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SSP2.4

Polar climate and environmental change throughout geological time

Polar regions are particularly sensitive to climate variability and play a key role in global climate and environmental conditions through various feedback mechanisms. In this session we invite contributions dealing with all aspects of Phanerozoic (i.e. Cambrian to Holocene) geology from high latitude regions: stratigraphy, paleoenvironment, paleoclimate, and modelling

Co-organized by CL1.1
Convener: Madeleine VickersECSECS | Co-convener: Kasia K. Sliwinska
Presentations
| Tue, 24 May, 15:10–16:40 (CEST)
 
Room -2.32/33

Tue, 24 May, 15:10–16:40

Chairpersons: Madeleine Vickers, Jack Longman

15:10–15:14
Deep Time

15:14–15:19
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EGU22-7172
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ECS
Aleksandra Smyrak-Sikora et al.

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.

15:19–15:24
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EGU22-6598
Sergey Rud'ko and Andrey Shatsillo

The paleomagnetic data obtained from the Neoproterozoic rocks stratigraphically related to glacial deposits suggest the ice sheets' near-equatorial occurrence. Based on these data, the Snowball Earth hypothesis proposing the Cryogenian period's total glaciations has been developed and became almost a paradigm. Quaternary glacial successions usually contain varves (seasonally laminated deposits) as they were formed in high latitudes. Therefore, we suggest that varves provide an independent sedimentological test of the paleolatitude position of Precambrian glacial deposits.

We carried out a sedimentological study on thinly laminated rhythmites in the Neoproterozoic glacial deposits in Southern Siberia, and found that they have features characteristic of seasonal varves. The studied rhythmites interstratify the Bolshoi Patom and Nichatka Formations' diamictites at the base of the Dal'nyaya Taiga Group. The seasonality is clearly manifested in the rhythmites of the Nichatka Formation. The rhythmites are represented by interbedding of millimeter-scale siltstones and mudstones with sandy and gravelly admixture. The coarse-sandy and gravelly component is interpreted as ice-rafted clasts, as it has characteristic features of dropstones and contains unconfined till pellets. Ice rafted clasts saturate siltstone laminas and are practically absent in argillite layers.
Thus, argillite laminas can be confidently recognized as deposits of the cold season, during which ice melting and iceberg rafting ceased. On the other hand, siltstone layers with dropstones are deposits of the warmer melting season. The rhythmite's diurnal nature is excluded by its complex structure of the silty layer of the rhythm, which is caused by several sedimentation events separated in time.  The entire set of microfacies of the Nichatka Formation rhythmites reveals similarities with varve microfacies produced by variable flows in ice-contact proglacial lakes. The upper part of the Bolshoi Patom Formation's rhythmites is also formed by varve-like pairs of thin siltstone and mudstone laminas. Dropstones are virtually absent in them, and, therefore, the seasonal nature of the rhythm is less confidently established. The siltstone within the rhythm may have a massive or normally graded texture. The argillite is approximately equal in thickness to the siltstone lamina (about 0.5 mm). The thickness of a pair of siltstone and argillite laminas may remain almost constant when more than 50 pairs are observed. This regularity of laminas thickness in rhythmite is not typical of a tidal setting, but it is difficult to rule out this rhythmite's diurnal nature.  These deposits display high similarity to varves produced by low energy suspension settling during the melt season. The observed seasonal nature of the rhythmites in the glacial deposits of the Dal'nyaya Taiga Group evidence against the validity of the Snowball Earth hypothesis, which assumes the presence of glacial caps near the equator in the Neoproterozoic. The study was supported by RSF Grant No. 20-77-10066.

How to cite: Rud'ko, S. and Shatsillo, A.: Varves versus Snowball: Seasonal rhythmite in the glacial deposits of the Nichatka Formation (South Siberia)., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6598, https://doi.org/10.5194/egusphere-egu22-6598, 2022.

15:24–15:29
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EGU22-11379
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ECS
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Luca Zurli et al.

The Late Paleozoic Ice Age (LPIA) in one of the coldest periods in the Earth history which led to the development of ice covers across the entire Gondwana from Carboniferous to Permian. The LPIA view is changing from a single ice sheet covering the entire Gondwana to a series of small and diachronous ice caps widespread through the supercontinent. Stratigraphic studies and facies analysis are key tools for the evaluation of the paleo-environmental depositional setting and, consequently, of the style of glaciation.

Tasmania is a key region because it was settled between northern Victoria Land (Antarctica) and Australia and the LPIA deposits could help to provide links between the two sectors of Gondwana. Tasmania constituted a sedimentary basin in the late Paleozoic and Mesozoic and thick sedimentary sequence, both marine and terrestrial, known as Parmeener Supergroup, crops out. The lowermost part of the Lower Parmeener Supergroup, consisting in the Wynyard Tillite and its correlative throughout the region, recorded glacial sedimentation linked with ice caps that developed in the region.

Here, we provide a detailed sedimentological analysis of two drillcores which recovered glacial sequences deposited in the Tasman Basin. The cores were placed into two separate sub-basins: the first hole, named Ross 1, is located in the central part of Tasmania and recorded ca. 60m of glaciogenic rocks of the Stockers Tillite; the second, named Cygnet 3, is located in the southern part of the island and recorded ca. 200m of glaciogenic rocks belonging to the Truro Tillite. The centimetric scale sedimentological analyses allow the identification of 14 lithofacies which were grouped into 6 facies association on the basis of depositional genesis. Facies associations vary from possibly sub-glacial or ice contact to ice distal. Deposition is dominated both by gravity and sediment remobilization processes and suspension settling with ice rafted debris accumulation. All of them are indicative of subaqueous deposition, likely glacimarine. Moreover, along the succession the glacial sequence stratigraphy approach was applied and glacial system tracts and bounding surfaces which define glacial sequences were identified. The stacking pattern of the facies associations allow to demonstrate that the glacial sequences record phases of advance and retreat of the glacial front into the basin within the main end of the main glacial phase. The facies associations, mainly interpreted as gravity driven deposits, together with the thin thickness, show that Ross 1 core was located in a basin margin position and that possibly recorded sub-glacial erosion, while Cygnet 3 core, which have greater thickness, shows facies associations mainly related with suspension settling, indicating a more basinal position. Petrographic analysis of the gravel size fraction constituting the diamictite and the ice rafted debris shows difference in the lithological composition of the two formations, sustaining the hypothesis that the sub-basins were fed by different ice caps.

How to cite: Zurli, L., Cornamusini, G., Liberato, G. P., and Conti, P.: Stratigraphy of the Late Paleozoic Ice Age glacial sequences in Tasmania (Australia): implications for the glaciation in southern Gondwana, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11379, https://doi.org/10.5194/egusphere-egu22-11379, 2022.

15:29–15:34
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EGU22-7362
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ECS
Franziska R. Blattmann et al.

The Permian-Triassic mass extinction (PTME) is considered to be the most severe extinction in Earth’s history. Following this extinction, the Early Triassic is known as an interval of divergent biotic recovery patterns, with several periods of unfavorable environmental conditions as suggested by global fluctuations in carbon isotope compositions of both organic and inorganic carbon reservoirs (e.g., Payne et al., 2004; Galfetti et al., 2007). Despite these global carbon isotope excursions, little is known about the evolution of the organic carbon cycle. The aim of this study is to improve our understanding of long-term organic carbon cycle dynamics, in particular the influence of pyrogenic carbon. Initial results for the Smithian and Spathian from sections sampled in Svalbard show an increase of polyaromatic hydrocarbons (PAHs) during the Spathian. Particularly, phenanthrene and anthracene concentrations increase amid the Smithian-Spathian boundary (SSB). These increases coincide with increased d18Ophosphate values (approx. 14 ‰ to 17 ‰) measured for conodonts in the same locality and are suggestive of a rapid cooling at the SSB. Global temperature decline in the late Smithian would decrease corresponding precipitation intensities, particularly in high latitude regions (Goudemand et al. 2019). Decreasing precipitation intensity generates much less runoff that, in turn, is associated with increases in wildfire activity in high latitude regions (Grosse et al. 2011). Increased wildfire activity may have contributed to increased atmospheric pCO2 levels. In contrast, incomplete combustion of organic matter would also form a recalcitrant terrestrial organic carbon pool, which could act as a carbon sink.

How to cite: Blattmann, F. R., Luz, Z. A. S., Vennemann, T., Bucher, H., Schneebeli-Hermann, E., and Magill, C. R.: Early Triassic Cycling of Pyrogenic Carbon in Northern High Latitudes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7362, https://doi.org/10.5194/egusphere-egu22-7362, 2022.

15:34–15:39
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EGU22-7286
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ECS
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Thomas Letulle et al.

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.

15:39–15:42
Into the Cenozoic

15:42–15:47
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EGU22-12640
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ECS
Lauren O'Connor et al.

Latitudinal temperature gradients are a critical component of the climate system and control the transport of heat and moisture. However, this process is poorly understood during past intervals of extreme greenhouse climate, in particular owing to models suggesting that gradients must be much steeper than proxy data imply. Palaeotemperature records Late Cretaceous–Early Paleogene can provide insight into how the global climate system operates under greenhouse conditions.

Much of our understanding of palaeotemperatures and gradients therein during this interval comes from marine sea-surface temperature proxy data, with very few terrestrial records. These palaeoclimate reconstructions are hampered by poor temporal resolution, difficulties in correlating between sites, and limited spatial coverage.

Lipids from fossil peats across North America provide an opportunity to investigate terrestrial palaeotemperatures across the Cretaceous–Paleogene boundary and how these differ across a range of latitudes. Here we present a mean annual air temperature record spanning this interval from the Canadian High Arctic (~75°N palaeolatitude). Our data show that temperatures ranged from 0–18°C, compared with 13–27°C at contemporaneous peat-accumulating sites in Saskatchewan (~60°N palaeolatitude). These data indicate a temperature gradient of approximately 10°C. These values are similar to those modelled for the latest Cretaceous, and the latitudinal difference is comparable to the modern gradient across North America (UCAR), albeit ~20°C warmer.

Our study demonstrates that although the Arctic experienced high terrestrial temperatures, the K-Pg interval saw a well-defined latitudinal temperature gradient. Further, our reconstructions fill an existing gap in the terrestrial record and highlight the value of fossil peats in palaeoclimate studies.

How to cite: O'Connor, L., Jerrett, R., Price, G., van Dongen, B., Crampton-Flood, E., and Lengger, S.: An organic geochemical reconstruction of North American temperature gradients over the Cretaceous-Paleogene boundary, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12640, https://doi.org/10.5194/egusphere-egu22-12640, 2022.

15:47–15:52
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EGU22-12131
Urszula Hara

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.

15:52–15:57
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EGU22-12021
Paul Knutz et al.

Studies based on deep ocean drilling cores points to North-East Greenland as a focal point for ice sheet accumulation incurring much earlier than the Pleistocene Northern Hemisphere glaciation. The build-up of marine-based ice sheets in these parts is critical to the cooling of the Nordic Seas and the Arctic Ocean, considered as a pre-condition for the modern ocean “conveyor belt” circulation. However, proximal sedimentary records that can shed light on the timing and climate background of early Greenland Ice Sheet evolution are lacking. In 2008 a series of shallow cores were drilled by the Kanumas consortium on the NorthEast Greenland shelf and Cenozoic sediments were recovered at several sites. Here we present litho- and palynostratigraphic information, along with new cosmogenic isotope results, of a 110 m long sediment core (Kanumas 13). The core study, supported by regional seismic data, suggests that ice streams may have been active on the North-East Greenland margin since middle-late Miocene. Geochemistry and magnetic susceptibility data indicate that an abrupt change in sediment source occurred at 50.8 m. The shift in provenance is accompanied by a transition to more open marine conditions. The implications for the Greenland Ice Sheet and Artic climate development will be addressed in the presentation.

How to cite: Knutz, P., Nielsen, T., Sliwinska, K., Fyhn, M., Hopper, J., Jennings, A., Bierman, P., Christ, A., Corbett, L., and Hidy, A.: A rare record of late Neogene glaciation from the north east Greenland margin, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12021, https://doi.org/10.5194/egusphere-egu22-12021, 2022.

15:57–16:02
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EGU22-3909
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ECS
Xiaoxia Huang et al.

16:02–16:05
Quaternary

16:05–16:15
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EGU22-10379
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ECS
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solicited
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Highlight
Flor Vermassen et al.

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.

16:15–16:20
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EGU22-11897
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ECS
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Weihan Jia et al.

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.

16:20–16:25
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EGU22-11180
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ECS
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Jeremy Courtin et al.

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.

16:25–16:30
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EGU22-8394
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ECS
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Diana Soloveva et al.

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.

16:30–16:35
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EGU22-12387
Olga Margalef et al.

Palsa mires are a common feature in the Subarctic zone of discontinuous permafrost. In these peatlands, the patchy distribution of frozen soil constrains relief, water regime and vegetation distribution. Because they lie at the edge of permafrost distribution, palsa mires are very sensitive to climate changes and become extremely valuable high-latitude terrestrial records. However, both (1) their origin, including their rapid development towards ombrotrophy because of uplift by ice accretion and (2) the irreversible geochemical effects of collapse and permafrost thaw make them challenging environmental archives. Understanding the Late Holocene evolution of these systems becomes a key framework to decipher potential consequences of the permafrost disappearance observed during the last decades. A 120 cm peat record was recovered on the Storflaket Palsa plateau (Abisko, Sweden, 68ºN) on June 2018.  This register contains more than 9000 years of paleoenvironmental information and was entirely made of peat, with two centimetric layers of volcanic ash interbedded at 74-77 and 46-47cm depth. A multidisciplinary approach using chemical (stoichiometry, stable isotopy and elemental composition) and biological proxies (macrofossil and pollen determination) was used to reconstruct the environmental evolution of the site. Bottom most layers (50-120cm) were characterized by peat made of different types of brown mosses and abundant aquatic fauna indicating that the area was covered by a high and stable water table that promoted organic matter accumulation in a percolation mire system. The very high accumulation rates and the extremely good preservation of macrofossil remains suggest a permafrost free area around 8000 cal yr BP. From 50 to 9 cm the peat is made of highly degraded brown moss, with increasing degradation towards the top. Chemical and macrofossil analyses indicate a strong oxidation processes due to peat exposition. The top layer (9 to 0 cm) is characterized by dry palsa peat and depicts very low accumulation rates, suggesting that this record is capturing the uplift movement of the peat mound by ice accretion and a shift from a minerotrophic and waterlogged mire system towards the development of a palsa plateau. Chemical and biological signals allow us to date the age of permafrost establishment later than 3000 cal. yr BP. The deposition of ash layers is linked to sudden inputs of phosphorus and metals leading to stoichiometric changes in peat composition.

How to cite: Margalef, O., Grau, O., Joosten, H., Pérez Haase, A., Pla Rabes, S., Fernández, P. R., Giralt, S., Sánchez, M., Pérez Obiol, R., Soriano, J. M., Pèlachs, A., Campderrós, S., Fernández Alarcón, C., and Peñuelas, J.: Late Holocene permafrost development triggers hydrological and geochemical changes in subarctic peatlands (Abisko, 68ºN), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12387, https://doi.org/10.5194/egusphere-egu22-12387, 2022.

16:35–16:40
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EGU22-6669
Nayeon Ko et al.

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.