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Vermassen, F., O'Regan, M., de Boer, A. M., Schenk, F., Razmjooei, M. J., West, G., . . . Coxall, H. (2023). A seasonally ice-free Arctic Ocean during the Last Interglacial. Nature Geoscience, 16(8), 723-729
Open this publication in new window or tab >>A seasonally ice-free Arctic Ocean during the Last Interglacial
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2023 (English)In: Nature Geoscience, ISSN 1752-0894, E-ISSN 1752-0908, Vol. 16, no 8, p. 723-729Article in journal (Refereed) Published
Abstract [en]

The extent and seasonality of Arctic sea ice during the Last Interglacial (129,000 to 115,000 years before present) is poorly known. Sediment-based reconstructions have suggested extensive ice cover in summer, while climate model outputs indicate year-round conditions in the Arctic Ocean ranging from ice free to fully ice covered. Here we use microfossil records from across the central Arctic Ocean to show that sea-ice extent was substantially reduced and summers were probably ice free. The evidence comes from high abundances of the subpolar planktic foraminifera Turborotalita quinqueloba in five newly analysed cores. The northern occurrence of this species is incompatible with perennial sea ice, which would be associated with a thick, low-salinity surface water. Instead, T. quinqueloba's ecological preference implies largely ice-free surface waters with seasonally elevated levels of primary productivity. In the modern ocean, this species thrives in the Fram Strait-Barents Sea 'Arctic-Atlantic gateway' region, implying that the necessary Atlantic Ocean-sourced water masses shoaled towards the surface during the Last Interglacial. This process reflects the ongoing Atlantification of the Arctic Ocean, currently restricted to the Eurasian Basin. Our results establish the Last Interglacial as a prime analogue for studying a seasonally ice-free Arctic Ocean, expected to occur this century. The warm Last Interglacial led to a seasonally ice-free Arctic Ocean and a transformation to Atlantic conditions, according to planktic foraminifera records from central Arctic Ocean sediment cores.

National Category
Geology
Identifiers
urn:nbn:se:su:diva-220914 (URN)10.1038/s41561-023-01227-X (DOI)001045179900008 ()2-s2.0-85166643282 (Scopus ID)
Available from: 2023-09-18 Created: 2023-09-18 Last updated: 2023-09-18Bibliographically approved
Muchowski, J., Arneborg, L., Umlauf, L., Holtermann, P., Eisbrenner, E., Humborg, C., . . . Stranne, C. (2023). Diapycnal Mixing Induced by Rough Small-Scale Bathymetry. Geophysical Research Letters, 50(13), Article ID e2023GL103514.
Open this publication in new window or tab >>Diapycnal Mixing Induced by Rough Small-Scale Bathymetry
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2023 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 50, no 13, article id e2023GL103514Article in journal (Refereed) Published
Abstract [en]

Diapycnal mixing impacts vertical transport rates of salt, heat, and other dissolved substances, essential for the overturning circulation and ecosystem functioning in marine systems. While most studies have focused on mixing induced by individual obstacles in tidal flows, we investigate the net effect of non-tidal flow over multiple small-scale (<1 km) bathymetric features penetrating a strongly-stratified density interface in a coastal region. We combine high-resolution broadband acoustic observations of turbulence microstructure with traditional shear microstructure profiling, to resolve the variability and intermittency of stratified turbulence related to the rough bathymetry. Scale analysis and acoustic imaging suggest that underlying mixing mechanisms are related to topographic wake eddies and breaking internal waves. Depth averaged dissipation rates (1.1 × 10−7 Wkg−1) and turbulent vertical diffusivities (7 × 10−4 m2s−1) in the halocline exceed reference values by two orders of magnitude. Our study emphasizes the importance of rough small-scale bathymetric features for the vertical transport of salt in coastal areas.

Keywords
diapycnal mixing, rough small-scale bathymetry, stratified flow over obstacles, broadband acoustic observations of turbulent mixing, microstructure profiler turbulence measurements, mixing across halocline
National Category
Oceanography, Hydrology and Water Resources
Identifiers
urn:nbn:se:su:diva-220982 (URN)10.1029/2023GL103514 (DOI)001022454400001 ()2-s2.0-85165469615 (Scopus ID)
Available from: 2023-09-13 Created: 2023-09-13 Last updated: 2023-09-13Bibliographically approved
Nilsson, J., van Dongen, E., Jakobsson, M., O'Regan, M. & Stranne, C. (2023). Hydraulic suppression of basal glacier melt in sill fjords. The Cryosphere, 17(6), 2455-2476
Open this publication in new window or tab >>Hydraulic suppression of basal glacier melt in sill fjords
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2023 (English)In: The Cryosphere, ISSN 1994-0416, E-ISSN 1994-0424, Vol. 17, no 6, p. 2455-2476Article in journal (Refereed) Published
Abstract [en]

Using a conceptual model, we examine how hydraulically controlled exchange flows in silled fjords affect the relationship between the basal glacier melt and the features of warm intermediate Atlantic Water (AW) outside the fjords. We show that an exchange flow can be forced to transit into the hydraulic regime if the AW interface height decreases, the AW temperature increases, or the production of glacially modified water is boosted by subglacial discharge. In the hydraulic regime, the heat transport across the sill becomes a rate-limiting factor for the basal melt, which is suppressed. An interplay between processes near the ice-ocean boundary and the hydraulically controlled exchange flow determines the melt dynamics, and the sensitivity of the basal melt to changes in the AW temperature is reduced. The model results are discussed in relation to observations from the Petermann, Ryder, and 79 N glaciers in northern Greenland.

National Category
Climate Research
Identifiers
urn:nbn:se:su:diva-220915 (URN)10.5194/tc-17-2455-2023 (DOI)001017677700001 ()2-s2.0-85164498950 (Scopus ID)
Available from: 2023-09-18 Created: 2023-09-18 Last updated: 2023-09-18Bibliographically approved
Razmjooei, M. J., Henderiks, J., Coxall, H., Baumann, K.-H., Vermassen, F., Jakobsson, M., . . . O'Regan, M. (2023). Revision of the Quaternary calcareous nannofossil biochronology of Arctic Ocean sediments. Quaternary Science Reviews, 321, Article ID 108382.
Open this publication in new window or tab >>Revision of the Quaternary calcareous nannofossil biochronology of Arctic Ocean sediments
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2023 (English)In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 321, article id 108382Article in journal (Refereed) Published
Abstract [en]

Despite extensive chronological studies, the relationship between the age and sub-seafloor depth of Arctic Ocean sediments remains ambiguous. This prevents confident identification of paleoceanographic changes in the Arctic during the Quaternary. Currently, age-depth models derived from uranium-series decay in Arctic sediments diverge by hundreds of thousands of years compared to those built on known evolutionary appearances and extinctions of calcareous nannoplankton, a group of globally valuable age-markers. Here we report on highresolution biostratigraphic analysis of late Quaternary sediments in six cores from the central Arctic Ocean (CAO). We applied paired light microscope (LM) and scanning electron microscope (SEM) imaging to improve nannofossil diagnosis. We argue that low abundances and poor preservation have led to misidentification of the true stratigraphic depth of the critical Pleistocene nannofossil bio-events that have underpinned age models for many Arctic sedimentary records for decades. The revised calcareous nannofossil biochronology provides a radically different geochronological framework for CAO sediments - indicating that what had previously been identified as Marine Isotope Stage (MIS) 7 (191-243 ka) in many sedimentary records is older than MIS 12 (424-478 ka). Furthermore, it suggests that previously inferred sub-stages of MIS 5 could represent full interglacial periods rather than interstadials. The results help reconcile the different dating approaches and provide a transformative step towards resolving the disparity in Quaternary Arctic age-depth models, bringing us one step closer to accurate paleoceanographic reconstructions based on sediment cores.

Keywords
Quaternary, Biostratigraphy, Nannoplankton, Arctic ocean, Age-model
National Category
Geology
Identifiers
urn:nbn:se:su:diva-224659 (URN)10.1016/j.quascirev.2023.108382 (DOI)001111425000001 ()2-s2.0-85176271088 (Scopus ID)
Available from: 2023-12-19 Created: 2023-12-19 Last updated: 2023-12-19Bibliographically approved
Detlef, H., O'Regan, M., Stranne, C., Mørk Jensen, M., Glasius, M., Cronin, T. M., . . . Pearce, C. (2023). Seasonal sea-ice in the Arctic's last ice area during the Early Holocene. Communications Earth & Environment, 4(1), Article ID 86.
Open this publication in new window or tab >>Seasonal sea-ice in the Arctic's last ice area during the Early Holocene
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2023 (English)In: Communications Earth & Environment, E-ISSN 2662-4435, Vol. 4, no 1, article id 86Article in journal (Refereed) Published
Abstract [en]

According to climate models, the Lincoln Sea, bordering northern Greenland and Canada, will be the final stronghold of perennial Arctic sea-ice in a warming climate. However, recent observations of prolonged periods of open water raise concerns regarding its long-term stability. Modelling studies suggest a transition from perennial to seasonal sea-ice during the Early Holocene, a period of elevated global temperatures around 10,000 years ago. Here we show marine proxy evidence for the disappearance of perennial sea-ice in the southern Lincoln Sea during the Early Holocene, which suggests a widespread transition to seasonal sea-ice in the Arctic Ocean. Seasonal sea-ice conditions were tightly coupled to regional atmospheric temperatures. In light of anthropogenic warming and Arctic amplification our results suggest an imminent transition to seasonal sea-ice in the southern Lincoln Sea, even if the global temperature rise is kept below a threshold of 2 °C compared to pre-industrial (1850–1900).

National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-216437 (URN)10.1038/s43247-023-00720-w (DOI)000953861000001 ()2-s2.0-85150922576 (Scopus ID)
Available from: 2023-05-05 Created: 2023-05-05 Last updated: 2023-05-05Bibliographically approved
Sicard, M., de Boer, A. M., Coxall, H., Koenigk, T., Karami, M. P., Jakobsson, M. & O'Regan, M. (2023). Similarities and Differences in Arctic Sea-Ice Loss During the Solar-Forced Last Interglacial Warming (127 Kyr BP) and CO2-Forced Future Warming. Geophysical Research Letters, 50(24), Article ID e2023GL104782.
Open this publication in new window or tab >>Similarities and Differences in Arctic Sea-Ice Loss During the Solar-Forced Last Interglacial Warming (127 Kyr BP) and CO2-Forced Future Warming
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2023 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 50, no 24, article id e2023GL104782Article in journal (Refereed) Published
Abstract [en]

Based on a 7-member global circulation model ensemble from CMIP6/PMIP4, we compare the regional distribution of Arctic sea ice between a simulation representing the Last Interglacial (LIG) climate, with solar-forced warming, and an idealized future CO2-forced simulation with a similar annual sea-ice volume. The two simulations feature small but robust differences in the Central Arctic and Baffin Bay during summer, and larger differences at the sea-ice margins in the sub-Arctic Atlantic and North Pacific sectors during winter. Our results indicate that, under both forcings, sea ice persists north of Greenland until late summer, suggesting that the assumption that this region is the Last Ice Area is robust and holds for other climate states. However, we show that processes influencing sea-ice distribution in winter, such as Atlantification and sea-ice drift, differ and need to be further investigated.

National Category
Oceanography, Hydrology and Water Resources
Identifiers
urn:nbn:se:su:diva-225434 (URN)10.1029/2023GL104782 (DOI)001123913100001 ()2-s2.0-85179357499 (Scopus ID)
Available from: 2024-01-17 Created: 2024-01-17 Last updated: 2024-01-17Bibliographically approved
Nikiforov, S., Ananiev, R., Jakobsson, M., Moroz, E., Sokolov, S., Sorokhtin, N., . . . Semiletov, I. (2023). The Extent of Glaciation in the Pechora Sea, Eurasian Arctic, Based on Submarine Glacial Landforms. Geosciences, 13(2), Article ID 53.
Open this publication in new window or tab >>The Extent of Glaciation in the Pechora Sea, Eurasian Arctic, Based on Submarine Glacial Landforms
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2023 (English)In: Geosciences, E-ISSN 2076-3263, Vol. 13, no 2, article id 53Article in journal (Refereed) Published
Abstract [en]

The Pechora Sea is optimally located for studying the coalescence of a glacial and periglacial continental shelf zone in the high Arctic. Here, we present data acquired during cruises of the RV Akademik Nikolaj Strakhov in 2018–2021, revealing the distribution of submarine glacial landforms in the central part of the Pechora shelf area. Based on moraines and the distribution of glacial lineations, the extent of the ice sheet during the Last Glacial Maximum (LGM) is proposed. The crests of the moraine ridges and the slopes of their sides express a variation in morphology, and the ridges combine into irregular complexes. The moraines are primarily composed of coarse cobble-sized material with an addition of coarse sand and other sedimentary fractions. The mapped glacial landforms clearly indicate that an ice sheet extended over the area, while the Pechora basin, at the same time, was comprised of lowland characterized by a cryogenic subaerial landscape. Based on the result from this study, the extent and ice-flow pattern of the Barents-Kara Ice Sheet during the LGM were determined.

Keywords
glacial landforms, moraines, ice sheet, arctic shelf, glacial lineations
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-216008 (URN)10.3390/geosciences13020053 (DOI)000939031000001 ()2-s2.0-85148762651 (Scopus ID)
Available from: 2023-03-31 Created: 2023-03-31 Last updated: 2023-03-31Bibliographically approved
Stranne, C., O'Regan, M., Hong, W.-L., Brüchert, V., Ketzer, M., Thornton, B. F. & Jakobsson, M. (2022). Anaerobic oxidation has a minor effect on mitigating seafloor methane emissions from gas hydrate dissociation. Communications Earth & Environment, 3(1), Article ID 163.
Open this publication in new window or tab >>Anaerobic oxidation has a minor effect on mitigating seafloor methane emissions from gas hydrate dissociation
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2022 (English)In: Communications Earth & Environment, E-ISSN 2662-4435, Vol. 3, no 1, article id 163Article in journal (Refereed) Published
Abstract [en]

Continental margin sediments contain large reservoirs of methane stored as gas hydrate. Ocean warming will partly destabilize these reservoirs which may lead to the release of substantial, yet unconstrained, amounts of methane. Anaerobic oxidation of methane is the dominant biogeochemical process to reduce methane flux, estimated to consume 90% of the methane produced in marine sediments today. This process is however neglected in the current projections of seafloor methane release from gas hydrate dissociation. Here, we introduce a fully coupled oxidation module to a hydraulic-thermodynamic-geomechanical hydrate model. Our results show that for seafloor warming rates > 1 degrees C century(-1), the efficiency of anaerobic oxidation of methane in low permeability sediments is poor, reducing the seafloor methane emissions by <5%. The results imply an extremely low mitigating effect of anaerobic oxidation of methane on climate warming-induced seafloor methane emissions. Microbial anaerobic oxidation of methane may not substantially mitigate projected warming-induced emissions of methane from marine hydrate-bearing sediments, according to a coupled hydraulic-thermodynamic-geomechanical hydrate model.

National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-208481 (URN)10.1038/s43247-022-00490-x (DOI)000832709800001 ()2-s2.0-85135059488 (Scopus ID)
Available from: 2022-09-01 Created: 2022-09-01 Last updated: 2022-09-01Bibliographically approved
Glueder, A., Mix, A. C., Milne, G. A., Reilly, B. T., Clark, J., Jakobsson, M., . . . McKay, J. L. (2022). Calibrated relative sea levels constrain isostatic adjustment and ice history in northwest Greenland. Quaternary Science Reviews, 293, Article ID 107700.
Open this publication in new window or tab >>Calibrated relative sea levels constrain isostatic adjustment and ice history in northwest Greenland
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2022 (English)In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 293, article id 107700Article in journal (Refereed) Published
Abstract [en]

Relative Sea Levels (RSLs) derived primarily from marine bivalves near Petermann Glacier, NW Greenland, constrain past regional ice-mass changes through glacial isostatic adjustment (GIA) modeling. Oxygen isotopes measured on bivalves corrected for shell-depth habitat and document changing meltwater input. Rapid RSL fall of up to 62 m/kyr indicates ice loss at or prior to ∼9 ka. Transition to an RSL stillstand starting at ∼6 ka reflects renewed ice-mass loading followed by further mass loss over the past few millennia. GIA simulations of rapid early RSL fall suggest a low regional upper-mantle viscosity. Early loss of grounded ice tracks atmospheric warming and pre-dates the eventual collapse of Petermann Glacier's floating ice tongue near ∼7 ka, suggesting grounding zone stabilization during early phases of deglaciation. We hypothesize mid-Holocene regrowth of regional ice caps in response to cooling and increased precipitation, following loss of the floating shelf ice. Remnants of these ice caps remain present but are now melting.

Keywords
Relative sea-level, Glacio-isostatic adjustment, Bivalves, Petermann glacier, Holocene thermal maximum, Sea level index points
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-210687 (URN)10.1016/j.quascirev.2022.107700 (DOI)000860292000004 ()
Available from: 2022-11-09 Created: 2022-11-09 Last updated: 2022-11-09Bibliographically approved
Möller, P., Björck, S., Dowling, T. P. F., Hammarlund, D., Jakobsson, M., Ljung, K., . . . Paradeisis-Stathis, S. (2022). Deglaciation history and subsequent lake dynamics in the Siljan region, south-central Sweden, based on new LiDAR evidence and sediment records. Earth Surface Processes and Landforms, 47(15), 3515-3545
Open this publication in new window or tab >>Deglaciation history and subsequent lake dynamics in the Siljan region, south-central Sweden, based on new LiDAR evidence and sediment records
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2022 (English)In: Earth Surface Processes and Landforms, ISSN 0197-9337, E-ISSN 1096-9837, Vol. 47, no 15, p. 3515-3545Article in journal (Refereed) Published
Abstract [en]

The Siljan region hosts Europe's largest impact structure. The high-relief landscape, with a central granite dome bordered by lake basins, contains an array of glacial and shore-level landforms. We investigated its deglaciation history by mapping and analysing landforms on high resolution LiDAR (light detection and ranging)-based digital surface models coupled with well-dated sediment successions from peat and lake sediment cores. The granite dome and bordering areas are characterized by streamlined terrain and ribbed moraine with a streamlined overprint. These suggest an ice-flow direction from north-northwest (NNW) with wet-based thermal conditions prior to deglaciation. During its retreat, the ice sheet was split into thinner plateau ice and thicker basin ice. Sets of low-gradient glaciofluvial erosion channels suggest intense ice-lateral meltwater drainage across gradually ice-freed slopes, while ‘down-the-slope’ erosion channels and eskers show meltwater drainage from stagnated plateau ice. Thick basin ice receded with a subaqueous margin across the deep Siljan–Orsasjön Basin c. 10,700–10,500 cal. bp. During ice recession the ingression of the Baltic Ancylus Lake led to diachronous formation of highest shoreline marks, from ~207 m in the south to ~220 m above sea level (a.s.l.) in the north. Differential uplift resulted in shallowing of the water body, which led to the isolation of the Siljan–Orsasjön Basin from the Baltic Basin at c. 9800 cal. bp. The post-isolation water body – the ‘Ancient Lake Siljan’ – was drained through the ancient Åkerö Channel with a water level at 168–169 m a.s.l. during c. 1000 years. A later rerouting of the outlet to the present course was initiated at c. 8800 cal. bp, which led to a lake-level lowering of 6–7 m to today's level of Lake Siljan (~162 m a.s.l.). This study shows the strength of an integrated methodological approach for deciphering the evolution of a complex landscape, combining highly resolved geomorphological analysis with well-dated sediment successions. 

Keywords
Baltic Basin, Dalarna, digital terrain models, drainage rerouting, glacial geomorphology, glaciofluvial deposits, glacio-isostatic rebound, ice sheet recession, ice-dammed lake, lake bathymetry, lake isolation, LiDAR, ribbed moraine, shoreline displacement, streamlined terrain
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-210674 (URN)10.1002/esp.5471 (DOI)000861741900001 ()2-s2.0-85138985081 (Scopus ID)
Available from: 2022-11-23 Created: 2022-11-23 Last updated: 2023-01-11Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-9033-3559

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