Folder Transport of Marine Litter

Documents

pdf Cózar, A., et al. (2017). "The Arctic Ocean as a dead end for floating plastics in the North Atlantic branch of the Thermohaline Circulation." Science advances 3(4): e1600582.

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Cózar-2017-The Arctic Ocean as a dead end for.pdf

Cózar, A., et al. (2017). "The Arctic Ocean as a dead end for floating plastics in the North Atlantic branch of the Thermohaline Circulation." Science advances 3(4): e1600582.
The subtropical ocean gyres are recognized as great marine accummulation zones of floating plastic debris; however, the possibility of plastic accumulation at polar latitudes has been overlooked because of the lack of nearby pollution sources. In the present study, the Arctic Ocean was extensively sampled for floating plastic debris from the Tara Oceans circumpolar expedition. Although plastic debris was scarce or absent in most of the Arctic waters, it reached high concentrations (hundreds of thousands of pieces per square kilometer) in the northernmost and easternmost areas of the Greenland and Barents seas. The fragmentation and typology of the plastic suggested an abundant presence of aged debris that originated from distant sources. This hypothesis was corroborated by the relatively high ratios of marine surface plastic to local pollution sources. Surface circulation models and field data showed that the poleward branch of the Thermohaline Circulation transfers floating debris from the North Atlantic to the Greenland and Barents seas, which would be a dead end for this plastic conveyor belt. Given the limited surface transport of the plastic that accumulated here and the mechanisms acting for the downward transport, the seafloor beneath this Arctic sector is hypothesized as an important sink of plastic debris.

pdf Obbard, R. W., et al. (2014). "Global warming releases microplastic legacy frozen in Arctic Sea ice." Earth's Future 2(6): 315-320.

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Obbard-2014-Global warming releases microplast.pdf

Obbard, R. W., et al. (2014). "Global warming releases microplastic legacy frozen in Arctic Sea ice." Earth's Future 2(6): 315-320.

When sea ice forms it scavenges and concentrates particulates from the water column, which then become trapped until the ice melts. In recent years, melting has led to record lows in Arctic Sea ice extent, the most recent in September 2012. Global climate models, such as that of Gregory et al. (2002), suggest that the decline in Arctic Sea ice volume (3.4% per decade) will actually exceed the decline in sea ice extent, something that Laxon et al. (2013) have shown supported by satellite data. The extent to which melting ice could release anthropogenic particulates back to the open ocean has not yet been examined. Here we show that Arctic Sea ice from remote locations contains concentrations of microplastics are several orders of magnitude greater than those that have been previously reported in highly contaminated surface waters, such as those of the Pacific Gyre. Our findings indicate that microplastics have accumulated far from population centers and that polar sea ice represents a major historic global sink of man-made particulates. The potential for substantial quantities of legacy microplastic contamination to be released to the ocean as the ice melts therefore needs to be evaluated, as do the physical and toxicological effects of plastics on marine life.

pdf Tubau, X., et al. (2015). "Marine litter on the floor of deep submarine canyons of the Northwestern Mediterranean Sea: the role of hydrodynamic processes." Progress in Oceanography 134: 379-403.

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Tubau-2015-Marine litter on the floor of deep.pdf

Tubau, X., et al. (2015). "Marine litter on the floor of deep submarine canyons of the Northwestern Mediterranean Sea: the role of hydrodynamic processes." Progress in Oceanography 134: 379-403.
Marine litter represents a widespread type of pollution in the World’s Oceans. This study is based on direct observation of the seafloor by means of Remotely Operated Vehicle (ROV) dives and reports litter abundance, type and distribution in three large submarine canyons of the NW Mediterranean Sea, namely Cap de Creus, La Fonera and Blanes canyons. Our ultimate objective is establishing the links between active hydrodynamic processes and litter distribution, thus going beyond previous, essentially descriptive studies.
Litter was monitored using the Liropus 2000 ROV. Litter items were identified in 24 of the 26 dives carried out in the study area, at depths ranging from 140 to 1731 m. Relative abundance of litter objects by type, size and apparent weight, and distribution of litter in relation to depth and canyon environments (i.e. floor and flanks) were analysed. Plastics are the dominant litter component (72%), followed by lost fishing gear, disregarding their composition (17%), and metal objects (8%). Most of the observed litter seems to be land-sourced. It reaches the ocean through wind transport, river discharge and after direct dumping along the coastline. While coastal towns and industrial areas represent a permanent source of litter, tourism and associated activities relevantly increase litter production during summer months ready to be transported to the deep sea by extreme events. After being lost, fishing gear such as nets and long-lines has the potential of being harmful for marine life (e.g. by ghost fishing), at least for some time, but also provides shelter and a substrate on which some species like cold-water corals are capable to settle and grow.
La Fonera and Cap de Creus canyons show the highest mean concentrations of litter ever seen on the deep-sea floor, with 15,057 and 8090 items km−2, respectively, and for a single dive litter observed reached 167,540 items km−2. While most of the largest concentrations were found on the canyon floors at water depths exceeding 1000 m, relatively little litter was identified on the canyon walls. The finding of litter ‘hotspots’ (i.e., large accumulations of litter) formed by mixtures of land- and marine-sourced litter items and natural debris such as sea urchin carcasses evidences an efficient transport to the floor of mid and lower canyon reaches at least.
High-energy, down canyon near-bottom flows are known to occur in the investigated canyons. These are associated to seasonal dense shelf water cascading and severe coastal storms, which are the most energetic hydrodynamic processes in the study area thus becoming the best candidates as main carriers of debris to the deep. The fact that the investigated canyons have their heads at short distance (<4 km) from the shoreline enhances their ability to trap littoral drift currents and also to convey the signal of the above-mentioned high-energy events to the deep, including their litter load. This study contributes to assess the origin and transport mechanisms of litter to the deep sea as well as its potential impact on deep-sea ecosystems.

pdf van Sebille, E., et al. (2012). "Origin, dynamics and evolution of ocean garbage patches from observed surface drifters." Environmental Research Letters 7(4): 044040.

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van Sebille-2012-Origin, dynamics and evolutio.pdf

van Sebille, E., et al. (2012). "Origin, dynamics and evolution of ocean garbage patches from observed surface drifters." Environmental Research Letters 7(4): 044040.
Much of the debris in the near-surface ocean collects in so-called garbage patches where, due to convergence of the surface flow, the debris is trapped for decades to millennia. Until now, studies modelling the pathways of surface marine debris have not included release from coasts or factored in the possibilities that release concentrations vary with region or that pathways may include seasonal cycles. Here, we use observational data from the Global Drifter Program in a particle-trajectory tracer approach that includes the seasonal cycle to study the fate of marine debris in the open ocean from coastal regions around the world on interannual to centennial timescales. We find that six major garbage patches emerge, one in each of the five subtropical basins and one previously unreported patch in the Barents Sea. The evolution of each of the six patches is markedly different. With the exception of the North Pacific, all patches are much more dispersive than expected from linear ocean circulation theory, suggesting that on centennial timescales the different basins are much better connected than previously thought and that inter-ocean exchanges play a large role in the spreading of marine debris. This study suggests that, over multi-millennial timescales, a significant amount of the debris released outside of the North Atlantic will eventually end up in the North Pacific patch, the main attractor of global marine debris.