds from the La Meseta Formation (Eocene) of Seymour Island, Antarctic Peninsula. Polish Polar Research, 36: 25-49.

Hara U., Mors T., Hagstrom J. & Reguero M. A., 2018. Eocene bryozoans assemblages from the La Meseta Formation of Seymour Island. Geological Quarterly, 62: 705-728.  

Ivany L.C., Lohmann K. C. Hasiuk F., Blake D.B., Glass A., Aronson R.B., & Moody R.M. 2008. Eocene climate record of the high southern latitude continental shelf: Seymour Island, Antarctica. Geological Society of America Bulletin, 120: 659-678.

How to cite: Hara, U.: Evolution of the Antarctic bryozoan biota as a response to environmental and climatic changes: (Eocene, La Meseta Formation, Seymour Island, Antarctic Peninsula), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12131, https://doi.org/10.5194/egusphere-egu22-12131, 2022.

The extent of Arctic sea-ice during the Last Interglacial is poorly known. Climate models and sediment-based reconstructions generally suggest a relatively extensive ice cover, comparable to the modern day. Here, we show that Arctic sea-ice was much more reduced than previously assumed, with summers being ice-free. Our new evidence stems from a series of central Arctic Ocean sediment cores, including sites that underlie the thickest parts of the modern Arctic ice pack. Microfossil analysis reveals that the Arctic Ocean was invaded by Turborotalita quinqueloba, a typically subpolar planktonic foraminifer that is strongly associated with chilled Atlantic waters in the modern North Atlantic Ocean, and which is absent in modern sediments in the central Arctic Ocean. Given that the modern Arctic Ocean is characterised by a pronounced halocline with Atlantic waters subducting beneath a fresh and cool upper water mass, our findings suggest a shallowing of those Atlantic waters in the Arctic Ocean during the Last Interglacial. This process, dubbed ‘atlantification’, would be associated with retreating sea-ice, allowing T. quinqueloba to invade. Since the onset of the atlantification of the Arctic Ocean in response to climate change is increasingly being reported, we suggest that the Last Interglacial may serve as an important analogue for studying a fully-atlantified, seasonally ice-free Arctic Ocean.

How to cite: Vermassen, F., O'Regan, M., de Boer, A., West, G., and Coxall, H. K.: A seasonally ice-free Arctic Ocean during the Last Interglacial, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10379, https://doi.org/10.5194/egusphere-egu22-10379, 2022.

Although sedimentary ancient DNA (sedaDNA) is increasingly used to reconstruct past ecosystem changes, we do not yet know much about its preservation conditions across geological time, resulting in potential biases and uncertainties in data interpretation. In this study, we obtained sedaDNA records from around 15 lakes from the Arctic and sub-Arctic regions and the Tibetan Plateau covering the last 2 to 80 ka BP. In addition to the four preservation proxies recently introduced by Jia et al. (2021) (https://doi.org/10.1002/edn3.259), some new potential proxies of plant DNA metabarcoding (e.g., dissimilarity between PCR replicates) and metagenomics (e.g., average DNA fragment length, duplication rate, guanine-cytosine content, and deamination rate) have also been applied to quantify the extent of ancient DNA preservation and compared with other environmental proxy records from the cores. So far, our preliminary results from Lake Ilirney (67°21’N, 168°19’E) show that DNA content generally decreases along the core over the last 18 ka BP and then maintains at a relatively stable level up to the bottom of the core (ca. 53.4 ka BP), which is consistent with the variations in lake organic productivity reflected by TC, TOC, TOC/TN, pollen and diatom abundance, and Br. In addition, sedaDNA preservation conditions revealed by our preservation proxies are variable within the core. Good sedaDNA preservation is associated with strong physical weathering and glacial abrasion in the catchment, as indicated by high K/Ti and low Zr/Rb values, resulting in increased clastic input of clay minerals and fine sediments, which favors the adsorption of DNA molecules to sediment particles. This process might also help to deepen the lake and increase its water conductivity, which is beneficial for DNA adsorption and preservation. No clear correlation is found between sedaDNA preservation and paleoclimatic changes reconstructed by fossil pollen records. It should be noted that our results may also be influenced by the ability of the DNA extraction protocols we used to recover DNA from different types of sediments. To conclude, sedaDNA preservation may be highly influenced by sediment type and catchment erosion rate, and glacial lakes appear to be promising for sedaDNA studies in the future. Further analyses of sedaDNA records from other lakes are pending and will be finalized and presented at EGU 2022.

How to cite: Jia, W., Cabuk, U., R. Stoof-Leichsenring, K., G. Alsos, I., Lammers, Y., K. Biskaborn, B., and Herzschuh, U.: Uneven preservation of ancient DNA along lake sediment cores: A case study of high-latitude and high-elevation lakes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11897, https://doi.org/10.5194/egusphere-egu22-11897, 2022.

Ongoing climate change causes a global biodiversity loss and species extinction by reducing population size and decreasing genetic diversity. Massive extinction events happened in the past with the Megafauna extinction as the latest example. The Pleistocene-Holocene transition also witnessed the loss of the broadly established steppe-tundra biota, spanning most of Northern Hemisphere during the Pleistocene and supporting Pleistocene megafauna at the time. Understanding past extinction events via the investigation of Quaternary records can strengthen the current methods to forecast the effects of global warming on ecosystems. If loss of other organism groups were proportional to what has been shown for mammals, a large part of the Pleistocene steppe-tundra biota might have gone extinct. However, few example are known. The improved taxonomic resolution and high detectability of sedimentary ancient DNA provide a new tool to explore this. Here, we investigate potential plant taxa loss in the Northern Hemisphere between the late Pleistocene-Holocene transition using sedimentary ancient DNA (sedaDNA) metabarcoding. We summarized data from 500 samples comprising nine lake sediment cores from North-East-Asia and North-America spanning the last 50.000 years. Using patterns of past plant diversity (appearance-disappearance through time), we built communities to detect past taxa non-present in modern databases inferring potential candidates for extinction. Our results suggest that vegetation was resilient until the Pleistocene to Holocene transition and that loss appeared in parallel to the Megafauna extinction. Finally, we characterized this vegetation loss and identified that more specialist taxa contributing less to beta diversity are more sensitive to potential extinction than other taxa. This work holds great potential to reveal new insights into the evolution of the fragile boreal plant communities and the processes leading to extinction of species.

How to cite: Courtin, J., Alsos, I., Biskaborn, B., Diekmann, B., Huang, Y., Lammers, Y., Melles, M., Pestryakova, L., Schulte, L., Stoof-Leichsenring, K., and Herzschuh, U.: Identification and characterization of vegetation loss during the last 50,000 years in Beringia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11180, https://doi.org/10.5194/egusphere-egu22-11180, 2022.

The central part of West Spitsbergen, Nordenskiöld Land, is characterized by comparably small extension of glaciers, high landscape diversity and the long-term development of river valleys. In doing so the number of objects suitable for paleobotanical, in particular, palynological research is limited. Holocene climate and vegetation in numerous studies were reconstructed by using palaeobotanical data from lake sediments and peat sequences. Fluvial sediments are widespread and include both terrigenous and organic deposits, but studies focussing on alluvium archives are rare. Such records relate to Coles and Gröndalen valleys.

During the researches of the Russian Arctic expedition in the Svalbard archipelago in 2019, the outcrop of marine sediments overlain by an alluvial stratum (with a general thickness of 4.2 m) was found and studied on the right slope of Semmeldalen valley (16 m a.s.l.). The sediments are represented by sand and silt with Mytilus edulis shells in situ (0.2 m), which are covered by gravel-pebble material (2.0 m), followed by stratum of interlayered silt, sand, loam with plant remains lenses and layers (2.0 m). The laboratory studies included radiocarbon dating and pollen analysis. Radiocarbon dating results show that the studied deposits were formed in the period from 9300 to 3500 cal BP.

According to pollen data, six stages of vegetation and climate changes were distinguished.  The first stage - about 9300 - 9000 cal. BP corresponds to the stage of sedimentation in a shallow sea bay under relatively favourable environmental conditions. The deposits contain rare microfossils of poorly preserved shrub forms. The almost total absence of Quaternary pollen and a spore in the second stage - gravel-pebble sequence - reflects a high rate of sedimentation in the river mouth during sea regression.  About 8700 cal BP (stage 3) the subshrub-sedge tundra developed in a relatively warm and humid climate. Following (about 8300 cal BP) it changed by the willow-sedge tundra (stage 4). The low content of microfossils at this stage is evidence of an increase in river runoff and, probably, an increase in the amount of atmospheric precipitation. Most probably study records contain a hiatus in sedimentation between 8000 - 4000 cal BP. The fifth stage is the increase in pollen amount and development of the willow-motley-grass tundra. The sixth stage reflects modern vegetation - willow-grass tundra.

The obtained dates and lithology description allow us to make a preliminary conclusion that a sharp decrease in sea level occurred about 9000 cal BP, thereby determining a radical restructuring of the natural environment of the study area. Preliminary results compared with published data show that there are local differences in valley development and environmental conditions changes in Central Svalbard during the Holocene.

How to cite: Soloveva, D., Verkulich, S., Savelieva, L., and Petrov, A.: Holocene environmental changes inferred from pollen record of Nordenskiöld Land alluvium sequences (West Spitsbergen Island): new data and review, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8394, https://doi.org/10.5194/egusphere-egu22-8394, 2022.

Multiple geochemical analyses may help us better constrain the ice-wedge formation and in-situ greenhouse gas (GHG) production mechanisms. Here we present new results from ice-wedge ice sampled at Zyryanka, Northeastern Siberia (65°93’N, 150°89’E). The plant remains and CO₂ gas were analyzed for ¹⁴C dating, and we obtained from 810 to 1750 years before 1950 CE for the Zyryanka ice wedge. δ(N₂/Ar) of the ice wedges ranges from -17.51 to -3.53 % with regard to modern air, indicating that the Zyryanka ice wedge was formed by both liquid water and dry snow. On the other hand, the δ(O₂/Ar) value of the Zyryanka ice wedges ranges from -72.88 to -37.58 % with regard to modern air, implying oxygen gas was consumed considerably by respiration of microorganisms in the ice-wedge ice. We also observed correlations among the three greenhouse gas species and oxygen gas concentrations. N₂O and CO₂ concentrations show a strong positive correlation (r = 0.94, p=0.01). We also found that the melting fraction (estimated from N₂/Ar) is positively correlated with CO2 (r=0.81, p=0.01) and CH₄ (r=0.87, p<0.05). Furthermore, O₂ concentration is negatively correlated with the CH₄ concentrations (r = -0.41, p<0.05) which may imply that CH₄ production is associated with biological oxygen consumption. The δ¹⁸O of ice melt ranges from -28.6 to -19.1 ‰ for the ice wedge and adjacent soil samples, showing a symmetric structure with low δ¹⁸O values in the ice wedge parts and high in the adjacent soils. Comparing with the δ¹⁸O value of modern precipitation in the Zyryanka region, it can be inferred that the ice wedge was mainly formed by filling with cold seasonal precipitation. Our study shows that the gas mixing ratios in ice wedges and water stable isotope analysis may help better understanding the biogeochemical environments during and after the formation of ice wedges.

How to cite: Ko, N., Park, H., Jung, H., Iwahana, G., Fedorov, A., and Ahn, J.: Understanding formation of ice wedges and origin of trapped greenhouse gas at Zyryanka, Northeastern Siberia , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6669, https://doi.org/10.5194/egusphere-egu22-6669, 2022.