Manganini Steven J.

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Manganini

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Lateral organic carbon supply to the deep Canada Basin

(American Geophysical Union, 2008-06-12) Hwang, Jeomshik ; Eglinton, Timothy I. ; Krishfield, Richard A. ; Manganini, Steven J. ; Honjo, Susumu

Understanding the processes driving the carbon cycle in the Arctic Ocean is important for assessing the impacts of the predicted rapid and amplified climate change in this region. We analyzed settling particle samples intercepted by a time-series sediment trap deployed in the abyssal Canada Basin (at 3067 m) in order to examine carbon export to the deep Arctic Ocean. Strikingly old radiocarbon ages (apparent mean 14C age = ∼1900 years) of the organic carbon, abundant lithogenic material (∼80%), and mass flux variations temporally decoupled from the cycle of primary productivity in overlying surface waters together suggest that, unlike other ocean basins, the majority of the particulate organic carbon entering the deep Canada Basin is supplied from the surrounding margins.
Pelagic diatom fluxes I : size fractioned time-series results from subarctic Pacific Station Papa during 1982-1983

(Woods Hole Oceanographic Institution, 1985-12) Takahashi, Kozo ; Povio, Danielle N. ; Billings, John D. ; Manganini, Steven J.

A time series vertical flux assessment of pelagic diatoms was conducted during September, 1982 through September, 1983 at subarctic Pacific Station PAPA (50°N, 145°W; water depth 4200 m) using PARFLUX sediment traps deployed at 1000 and 38000 m. The time series sediment trap samples were collected for 11 to 16-day periods during the year; a total of 24 samples represent a full year's record of flux. Eighteen taxonomic groups of diatoms were enumerated, based on a census of four wet-sieved size fractions: 250-1000μm, 125-250μm, 63-125μm, and < 63μm. In order to study the sinking processes of diatoms, detailed information on frustule integrity was acquired. For example , counts of single valves were separated from frustules. Size-fractioned fluxes of all the counting groups are graphically presented, which provides a data base for further investigations.
Particle fluxes, south central Black Sea : 1982-1985

(Woods Hole Oceanographic Institution, 1987-05) Honjo, Susumu ; Manganini, Steven J. ; Asper, Vernon L. ; Hay, Bernward J. ; Karowe, Amy

Annual particle fluxes were measured by sediment traps deployed at a station about 40 km north of Amasra, Southern Black Sea, by an international team of oceanographers from Germany, Turkey, and the United States. This experiment continuously monitored oceanic particle flux for two and a half years from October 28, 1982 to April 6, 1985 at approximately two-week intervals at 250 m and 1200 m below the surface using 1.2 m2 Mark 5-12 time-series sediment traps. The water depth at this station was about 2,200 m and both traps were situated within the anoxic layer of the Black Sea. The collected flux samples were analyzed at the Woods Hole Oceanographic Institution to document the basic sedimentary characteristics using a quarter of each sample split. In the first data file from this experiment, total mass, carbonate, noncombustible, combustible, opal (biogenic silica), organic carbon, and organic nitrogen fluxes data are presented in bar graphs and detailed tables, in unit samples covering a two-week period at each depth. The Black Sea Sedimentation Data File is intended to provide source data on particle fluxes from this unique ocean environment for further investigation and for planning advanced research programs.
Cruise report: JGOFS Leg I International study of the North Atlantic Bloom : R/V Atlantis II Voyage 119.2, Funchal to Reykjavik, March/April 1989

(Woods Hole Oceanographic Institution, 1989-07) Honjo, Susumu ; Manganini, Steven J. ; Krishfield, Richard A.

With the support of the National Science Foundation, we have completed the first cruise devoted to the GOFS and JGOFS program for the North Atlantic Bloom studies between March 28 and April 6 on board R/V Atlantis II. The major task of this cruise, to deploy bottom-tethered mooring arrays with time-series sediment traps along with current meters at two critical stations, 34°N and 47°N along 20°W, was accomplished. All 6 sediment traps, 3 on each array, were set at 14-day intervals for 13 periods from April 3 to September 26, 1989. Their opening and closing times were synchronized throughout the period of deployment. The arrays and instruments will be recovered and redeployed in September/October, 1989. Ancillary water column data, such as CTD, fluorometry, pigments, and major nutrient distribution, were also successfully completed (except for transmissometry profiling at the 47°N station) in order to understand the prebloom setting at JGOFS 34°N, 47°N, and 60°N stations. At the 47°N station on April 2, the mixed layer depth was 248m.
Biogenic particle fluxes at the 34°N 21°W and 48°N 21°W stations, 1989-1990 : methods and analytical data compilation

(Woods Hole Oceanographic Institution, 1992-03) Honjo, Susumu ; Manganini, Steven J.

This technical report presents the results of analyses on opal, organic carbon, nitrogen and phosphorus content in each of 156 specimen samples collected from the moored sediment trap experiment that was a part of JGOFS North Atlantic Bloom Experiment. The analyzed samples represent a spatio-temporal matrix formed by 6 time-series sediment traps that provided 26 periods of uniform and synchronized periods of 14 days, except for one longer and one shorter period. Traps were deployed at 3 depths, 1 km, 2 km and 0.7 km above the bottom, and at 2 stations, 34°N 21°W and 48°N 21°W from April 4, 1989 to April 17, 1990, as shown in Tables 1 and 2. There was an 20-day hiatus in September /October 1989 for changeover of the trap moorings. Some samples were unusable because of the in trusion of fish. Samples were separated into several aliquots by wet-splitting, then water sieved into larger-than- and smaller-than-1-mm sizes. The fluxes of biogeochemical elements and constituents were determined on these aliquots and size fractions for: carbonate by vacuum gasometric method; opal by selective leaching method; reactive phosphorus by high temperature oxidation hydrolysis method; and organic carbon and nitrogen by applying an elementary analyzer. The annual fluxes, fluxes during the bloom, pre- and post-bloom episodes were normalized to a 365-day calendar year (Table 6) and are summarized in Tables 7 to 12. Variabilty of particle fluxes by each period at the two stations in terms of size fractions, sedimentary constituents and elements are shown in Tables 13 and 14. The molar ratios between pairs of critical biogeochemical elements during each episode and annually, shown at various depths and stations, are included in Tables 10 through 14.
Lithogenic particle transport trajectories on the Northwest Atlantic Margin

(American Geophysical Union, 2020-12-04) Hwang, Jeomshik ; Blusztajn, Jerzy S. ; Giosan, Liviu ; Kim, Minkyoung ; Manganini, Steven J. ; Montluçon, Daniel ; Toole, John M. ; Eglinton, Timothy I.

The neodymium isotopic composition of the detrital (lithogenic) fraction (εNd‐detrital) of surface sediments and sinking particles was examined to constrain transport trajectories associated with hemipelagic sedimentation on the northwest Atlantic margin. The provenance of resuspended sediments and modes of lateral transport in the water column were of particular interest given the energetic hydrodynamic regime that sustains bottom and intermediate nepheloid layers over the margin. A large across‐margin gradient of ∼5 εNd units was observed for surface sediments, implying strong contrasts in sediment provenance, with εNd‐detrital values on the lower slope similar to those of “upstream regions” (Scotian margin) under the influence of the Deep Western Boundary Current (DWBC). Sinking particles collected at three depths at a site (total water depth, ∼3,000 m) on the New England margin within the core of the DWBC exhibited a similarly large range in εNd‐detrital values. The εNd‐detrital values of particles intercepted at intermediate water depths (1,000 and 2,000 m) were similar to each other but significantly higher than those at 3,000 m (∼50 m above the seafloor). These observations suggest that lithogenic material accumulating in the upper two traps was primarily advected in intermediate nepheloid layers emanating from the adjacent shelf, while that at 3,000 m is strongly influenced by sediment resuspension and along‐margin, southward lateral transport within the bottom nepheloid layer via entrainment in the DWBC. Our results highlight the importance of both along‐ and across‐margin sediment transport as vectors for lithogenic material and associated organic carbon transport.
Biological and physical controls on the flux and characteristics of sinking particles on the Northwest Atlantic margin

(John Wiley & Sons, 2017-06-01) Hwang, Jeomshik ; Manganini, Steven J. ; Park, Jonglin ; Montlucon, Daniel B. ; Toole, John M. ; Eglinton, Timothy I.

Biogenic matter characteristics and radiocarbon contents of organic carbon (OC) were examined on sinking particle samples intercepted at three nominal depths of 1000 m, 2000 m, and 3000 m (∼50 m above the seafloor) during a 3 year sediment trap program on the New England slope in the Northwest Atlantic. We have sought to characterize the sources of sinking particles in the context of vertical export of biogenic particles from the overlying water column and lateral supply of resuspended sediment particles from adjacent margin sediments. High aluminum (Al) abundances and low OC radiocarbon contents indicated contributions from resuspended sediment which was greatest at 3000 m but also significant at shallower depths. The benthic source (i.e., laterally supplied resuspended sediment) of opal appears negligible based on the absence of a correlation with Al fluxes. In comparison, CaCO3 fluxes at 3000 m showed a positive correlation with Al fluxes. Benthic sources accounted for 42 ∼ 63% of the sinking particle flux based on radiocarbon mass balance and the relationship between Al flux and CaCO3 flux. Episodic pulses of Al at 3000 m were significantly correlated with the near-bottom current at a nearby hydrographic mooring site, implying the importance of current variability in lateral particle transport. However, Al fluxes at 1000 m and 2000 m were coherent but differed from those at 3000 m, implying more than one mode of lateral supply of particles in the water column.
Temporal and spatial variability of particle transport in the deep Arctic Canada Basin

(John Wiley & Sons, 2015-04-11) Hwang, Jeomshik ; Kim, Minkyoung ; Manganini, Steven J. ; McIntyre, Cameron P. ; Haghipour, Negar ; Park, Jong Jin ; Krishfield, Richard A. ; Macdonald, Robie W. ; McLaughlin, Fiona A. ; Eglinton, Timothy I.

To better understand the current carbon cycle and potentially detect its change in the rapidly changing Arctic Ocean, we examined sinking particles collected quasi-continuously over a period of 7 years (2004–2011) by bottom-tethered sediment trap moorings in the central Canada Basin. Total mass flux was very low (<100 mg m−2 d−1) at all sites and was temporally decoupled from the cycle of primary production in surface waters. Extremely low radiocarbon contents of particulate organic carbon and high aluminum contents in sinking particles reveal high contributions of resuspended sediment to total sinking particle flux in the deep Canada Basin. Station A (75°N, 150°W) in the southwest quadrant of the Canada Basin is most strongly influenced while Station C (77°N, 140°W) in the northeast quadrant is least influenced by lateral particle supply based on radiocarbon content and Al concentration. The results at Station A, where three sediment traps were deployed at different depths, imply that the most likely mode of lateral particle transport was as thick clouds of enhanced particle concentration extending well above the seafloor. At present, only 1%–2% of the low levels of new production in Canada Basin surface waters reaches the interior basin. Lateral POC supply therefore appears to be the major source of organic matter to the interior basin. However, ongoing changes to surface ocean boundary conditions may influence both lateral and vertical supply of particulate material to the deep Canada Basin.
Particle fluxes, Northeastern Nordic Seas, 1983-1986

(Woods Hole Oceanographic Institution, 1987-04) Honjo, Susumu ; Manganini, Steven J. ; Karowe, Amy ; Woodward, Bonnie L.

Seventy-nine particle. flux samples were collected from 1983 to 1986 using 7 automated time-series sediment traps at 6 stations distributed in the northern and eastern portion of the Nordic Seas as part of a German/U.S. joint program on arctic sedimentation studies. Each sample represents either one month or two weeks of sedimentation at approximately 400 m above the sea floor. In this data file the results of laboratory analysis conducted at the Woods Hole Oceanographic Institution, U.S.A. of the main sedimentological criteria: total mass, carbonate, opal, combustible, organic carbon, nitrogen, and lithogenic mass are presented in both tabular and histogram form. Results from the southern and western portion of the Nordic Seas will be published as they become available.

Manganini Steven J.

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