The ice arches that usually develop at the northern and southern ends of Nares Strait play an important role in modulating the export of Arctic Ocean multi-year sea ice. The Arctic Ocean is evolving ...towards an ice pack that is younger, thinner, and more mobile and the fate of its multi-year ice is becoming of increasing interest. Here, we use sea ice motion retrievals from Sentinel-1 imagery to report on the recent behavior of these ice arches and the associated ice fluxes. We show that the duration of arch formation has decreased over the past 20 years, while the ice area and volume fluxes along Nares Strait have both increased. These results suggest that a transition is underway towards a state where the formation of these arches will become atypical with a concomitant increase in the export of multi-year ice accelerating the transition towards a younger and thinner Arctic ice pack.
Significant attention has focused on the potential for increased shipping activity driven by recently observed declines in Arctic sea ice cover. In this study, we describe the first coupled spatial ...analysis between shipping activity and sea ice using observations in the Canadian Arctic over the 1990–2015 period. Shipping activity is measured by using known ship locations enhanced with a least cost path algorithm to generate ship tracks and quantified by computing total distance traveled in kilometers. Statistically significant increases in shipping activity are observed in the Hudson Strait (150–500 km traveled yr−1), the Beaufort Sea (40–450 km traveled yr−1), Baffin Bay (50–350 km traveled yr−1), and regions in the southern route of the Northwest Passage (50–250 km traveled yr−1). Increases in shipping activity are significantly correlated with reductions in sea ice concentration (Kendall's tau up to −0.6) in regions of the Beaufort Sea, Western Parry Channel, Western Baffin Bay, and Foxe Basin. Changes in multiyear ice‐dominant regions in the Canadian Arctic were found to be more influential on changes to shipping activity compared to seasonal sea ice regions.
Key Points
First observational coupled spatial analysis of the influence of declining sea ice on increasing ship activity in the Canadian Arctic
Shipping activity increases are significantly correlated to declining sea ice in several regions
The presence of multiyear ice seems to influence shipping activity more than seasonal first‐year ice
Declining sea ice area in the Canadian Arctic has gained significant attention with respect to the prospect of increased shipping activities. To investigate relationships between recent declines in ...sea ice area with Arctic maritime activity, trend and correlation analysis was performed on sea ice area data for total, first-year ice (FYI), and multi-year ice (MYI), and on a comprehensive shipping dataset of observed vessel transits through the Vessel Traffic Reporting Arctic Canada Traffic Zone (NORDREG zone) from 1990 to 2012. Links to surface air temperature (SAT) and the satellite derived melt season length were also investigated. Between 1990 and 2012, statistically significant increases in vessel traffic were observed within the NORDREG zone on monthly and annual time-scales coincident with declines in sea ice area (FYI, MYI, and total ice) during the shipping season and on a monthly basis. Similarly, the NORDREG zone is experiencing increased shoulder season shipping activity, alongside an increasing melt season length and warming surface air temperatures (SAT). Despite these trends, only weak correlations between the variables were identified, although a step increase in shipping activity is apparent following the former summer sea ice extent minimum in 2007. Other non-environmental factors have also likely contributed to the observed increase in Arctic shipping activity within the Canadian Arctic, such as tourism demand, community re-supply needs, and resource exploration trends.
We present optical, X-ray and gamma-ray observations of GRB 111209A, at a redshift of z = 0.677. We show that this event was active in its prompt phase for about 25000 seconds, making it the longest ...burst ever observed. This rare event could have been detected up to z ~ 1.4. Compared to other long GRBs, GRB 111209A is a clear outlier in the energy-fluence and duration plane. The high-energy prompt emission shows no sign of a strong black body component, as expected if the event was caused by a tidal disruption event or a supernova shock breakout. Given the extreme longevity of this event, and a lack of a supernova signature, we propose that GRB 111209A is a relatively rare stellar collapse of a low metallicity blue super giant star. Only this progenitor can supply mass to the central engine over a duration of thousands of seconds. Hence, GRB 111209A could have more in common with population III stellar explosions, rather than normal long gamma ray bursts.
Exposure to persistent organic pollutants (POPs), including organochlorine (OC) pesticide POPs, has been associated with the increased prevalence of obesity and type 2 diabetes. However, the ...underlying mechanisms through which exposure to these compounds may promote obesity and metabolic dysfunction remain an area of active investigation. To this end, the concentration dependent effects of an environmentally relevant mixture of OC pesticide POPs on adipocyte function was explored utilizing a translationally relevant immortalized human subcutaneous preadipocyte/adipocyte model. Briefly, immortalized human preadipocytes/adipocytes were exposed to a mixture of dichlorodiphenyldichloroethylene (DDE), trans-nonachlor, and oxychlordane (DTO) then key indices of preadipocyte/adipocyte function were assessed. Exposure to DTO did not alter adipogenesis. However, in mature adipocytes, exposure to DTO slightly increased fatty acid uptake whereas isoproterenol stimulated lipolysis, basal and insulin stimulated glucose uptake, mitochondrial membrane potential, and cellular ATP levels were all significantly decreased. DTO significantly increased Staphylococcus aureus infection induced increases in expression of pro-inflammatory cytokines IL-6, IL-1β, and Mcp-1 as well as the adipokine resistin. Taken together, the present data demonstrated exposure to an environmentally relevant mixture of OC pesticide compounds can alter mature adipocyte function in a translationally relevant human adipocyte model which further supports the adipose tissue as an effector site of OC pesticide POPs action.
•Exposure to the organochlorine (OC) pesticide mixture did not alter adipogenesis.•Lipolysis and glucose uptake were decreased by exposure to the OC mixture.•OC exposure decreased both mitochondria membrane potential and cellular ATP levels.•OC exposure increased S. aureus induced proinflammatory cytokine expression.
The coastline of eastern Georgian Bay in the Parry Sound region is a distinctive nearshore environment consisting of a large deep-water embayment partially isolated from the open lake and connected ...with other embayments of diverse morphometric features. The underlying geology of the embayments and their watersheds contrasts with the larger lake basin, resulting in heterogenous water quality stemming from mixing of the high-alkalinity, low phosphorus waters of Georgian Bay with the low-alkalinity and higher phosphorus waters draining watersheds of the Canadian Shield. In 2016, water quality was examined in the deep basin of Parry Sound known as the Big Sound, and six connected embayments to examine the influences of watershed loading and anthropogenic development to enable better detection of changes related to human activity. Inter-basin mixing and river loading accounted for much of the variability in major ions, water clarity and nutrients except for Deep Bay, an embayment exhibiting signs of nutrient enrichment. The oligotrophic conditions in Parry Sound have changed little since 1990 unlike Lake Huron where the dreissenid invasion has correlated with falling phosphorus levels. Low calcium levels may limit dreissenid mussel numbers in Parry Sound and are hypothesized to have pre-empted mussel-related changes in water quality. Apparent productivity, light regime and water column stratification of the Big Sound and connected embayments contrast with the adjacent nearshore of Georgian Bay indicating an aquatic environment distinct from the exposed nearshore of Georgian Bay.
We investigate the prospects for joint low-latency gravitational wave (GW) detection and prompt electromagnetic (EM) follow-up observations of coalescing binary neutron stars (BNSs). For BNS mergers ...associated with short duration gamma-ray bursts (SGRBs), we for the first time evaluate the feasibility of rapid EM follow-ups to capture the prompt emission, early engine activity, or reveal any potential by-products such as magnetars or fast radio bursts. To achieve our goal, we first simulate a population of coalescing BNSs using realistic distributions of source parameters and estimate the detectability and localization efficiency at different times before merger. We then use a selection of facilities with GW follow-up agreements in place, from low-frequency radio to high-energy γ-ray to assess the prospects of prompt follow-up. We quantify our assessment using observational SGRB flux data extrapolated to be within the horizon distances of the advanced GW interferometric detectors LIGO and Virgo and to the prompt phase immediately following the binary merger. Our results illustrate that while challenging, breakthrough multimessenger science is possible with EM follow-up facilities with fast responses and wide fields-of-view. We demonstrate that the opportunity to catch the prompt stage (<5 s) of SGRBs can be enhanced by speeding up the detection pipelines of both GW observatories and EM follow-up facilities. We further show that the addition of an Australian instrument to the optimal detector network could possibly improve the angular resolution by a factor of 2 and thereby contribute significantly to GW–EM multimessenger astronomy.
We estimate the stochastic gravitational wave (GW) background signal from the field population of coalescing binary stellar mass black holes (BHs) throughout the universe. This study is motivated by ...recent observations of BH-Wolf-Rayet (WR) star systems and by new estimates in the metallicity abundances of star-forming galaxies that imply BH-BH systems are more common than previously assumed. Using recent analytical results of the inspiral-merger-ringdown waveforms for coalescing binary BH systems, we estimate the resulting stochastic GW background signal. Assuming average quantities for the single source energy emissions, we explore the parameter space of chirp mass and local rate density required for detection by advanced and third-generation interferometric GW detectors. For an average chirp mass of 8.7 M , we find that detection through 3 years of cross-correlation by two advanced detectors will require a rate density, r 0 >= 0.5 Mpc--3 Myr--1. Combining data from multiple pairs of detectors can reduce this limit by up to 40%. Investigating the full parameter space we find that detection could be achieved at rates r 0 ~ 0.1 Mpc--3 Myr--1 for populations of coalescing binary BH systems with average chirp masses of ~15 M which are predicted by recent studies of BH-WR star systems. While this scenario is at the high end of theoretical estimates, cross-correlation of data by two Einstein Telescopes could detect this signal under the condition r 0 >= 10--3Mpc--3 Myr--1. Such a signal could potentially mask a primordial GW background signal of dimensionless energy density, Delta *WGW ~ 10--10, around the (1-500) Hz frequency range.
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