OS11A-1095
Impact of Ridge Induced Latent Heat Advection on Sea Ice Global Heat Budget.
The effects of permeability on ice keel induced latent heat fluxes are examined using pressure ridge density statistics computed from SAR images and a prognostic simulation of forced brine advection through the bottom ice layer. Under pressure gradients generated in the wake of an ice keel sea water is pushed into and brine pumped out of the bottom ice layer. This in turn causes a new thermodynamic equilibrium to be reached. At spring when the ice permeability increases, brine export combined with sea water import translates into an advective heat flow that is balanced by the latent heat absorbed by volume melting of brine channel walls. Sea ice within the sheltered areas behind keels is modelled as an anisotropic heteregeneous mushy layer. The non-linear equation system within each cell is implemented on a finite volume grid and include volume melt of the brine channels from which porosity, water density, temperature and salinity are computed. Outputs from these simulations are then combined with ridge distribution statistics to evaluate the global impact of latent heat absorbed due to volume melting in the wake of ridges. As anticipated, results are highly dependent on permeability, nevertheless, they show that pressure ridge induced melting within the ice is a significant component of the heat budget when compared with melting at the ice water interface. This work underlines needs for further researches to improve our understanding of ice permeability changes during the melt season, it also calls for better tools to extract pressure ridge characteristics from satellite images.
OS11A-1096
Variability of Sea Ice Cover and Oceanographic Properties of the Canadian Arctic Archipelago.
Year-long moorings have been in place since August 1989 in Lancaster Sound to measure pack ice properties and oceanographic transports of the Arctic Surface Waters passing through the Canadian Arctic Archipelago (CAA). In addition, ice charts provide a thirty year time series on the inter-annual variability of mobile and land-fast pack ice conditions. The mooring time series data shows large inter-annual variability, but generally has a mayor transport peak in the summer and seasonal low in the late fall, early winter. Regression analysis with the Arctic Ocean wind field has shown that the highest correlation between the transports in Lancaster Sound is with the winds at grid location along Banks Island in the Canadian Beaufort Sea some 1000km from the mooring site. Local winds thus do not cause the variability in transports; instead the far-field winds do. The north-south winds over the shelf at the western entrance to the NW Passage set up the along pressure gradient in Lancaster Sound which in turn cause the variability seen in the observed transports. In contrast, local atmospheric conditions determine the mobile and land-fast sea ice cover variability in Lancaster Sound. Expected atmospheric changes within the CAA due to global warming will increase the length of the mobile ice season, increase the oceanographic transport variability and thereby changing physical environments controlling the biological marine ecosystem of the CAA from an ice-algae driven benthic to a phytoplankton driven pelagic community.
OS11A-1097
Effects of Increased UV and Sea Ice Retreat on Antarctic Marine Larvae
Increased UV radiation caused by a decrease in the levels of stratospheric ozone has the potential to harm marine organisms. The sharpest decrease in ozone can be found over the Antarctic continent during the austral spring. Invertebrates may be particularly susceptible to the effects of increased UV-R because most have a planktonic stage in which their embryos and larvae live in surface waters. Marine invertebrates in the Antarctic are likely to be affected to a greater extent than those in tropical and temperate biomes as there is not only a greater amount of UV-R coming through the atmosphere in these latitudes, but the larval stages are in the water column for a greater period, have slower metabolism, and a stenothermal physiology. These factors have the potential to affect recruitment of new individuals into marine populations. One of the major forms of damage is the creation of cyclobutane pyrimidine dimers (CPD) in DNA. Previous work has shown that photolyase, a protein that repairs UV-R induced CPDs on DNA, is present in echinoderm larvae, and increases the repair rates of UV-R damaged DNA. During the austral spring of 2007 laboratory and field experiments were carried out on Sterechinus. neumayeri at Cape Evans on Ross Island, Antarctica, and at the ice edge north of Cape Royds. The effects of depth, and consequently dose of UV-R on expression of photolyase was determined. We established that photolyase can be induced by increased UV-R in S. neumayeri, and consequently is dependent on depth of the water column. There also appears to be an upper limit, where increases in UV-R do not induce further photolyase expression. With predictions that the annual ozone hole will be present for at least another 50 years and the possible retreat of sea ice, ambient levels of UV-R in the marine environment of Antarctica will increase. The results of this research suggest that S. neumayeri can compensate for increased DNA damage to UV-R at relatively low levels. But if the levels increase to those found under thin sea ice or open water, the rate of damage might be greater than the rate of repair.
OS11A-1098
Enhanced biological activity in the western and central equatorial Pacific over the past decade
Recent observational studies indicate strengthened trade winds and intensified upwelling in the tropical Pacific since the late 1990s, with obvious implications for the equatorial Pacific biogeochemistry. A coupled OGCM-biogeochemical model is used to simulate the past several decades to place the last decade in the context of longer term variability of the physical-biogeochemical interactions. Modeling results indicate that there are systematic changes in mean biogeochemical conditions in the equatorial Pacific over the past decade. The strengthened winds and intensified upwelling during 1998-2007 have resulted in enhanced biological activity in the western and central equatorial Pacific. Integrated primary productivity has increased by 10%-16%. The biggest increase in new production (~15%) is in the central equatorial Pacific whereas the biggest increase in regenerated production (~20%) is shown in the western equatorial Pacific. Detailed analyses of the associated biogeochemical fields and possible implications for the carbon source/sink variability at regional scale will be discussed.
OS11A-1099
Spatial Variation of Surface fCO2 in the Western North Pacific and the East China Sea
We examined the spatial variation of surface fCO2 and its major controlling factors in the western North Pacific and the East China Sea based on surface fCO2, temperature and salinity continuously measured aboard R/V Onnuri in late summer 2006, 2007 and spring 2008. The western North Pacific and the East China Sea were distinguished in fCO2 distribution as well as characteristics of temperature and salinity. Diurnal variations of fCO2 corresponding to the diurnal variations of sea surface temperature (SST) observed in the western North Pacific indicated that SST was a major factor controlling the surface fCO2 distribution. On the contrary, fCO2 distribution in the East China Sea was controlled by many factors such as salinity, primary production and vertical mixing. The western North Pacific acted as a weak CO2 source while the East China Sea acted as a CO2 sink in both summer and spring.
OS11A-1100
The Role of Intra-Island Temperature Variability at Palmyra Atoll in Mass Coral Bleaching Events
Mass coral bleaching events have been reported in Palmyra Atoll during severe El Niños in the last 30 years, and are thought to be increasing both in frequency and magnitude. During these events, bleaching is highly localized, with some parts of the reef showing a much greater effect than others. NOAA's Coral Reef Watch monitors thermal stress on corals by calculating degree heating weeks (DHW) from satellite sea surface temperature in a 50 km pixel around each reef group or atoll of interest. While this technique allows some predictive capacity, especially for mass bleaching events, it does not consider the effects of reef geometry on bleaching susceptibility at different reef groups (Hoeke et al., 2006). Furthermore, because of its large scale, it cannot differentiate between open ocean, backreef, or lagoon temperatures. This project compiles high resolution temperature time series recorded in situ at a number of locations on the reef at Palmyra from 2002-2008, with surprising results. At any one given time, corals at different locations around the atoll may be experiencing temperature stresses that are significantly different both between locations and from the satellite DHW product. Shallow reef flats appear to be a source of heated water that, if advected elsewhere on the reef, may stress corals in normally cooler locations. A more thorough understanding of these mechanisms could improve our predictive capability as to which areas of the reef are at greatest risk if mass bleaching events continue to increase in severity and frequency.
OS11A-1101
Understanding Growth Limiting Nutrients Through Stoichiometric Approaches Around Dokdo in the East (Japan) Sea
In order to understand the limiting inorganic nutrients for phytoplankton growth around Dokdo in the East (Japan) Sea of Korea, this study was conducted at 33 stations in the November 2004, March and December 2007, and March 2008. Based on the physical properties (temperature and salinity) of the study area, water mass structures were primarily determined by two major current systems. One is southwestward flowing along the east coast of Korea called North Korean Cold Water (NKCW), and the other is northward flowing East Korean Warm Current (EKWC), which was a branch of the Tsushima Current Water (TCW). The vertical distributions of nutrients concentration showed typical pattern, increasing with depth. However, the horizontal distributions (in the 0 m, 30 m, and 75 m depth) of nutrients were mainly affected by physical processes. Nutrients were higher in the region mainly affected by NKCW than in that by EKWC even though the front region where was formed with mixture of cold water (NKCW) and warm water (EKWC) was varied with season. The scatter diagrams constructed using stoichiometric N:P ratios, Si:P ratios, and Si:N ratios indicated that N (mean 70.2%) was mainly limiting nutrient for phytoplankton growth in the surface layer of this study area. But P (39.6%, Dec. 2007) and Si (17.1%, Nov. 2006) also played a significant role in some area according to season. While the traditional approach using N:P ratio suggested this study area was only N-limited environment for phytoplankton growth, stoichiometric approaches indicated not only N-limited but also P- limited or Si-limited environment. Therefore, these results suggested that multiple approaches should give better information to understand nutrients dynamics in complex aquatic environment.
OS11A-1102
Sediment Waves of Caspian Sea
An area of approximately 1000 km2 of sediment waves is identified at the continental slope in the western Derbent Basin, central Caspian Sea, in water depths of 100–700 m. The waves are migrating up a steep angle (3.4°) slope to the west-northwest. They are typically slope-parallel, 15–30 m in amplitude and 150-400m in wavelength. Based on swath bathymetry and seismic reflection profiles, the sediments can be divided into eight acoustic units, which are parasequences of the regional HST. These parasequenses are evidences of transgression-regression subcycles inside the HST in whole. A quantitative measurement of key morphobathymetric parameters (such as wavelength, height, asymmetry and wave-form indexes) was performed for the each unit on three high-resolution one-channel seismic polygons. These measurements are determined with respect to water depth or downslope distance from the shallowest wave. The "regressive" units have sinusoidal wave-formed reflectors, the weaker the deeper the unit is. Wave amplitudes are also decreasing downward, meanwhile the wavelength is increasing, so do the symmetry. This might be caused not only by different environments but by sediment pressure as well. The "transgressive" units have weak but continuous parallel reflectors displaying well-developed waveforms mimicking and smoothing those below. The original construction of the waves may have been by integrating turbidits and bottom currents activity. The Derbent Basin is a seismically active domain where frequent turbidites are caused by trigging. The high sediment supply from Caucasus, as well strong bottom currents and Caspian famous permanent sea-level changes, form very peculiar geologic/stratigraphic setting.
OS11A-1103
The Role of Fluid and Gas Discharge in Shaping Seafloor Morphology
Numerous sites of seafloor fluid and gas discharge have been identified along continental margins since their initial discovery almost 25 years ago. Techniques used to detect, characterize, and sample these sites include direct observation by HOVs and ROVs, and acoustic mapping using primarily multi-beam and side- scan sonar systems. The database is now large enough to make some generalizations about the morphological features believed to indicate or focus fluid and gas discharge onto the seafloor. Four distinct morphologic categories are recognized: (1) discrete topographic highs; (2) discrete topographic lows; (3) the faces of escarpments; and (4) widespread areas of rough-textured, acoustically reflective seafloor. Most visual observations of gas bubble venting are associated with topographic highs (constructional features such as mud volcanoes, authigenic carbonate mounds, and chimney-like structures), rather than topographic lows. Low molecular weight hydrocarbon gases (predominantly methane, but also minor amounts of higher alkanes) are typically contained in the venting gases. Chemosynthetic biological communities (CBCs) and methane-derived authigenic carbonates are commonly found at gas venting sites, and because of this association, CBCs and authigenic carbonates are often used to infer seepage of methane-rich fluids onto the seafloor at sites where gas bubbling is not observed. The presence of pockmarks and pockmark fields (erosional depressions on the seafloor) is interpreted as indicating present or past venting of gas, which excavates these features. Gas bubble venting has been observed at selected pockmarks, and is commonly inferred to be the primary process responsible for creating and maintaining these features. However, a clear enunciation of how gas venting will excavate these depressions and documentation that specific pockmarks have formed as a consequence of gas venting is lacking. Fluid and/or gas discharge has been observed along steep topographic features. These include headwalls of slope failure scarps, bases of submarine escarpments, and flanks of submarine canyons. Inferences have been made that springs along submarine escarpments have played a role in forming this topography. However, a clear understanding of the role fluid discharge plays in generating steep topography or whether fluid discharge is simply located at these sites as a consequence of the topography has not yet been obtained. The widespread occurrence of rough-textured, acoustically-reflective seafloor associated with methane- derived carbonate slabs and crusts has been interpreted as indicating extensive methane-rich fluid or gas discharge and formation of authigenic carbonates on the seafloor. However, the occurrence of carbonate slabs and crusts on the seafloor can also result from the erosional exhumation of authigenic carbonate accumulations formed in the immediate subsurface via anaerobic oxidation of methane. Geochemical measurements and models favor formation of authigenic carbonate in the subsurface, not on the seafloor. Morphologic manifestations of gas and/or fluid discharge on the seafloor are the consequence of migrating reservoir fluids. How these fluids and gases interact with pre-existing seafloor topography and alter this topography is controlled by a variety of factors, including their chemical composition, rate of delivery, and rate of energy release by gas expansion. Thus, it is difficult to reliably infer process from morphology alone.
OS11A-1104
Forward modeling pore pressure evolution in the Ursa Basin, offshore Louisiana, Gulf of Mexico
We simulate deposition, pore pressure evolution, and flow in sediments of the Ursa Basin, Gulf of Mexico since 200 ka. These strata are composed of four successive depositional units: hemipelagic mudstone, the Blue Unit basin-floor fan, channel-levee deposition, and distal fan deposits. The Blue Unit, a laterally continuous, horizontal, sand-rich body overlies the hemipelagic mudstone. Channel-levee sediments buried the Blue Unit asymmetrically: its western margin (Site U1324) is 600 meters thick whereas its eastern margin (Site U1322) is only 230 meters thick. The base of the Blue Unit is dated at approximately 70ka and mudstones 20 meters above the Blue Unit are dated at 57 ky. Permeability is assumed to vary exponentially with porosity (log (k) = γφ +k0, where k is vertical permeability (m2), φ is porosity, and γ and k0 are fitting parameters). For clayey silts γ is 9.19 and k0 is -19.77, whereas for silty clays γ is 9.17 and k0 is -21.67. Compression is described as an exponential function of effective stress: e = -B/A +(eo+ B/A)×(σvhA/ln(10). For the Ursa mudstones, A = 0.338 and B = 0.152, eo = 0.894. We find that the rapid sedimentation at Site U1324 (~12 mm/yr) generates severe overpressures λ* =0.6 (λ* = P*/σvh). , where P* is overpressure and σvh is the hydrostatic effective stress), whereas a lower sedimentation rate at Site 1322 (3 mm/yr) generates modest overpressure (λ* = 0.3). The degree of lateral flow within the Blue Unit is striking: immediately upon burial by overlying mudstone, it acts to completely focus flow from the thick overburden section (Site U1324) toward the thin overburden section (Site U1322). This results in significant elevation of pore pressure at Site U1322, the location of lowest overpressure and provides a mechanism for the large submarine landslides and low regional gradient (2 degrees) offshore from the Mississippi delta.
OS11A-1105
Porosity vs. Permeability Behavior of Shallow Mudstones in the Ursa Basin, Deepwater Gulf of Mexico
At a given porosity, vertical permeabilities of silty clays from the Ursa Basin in the deepwater Gulf of Mexico, offshore Louisiana, USA, are on average two orders of magnitudes lower than vertical permeabilities of clayey silts from the same location. We estimate vertical permeabilities from uniaxial, constant rate of strain consolidation (CRSC) experiments on 30 whole-round cores that were collected from depths to 600 meters below seafloor at Integrated Ocean Drilling Program (IODP) Sites U1322 and U1324. Permeabilities range from 1.78 × 10-17 to 2.3 × 10-20 m2 for porosities 59.2% to 25.0% in silty clays and from 7.74 × 10-17 to 8.49 × 10-19 m2 for porosities 36.8% to 18.9% in clayey silts. We express the porosity-permeability behavior for each sediment specimen as a log-linear function: log (k) = γ · φ + k0, where k is vertical permeability in m2, φ is porosity, and γ and k0 are fitting parameters. For clayey silts γ is 9.19 and k0 is -19.77, whereas for silty clays γ is 9.17 and k0 is -21.67. In situ permeabilities (kinsitu) are obtained by extrapolating the individual porosity-permeability relationship back to the in situ porosity (φinsitu) of the whole-round core which is determined from water contents measured on either the specimen or trimmings. kinsitu ranges from 3.08 × 10-17 to 1.31 × 10-18 m2 for porosities 62% to 43% in silty clays and is 5.15 × 10-17 m2 for a porosity of 38% in clayey silts. We finally compare in situ vertical permeabilities estimated from CRSC experiments with permeabilities measured in flow-through permeability experiments using a constant rate of flow in a uniaxial, constant rate of strain consolidation test setup. Given an average in situ vertical permeability of 1.64 × 10-17 m2 and overpressures of 70% of the hydrostatic effective stress to a depth of 200 meters below seafloor at Site U1324 (Flemings et al., 2008), calculated modern upward flow rates are approximately 3.2 mm/yr.
OS11A-1106
Clay minerals in surface sediments of the South China Sea and surrounding fluvial drainage basins: Source and transportation
This study reports clay mineralogy in surface sediments collected from both the South China Sea and its surrounding major fluvial drainage basins to reveal sources of fine-grained detrital sediments and their transportation in the South China Sea. Total 225 surface samples throughout the South China Sea and 223 surface samples from surrounding fluvial drainage basins (e.g. Pearl River, Red River, Mekong River, southwestern Taiwan rivers and lakes, Luzon rivers, middle Vietnam rivers, and northern Borneo rivers) were analyzed for clay minerals by X-ray diffraction (XRD). Clay mineral assemblages derived from individual fluvial drainage basin present several characteristic end-members. Rivers and lakes in southwestern Taiwan include dominantly of illite and chlorite. Rivers in Luzon contain a huge amount of smectite. However, the Pearl River provides mainly kaolinite, with moderate illite and chlorite. Northern Borneo clays also consist mainly of illite and chlorite. The Red and Mekong Rivers present similar clay mineral assemblages with major illite, chlorite, and kaolinite. However, rivers in middle Vietnam present abundant kaolinite with northern rivers closer to the Red River. Despite of these characteristic end-member clay mineral assemblages in the surrounding fluvial drainage basins, the surface distribution in the South China Sea is highly unified with marginal clay mineral provinces closer to relative fluvial drainage basins. But in the abysmal South China Sea, clay minerals are highly mixed by both surface and bottom currents. The characteristic end-members combined with illite crystallinity and chemistry index in the surrounding fluvial drainage basins are sufficiently used to determine the sources of clay minerals in the South China Sea. Additionally, the clay mineral assemblages indicate various chemical weathering degrees in land surrounding the South China Sea. Strong physical erosion is evident in southwestern Taiwan and northern Borneo. Increased chemical weathering occurs in South China. However, the Indochina Peninsula and Luzon indicate a moderate chemical weathering processes.
OS11A-1107
Recovery of Magnesium from Seawaters and Development of Analytical Techniques for Eco-Friendly Materials Processing.
Nevertheless other resources such as fossil fuel, oils, mineral resources, drive continued interest in
developing fundamental techniques for recovering valuable metals like seawater origin. A process for
recovery of magnesium from brine and bittern have been described in achieving low-level detection limits as
well as reliability of analytical technique. The choice of analytical technique to meet the most stringent
analytical needs of our fields is ICP-OES and XRF for commercial purposes in high solid waters like bittern.
This study contains the results of a study of processes for seawater reverse osmosis with enhanced
precipitation yield such as NaCl, Mg(OH)2, and Br2. The original bittern composition supplied from Hanjoo
Co. Ltd. was pretreated for microbial matter and additional NaOH, NH4OH, or Na2CO3. Adding NaOH at pH
9.0 to pH 9.9 yield precipitation of Na2CO3.
http://kbsi.re.kr
OS11A-1108 TI: The deep-ocean environment, including the ocean floor and crust, represents one of the last scientific frontiers on earth. The surprising lack of information on the mineralogy, the geochemical processes, or the biota of the ocean floor is the result of the inability to simulate ocean-floor conditions and to study geochemical systems at these conditions. A proto-type high-pressure environmental chamber (HPEC) has been constructed for use on a transmission- mode X-ray diffractometer to study geochemical processes at the deep-ocean sediment cover and crust. The HPEC has a designed pressure range to 1000 bars and temperature range from -20 oC to 200 oC. In this chamber, a liquid (e.g., sea water) plus sample in suspension can be pressurized either by gas or liquid. A cell-pump system continuously agitates the liquid to keep particles in suspension, thereby allowing the examination of mineral phases, including clays minerals. A major feature of the HPEC is that the mineral component moves freely and can react with its environment while being illuminated by the X-ray beam. The cell-pump also allows applied gas, such as CH4 or CO2, or O2, to interact efficiently with the aqueous liquid so that the system may rapidly reach equilibrium. In addition, mixing these gases with inert gases, e.g. He or Ar, allows control of the fugacity of these gas components. The design components and how data are manipulated to remove X-ray dispersion effects caused by the liquid will be discussed, along with examples showing the effects of temperature, pressure, and salt content on smectite clay.
OS11A-1109
Characterizing the Discharge Features of Glacial Lake Agassiz during the Post-Marquette Period Using Marine Seismic-Reflection Methods
Glacial Lake Agassiz was the largest of the North American glacial margin lakes. Over its 4,000 year existence, Lake Agassiz varied substantially in aerial extent and volume. This variability was a function of the fluctuating retreat pattern of the Laurentide Ice Sheet's southwestern margin, differential isostatic rebound of the North American crust, the topography of the land exposed by the retreating ice, and erosion of the various outlet channels draining the lake. These factors combined to form a history of Lake Agassiz punctuated by sudden and sometimes catastrophic rerouting of its drainage from one outlet channel to another. The amount and routing of Lake Agassiz discharge has become controversial. However, extensive onshore observations of Glacial Lake Agassiz discharge features have firmly established that northwestern Lake Superior was a major drainage route following the retreat of the Marquette glacial advance ca. 9,500 years 14C BP. We describe a high-resolution single channel seismic reflection dataset collected with a small airgun that we acquired to test our hypothesis that this drainage event (corresponding to the Nipigon Phase of Lake Agassiz) left diagnostic stratigraphic and geomorphic signatures beneath Lake Superior. The unique bathymetry of northwestern Lake Superior, where water depth plunges off Nipigon and Black Bays, makes this location ideal for the identification and characterization of the Post-Marquette depositional features. The steep and sudden drop-off from the shallow water bays into the deep offshore waters of the lake would have caused the high-velocity floods to slow and drop much of the sediment they were carrying. Our results confirm the existence of these sediment packages, which are now buried below a thin blanket of Holocene sediment. They form wedges of sediment that are thickest (some over 70 m thick) in the deep water area adjacent to the flood outlet. The apron of sediment thins lakeward and shore-parallel away from the outlet. The seismic character of the basal units of the apron, proximal to the outlet, is chaotic and only very weakly stratified suggesting that these deposits represent coarse sediment laid down during the initial stages of the flood when flow was presumably at its peak. These sediments are overlain and draped by a weakly stratified package that is more widely developed (extending lakeward beyond the bounds of our survey). We interpret this unit, which becomes more stratified and thinner lakeward, to represent the fine grained sediment associated with the latter stages of the flood when flow had eased.
OS11A-1110
Presentation, Calibration and Validation of the Low-order, DCESS Earth System Model
A new, low-order Earth system model is described, calibrated and tested against Earth system data. The model features modules for the atmosphere, ocean, ocean sediment, land biosphere and lithosphere and has been designed to simulate global change on time scales of years to millions of years. The atmosphere module considers radiation balance, meridional transport of heat and water vapor between low-mid latitude and high latitude zones, heat and gas exchange with the ocean and sea ice and snow cover. Gases considered are carbon dioxide and methane for all three carbon isotopes, nitrous oxide and oxygen. The ocean module has 100 m vertical resolution, carbonate chemistry and prescribed circulation and mixing. Ocean biogeochemical tracers are phosphate, dissolved oxygen, dissolved inorganic carbon for all three carbon isotopes and alkalinity. Biogenic production of particulate organic matter in the ocean surface layer depends on phosphate availability but with lower efficiency in the high latitude zone, as determined by model fit to ocean data. The calcite to organic carbon rain ratio depends on surface layer temperature. The semi-analytical, ocean sediment module considers calcium carbonate dissolution and oxic and anoxic organic matter remineralisation. The sediment is composed of calcite, non-calcite mineral and reactive organic matter. Sediment porosity profiles are related to sediment composition and a bioturbated layer of 0.1 m thickness is assumed. A sediment segment is ascribed to each ocean layer and segment area stems from observed ocean depth distributions. Sediment burial is calculated from sedimentation velocities at the base of the bioturbated layer. Bioturbation rates and oxic and anoxic remineralisation rates depend on organic carbon rain rates and dissolved oxygen concentrations. The land biosphere module considers leaves, wood, litter and soil. Net primary production depends on atmospheric carbon dioxide concentration and remineralization rates in the litter and soil are related to mean atmospheric temperatures. Methane production is a small fraction of the soil remineralization. The lithosphere module considers outgassing, weathering of carbonate and silicate rocks and weathering of rocks containing old organic carbon and phosphorus. Weathering rates are related to mean atmospheric temperatures. A pre-industrial, steady state calibration to Earth system data is carried out. Ocean observations of temperature, carbon 14, phosphate, dissolved oxygen, dissolved inorganic carbon and alkalinity constrain air-sea exchange and ocean circulation, mixing and biogeochemical parameters. Observed calcite and organic carbon distributions and inventories in the ocean sediment help constrain sediment module parameters. Carbon isotopic data and carbonate vs silicate weathering fractions are used to estimate initial lithosphere outgassing and rock weathering rates. Model performance is tested by simulating atmospheric greenhouse gas increases, global warming and model tracer evolution for the period 1765 to 2000, as forced by prescribed anthropogenic greenhouse gas inputs and other anthropogenic and natural forcing. Long term, transient model behavior is studied with a set of 100,000 year simulations, forced by a slow, 5000 GtC input of CO2 to the atmosphere, and with a 1.5 million year simulation, forced by a doubling of lithosphere CO2 outgassing.
OS11A-1111
NOAA Surveys; Stabalizing Economy and Ecology on The U.S. Coast
NOAA TEACHER AT SEA: LISHA LANDER HYLTON ONBOARD NOAA SHIP: DELAWARE II JUNE 29TH –JULY 11TH, 2008 MISSION: The mission of my trip with NOAA was to provide me (a teacher of third grade students) an extraordinary opportunity to take part in genuine–world experiences being conducted by NOAA in order for me to achieve a clearer insight into our ocean planet and a superior perceptive of NOAA-related careers. With the knowledge that I obtained on-board THE DELAWAREII - I am now able to teach the lesson plans created on my field study to my students, giving them insight as to how much power they have on their lives and this world we live in. My students are able to play a part in maritime activities as we study together, valuing the work and expertise that is required to sustain oceanic and atmospheric research. The students' enthusiasm, inquisitiveness and yearning to learn is only heightened with the hands-on, motivational activities that I gained from my research with this NOAA team. As a Part of this NOAA team, on-board we conducted clam surveys at various stations along the northeastern coast of the United States. I learned that clams are a very important part of economy and ecology in this region. Surveying clams and other marine species was performed on my field study with NOAA for the purpose of conserving marine life. NOAA realizes the importance of the fishing industry and conducts fishery surveys in order to stabilize fishery industries without destroying the marine ecosystems completely. Clams play a very important part in marine fishery; therefore these surveys are helping to maintain stability in the economy and ecology of The United States. By comparing past and present fishery surveys, our team made conclusions regarding the stability of these marine populations. After dredging, collecting, sorting, counting, measuring and weighing (clams with shells and shucked clam meat only) – the data was obtained and recorded then entered into computers filed under the specific station number that was dredged. All data was then sent to a central database. The compiled data was compared to past surveys. If the meat weight, size, quantity or quality of clams collected has reduced in comparison to past surveys, this could be an indication that some factor is influencing the reduction. Possible influencing factor: ~Clams are being over-fished~ I created a Power point-presentation, (200 slides long) in order to teach my students how and why NOAA scientist conduct these fishery surveys.
OS11A-1112 [WITHDRAWN]
Shallow-water seismoacoustic noise generated by tropical storms Ernesto and Florence
Land-based seismic observations of double frequency (DF) mi- croseisms generated during tropical storms Ernesto and Florence are dominated by signals in the 0.15 - 0.5 Hz band. In contrast, data from sea floor hydrophones in shallow water (70 m depth, 130 km off the New Jersey coast) show dominant signals in the ocean gravity-wave frequency band, 0.02 - 0.18 Hz, and low amplitudes from 0.18 to 0.3 Hz, suggesting significant opposing wave components necessary for DF microseism generation were negligible at the site. Florence produced large waves over deep water while Ernesto only generated waves in coastal regions, yet both storms produced similar spectra. This suggests near-coastal shallow water as the dominant region for observed microseism generation.
OS11A-1113
Regional Comparisons from a Global Survey of Deep-Ocean Sound
A NOAA Pacific Marine Environmental Lab archive of continuous deep-ocean sound recordings from hydrophones deployed in the equatorial East Pacific (EEP), central Mid-Atlantic (CMA), northern Mid-Atlantic (NMA), Bering Sea (BS), Antarctic Peninsula (ANP), and Indian Ocean (IO) provides insight into the overall structure for the deep-water global sound field. The hydrophones are moored in the SOFAR channel, taking advantage of the efficient propagation characteristics that enable the instruments to effectively monitor large sections of the global oceans. Although not always concurrent, the deployment of the hydrophone arrays from 1996 to present allows for an up-to-date assessment of the global-scale distribution of ocean sound levels in discrete frequency bands. Comparisons of intra- and inter-annual time-averaged ambient-sound levels reveal strong latitudinal variations, where higher latitudes correspond with higher noise levels. Seismic and volcanic activity dominate the lower frequency bands (0-10 Hz) within all of the hydrophone arrays. Of interest is the periodic nature of broad-band ice noise observed in the ANP acoustic data, suggesting a climate link for these signals related to ice breakup during seasonal warming events (Matsumoto et al., 2008). In addition, the multi-species marine-mammal vocalizations observed in all of our hydrophone datasets dominate sound-energy levels at specific frequencies.
OS11A-1114
Scaling of Mixing Parameter in Homogeneous Sheared and Stratified Turbulence
The dependency of the overturn Froude number on the Reynolds number was investigated for the modeling of the mixing parameter in various scales. Large eddy simulations of homogeneous sheared and stratified turbulence were carried out under the condition of the energy equilibrium with various combinations of energy dissipation rate and stratification. The Reynolds numbers calculated from the overturn scale and the dissipation rate ranged from O (102) to O (104), which was larger than those of the conventional numerical simulations of homogeneous stratified turbulence. It was found that the Froude number based on the overturn scale can be scaled by the ratio of the maximum length scale (here domain size) and the Ozmidov scale rather than the gradient Richardson number. This indicates that not only the gradient Richardson number, but also the Reynolds number play important roles in the vertical mixing, and their effects are taken into account in the present scaling of the Froude number. The correlation coefficient of the density and the vertical velocity component seems to depend on the overturn Froude number without further classification by the Reynolds number, and was expressed as the function by the fitting. Finally, the flux Richardson number was expressed as the function only on the overturn Froude number, in other words, the combination of the energy dissipation rate, the stratification, and the maximum length scale.
OS11A-1115
Investigating Increases in Spectral Gamma Ray Signals Observed From Wireline Logging Through Correlation With Core Geochemical Analyses: Integrated Ocean Drilling Program (IODP) Expedition 310, Tahiti Sea Level
The last deglacial reef sequence in Tahiti consists of a series of successive reef terraces seaward of the living barrier reef. IODP Expedition 310 recovered core from 37 boreholes which shows that the reef terraces are composed of two major lithological units (i) a last deglacial carbonate sequence and (ii) an older Pleistocene unit. Each sequence comprises of a series of distinctive coral assemblages, with microbialites locally forming the major component of the reef. High levels of U in carbonates have previously been linked to diagenetic processes, subaerial exposure, higher levels of organic material and the presence of red algae. Spectral gamma ray logs collected during Expedition 310 show a significant interval of elevated gamma ray counts in Hole M0005D. This ~20 m thick interval is located in the Pleistocene succession a few metres below the boundary with the last deglacial sequence. Analysis of the individual elements contributing to the gamma counts show that U is the major contributor to the higher counts in the upper part of this interval. This interval comprises the coralgal- microbialite reef frameworks that dominate much of the reef terraces and there is no apparent link between U and lithology. Higher counts in the lower section result from raised Th and K concentrations and correlate with silt dominated lithology at these depths. We selected 104 core samples from the high-U intervals for standard geochemical analyses (XRF). Major element correlation diagrams including our new data and published data on Tahiti igneous rocks imply that igneous fragments may have been incorporated during carbonate precipitation. Detailed thin section analyses reveal small volcanic clasts within some carbonates supporting this interpretation. The geochemical analyses of the core (both discrete samples and continuous core) also indicate that an interval of increased Mg correlates with the increase in U observed from the logs. We infer from high CaO (48 to 52 wt.%) and moderate MgO (2 to 6 wt.%) observed in this interval the presence of dolomite, thus implying a potential diagenetic influence. Mass balance calculations using major element oxides demonstrate that this is compatible with the geochemical data. These preliminary findings from combining spectral gamma ray observations with analyses performed on core samples provide insight into the processes operating in the Tahiti reefal carbonates. Establishing the potential causes of U increases and identifying these elsewhere may provide a tool to identify other regions of the reef affected by similar processes.