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The size of the last glacial ice sheet on the Northeast (NE) Greenland shelf and its interaction with ocean circulation have been the subject of debate. Here we provide insights into the extent of the ice sheet around the Last Glacial Maximum (LGM) and investigate timing and strength of changes in the flow of Atlantic Water. The study is based on a multiproxy investigation of a marine sediment core, gravity core DA17-NG-ST01-019G, from 323-m water depth at the NE Greenland shelf edge at 79.4°N. We present benthic and planktic foraminiferal distribution data, AMS-14C dates, sedimentological (ice-rafted debris (IRD) and grain sizes), and geochemical (XRF) data in combination with geophysical (sub-bottom profiler) data. The oldest sediments at the study site are dated to 25.5–17.5 ka, encompassing the time frame from the beginning of the LGM to the early deglaciation. This part is overlain by sediments from the late deglaciation and Holocene. The deposits dating from the LGM are very rich in both planktic and benthic foraminifera and macrofossils of excellent preservation. The faunas show that the site generally was affected by a strong flow of relatively warm subsurface Atlantic Water during the LGM and Early Holocene. Conditions turned more polar with cold bottom water flow in the Middle–Late Holocene (c. 7.5 ka to Recent) with presence of mainly agglutinated benthic foraminiferal species. Our data from the LGM also indicate that the deposits were mixed by iceberg scouring, confirmed by the geophysical data showing extensive ploughing of the sediments on the outer shelf area. The results further indicate that the Greenland Ice Sheet did not reach to the edge of the NE Greenland shelf at 79.4°N during the LGM 24–18 ka.

Process-based, mechanistic research of mineral authigenesis has been progressively utilized to understand the biogeochemical processes taking place at the sediment–water interface (SWI), and to capture long-term sedimentary (biogeochemical) records of paleoenvironments. A better understanding of mineral authigenic sedimentary processes directly beneath the SWI in Arctic continental shelves is thus fundamental as Earth’s polar regions are at greatest risk of future climate change. This is in part due to disturbances in the benthic–pelagic coupling related to changes in ocean circulation and sea ice dynamics.In this study, we aim at focusing on the Holocene period by investigating sedimentary archives recovered from the NE Greenland shelf during the NorthGreen17 Expedition. Here we combined a suite of sedimentological (e.g., detailed ichnological analysis and taphonomic features of the benthic foraminifera Cassidulina neoteretis), mineralogical (bulk and clay mineralogy) and geochemical (major, trace and rare earth elements, and δ13C and δ18O stable isotope signatures recorded in Cassidulina neoteretis) proxies with bulk organic matter parameters (δ13C, TOC, TN). The first results of this study, presented during the EGU General Assembly 2023 in Vienna, Austria, focus on several important points such as: (1) changes in sedimentation (geochemical characteristics) over the NE Greenland sediment profiles; (2) evolutionary characteristics of terrigenous influx, redox conditions and productivity; and (3) controlling factors and modes of organic matter accumulation.

The Northeast Greenland shelf is a broad Arctic shelf located between Greenland and Fram Strait. It is the principal gateway for sea ice export and sea ice-associated freshwater from the Arctic Ocean. Sea ice thickness has decreased by 15% per decade since the early 1990s and meteoric freshwater discharge has increased. The consequence of changing sea-ice and freshwater conditions in the region on ocean dynamics and the biological system remains unknown. Determining the source(s) of freshwater is important to be able to understand how the area will react to future upstream change. Here we present a synoptic survey of the Northeast Greenland shelf and slope with observations of hydrography, the nutrients nitrate, phosphate and silicate, and conservative tracers δ18O, δ2H and total alkalinity during late summer 2017. We compare these to previously published values, including those which identify Pacific and Atlantic water, the Siberian shelf seas, and the 6 largest Arctic rivers. We show that a major source of freshwater on the Northeast Greenland shelf during late summer 2017 is the Laptev Sea and find no conclusive evidence of Pacific Water. Our observations provide a direct link between Northeast Greenland hydrology and processes occurring on Eurasian shelves.

The projections of future scenarios under the current trend of global climate change demand a better understanding of the long-term ice-ocean-tectonic interactions, and in particular the potential meltwater contributions from modern ice sheets. The sensitivity of the Greenland Ice Sheet to polar amplification, changes in ocean heat transport and deteriorating perennial sea ice conditions makes the Northeast Greenland margin one of the most critical locations to understand the impact of future climate change on ice sheet instability and associated sea level rise. The development of oceanic gateways controlling the long-term water mass exchanges between the Arctic and Atlantic oceans, notably the Fram Strait and the Greenland-Scotland Ridge, have played a pivotal role for the Cenozoic evolution of the Northeast Greenland regions. In Northeast Greenland, ice-ocean-tectonic interactions and coupling between the ice sheet, ocean and sea ice are readily observable today, but geological records that can illuminate long-term trends are lacking. Consequently, NorthGreen MagellanPlus workshop was organised at the Geological Survey of Denmark and Greenland in collaboration with Aarhus (Denmark) and Stockholm (Sweden) universities in November 2022 as an international effort to develop Mission Specific Platform (MSP) proposals on Northeast Greenland margins under the umbrella of the European Consortium for Ocean Research Drilling (ECORD). For three days, seventy-one participants (56 in person + 15 online) discussed the key scientific questions and primary targets for scientific drilling in Northeast Greenland. Three pre-proposals have been initiated during the workshop targeting Morris Jesup Rise, Northeast Greenland continental shelf and Denmark Straight.

Radiocarbon dating marine sediments is complicated by the strongly heterogeneous age of ocean waters. Tephrochronology provides a well-established method to constrain the age of local radiocarbon reservoirs and more accurately calibrate dates. Numerous ultra-distal cryptotephra deposits (non-visible volcanic ash more than 3000 km from source) have been identified in peatlands and lake sediments across north-eastern North America and correlated with volcanic arcs in the Pacific north-west. Previously, however, these isochrons have not been identified in sediments from the north-west Atlantic Ocean. In this study, we report the presence of two ultra-distal cryptotephra deposits; Mazama Ash and White River Ash eastern lobe (WRAe), in Placentia Bay, North Atlantic Ocean. We use these well-dated isochrons to constrain the local marine radiocarbon reservoir offset (ΔR) and develop a robust Bayesian age–depth model with a ΔR that varies through time. Our results indicate that the marine radiocarbon offset in Placentia Bay was -126±151 years (relative to the Marine20 calibration curve) at the time of Mazama Ash deposition (7572 ± 18 yr BP) and −396 ± 144 years at the time of WRAe deposition (1098–1097 yr BP). Changes in ΔR appear to coincide with inferred shifts in relative influences of the inner Labrador Current and the Slopewater Current in the bay. An important conclusion is that single-offset models of ΔR are easiest to apply and often hard to disprove. However, such models may oversimplify reservoir effects in a core, even over relatively short timescales. Acknowledging potentially varying offsets is critical when ocean circulation and ventilation characteristics have differed over time. The addition of tephra isochrons permits the calculation of semi-independent reservoir corrections and verification of the single ΔR model.

Heinrich events associated with millennial-scale climate oscillations during the last glacial period are prominent events of ice-sheet collapse, characterized by the dispersal of ice(berg) rafted debris and freshwater across the North Atlantic. Hudson Strait has been suggested as one of the predominant iceberg source regions. One potential mechanism triggering iceberg release invokes cryosphere-ocean interactions, where subsurface warming destabilizes the Laurentide ice sheet. Subsurface warming is facilitated by the expansion of sea ice in the Labrador Sea in combination with a slow down of the Atlantic Meridional Overturning Circulation, which prevents the release and downward mixing of heat in the water column.Here we present high-resolution reconstructions of sea ice dynamics in the outer Labrador Sea at IODP Site U1302/03 between 30 ka and 60 ka. Sea ice reconstructions are based on a suite of sympagic and pelagic biomarkers, including highly branched isoprenoids and sterols. The results suggest a transition from reduced/seasonal to extended/perennial sea ice conditions preceding the onset of iceberg rafting associated with Heinrich event 3, 4, 5, and 5a by ~0.9 ± 0.5 ka. Ongoing work on the same core and sample material will have to confirm the timing and extent of subsurface warming compared to sea ice advances.

The western Fram Strait is the only deep-water gateway connecting the Arctic Ocean and North Atlantic. Consequently, today, the western Fram Strait and the Northeast Greenland shelf receive cold, low saline Polar and Arctic Atlantic waters from the Arctic Ocean incorporated in the East Greenland Current, together with warmer, saline recirculated Atlantic Water masses derived from the West Spitsbergen Current. We present a multiproxy study (grain size distribution, XRF core scans, and benthic foraminiferal assemblages) based on the lower part of the radiocarbon dated marine sediment core DA17-NG-ST03-039G, covering the period from 13.3 to 3.9 cal ka BP. We reconstruct the deglacial conditions of the Northeast Greenland shelf together with Early to Mid Holocene fluctuations in subsurface Atlantic Water and Polar Water advection. The results show that the outer Northeast Greenland shelf was deglaciated and marine conditions were established prior to c. 13.3 cal ka BP. At this time, our data show Atlantic Water masses flowing beneath an extensive sea-ice cover in a glaciomarine setting, potentially related to the Bølling-Allerød warm period. Around 12.9 cal ka BP, the onset of high surface and bottom water productivity may be associated with the Younger Dryas onset. This was followed by a transition towards warmer bottom and subsurface water conditions from c. 11.7 until 10.2 cal ka BP caused by enhanced advection of Atlantic-derived water masses. A cold period with marginal ice zone conditions and enhanced East Greenland Current incursion is evident from 10.2 to 9.4 cal ka BP, succeeded by harsher sea-ice conditions and Atlantic Water inflow, prevailing until c. 7.5 cal ka BP. Holocene Thermal Maximum conditions, characterized by high surface and subsurface water productivity, were promoted by enhanced Atlantic Water flow to the shelf from c. 7.5 to 6.7 cal ka BP. In contrast, the transition towards a cold period with increased drift-ice transport via a strong East Greenland Current is recorded from c. 6.2 cal ka BP and to the end of our record at 3.9 cal ka BP; it was associated with the onset of the Neoglaciation., Quaternary Science Reviews, 293, ISSN:0277-3791

The Fram Strait is one of the largest gateways through which meltwater and sea ice are exported to thesubarctic North Atlantic, transiting the North-East Greenland shelf via the southward flowing EastGreenland Current. Observations indicate a recent freshening of the East Greenland Current that mayhave implications for wider oceanic circulation regimes. The North-East Greenland shelf is an opportuneregion to assess these changes back through time. Paleoceanographic reconstructions from the North-East Greenland shelf are sparse and their temporal coverage is limited to the Holocene, limiting ourability to assess the impact of rapid climatic variations on marine conditions, such as during the YoungerDryas/Holocene transition. Here, we present data from a well-dated marine sediment core retrieved fromthe North-East Greenland shelf (74N; east of Young Sound-Tyrolerfjord system) that captures the lateYounger Dryas Stadial through to the Mid-Holocene at sub-centennial resolution. We apply a multi-proxyapproach to reconstruct changes in productivity, surface and bottom ocean conditions. We show that at74 N the presence of warm Atlantic waters on the inner North-East Greenland shelf was limited to thelate Younger Dryas, as the Greenland Ice Sheet retreated landward and isostatic rebound caused the areato uplift. A unique dimension to this record is its location within one of the few biological hotspots on theEast Greenland shelf today; the Sirius Water polynya. Archaeological studies indicate the polynya wasforming as early as 4500 years ago, but nothing is known about its evolution from a marine perspective.Cooling of bottom waters, increasing sea-surface productivity and more frequent open water conditionsindicate an Early Holocene onset of the Sirius Water (ca. 10e8.7 ka BP).

The melting of marine terminating glaciers in Northeast Greenland is a visible sign that our climate is changing. This melt has been partly attributed to changes in oceanic heat fluxes, particularly warming of Atlantic Water (AW). Yet our understanding of the interaction between glaciers and the ocean is limited by the length of instrumental records. Here, we present a multi-proxy study (benthic foraminifera assemblages, CT scans, grain size, XRF, and stable isotope data) on core DA17-NG-ST08-092G, located 90 km east of the Northeast Greenland Ice Stream (NEGIS). Whilst the exact timing of deglaciation is uncertain, it is certain to have occurred at least as early as 12.5 ka cal BP, and likely before 13.4 ka cal BP. The inflow of AW may have played a role in the seemingly early deglaciation on the Northeast Greenland continental shelf. Following deglaciation, the site was overlain by an ice shelf, with AW and Polar Water (PW) flowing beneath until 11.2 ka cal BP. The NEGIS briefly retreated westwards between 11.2 and 10.8 ka cal BP before our site returned to glacier-proximal conditions dominated by colder subsurface water and persistent AW flowing beneath (10.8–9.6 ka cal BP). Between 9.6 and 7.9 ka cal BP the NEGIS retreated westwards; there was a continued presence of AW and PW at the site. A drastic shift in ocean circulation occurred at 7.9 ka cal BP, with a decline in AW flow and dominance of PW flowing beneath perennial sea ice. During the Late Holocene, there was return of AW and likely breakup of perennial sea ice., Quaternary Science Reviews, 286, ISSN:0277-3791

Sediment core ER11-16 from Køge Bugt in Southeast Greenland is used to assess early Holocene palaeoceanographic changes and sediment rafting from icebergs calved from the large outlet glaciers in the area. Diatom analysis reconstructs variability in surface water temperature, salinity and sea-ice concentrations, and benthic foraminiferal assemblages is used to reconstruct subsurface ocean conditions. We report Holocene Thermal Maximum in Southeast Greenland during the early Holocene (at least since onset of the record 9100 cal yr BP) until around 4500 cal yr BP, which contrasts with a delay until the mid-Holocene of the Holocene Thermal Maximum in South and Southwest Greenland. The early Holocene warming in Southeast Greenland was caused by a combination of high solar insolation and a weakened subpolar gyre, both of which served to warm the Irminger Current waters subducting onto the shelf. At the same time, the surface temperature was relatively high and sea-ice cover in the polar surface waters of the East Greenland Current was relatively low. High levels of iceberg rafting occurred in Køge Bugt during the early Holocene, synchronously with these warm oceanic temperatures. This is attributed to an increase in iceberg production from the extensive, but retreating, Greenland Ice Sheet. The warm surface conditions were interrupted by a marked and short-lived increase in sea ice around 8200 years ago, providing the first evidence of this global cold episode in Southeast Greenland. After 4500 cal. yr BP, sea-ice cover increased with an expansion of the East Greenland Current, suppressing the inflow of warmer subsurface Irminger Current water to the Southeast Greenland shelf. We relate this oceanic shift to the decreased Northern Hemisphere summer solar insolation. Multi-centennial variability is observed in the grain size spectrum of iceberg rafted debris; a finding we interpret in the context of palaeoceanographic changes.

The timing of the flooding of the Danish/German/Swedish straits and the first marine influence in the Baltic Basin after the Ancylus Lake stage has been much debated. Here we present 47 new radiocarbon ages from sediment cores retrieved from Danish waters, ages that record the marine transgression of the area. Most of the ages are based on shells of marine molluscs, hence the ages are uncertain because we do not know the precise reservoir age in the past.We use a reservoir age of 400 years, which is based on dating of museum specimens collected live before testing of nuclear bombs. It appears from the ages that the Great Belt (Storebælt) was inundated before The Sound (Øresund). The oldest ages on marine shells from the northern part of the Great Belt region are about 8.9 cal. ka BP.From the central part of the Great Belt, the oldest ages are about 8.2 cal. ka BP, in Mecklenburg Bay 8.1 cal. ka BP and in the Arkona Basin 7.1 cal. ka BP. Sediments deposited prior to the occurrence of marine molluscs contain brackish-water ostracods (Cyprideis torosa and Cytheromorpha fuscata); the sediments are usually laminated and non-bioturbated mud. The brackish-water phase may have lasted 500–1000 years. The youngest lake deposits without signs of marine influence are dated to c. 8.8 cal. ka BP(central Great Belt), 8.7 cal. ka BP(Little Belt)and8.5 cal. ka BP(Arkona Basin). We see no evidence for marine influence at c. 10 cal. ka BP as recorded by some studies from the Baltic Basin.

We address here the specific timing and amplitude of sea-surface conditions and productivity changes off SW Greenland, northern Labrador Sea, in response to the high deglacial meltwater rates, the Early Holocene maximum insolation and Neoglacial cooling. Dinocyst assemblages from sediment cores collected off Nuuk were used to set up quantitative records of sea ice cover, seasonal sea-surface temperature (SST), salinity (SSS), and primary productivity, with a centennial to millennial scale resolution. Until similar to 10 ka BP, ice-proximal conditions are suggested by the quasi-exclusive dominance of heterotrophic taxa and low dinocyst concentrations. At about 10 ka BP, an increase in species diversity and abundance of phototrophic taxa marks the onset of interglacial conditions at a regional scale, with summer SST reaching up to 10 degrees C between 8 and 5 ka BP, thus in phase with the Holocene Thermal Maximum as recorded in the southern Greenlandic areas/northern Labrador Sea. During this interval, low SSS but high productivity prevailed in response to high meltwater discharge and nutrient inputs from the Greenland Ice Sheet. After similar to 5 ka BP, a decrease in phototrophic taxa marks a two-step cooling of surface waters. The first started at similar to 5 ka BP, and the second at similar to 3 ka BP, with a shift toward colder conditions and higher SSS suggesting reduced meltwater discharge during the Neoglacial. This second step coincides with the disappearance of the Saqqaq culture. The gap in human occupation in west Greenland, between the Dorset and the Norse settlements from 2000 to 1000 years BP, might be linked to high amplitude and high frequency variability of ocean and climate conditions.

The NE Greenland shelf, together with the Fram Strait, form the main sea ice and cold-water transport pathway between the Arctic Ocean and the Nordic seas. As such, these regions play a part in the Atlantic meridional overturning cell that is driven by the thermohaline convection taking place in subpolar and Polar regions. The ocean circulation, freshwater export and sea ice extent are heavily influenced by the interplay of oceanography, climate, glacial landforms and bathymetry.Over the outer NE Greenland shelf, a layer of low salinity, cold Polar Water overlies a body of Atlantic Water (AW) that is either recirculated directly across the Fram Strait or further in the Arctic Ocean from where it returns as colder, modified Arctic-Atlantic Water. The relative contributions of these two types of AW recirculation bear significant implications to the deep-water formation and thus, the global ocean circulation, but little is known about the change in AW source over time and how it affects the local environmental settings.This study aims to describe the paleoceanographic development of the outer Norske Trough using a multi-proxy approach to sediment gravity core DA17-NG-ST12-135G. The core was taken on the NorthGreen17 Expedition from the outmost location in an east-west transect of cores along the trough. When combined with the other cores, it can be used to reconstruct the oceanic forcing on the northeastern Greenland Ice Sheet and its deglaciation history along the Norske Trough. The data used includes AMS 14C dating, sedimentary description, grain size analysis, µ-XRF core scanning and benthic foraminifera analysis. The preliminary results suggest intermittent early AW water influence and high seasonal productivity just east of the Northeast Greenland Ice Stream grounding line during the early deglaciation. AW influence on the outer NE Greenland Shelf is relatively constant after the deglaciation, but changes in productivity and current strengths are captured by the data.

It is unequivocal that the climate is changing; marine terminating glaciers in Northeast Greenland (NEG) have experienced rapid speedup and retreat in recent decades as a result. The Zachariae Isstrøm (ZI) began accelerating in 2000, resulting in the total collapse of its floating ice tongue. This has been partly attributed to basal melting caused by the warming of Atlantic Water (AW). Unfortunately, our understanding of the interaction between these entities is somewhat limited by the length of instrumental records. Examining proxies preserved in marine sediment cores provides an alternative method to understand these changes on longer timescales.Here we apply a multi-proxy approach (XRF, benthic foraminifera, stable isotopes, grain size, CT scans) to marine sediment core DA17-NG-ST08-092G, collected from the NEG continental shelf, 90km east of the ZI terminus. Our results indicate that the site was free of grounded ice at least as early as 12.5 ka cal BP, and most likely before 13.4 ka cal BP. The inflow of AW onto the continental shelf may have played a role in the seemingly early deglaciation at this site. Between 13.4 and 11.2 ka cal BP the site was overlain by a floating ice tongue, most likely the ZI, with AW and PW flowing beneath. Following this, the ZI briefly retreated westwards (11.2-10.8 ka cal BP) before it re-advanced (10.8-9.6 ka cal BP); there was a strong influx of AW throughout these periods. Between 9.6 and 7.9 ka cal BP the ZI retreated westwards again, before a drastic shift in ocean circulation occurred at 7.9 ka cal BP. At this time, there was a sharp decline in AW corresponding to an increase in PW flowing beneath perennial sea ice. In the final part of the record, AW returns and there was likely a breakup of the perennial sea ice.

The Greenland Ice Sheet (GIS), the second largest ice sheet on Earth, has experienced a dramatic ice mass reduction during the last decades, coincident with global warming and an increase in atmospheric CO2. About 16% of the GIS is currently drained via marine terminating glaciers, mostly through the Northeast Greenland Ice Stream (NEGIS; with ~12%). Two cross-shelf troughs (Norske and Westwind troughs) served as drainage pathways of the NEGIS. According to numerical ice-sheet models, a whole meltdown of the GIS may cause a global sea−level rise of >7 m, causing permanent damage to the environment and countless economic impacts on our coastal society. In order to better understand the processes driving these present changes, studies of the development of glaciers/glacial troughs and ice sheets in response to past climate changes are required for testing numerical models that seek to predict ice-sheet response to anthropogenic climate change.In this study, high-resolution INNOMAR sediment subbottom profiler data combined to multi-proxy analyses of gravity core DA17-NG-ST10-117G, obtained from Norske Trough during the NorthGreen17 expedition, are investigated. Multi-proxy data derived from the sediment gravity core include 14C-derived ages, descriptions of sedimentary units, compositional variability of ice-rafted debris, and continuous logging of magnetic susceptibility and micro-XRF core scanning. In Norske Trough, submarine glacial landforms indicate that ice sheet retreat to the outer middle shelf after the Last Glacial Maximum (LGM) was stepwise, with phases of grounding line stabilization, while ice sheet retreat from the middle shelf to the coastline during deglaciation was fast. Sedimentological evidence at our recorded coring site captures the transition from sub–ice stream (subglacial) environments to proximal (proglacial)/distal glaciomarine conditions during the LGM to Holocene recession. In addition, preliminary foraminifera analysis indicates warmer recirculating Atlantic Water on the middle Norske Trough immediately on deglaciation, suggesting that oceanic forcing very likely played a significant role during the retreat of the ice margin. This presentation will include a comprehensive comparison of the spatio-temporal sedimentation patterns across the Norske Trough.

Climate warming is rapidly reshaping the Arctic cryosphere and ocean conditions, with consequences for sea ice and pelagic productivity patterns affecting the entire marine food web. To predict how ongoing changes will impact Arctic marine ecosystems, concerted effort from various disciplines is required. Here, we contribute multi‐decadal reconstructions of changes in diatom production and sea‐ice conditions in relation to Holocene climate and ocean conditions off northwest Greenland. Our multiproxy study includes diatoms, sea‐ice biomarkers (IP25 and HBI III) and geochemical tracers (TOC [total organic carbon], TOC:TN [total nitrogen], δ13C, δ15N) from a sediment core record spanning the last c. 9,000 years. Our results suggest that the balance between the outflow of polar water from the Arctic, and input of Atlantic water from the Irminger Current into the West Greenland Current is a key factor in controlling sea‐ice conditions, and both diatom phenology and production in northeastern Baffin Bay. Our proxy record notably shows that changes in sea‐surface conditions initially forced by Neoglacial cooling were dynamically amplified by the shift in the dominant phase of the Arctic Oscillation (AO) mode that occurred at c. 3,000 yr BP, and caused drastic changes in community composition and a decline in diatom production at the study site. In the future, with projected dominant‐positive AO conditions favored by Arctic warming, increased water column stratification may counteract the positive effect of a longer open‐water growth season and negatively impact diatom production., We present the first continuous and high‐resolution diatom record from northeastern Baffin Bay spanning the last c. 9,000 years. Our data show that the variability in sea ice and primary production on the northwest Greenland shelf is linked to modulations in millennial‐scale Arctic Oscillation. The phenology and diatom community structure is largely controlled by water‐column stratification and sea‐ice conditions.

A new calcareous Arctic foraminiferal species, Glomulina oculus n. sp., belonging to the suborder Miliolina has been observed in surface samples from northern Nares Strait and Petermann Fjord, NW Greenland, and off Zachariae Isbrae, NE Greenland, as well as in early Holocene sediments from the northern Baffin Bay region and on the NE Greenland shelf. In some samples, this new porcelaneous species makes up a significant fraction of the foraminiferal assemblage, particularly in samples with a relatively large sand content, and we suggest that this species is indicative of an Arctic environment with marine-terminating glaciers. Yet, further studies are needed to ascertain its full habitat range.

Climate warming and the resulting acceleration of freshwater discharge from the Greenland Ice Sheet are impacting Arctic marine coastal ecosystems, with implications for their biological productivity. To accurately project the future of coastal ecosystems and place recent trends into perspective, palaeo-records are essential. Here, we show runoff estimates from the late 19th century to the present day for a large sub-Arctic fjord system (Nuup Kangerlua, southwest Greenland) influenced by both marine- and land-terminating glaciers. We followed a multiproxy approach to reconstruct spatial and temporal trends in primary production from four sediment core records, including diatom fluxes and assemblage composition changes and biogeochemical and sedimentological proxies (total organic carbon, nitrogen, C/N ratio, biogenic silica, δ13C, δ15N, and grain-size distribution). We show that an abrupt increase in freshwater runoff in the mid-1990s was reflected by a 3-fold increase in biogenic silica fluxes in the glacier-proximal area of the fjord. In addition to increased productivity, freshwater runoff modulates the diatom assemblages and drives the dynamics and magnitude of the diatom spring bloom. Our records indicate that marine productivity is higher today than it has been at any point since the late 19th century and suggest that increased mass loss of the Greenland Ice Sheet may continue promoting high productivity levels at sites proximal to marine-terminating glaciers. We highlight the importance of palaeo-records in offering a unique temporal perspective on ice–ocean–ecosystem responses to climate forcing beyond existing remote sensing or monitoring time series.

We propose a new relative shore-level curve for the Aarhus Bugt area, an embayment in eastern Jylland, Denmark, based on a compilation of pub- lished and new radiocarbon ages of organic material. Lakes existed in the area during the Late Glacial and Early Holocene. Lake level rose gradually until the region was inundated by the sea at c. 9000 cal. years BP. The relative sea level reached a high stand at about 6000 cal. years BP, when the local relative sea level was c. 3 m above present-day mean sea level. The Aarhus Bugt area was inundated by the sea later than the Limfjord area in northern Jylland, but earlier than the Lillebælt region in southern Denmark. The shore- level curves for these areas differ partly because the glacio-isostatic uplift was more pronounced in the Limfjord area than farther south and partly because the northern regions were inundated by the sea earlier than the southern areas.

The Labrador Current is part of the anticlockwise subpolar gyre and plays a major role in the formation of North Atlantic Deep Water. It is influenced by the West Greenland and Baffin currents supplying warmer Atlantic and cold polar waters, respectively. During the early Holocene, at the final stage of the last deglaciation, meltwater and iceberg discharge caused highly variable conditions in the Labrador Current. In order to assess its sensitivity to such freshening, this study provides a well-resolved Holocene paleoclimatic record from the Labrador Shelf. Based on benthic foraminiferal faunal and alkenone biomarker analyses, we differentiated four distinct climatic periods in the western Labrador Sea. From 8.9 to 8.6 ka BP, the Labrador Shelf was dominated by polar water outflow from Baffin Bay and covered by perennial sea ice. Between 8.6 and 7.4 ka BP, a strong subsurface inflow of warmer Atlantic water masses is ascribed to an intensification and redirection of the West Greenland Current. At 7.4 ka BP, the decreased influence of Atlantic water masses on the Labrador Shelf marks the establishment of winter convection leading to the formation of Labrador Sea Water in the central basin. Concurrently, an intensified polar water outflow through the Canadian Gateways strengthened the inner Labrador Current, and higher primary productivity suggests longer spring blooms because of a shorter sea-ice season during the Holocene Thermal Maximum. In the late Holocene after 3 ka BP, periodic fluctuations of primary productivity may tentatively be correlated with stronger and weaker northwesterly winds.

One active journal. Fourteen legacy titles. More than 3000 articles published since 1893 – some digitised, some not. One full-time member of staff. A small team of dedicated geoscientists. Limited budget. PlanS. Open-source journal software. If these are the ingredients, what is the recipe? Like many surveys, the Geological Survey of Denmark and Greenland (GEUS) has a long history of publishing. Our full catalogue of titles extends back to 1893 and our current title, GEUS Bulletin (www.geusbulletin.org; formerly Geological Survey of Denmark and Greenland Bulletin), has been active since 2003. Our journals have always been grassroots initiatives – run by scientists, for scientists. But two years ago, amid the fast-changing demands of digital publishing, the Survey faced a quandary: should we continue publishing our own journal? At a time of rapid proliferation of journals for any discipline imaginable, what niche did a geographically-focused journal fill? What should we modernise? Could we relaunch as an online, diamond open-access journal on our existing budget? Could we implement more of the services our authors wanted and attract more authors beyond our traditional audience? Two years later, we have successfully re-launched our collection of journals, without increasing our overall budget. Using open-source solutions, we have transformed our print-focused publication workflow to a new online, open-access platform and data repository. We are currently migrating our entire back catalogue of legacy titles to the same platform. Although we only have visitor data for our new platform since November 2020, we can see early signs of increased article views (c. +82% in Nov–Dec 2020, compared with the same months in 2018 and 2019) and a jump in traffic from external websites like Google Scholar (from 5% before re-launch to 35% after re-launch). In this presentation, we present a recipe that we hope other geological surveys, societies and institutions can follow when launching (or relaunching) their own journals using open-source solutions. We review the options available to small survey or society publishers on a limited budget, from journal hosting to typesetting. We highlight the advantages of non-profit open-access publishing and open source, community-driven solutions that currently exist. We close by highlighting the barriers that remain for small non-profit publishers when balancing discoverability, journal impact and compliance with the latest open-access initiatives such as Plan S, and web accessibility regulations. It is still early days for GEUS Bulletin, but we see the adoption of open-source platforms as the key ingredient to our potential for success in the coming years. Such platforms allow us to offer diamond open-access publishing and a data repository, while maintaining our non-profit, publishing model with neither author nor reader fees.

The polar regions exhibit some of the most visible signs of climate change globally; annual mass loss from the Greenland Ice Sheet (GrIS) has quadrupled in recent decades, from 51 ± 65 Gt yr−1 (1992-2001) to 211 ± 37 Gt yr−1 (2002-2011). This can partly be attributed to the widespread retreat and speed-up of marine-terminating glaciers. The Zachariae Isstrøm (ZI) is an outlet glacier of the Northeast Greenland Ice Steam (NEGIS), one of the largest ice streams of the GrIS (700km), draining approximately 12% of the ice sheet interior. Observations show that the ZI began accelerating in 2000, resulting in the collapse of the floating ice shelf between 2002 and 2003. By 2014, the ice shelf extended over an area of 52km2, a 95% decrease in area since 2002, where it extended over 1040km2. Paleo-reconstructions provide an opportunity to extend observational records in order to understand the oceanic and climatic processes governing the position of the grounding zone of marine terminating glaciers and the extent of floating ice shelves. Such datasets are thus necessary if we are to constrain the impact of future climate change projections on the Arctic cryosphere.A multi-proxy approach, involving grain size, geochemical, foraminiferal and sedimentary analysis was applied to marine sediment core DA17-NG-ST8-92G, collected offshore of the ZI, on the Northeast Greenland Shelf. The aim was to reconstruct changes in the extent of the ZI and the palaeoceanographic conditions throughout the Early to Mid Holocene (c.a. 12,500-5,000 cal. yrs. BP). Evidence from the analysis of these datasets indicates that whilst there has been no grounded ice at the site over the last 12,500 years, the ice shelf of the ZI extended as a floating ice shelf over the site between 12,500 and 9,200 cal. yrs. BP, with the grounding line further inland from our study site. This was followed by a retreat in the ice shelf extent during the Holocene Thermal Maximum; this was likely to have been governed, in part, by basal melting driven by Atlantic Water (AW) recirculated from Svalbard or from the Arctic Ocean. Evidence from benthic foraminifera suggest that there was a shift from the dominance of AW to Polar Water at around 7,500 cal. yrs. BP, although the ice shelf did not expand again despite of this cooling of subsurface waters.

Arctic sea ice is declining at an unprecedented pace as the Arctic Ocean heads towards ice-free summers within the next few decades. Because of the role of sea ice in the Earth System such as ocean circulation and ecosystem functioning, reconstructing its past variability is of great importance providing insight into past climate patterns and future climate scenarios. Today, much of our knowledge of past sea-ice variability derives from a relatively few microfossil and biogeochemical tracers, which have limitations, such as preservation biases and low taxonomic resolution. Marine sedimentary ancient DNA (marine sedaDNA) has the potential to capture more of the arctic marine biodiversity compared to other approaches. However, little is known about how well past communities are represented in marine sedaDNA. The transport and fate of DNA derived from sea-ice associated organisms, from surface waters to the seafloor and its eventual incorporation into marine sediment records is poorly understood. Here, we present results from a study applying a combination of methods to examine modern and ancient DNA to material collected along the Northeast Greenland Shelf. We characterized the vertical export of genetic material by amplicon sequencing the hyper-variable V4 region of the 18S rDNA at three water depths, in surface sediments, and in a dated sediment core. The amplicon sequencing approach, as currently applied, includes some limitations for quantitative reconstructions of past changes such as primer competition, PCR errors, and variation of gene copy numbers across different taxa. For these reasons we quantified amplicons from a single species, the circum-polar sea ice dinoflagellate Polarella glacialis in the marine sedaDNA, using digital droplet PCR. The results will increase our understanding on the taphonomy of DNA in sea ice environments, how sedimentation differs among taxonomic groups, and provide indications to potentially useful marine sedaDNA-based proxies for climate and environmental reconstructions.

The Last Glacial Maximum (LGM, 23–19,000 year BP) designates a period of extensive glacial extent and very cold conditions on the Northern Hemisphere. The strength of ocean circulation during this period has been highly debated. Based on investigations of two marine sediment cores from the Davis Strait (1033 m water depth) and the northern Labrador Sea (2381 m), we demonstrate a significant influx of Atlantic-sourced water at both subsurface and intermediate depths during the LGM. Although surface-water conditions were cold and sea-ice loaded, the lower strata of the (proto) West Greenland Current carried a significant Atlantic (Irminger Sea-derived) Water signal, while at the deeper site the sea floor was swept by a water mass comparable with present Northeast Atlantic Deep Water. The persistent influx of these Atlantic-sourced waters entrained by boundary currents off SW Greenland demonstrates an active Atlantic Meridional Overturning Circulation during the LGM. Immediately after the LGM, deglaciation was characterized by a prominent deep-water ventilation event and potentially Labrador Sea Water formation, presumably related to brine formation and/or hyperpycnal meltwater flows. This was followed by a major re-arrangement of deep-water masses most likely linked to increased overflow at the Greenland-Scotland Ridge after ca 15 kyr BP.

The Inuvialuit ancestors, the Thule People, first occupied the northwestern American coasts about 1,000 years ago (Alunik et al., 2003). Today, the harvest of marine resources in the nearshore areas is still of great importance for local communities in terms of subsistence and cultural practices (Usher, 2002). In this context, we undertook a research project with the complementary aims to (1) reconstruct environmental variations in marine waters from the Beaufort Sea continental shelf over the last millennia and (2) disentangle the effects of the recent anthropogenic forcing. To meet these objectives, we used micropaleontological records, mostly based on benthic foraminifers and ostracods, from sediment core PG2303-2/3 retrieved at 43 meters depth in the Herschel Basin, off northern Yukon. The Herschel Basin allowed for continuous accumulation of sediment at a mean rate of 0.3 cm/yr (Pfalz, 2017). The benthic foraminifer concentrations range between 15 and 135 foraminifers/g, with raw counts (>100 specimen) allowing for population analyses. Elphidium clavatum and Cassidulina reniforme dominate the assemblage throughout the record. However, an occurrence peak of Triloculina trihedra at ~1300 CE and an increase of Haynesina nivea, Eoeponidella pulchella, Stainforthia feylingi and Textularia earlandi during the last two centuries mark the record. Ostracods record concentrations ranging between 0 and 9 ostracods/g. The ostracod assemblages are dominated by the euhaline taxa Cytheropteron spp. and Cytheropteron suzdalskyi. Paracyprideis spp., which can tolerate a wide range of salinities, is also abundant, particularly in the ~1800- 1900 CE interval. From these results, we suggest that the last two centuries were marked by important changes in the benthic fauna biodiversity on the Beaufort Sea shelf, with no equivalent since the occupation of the land by the Inuvialuit and their ancestors. Ultimately, this recent change indicates important variations in water mass properties, possibly linked to increase melting of land ice and sea ice in response to Human activities.

In recent decades the surface water temperature and salinity in the Labrador Sea have been influenced by atmospheric circulation patterns, such as the North Atlantic Oscillation (NAO), as well as a trend to increasingly warm atmospheric temperatures in recent years. These changes are concerning, given the important role that temperature and salinity have on deep convection in the Labrador Sea. Yet, due to the shortness of available records, the long-term patterns of climate variability in the region are not clear. Here, a diatom-based reconstruction of summer sea-surface temperature (SST) developed from Trinity Bay, Newfoundland, provides insight into variations of SST since 7.2 cal ka BP in the southwestern Labrador Sea. The results show that the Holocene Thermal Maximum (HTM) lasted until c. 5.2 cal ka BP, which was followed by a gradual cooling trend overprinted by centennial temperature fluctuations of 1–2°C. Long-term cooling was likely the result of declining Northern Hemisphere orbital summer insolation, potentially amplified by long-term changes in surface and bottom water salinity, which led to a gradual reduction in the stratification of the water column. Centennial fluctuations in temperature vary in-phase with reconstructed variations in the NAO, supporting a consistent relationship between atmospheric circulation and SST over centennial-millennial timescales. Other factors influencing the SST variability may have been solar forcing during the mid-Holocene and variations in the strength of the subpolar gyre during the late-Holocene. The most prolonged cool period at 5.2–4.1 cal ka BP coincides with sharply reduced salinity in the Labrador Sea and a weakening of deep ventilation in the northeast Atlantic, highlighting a period with altered ocean surface conditions and circulation across the northern North Atlantic.

Through a process called “bioturbation,” burrowing macrofauna have altered the seafloor habitat and modified global carbon cycling since the Cambrian. However, the impact of macrofauna on the community structure of microorganisms is poorly understood. Here, we show that microbial communities across bioturbated, but geochemically and sedimentologically divergent, continental margin sites are highly similar but differ clearly from those in nonbioturbated surface and underlying subsurface sediments. Solid- and solute-phase geochemical analyses combined with modeled bioturbation activities reveal that dissolved O2 introduction by burrow ventilation is the major driver of archaeal community structure. By contrast, solid-phase reworking, which regulates the distribution of fresh, algal organic matter, is the main control of bacterial community structure. In nonbioturbated surface sediments and in subsurface sediments, bacterial and archaeal communities are more divergent between locations and appear mainly driven by site-specific differences in organic carbon sources., Proceedings of the National Academy of Sciences of the United States of America, 117 (27), ISSN:0027-8424, ISSN:1091-6490

Baffin Bay is a semi-enclosed basin connecting the Arctic Ocean and the western North Atlantic, thus making out a significant pathway for heat exchange. Here we reconstruct the alternating advection of relatively warmer and saline Atlantic waters versus the incursion of colder Arctic water masses entering Baffin Bay through the multiple gateways in the Canadian Arctic Archipelago and the Nares Strait during the Holocene. We carried out benthic foraminiferal assemblage analyses, X-ray fluorescence scanning, and radiocarbon dating of a 738 cm long marine sediment core retrieved from eastern Baffin Bay near Upernavik, Greenland (Core AMD14-204C; 987 m water depth). Results reveal that eastern Baffin Bay was subjected to several oceanographic changes during the last 9.2 kyr. Waning deglacial conditions with enhanced meltwater influxes and an extensive sea-ice cover prevailed in eastern Baffin Bay from 9.2 to 7.9 ka. A transition towards bottom water amelioration is recorded at 7.9 ka by increased advection of Atlantic water masses, encompassing the Holocene Thermal Maximum. A cold period with growing sea-ice cover at 6.7 ka interrupts the overall warm subsurface water conditions, promoted by a weaker northward flow of Atlantic waters. The onset of the neoglaciation at ca. 2.9 ka is marked by an abrupt transition towards a benthic fauna dominated by agglutinated species, likely in part explained by a reduction of the influx of Atlantic Water, allowing an increased influx of the cold, corrosive Baffin Bay Deep Water originating from the Arctic Ocean to enter Baffin Bay through the Nares Strait. These cold subsurface water conditions persisted throughout the Late Holocene, only interrupted by short-lived warmings superimposed on this cooling trend.

The Arctic region exhibits some of the most visible signs of climate change globally. Arctic sea ice extent and volume has been declining sharply in recent decades; observations indicate a mean annual decrease of 3.2% since 1980. However, no extensive network of sea ice observations extends back further than the mid-18th century and satellite data since the late 1970s; this limits perspectives of sea ice variability on longer time scales. Thus, to understand the processes governing sea-ice cover and variability, predict how sea ice and ocean conditions will respond to anthropogenic climate change and to understand if the shrinking of Arctic sea ice is a unique and irreversible process, longer records of sea ice variability and oceanic conditions are required.A multi-proxy approach, involving grain size, geochemical, foraminifera and sedimentary analysis, was applied to a marine sediment core from North East Greenland to reconstruct changes in sea ice extent and palaeoceanographic conditions throughout the early Holocene (ca. 12,400-7,800 cal. yrs. BP). The study aimed to improve the understanding of the interaction between ocean circulation, sea ice and fluctuations of the Zachariae Isstrøm (ZI), one of the main glacier outlets of NE Greenland. Four distinct zones have been identified: Zone 1 (12,400-11,600 cal. yrs. BP) covering the transition from the Younger Dryas into the Holocene which evidences a gradually warming climate, resulting in a retreat of the ZI; Zone 2 (11,600 – 10,300 cal. yrs. BP) which encapsulates two distinct cooling events as a result of cooler surface waters, rapid release of freshwater and local feedback mechanisms. This coincides with sudden re-advances of the ZI followed by gradual retreats; 3) Zone 3 (10,300 – 8,600 cal. yrs. BP) shows warm and stable conditions, with warm surface waters that resulted in the retreat of the ZI; 4) Zone 4 (8,600 – 7,800 cal. yrs. BP) which shows a rapid return to cooler conditions, with cold surface waters and rapid freshwater outbursts resulting in the re-advance of the ZI, forced by decreasing solar insolation and cold surface waters. Our investigation thus indicated that changes in oceanic conditions at the NE Greenland shelf had a significant impact on the extent and melting rate of the ZI glacier.

One of the best methods for studying past climate variability is the analyses of microfossils in sediment cores, especially foraminifera. However, this is highly laborious and time-consuming work. Consequently, several independent endeavors are currently underway with the aim of to automate this procedure, each testing different techniques. Here, we present preliminary results of one of these endeavors that focus on benthic foraminifera from arctic and temperate regions. The study is based on ongoing student projects carried out in collaboration between engineers and geologists. We combine robotics, imaging and machine learning.The project is divided into three stages, with stage 1 and 2 currently ongoing: 1) Robotic separation of foraminiferal specimens from sediment particles, 2) Species classification algorithm based on Convolutional Neural Networks (CNN) including creation of training material. 3) System verification comparing analyses carried out by the automated system and a foraminiferal specialist on the same dataset. Phase 3 has not yet commenced, but initial results of 1 and 2 are available. In time, we hope to be able to build up a database of about 100 different foraminiferal species, which will cover the main assemblages of the coastal regions of the Arctic and Atlantic cold temperate regions.For separating and picking of specimens (1) we have evaluated two different methods using a custom made xyz-platform or a robotic arm. Based on this, it seems that moving the specimens with a robotic arm will work well, but the price of such a robotic arm makes this solution less practical. In contrast, the combination of separating the specimens through shaking the sample in a tray and picking specimens for photographing and analyses using a suction system, with a custom made xyz-platform, is the best solution when considering quality, speed and price. Subsequently, the picked foraminifera/grains are delivered automatically to a digital microscopy system and photographed. So far focus on this part of the process has been developing a precise system for moving and picking, and in the future, we will work towards being able to handle particles of highly variable size in the same sample as well as increasing the speed of the picking and photographing process. For foraminiferal identification (2), parts of the labeling process have been automated using the Django (Python) framework and Amazon Web Services. Also, a number of imaging experiments have been investigated and several Convolutional Neural Network (CNN) algorithms are being developed and tested. In this first test, we include three different benthic foraminiferal species, with very distinct morphologies, as well as various types of clastic grains in approximately the same size fraction as the foraminiferal individuals. In this initial test case only relatively few specimens were included in the database (Ammonia batava - 168 specimens, Elphidium williamsoni - 168 specimens and Quinqueloculina seminulum specimens - 168 specimens as well as 449 clastic grains). Using a customized CNN algorithm, the separation of foraminifera from mineral grains and foraminiferal species identification could be carried out respectively with a precision, recall and F1-score of 94% and 91%.

The Greenland Ice Sheet has been losing mass at an increasing rate over the past decades due to atmospheric and oceanic warming. As a result, freshwater discharge from the Greenland Ice sheet has doubled in the last two decades and is expected to strongly increase in the future, with a large impact on the functioning of coastal marine ecosystems. While glacier runoff delivers nutrients and labile carbon into the fjords, an increase in sediment inputs is expected to have a negative impact in primary productivity, due to increased turbidity and subsequent reduction in available light for photosynthesis. Bridging modern satellite, historical and paleo-records is a key approach, as our capacity to project future scenarios requires an understanding of long-term dynamics, and insight into past warm(er) climate periods that may serve as analogues for the future. We will present results from a master’s project developed within the framework of project GreenShift: Greenland fjord productivity under climate change. Two high-resolution sediment core records from two contrasting fjord systems in NE and SW Greenland were analysed to assess the impact of Greenland Ice Sheet melt on sediment fluxes and primary productivity, focusing on the time period from the Little Ice Age until present. The overall goal of this work is to gain a better understanding of the possible linkages between GIS melt and productivity in Greenland fjord systems, with a view to improve future projections. We followed a multiproxy approach including grain-size distribution, organic carbon and biogenic silica fluxes; and dinoflagellate cyst analyses. Our preliminary results show an overall trend towards sea-surface freshening in recent decades for both fjords influenced by land-terminating (NE) and marine-terminating (SW) glaciers, alongside with important differences both in terms of sedimentary organic composition and dinoflagellate cyst assemblages.

Knowledge of the impact of past climate warming on Greenland Ice Sheet stability is an important issue for assessing thresholds that are critical for a potential ice sheet collapse. For the late Holocene, evidence has recently been found of a so-called 4.2 ka BP event(1) including a prominent warming spike in several ice core records from Greenland and Canada (Agassiz). Also lake records from both Northwest(2) and South Greenland(3) support pronounced summer warming during that time. After c. 4.0 ka BP NW Greenland July air temperature dropped by about 3o C. Coeval with this exceptional atmospheric warming anomaly over northern Canada and parts of Greenland, abrupt cooling and freshening affected the N-Atlantic subpolar gyre where Labrador Sea deep convection ceased(4). Northern N-Atlantic climate generally deteriorated. With our contribution we present Holocene sub-bottom profiling and sedimentary shelf and fjord records from Southwest Greenland and Disko Bay that indicate exceptional Greenland Ice Sheet melting 4.4-4.0 ka BP at a rate and magnitude not recorded since early Holocene deglaciation. Extremely strong melt water discharge resulted in erosion of fjord sediments(5) and local deposition of up to several meters thick meltwater sediment on the shelf(6-8). Timing of this melting event corresponds to a significant anomaly in hydrographic parameters of the Labrador Current off Newfoundland(9,10), which is concluded to have resulted in thermohaline perturbation of the N-Atlantic Subpolar gyre. (1) Weiss, H. 2019. Clim Past doi:10.5194/cp-2018-162-RC2 (2) McFarlin, J.M. et al. 2018. PNAS doi:10.1073/pnas.1720420115 (3) Andresen, C.S. et al. 2004. J Quat Sci 19(8) doi:10.1002/jqs.886 (4) Klus, A. et al. 2018. Clim Past doi:10.5194/cp-14-1165-2018 (5) Ren, J. et al. 2009. Mar Micropal doi:10.1016/j.marmicro.2008.12.003 (6) Hygom Jacobsen, S. 2019. Master Thesis Aarhus Univ, Dept. of Geoscience, pp105 (7) Schneider, R. 2015. Cruise Rep epic.awi.de/id/eprint/37062/131/msm-44-46-expeditionsheft.pdf (8) Kuijpers, A. et al. 2001. Geol. Greenland Surv Bull 189, 41-47 (9) Solignac, S. et al. 2011. The Holocene, doi: 10.1177/0959683610385720 (10) Orme, L. et al 2019. The Holocene (submitted)

Polynyas, areas of open water in the otherwise sea-ice dominated high Arctic, are vital oases for biological productivity, supporting a plethora of marine mammals and birds that in turn sustain indigenous communities. Polynyas are not, however, consistent features. Beyond the observational era, little to nothing is known about their past dynamics and equally, about their resilience to emerging changes in Arctic sea-ice conditions.Recent paleoceanographic reconstructions of the North Water in northern Baffin Bay, the largest of the high Arctic polynyas, indicate that the polynya contracted in response to warm climatic intervals during the Holocene (e.g. Roman Warm Period). In contrast, the onset of stable North Water polynya formation acted to suppress northward incursion of warm Atlantic-sourced waters. This highlighted not only the sensitivity of polynyas to past climatic changes, but the role their formation plays in mediating water column dynamics and ocean circulation.These new findings provided the rationale for the MSCA project ‘POLARC: High Arctic Polynyas in a Changing Climate’, to investigate the Holocene dynamics of other high Arctic polynyas forming off the east Greenland coast. New marine sedimentary archives and a multiproxy approach will be used to reconstruct productivity, sea-ice conditions and bottom water conditions, capturing a holistic view of these systems and their interaction with climatic and oceanographic variation during the Holocene (11,700 years BP to present). We present here preliminary paleoceanographic reconstructions of the Sirius Water, the first Holocene record from this polynya region, as well as plans for model-data comparisons in key polynya regions with the aim of constraining the past and better predicting the future of these phenomena.

As we move towards a “blue” Arctic Ocean in the summer within the next decades, predicting the full range of effects of climate change on the marine arctic environment remains a challenge. This is partly due to the paucity of long-term data on ocean-biosphere-cryosphere interactions over time and partly because, today, much of our knowledge on past ocean variability derives from microfossil and biogeochemical tracers that all have considerable limitations such as preservation biases and low taxonomic resolution or coverage.Recent studies have revealed sedaDNA as a potential “game-changer” in our ability to reconstruct past ocean conditions, due to the preservation of DNA at low temperatures, and the possibility to capture a much larger fraction of the Arctic marine biome diversity than with classical approaches. However, while sedaDNA has been used in terrestrial, archeological, and lake studies for some years, its application to marine sediment records is still in its infancy.Here, we will present new results from material recently collected along the two Arctic Ocean outflow shelves off Greenland (Greenland Sea/Fram Strait and Northern Baffin Bay/Nares Strait). We have used a combination of modern and ancient DNA methods applied to seawater, surface sediments, and sediment cores covering the past ca. 12 000 years with the objectives of: 1) characterizing the vertical export of sea ice-associated genetic material through the water column and into the sediments following sea ice melt and 2) exploring the potential of sedaDNA from the circum-polar sea ice dinoflagellate Polarella glacialis as a new sea ice proxy. For the first objective, we followed a comparative metabarcoding approach while the second objective included designing species-specific primers followed by gene copy number quantification by a droplet digital PCR assay. We argue that sedaDNA will have a critical role in expanding the Paleoceanography “toolbox” and lead to the establishment of a new cross-disciplinary field.

The chemical composition of foraminiferal calcite is widely used for studying past environmental conditions and biogeochemistry. However, high rate of microbial-derived organic matter degradation and abundant dissolved metal sources in sediment and pore waters may impede the application of paleoenvironmental proxies due to formation of secondary carbonates on the outside and/or inside of foraminiferal tests. Secondary carbonate precipitation severely alters the foraminiferal geochemistry and can be difficult to eliminate through standard cleaning procedures for foraminiferal trace element analyses. Here we present results of the mineral composition and formation sequence of diagenetic coatings on the tests of foraminifera formed under extreme anoxic conditions in the Baltic Sea deepest basin (the Landsort Deep, IODP Exp. 347, Site M0063), as well as changing trace element concentrations of authigenic carbonates on the test on a millennial time-scale. The focus is on the diagenetic carbonates present on the tests of the low-oxygen tolerant benthic foraminiferal species Elphidium selseyensis and Elphidium clavatum. We applied geochemical and imaging methods by using scanning electron microscope imaging (SEM) and energy dispersive spectroscopy (EDS), synchrotron-based x-ray fluorescence microscopy (nano-XRF), RAMAN spectroscopy and laser ablation (LA)-ICP-MS, in order to ascertain the sedimentary diagenetic processes, and the foraminiferal authigenic mineral formation sequence. The authigenic carbonates were enriched in Mg, Mn, Fe and Ba, depending on the redox environmental conditions when the authigenic carbonates were precipitated. In particular, concentrations of redox-sensitive elements such as Mn and Fe were increased in bottom waters and sedimentary pore waters under oxygen-depleted conditions in the Landsort Deep, which resulted in Mn- and Fe-enriched carbonate formation. The diagenetic alteration on foraminiferal tests provides potential opportunity to investigate past sedimentary redox environment and primary productivity in the Baltic Sea.