Svalbard Barents Sea Research Articles

Weichselian–Holocene glacial history of the Sjuøyane archipelago, northern Svalbard

The Sjuøyane archipelago is the northernmost land area of Svalbard; thus, it provides a window to study the terrestrial glacial history and dynamics of the Svalbard–Barents Sea Ice Sheet and complement marine geological studies in the region. To reconstruct the glacial history of Sjuøyane, we describe coastal sedimentary sections in Quaternary sediments and constrain their chronology by radiocarbon and optically stimulated luminescence ages. Erratic boulders and bedrock are sampled for 10Be cosmogenic exposure dating, aiming to determine the deglaciation age and exposure history. Holocene environments are studied based on lake sediments and emerging vegetation from retreating snow patches. The sedimentary sections largely consist of shallow (glacio‐)marine and/or littoral sediments deposited during high relative sea levels. The radiocarbon and luminescence ages suggest they formed during a Middle Weichselian interstadial and after the Late Weichselian glaciation. A wave‐washed bedrock erosional notch and rounded boulders at 36±1 m a.h.t. most likely formed during this interstadial. Most of the cosmogenic 10Be ages are older than the last deglaciation, likely indicating a complex exposure history. One boulder sample suggests that the lowlands were deglaciated 14.7±1.82 ka ago, and two boulder samples with ages of 18.94±3.26 and 22.89±4.05 ka suggest that the highlands were possibly ice‐free at this time. The lake sediments from Isvatnet, Phippsøya, consist of glaciolacustrine silt and clay overlain by gyttja. The gyttja has accumulated at least since 7.0 cal. ka BP. Two radiocarbon ages from emerging vegetation suggest Neoglacial cooling since 3.8 cal. ka BP. A patchy glacial drift at the surface of Sjuøyane and well‐preserved pre‐Late Weichselian sediments suggest that the Late Weichselian glaciation was non‐erosive and/or cold‐based at this part of the north margin of the Svalbard–Barents Sea Ice Sheet.

Eurasian Arctic Rifted Margin Composite Tectono-Sedimentary Element

The Eurasian Arctic Rifted Margin (EARM) spans a poorly studied transition region between the Eurasian continental shelf and the deep-water Nansen Basin. It is a conjugate margin to the Lomonosov Ridge, as both domains were united before the opening of the oceanic Eurasia Basin. The EARM is considered as a Composite Tectono-Sedimentary Element (CTSE) consisting of two individual tectono-sedimentary elements (TSEs): (1) an undefined group of poorly known pre-rift Mesozoic and Paleozoic sedimentary successions; and (2) Late Cretaceous–Paleocene synrift strata. The latter are bounded by a c. 56 Ma break-up unconformity and are overlain by the Eurasia Basin prograded margin TSE, which is not included in EARM. In the absence of drilled wells, we utilize multichannel seismic reflection (MCS) data for seismic stratigraphic correlations with nearby, better-explored, areas. The EARM CTSE is subdivided into three along-strike segments (from west to east): Svalbard–Barents Sea, the North Kara Sea and the Taimyr–Laptev Sea. Across-strike, the EARM CTSE is composed of a proximal zone of stretched crust characterized by normal faulting and a relatively narrow distal transition zone that may contain unroofed serpentinized mantle. The lack of drilled wells makes it challenging to evaluate the petroleum potential of the CTSE, although some indications of a working petroleum system presence exist.

Persistence of Holocene ice cap in northeast Svalbard aided by glacio-isostatic rebound

The deglaciation of the Svalbard-Barents Sea Ice Sheet was driven by relative sea-level rise, the incursion of North Atlantic waters around Spitsbergen, and increasing summer insolation. However, ice retreat was interrupted by asynchronous re-advances that occurred into high relative seas, during a period associated with warm regional waters and elevated summer temperatures. Better understanding of this complex style of deglaciation and the dynamic response to a warming climate can serve as an important analogue for modern warming and today's ice sheets. We present evidence from northern Svalbard of glacier re-advances during the Late Glacial-Early Holocene in hand with relative sea-level history and the occurrence of thermophilous molluscs. We argue that glacio-isostatic adjustment during the transition into the Holocene influenced ice marginal dynamics and as a result, the southern region of the Åsgardfonna ice cap persisted through the Holocene Thermal Maximum.

CAGE21-3 Cruise Report: Ocean bottom seismics and acoustic surveys on the West-Svalbard margin – a study of local seismicity and its effect on methane seepage

Cruise CAGE21-3 with UiT’s research vessel R/V Helmer Hanssen was carried out to address the following objectives within the SEAMSTRESS project (Tectonic stress effects on Arctic methane seepage):1- Recovery of 10 Ocean Bottom Seismometers (OBS) deployed last year north of the Knipovich Ridge-Molloy Transform Fault corner (see report CAGE20-5).2- Conduction of an active source OBS experiment for the study of shear waves propagation in relation to local stress field and focused fluid flow.3- Acquisition of seismic lines for completing a side survey for the FRAME-IODP proposal.In 2020, 10 ocean-bottom seismometers (OBS) were deployed at the northern termination of the Knipovich Ridge to monitor seismic activity. The aim is to detect regional and local earthquakes. If localearthquakes are captured we will investigate the stress field in the region and how faults and fluids react to such stress (Figure 1). From the 10 instruments 8 are from Awi and 2 from UiT. IODP proposal 985 Eastern Fram Strait Palaeo-archive (FRAME) proposed to drill five sites on the western Svalbard margin in order to study chronostratigraphy, palaeoceanography, the palaeoclimatic evolution, and the forcing mechanisms responsible for main climatic transitions and the dynamics of the Svalbard Barents Sea Ice Sheet complex. This cruise acquired additional site survey seismic data for proposed primary and alternate drill sites. The cruise may be known as: CAGE21_3

Chemosynthetic and photosynthetic trophic support from cold seeps in Arctic benthic communities

Benthic communities below the photic zone are largely reliant on the export of surface-water primary production and the flux of partially degraded organic matter to the seabed, i.e. pelagic−benthic coupling. Over the past decades, however, the role of chemosynthetically produced carbon in food webs has been recognized in various habitats. Cold seeps are now known to be widespread across circumpolar Arctic shelves where natural release of hydrocarbons occurs at the seabed. Here, we investigated to what extent chemosynthesis-based carbon (CBC) enters the food web in a high latitude shelf-system. Specifically, we estimated the contributions of chemosynthesis-based carbon to primarily benthic invertebrate taxa from seeps at both shallow and deeper shelves and comparative non-seep areas in the Svalbard-Barents Sea region using bulk stable isotope-analysis of carbon and nitrogen. Our results show low δ13C values (-51.3 to -32.7 ‰) in chemosymbiotic siboglinids and several species of benthic, higher-trophic level, invertebrates (mainly polychaetes and echinoderms; -35.0 to -26.1‰) collected at cold seeps, consistent with assimilation of chemosynthesis-based carbon into the Arctic benthic food web. Using a two-component mixing equation, we demonstrate that certain species could derive more than 50% of their carbon from chemosynthesis-based carbon. These findings show that autochthonous chemosynthetic energy sources can contribute to supporting distinct groups of ‘background’ benthic taxa at these Arctic seep-habitats beyond microbial associations and chemosymbiotic species. Furthermore, we found a higher degree of chemosynthesis-based carbon in benthos at the deeper Barents Sea shelf seeps (>330 m) compared to seeps at the Western Svalbard shelf (<150 m water-depth), and we suggest this result reflects the differences in depth range, surface production and pelagic-benthic coupling. We detected large intra-species variations in carbon signatures within and across geographical locations and, combined with isotopic niche-analysis, our results show that certain taxa that inhabits seeps, have wider trophic niches in comparison to taxa inhabiting non-seeps. The increasing number of discovered natural seeps in the Arctic suggests that chemosynthetic production from seeps could play a more critical role in Arctic trophic structure than previously thought. Seep-derived carbon should, hence, be accounted for as an additional carbon source and included in food-web and energy-flow models in future work.

High genomic diversity in the endangered East Greenland Svalbard Barents Sea stock of bowhead whales (Balaena mysticetus)

The East Greenland-Svalbard-Barents Sea (EGSB) bowhead whale stock (Balaena mysticetus) was hunted to near extinction and remains Endangered on the International Union of Conservation of Nature Red List. The intense, temporally extensive hunting pressure may have left the population vulnerable to other perturbations, such as environmental change. However, the lack of genomic baseline data renders it difficult to evaluate the impacts of various potential stressors on this stock. Twelve EGSB bowhead whales sampled in 2017/2018 were re-sequenced and mapped to a previously published draft genome. All individuals were unrelated and void of significant signs of inbreeding, with similar observed and expected homo- and heterozygosity levels. Despite the small population size, mean autosome-wide heterozygosity was 0.00102, which is higher than that of most mammals for which comparable estimates are calculated using the same parameters, and three times higher than a conspecific individual from the Eastern-Canada-West-Greenland bowhead whale stock. Demographic history analyses indicated a continual decrease of Ne from ca. 1.5 million to ca. 250,000 years ago, followed by a slight increase until ca. 100,000 years ago, followed by a rapid decrease in Ne between 50,000 and 10,000 years ago. These estimates are lower than previously suggested based on mitochondrial DNA, but suggested demographic patterns over time are similar.

An updated Weichselian chronostratigraphic framework of the Kongsfjorden Trough Mouth Fan and its implications for the glacial history of Svalbard

The Arctic is a climate‐sensitive area, responding rapidly to present changes, but for the past changes, the record is still incomplete. For instance, the Weichselian glacial history of the Svalbard–Barents Sea Ice Sheet (SBIS) has largely been reconstructed based on studies of the fragmentary Spitsbergen terrestrial and shelf records. However, the sediments removed from the land and shelf areas during peak glacials were deposited on trough mouth fans located along the continental slope. By studying the stratigraphy and processes of the trough mouth fans, comprising a more complete sediment archive, our new data have allowed gaps in the Weichselian glacial history of the SBIS to be refined and filled. Here we present new lithological and geochronological data from the Kongsfjorden Trough Mouth Fan, closely linked to the advance and decay of the SBIS. High‐resolution TOPAS seismic profiles reveal three distinct packages of glacigenic debris flows (GDFs) within its upper stratigraphy, each interpreted to represent an advance of the SBIS to the shelf edge. A radiocarbon dated, 12.6‐m‐long core from the southern flank of the Kongsfjorden Trough Mouth Fan penetrates trough sediments directly linked to the youngest GDF package and terminates in the second GDF, allowing us to study the last two Kongsfjorden ice‐stream advances in greater detail than was previously possible. The age model of core GS10‐164‐09PC, based on combining 14C‐, 18O‐stable isotope and magnetic susceptibility data, spans the last ~54 ka. An Early Weichselian glacial advance is tentatively dated to have ended at ~90 ka. A second peak glaciation is estimated at ~70 ka, followed by a deglaciation from ~54 ka. An ice rafted debris‐rich unit (U7) dated between 38 and 34 ka, followed by a plumite (U6), indicates an advance of unknown extent. The Last Glacial Maximum advance is dated to before 24 ka BP, followed by a rapid deglaciation at ~15 ka. The presence of coarser‐grained sorted sediments at the present seafloor is attributed to the influence of the West‐Spitsbergen Current, acting on water depths of at least 846 m, and is thought to have worked in the vicinity of the coring site since ~14 ka BP.

Deglacial bottom water warming intensified Arctic methane seepage in the NW Barents Sea

Changes in the Arctic climate-ocean system can rapidly impact carbon cycling and cryosphere. Methane release from the seafloor has been widespread in the Barents Sea since the last deglaciation, being closely linked to changes in pressure and bottom water temperature. Here, we present a post-glacial bottom water temperature record (18,000–0 years before present) based on Mg/Ca in benthic foraminifera from an area where methane seepage occurs and proximal to a former Arctic ice-sheet grounding zone. Coupled ice sheet-hydrate stability modeling shows that phases of extreme bottom water temperature up to 6 °C and associated with inflow of Atlantic Water repeatedly destabilized subsurface hydrates facilitating the release of greenhouse gasses from the seabed. Furthermore, these warming events played an important role in triggering multiple collapses of the marine-based Svalbard-Barents Sea Ice Sheet. Future warming of the Atlantic Water could lead to widespread disappearance of gas hydrates and melting of the remaining marine-terminating glaciers.

A Continuous Seismostratigraphic Framework for the Western Svalbard-Barents Sea Margin Over the Last 2.7 Ma: Implications for the Late Cenozoic Glacial History of the Svalbard-Barents Sea Ice Sheet

Here we present a high-resolution, continuous seismostratigraphic framework that for the first time, connects the over 1,000 km long western Svalbard-Barents Sea margin and covers the last ∼2.7 million years (Ma). By exploiting recent improvements in chronology, we establish a set of reliable age fix-points from available boreholes along the margin. We then use a large 2-D seismic database to extend this consistent chronology from the Yermak Plateau and offshore western Svalbard, southwards to the Bear Island Trough-Mouth Fan. Based on this new stratigraphic framework we divide the seismic stratigraphy along the continental margin into three seismic units, and 12 regionally correlated seismic reflections, each with an estimated age assignment. We demonstrate one potential application of this framework by reconstructing the Svalbard-Barents Sea Ice Sheet evolution from the intensification of the northern hemisphere glaciation at ∼2.7 Ma to the Weichselian glaciations. Through seismic facies distribution and sedimentation rate fluctuations along the margin we distinguish three phases of glacial development. The higher temporal resolution provided by this new framework, allows us to document a clear two-step onset to glacial intensification in the region during phase 1, between ∼2.7 and 1.5 Ma. The initial step, between ∼2.7 and 2.58 Ma shows glacial expansion across Svalbard. The first indication of shelf-edge glaciation is on the Sjubrebanken Trough-Mouth Fan, northwestern Barents Sea after ∼2.58 Ma; whilst the second step, between ∼1.95 and 1.78 Ma shows glacial advances beyond Svalbard to the northwestern Barents Sea. Phase 2 is characterized by variations in sedimentation rates and the seismic facies are indicative for a regional glacial intensification for the whole Barents Sea-Svalbard region with widespread shelf-edge glaciations recorded at around ∼1.5 Ma. During Phase 3, the western Barents Sea margin is characterized by a dramatic increase in sedimentation rates, inferring once again a regional glacial intensification. Our new stratigraphic framework allows for the first time differentiation of the sediments deposited on the slope during Early Saalian (∼0.4 and 0.2 Ma), Late Saalian (∼0.2 and 0.13 Ma), and Weichselian (<∼0.123 Ma) periods, providing new insights into the Barents Sea glaciations over the last ∼0.42 Ma.

Glacial and environmental changes in northern Svalbard over the last 16.3 ka inferred from neodymium isotopes

The reconstruction of past ice sheet extents and dynamics in polar regions is essential for understanding the global climate system and obtaining more reliable predictions of future climate change. Here, we present a multi-proxy dataset integrating the Nd isotopic compositions (ε Nd ) of paired detrital and authigenic Fe oxide fractions, grain size distributions, organic geochemistry, and mineral assemblages in a glacimarine sediment core (core HH17–1085-GC) retrieved from the continental shelf off northern Svalbard. Our results indicate variability in sediment provenance and chemical weathering patterns since the last deglaciation, allowing us to distinguish a succession of distinct paleoclimate events: 1) a general retreat of the Svalbard-Barents Sea Ice Sheet (SBIS) from the continental shelf before ca. 16.3 ka BP; 2) an intense episode of meltwater discharge related to massive glacier loss between ca. 12.1–9.9 ka BP; and 3) a period of reduced meltwater input between ca. 9.9 and 2.7 ka BP followed by 4) a phase of glacier re-advance over the last two millennia. Evidence for the prolonged supply of radiogenic detrital ε Nd and dolomite at the site of core HH17–1085-GC indicates that the onset of deglaciation offshore northeastern Svalbard may have occurred at least 1 ka later than that at the northwestern shelf, which can be further evaluated by obtaining a more precise end-member determination for the northeastern source with a quantitative ε Nd dataset from Nordaustlandet. In the context where both polar sea-ice and oceanic circulation are expected to have played minor roles in determining the sedimentary ε Nd compositions, the evidence for pronounced Nd isotopic decoupling between paired authigenic and detrital signatures (Δε Nd ) at ca. 15.2 and 14.1 ka BP is interpreted as reflecting chemical weathering changes following the retreat of the SBIS on northern Svalbard, probably corresponding to punctual episodes of glacial re-advances. Our findings provide a better understanding of the deglacial history of northern Svalbard during and after the last deglaciation and highlight the utility of Nd isotopes as a proxy for reconstructing paleo-cryosphere changes. • Ice recession from the continental shelf off northern Svalbard began before 16.3 ka BP. • Deglaciation of NE Svalbard may have started ~1 ka later than NW Svalbard. • Ice recession on N. Svalbard was punctuated by glacier re-advances at 15.2 and 14.1 ka BP. • Influence of the Arctic sea-ice and oceanic inflow on ε Nd in N. Svalbard was likely minor. • Δε Nd can be a useful tracer to reconstruct detailed glacial activity.

The Plio-Pleistocene seepage history off western Svalbard inferred from 3D petroleum systems modelling

Methane seepage off the coast of Svalbard is demonstrated by active gas flares in the water column today and through precipitation of methane-derived authigenic carbonates (MDAC) over the past 160 000 years. Though submarine discharge of thermogenic methane is well documented, the geological history of past leakage is still debated, largely due to unconstrained free gas sources and seepage trigger mechanisms. We have assembled a high-resolution 3D petroleum systems model to evaluate the impact and charge of potential thermogenic hydrocarbons on the Vestnesa Ridge, NW Svalbard. We show that gaseous hydrocarbons, originating from Miocene age terrigenous organic matter, accumulates largely in ~2 million-year-old (Ma) sedimentary sequences underneath the pockmark system on the ridge's crest. These traps are constantly charged until present day. The supply of free gas to the gas hydrate stability zone (GHSZ) initiated the hydrate formation at ~3.0 Ma. We also show that gas leakage to the seafloor is governed by fault corruption of the hydrocarbon traps and not by excess pore fluid pressure. The onset of episodic seafloor seepage on Vestnesa Ridge can be associated with the first shelf edge glaciation of the Svalbard-Barents Sea ice sheet (SBIS), ~1.5 Ma ago. The results of the modelled petroleum system are consistent with the notion that repeated forebulge uplift and subsidence, due to cyclic SBIS build-up and decay, can be advocated as a mechanism that repeatedly caused extensional fracturing of the eastern Vestnesa Ridge segment. This fault damage affected modelled gas accumulations and led to the formation of hydrocarbon migration pathways to the seafloor. Repeated tapping into hydrocarbon reservoirs due to (a) fracture formation promoted by glacial isostatic adjustments (GIA) and (b) fracture re-activation could explain recent observations of multiple seepage events on Vestnesa Ridge during episodes of intense cooling over the past 160.000 years.

Climate and ocean forcing of ice-sheet dynamics along the Svalbard-Barents Sea ice sheet during the deglaciation ∼20,000–10,000 years BP

The last deglaciation, 20,000–10,000 years ago, was a period of global warming and rapidly shrinking ice sheets. It was also climatically unstable and retreats were interrupted by re-advances. Retreat rates and timing relative to climatic changes have therefore been difficult to establish. We here study a suite of 12 marine sediment cores from Storfjorden and Storfjorden Trough, Svalbard. The purpose is to reconstruct retreat patterns and retreat rates of a high northern latitude marine-based ice stream from the Svalbard-Barents Sea Ice Sheet in relation to paleoceanographic and paleoclimatic changes. The study is based on abundance and composition of planktic and benthic foraminiferal assemblages, ice rafted debris (IRD), lithology, and 70 AMS-14C dates. For core 460, we also calculate sea surface and bottom water temperatures and bottom water salinity. The results show that retreat rates of the ice shelf and ice streams of Storfjorden Trough/Storfjorden (‘Storfjorden Ice Stream’) closely followed the deglacial atmospheric and ocean temperature changes. During the start of the Bølling interstadial retreat rates in Storfjorden Trough probably exceeded 2.5 km/year and more than 10,000 km2 of ice disappeared almost instantaneously. A similarly rapid retreat occurred at the start of the Holocene interglacial, when 4500 km2 of ice broke up. Maximum rates during the deglaciation match the fastest modern rates from Antarctica and Greenland. Correlation of data show that the ice streams in several fjords from northern Norway retreated simultaneously with the Storfjorden Ice Stream, indicating that temperature was the most important forcing factor of the Svalbard-Barents Sea Ice Sheet during the deglaciation.

New interpretation of the spreading evolution of the Knipovich Ridge derived from aeromagnetic data

SUMMARYInsights into the spreading evolution of the Knipovich Ridge and development of the Fram Strait are revealed from a recent aeromagnetic survey. As an ultraslow spreading ridge in an oblique system located between the Svalbard–Barents Sea and the Northeast Greenland rifted margins, the dynamics of the Knipovich Ridge opening has long been debated. Its 90° bend with the Mohns Ridge, rare in plate tectonics, affects the evolution of the Fram Strait and motivates the study of crustal deformation with this distinctive configuration. We identified magnetic isochrons on either side of the present-day Knipovich Ridge. These magnetic observations considerably reduce the mapped extent of the oceanic domain and question the present understanding of the conjugate rifted margins. Our analysis reveals a failed spreading system before a major spreading reorganization of the Fram Strait gateway around magnetic chron C6 (circa 20 Ma).

Palynological evidence of sea-surface conditions in the Barents Sea off northeast Svalbard during the postglacial period

AbstractPostglacial changes in sea-surface conditions, including sea-ice cover, summer temperature, salinity, and productivity were reconstructed from the analyses of dinocyst assemblages in core S2528 collected in the northwestern Barents Sea. The results show glaciomarine-type conditions until about 11,300 ± 300 cal yr BP and limited influence of Atlantic water at the surface into the Barents Sea possibly due to the proximity of the Svalbard-Barents Sea ice sheet. This was followed by a transitional period generally characterized by cold conditions with dense sea-ice cover and low-salinity pulses likely related to episodic freshwater or meltwater discharge, which lasted until 8700 ± 700 cal yr BP. The onset of “interglacial” conditions in surface waters was marked by a major change in dinocyst assemblages, from dominant heterotrophic to dominant phototrophic taxa. Until 4100 ± 150 cal yr BP, however, sea-surface conditions remained cold, while sea-surface salinity and sea-ice cover recorded large amplitude variations. By ~4000 cal yr BP optimum sea-surface temperature of up to 4°C in summer and maximum salinity of ~34 psu suggest enhanced influence of Atlantic water, and productivity reached up to 150 gC/m2/yr. After 2200 ± 1300 cal yr BP, a distinct cooling trend accompanied by sea-ice spreading characterized surface waters. Hence, during the Holocene, with exception of an interval spanning about 4000 to 2000 cal yr BP, the northern Barents Sea experienced harsh environments, relatively low productivity, and unstable conditions probably unsuitable for human settlements.

Deglacial–Holocene Svalbard paleoceanography and evidence of meltwater pulse 1B

Better understanding of deglacial meltwater pulses (MWPs) is imperative for future predictions of human-induced warming and abrupt sea-level change because of their potential for catastrophic damage. However, our knowledge of the second largest meltwater pulse MWP-1B that occurred shortly after the start of the Holocene interglacial remains very limited. Here, we studied fossil ostracods as paleoenvironmental indicators of water depth, salinity, and temperature in two marine sediment cores from Storfjorden, Svalbard margin (the Arctic Ocean), to investigate near-field (i.e. areas located beneath continental ice sheets at the Last Glacial Maximum) evidence of MWP-1B. The depositional environment changed from a cold bathyal environment to a warmer bathyal environment at ∼11,300 yr BP indicating incursion of warm Atlantic water into the Nordic seas, and eventually to a cold neritic environment by ∼11,000 yr BP because of melting of the Svalbard-Barents Sea ice sheet and resultant isostatic rebound. This process corresponds to rapid relative sea-level fall of 40–80 m of MWP-1B from ∼11,300 to 11,000 yr BP.

Late Weichselian glacial history of Forlandsundet, western Svalbard: an inter-ice-stream setting

The last glacial maximum (LGM) and post-glacial Quaternary history of Forlandsundet, the strait between western Spitsbergen and Prins Karls Forland, are enigmatic. Previous terrestrial field studies report contradicting evidence for an ice sheet either overriding the entire strait or completely absent during the LGM. Here, we present a multi-proxy investigation of marine sediments, high-resolution bathymetric data and aerial imagery from Forlandsundet. We reveal glacial till present at 15 cal. ka BP and geomorphological landforms characteristic to an inter-ice-stream glaciated margin. This new evidence implies that the Forlandsundet region was fully glaciated during the LGM. This glaciation was followed by a stepwise retreat of glacial ice during the Bolling–Allerod (14.7–12.7 cal. ka BP) and Younger Dryas (12.7–11.7 cal. ka BP). The Holocene record from the marine sediments is incomplete, with a hiatus from approximately 11.8 to 7.4 cal. ka BP, interpreted as an erosive event. By the mid-Holocene (7.4 cal. ka BP), more temperate, Atlantic conditions based on the benthic foraminiferal assemblages prevailed, and are followed by gradual cooling into the late Holocene (< 4 cal. ka BP). This study provides new data to resolve the LGM extent of the Svalbard–Barents Sea ice sheet in the Forlandsundet region and sheds light on the deglacial ice dynamics in a palaeo-inter-ice-stream area driven by the inflow of warm Atlantic water.

Ice‐rafting patterns on the western Svalbard slope 74–0 ka: interplay between ice‐sheet activity, climate and ocean circulation

The distribution of ice‐rafted detritus (IRD) is studied in three cores from the western Svalbard slope (1130–1880 m water depth, 76–78°N) covering the period 74–0 ka. The aim was to provide new insight into the dynamics of the Svalbard–Barents Sea Ice Sheet during Marine Isotope Stages (MIS) 4–1 to get a better understanding of ice‐sheet interactions with changes in ocean circulation and climate on orbital and millennial (Dansgaard–Oeschger events of stadial–interstadial) time scales. The results show that concentration, flux, composition and grain‐size of IRD vary with climate and ocean temperature on both orbital and millennial time scales. The IRD consists mainly of fragments of siltstones and mono‐crystalline transparent quartz (referred to as ‘quartz’). IRD dominated by siltstones has a local Svalbard–Barents Sea source, while IRD dominated by quartz is from distant sources. Local siltstone‐rich IRD predominates in warmer climatic phases (interstadials), while the proportion of allochthonous quartz‐rich IRD increases in cold phases (glacials and stadials/Heinrich events). During the Last Glacial Maximum and early deglaciation at 24–16.1 ka, the quartz content reached up to &gt;90%. In warm climate, local iceberg calving apparently increased and the warmer ocean surface caused faster melting. During the glacial maxima (MIS 4 and MIS 2) and during cold stadials and Heinrich events, the local ice‐sheets must have been relatively stable with low ablation. During ice retreat phases of the MIS 4/3 and MIS 2/1 transitions, maxima in IRD deposition were dominated by local coarse‐grained IRD. These maxima correlate with episodes of climate warming, indicating a rapid, stepwise retreat of the Svalbard–Barents Sea Ice Sheet in phase with millennial‐scale climate oscillations.

Early Holocene Establishment of the Barents Sea Arctic Front

A main feature of the Barents Sea oceanography is the Arctic front. The Arctic front marks the transition between the southern Atlantic water and northern Arctic water dominated parts of the Barents Sea. Presently, the Barents Sea Arctic front is directed by the topography of the Bear Island Trough and to some degree the location of the Marginal Sea Ice Zone. During the last glacial maximum, the Svalbard-Barents Sea and Scandinavian Ice Sheets covered the Barents Sea. Hence, no water entered the Barents Sea, neither from the south nor from the north. Following the deglaciation of the Barents Sea, the present-day ocean circulation developed. The evolution of how the present location of the Barents Sea Arctic front established during the early Holocene is documented by foraminiferal relative assemblage data from six core sites along the western Barents Sea margin and entrance. The relative abundance of Arctic front indicator Turborotalita quinqueloba, in combination with the cold, polar Neogloboquadrina pachyderma and warm, Atlantic Neogloboquadrina incompta, are used to infer the location of the Barents Sea Arctic front relative to the individual core sites. Until ca. 11 ka BP, the Barents Sea Arctic front followed the western margin of the Barents Sea. All sites along the Barents Sea margin where still dominated by Arctic water between ca. 11 and 10.2 ka BP, however, the Barents Sea Arctic front turned eastwards into the southwestern Barents Sea. From ca. 10 to 8.8 ka BP, the Barents Sea Arctic front followed the Barents Sea margin and the northern and southern borders of the Bear Island Trough. Hence, from this time on the topography of the Bear Island Trough became a steering component. The northwestern Barents Sea Arctic front was close to the present location from ca. 8.8 to 7.4 ka BP, however, it was still confined to the southwestern Barents Sea. From ca. 7.4 ka BP, the Barents Sea Arctic front has been located close to the present position, along the margin southwards from Svalbard, turning eastwards along and beyond the northern Bear Island Trough margin.

Paleoceanography of northeastern Fram Strait since the last glacial maximum: Palynological evidence of large amplitude changes

Sea-surface conditions in northeastern Fram Strait since the last glacial maximum (LGM) were reconstructed from cores MSM5/5-712-2 and PS2863/1–2 based on palynological assemblages, ecological preferences of dinocysts and application of the modern analog technique. Dinocyst in LGM sediments are sparse, but their assemblages reflect mild summer conditions. Given the regional context and evidence from other tracers, the dinocyst assemblages of the LGM could relate to regional fluxes of dinocysts during exceptional mild summers. From 19 to 14.7 ka, dinocyst data suggest very cold conditions with extensive sea-ice cover, while abundant reworked palynomorphs indicate intense glacial erosion. An abrupt transition at 14.7–14.5 ka was marked by a peak in summer temperatures coinciding with a rapidly deposited sediment layer related to a regional meltwater plume event in western Svalbard. From 14.7 to 12.6 ka, large seasonal temperature contrasts with mild summers and cold winters together with low salinity indicate continuous melting of the Svalbard Barents Sea ice sheet fostered by warm climate. At 12.6 ka, the regional onset of the Younger Dryas was marked by cooling and increased salinity. On a regional scale, the 12.6–12 ka interval corresponds to an important transition involving enhanced circulation of Arctic waters around Svalbard and establishment of coastal fronts along its northern and western margins. Modern-like oceanic conditions with relatively high salinity and low seasonal temperature contrast developed at about 7.6 ka. Since then, a slight cooling is observed, especially in winter. This study offers a comprehensive picture of the deglacial phases in eastern Fram Strait with unique data on the sea-surface salinity, which controls surface water stratification and plays an important role in ocean circulation.

A 190-ka biomarker record revealing interactions between sea ice, Atlantic Water inflow and ice sheet activity in eastern Fram Strait

The northeastern Fram Strait at the entrance to the Arctic Ocean represents a key observatory for sea ice reconstructions as it sensitively reacts to environmental changes. A combined biomarker approach (HBIs, sterols, alkenones) was carried out on Core PS93/006-1 from the western Svalbard margin to reconstruct sea ice conditions related to glacial–interglacial cycles of the last 190 ka. The continuous presence of sea ice demonstrates the strong influence of polar water masses in the eastern Fram Strait. Glacial intervals are characterised by extended sea ice conditions with perennial sea ice cover during early MIS 6, the Penultimate Glacial Maximum, the interstadial MIS 5d, MIS 4 and the Last Glacial Maximum. Less severe, yet highly variable, sea ice conditions with more frequent summer melt dominated the interglacial stages. The opposing sea ice conditions along the western and northern Svalbard margin highlight the different regional impact of various environmental forces in eastern Fram Strait. Thus, the major expansion of the Svalbard Barents Sea Ice Sheet favoured the formation of perennial sea ice west of Svalbard while it triggered the establishment of marginal ice cover on the Yermak Plateau.