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Upper-atmosphere winds from a meteor radar and a field-widened Michelson interferometer, co-located at the Polar Environment Atmospheric Research Laboratory in Eureka, Nunavut, Canada (80° N, 86° W) are compared. The two instruments implement different wind-measuring techniques at similar heights and have very different temporal and spatial observational footprints. The meteor radar provides winds averaged over a ∼ 300 km horizontal area in 3 km vertical bins between 82 and 97 km on a 1 h cadence. The E-Region Wind Interferometer II (ERWIN) provides airglow-weighted winds (averaged over volumes of ∼ 8 km in height by ∼ 5 km radius) from three nightglow emissions (O(1S) , oxygen green line, 557.7 nm , 97 km ; an O2 line, 866 nm , 94 km ; and an OH line, 843 nm , 87 km) on a ∼ 5 min cadence. ERWIN's higher precision (1–2 ms-1 for the O(1S) and OH emissions and ∼ 4 ms-1 for the O2 emissions) and higher cadence allows more substantive comparisons between winds measured by meteor radar and Doppler shifts in airglow emissions than previously possible for similar meteor radar/airglow Doppler shift comparisons using Fabry–Perot interferometers. The best correlation is achieved using Gaussian weighting of meteor radar winds with peak height and vertical width being optimally determined. Peak heights agree well with co-located SABER airglow observations. Offsets between the two instruments are ∼ 1–2 ms-1 for the O2 and O(1S) emissions and less than 0.3 ms-1 for the OH emission. Wind directions are highly correlated with a ∼ 1:1 correspondence. On average, meteor radar wind magnitudes are ∼ 40 % larger than those from ERWIN. Gravity wave airglow brightness weighting of observations is discussed. Non-quadrature phase offsets between the airglow weighting and gravity wave associated wind and temperature perturbations will result in enhanced or reduced layer-weighted wind amplitudes. [ABSTRACT FROM AUTHOR]

This study explores the role of snowpack in polar boundary layer chemistry, especially as a direct source of reactive bromine (BrOx = BrO + Br) and nitrogen (NOx = NO + NO2) in the Arctic springtime. Surface snow samples were collected daily from a Canadian high Arctic location at Eureka, Nunavut (80° N, 86° W) from the end of February to the end of March in 2018 and 2019. The snow was sampled at several sites representing distinct environments: sea ice, inland close to sea level, and a hilltop ∼ 600 m above sea level (a.s.l.). At the inland sites, surface snow salinity has a double-peak distribution with the first and lowest peak at 0.001–0.002 practical salinity unit (psu), which corresponds to the precipitation effect, and the second peak at 0.01–0.04 psu , which is likely related to the salt accumulation effect (due to loss of water vapour by sublimation). Snow salinity on sea ice has a triple-peak distribution; its first and second peaks overlap with the inland peaks, and the third peak at 0.2–0.4 psu is likely due to the sea water effect (a result of upward migration of brine). At all sites, snow sodium and chloride concentrations increase by almost 10-fold from the top 0.2 to ∼ 1.5 cm. Surface snow bromide at sea level is significantly enriched, indicating a net sink of atmospheric bromine. Moreover, surface snow bromide at sea level has an increasing trend over the measurement period, with mean slopes of 0.024 µMd-1 in the 0–0.2 cm layer and 0.016 µMd-1 in the 0.2–0.5 cm layer. Surface snow nitrate at sea level also shows a significant increasing trend, with mean slopes of 0.27, 0.20, and 0.07 µMd-1 in the top 0.2, 0.2–0.5, and 0.5–1.5 cm layers, respectively. Using these trends, an integrated net deposition flux of bromide of (1.01 ± 0.48) × 10 7 molec.cm-2s-1 and an integrated net deposition flux of nitrate of (2.6 ± 0.37) × 10 8 molec.cm-2s-1 were derived. In addition, the surface snow nitrate and bromide at inland sites were found to be significantly correlated (R = 0.48–0.76) with the [NO3-]/[Br-] ratio of 4–7 indicating a possible acceleration effect of reactive bromine in atmospheric NOx -to-nitrate conversion. This is the first time such an effect has been seen in snow chemistry data obtained with a sampling frequency as short as 1 d. BrO partial column (0–4 km) data measured by MAX-DOAS show a decreasing trend in early spring, which generally agrees with the derived surface snow bromide deposition flux indicating that bromine in Eureka atmosphere and surface snow did not reach a photochemical equilibrium state. Through mass balance analysis, we conclude that the average release flux of reactive bromine from snow over the campaign period must be smaller than the derived bromide deposition flux of ∼ 1 × 10 7 molec.cm-2s-1. Note that the net mean fluxes observed do not completely rule out larger bidirectional fluxes over shorter timescales. [ABSTRACT FROM AUTHOR]

Northwestern Baffin Island, Nunavut, Canada, preserves the stratigraphic record in the northern margin of the Foxe Basin. The Ordovician succession exposed on an unnamed peninsula west of Steensby Inlet, northwestern Baffin Island includes the Lower and Middle Ordovician Ship Point Formation and Upper Ordovician Frobisher Bay and Amadjuak formations. Nearly 7000 conodont specimens recovered from six sections on this peninsula allow the establishment of seven conodont zones throughout this succession: Rossodus manitouensis Taxon-range Zone, Acodus deltatus–Oneotodus costatus Assemblage Zone, Oepikodus communis Interval Zone, and Cooperignathus aranda–Jumudontus gananda Assemblage Zone in units 2 and 3 of the Ship Point Formation, correlative to the upper Tremadocian and Floian, Lower Ordovician; Phragmodus polonicus Taxon-range Zone confined to unit 4 of the Ship Point Formation, correlative to the middle Darriwilian, Middle Ordovician; and Appalachignathus delicatuluss–Belodina confluens and Belodina confluens–Periodon grandis Assemblage zones limited to the Frobisher Bay and Amadjuak formations, respectively, correlative to the lower Katian, Upper Ordovician. The establishment of these conodont zones proves that (1) the Ship Point Formation in the Foxe Basin is not a continuous stratigraphic unit but has a stratigraphic interval missing that is assignable to the Dapingian and lower Darriwilian, Middle Ordovician; (2) the base of the Ship Point Formation is diachronous in the Foxe Basin, which is correlated to the upper Tremadocian on northwestern Baffin Island but to the upper Floian on Melville Peninsula; and (3) the strata younger than lower Amadjuak Formation have been eroded in this area. [ABSTRACT FROM AUTHOR]

Greenland Halibut (Reinhardtius hippoglossoides) is a deepwater flatfish having a circumpolar distribution. Understanding the spatial connectivity and migratory patterns of this commercially valuable species is essential for ensuring a sustainable fishery; nonetheless, this information remains relatively scarce for many Greenland Halibut populations. Here we evaluate the connectivity and the population structure of halibut along coastal Greenland and Canada to better characterize the contribution of each production zone to the various stocks found in the northwestern Atlantic Ocean. In 2014 and 2016, we sampled 411 large Greenland Halibut from coastal Nunavut, Labrador, and Greenland. We used the elemental fingerprint (magnesium, strontium, and barium) from the otolith core and margin of the sampled fish to determine spatial differentiation of the source areas of the collected halibut. From the 17 sample sites, margin elemental fingerprint delineated four "elemental sectors", representing pooled adjacent sites having similar chemistry. Overall, 62% of Greenland Halibut were correctly assigned to their sampled coast. Elemental fingerprint of the otolith cores indicated three chemically distinct natal sources for the captured halibut. The chemical record in the otolith cores suggested a high connectivity of Greenland Halibut in the northwestern Atlantic and a main natal source located potentially along the west coast of Greenland. Given that our results suggest the presence of a large nursery around Disko Bay-Hellefiske Bank, protection measures should be considered for this area. [ABSTRACT FROM AUTHOR]

Fisheries-independent surveys are a critical tool for monitoring marine populations and communities. However, considerations must be made to account for variable-size-based catchability. The size-specific catchability function is therefore key for estimating size distributions, but often requires extensive data sets or specialized field experiments to determine. We develop a Bayesian model capable of simultaneously estimating both a size-based catchability curve and species-specific size spectrum parameters from trawl data by assuming that individual species size spectra follow a theoretically derived parametric size spectrum model. The resulting model provides a means of estimating catchability and size spectra within an adaptive framework capable of accommodating confounding factors such as vessel power and fish density, potentially allowing for improved biomass and productivity estimates. We demonstrate the application of this model using 15 years of Greenland Halibut (Reinhardtius hippoglossoides) survey data from Nunavut to determine size-specific catchabilities and assess whether the size spectrum of Greenland Halibut has changed across the time series. While size spectrum parameters for this stock were not found to vary, we did find evidence of time-varying catchability parameters across the study period. [ABSTRACT FROM AUTHOR]