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Arctic climate warming leads to drastic changes in sea ice dynamics, hence impacting primary productivity but also the benthic communities. Therefore, to assess the response of living benthic foraminifera to contrasting Arctic environments, surface sediments from nine stations were collected during the summer of 2014 and fall of 2015 in the Baffin Bay and Nares Strait. Living standing stock are systematically low in the eastern and western Baffin Bay and much higher in the North Water Polynya and the Kane Basin located at the entrance and in the center of Nares Strait, respectively. High living benthic foraminiferal densities in the NOW reflect higher TOC while the highest density in the Kane Basin coincides with lower TOC but higher C/N and higher δ13Corg. The contribution of agglutinated species is on average very high for the whole study area and dominated by the species Adercotryma glomeratum, Lagenammina arenulata, and Reophax scorpiurus. Calcareous species, dominated by Nonionellina labradorica and Melonis barleeanus, are more abundant in the North Water Polynya and the Kane Basin. The very high living standing stock observed in the Kane Basin might be related to the northern position of the ice arch that summer during 2014 and therefore a particularly scarce sea ice cover might have allowed massive phytoplankton production during that season. In this study, the distribution of living benthic foraminifera is discussed according to several environmental parameters such as water masses, phytoplankton productivity, and organic matter fluxes. [ABSTRACT FROM AUTHOR]

Nares Strait and the channels of the Canadian Arctic Archipelago (CAA) act as conduits for sea ice export from the Arctic Ocean but have never been directly compared. Here, we perform such a comparison for both the sea ice area and volume fluxes from October 2016 to December 2021. Nares Strait provided the largest average seasonal (October through September) ice area flux of 95 ± 8 × 103 km2 followed by the CAA regions of the Queen Elizabeth Islands (QEI) at 41 ± 7 × 103 km2 and M'Clure Strait at 2 ± 8 × 103 km2 with corresponding ice volume fluxes of 177 ± 15 km3, 59 ± 10 km3, and 8 ± 8 km3, respectively. Larger Arctic Ocean ice export at Nares Strait was associated with a shorter ice arch duration (237 days) compared to M'Clure Strait (163 days) and QEI (65 days). Seasonal Arctic Ocean ice export was dominated by Nares Strait in 2017–2019 and 2021 but was remarkably exceeded by the QEI in 2020. Large‐scale atmospheric circulation patterns were found to influence the ice area flux in the absence of ice arches but no occurrence of coherent Arctic Ocean ice export events coinciding across all gates were observed. Average net seasonal Arctic Ocean ice area and volume export were 138 × 103 km2 and 245 km3, which represent ∼16% of the area and ∼25% of the volume of sea ice export from Fram Strait. Divergent Arctic Ocean export ice trajectories are apparent for Nares Strait and the QEI when compared to Fram Strait. Plain Language Summary: Sea ice is transported out of the Arctic Ocean via Nares Strait and the channels of the Canadian Arctic Archipelago (CAA) but these export passageways have never been directly compared. Here, we perform such a comparison for both the sea ice area and volume fluxes from October 2016 to December 2021. Nares Strait provided the largest average seasonal fluxes followed by the CAA regions of the Queen Elizabeth Islands (QEI) and M'Clure Strait. Larger Arctic Ocean ice export at Nares Strait was associated less frequent ice arch formation that halts ice export compared to M'Clure Strait and QEI. No occurrence of a large Arctic Ocean ice export event coinciding across all regions was observed. Arctic Ocean ice export was dominated by Nares Strait in 2017–2019 and 2021 but was remarkably exceeded by the QEI in 2020. Under continued warming, Arctic Ocean ice export from Nares Strait and the QEI are expected to increase. Key Points: First comparison of Arctic Ocean ice export between Nares Strait and the CAANo occurrence of large Arctic Ocean ice export events coinciding across all regions was observedSeasonal Arctic Ocean ice volume export from Nares Strait and the CAA together represent ∼25% of the volume export from Fram Strait [ABSTRACT FROM AUTHOR]

Arctic climate warming leads to drastic changes in sea ice dynamics, hence impacting primary productivity but also the benthic communities. Therefore, to assess the response of living benthic foraminifera to contrasting Arctic environments, surface sediments from nine stations were collected during the summer of 2014 and fall of 2015 in the Baffin Bay and Nares Strait. Living standing stock are systematically low in the eastern and western Baffin Bay and much higher in the North Water Polynya and the Kane Basin located at the entrance and in the center of Nares Strait, respectively. High living benthic foraminiferal densities in the NOW reflect higher TOC while the highest density in the Kane Basin coincides with lower TOC but higher C/N and higher δ13Corg. The contribution of agglutinated species is on average very high for the whole study area and dominated by the species Adercotryma glomeratum, Lagenammina arenulata, and Reophax scorpiurus. Calcareous species, dominated by Nonionellina labradorica and Melonis barleeanus, are more abundant in the North Water Polynya and the Kane Basin. The very high living standing stock observed in the Kane Basin might be related to the northern position of the ice arch that summer during 2014 and therefore a particularly scarce sea ice cover might have allowed massive phytoplankton production during that season. In this study, the distribution of living benthic foraminifera is discussed according to several environmental parameters such as water masses, phytoplankton productivity, and organic matter fluxes.

Nares Strait is the long and narrow strait bounded by steep topography that connects the Arctic Ocean's Lincoln Sea to the North Atlantic's Baffin Bay. The winds that blow along the strait play an important role in modulating ice and water exports from the Arctic Ocean as well as in helping to establish the Arctic's largest and most productive polynya that forms at its southern terminus. However, its remote location has limited our knowledge of the winds along the strait. Here we use weather station data from the region as well as two reanalyses and an operational analysis with nominal horizontal resolutions that vary from ∼30 to ∼2.5 km to characterize the wind field in the vicinity of the strait. The strait has a width that varies from ∼40 to ∼100 km and as such the wind field is typically ageostrophic and controlled by the pressure gradient in the along‐strait direction. We show that model resolution plays a role in the representation of both the mean and extreme winds along the strait through the ability to represent this ageostrophic flow. Higher windspeeds occur in the vicinity of Smith Sound and are associated with a left‐hand corner jet. Kane Basin, the widest section of the strait, is characterized by a gradient in windspeed with higher speeds in the center of the basin and lower winds in the eastern basin that is the result of sheltering by the steep topography of the upstream Washington Land peninsula. Key Points: The winds along Nares Strait play an important role in Arctic sea ice export as well as in the formation of the North Water PolynyaThe strait is narrow with steep topography on either side and as a result, the ageostrophic processes play a role in its wind climateModel resolution plays a role in the representation of the ageostrophic mean and extreme winds along the strait [ABSTRACT FROM AUTHOR]

Abstract The discrete element method (DEM) can provide detailed descriptions of sea ice dynamics that explicitly model floes and discontinuities in the ice, which can be challenging to represent accurately with current models. However, floe‐scale stresses that inform lead formation in sea ice are difficult to calculate in current DEM implementations. In this paper, we use the ParticLS software library to develop a DEM that models the sea ice as a collection of discrete rigid particles that are initially bonded together using a cohesive beam model that approximates the response of an Euler‐Bernoulli beam located between particle centroids. Ice fracture and lead formation are determined based on the value of a non‐local Cauchy stress state around each particle and a Mohr‐Coulomb fracture model. Therefore, large ice floes are modeled as continuous objects made up of many bonded particles that can interact with each other, deform, and fracture. We generate particle configurations by discretizing the ice in MODIS satellite imagery into polygonal floes that fill the observed ice shape and extent. The model is tested on ice advecting through an idealized channel and through Nares Strait. The results indicate that the bonded DEM model is capable of qualitatively capturing the dynamic sea ice patterns through constrictions such as ice bridges, arch kinematic features, and lead formation. In addition, we apply spatial and temporal scaling analyses to illustrate the model's ability to capture heterogeneity and intermittency in the simulated ice deformation.

The ice bridge that forms seasonally across Nares Strait impedes the southward transport of sea ice from the Lincoln Sea to Baffin Bay and contributes to the maintenance of the North Water Polynya. Previous studies have quantified how the bridge affects ice export and highlighted a long term decline in the duration of the bridge; however, the specific mechanism by which the bridge forms has remained unstudied. In this study we first used a mix of satellite imagery to refine the timing of formation for the 16 bridges that formed between 2000 and 2021, and subsequently examine the atmospheric and oceanic forcing around these events. It was found that, on average, the ice bridges formed 3 days earlier than reported in previous studies. In general, the bridges formed during periods of cold air temperatures (less than -15°C), around neap tide, and during a cessation or even reversal in the prevailing north-northeasterly winds. Specific quantitative criteria of the environmental conditions favorable for bridge formation are presented and discussed. It was shown, however, that the alignment of these conditions does not always lead to the formation of a bridge, indicating that other factors such as ice thickness and landfast ice stability may limit the formation. A comparison of ice freeboard in Kane Basin between winter 2020 (bridge) and 2019 (no bridge) revealed that the ice pack was thinner in 2019, which may have precluded the formation of the bridge. This is critical as the Arctic ice pack continues to thin. [ABSTRACT FROM AUTHOR]

Nares Strait is a major pathway along which multi-year sea ice leaves the Arctic, an ice class that has seen a recent dramatic reduction in extent. The winds that blow along the strait play an important role in modulating this ice export as well as in establishing the Arctic's largest and most productive polynya, the North Water, that forms at its southern terminus. However, its remote location has limited our knowledge of the winds along the strait. Here we use automatic weather station data from Hans Island, in the middle of the strait, to assess the ability of a set of atmospheric renalyses and analyses with a common lineage but with varying horizontal resolution to represent the variability in the wind field. We find that the flow is highly bidirectional, consistent with topographic channeling, with the highest wind speeds from the north and that a model resolution of ~ 9 km is required to capture the observed variability. The wind field at Hans Island is also found to be representative of variability in the flow along much of Nares Strait. [ABSTRACT FROM AUTHOR]

The mineralogical and geochemical compositions of three sediment cores from the northwestern Greenland continental margin (AMD14‐204 and AMD14‐210) and Kane Basin (AMD14‐Kane2B) were investigated using quantitative X‐ray diffraction and energy‐dispersive X‐ray fluorescence in order to document the impact of ice‐ocean interactions on the sediment provenance and transport pathways during the Holocene. Unmixing of the sediment composition and ratios such as quartz/clays and K/Fe indicate that detrital sediments in cores from the northwest Greenland margin are derived mainly from Prøven granite and reworked Archean gneiss, whereas sediments from Kane Basin are derived mainly from detrital carbonate (Ellesmere Island) and Proterozoic gneiss (Humboldt Glacier). Mineralogical and geochemical signatures also reveal that changes in detrital sediment provenance and transport in the region are strongly interconnected to regional ice stream dynamics, especially during the early Holocene with strong meltwater discharge from the Greenland Ice Sheet associated with the end of deglaciation. With the establishment of milder conditions during the mid‐Holocene and reduced glacial activity once ice sheets retreated inland, sediment inputs via ocean currents became more effective. Thus, detrital proxies in core AMD14‐204, located in the Upernavik cross‐shelf trough, support the hypothesis of an intensification of the West Greenland Current influence after 7.7 cal ka BP, which eventually affected the regional sediment dynamic by a greater contribution from basalt to the sediment supply. Finally, our results suggest that the interactions between climate, glacial dynamics, and surface ocean circulation controlled the paleoenvironmental changes observed in the three cores. Key Points: Sediment provenance is used as indicator of palaeoceanographic changes in northeast Baffin BayDetrital proxies reveal a stronger influence of the West Greenland Current after ~7.7 cal ka BPVariations in sediment provenance on the northwestern margin are interconnected to regional ice streams activity [ABSTRACT FROM AUTHOR]

Petermann Gletscher drains ~4% of the Greenland ice sheet (GrIS) area, with ~80% of its mass loss occurring by basal melting of its ice shelf. We use a high-resolution coupled ocean and sea-ice model with a thermodynamic glacial ice shelf to diagnose ocean-controlled seasonality in basal melting of the Petermann ice shelf. Basal melt rates increase by ~20% in summer due to a seasonal shift in ocean circulation within Nares Strait that is associated with the transition from landfast sea ice to mobile sea ice. Under landfast ice, cold near-surface waters are maintained on the eastern side of the strait and within Petermann Fjord, reducing basal melt and insulating the ice shelf. Under mobile sea ice, warm waters are upwelled on the eastern side of the strait and, mediated by local instabilities and eddies, enter Petermann Fjord, enhancing basal melt down to depths of 200 m. The transition between these states occurs rapidly, and seasonal changes within Nares Strait are conveyed into the fjord within the same season. These results suggest that long-term changes in the length of the landfast sea-ice season will substantially alter the structure of Petermann ice shelf and its contribution to GrIS mass loss.

The North Water (NOW) Polynya is a regularly-forming area of open-water and thin-ice, located between northwestern Greenland and Ellesmere Island (Canada) at the northern tip of Baffin Bay. Due to its large spatial extent, it is of high importance for a variety of physical and biological processes, especially in wintertime. Here, we present a long-term remote sensing study for the winter seasons 1978/1979 to 2014/2015. Polynya characteristics are inferred from (1) sea ice concentrations and brightness temperatures from passive microwave satellite sensors (Advanced Microwave Scanning Radiometer (AMSR-E and AMSR2), Scanning Multichannel Microwave Radiometer (SMMR), Special Sensor Microwave Imager/Sounder (SSM/I-SSMIS)) and (2) thin-ice thickness distributions, which are calculated using MODIS ice-surface temperatures and European Center for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalysis data in a 1D thermodynamic energy-balance model. Daily ice production rates are retrieved for each winter season from 2002/2003 to 2014/2015, assuming that all heat loss at the ice surface is balanced by ice growth. Two different cloud-cover correction schemes are applied on daily polynya area and ice production values to account for cloud gaps in the MODIS composites. Our results indicate that the NOW polynya experienced significant seasonal changes over the last three decades considering the overall frequency of polynya occurrences, as well as their spatial extent. In the 1980s, there were prolonged periods of a more or less closed ice cover in northern Baffin Bay in winter. This changed towards an average opening on more than 85% of the days between November and March during the last decade. Noticeably, the sea ice cover in the NOW polynya region shows signs of a later-appearing fall freeze-up, starting in the late 1990s. Different methods to obtain daily polynya area using passive microwave AMSR-E/AMSR2 data and SSM/I-SSMIS data were applied. A comparison with MODIS data (thin-ice thickness ≤ 20 cm) shows that the wintertime polynya area estimates derived by MODIS are about 30 to 40% higher than those derived using the polynya signature simulation method (PSSM) with AMSR-E data. In turn, the difference in polynya area between PSSM and a sea ice concentration (SIC) threshold of 70% is fairly low (approximately 10%) when applied to AMSR-E data. For the coarse-resolution SSM/I-SSMIS data, this difference is much larger, particularly in November and December. Instead of a sea ice concentration threshold, the PSSM method should be used for SSM/I-SSMIS data. Depending on the type of cloud-cover correction, the calculated ice production based on MODIS data reaches an average value of 264.4 ± 65.1 km 3 to 275.7 ± 67.4 km 3 (2002/2003 to 2014/2015) and shows a high interannual variability. Our achieved long-term results underline the major importance of the NOW polynya considering its influence on Arctic ice production and associated atmosphere/ocean processes.

Abstract: A semianalytic two‐dimensional model is used to analyze the interplay between the different forces acting on density‐driven flow in high‐latitude channels. In particular, the balance between wind stress, viscous forces, baroclinicity, and sea surface slope adjustments under specified flux conditions is examined. Weak winds are found not to change flow patterns appreciably, with minimal (<7%) adjustments to horizontal velocity maxima. In low‐viscosity regimes, strong winds change the flow significantly, especially at the surface, by either strengthening the dual‐jet pattern, established without wind, by a factor of 2–3 or initiating return flow at the surface. A nonzero flux does not result in the addition of a uniform velocity throughout the channel cross section, but modifies both along‐channel and cross‐channel velocities to become more symmetric, dominated by a down‐channel jet centered in the domain and counter‐clockwise lateral flow. We also consider formulations of the model that allow adjustments of the net flux in response to the wind. Flow patterns change, beyond uniform intensification or weakening, only for strong winds and high Ekman number. Comparisons of the model results to observational data collected in Nares Strait in the Canadian Archipelago in the summer of 2007 show rough agreement, but the model misses the upstream surface jet on the east side of the strait and propagates bathymetric effects too strongly in the vertical for this moderately high eddy viscosity. Nonetheless, the broad strokes of the observed high‐latitude flow are reproduced. [ABSTRACT FROM AUTHOR]

Abstract: Based on a 2 year data set, the eastern Canadian Arctic Archipelago and Baffin Bay appear to be a modest summertime sink of atmospheric CO2. We measured surface water CO2 partial pressure (pCO2), salinity, and temperature throughout northern Baffin Bay, Nares Strait, and Lancaster Sound from the CCGS Amundsen during its 2013 and 2014 summer cruises. Surface water pCO2 displayed considerable variability (144–364 μatm) but never exceeded atmospheric concentrations, and average calculated CO2 fluxes in 2013 and 2014 were −12 and −3 mmol C m−2 d−1 (into the ocean), respectively. Ancillary measurements of chlorophyll a reveal low summertime productivity in surface waters. Based on total alkalinity and stable oxygen isotopes (δ18O) data, a strong riverine signal in northern Nares Strait coincided with relatively high surface pCO2, whereas areas of sea‐ice melt occur with low surface pCO2. Further assessments, extending the seasonal observation period, are needed to properly constrain both seasonal and annual CO2 fluxes in this region. [ABSTRACT FROM AUTHOR]

This paper presents a first implementation of a new rheological model for sea ice on geophysical scales. This continuum model, called Maxwell elasto-brittle (Maxwell-EB), is based on a Maxwell constitutive law, a progressive damage mechanism that is coupled to both the elastic modulus and apparent viscosity of the ice cover and a Mohr-Coulomb damage criterion that allows for pure (uniaxial and biaxial) tensile strength. The model is tested on the basis of its capability to reproduce the complex mechanical and dynamical behaviour of sea ice drifting through a narrow passage. Idealized as well as realistic simulations of the flow of ice through Nares Strait are presented. These demonstrate that the model reproduces the formation of stable ice bridges as well as the stoppage of the flow, a phenomenon occurring within numerous channels of the Arctic. In agreement with observations, the model captures the propagation of damage along narrow arch-like kinematic features, the discontinuities in the velocity field across these features dividing the ice cover into floes, the strong spatial localization of the thickest, ridged ice, the presence of landfast ice in bays and fjords and the opening of polynyas downstream of the strait. The model represents various dynamical behaviours linked to an overall weakening of the ice cover and to the shorter lifespan of ice bridges, with implications in terms of increased ice export through narrow outflow pathways of the Arctic. [ABSTRACT FROM AUTHOR]

Petermann Gletscher drains ~4% of the Greenland ice sheet (GrIS) area, with ~80% of its mass loss occurring by basal melting of its ice shelf. We use a high-resolution coupled ocean and sea-ice model with a thermodynamic glacial ice shelf to diagnose ocean-controlled seasonality in basal melting of the Petermann ice shelf. Basal melt rates increase by ~20% in summer due to a seasonal shift in ocean circulation within Nares Strait that is associated with the transition from landfast sea ice to mobile sea ice. Under landfast ice, cold near-surface waters are maintained on the eastern side of the strait and within Petermann Fjord, reducing basal melt and insulating the ice shelf. Under mobile sea ice, warm waters are upwelled on the eastern side of the strait and, mediated by local instabilities and eddies, enter Petermann Fjord, enhancing basal melt down to depths of 200 m. The transition between these states occurs rapidly, and seasonal changes within Nares Strait are conveyed into the fjord within the same season. These results suggest that long-term changes in the length of the landfast sea-ice season will substantially alter the structure of Petermann ice shelf and its contribution to GrIS mass loss. [ABSTRACT FROM AUTHOR]

Over the last 60 years, the perception of the Arctic Ocean has changed from a hostile, sluggish, steady, ice-covered environment with little global impact to an ocean that has become increasingly accessible, apparently rapidly changing, only partly ice-covered, and connected to the global meridional overturning circulation. Our new observations demonstrate that waters off Northwest Greenland constitute the final limb in the grand cyclonic circulation of the Atlantic layer in the Arctic Ocean. These waters with an Atlantic water mass signature are warming in Nares Strait to the west of Greenland as they are elsewhere. Estimates of the magnitude and uncertainty of this warming are emerging from both moored observations and historical hydrographic station data.Ocean temperatures sensed by instruments moored 3 m above the bottom between 228 and 366 m depth in Nares Strait suggest a mean warming of about 0.023 ± 0.015°C per year for the 2003–2009 period at 95% confidence. Salinity changes for the same period are not significantly different from zero. Nevertheless, oscillating bottom temperatures covary with salinities. Mean bottom salinities in Nares Strait exceed 34.56 psu while no water with salinities above 34.51 psu occurs in Baffin Bay to the south. These data indicate a dominantly northern source for the waters sensed by our moorings. Mean bottom temperatures hover near 0°C, which suggests minimal influence of waters from the northeastern Amundsen Basin in the Arctic Ocean. Thus, we conclude that the observed warming originates from the northeastern Canadian Basin to the southwest of our study area.In addition to these mean conditions, we find large interannual variability. For example, significant freshening emerges for the 2003–2006 period that reaches –0.02 ± 0.008 psu per year without significant concurrent temperature trends at three sensor locations. These data contrast with the 2007–2009 observational period when five different sensors all indicate warmer waters (0.063 ± 0.017°C per year) and saltier waters (0.027 ± 0.01 psu per year), which reverses the 2003–2006 freshening. We speculate that some of these observed changes are caused by a changing ice regime. During the 2003–2006 winters, ice was landfast, while during 2007–2009 it was generally mobile year-round. The warming impacts tidewater glaciers along northern Greenland with sill depths below 300 m, for example, Petermann Gletscher.

Retreat of glacier ice from Nares Strait and other straits in the Canadian Arctic Archipelago after the end of the last Ice Age initiated an important connection between the Arctic and the North Atlantic Oceans, allowing development of modern ocean circulation in Baffin Bay and the Labrador Sea. As low-salinity, nutrient-rich Arctic Water began to enter Baffin Bay, it contributed to the Baffin and Labrador currents flowing southward. This enhanced freshwater inflow must have influenced the sea ice regime and likely is responsible for poor calcium carbonate preservation that characterizes the Baffin Island margin today. Sedimentologic and paleoceanographic data from radiocarbon-dated core HLY03-05GC, Hall Basin, northern Nares Strait, document the timing and paleoenvironments surrounding the retreat of waning ice sheets from Nares Strait and opening of this connection between the Arctic Ocean and Baffin Bay. Hall Basin was deglaciated soon before 10,300 cal BP (calibrated years before present) and records ice-distal sedimentation in a glacial bay facing the Arctic Ocean until about 9,000 cal BP. Atlantic Water was present in Hall Basin during deglaciation, suggesting that it may have promoted ice retreat. A transitional unit with high ice-rafted debris content records the opening of Nares Strait at approximately 9,000 cal BP. High productivity in Hall Basin between 9,000 and 6,000 cal BP reflects reduced sea ice cover and duration as well as throughflow of nutrient-rich Pacific Water. The later Holocene is poorly resolved in the core, but slow sedimentation rates and heavier carbon isotope values support an interpretation of increased sea ice cover and decreased productivity during the Neoglacial period.

The crustal structure and continental margin between southern Nares Strait and northern Baffin Bay were studied based on seismic refraction and gravity data acquired in 2010. We present the resulting P wave velocity, density and geological models of the crustal structure of a profile, which extends from the Greenlandic margin of the Nares Strait into the deep basin of central northern Baffin Bay. For the first time, the crustal structure of the continent-ocean transition of the very northern part of Baffin Bay could be imaged. We divide the profile into three parts: continental, thin oceanic, and transitional crust. On top of the three-layered continental crust, a low-velocity zone characterizes the lowermost layer of the three-layered Thule Supergroup underneath Steensby Basin. The 4.3–6.3 km thick oceanic crust in the southern part of the profile can be divided into a northern and southern section, more or less separated by a fracture zone. The oceanic crust adjacent to the continent-ocean transition is composed of 3 layers and characterized by oceanic layer 3 velocities of 6.7–7.3 km/s. Toward the south only two oceanic crustal layers are necessary to model the travel time curves. Here, the lower oceanic crust has lower seismic velocities (6.4–6.8 km/s) than in the north. Rather low velocities of 7.7 km/s characterize the upper mantle underneath the oceanic crust, which we interpret as an indication for the presence of upper mantle serpentinization. In the continent-ocean transition zone, the velocities are lower than in the adjacent continental and oceanic crustal units. There are no signs for massive magmatism or the existence of a transform margin in our study area. [ABSTRACT FROM AUTHOR]

A fold-and-thrust belt developed between Greenland and Svalbard during the Palaeogene, with an associated foreland basin forming in what is now Spitsbergen. This Central Basin is comprised of the Van Mijenfjorden Group, a ~2.3 km thick sandstone-shale dominated succession that contains prominent and laterally continuous bentonite layers in the lower formations. These altered tephra layers can be used as stratigraphic markers that connect the basin development with regional explosive volcanism and changes to relative plate motions. We sampled and analysed bentonites from nine borehole cores across the Central Basin. Each layer shows evidence of alteration, with mobile elements such as alkali and alkali earth metals particularly disrupted. However, immobile elements including rare earth elements (REE) and preserved igneous minerals retain a magmatic signature, allowing for comparisons with potential volcanic sources to be made. The majority of bentonites are both evolved and strongly alkaline, with chemical signatures that are much closer to the continental rift events around Ellesmere Island and North Greenland than to the early activity of the North Atlantic Igneous Province (NAIP). There is a clear difference between tephra layers in the mid Palaeocene versus late Palaeocene strata. The early bentonites have a REE signature comparable to the volcanics of the Kap Washington Group exposed in North Greenland. The later bentonites have likely come from volcanic centres in the Nares Strait that are also the source of abundant volcaniclastic sediments in the Judge Daly Promontory, Ellesmere Island. These findings suggest that a mid to late Palaeocene change in locus of volcanic provenance may reflect changes in relative plate motions related to the formation of the West Spitsbergen fold-and-thrust belt and the emplacement of the NAIP. However, the lack of bentonites matching NAIP sources suggests that explosive volcanism was of insufficient magnitude to lead to deposition in the Central Basin at this time. [ABSTRACT FROM AUTHOR]

Recent peripheral thinning of the Greenland Ice Sheet is partly offset by interior thickening and is overprinted on its poorly constrained Holocene evolution. On the basis of the ice sheet's radiostratigraphy, ice flow in its interior is slower now than the average speed over the past nine millennia. Generally higher Holocene accumulation rates relative to modern estimates can only partially explain this millennial-scale deceleration. The ice sheet's dynamic response to the decreasing proportion of softer ice from the last glacial period and the deglacial collapse of the ice bridge across Nares Strait also contributed to this pattern. Thus, recent interior thickening of the Greenland Ice Sheet is partly an ongoing dynamic response to the last deglaciation that is large enough to affect interpretation of its mass balance from altimetry. [ABSTRACT FROM AUTHOR]

Time series observations of velocity, salinity, pressure, and ice draft provide estimates of advective fluxes in Nares Strait from 2003 to 2009 at daily to interannual time scales. Velocity and salinity are integrated across the 36-km-wide and 350-m-deep channel for two distinct multiyear periods of sea ice cover. These observations indicate multiyear mean fluxes that range from 0.71 ± 0.09 to 1.03 ± 0.11 Sverdrups (Sv; 1 Sv ≡ 106 m3 s−1 = 31 536 km3 yr−1) for volume and from 32 ± 5.7 to 54 ± 9.3 mSv (1 mSv ≡ 103 m3 s−1) for oceanic freshwater relative to a salinity of 34.8 for the first (2003-06) and second (2007-09) periods, respectively. Advection of ice adds another 8 ± 2 mSv or 260 ± 70 km3 yr−1 to the freshwater export. Flux values are larger when the sea ice is mobile all year. About 75% of the oceanic volume and freshwater flux variability is correlated at daily to interannual time scales. Flux variability peaks at a 20-day time scale and correlates strongly with along-channel pressure gradients ( r2 = 0.68). The along-channel pressure gradient peaks in early spring when the sea ice is often motionless with higher sea level in the Arctic that drives the generally southward ocean circulation. Local winds contribute only when the sea ice is mobile, when they explain 60% of its variance ( r2 = 0.60). Observed annual to interannual change in the duration of motionless sea ice conditions impacts ocean stratification and freshwater flux, while seasonal variations are small. [ABSTRACT FROM AUTHOR]

The North Water (NOW) Polynya is a regularly-forming area of open-water and thin-ice, located between northwestern Greenland and Ellesmere Island (Canada) at the northern tip of Baffin Bay. Due to its large spatial extent, it is of high importance for a variety of physical and biological processes, especially in wintertime. Here, we present a long-term remote sensing study for the winter seasons 1978/1979 to 2014/2015. Polynya characteristics are inferred from (1) sea ice concentrations and brightness temperatures from passive microwave satellite sensors (Advanced Microwave Scanning Radiometer (AMSR-E and AMSR2), Scanning Multichannel Microwave Radiometer (SMMR), Special Sensor Microwave Imager/Sounder (SSM/I-SSMIS)) and (2) thin-ice thickness distributions, which are calculated using MODIS ice-surface temperatures and European Center for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalysis data in a 1D thermodynamic energy-balance model. Daily ice production rates are retrieved for each winter season from 2002/2003 to 2014/2015, assuming that all heat loss at the ice surface is balanced by ice growth. Two different cloud-cover correction schemes are applied on daily polynya area and ice production values to account for cloud gaps in the MODIS composites. Our results indicate that the NOW polynya experienced significant seasonal changes over the last three decades considering the overall frequency of polynya occurrences, as well as their spatial extent. In the 1980s, there were prolonged periods of a more or less closed ice cover in northern Baffin Bay in winter. This changed towards an average opening on more than 85% of the days between November and March during the last decade. Noticeably, the sea ice cover in the NOW polynya region shows signs of a later-appearing fall freeze-up, starting in the late 1990s. Different methods to obtain daily polynya area using passive microwave AMSR-E/AMSR2 data and SSM/I-SSMIS data were applied. A comparison with MODIS data (thin-ice thickness ≤ 20 cm) shows that the wintertime polynya area estimates derived by MODIS are about 30 to 40% higher than those derived using the polynya signature simulation method (PSSM) with AMSR-E data. In turn, the difference in polynya area between PSSM and a sea ice concentration (SIC) threshold of 70% is fairly low (approximately 10%) when applied to AMSR-E data. For the coarse-resolution SSM/I-SSMIS data, this difference is much larger, particularly in November and December. Instead of a sea ice concentration threshold, the PSSM method should be used for SSM/I-SSMIS data. Depending on the type of cloud-cover correction, the calculated ice production based on MODIS data reaches an average value of 264.4 ± 65.1 km³ to 275.7 ± 67.4 km³ (2002/2003 to 2014/2015) and shows a high interannual variability. Our achieved long-term results underline the major importance of the NOW polynya considering its influence on Arctic ice production and associated atmosphere/ocean processes. [ABSTRACT FROM AUTHOR]

Abstract: The Lincoln Sea is a bifurcation point, where waters from the Canadian and Eurasian Basins flow to Nares or Fram Strait. Mechanisms that control which waters are found in the Lincoln Sea, and on its continental shelves, are unknown. Using conductivity–temperature–depth (CTD; from hydrographic and ice-tethered profiler surveys), nutrient, and mooring data with the DRAKKAR global 3-D coupled ocean/sea-ice model, the Lincoln Sea was examined from 1991 to 2012. Although both Pacific and Atlantic waters were observed on the North Ellesmere and North Greenland shelves, Atlantic water was shallower on the North Greenland shelf. Thus, deeper than 125m, water was warmer and saltier on the North Greenland shelf than the North Ellesmere shelf. Three different water types were identified on the North Ellesmere shelf – waters from the Canadian Basin were observed 1992, 1993, 1996, 2005, and 2012, waters from both the Canadian and Eurasian Basins were observed in 2003, 2004, and 2008, and waters with no temperature minima or maxima below the surface mixed layer were observed in 1991, 2006, 2009, and 2010. Mixing with vertical advection speeds of 1×10−4 ms−1 were observed on the continental slope and this mixing could cause the disappearance of the temperature maxima. Model results suggest that currents on the North Ellesmere shelf were weak (less than 10cms−1), baroclinic, and directed away from Nares Strait while currents on the North Greenland shelf were stronger (less than 15cms−1), and primarily directed towards Nares Strait. CTD, mooring, and model results suggest that the water advected to Nares Strait is primarily from the North Greenland shelf while water on the North Ellesmere shelf is advected westward. [Copyright &y& Elsevier]

The North Water (NOW) polynya is an area of ocean between Greenland and Ellesmere Island that does not freeze completely during the winter months. The northern border of the polynya is typically demarked by an ice arch that forms across the narrow head of Smith Sound during winter. Once the ice arch consolidates, winds and current advect ice to the south, allowing the formation of new ice. The ice arch generally breaks down in late spring, at which point floes enter the region from the Arctic Ocean via Nares Strait. In 2009, the Smith Sound ice arch did not consolidate, but another ice arch formed 500 km to the north at the junction of Nares Strait and the Arctic Ocean. This northern ice arch prevented floes from reaching the NOW until 23 July and led to decadal low ice coverage for the region. In July, satellite-derived sea surface temperatures (SSTs) reached 8–10°C, which is approximately 5°C above typical seasonal values. With the introduction of floes into the NOW after 23 July, SSTs began to moderate. [ABSTRACT FROM AUTHOR]

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Many workers continue to model Nares Strait between Greenland and Ellesmere Island, Canada, as a plate boundary and locus of major Cenozoic compression and strike-slip, marked by the postulated Wegener (transform) Fault. This, despite continuity of Precambrian-Paleozoic provinces across the seaway including an undeformed Neoproterozoic mafic dyke swarm that crosses at a high angle. As a test of the speculative plate kinematic modelling, apatite fission track (AFT) dating was undertaken along a transect across the Paleoproterozoic shield of Smith Sound, at the south end of Nares Strait, running from sea level to ca. 600 m elevation and as much as 70 km inland on both sides. The shield is overlain by three sedimentary basins separated by major hiatuses. The AFT ages fall into two groups: 282 ± 34 and 650 ± 51 Ma. They indicate maximum depth was >4 km in the lower Paleozoic from both coasts to 50 km inland, and at >50 km inland temperatures were below the annealing interval throughout Phanerozoic time. During the past ca. 280 million years, the rocks of both age groups suffered only minor displacements. The ages form an unbroken, harmonious pattern along the transect with no evidence of thermotectonism since the Permo-Carboniferous. These quantitative data support the field mapping that demonstrates Smith Sound and environs constitute an intact crustal block unaffected by lithospheric fracturing. Nares Strait is not the site of a plate boundary. The Wegener Fault does not exist. [ABSTRACT FROM AUTHOR]

Abstract: A three dimensional coupled ocean (HYCOM) and sea ice model (CICE) is applied to a regional setup of the Lincoln Sea, the Nares Strait, and the Baffin Bay. As the sea ice model is originally developed for global simulations, boundary conditions have been implemented for the regional setup. The model results are compared with satellite images and with the large scale simulation that is specified for the boundary conditions. The main focus in this paper is on the simulated variations in the modeled sea ice flux and oceanic volume flux through the Nares Strait in the period September 2005–August 2008. The total sea ice area flux in 2006 is 14×103 km2/year and in 2007 it is 69×103 km2/year. The reason for this difference is mainly the blocking of the ice flow in the Nares Strait in spring 2006. The corresponding volume fluxes are 20km3/year and 120km3/year. The average annual oceanic volume flux varies from 0.6Sv to 1.3Sv from 2006 to 2008. The freshwater flux with a reference salinity of 34.8 varies in the same period from 12mSv to 29mSv. The opening and closing of the North Water, which is one of the largest polynyas in the world, are investigated. A February storm event with opening and refreezing of the North Water is well reproduced. The model results show that the net heat flux in the polynya area at the surface is positive into the ocean from May until the end of July, and hence while the wind is responsible for opening the polynya, the main mechanism for maintaining the polynya in late spring and early summer is the surface heat flux. [ABSTRACT FROM AUTHOR]

Paleogene sediments in fault-bounded basins on Judge Daly Promontory, northeast Ellesmere Island, Canadian High Arctic, are rich in volcanogenic material. Volcanic pebbles within the Cape Back basin near Nares Strait were studied for their petrography, geochemistry, Sr and Nd isotopes, and geochronology to identify and characterize their parent rock. The pebbles are derived from lava flows and ignimbrites of a continental rift-related, strongly differentiated, highly incompatible element enriched, alkaline volcanic suite, the proposed Nares Strait volcanic suite, which is distinct from other alkaline volcanic suites on the northern coasts of Ellesmere Island and Greenland. 40Ar/39Ar amphibole and alkali feldspar ages indicate that volcanism was active around 61–58 Ma and was probably contemporaneous with sedimentation resulting in Middle to Late Paleocene age for deposition within the Cape Back basin and the other Paleogene basins on Judge Daly Promontory. [ABSTRACT FROM AUTHOR]

The Arctic Ocean is an important link in the global hydrological cycle, storing freshwater and releasing it to the North Atlantic Ocean in a variable fashion as pack ice and freshened seawater. An unknown fraction of this return flow passes through Nares Strait between northern Canada and Greenland. Surveys of ocean current and salinity in Nares Strait were completed in the summer of 2003. High-resolution data acquired by ship-based acoustic Doppler current profiler and via hydrographic casts revealed subtidal volume and freshwater fluxes of 0.8 ± 0.3 Sv and –25 ± 12 mSv (Sv = 103 mSv = 106 m3 s-1), respectively. The observations resolved the dominant spatial scale of variability, the internal Rossby radius of deformation (LD ∼9 km), and revealed a complex, yet coherent along-channel flow with a Rossby number of about 0.13, close to geostrophic balance. Approximately one-third of the total volume flux was associated with across-channel slope of the sea surface and two-thirds (68%) with across-channel slope of isopycnal surfaces. During the period of observation, sustained wind from the southwest weakened the average down-channel flow at the surface. The speed of tidal currents exceeded subtidal components by a factor of 2. Tidal signals were resolved and removed from the observations here using two independent methods resolving horizontal and vertical variability of tidal properties, respectively. Tidal current predictions from a barotropic model agreed well with depth-averaged observations in both amplitude and phase. However, because estimates of freshwater flux require accurate surface currents (and salinity), a least squares fitting procedure using velocity data was judged more reliable, since it permits quantification of vertical tidal current variations. [ABSTRACT FROM AUTHOR]

Abstract: The “Nares Strait problem” represents a debate about the existence and magnitude of left-lateral movements along the proposed Wegener Fault within this seaway. Study of Palaeogene Eurekan tectonics at its shorelines could shed light on the kinematics of this fault. Palaeogene (Late Paleocene to Early Eocene) sediments are exposed at the northeastern coast of Ellesmere Island in the Judge Daly Promontory. They are preserved as elongate SW–NE striking fault-bounded basins cutting folded Early Paleozoic strata. The structures of the Palaeogene exposures are characterized by broad open synclines cut and displaced by steeply dipping strike-slip faults. Their fold axes strike NE–SW at an acute angle to the border faults indicating left-lateral transpression. Weak deformation in the interior of the outliers contrasts with intense shearing and fracturing adjacent to border faults. The degree of deformation of the Palaeogene strata varies markedly between the northwestern and southeastern border faults with the first being more intense. Structural geometry, orientation of subordinate folds and faults, the kinematics of faults, and fault-slip data suggest a multiple stage structural evolution during the Palaeogene Eurekan deformation: (1) The fault pattern on Judge Daly Promontory is result of left-lateral strike-slip faulting starting in Mid to Late Paleocene times. The Palaeogene Judge Daly basin formed in transtensional segments by pull-apart mechanism. Transpression during progressive strike-slip shearing gave rise to open folding of the Palaeogene deposits. (2) The faults were reactivated during SE-directed thrust tectonics in Mid Eocene times (chron 21). A strike-slip component during thrusting on the reactivated faults depends on the steepness of the fault segments and on their obliquity to the regional stress axes. Strike-slip displacement was partitioned to a number of sub-parallel faults on-shore and off-shore. Hence, large-scale lateral movements in the sum of 80–100 km or more could have been accommodated by a set of faults, each with displacements in the order of 10–30 km. The Wegener Fault as discrete plate boundary in Nares Strait is replaced by a bundle of faults located mainly onshore on the Judge Daly Promontory. [Copyright &y& Elsevier]

Copyright of Atmosphere - Ocean (Canadian Meteorological & Oceanographic Society) is the property of Canadian Meteorological & Oceanographic Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Atmosphere - Ocean (Canadian Meteorological & Oceanographic Society) is the property of Canadian Meteorological & Oceanographic Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In 2002, oceanographers began a study of Arctic freshwater export via Nares Strait (Münchow et al., 2006). This 550 km channel separating Greenland from Canada is possibly the longest narrow waterway on Earth. Surrounding ice-capped terrain rises above 2000 m. We used the US icebreaker Healy to install recording instruments on submerged moorings in summer in 2003, but planned their recovery in 2005 via an ice camp in spring, because the dangerous fast moving pack ice of summer makes ship-based recoveries difficult.

Investigates the cosmogenic chlorine that accumulated in the bedrock within the Nares Strait, Greenland to determine the time of which the rocks were exposed to the atmosphere. Blockade of the strait by ice during the last glaciation; Determination of the age of deglaciation of the strait.