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The rainfall over the Yangtze River Valley (YRV) in June 2020 broke the record since 1979. Here we show that all three oceans of the Pacific, Indian and Atlantic Oceans contribute to the YRV rainfall in June 2020, but the Atlantic plays a dominant role. The sea surface temperature (SST) anomalies in three oceans are associated with the two vorticity anomalies: negative 200-hPa relative vorticity anomalies over North China (NC) and negative 850-hPa relative vorticity anomalies in the South China Sea (SCS). The rainfall anomalies in the YRV are mainly controlled by atmospheric process associated with the NC vorticity. The positive SST anomalies in May over the western North Atlantic induce positive geopotential height anomalies in June over the mid-latitude North Atlantic, which affect the rainfall anomalies in the YRV by changing the NC vorticity via Atlantic-induced atmospheric wave train across Europe. The Indian Ocean and tropical North Atlantic, as capacitors of Pacific El Niño events in the preceding winter, affect the SCS vorticity associated with the anomalous anticyclone over the SCS and also facilitate the YRV rainfall by providing favorable moisture conditions. This study suggests that the May SST over the western North Atlantic is a good predictor of June rainfall anomalies in the YRV and highlights the important impacts of three-ocean SSTs on extreme weather and climate events in China. [ABSTRACT FROM AUTHOR]

Understanding how mobile, marine predators use three-dimensional space over time is central to inform management and conservation actions. Combining tracking technologies can yield powerful datasets over multiple spatio-temporal scales to provide critical information for these purposes. For the white shark (Carcharodon carcharias), detailed movement and migration information over ontogeny, including inter- and intra-annual variation in timing of movement phases, is largely unknown in the western North Atlantic (WNA), a relatively understudied area for this species. To address this need, we tracked 48 large juvenile to adult white sharks between 2012 and 2020, using a combination of satellite-linked and acoustic telemetry. Overall, WNA white sharks showed repeatable and predictable patterns in horizontal movements, although there was variation in these movements related to sex and size. While most sharks undertook an annual migratory cycle with the majority of time spent over the continental shelf, some individuals, particularly adult females, made extensive forays into the open ocean as far east as beyond the Mid-Atlantic Ridge. Moreover, increased off-shelf use occurred with body size even though migration and residency phases were conserved. Summer residency areas included coastal Massachusetts and portions of Atlantic Canada, with individuals showing fidelity to specific regions over multiple years. An autumn/winter migration occurred with sharks moving rapidly south to overwintering residency areas in the southeastern United States Atlantic and Gulf of Mexico, where they remained until the following spring/summer. While broad residency and migration periods were consistent, migratory timing varied among years and among individuals within years. White sharks monitored with pop-up satellite-linked archival tags made extensive use of the water column (0–872 m) and experienced a broad range of temperatures (−0.9 – 30.5°C), with evidence for differential vertical use based on migration and residency phases. Overall, results show dynamic inter- and intra-annual three-dimensional patterns of movements conserved within discrete phases. These results demonstrate the value of using multiple tag types to track long-term movements of large mobile species. Our findings expand knowledge of the movements and migration of the WNA white shark population and comprise critically important information to inform sound management strategies for the species.

The Western North Atlantic Ocean (WNAO) is a complex land‐ocean‐atmosphere system that experiences a broad range of atmospheric phenomena, which in turn drive unique aerosol transport pathways, cloud morphologies, and boundary layer variability. This work, Part 2 of a 2‐part paper series, provides an overview of the atmospheric circulation, boundary layer variability, three‐dimensional cloud structure, and precipitation over the WNAO; the companion paper (Part 1) focused on chemical characterization of aerosols, gases, and wet deposition. Seasonal changes in atmospheric circulation and sea surface temperature explain a clear transition in cloud morphologies from small shallow cumulus clouds, convective clouds, and tropical storms in summer, to stratus/stratocumulus and multilayer cloud systems associated with winter storms. Synoptic variability in cloud fields is estimated using satellite‐based weather states, and the role of postfrontal conditions (cold‐air outbreaks) in the development of stratiform clouds is further analyzed. Precipitation is persistent over the ocean, with a regional peak over the Gulf Stream path, where offshore sea surface temperature gradients are large and surface fluxes reach a regional peak. Satellite data show a clear annual cycle in cloud droplet number concentration with maxima (minima) along the coast in winter (summer), suggesting a marked annual cycle in aerosol‐cloud interactions. Compared with satellite cloud retrievals, four climate models qualitatively reproduce the annual cycle in cloud cover and liquid water path, but with large discrepancies across models, especially in the extratropics. The paper concludes with a summary of outstanding issues and recommendations for future work. Key Points: Atmospheric circulation and sea surface temperature drive large seasonal changes in precipitation, surface fluxes, and cloud typesSynoptic activity in winter yields the highest seasonal rain rates, low‐cloud occurrence, and cloud droplet number concentrationsClimate models simulate a wide range of low‐cloud properties, with improved results for models with more sophisticated turbulence schemes [ABSTRACT FROM AUTHOR]

We report on two sightings of individual blue whales (Balaenoptera musculus) off the coast of Virginia during marine mammal surveys. On 11 April 2018, during a vessel survey off the coast of Virginia, a single blue whale was observed approximately 100 km east-northeast of Virginia Beach. On 10 February 2019, another single blue whale was recorded during an aerial survey approximately 135 km east-southeast of Virginia Beach. These observations mark the first time this endangered species has been documented with photographs off the coast of Virginia, and represent the southernmost confirmed sightings in waters of the United States Atlantic Exclusive Economic Zone (EEZ). At the time of the vessel observation, numerous fin whales (Balaenoptera physalus), humpback whales (Megaptera novaeangliae), and North Atlantic right whales (Eubalaena glacialis), were observed within the same approximately 8 km2 area as the blue whale. For the aerial sighting, the blue whale was seen feeding among at least 15 fin whales in an area approximately 4 km2. These sightings contribute to the small body of information existing for the late winter/early spring distribution of blue whales in waters of the western North Atlantic. [ABSTRACT FROM AUTHOR]

Observations of WCR centers and radii for a 24-year (1981–2004) period displayed strong inter-annual variability (IAV) of encounters between WCRs and the outer continental shelf between 75° and 65° W, and decreasing encounter area east of 65° W. Temporal mean WCR/shelf encounters showed two significant maxima, i.e. "hotspots", along the outer shelf between 72° and 71° W (south of Long Island) and 69° and 68° W (south of Nantucket Shoals). Higher temporal mean WCR/shelf encounter areas were observed during July–December (warm) months of up to twice those for the January–June (cold) months west of 65° W in agreement with earlier work. The correlation between time series of WCR/shelf encounter area and annual number of discrete WCRs from 75° and 65° W is small and insignificant. Longfin squid (Doryteuthis pealeii) displays large IAV in relative abundance between 75° and 65° W within the US Northeast Shelf Large Marine Ecosystem. Correlations of the spatially averaged annual mean WCR/shelf encounter area with D. pealeii autumn relative abundance between 75° and 65° W from 1981 and 2004 were small and insignificant. The weak correlation showed that no relationship exists between D. pealeii relative abundance and our WCR/shelf encounter metric over the broad-scale shelf region from Cape Hatteras to Georges Bank, suggesting finer scale studies are warranted. [ABSTRACT FROM AUTHOR]

Marine environments are subject to a range of human disturbances. Identifying effective conservation strategies, in order to manage or mitigate the negative impacts of human activities, requires a way to first identify and evaluate the impact of activities on ecosystem components. Multicriteria decision analysis (MCDA) techniques such as the Analytic Hierarchy Process (AHP) offer a way to systematically evaluate and integrate stakeholder opinion in order to set priorities and make decisions. With a goal to synthesize current knowledge of the potential impacts of human activity on breeding and non-breeding seabirds in the western North Atlantic Ocean, we present a case study involving the use of AHP to assess sensitivity of species to such hazards as: fisheries bycatch, oiling, light pollution, vessel traffic, marine debris, and offshore wind turbines. Based on responses from ten North Atlantic seabird experts, fisheries bycatch (particularly when involving suspended gill nets) was identified as the greatest risk across a wide range of species, with an overall relative value of 0.47 ± SE 0.026. Oiling risk was the second most highly ranked (0.26 ± 0.026, of which 0.214 corresponded with surface oil, 0.044 with oil and gas platform interactions), and was considered to have the greatest potential impact on alcids (Common and Thick-billed Murre, Atlantic Puffin, Razorbill, Dovekie). Offshore wind turbines (0.097 ± 0.022), marine debris (0.08 ± 0.016), light pollution (0.058 ± 0.0077), and traffic (0.042 ± 0.0053) were considered to be less serious risks for seabirds than fisheries bycatch and oiling. In addition to demonstrating how relative risk can be quantified using a multicriteria decision analysis technique such as AHP, we summarize the sensitivities of fourteen seabirds and suggest ways in which multicriteria decision analysis can enhance conservation planning. • Expert opinion can synthesize information across temporal, spatial, or ecological scales, and reduce uncertainty when data is insufficient. • Analytic Hierarchy Process (AHP) was used to evaluate and integrate expert opinion on the risks posed to 14 species of seabird in NW Atlantic. • Overall risks posed by human activity, as well as species-specific sensitivities, were quantified using the AHP framework. • Fisheries bycatch and oiling were considered the greatest risk for a wide range of species. • AHP is an effective tool to rank and prioritize conservation concerns, and can help to guide conservation planning and management decisions. [ABSTRACT FROM AUTHOR]

"The Gully", situated off Nova Scotia, Canada, is the largest submarine canyon in the western North Atlantic. This unique oceanographic feature, which became a Marine Protected Area (MPA) in 2004, is rich in marine biodiversity and is part of the critical habitat of Endangered northern bottlenose whales (Hyperoodon ampullatus). To understand the potential impact of plastic pollution in the MPA and on this Endangered cetacean, we evaluated trends over time in the abundance and composition of plastics and compared these to the stomach contents of recently stranded northern bottlenose whales. From the 1990s–2010s, the median abundance of micro-sized (<5 mm) and small plastics (5 mm–2.5 cm) increased significantly, while the median abundance of large plastics (>2.5 cm) decreased significantly. Plastic abundance from the 2010s for micro-sized and small plastics varied from 5586–438 196 particles km−2, higher than previously measured estimates for surrounding offshore areas. Polymers identified using FTIR spectroscopy included polyethylene, polypropylene, polyethylene terephthalate polyester, nylon, alkyds (paint), and natural and semi-synthetic cellulosic fibers. The abundance of large debris ranged from 0 to 108.6 items km−2 and consisted of plastic sheets and bags, food wrappers and containers, rope, fishing buoys, and small plastic fragments. Whale stomach contents contained fragments of fishing nets, ropes, bottle caps, cups, food wrappers, smaller plastic fragments, fibers, and paint flakes, consistent with the composition and character of items collected from their critical habitat. Despite being far from centres of human population, the unique oceanographic features of The Gully (i.e. currents and bathymetric complexity) may concentrate plastic debris, increasing exposure rates of whales to plastic pollution. The increase in micro-sized and small plastics over time suggests associated health and welfare impacts of ingested plastics should be accounted for in future recovery plans for this Endangered species. • Plastics from multiple sources pollute an offshore marine protected area. • The amount of large plastics decreased while small plastics increased over time. • Oceanographic features may trap plastics increasing encounter rates for whales. • Whales are ingesting plastics consistent with the types found in surface waters. • Plastic ingestion should be considered in recovery plans for Endangered whales. [ABSTRACT FROM AUTHOR]

To investigate the oceanic lithosphere formation and early seafloor spreading history of the North Atlantic Ocean, we examine multiscale magnetic anomaly data from the Jurassic/Early Cretaceous age Eastern North American Margin (ENAM) between 31 and 40°N. We integrate newly acquired sea surface magnetic anomaly and seismic reflection data with publicly available aeromagnetic and composite magnetic anomaly grids, satellite-derived gravity anomaly, and satellite-derived and shipboard bathymetry data. We evaluate these data sets to (1) refine magnetic anomaly correlations throughout the ENAM and assign updated ages and chron numbers to M0-M25 and eight pre-M25 anomalies; (2) identify five correlatable magnetic anomalies between the East Coast Magnetic Anomaly (ECMA) and Blake Spur Magnetic Anomaly (BSMA), which may document the earliest Atlantic seafloor spreading or synrift magmatism; (3) suggest preexisting margin structure and rifting segmentation may have influenced the seafloor spreading regimes in the Atlantic Jurassic Quiet Zone (JQZ); (4) suggest that, if the BSMA source is oceanic crust, the BSMA may be M series magnetic anomaly M42 (~168.5 Ma); (5) examine the along and across margin variation in seafloor spreading rates and spreading center orientations from the BSMA to M25, suggesting asymmetric crustal accretion accommodated the straightening of the ridge from the bend in the ECMA to the more linear M25; and (6) observe anomalously high-amplitude magnetic anomalies near the Hudson Fan, which may be related to a short-lived propagating rift segment that could have helped accommodate the crustal alignment during the early Atlantic opening. [ABSTRACT FROM AUTHOR]

Marine aerosols were collected over the western North Atlantic off the coast of Boston to Bermuda in August 2012 using a high-volume air sampler. Aerosol samples were analyzed for organic and elemental carbon (OC/EC), low molecular weight dicarboxylic acids and related compounds, lipid class compounds (n-alkanes, fatty acids and fatty alcohols), sugars and various secondary organic aerosol (SOA) tracers. Homologous series (C 2 -C 12 ) of dicarboxylic acids (31–335 ng/m 3 ) were detected with a predominance of oxalic acid. Diacids were found to be the most abundant compound class followed by monoterpene-SOA tracers > isoprene-SOA tracers > sugars > oxoacids > fatty alcohols > fatty acids > α-dicarbonyls > aromatic acids > n-alkanes. The concentrations of these compounds were higher in the coastal site and decreased towards the open ocean. However, the abundance of diacids stayed relatively high even in the remote ocean. Interestingly, contributions of oxalic acid to total aerosol carbon increased from the coast (2.3%) to the open ocean (5.6%) near Bermuda. Stable carbon isotope ratios of aerosol total carbon and individual diacids and oxoacids were determined using an isotope ratio mass spectrometer. The stable carbon isotopic composition of oxalic acid increased from the coast (−17.5‰) to the open ocean (−12.4‰), confirming that photochemical aging of organic aerosols occurred during the atmospheric over the ocean. Stable carbon isotope ratios of bulk aerosol carbon also increased from the coast near Boston (−24.3‰) to the open ocean near Bermuda (−18.2‰), consistent with photochemical aging of organic aerosols. [ABSTRACT FROM AUTHOR]

The prevailing view of western Atlantic hydrography during the Last Glacial Maximum (LGM) calls for transport and intermixing of deep southern and intermediate northern end members. However, δ13C and Δ14C results on foraminifera from a sediment core at 5.0 km in the northern subtropics show that there may have also been a northern source of relatively young, very dense, nutrient-depleted water during the LGM (18 ky to 21 ky ago). These results, when integrated with data from other western North Atlantic locations, indicate that the ocean was poorly ventilated at 4.2 km, with better ventilation above and below that depth. If this is a signal of water mass source and not nutrient storage, it would indicate that a previously unrecognized deep water end member originated along the western margin of the Labrador Sea, analogous to dense water formation today around Antarctica and in the Okhotsk Sea. [ABSTRACT FROM AUTHOR]

Fisheries that operate at large spatial scales and with high intensity have the potential to impact highly migratory species, and it is important to characterize threats to specific breeding populations of these species. We used many‐to‐many mixed‐stock analysis (MSA) (n = 408) and microsatellite assignment testing (n = 397) to determine source populations for leatherback turtles (Dermochelys coriacea) caught as bycatch in the U.S. pelagic longline fishery from 2002 to 2012 in the western North Atlantic. Within the United States, we had bycatch samples from the majority of statistical fishing areas: Gulf of Mexico (GOM), Northeast Distant (NED), Caribbean (CAR), Florida East Coast (FEC), Mid Atlantic Bight (MAB), Northeast Coastal (NEC), South Atlantic Bight (SAB) and Sargasso (SAR). We determined the proportions of turtles from each of nine nesting stocks in the Atlantic in each of the sampled areas. These nesting stocks included Brazil, Costa Rica, Florida, Trinidad, French Guiana, St. Croix, Ghana, Gabon, and South Africa. The MSA revealed that the NED had a lower relative proportion of turtles from Costa Rica than other areas and that the GOM had the highest relative proportion of turtles from Costa Rica. No turtles were assigned to the African rookeries, lending further evidence that turtles from that region forage elsewhere and therefore may not be affected by western North Atlantic fisheries. This work contributes to the ongoing assessment of threats to leatherback turtles in the Regional Management Unit (RMU) of the western North Atlantic, and draws attention to the disproportionate number of turtles from Costa Rica being caught in the Gulf of Mexico; Costa Rica is one of the only populations in the northern Atlantic that is not experiencing significant increases in nest numbers. This approach should be useful in determining population‐specific threats to other highly migratory protected species that may depend on segregated foraging areas either within or among species. [ABSTRACT FROM AUTHOR]

We describe a possible cryptic invasion of the toxic Western Pacific hydromedusa Gonionemus vertens (Cnidaria, Hydrozoa, Limnomedusae) in the Northwest Atlantic Ocean. G. vertens was first noticed in Eel Pond in Woods Hole (Cape Cod), Massachusetts in 1894, but nearly disappeared in the 1930s, coincident with a large scale die-off of its preferred eelgrass habitat. During the 1894-1930 period, G. vertens was the object of numerous studies by local scientists, and was not reported as stinging. In contrast, Western Pacific G. vertens are known for their toxic sting symptoms, which include severe pain, respiratory distress, and paralysis. Here, we report new sightings in the northwest Atlantic from the late twentieth century onwards. Sightings are most frequent in Waquoit Bay on the southern-facing shore of Cape Cod, Massachusetts, and on the island of Martha's Vineyard, Massachusetts, but medusae have also been found in locations ranging from Long Island (New York) to Wellfleet Harbor on the north side of Cape Cod. We also describe reports of stings with symptoms similar to those produced by the toxic Western Pacific strain. The first sting report that we are aware of occurred in 1990 in Waquoit Bay, and stings have since occurred in most of G. vertens' known Northwest Atlantic locations. It appears likely that the recent sightings associated with toxic stings represent a new, cryptic invasion of the Western Pacific form. These new observations are cause for public health concern, particularly as warmer temperatures associated with climate change may promote G. vertens blooms and thus the likelihood of dangerous human-jellyfish interactions in a populated, tourism-dependent region. [ABSTRACT FROM AUTHOR]

Humpback whales (Megaptera novaeangliae) are known to utilize Massachusetts Bay as a feeding ground in the spring and summer, during the annual migration of the Gulf of Maine sub-population. However, there is a limited understanding of the pattern of humpback whale occurrence in this region outside of the feeding period. Passive acoustic monitoring of Massachusetts Bay over a two-year period, revealed an extended presence of acoustically active humpback whales throughout a majority of the study period (87%; 633 days of presence out of 725 days of acoustic monitoring). Humpback whale presence oscillated between lengthy periods of consistent presence (April to December) and relatively shorter periods of variable presence (December to March). Seasonal variation in presence was evident during three distinct phases: (1) maximum-presence from spring to early winter; (2) variable-presence in early winter and early spring; and (3) minimum-presence mid-winter. The variation in seasonal presence was concurrent with coarse migratory patterns of humpback whales, and yearly variations in presence presumably reflect a shift in the influx and efflux of whales between years. The extended presence of humpbacks in this area suggests that Massachusetts Bay is an important, year-round habitat for the Gulf of Maine sub-population, and may warrant revision of management and regulatory practices to reflect this presence. [ABSTRACT FROM PUBLISHER]

Abstract: A series of topographic/bathymetric anomalies trend along the western passive plate margin of the North Atlantic and are characterized roughly by uplift offshore on the ocean plate and subsidence at the continental margin. The features—determined from two independent data sets—are not constant along the strike of the plate boundary, however. The anomalous topography/bathymetry is considered to be a surface dynamic response to edge driven convection in the mantle occurring at the continental margin. Three-dimensional numerical mantle flow experiments are conducted to investigate the margin-parallel and -perpendicular development of edge driven convection and dynamic topography. The flow induces a near-margin topography low and offshore bathymetry high of up to ∼1.5km. If the thermal structure of the convection is perturbed along strike to the plate boundary, the edge driven convection cells develop instabilities with a similar ∼500km wavelength. This causes localized peaks and saddles in the topography/bathymetry that is consistent with the observed variability of residual topography along the western side of the North Atlantic. The plate margin experiences modest thermal erosion causing dynamic topography to migrate continent-ward and slightly increasing its wavelength. Generally, though, the flow and associated topography developed into a quasi-static form relative to the passive margin over timescales of at least tens of millions of years. [Copyright &y& Elsevier]

One of the key steps towards predicting dimethylsulfide (DMS) emission to the atmosphere is to understand the distribution and cycling of biogenic sulfur in the microlayer. In this study, we examined the distribution of DMS and dissolved and particulate fractions of dimethylsulfoniopropionate (DMSPd and DMSPp) in the surface microlayer and bulk water of the western North Atlantic during July 2003. DMS concentrations in the bulk water varied from 0.71 to 7.65 nM. In contrast, DMS concentrations in the surface microlayer were fairly low (0.17–1.33 nM). Average concentrations of DMSPd and DMSPp in the bulk water were 2.09 (1.87–6.25) and 44.1 (8.06–119.8) nM, respectively, and those in the surface microlayer were 15.4 (4.06–54.3) and 29.9 (7.32–97.0) nM. In general, DMS was depleted in the microlayer (mean concentration: 0.60 nM) relative to the bulk water (mean concentration: 2.38 nM) with enrichment factors (the ratio of the microlayer concentration to bulk water concentration) ranging from 0.13 to 0.54. There was no consistent enrichment of DMSPp and chlorophyll a in the microlayer. On the contrary, DMSPd appeared to be highly enriched in the microlayer with an average EF of 4.89. The concentration of phaeopigments was also generally greater in the microlayer than in the bulk water, presumably due to enhanced photo-oxidation of chlorophyll a under high surface light intensities in the microlayer. In the study area, the concentration of DMSPp was significantly correlated with the abundance of dinoflagellates in the microlayer. Moreover, a significant correlation between the distributions of DMS, DMSPp, chlorophyll a and phaeopigment concentrations in the microlayer and the bulk water demonstrated that the biogenic materials in the microlayer come primarily from the bulk water below. [ABSTRACT FROM AUTHOR]

Abstract: Previous work concerning Gulf Stream warm-core rings (WCRs) and their associated shelf water entrainments have been based upon single surveys or time series from individual WCRs. To date, estimates of annual shelf water volume entrained into the Slope Sea by WCRs and its interannual variability have not been made. Using a long time series of satellite-derived sea surface temperature (SST) observations of Slope Sea WCRs, we have completed an analysis of 22 years of WCR data (1978–1999) between 75°W and 50°W to understand the interannual variability of WCRs and their role in entraining shelf water. Satellite-derived SST data digitized at Bedford Institute of Oceanography are analyzed using an ellipse-fitting feature model to determine key WCR characteristics including WCR center position, radius and orientation. Key characteristics are then used to compute WCR swirl velocity by finite-differencing WCR orientations (θ) obtained from the feature model time series. Global mean WCR-edge swirl velocity calculated from all observations is 105.72±10.7km day−1 (122.36±12.4cms−1), and global mean WCR radius is 64.8±6.2km. Primary and derived WCR data are incorporated into a two-dimensional ring entrainment model (RM) using the quasi-geostrophic approximation of the potential vorticity equation. The RM defines ambient water as entrained by a WCR only if the gradient of relative vorticity term (horizontal shear) dominates the potential vorticity. Proximity of a WCR to the position of the shelf-slope front (SSF) is then used to determine whether the ambient water is entrained from the outer continental shelf. WCR-induced shelf entrainment derived from the RM displays considerable spatial variability, with maximum entrainment occurring offshore of Georges Bank, advecting a mean total annual shelf water volume of 7500km3 year−1 from the region. Estimates of shelf water fluxes display significant interannual variability, which may be in part due to the observed covariance between WCR occurrences and the state of the North Atlantic Oscillation (NAO). Increased (decreased) occurrences of WCRs are evidenced during positive (negative) phases of the NAO. The total mean annual shelf-wide WCR-induced shelf water transport is estimated to be 23,700km3 year−1 (0.75Sv), accounting for nearly 25% of the total transport in the Slope Sea region neighboring the outer continental shelf. [Copyright &y& Elsevier]

Abstract: We report results from the first deployment of a buoy-mounted aerosol sampler on the Bermuda Testbed Mooring (BTM) in the Sargasso Sea, in which a time-series of 21 aerosol samples were collected over the period May 5–September 29, 2004. These aerosol samples were analyzed for iron and soluble sodium (as a proxy for sea salt). Also analyzed was a time-series of 22 aerosol samples collected over the same period at the Tudor Hill atmospheric sampling tower on Bermuda. The buoy sampler worked as intended and successfully collected a time-series of aerosol samples, thus demonstrating that moored buoys can be used as oceanic observatories to provide information on the temporal (weekly, monthly and seasonal) variability in the concentration of aerosol iron (and other trace elements) over the surface ocean. The magnitude and time variation of aerosol Fe concentrations calculated from the BTM buoy samples are in close agreement with the corresponding aerosol Fe record from the Tudor Hill tower, which is located approximately 80km northwest of the mooring site. Both the BTM and Tudor Hill samples record periods of high aerosol iron loadings in late June and late July 2004, reflecting the transport of soil dust from North Africa, with the highest concentration of aerosol iron at the BTM site (0.83μgm−3) measured in late June. Concentrations of sea-salt aerosol calculated from the BTM samples are comparable to values measured over the Sargasso Sea and for samples collected at the Tudor Hill tower. Sea-salt aerosols do not appear to impede the collection of mineral aerosols by the buoy-mounted sampler. [Copyright &y& Elsevier]

Abstract: Mode-1 internal tides were observed the western North Atlantic using an ocean acoustic tomography array deployed in 1991–1992 centered on 25°N, 66°W. The pentagonal array, 700-km across, acted as an antenna for mode-1 internal-tides. Coherent internal-tide waves with O(1m) displacements were observed traveling in several directions. Although the internal tides of the region were relatively quiescent, they were essentially phase locked over the 200–300 day data record lengths. Both semidiurnal and diurnal internal waves were detected, with wavenumbers consistent with those calculated from hydrographic data. The M 2 internal-tide energy flux was estimated to be about 70Wm−1, suggesting that mode-1 waves radiate 0.2GW of energy, with large uncertainty, from the Caribbean island chain at this frequency. A global tidal model (TPXO 5) suggested that 1–2GW is lost from the M 2 barotropic tide over this region, but the precise value was uncertain because the complicated topography makes the calculation problematic. In any case, significant conversion of barotropic to baroclinic tidal energy does not occur in the western North Atlantic basin. It is apparent, however, that mode-1 internal tides have very weak decay and retain their coherence over great distances, so that ocean basins may be filled up with such waves. Observed diurnal amplitudes were an order of magnitude larger than expected. The amplitude and phase variations of the K 1 and O 1 constituents observed over the tomography array were consistent with the theoretical solutions for standing internal waves near their turning latitude. The energy densities of the resonant diurnal internal waves were roughly twice those of the barotropic tide at those frequencies. [Copyright &y& Elsevier]

Abstract: Sixteen surface microlayer samples and corresponding subsurface water samples were collected in the western North Atlantic during April–May 2003 to study the distribution and cycling of dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) and the factors influencing them. In the surface microlayer, high concentrations of DMS appeared mostly in the samples containing high levels of chlorophyll a, and a significant correlation was found between DMS and chlorophyll a concentrations. In addition, microlayer DMS concentrations were correlated with microlayer DMSPd (dissolved) concentrations. DMSPd was found to be enriched in the microlayer with an average enrichment factor (EF) of 5.19. However, no microlayer enrichment of DMS was found for most samples collected. Interestingly, the DMS production rates in the microlayer were much higher than those in the subsurface water. Enhanced DMS production in the microlayer was likely due to the higher concentrations of DMSPd in the microlayer. A consistent pattern was observed in this study in which the concentrations of DMS, DMSPd, DMSPp (particulate) and chlorophyll a in the microlayer were closely related to their corresponding subsurface water concentrations, suggesting that these constituents in the microlayer were directly dependent on the transport from the bulk liquid below. Enhanced DMS production in the microlayer further reinforces the conclusion that the surface microlayer has greater biological activity relative to the underlying water. [Copyright &y& Elsevier]

Abstract: A one-dimensional quasi-Eulerian model, describing the biological and chemical interactions of autotrophic and heterotrophic plankton populations within the upper 100m of the water column, was used to explain the relative impact of iron fertilization from Saharan dust on phosphorus cycling by the cyanobacterium, Trichodesmium spp. We examined the Caribbean surface waters off the west coast of Barbados using seasonal cases of dust delivery (summer peak) in relation to periods of elevated phosphorus stocks found in episodic pulses of Amazon River water advected past Barbados by the Guiana Current. The additional iron and phosphorus supplied by fluvial sources, available after biological depletion of nitrogen, could alleviate the growth limitation of Trichodesmium far downstream of the river plumes. The model results were compared with measurements made of Trichodesmium stocks 8km off the west coast of Barbados. Modeled concentrations within the low-salinity Amazon plumes reached ∼7.4mgchlm−2, as seen at Barbados. In the absence of the low-salinity signal, the Trichodesmium biomass shifted to phosphorus limitation with little response to iron fertilization. This indicates that Trichodesmium stocks may indeed be mainly a function of phosphorus availability within the upper water column. Therefore, the supply of phosphorus from subtropical/tropical rivers, such as the Amazon and Orinoco, limits the potential cyanophyte response, despite adequate atmospheric iron delivery. This alters our view not only of the western North Atlantic nitrogen budget, but potentially several regions downstream of low N:P river systems. [Copyright &y& Elsevier]

Ten ODP sites drilled in a depth transect (2164–4775 m water depth) during Leg 172 recovered high-deposition rate (>20 cm/kyr) sedimentary sections from sediment drifts in the western North Atlantic. For each site an age model covering the past 0.8–0.9 Ma has been developed. The time scales have a resolution of 10–20 kyr and are derived by tuning variations of estimated carbonate content to the orbital parameters precession and obliquity. Based on the similarity in the signature of proxy records and the spectral character of the time series, the sites are divided into two groups: precession cycles are better developed in carbonate records from a group of shallow sites (2164–2975 m water depth, Sites 1055–1058) while the deeper sites (2995–4775 m water depth, Sites 1060–1063) are characterized by higher spectral density in the obliquity band. The resulting time scales show excellent coherence with other dated carbonate and isotope records from low latitudes. Besides the typical Milankovitch cyclicity significant variance of the resulting carbonate time series is concentrated at millennial-scale changes with periods of about 12, 6, 4, 2.5, and 1.5 kyr. Comparisons of carbonate records from the Blake Bahama Outer Ridge and the Bermuda Rise reveal a remarkable similarity in the time and frequency domain indicating a basin-wide uniform sedimentation pattern during the last 0.9 Ma. [Copyright &y& Elsevier]

• We reconstruct iceberg discharge for the past 135,000 yrs near Newfoundland. • Iceberg flux increased during each Heinrich event in the western North Atlantic. • Compared to the eastern North Atlantic, the western iceberg flux is higher. • Heinrich layers 3 and 6 cannot solely be the result of foraminifera dissolution. A series of catastrophic iceberg and meltwater discharges to the North Atlantic, termed Heinrich events, punctuated the last ice age. During Heinrich events, coarse terrigenous debris released from the drifting icebergs was preserved in deep-sea sediments, serving as an indicator of iceberg passage. Quantifying the vertical flux of ice-rafted debris (IRD) in open-ocean settings can resolve questions regarding the timing and spatial variation in ice sheet calving intensity. In this study, 230Th xs -based IRD flux throughout the last glacial period was measured in a deep-sea sediment core from the western North Atlantic, and complemented by data spanning 0-32 ka from a sediment core in the Labrador Sea. The cores were recovered from sites downstream from Hudson Strait, a likely conduit for icebergs calving from the Laurentide ice sheet (LIS). We compare our results with equivalent existing data from the eastern North Atlantic and show that the two cores in our study have higher IRD fluxes during all Heinrich events, notably including events H3 (∼31 ka) and H6 (∼60 ka). This study demonstrates that the LIS played a role in all Heinrich events, and raises the likelihood that a single mechanism can account for the genesis of these events. [ABSTRACT FROM AUTHOR]