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Microplastics are increasingly recognized as ubiquitous global contaminants, but questions linger regarding their source, transport and fate. We document the widespread distribution of microplastics in near-surface seawater from 71 stations across the European and North American Arctic - including the North Pole. We also characterize samples to a depth of 1,015 m in the Beaufort Sea. Particle abundance correlated with longitude, with almost three times more particles in the eastern Arctic compared to the west. Polyester comprised 73% of total synthetic fibres, with an east-to-west shift in infra-red signatures pointing to a potential weathering of fibres away from source. Here we suggest that relatively fresh polyester fibres are delivered to the eastern Arctic Ocean, via Atlantic Ocean inputs and/or atmospheric transport from the South. This raises further questions about the global reach of textile fibres in domestic wastewater, with our findings pointing to their widespread distribution in this remote region of the world., Microplastics have spread across the globe and reached even the most remote locations, but an understanding of their origins remains largely elusive. Here the authors quantify and characterise microplastics across the North Pole, finding that synthetic fibers like polyester are dominant and likely sourced from the Atlantic Ocean.

Arctic Cod (Boreogadus saida) occur throughout the circumpolar north; however, their distributions at localized scales are not well understood. The seasonal habitat associations and diet preferences across life-history stages of this keystone species are also poorly known, thereby impeding effective regulatory efforts in support of conservation objectives. The distribution of Arctic Cod in the Canadian Beaufort Sea was assessed using bottom trawling in shelf and slope habitats between 20 and 1000 m depths. Highest catch biomasses occurred at 350 and 500 m depth slope stations, coinciding with >0 °C temperatures in the Pacific–Atlantic thermohalocline and Atlantic water mass. Calanus glacialis, Calanus hyperboreus, Themisto libellula, and Themisto abyssorum were identified as key prey species in the diet of Arctic Cod, comprising approximately 86 % of total biomass in guts. Hierarchical cluster analysis with a SIMPROF test identified five statistically significant (p 200 m depth) coinciding with an associated increase in fish standard length with depth. Smaller Arctic Cod fed primarily on Calanus copepods and larger Arctic Cod fed primarily on the larger Themisto species. The habitat and diet associations presented here will inform knowledge of structural and functional relationships in Arctic marine ecosystems, aid in mitigation and conservation efforts, and will enhance our ability to predict the effects of climate change on the local spatial and depth associations of this pivotal marine fish.

Harmonic analyses of 16-year long time series of collocated TOPEX, Poseidon and Jason-1 altimeter data were carried out in the Pacific and western Atlantic Oceans and their marginal seas. These time series are sufficiently long to adequately separate the 18.6-year nodal satellites Q 1 n , O 1 n , K 1 n , M 2 n and K 2 n from their parent constituents Q 1 , O 1 , K 1 , M 2 and K 2 . Editing criteria were used to eliminate results in areas where these satellites are weak (i.e., smaller than their formal error estimates), or where they are strongly affected by aliased low-frequency signals (e.g. in the Kuroshio, in the Gulfstream and in their extension regions). As expected from tidal theory, the phases of the altimetry-derived nodal satellites agree reasonably well with the phases of their parents. However, due to their relatively small amplitudes and the remaining influence from low-frequency aliased signals, the altimeter observed amplitude ratios between the nodal satellites and their parent constituents tend to exceed the values predicted by the theory. Examination of diurnal and semidiurnal nodal amplitudes in select coastal areas and marginal seas around the Pacific and the western Atlantic Ocean allowed the assignment of a nodal character to regions, which were each classified as nodal diurnal, nodal semidiurnal, or nodal mixed, based on the nodal amplitudes in each band. While the areas with predominant diurnal tides are all nodal diurnal, the small nodal ratio of 0.037 for M 2 n resulted in some regions with strong M 2 tides being classified as nodal diurnal or nodal mixed. The amplitude ratio between K 2 n and K 2 is 0.30, making the K 2 n amplitudes sometimes comparable to those of M 2 n . However, this effect was not sufficient to make all the areas with dominant M 2 to be dominant nodal semidiurnal. The observed amplitudes of the 18.6-year nodal constituent M n are relatively small, 1.5–3.5 cm. These values significantly exceed its theoretical amplitudes, which are less than 1 cm almost everywhere. The analysed signals at M n frequency are therefore of mostly non-tidal origin, part of the broad-band decadal ocean variability.

Surface absorption and fluorescence measurements of Dissolved Organic Matter (DOM) were conducted along with hydrographic parameters in the Amerasian and Makarov Basins. Parallel factor analysis of DOM fluorescence identified four humic-like and one protein-like component in all 107 surface samples. Based on strong negative trends observed between the spectral slope in the 275–295 nm range and absorption at 370 nm, and four humic-like components C1–4, the DOM character was found to be basin-dependent. The Makarov Basin surface DOM was largely dominated by high molecular weight and humic-rich material whereas the Canada Basin surface DOM was more heterogeneous with a marked influence of in situ production. This study highlights that absorbing and fluorescing measurements can be used successfully to trace and differentiate DOM from diverse sources and across frontal zones, and as such can be convenient and complementary tools for the better understanding of marine biogeochemical cycling of carbon.

The effects of reduced sampling schedules (duty cycles) on velocity statistics derived from satellite-tracked drifters in the northeast Pacific Ocean are investigated. Continuous segments of the drifter records (in which all available satellite positions fixes are recorded and processed by Service ARGOS) are degraded to match the standard duty cycle used in the World Ocean Circulation Experiment–Surface Velocity Program, in which there are 48 h of no data transmission followed by 24 h of received transmission (48–24 h). Also examined are duty cycles of 32–16 h and 16–8 h. It is found that the strong inertial motions prevalent in the drifter records result in significantly biased statistics derived from the degraded series. Reproduction of the original prime (mean and standard deviation) and rotary spectral statistics requires an interpolation that takes into account the oscillatory component of the drifter motions. Duty cycles having shorter but more frequent gaps (e.g., 16–8 h) are not sufficien...

[1] The freshwater composition of waters on the southeast Greenland shelf and slope are described using a set of high-resolution transects occupied in summer 2004, which included hydrographic, velocity, nutrient, and chemical tracer measurements. The nutrient and tracer data are used to quantify the fractions of Pacific Water, sea ice melt, and meteoric water present in the upper layers of the East Greenland Current (EGC) and East Greenland Coastal Current (EGCC). The EGC/EGCC system dominates the circulation of this region and strongly influences the observed distribution of the three freshwater types. Sea ice melt and meteoric water fractions are surface intensified, reflecting their sources, and generally increase southward from Denmark Strait to Cape Farewell, as well as shoreward. Significant fractions of Pacific Water are found in the subsurface layers of the EGCC, supporting the idea that this inner shelf branch is directly linked to the EGC and thus to the Arctic Ocean. A set of historical sections is examined to investigate the variability of Pacific Water content in the EGC and EGCC from 1984 to 2004 in the vicinity of Denmark Strait. The fraction of Pacific Water increased substantially in the late 1990s and subsequently declined to low levels in 2002 and 2004, mirroring the reduction in Pacific Water content reported previously at Fram Strait. This variability is found to correlate significantly with the Arctic Oscillation index, lagged by 9 years, suggesting that the Arctic Ocean circulation patterns bring varying amounts of Pacific Water to the North Atlantic via the EGC/EGCC.

Possible multiple equilibria of large-scale flows over topography have been subjects of many recent investigations. Early suggestions of Charney and De Vore, Hart and Wiin-Nicisen were based upon idealized flows of very few degrees of freedom. Subsequent studies based upon more elaborate systems failed to show intransitive multiple equilibria. On the contrary, we exhibit well-resolved, fully eddy-active model results which show multiple equilibria to be well-established over a range of parameters. “Blocked” regimes are characterized by transient eddy activity. Under steady external forcing, the flow regimes appear to be intransitive.