Small scale model static acoustic investigation of hybrid high lift systems combining upper surface blowing with the internally blown flap

A static acoustic and propulsion test of a small radius Jacobs-Hurkamp and a large radius Flex Flap combined with four upper surface blowing (USB) nozzles was performed. Nozzle force and flow data, flap trailing edge total pressure survey data, and acoustic data were obtained. Jacobs-Hurkamp flap surface pressure data, flow visualization photographs, and spoiler acoustic data from the limited mid-year tests are reported. A pressure ratio range of 1.2 to 1.5 was investigated for the USB nozzles and for the auxiliary blowing slots. The acoustic data were scaled to a four-engine STOL airplane of roughly 110,000 kilograms or 50,000 pounds gross weight, corresponding to a model scale of approximately 0.2 for the nozzles without deflector. The model nozzle scale is actually reduced to about .17 with deflector although all results in this report assume 0.2 scale factor. Trailing edge pressure surveys indicated that poor flow attachment was obtained even at large flow impingement angles unless a nozzle deflector plate was used. Good attachment was obtained with the aspect ratio four nozzle with deflector, confirming the small scale wind tunnel tests

Paleo-methane emissions recorded in foraminifera near the landward limit of the gas hydrate stability zone offshore western Svalbard

We present stable isotope and geochemical data from four sediment cores from west of Prins Karls Forland (ca. 340 m water depth), offshore western Svalbard, recovered from close to sites of active methane seepage, as well as from shallower water depths where methane seepage is not presently observed. Our analyses provide insight into the record of methane seepage in an area where ongoing ocean warming may be fueling the destabilization of shallow methane hydrate. The ?13C values of benthic and planktonic foraminifera at the methane seep sites show distinct intervals with negative values (as low as ?27.8‰) that do not coincide with the present-day depth of the sulfate methane transition zone (SMTZ). These intervals are interpreted to record long-term fluctuations in methane release at the present-day landward limit of the gas hydrate stability zone (GHSZ). Shifts in the radiocarbon ages obtained from planktonic foraminifera toward older values are related to methane-derived authigenic carbonate overgrowths of the foraminiferal tests, and prevent us from establishing the chronology of seepage events. At shallower water depths, where seepage is not presently observed, no record of past methane seepage is recorded in foraminifera from sediments spanning the last 14 ka cal BP (14C-AMS dating). ?13C values of foraminiferal carbonate tests appear to be much more sensitive to methane seepage than other sediment parameters. By providing nucleation sites for authigenic carbonate precipitation, foraminifera thus record the position of even a transiently stable SMTZ, which is likely to be a characteristic of temporally variable methane fluxes

Ice loss from the East Antarctic Ice Sheet during late Pleistocene interglacials

Understanding ice sheet behaviour in the geological past is essential for evaluating the role of the cryosphere in the climate system and for projecting rates and magnitudes of sea level rise in future warming scenarios1,2,3,4. Although both geological data5,6,7 and ice sheet models3,8 indicate that marine-based sectors of the East Antarctic Ice Sheet were unstable during Pliocene warm intervals, the ice sheet dynamics during late Pleistocene interglacial intervals are highly uncertain3,9,10. Here we provide evidence from marine sedimentological and geochemical records for ice margin retreat or thinning in the vicinity of the Wilkes Subglacial Basin of East Antarctica during warm late Pleistocene interglacial intervals. The most extreme changes in sediment provenance, recording changes in the locus of glacial erosion, occurred during marine isotope stages 5, 9, and 11, when Antarctic air temperatures11 were at least two degrees Celsius warmer than pre-industrial temperatures for 2,500 years or more. Hence, our study indicates a close link between extended Antarctic warmth and ice loss from the Wilkes Subglacial Basin, providing ice-proximal data to support a contribution to sea level from a reduced East Antarctic Ice Sheet during warm interglacial intervals. While the behaviour of other regions of the East Antarctic Ice Sheet remains to be assessed, it appears that modest future warming may be sufficient to cause ice loss from the Wilkes Subglacial Basin

Glacial‐interglacial variations in sediment organic carbon accumulation and benthic foraminiferal assemblages on the Bermuda Rise (ODP Site 1063) during MIS 13 to 10

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94866/1/palo1807.pd

Comparative Composition, Diversity and Trophic Ecology of Sediment Macrofauna at Vents, Seeps and Organic Falls

Sediments associated with hydrothermal venting, methane seepage and large organic falls such as whale, wood and plant detritus create deep-sea networks of soft-sediment habitats fueled, at least in part, by the oxidation of reduced chemicals. Biological studies at deep-sea vents, seeps and organic falls have looked at macrofaunal taxa, but there has yet to be a systematic comparison of the community-level attributes of sediment macrobenthos in various reducing ecosystems. Here we review key similarities and differences in the sediment-dwelling assemblages of each system with the goals of (1) generating a predictive framework for the exploration and study of newly identified reducing habitats, and (2) identifying taxa and communities that overlap across ecosystems. We show that deep-sea seep, vent and organic-fall sediments are highly heterogeneous. They sustain different geochemical and microbial processes that are reflected in a complex mosaic of habitats inhabited by a mixture of specialist (heterotrophic and symbiont-associated) and background fauna. Community-level comparisons reveal that vent, seep and organic-fall macrofauna are very distinct in terms of composition at the family level, although they share many dominant taxa among these highly sulphidic habitats. Stress gradients are good predictors of macrofaunal diversity at some sites, but habitat heterogeneity and facilitation often modify community structure. The biogeochemical differences across ecosystems and within habitats result in wide differences in organic utilization (i.e., food sources) and in the prevalence of chemosynthesis-derived nutrition. In the Pacific, vents, seeps and organic-falls exhibit distinct macrofaunal assemblages at broad-scales contributing to ß diversity. This has important implications for the conservation of reducing ecosystems, which face growing threats from human activities

Holocene sea ice variability driven by wind and polynya efficiency in the Ross Sea

The causes of the recent increase in Antarctic sea ice extent, characterised by large regional contrasts and decadal variations, remain unclear. In the Ross Sea, where such a sea ice increase is reported, 50% of the sea ice is produced within wind-sustained latent-heat polynyas. Combining information from marine diatom records and sea salt sodium and water isotope ice core records, we here document contrasting patterns in sea ice variations between coastal and open sea areas in Western Ross Sea over the current interglacial period. Since about 3600 years before present, an increase in the efficiency of regional latent-heat polynyas resulted in more coastal sea ice, while sea ice extent decreased overall. These past changes coincide with remarkable optima or minima in the abundances of penguins, silverfish and seal remains, confirming the high sensitivity of marine ecosystems to environmental and especially coastal sea ice conditions

Expanded oxygen minimum zones during the late Paleocene-early Eocene:Hints from multiproxy comparison and ocean modeling

Anthropogenic warming could well drive depletion of oceanic oxygen in the future. Important insight into the relationship between de-oxygenation and warming can be gleaned from the geological record, but evidence is limited because few ocean oxygenation records are available for past greenhouse climate conditions. We use I/Ca in benthic foraminifera to reconstruct late Paleocene through early Eocene bottom and pore-water redox conditions in the South Atlantic and Southern Indian Oceans, and compare our results with those derived from Mn speciation and the Ce anomaly in fish teeth. We conclude that waters with lower oxygen concentrations were widespread at intermediate depths (1.5-2 km), whereas bottom waters were more oxygenated at the deepest site, in the Southeast Atlantic Ocean (>3 km). Epifaunal benthic foraminiferal I/Ca values were higher in the late Paleocene, especially at low oxygen sites, than at well-oxygenated modern sites, indicate higher seawater total iodine concentrations in the late Paleocene than today. The proxy-based bottom water oxygenation pattern agrees with the site-to-site O2 gradient as simulated in a comprehensive climate model (CCSM3), but the simulated absolute dissolved O2 values are low (<~35 µmol/kg), while higher O2 values (~60-100 µmol/kg) were obtained in an Earth system model (cGENIE). Multi-proxy data together with improvements in boundary conditions and model parameterization are necessary if the details of past oceanographic oxygenation are to be resolved

The ecology of living (stained) deep-sea benthic foraminifera from the Sulu Sea

The distribution of living (rose bengal stained) deep-sea benthic foraminifera was determined in the upper 20 cm of sediments of eight Soutar box cores taken from two depth transects (510-4515 m) in the thermospheric (> 10°C) Sulu Sea. Despite the uniformity of bottom water temperatures, salinities, and dissolved oxygen levels below 1000 m, significant faunal differences exist at different depths in the low-oxygen (∼1.25 mL/L below 1000 m) basin. The shallowest site (510 m) is dominated (> 10% of the calcareous fauna) by Cibicidoides, Uvigerina, (> 150 µm) and Bolivina (> 63 µm), while Siphonina is codominant with Cibicidoides and Uvigerina in the 1005-m core. The 2000-m cores are dominated by Cibicidoides, Gyroidinoides, and Oridorsalis, while Cibicidoides bradyi and Oridorsalis umbonatus dominate the 3000- and 4000-m cores. Infaunal assemblages of Valvulineria mexicana are found in the sediments of the 4515-m core. Relatively low bottom water oxygen values do not necessarily yield "typical low-oxygen taxa" such as Bolivina, Uvigerina, Chilostomella, Bulimina, and Globobulimina. Changes in the abundances of these taxa in fossil assemblages have been used as indicators of changes in ancient bottom water oxygen levels but may instead reflect organic carbon contents of the sediments. An examination of the vertical distributions of foraminiferal assemblages from the > 63-µm and > 150-µm fractions reveals that taxa have microhabitat preferences similar to those observed in other regions. Taxa found in the upper 0- to 1-cm interval (epifaunal) include Cibicidoides wuellerstorfi and Hoeglundina elegans, while taxa such as Chilostomella and Globobulimina reach maximum abundances in subsurface sediments and have infaunal microhabitat preferences. Cibicidoides bradyi and O. umbonatus live in sediment depths from 0- to 4-cm and have transitional preferences with both epifaunal and infaunal occurrences. Intrageneric differences in test morphologies, including pore distribution, rounded peripheries, and variable spire height, are observed in Cibicidoides and Gyroidinoides and are suggested to be related to microhabitat preferences. Vertical distributions of a number of taxa found in both the 63- to 150-µm and > 150-µm fractions are similar, suggesting that juveniles and adults live under similar microhabitat conditions. Ontogenetic changes in microhabitat preferences of most species are not observed in this study and therefore would not be expected to account for isotopic vital effects reported for some taxa in previous studies

Epifaunal Foraminifera in an Infaunal World: Insights Into the Influence of Heterogeneity on the Benthic Ecology of Oxygen-Poor, Deep-Sea Habitats

A reduction in dissolved oxygen availability in marine habitats is among the predicted consequences of increasing global temperatures. An understanding of past oxygenation is critical for predictions of future changes in the extent and distribution of oxygen minimum zones (OMZs). Benthic foraminifera have been used to assess changes in paleo-oxygenation, and according to prevailing thought, oxygen-poor marine benthic habitats are dominated by sediment-dwelling infaunal foraminifera, while more oxygenated environments are populated with more epifaunal taxa. However, in this study we found elevated densities of epifaunal taxa in oxygen-poor habitats. A series of 16 multicores were taken on depth transects (360–3000 m) across an OMZ in the Southern California Bight to investigate the ecology of living (rose bengal stained) benthic foraminifera. Dissolved oxygen concentrations in bottom water at sampling sites varied from 21 to 162 μmol/l. Sampling focused on bathymetric highs in an effort to collect seafloor surface materials with coarse sediments in areas not typically targeted for sampling. Mean grain size varied from about 131 (gravelly sand) to about 830 μm (coarse sand with fine gravel). Vertical distribution patterns (0–2 cm) were consistent with those of conspecifics reported elsewhere, and reconfirm that Cibicidoides wuellerstorfi and Hanzawaia nipponica have a living preference at or near the sediment-water interface. As expected, assemblages were dominated by infaunal taxa, such as Uvigerina and Bolivina, traditionally associated with the supersaturated, unconsolidated mud, characteristic of OMZ habitats, suggesting that these taxa are not sensitive to substrate type. However, despite dysoxic conditions (21–28 μmol/l), epifaunal taxa comprised as much as 36% of the stained population at the five sites with the coarsest mean grain size, while other measured environmental parameters remained relatively constant. We suggest that these epifaunal taxa, including C. wuellerstorfi, prefer habitats with coarse grains that allow them to remain at or above the sediment-water interface. These results suggest that seafloor habitat heterogeneity contributes to the distribution of benthic foraminifera, including in low-oxygen environments. We submit that paleo-oxygenation methods that use epifaunal indicator taxa need to reconsider the dissolved oxygen requirements of epifaunal taxa