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Monday, December 9, 2013

Constraints on hydrocarbon and organic acid abundances in hydrothermal fluids at the Von Damm vent field, Mid-Cayman Rise

Since the discovery of hydrothermal vents on the seafloor, organic compounds in vent fluids have drawn significant scientific interest because of the potential insight they may offer into the origin of life on Earth as well as the establishment of life elsewhere.  We collected samples from the Von Damm hydrothermal vent field at depths of about 2,350 meters on the Mid-Cayman Rise. These hydrogen-rich vent fluids that can reach temperatures up to 226°C provide an exciting opportunity to examine abiotic carbon transformations in a highly reducing system. Our results indicate multiple sources of carbon compounds in vent fluids at this site. Furthermore, the transformation of inorganic carbon to organic compounds via two distinct pathways in modern seafloor hydrothermal vents validates theoretical and experimental models of processes that occur in the crust and during hydrothermal circulation. This transformation is relevant to supporting life in vent ecosystems.

Speaker: Jill M. McDermott

Time: 10:50 a.m.

Location: 2000 Moscone West


Shear-wave Velocity Structure and Inter-Seismic Strain Accumulation in the Up-Dip Region of the Cascadia Subduction Zone: Similarities to Tohoku?

It’s difficult to study the up-dip region of subduction zone thrusts using land-based seismic and geodetic networks, yet documenting the region’s ability to store and release elastic strain is critical to understand the mechanics of great subduction earthquakes and tsunamis. To tackle this, we deployed 10 ocean bottom seismographs (OBS) on the continental slope offshore of Vancouver Island from 2010 to 2011 as part of the SeaJade experiment. One goal of the experiment is to measure the shear modulus of the sediments lying above the subducting plate.

The 2011 Tohoku earthquake produced extremely large slip in the shallowest portion of the subduction zone beneath a region of the fore-arc that is comprised of extremely low-velocity, unconsolidated sediments [Tsuru et al. JGR 2012]. The influence of the sediment material properties on the co-seismic slip distribution and tsunami generation can be considerable through both the effects on the dynamic wavefield during the rupture [Kozdon and Dunham, BSSA 2012] and potentially the build-up of strain during the inter-seismic period.

We calculated the effect of the material property contrast on the inter-seismic strain accumulation in the up-dip region of the subduction zone using a finite element model and found that the sediments can increase the amount of inter-seismic strain accumulated in the up-dip region by more than 100 percent relative to a homogenous elastic model.

Speaker: John A. Collins

Time: 11:50 a.m.

Location: 305 Moscone South

Tuesday, December 10, 2013

Punctuated events and long-term barrier evolution in a rising-sea-level world

Barrier coasts, both developed and undeveloped, face historically unprecedented rates of sea-level rise over the coming century. These sustained rates have not been seen since the last deglaciation. Understanding the future trajectory of barriers requires an integrated accounting of three key sediment transport pathways: alongshore transport gradients, on-offshore sediment transport across the wave-affected shoreface, and onshore sediment transport, generally by storm overwash.

 To incorporate the role of storms on coastal evolution with results from recent models, we analyzed 20-year hindcast wave data along the U.S. Gulf Coast and Atlantic Coast. Ensemble model results can then be used to understand a potential range of future barrier evolution for different sea-level rise scenarios. We find that pre-existing barrier geometries play a significant role in storm response and accordingly, coupling profiles alongshore allows us to investigate the role of alongshore variability on long-term barrier evolution.

Speaker: Andrew Ashton

Time: 8:15 a.m.

Location: 2003 Moscone West


Magnetotelluric Data, Stable Distributions and Stable Regression

The author has noted for many years that the residuals from robust or bounded influence estimates of the magnetotelluric response function are systematically long tailed compared to a Gaussian or Rayleigh distribution. Consequently, the standard statistical model of a Gaussian core contaminated by a fraction of outlying data is not really valid. This paper introduces a new statistical approach to magnetotelluric data that is based on stable regression, which directly accommodates the actual residual distribution without eliminating the most extreme ones.

 Further work remains to produce a robust stable regression algorithm that will eliminate real outliers such as lightning strikes or instrument problems without affecting the bulk stable population. Stable distributions are intimately associated with fractional derivative physical processes. Since the Maxwell equations and the constitutive relations pertaining to the earth do not contain any fractional derivatives, the pervasive occurrence of stable residuals for magnetotelluric response function estimates must have an origin in the ionospheric and magnetospheric sources.

Speaker: Alan D. Chave

Time: 9:15 a.m.

Location: 300 Moscone South


Triggering processes of earthquake bursts in Japan: evidence from statistical modeling

In our search for spatially and temporally isolated earthquake bursts across Japan using the Japan Meteorological Agency (JMA) catalog from 2000 to 2013, we identified 290 earthquake bursts. For each identified burst, we obtain a set of parameters, which include the ratio between total moment release and volume of the burst, tmax, duration, radius, planarity, and dip. Ninety of these bursts occurred within 2 km of another burst.

Our results suggest that periodic aseismic stressing is playing a significant role in triggering crustal earthquake bursts in Japan. The results also suggest correlation between volcanoes and Epidemic Type Aftershock Sequences (ETAS) parameters, because lower α and higher p are observed within 25 km from active volcanoes and no clear differences among background fraction or swarm-like or aftershock-like burst types are identified. Further analysis of relevant geodetic measurement or fluid imaging may help to additionally distinguish the driving force in each area.

Speaker: Xiaowei Chen

Time: 11:05 a.m.

Location: 307 Moscone South


Early Anthropogenic Transformation of the Danube-Black Sea System: From Records to Causes

When did humans change their terrestrial habitats in such a degree to affect the ocean? We present sedimentary, paleoenvironmental, and paleogenetic evidence to show that the Black Sea was affected by land use long before the Industrial Era.

 Although watershed hydroclimate was spatially and temporally variable over the last ~3,000 years, surface salinity dropped systematically in the Black Sea. Sediment loads delivered by the Danube River, the main tributary of the Black Sea, significantly increased as land use intensified in the past two millennia, which led to a rapid expansion of its delta. Lastly, proliferation of diatoms and dinoflagellates over the past five to six centuries, when intensive deforestation occurred in Eastern Europe, points to an anthropogenic pulse of river-borne nutrients that radically transformed the food web structure in the Black Sea.

We discuss potential avenues for fingerprinting historical land use type and intensity based on sedimentary proxies as well as novel strategies to disentangle climate from anthropogenic variables with potential application to other systems outside the Danube and Black Sea.

Speaker: Liviu Giosan

Time: 11:50 a.m.

Location: 3003 Moscone West


The influence of magma degassing on entrapment pressures recorded in olivine-hosted melt inclusions

The concentrations of H2O and CO2 in olivine-hosted melt inclusions provide estimates for the pressures at which they were entrapped, and represent an important source of information on the depths at which basaltic magmas crystallize. Results from recent dehydration experiments demonstrate that diffusive loss of H2O from melt inclusions, driven by degassing of the external magma, leads to significant decreases to pressure within the inclusion. This, in turn, lowers the solubility of CO2 in the included melt causing a vapor to exsolve and form a bubble. This process has the potential to significantly modify estimates of entrapment pressures derived from volatile concentrations in olivine hosted melt inclusions.

 I have developed a quantitative model that describes this process, allowing the influence of degassing on entrapment pressures to be rigorously evaluated. Modeling results demonstrate that degassing of H2O-rich magma produces significant drops in pressure so that entrapment pressures never exceed crustal values and always represent a minimum. Conversely, degassing of H2O-poor magma does not significantly perturb the H2O content of olivine-hosted melt inclusions. Therefore, these inclusions preserve reliable records of the pressures at which they were entrapped. These results are consistent with a global compilation of olivine-hosted melt inclusion entrapment pressures

Speaker: Glenn Gaetani

Time: 3:25 p.m.

Location: 308 Moscone South

Wednesday, December 11, 2013

Abrupt shifts in Horn of Africa hydroclimate and the influence of the Indian Ocean

The timing and abruptness with which Northeast Africa transitioned into and out of the Early Holocene African Humid Period is a subject of ongoing debate with direct consequences for our understanding of climate stability and paleoenvironments. Here we present a new proxy record of regional hydroclimate, based on the hydrogen isotopic composition of leaf waxes from a marine core in the Gulf of Aden that documents rapid, century-scale transitions into and out of the African Humid Period across the Horn of Africa. The Gulf of Aden record also documents large drying events during the last deglacial, synchronous with Heinrich Event 1 and the Younger Dryas.   

 Similar and generally synchronous abrupt transitions at other East African sites suggest that rapid shifts in hydroclimate are regionally coherent. In addition, the termination of the African Humid Period in East Africa is synchronous with the termination along the western Saharan margin. A probabilistic analysis of the abruptness of the transitions in East Africa suggests that they likely occurred within centuries, underscoring the sensitivity of northeast African hydroclimate to external forcings. We speculate that the non-linear behavior of hydroclimate in the Horn of Africa is related to convection thresholds in the western Indian Ocean, and test this hypothesis with preliminary sea surface temperature (SST) proxy data.

Speaker: Jessica Tierney

Time: 8:15 a.m.

Location: 2005 Moscone West


Imaging sediments in the deep, rough terrain at the Mid-Atlantic Ridge using AUV Sentry’s CHIRP sub-bottom profiler

 

AUV Sentry obtained sub-bottom profiles that provide a new and exciting look at the detailed morphology of the sediments covering the deep seafloor. Equipped with an  Edgetech 2200M sub-bottom profiler, which uses a CHIRP signal (a broadband, swept waveform) in the 4 – 24 kHz range, we obtained sub-bottom profiles on 11 Sentry dives during R/V Knorr Cruise 210-05 in May-June 2013.

 Our study region was centered at 16.5N on the flanks of the Mid-Atlantic Ridge (MAR). Sentry flew at ~60 m above the seafloor traversing terrain that included features over 1 km in relief. 

 The resulting images are excellent quality. Sedimentary layers were identified above the acoustic basement, with thicknesses ranging from tens of centimeters to 4-5 m. Preliminary interpretation shows no evidence for reflections beneath the sediment – basement interface. We have used the high-resolution sub-bottom profiles to estimate sedimentation rate at this section of the MAR. And in combination with the other high-resolution products from Sentry, we have been able to argue that some of the long-lived faults observed in the region are still active.

Speaker: Dana Yoerger

Time: 8:35 a.m.

Location: 3009 Moscone West


Sustainable Software Decisions for Long-term Projects

Adopting new, emerging technologies can be difficult for established projects that are positioned to exist for years to come. In some cases the challenge lies in the pre-existing software architecture. In others, the challenge lies in the fluctuation of resources like people, time, and funding.

The Biological and Chemical Oceanography Data Management Office (BCO-DMO) was created in late 2006 by combining the data management offices for the U.S. GLOBEC and U.S. JGOFS programs to publish data for researchers funded by the National Science Foundation (NSF). Since its inception, BCO-DMO has been supporting access and discovery of these data through web-accessible software systems and has worked through many of the challenges of incorporating new technologies into its software systems. From migrating human readable, flat file metadata storage into a relational database, and now, into a content management system (Drupal) that incorporates controlled vocabularies, new technologies can radically affected the existing software architecture. However, BCO-DMO has been able to adapt its existing software architecture to adopt new technologies through science-driven use cases, effective resource management, and loosely coupled software components.

One of the latest efforts at BCO-DMO revolves around applying metadata semantics for publishing linked data in support of data discovery. This effort primarily affects the metadata web interface software at http://bco-dmo.org and the geospatial interface software at http://mapservice.bco-dmo.org/. With guidance from science-driven use cases and consideration of our resources, implementation decisions are made using a strategy to loosely couple the existing software systems to the new technologies. The results of this process led to the use of Representational State Transfer (REST) web services and a combination of contributed and custom Drupal modules for publishing BCO-DMO’s content using the Resource Description Framework (RDF) via an instance of the Virtuoso Open-Source triplestore.

Speaker: Adam Shepherd

Time: 8:40 a.m.

Location: 2020 Moscone West


Air-Sea Coupling and South Pacific and Southern Ocean Surface Moorings: Results from 10 Years of Observations and Future Plans

High quality surface meteorological and air-sea flux data collected from long-term surface moorings provide a valuable resource. They can be used for validating models and for describing the variability and trends in the surface meteorology and air-sea coupling. Results from a surface mooring maintained at a site off northern Chile since October 2000 are presented. These results point to the potential for future, planned deployments of surface moorings in the Southern Ocean. The NSF Ocean Observatories Initiative (OOI) plans to deploy and maintain moored arrays at 55°S, 90°W in the South Pacific and at 42°S, 42°W in the South Atlantic. The surface moorings at those sites will have a core set of sensors whose data will be made freely available. They will also have power and bandwidth available for investigators to add additional sensors.

Speaker: Robert A. Weller

Time: 11:35 a.m.

Location: 3006 Moscone West


Putting Hurricane Sandy in Historical and Geological Context

Hurricane Sandy caused $71 billion in property damage and 285 lives were lost. But the category 1 storm was small in relation to hurricanes that have hit the East Coast since the 18th century, according to Woods Hole Oceanographic Institution Geologist Jeff Donnelly. He found that the coastline by New York City and New Jersey was struck by category 3 hurricanes in 1788 and 1821. Given the population increase and development on the coast over the past two centuries, if storms like these were to occur today, they would likely result in significantly more damage and loss of life than Hurricane Sandy.

Donnelly tracks hurricane landfalls through overwash deposits and hydrodynamic modeling. He has gathered information on hurricanes that impacted the Northeast in 1788, 1821, 1893, 1938, 1944, 1954, 1960, 1976, 1985, and 1991.

Speaker: Jeffrey P. Donnelly

Time: 1:40 p.m.

Location: 3009 Moscone West


Contrasting ice sheet response to early and late summer rapid supraglacial lake drainage events on the Greenland Ice Sheet

Using a network of 20 GPS stations installed in 2011, and supplemented with a smaller network operating back to 2006, we observe ice surface motion during a series of lake draining hydro-fracture events on the Greenland Ice Sheet. The data are used to investigate the location and propagation geometry of the fracture opening, and the acceleration of ice in response to the rapid input of surface meltwater to the bed.

Observations at the same location show varying surface motion following early versus late summer rapid lake drainage events from multiple years. The results indicate that the ice-sheet response is modulated, at least in part, by the seasonal evolution of the subglacial hydrological system.

Speaker: Laura Stevens

Time: 1:55 p.m.

Location: 3007 Moscone West


Improved Discovery and Re-Use of Oceanographic Data through a Data Management Center

Effective use and reuse of ecological data are not only contingent upon those data being well-organized and documented, but also upon data being easily discoverable and accessible by others. As funding agency and publisher policies begin placing more emphasis on, or even requiring, sharing of data, some researchers may feel overwhelmed in determining how best to manage and share their data. The Biological and Chemical Oceanography Data Management Office (BCO-DMO) was created in 2006 to work with investigators to manage data from research funded by the Division of Ocean Sciences (OCE) Biological and Chemical Oceanography Sections and the Division of Polar Programs (PLR) Antarctic Organisms and Ecosystems Program of the US National Science Foundation (NSF).

Researchers contributing data to BCO-DMO benefit from the data management and sharing resources. Researchers looking for data can use BCO-DMO’s system to find and use data of interest. This role of the data management center in facilitating discovery and reuse is one that can be extended to other research disciplines for the benefit of the science community.

Speaker: Shannon Rauch

Time: 2:10 p.m.

Location: 300 Moscone South


Left Behind: Effects of marine reworking and sea-level rise on deltas of the 21st century

The 21st century will represent a time of punctuated change for the morphology of the world’s deltas as they face the doubled-edged impacts of sediment reduction during reservoir infilling and submergence by rising sea levels. This research focuses on the controls on the evolution of deltas strongly affected by marine processes, namely wind waves, with a particular emphasis on reworking. Our objective is to apply process-based quantitative means to advance our observational knowledge of how changes in sediment supply and accommodation growth through sea-level rise manifest through delta reworking and the delta cycle.

Building upon previous research highlighting how the angle of approaching waves can leave a fingerprint on a delta's shape, we investigate how the coastal conditions prior to sediment cessation can be used to predict the morphologic shape of the ensuing reworked shore along and adjacent to the former delta, including the potential for forming spits and other features indicative of lobe abandonment.

As delta plains flood, marine processes will likely sculpt protective barriers whose evolution and responses to sea-level rise are strongly affected by the process of overwash. Coupling the alongshore and cross-shore dimensions allows a more detailed picture of the fate of many deltas over the next century and beyond.

Speaker: Andrew Ashton

Time: 2:55 p.m.

Location: 2005 Moscone West


Maintenance of large deltas through channelization

River deltas are in danger of drowning due to an accelerated sea level rise, lack of new fluvial sediments and lack of mobility under their development by humans. While a new paradigm for delta restoration is currently taking shape in the Mississippi delta, we propose an alternative for delta maintenance primarily envisioned for wave-influenced deltas based on experiences from the Danube delta.

Over the past half century, while the total sediment load of the Danube dramatically decreased due to dam construction on tributaries and its mainstem, a grand experiment inadvertently ran in the Danube delta: the construction of a dense network of canals, which almost tripled the water discharge toward the interior of the delta plain.

We use core-based and chart-based sedimentation rates and patterns to explore the delta transition from the natural to an anthropogenic regime, to understand the effects of far-field damming and near-field channelization, and to construct a conceptual model for delta development as a functional sediment partition between the delta plain and the delta coastal fringe.

We suggest that increased channelization that mimics and enhances natural processes may provide a simple solution for keeping delta plains above sea level and that abandonment of wave-dominated lobes may be the most long term efficient solution for protecting the internal fluvial regions of deltas and providing new coastal growth downcoast.

Speaker: Liviu Giosan

Time: 3:25 p.m.

Location: 2005 Moscone West

Thursday, December 12, 2013

The influence of surface energy on the transport of hydrothermal vent products and the connections among vent populations

Atmospheric forcing, which is known to have strong influence on surface ocean dynamics and production, is typically not considered in studies of the deep sea. Our observations and models demonstrate an unexpected influence of surface-generated mesoscale eddies originating off the coast of Central America in the transport of hydrothermal vent efflux and of vent larvae away from the northern East Pacific Rise and potentially between isolated vent fields. These eddies are formed seasonally and are sensitive to phenomena such as El Niño, they have the potential to introduce seasonal to interannual atmospheric variations into the deep sea. The evidence from the northern East Pacific Rise suggests that surface processes may influence transport of hydrothermal vent products more widely. We tested this hypothesis by comparing patterns of connectivity among populations of hydrothermal vent organisms with patterns of ocean surface kinetic energy.

Speaker: Diane Adams

Time: 1:45 p.m.

Location: 3009 Moscone West


Past Asian Monsoon circulation from multiple tree-ring proxies and models

The Asian monsoon can be characterized in terms of precipitation variability as well as features of regional atmospheric circulation across a range of spatial and temporal scales. While multicentury time series of tree-ring widths at hundreds of sites across Asia provide estimates of past rainfall, the oxygen isotope ratios of annual rings at some of these sites can reveal broader regional atmosphere-ocean dynamics. Here we present a replicated, multicentury stable isotope series from Vietnam that integrates the influence of monsoon circulation on water isotopes. Stronger (weaker) monsoon flow over Indochina is associated with lower (higher) oxygen isotope values in our long-lived tropical conifers. Ring width and isotopes show particular coherence at multidecadal time scales, and together allow past precipitation amount and circulation strength to be disentangled. Combining multiple tree-ring proxies with simulations from isotope-enabled and paleoclimate general circulation models allows us to independently assess the mechanisms responsible for proxy formation and to evaluate how monsoon rainfall is influenced by ocean-atmosphere interactions at timescales from interannual to multidecadal.

Speaker: Kevin J. Anchukaitis

Time: 1:40 p.m.

Location: 2010 Moscone West

Friday, December 13, 2013

Using Controlled Vocabularies and Semantics to Improve Ocean Data Discovery

The Biological and Chemical Oceanography Data Management Office (BCO-DMO) was created in late 2006, by combining the formerly independent data management offices for the U.S. GLOBal Ocean ECosystems Dynamics (GLOBEC) and U.S. Joint Global Ocean flux Study (JGOFS) programs. BCO-DMO staff members work with investigators to publish data from research projects funded by the NSF Geosciences Directorate (GEO) Division of Ocean Sciences (OCE) Biological and Chemical Oceanography Sections and Polar Programs (PLR) Antarctic Sciences Organisms & Ecosystems Program (ANT). Since 2006, researchers have been contributing new data to the BCO-DMO data system.

We are exploring use of technologies to improve the accuracy of the BCO-DMO data collection and to facilitate exchange of information with complementary ocean data repositories. Integrating a semantic layer into the BCO-DMO data system architecture improves data and information resource discovery, access and integration.

Speaker: Cynthia Chandler

Time: 11:20 a.m.

Location: 2020 Moscone West


Distributions and Controls of Carbonate Chemistry on the Northeastern U.S. Shelf

Recent work on coastal carbon has shown that waters of the northeastern U.S. shelf including Gulf of Maine and the Mid-Atlantic Bight have lower pH, aragonite saturation states and less buffer capacity than the southern U.S. shelves. This suggests that the region may be more susceptible to acidification pressures than previously thought. Further studies on carbonate chemistry in this region are warranted to understand its variability and various controlling mechanisms, which in turn are important to understand potential ocean acidification effects on ecosystems and fisheries. Both legacy and newly-collected data are used in the present study to examine seasonal and spatial variability of relevant carbonate parameters, including dissolved inorganic carbon (DIC), total alkalinity (TA), pH, and ΩA, in the region.

Speaker: Zhaohui Aleck Wang

Time: 2:55 p.m.

Location: 3009 Moscone West


Processes Driving Natural Acidification of Western Pacific Coral Reef Waters

Rising levels of atmospheric carbon dioxide (CO2) are acidifying the oceans, reducing seawater pH, aragonite saturation state (Ωar) and the availability of carbonate ions (CO32-) that calcifying organisms use to build coral reefs. Today’s most extensive reef ecosystems are located where open ocean CO32- concentration ([CO32-]) and Ωar exceed 200 μmol kg-1 and 3.3, respectively. However, high rates of biogeochemical cycling and long residence times of water can result in carbonate chemistry conditions within coral reef systems that differ greatly from those of nearby open ocean waters. Results will be presented from research in the Palauan archipelago.

Speaker: Kathryn E F Shamberger

Time: 5:15 p.m.

Location: 3009 Moscone West

Last updated: December 5, 2013