Dartmouth, Canada

The Bedford Institute of Oceanography is a major Government of Canada ocean research facility located in Dartmouth, Nova Scotia. BIO is the largest ocean research station in Canada. Established in 1962 as Canada's first, and currently largest, federal centre for oceanographic research, BIO derives its name from the Bedford Basin, an inland bay comprising the northern part of Halifax Harbour, upon which it is located.Spread out over 40 acres of a former Royal Canadian Navy property near Shannon Park in Dartmouth, BIO consists of a series of interconnected buildings housing research labs and offices, as well as docks for Canadian Coast Guard and RCN research vessels.As the federal government seeks to concentrate its operations in the Halifax Regional Municipality, BIO is being considered for additional office buildings to house other non-oceanographic and non-research organizations and their employees. As such, new buildings have been built for the Canadian Coast Guard as well as Environment Canada in recent years. Wikipedia.

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Based on a unique dataset collected during a research cruise to the Irminger Sea in April 2015, a new paper reveals a strong link between atmospheric forcing, deep convection, ocean ventilation and anthropogenic carbon sequestration. The Irminger Sea, a small ocean basin between Greenland and Iceland, is known for its harsh and extreme weather conditions during winter. Research cruises that take measurements in the subpolar North Atlantic almost exclusively do so in summer, although the area is particularly interesting in the convectively active winter season. Wintertime on-board ship measurements in the Irminger Sea were collected in April 2015 by scientists from the Bjerknes Centre for Climate research, as part of the SNACS project funded by the Norwegian Research Council. The results are now published in Nature Communications by Friederike Fröb, a PhD student at the Geophysical Institute of the University of Bergen and the Bjerknes Centre for Climate Research, with colleagues from the University of Bergen, Uni Research Bergen, the University of Toronto and the Bedford Institute of Oceanography, both in Canada. Compared to the far more famous Labrador Sea where deep convection is observed almost every year, convection in the Irminger Sea is more rare, and more variable in extent and strength. The 2015 data show record winter mixed layers of 1,400m depth -- usually observed are 400m. The last time winter mixing had been that deep was probably in the mid-1990s, however, there is only indirect evidence for that; no direct measurements are available from that time. In the late 2000s, during the winters 2007/08 and 2011/12, convection down to between 800m and 1,000m was observed by ARGO floats. With the newly collected data in 2015, oxygen and carbon concentrations during active convection have been determined as well. These data show that oxygen and anthropogenic CO2 concentrations were both almost saturated with respect to the atmosphere in the upper water column. This resulted in a replenishment of depleted oxygen levels at mid-depth as well as a sequestration of large amounts of anthropogenic carbon to the deep ocean. Compared to historic cruise data in 1997 and 2003 covering the same transect as the 2015 cruise, the anthropogenic carbon storage rate almost tripled in response to the large variability in the physical climate system. The main driver for that extreme convective event in 2015 was the strong heat flux from the water column, a consequence of exceptionally strong winds that developed that winter around the southern tip of Greenland. The winter 2014-2015 was also the coldest on record in the North Atlantic, a phenomenon known as the 'cold-blob'. This cold-blob has been tied to a reduced Atlantic Meridional Overturning Circulation as a consequence of increased freshwater runoff from the melting Greenland Ice Sheet and the Arctic, which increases ocean stratification. Although observations of one extreme event during winter can not be used to reject a hypothesis that is based on long-term trends, global climate model predictions are definitely challenged. The ability or lack of such to resolve small scale atmospheric phenomena like the ones in the Irminger Sea might be of greater relevance to simulate convective processes in the North Atlantic than anticipated. Overall, the cruise observations reveal the strong, direct link between atmospheric forcing, oceanic heat loss, ventilation, and anthropogenic carbon storage in the Irminger Sea. Further, the cruise data shows the necessity of ongoing, continuous data collection in remote areas also during harsh seasons, allowing to study highly variable natural processes as well as the impact of anthropogenic climate change on ocean biogeochemistry.

Kieke D.,University of Bremen | Yashayaev I.,Bedford Institute of Oceanography
Progress in Oceanography | Year: 2015

Labrador Sea Water (LSW), the lightest contribution to North Atlantic Deep Water (NADW) and one of the most prominent water masses of the subpolar North Atlantic, has seen remarkable changes over the past century. LSW originates in the Labrador Sea, where it is formed through wintertime ocean convection of varying intensity, depth and spatial extent. Formation of LSW, followed by its respective injection into the mid-depth circulation system, is mandatory for ventilating and renewing water layers of the interior ocean. Indispensably important for unraveling the history of variability in formation and properties of LSW as well as for mapping its large-scale spreading and export are sustained physical and chemical observations from the deep ocean. These observations started at the beginning of the 20th century from occasional mostly national surveys and today constitute large-scale multi-national collaborative efforts including a vast arsenal of sophisticated instrumentation. In a historical context, we revisit major milestones over the past 100. years which have established and are constantly adding to shaping today's knowledge on LSW, and present first details on the latest vintage of LSW generated during the strong winter of 2013/2014. Respective Argo data reveal mixed-layer depths greater than 1700. m marking formation of a new cold and fresh anomaly that has spread since then over the subpolar North Atlantic. We further summarize the on-going observational efforts in the subpolar North Atlantic and present a compilation of hydrographic standard lines that serve to provide top-to-bottom information on NADW components. © 2014 Elsevier Ltd.

Zhang B.,Nanjing University of Information Science and Technology | Zhang B.,Bedford Institute of Oceanography | Perrie W.,Bedford Institute of Oceanography
Bulletin of the American Meteorological Society | Year: 2012

A C-band Cross-Polarization Ocean (C-2PO) model is presented, based on RADARSAT-2 fine quad-polarization mode SAR measurements. The C-2PO model is insensitive to wind direction and radar incidence angle, and thus it is a straightforward mapping of observed cross-polarized NRCS to wind speed. C-2PO avoids the errors in wind speed retrievals that can occur in CMOD5.N due to errors in wind directions. In presently available quad-polarization data, the observed NRCS in cross polarization increases linearly with wind speed, up to 26 m s -1, which indicates that it could potentially be used to retrieve hurricane winds, including eye structure observations. In comparisons of wind speeds derived from C-2PO and CMOD5.N with buoy data, SFMR measurements, and H*Wind analysis, we show that C-2PO has slightly smaller scatter than CMOD5.N for wind speeds <20 m s -1; for wind speeds in the range of 20- 38 m s -1, the difference in scatter is significant. © 2012 American Meteorological Society.

Talling P.J.,UK National Oceanography Center | Paull C.K.,Monterey Bay Aquarium Research Institute | Piper D.J.W.,Bedford Institute of Oceanography
Earth-Science Reviews | Year: 2013

Subaqueous sediment density flows are one of the volumetrically most important processes for moving sediment across our planet, and form the largest sediment accumulations on Earth (submarine fans). They are also arguably the most sparely monitored major sediment transport processes on our planet. Significant advances have been made in documenting their timing and triggers, especially within submarine canyons and delta-fronts, and freshwater lakes and reservoirs, but the sediment concentration of flows that run out beyond the continental slope has never been measured directly. This limited amount of monitoring data contrasts sharply with other major types of sediment flow, such as river systems, and ensure that understanding submarine sediment density flows remains a major challenge for Earth science. The available monitoring data define a series of flow types whose character and deposits differ significantly. Large (>100km3) failures on the continental slope can generate fast-moving (up to 19m/s) flows that reach the deep ocean, and deposit thick layers of sand across submarine fans. Even small volume (0.008km3) canyon head failures can sometimes generate channelised flows that travel at >5m/s for several hundred kilometres. A single event off SE Taiwan shows that river floods can generate powerful flows that reach the deep ocean, in this case triggered by failure of recently deposited sediment in the canyon head. Direct monitoring evidence of powerful oceanic flows produced by plunging hyperpycnal flood water is lacking, although this process has produced shorter and weaker oceanic flows. Numerous flows can occur each year on river-fed delta fronts, where they can generate up-slope migrating crescentic bedforms. These flows tend to occur during the flood season, but are not necessarily associated with individual flood discharge peaks, suggesting that they are often triggered by delta-front slope failures. Powerful flows occur several times each year in canyons fed by sand from the shelf, associated with strong wave action. These flows can also generate up-slope migrating crescentic bedforms that most likely originate due to retrogressive breaching associated with a dense near-bed layer of sediment. Expanded dilute flows that are supercritical and fully turbulent are also triggered by wave action in canyons. Sediment density flows in lakes and reservoirs generated by plunging river flood water have been monitored in much greater detail. They are typically very dilute (<0.01vol.% sediment) and travel at <50cm/s, and are prone to generating interflows within the density stratified freshwater. A key objective for future work is to develop measurement techniques for seeing through overlying dilute clouds of sediment, to determine whether dense near-bed layers are present. There is also a need to combine monitoring of flows with detailed analyses of flow deposits, in order to understand how flows are recorded in the rock record. Finally, a source-to-sink approach is needed because the character of submarine flows can change significantly along their flow path. © 2013 Elsevier B.V.

Frank K.T.,Bedford Institute of Oceanography | Petrie B.,Bedford Institute of Oceanography | Fisher J.A.D.,Queen's University | Leggett W.C.,Queen's University
Nature | Year: 2011

Overfishing of large-bodied benthic fishes and their subsequent population collapses on the Scotian Shelf of Canada's east coast and elsewhere resulted in restructuring of entire food webs now dominated by planktivorous, forage fish species and macroinvertebrates. Despite the imposition of strict management measures in force since the early 1990s, the Scotian Shelf ecosystem has not reverted back to its former structure. Here we provide evidence of the transient nature of this ecosystem and its current return path towards benthic fish species domination. The prolonged duration of the altered food web, and its current recovery, was and is being governed by the oscillatory, runaway consumption dynamics of the forage fish complex. These erupting forage species, which reached biomass levels 900% greater than those prevalent during the pre-collapse years of large benthic predators, are now in decline, having outstripped their zooplankton food supply. This dampening, and the associated reduction in the intensity of predation, was accompanied by lagged increases in species abundances at both lower and higher trophic levels, first witnessed in zooplankton and then in large-bodied predators, all consistent with a return towards the earlier ecosystem structure. We conclude that the reversibility of perturbed ecosystems can occur and that this bodes well for other collapsed fisheries. © 2011 Macmillan Publishers Limited. All rights reserved.

Although many studies have examined foraging success across seagrass complexity, few have identified underlying behavioural mechanisms or examined effects of belowground complexity. Here, I used a new habitat complexity index ( IBG), behavioural data, and laboratory manipulations of artificial above- and belowground structures and predator sizes to understand foraging of invasive green crabs ( Carcinus maenas) on soft-shell clams ( Mya arenaria) in seagrass ( Zostera marina) beds. IBG was calculated as interstitial area between rhizomes (i.e., belowground complexity) divided by claw area; belowground complexity was varied while claw area was held constant. This meant that as IBG increased, belowground complexity itself decreased. Belowground complexity strongly affected crab foraging, and a sigmoid function described predation rate across increasing IBG. This relationship was not evident when aboveground complexity was high (i.e., interstitial area between shoots was small), and no patterns in predation across a gradient of aboveground complexity were observed. Important behavioural mechanisms included encounter rate with prey and the probability of capture upon encounter, both of which increased hyperbolically as IBG increased, and handling time per prey, which decreased exponentially as IBG increased. Most handling time was spent excavating prey from the sediments. Predator size did not change these relationships, although larger crabs had more difficulty capturing prey at low IBG than smaller crabs. Clearly, success of crabs feeding on infauna in seagrass beds is limited most by claw size relative to opening size from which prey are extracted. IBG incorporates this limitation, and can be used to predict effects of habitat complexity on foraging success of epibenthic predators in various habitat types. © 2013.

Kenchington T.J.,Bedford Institute of Oceanography
Fish and Fisheries | Year: 2014

The 29 estimators of natural mortality (M) that have been proposed for 'information-limited' fisheries are reviewed, together with a new alternative presented here. Each is applied to 13 example populations for which well-founded estimates are available of both M and the estimators' parameters. None of the 30 can provide accurate estimates for every species, and none appears sufficiently precise for use in analytical stock assessments, while several perform so poorly as to have no practical utility. If the growth coefficient K has been reliably estimated, either M = 1.5 K or Pauly's long-established estimator can provide useful estimates of M, but they fail with species that have long adult lives after swift juvenile growth, with those that never reach their asymptotic lengths and with species that otherwise deviate from archetypal teleost life histories. If a pre-exploitation maximum observed age (Tmax) can be established, M can be estimated for both teleosts and sharks using M = 4.3/Tmax but that seriously underestimates when the effective sample size (ne) is large and overestimates with species showing pronounced senescence. The new estimator presented here addresses ne but is upset by even mild senescence. Some estimators of M-at-size, particularly ones recently advanced by Gislason et al. and Charnov et al., also show promise but require further examination. It is recommended that fisheries scientists measure M by more advanced methods whenever possible. If 'information-limited' estimators must be used, their uncertainties should be acknowledged and their errors propagated into management advice. © Her Majesty the Queen in Right of Canada 2013.

Mosher D.C.,Bedford Institute of Oceanography
Marine and Petroleum Geology | Year: 2011

It is the intent of this paper to explore a significant extent of an entire passive continental margin for hydrate occurrence to understand hydrate modes of occurrence, preferred geologic settings and estimate potential volumes of methane. The presence of gas hydrates offshore of eastern Canada has long been inferred from estimated stability zone calculations, but little physical evidence has been offered. An extensive set of 2-D and 3-D, single and multi-channel seismic reflection data comprising in excess of 140,000 line-km was analyzed. Bottom simulating reflections (BSR) were unequivocally identified at seven sites, ranging between 250 and 445 m below the seafloor and in water depths of 620-2850 m. The combined area of the BSRs is 9311 km2, which comprises a small proportion of the entire theoretical stability zone along the Canadian Atlantic margin (∼715,165 km2). The BSR within at least six of these sites lies in a sedimentary drift deposit or sediment wave field, indicating the likelihood of grain sorting and potential porosity and permeability (reservoir) development. Although there are a variety of conditions required to generate and recognize a BSR, one might assume that these sites offer the most potential for highest hydrate concentration and exploitation. Total hydrate in formation at the sites of recognized BSR's is estimated at 17 to 190 × 109 m3 or 0.28 to 3.12 × 1013 m3 of methane gas at STP. Although it has been shown that hydrate can exist without a BSR, the results from this regional study argue that conservative estimates of the global reserve of hydrate along continental margins are necessary. © 2011.

Jerosch K.,Bedford Institute of Oceanography
Journal of Marine Systems | Year: 2013

The paper describes an approach for a quality controlled mapping of grain sizes and sediment textures for the Beaufort Shelf in the Canadian Arctic. The approach is based on grain size data collected during the Nahidik Program (2005-2009) and earlier. A replenishment of grain size data since the 1980s, as well as the consideration of correlating parameters (bathymetry, slope and sediment input) to a cokriging algorithm, amends the former way of mapping the surficial sediments of the Beaufort Shelf. The cokriging analysis showed that the simulation of a sediment input by the Mackenzie River, modeled as a cost-distance function, was the key variable in reducing the errors of the output estimate. Furthermore, the approach compares the geostatistical interpolation methods of ordinary kriging and cokriging and recommends the use of a combination of both. The predicted mean standard errors showed that in this study cokriging was the superior interpolation method for clay, silt and sand while ordinary kriging was more suitable for gravel. A new sediment texture map, based on the grain size maps, is provided according to commonly used grain size and sediment type classification systems. © 2012 Elsevier B.V.

Jessop B.M.,Bedford Institute of Oceanography
Canadian Journal of Fisheries and Aquatic Sciences | Year: 2010

Latitudinal variability in length and age at maturity and annual growth rate for the American eel (Anguilla rostrata) along the Atlantic coast of North America was examined with respect to life history strategies and theory. Maturing (silver phase) female lengths and ages increased with increasing latitude (and distance) from the Sargasso Sea spawning site, as did male ages but not lengths. Growth rates for females (and males) declined with increasing latitude south of 44 °N latitude, approximately the entrance to the Cabot Strait, but were constant or increased within the Gulf of St. Lawrence and St. Lawrence River, depending on the analysis method. The growing season and the number of degree-days ≥ 10 °C declined with increasing latitude. Female growth rates adjusted for the number of degree-days were approximately constant south of 44 °N but increased further north, suggesting countergradient variation in growth. The temperature-size rule (increase in body size at lower temperatures) evidently applies to American eel females, but not males. No current life history model provides a satisfactory explanatory mechanism for the temperature-size rule and for anguillid life history strategies. A genetic link is proposed between increasing age (length) at elver and silver eel stages with increasing distance from the spawning area.

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