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Monday, Feb. 20, 2012

Deep Realm Research Beyond the Census Of Marine Life: A Trans-Pacific Road Map

The ChEss project of the Census of Marine Life (2002-2010) helped foster internationally coordinated studies worldwide with a particular emphasis on exploration for, and characterization of new deep-sea chemosynthetic ecosystem sites in four key geographic locations. This work has advanced our understanding of both the nature of, and what controls, the biogeography and biodiversity of these ecosystems. The ChEss program made key advances in each of four major study areas (the Atlantic Equatorial Belt, the New Zealand region, the Polar Oceans of the Arctic and Antarctic and the SE Pacific close to the Chile Triple Junction). But this was only achieved through a judicious combination of long-term planning and astute inter- and intra-national collaborations. These perspectives have enabled us to identify and recommend important future research directions to a new and emerging project, INDEEP, born from the synthesis of the Deep Realm CoML programs focused on mid-ocean ridges, abyssal plains, seamounts and margins, in addition to our own ChEss program. These future priorities include continued exploration of the deep ocean ridge-crest, an increased focus on potential anthropogenic impacts upon these enigmatic deep-sea ecosystems and a concerted future effort to link with other scientists active in the Deep Ocean Realm for a major investigation of the South Pacific Ocean the world’s largest contiguous habitat for life but also its least investigated deep ocean basin.


Speaker: Chris German, Geology & Geophysics

Time: 8:15 a.m.

Location: Ballroom F


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Ekman Veering, Inertial Motions, and Turbulent Fluxes in Arctic Surface Waters Under Sea-Ice
Ice-ocean interactions on inertial to monthly timescales are studied using winter 2009-2010 observations from the first Ice-Tethered Profiler equipped with a velocity sensor. Ocean velocity spiraled clockwise and decayed with depth through the surface mixed layer. Directly-estimated turbulent momentum flux just below the ice-ocean interface was correlated with the ice-ocean velocity difference, allowing a drag coefficient to be estimated. The ice-ocean drag coefficient had larger values derived for straight ice-drift segments and certain ice-drift directions. The surface-layer turbulent kinetic energy dissipation rate also scaled with ice-ocean velocity shear. Inertial or tidal energy in the ice velocity and internal wave fields was observed throughout the record with elevated energy associated with increased stratification within the surface layer and a slightly thicker surface layer. The direct turbulent heat flux was primarily upward, and the direct turbulent salt flux had alternating sign due to brine rejection during ice formation and internal wave mixing and entrainment. Analyses of this and future ITP-V data sets will advance understanding of ice-ocean interactions and their parameterizations in numerical models.

 

Speaker: Sylvia Cole, Physical Oceanography

Time: 8:45 a.m.

Location: Ballroom C

 

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Initial Pioneers Matter: Non-Deterministic Succession After Catastrophic Disturbance At A Deep-Sea Hydrothermal Vent
Deep-sea hydrothermal vents experience major tectonic and magmatic disturbances that eradicate the resident fauna. One might assume that vent communities are well adapted to disturbance and recover quickly to their original state. A catastrophic eruption on the East Pacific Rise at 9°50N in 2006 provided a natural perturbation in which to test this idea. We monitored larval supply and colonization for two years after the eruption and found that faunal change differed substantially from succession patterns described after a 1991 eruption at this site. Two dominant pioneers, the gastropods Ctenopelta porifera and Lepetodrilus tevnianus, still persisted two years after the disturbance though neither had been prominent previously. Many other species typically found at the site had not yet appeared. Measurements of temperature, pH and free sulfide in the vent environments suggested that the post-eruption sites should have been habitable by these species. Our results indicate that temporal variation in larval availability and composition of initial colonists can have a lasting effect on vent community structure and regional biodiversity.

 

Speaker: Lauren Mullineaux, Biology

Time: 9:15 a.m.

Location: Room 150

 

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Characterization And Lability Of Dissolved Organic Matter Produced By Marine Phytoplankton: Linking Biological And Chemical Diversity
Extracellular release of fixed carbon from marine phytoplankton is a major source of oceanic dissolved organic matter (DOM). If phytoplankton produce and release DOM of varying composition, DOM may impact marine biodiversity by acting as a link between autotrophic and heterotrophic community structure. To examine extracellular release of DOM by phytoplankton with an emphasis on how species diversity influences the composition of DOM, we characterized and compared organic material released by various marine phytoplankton in culture. DOM from axenic phytoplankton cultures (Prochloroccocus marinus, Synechococcus sp., Phaeodactylum tricornutum, etc.) was captured by solid-phase extraction and analyzed using mass spectrometry. We found that while a small fraction of the DOM released was common to all isolates tested, the majority was specific to individual strains or groups, suggesting a relationship between phytoplankton species and DOM composition. Phytoplankton-derived DOM suites were also given to axenic cultures of heterotrophic bacterioplankton (multiple SAR11 subgroups, Roseobacter lineage, Bacteroidetes, etc.) to assess lability. Certain DOM additions resulted in increased growth rate and cell abundance for particular bacteria, further implicating DOM as a potential driver of marine microbial biodiversity.

Speaker: Jamie Becker, Biology

Time: 9:15 a.m.

Location: Ballroom D

 

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Physical Controls On An Estuarine Harmful Algal Bloom
Harmful algal blooms of the genus Alexandrium produce a toxin associated with Paralytic Shellfish Poisoning and can cause significant economic and human health impacts. In the northeastern US and Canada, Alexandrium blooms occur both in the open waters of the Gulf of Maine and in coastal embayments and estuaries, and the links between these populations are not well understood. Combining observations and a numerical model, we evaluate the bloom dynamics in one such estuary, the Nauset Marsh System on Cape Cod. Several physical factors, including bathymetry, stratification, and convective mixing, combine with the organism motility to promote retention of cells within subembayments of the estuary. The model is used to link the spatial heterogeneity in estuarine residence time to organism growth rates, and the residence time distributions are consistent with the bloom intensity. Export of cells from the estuary to the coastal ocean is limited, but import from the coastal bloom to the estuary is observed. Exchange of cells between the estuary and coastal ocean is sensitive to the timing and magnitude of meteorological forcing during bloom development.

Speaker: David Ralston, Applied Ocean Physics & Engineering

Time: 10:30 a.m.

Location: 250

 

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A New Dynamical Modeling Framework For Interpreting Phytoplankton Natural Fluorescence

A new analytical framework will be introduced for describing and interpreting the dynamical changes seen in phytoplankton natural fluorescence within a diurnal period. The framework is based on the basic photochemical and nonphotochemical processes known to affect the fluorescence emission of phytoplankton, and it replicates the dynamics of fluorescence-irradiance trajectories seen in laboratory cultures (i.e., natural fluorescence) and in field observations (i.e., sun-stimulated fluorescence) over diurnal periods. When implemented as a model for curve-fitting purposes, the model parameters retrieved illustrate how day-to-day changes in estimated model parameters can be used to track physiological changes in photosynthesis over multi-day timescales in actual experimental and field data. Current challenges with this analytical framework include the ability to account for short-term perturbations to the fluorescence-irradiance trajectories caused for example by intermittent clouds or rapid vertical mixing in the water column, both a focus of ongoing study.

Speaker: Sam Laney, Biology

Time: 12:15

Location: Ballroom E

 

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Radium Derived Mixing Rates And Trace Element Fluxes In The North Atlantic Ocean
The quartet of radioactive radium isotopes (223Ra, t1/2 = 11 d; 224Ra, t1/2 = 4 d; 226Ra, t1/2 = 1600 y; 228Ra, t1/2 = 6 y) that exist in the marine environment occur in vanishingly small quantities, circa 10-16 – 10-23 moles L-1. However, recent advances in sampling technology coupled with rapid ship-board analysis of the short-lived isotopes, has made it possible to simultaneously measure full ocean depth profiles of all four isotopes. Radium, conservative in seawater and a marker of seawater-lithosphere interaction, can be used to estimate mixing rates in a variety of ocean settings. For example 223Ra and 224Ra can be used to measure small spatiotemporal mixing processes that occur near the coastline or seabed. In contrast 226Ra and 228Ra can provide information on larger-scales such as cross-basin and diapycnal mixing rates. Here we will present preliminary Ra data and associated mixing rates from two recent field campaigns that skirted the Eastern and Northwestern Atlantic margins. Furthermore, we will then demonstrate the usefulness of these Ra-derived mixing rates in compiling geochemical fluxes of other trace elements.

Speaker: Paul Morris, Marine Chemistry & Geochemistry

Time: 3:30 p.m.

Location: Ballroom B

 

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Examination Of The Influence Of The Path Of Kuroshio On Meridional Eddy Transport Of Sensible And Latent Heat In The Troposphere
Previous studies of the relation between interannual changes in the path of the Kuroshio and Gulf Stream on the synoptic variability of the wintertime (JFM) atmospheric boundary layer (Joyce, Kwon, and Yu 2009) have been augmented by inclusion of the Oyashio path and extended into the troposphere using MERRA atmospheric reanalysis for the 24 year period of 1983-2006, inclusive. In addition, we have analyzed the intra-seasonal (8-90d) contribution of the transient eddy fluxes in the atmosphere as well as the synoptic band (2-8d). We find that at mid-latitudes, approximately 2/3 of the thermal flux in the atmosphere is due to sensible heat and 1/3 due to moisture. The intra-seasonal and synoptic bands contain approximately equal contributions to the vertically-integrated transient eddy signal, although they have distinctly different spatial characteristics. While the statistical dependence of atmospheric fluxes on path shifts of the Gulf Stream and Oyashio has been carried out, in this report we will focus on the relationship with the interannually-changing path of the Kuroshio Extension, which represents the most significant hemispheric influence of the ocean on the atmosphere, accounting for as much as 10% of the record’s winter mean, zonally-integrated, transient thermal energy transport in the mid-latitude troposphere.

Speaker: Terry Joyce, Physical Oceanography

Time: 3:45 p.m.

Location: Ballroom H

 

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Phenology Of Sea Ice And Ocean Algal Blooms In The Arctic
Arctic organisms are adapted to the strong seasonality of environmental forcing. A small timing mismatch between biological processes and environment could have a significant consequence for the entire food web. Climate warming is likely to induce early snow melt and ice retreat in the Arctic, thus causing timing variability (phenology) of primary production for both ice algae and phytoplankton. This study is focused on synthesizing the available observations and coupled ice-ocean-ecosystem model results to examine the spatial variability in primary production phenology in the Arctic, and to test existing conceptual models on region-dependent algae growth. The results allow us 1) to quantify the spatial variability in bloom phenology; 2) to identify the regions most susceptible to climate-related changes in mixing and light/nutrient availability; and 3) to infer the possible impact on zooplankton and higher trophic levels. The numerical experiments also provide insight on the mechanisms controlling the phenological shifts and assess the phenological responses under future climate-change scenarios. It is anticipated that the results from this study will lay the foundation for more comprehensive research in this important area.

Speaker: Rubao Ji, Biology

Time: 3:45 p.m.

Location: Ballroom E

 

Tuesday, 2/21/2012

Fresh Water Transformations And Dynamics In The Arctic Ocean
Recent findings show an unprecedented increase of liquid freshwater (FW) accumulated in the Arctic Ocean’s Beaufort Gyre (BG) in 2003-2011. The release of this FW to the North Atlantic can significantly influence global climate via reduction of the ocean meridional overturning circulation. In this sense the BG as a major FW reservoir is “a ticking time bomb” for climate. On the other hand, the EWG Atlas of the Arctic Ocean shows that the BG FW reservoir is a stable feature of the Arctic Ocean and can be considered as a flywheel of the Arctic Ocean circulation. An important scientific question is whether significant changes of these flywheel mechanics can be expected in the near future. Investigation of this paradox requires a comprehensive analysis of both observational data and numerical model output to examine conditions, mechanisms and variability of FW accumulation and release in the BG region, and the sensitivity of these processes to atmospheric and ocean circulation regimes, ocean mixing, changes in the FW sources (rivers, precipitation, ocean straits), and sea ice and atmospheric thermodynamic conditions In this presentation we analyze historical and recent observational data, results from a set of idealized and realistic numerical experiments specifically designed to understand FWC transformations, and the sensitivity of these transformations to different external (sea ice and atmospheric conditions) and internal (advection and mixing) processes.

Speaker: Andrey Proshutinsky, Physical Oceanography

Time: 8:00 a.m.
Location: Room 150

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Cross-Shelf Transports: The Problem That Does Not Die
Cross-shelf transports undoubtedly occur in the coastal ocean: inner shelf waters are almost always salty. These exchanges are critical for nutrient cycling, sediment transport and contaminant dispersal, to name just a few. From a physical perspective, the problem is hard because Earth’s rotation inhibits steady flow across isobaths, so that cross-shelf exchanges must be dissipative, episodic, or unusually intense. Some types of cross-shelf transports that are roughly understood, including wind-driven upwelling, surf zone undertow, and shear dispersion. Attention here is on the difficulties and opportunities associated with a few illustrative, less-understood mechanisms. For exchanges across a shelfbreak front, time-dependence and nonlinearity allow net fluxes, but the observational problem is difficult because the exchange is inefficient. In bottom boundary layers, turbulent frictional effects allow cross-shelf transports, but we still do not understand the bounds of buoyancy arrest. Buoyancy currents, unless they are very large, tend to die out alongshore, implying cross-shelf dispersal, but the mechanism and rates are, to date, poorly understood. Progress will likely involve using models that are evaluated against the more observable integrated aspects of measurements.

Speaker: Kenneth Brink, Physical Oceanography

Time: 10:30 a.m.
Location: Room 251

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Science Communication In Times Of Crisis: Outreach Lessons From The Gulf Of Mexico And The Pacific Coast Of Japan
The Deepwater Horizon oil spill and accidental release of radiation from the Fukushima Daiichi nuclear power plant represent two recent events related to the ocean that captured public attention for months. The public desire for information in part motivated scientists and communications staff at the Woods Hole Oceanographic Institution to organize expedition-based outreach activities to communicate efforts to study the effects of both events on the marine environment. The urgent and potentially controversial nature of both highlighted the need for a well thought-out communications plan that includes a mix of traditional, social, and multi-media. Real-time outreach from the Gulf of Mexico centered around a 6-day cruise in December 2010 with DSV Alvin and AUV Sentry using the educational website Dive & Discover and that presented information through a broad mix of media channels. After the March 2011 earthquake, tsunami and nuclear accident in Japan, efforts focused on a more traditional, text- and photo-based cruise blog. Both of these efforts offer insights into planning and implementing effective science outreach in times of crisis, as well as under less urgent circumstances.
Speaker: Ken Kostel, Communications

Time: 11:00 a.m.

Location: Ballroom F

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Finescale Observations Of The Middle Atlantic Bight Shelfbreak And Slope
The shelfbreak and slope in the Middle Atlantic Bight (MAB) are highly variable regions that remain poorly understood. Recent glider observations south of Cape Cod provide finescale observations over the upper 1000 m in the MAB. We examine temperature and salinity structure along both isopycnals (i.e., spice) and depth surfaces at scales from O(1)-O(100) km to determine how the dominant scales of variability change from shelfbreak to slope. Bidirectional exchange across the shelfbreak front contributes significantly to the thermohaline variability in the region; cool, fresh shelf waters are regularly found over the slope, and warm, salty slope waters are frequently found inshore of the shelfbreak. Observations from a four month glider deployment over the shelfbreak to mid-slope as well as a shorter deployment that traversed the periphery of a warm-core ring are used to characterize the scales of variability.

Speaker: Robert Todd, Physical Oceanography
Time: 11:15 a.m.
Location: Room 251

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Impact Of Arctic And Atlantic Variability On Greenland’s Glaciers
Increasing evidence suggests that ocean variability triggered the recent acceleration of glaciers in western and southeastern Greenland leading to a doubling of the ice sheet’s contribution to sea-level rise. This hypothesis is supported by the fact that the timing of the glaciers’ acceleration coincided with the recent warming of the subpolar North Atlantic and by recent measurements showing that warm, salty waters of subtropical origin circulate rapidly through these fjords. Yet the processes regulating the inflow and variability of warm, salty waters inside Greenland’s glacial fjords are complex and involve crossing shelves that are strongly influenced by cold, fresh waters of Arctic origin. Here, I will present recent measurements from one major glacial fjord in southeast Greenland and historical data, including a reconstruction of the shelf variability over the last 120 years, which indicate that the properties at the glaciers’ margins and the glaciers’ stability are affected both by Arctic and Atlantic variability on interannual to decadal time scales
Speaker: Fiamma Straneo, Physical Oceanography
Time: 11:15 a.m.
Location: Room 150

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Direct Observations Of Formation And Propagation Of Subpolar Eddies Into The Subtropical North Atlantic
Subsurface float and moored observations are presented to show for the first time the formation and propagation of anticyclonic submesoscale coherent vortices that transport relatively cold, fresh subpolar water to the interior subtropical North Atlantic. Acoustically tracked RAFOS floats released in the southward-flowing Western Boundary Current at the exit of the Labrador Sea reveal the formation of three of these eddies at the southern tip of the Grand Banks (42°N, 50°W). It was found that the eddies had average rotation periods of 5–7 days at radii of 10–25 km, with mean rotation speeds of up to 0.3 m s-1. One especially long-lived (5.1 months) eddy crossed under the Gulf Stream path and translated southwestward in the subtropical recirculation to at least 35°N. Velocity, temperature and salinity measurements from a nine-month deployment of two moorings south of the Gulf Stream at 38°N, 50°W reveal the passage of at least two eddies with similar hydrographic and kinematic properties. The core temperature and salinity properties of the eddies imply their formation at intermediate levels of the Labrador Current south of the Tail of the Grand Banks. These observations confirm earlier speculation that eddies form in this region and transport anomalously cold, low-salinity water directly into the subtropical interior.

Speaker: Amy Bower, Physical Oceanography
Time: 11:30 a.m.
Location: Ballroom A

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Impacts Of The Fukushima Dai-Ichi Nuclear Power Plants On The Ocean
The triple disaster of the March 11, 2011, earthquake, tsunami and subsequent radioactivity releases from the Fukushima Dai-ichi nuclear power plants are unprecedented events for the oceans. In response, we organized a research cruise in June, 2011 off Japan to study Fukushima derived radionuclides in the waters and biota off Japan. This presentation will provide an overview of these successful sampling activities and our plans for analyses of a wide range of radionuclides. For this talk we will focus on the cesium-137 and cesium-134 surface distributions and vertical profiles obtained during this cruise. The highest cesium concentrations at that time were not necessarily at the closest sampling point 30 km from the Fukushima NPPs, but 70-100 km off shore. The data also suggests that the Kuroshio Current prevents the southward spreading of contaminated water. 134Cs/137Cs activity ratios (1.0 at source) indicate Fukushima-derived cesium out to at least 600 km off shore. These results are discussed in context of prior cesium levels in the waters off Japan and in comparison to radionuclide results from other studies in 2011 off Japan.
Speaker: Ken Buesseler, Marine Chemistry & Geochemistry
Time: 11:30
Location: Ballroom E

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The Effect Of Stratification On Wind-Driven, Cross-Shelf Circulation On The Inner Shelf
Three years of observations from the inner shelf south of Martha’s Vineyard, MA are used to describe the effect of stratification on wind-driven, cross-shelf circulation and transport. For along-shelf wind stress, the fraction of full Ekman transport scales with stratification, and the surface mixed layer thickness clearly limits the depth of the first zero-crossing of the velocity. For cross-shelf wind stress, stratification increases cross-shelf transport, but a 1D view of the dynamics is not sufficient to explain the relationship between circulation and stratification. For both wind orientations, the sign of wind stress driving offshore surface flow generates a more sheared circulation and a larger increase in transport between mixed and stratified conditions.
Speaker: Rachel Horwitz, Physical Oceanography
Time: 11:45 a.m.
Location: Room 251

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Tracing The Circulation Around Fukushima
Following the release of radioactive isotopes from the Fukushima nuclear power plants, we undertook a cruise to sample the ocean waters off the eastern coast of Japan. As part of this effort, 24 surface drifters were deployed and subsequently tracked. The trajectories of these drifters indicate that much of the contaminated water was being pulled away from the coast on the northern side of Kuroshio Extension. However, some of the drifters stayed in the coastal region suggesting that some contaminated water may recirculate in this area before being washed off-shore. The absence of drifter crossings across the Kuroshio Extension core suggests that it inhibits the southward spreading of contaminated water, at least over the western Pacific ocean. Measurements of different radioactive contaminants seem to agree with our interpretation based on drifters. Using the drifter trajectories, we test and validate methods to extend the tracking back to the initial releases and into the future to track the fate of the contamination.
Speaker: Steven Jayne, Physical Oceanography
Time: 11:45 a.m.
Location: Ballroom E

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Swimming Behaviors Of Barnacle Larvae In Response To Waterborne Settlement Cues
Substratum-bound and waterborne chemical cues that induce larval settlement in late-stage barnacle larvae (cyprids) have been characterized well. While searching behaviors and settlement selection in response to these cues are well described, experiments examining the effects of waterborne cues on larval swimming behaviors under natural flow conditions are rare. We are using digital video observations, larval tracking, and flow characterizations to examine how cyprids respond to waterborne cues in field-relevant turbulent conditions. Preliminary experiments in still-water containers suggest that the average cyprid vertical swimming velocity switched from upward to downward when a homogenously dissolved waterborne cue was present. Subsequent experiments in a large racetrack flume examining changes in vertical swimming behaviors (e.g., velocity, tortuosity, sinking rate) as larvae come into contact with filaments of cue in turbulent flow will also be presented.
Speaker: Shawn Arellano, Biology
Time: 11:45 a.m.

Location: Ballroom D

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Fish And Shark Responses To Non-Linear Internal Waves: Foraging And Vertical Re-Distribution
Fish and sharks respond to large-amplitude internal waves (IWs) that are generated semidiurnally at Race Point (RP), a headland at the northern tip of Cape Cod, Massachusetts. SAR observations indicate that RP IWs tend to impact Stellwagen Bank’s southern flank, a shallow bank 10 km distant from RP. Sand lance, a planktivorous fish, moved up in the water column in response to surface-intensified, horizontally propagating IWs approaching this area. Sand lance may have responded to zooplankton patches concentrated in the waves. Fish near the bottom might have detected the IWs via changes in pressure and velocity produced by the waves. We estimated the wave properties with a fully-nonlinear model that provides estimates of wave-induced pressure and velocity fields over the full depth. Small sharks responded to IWs in two ways. First, sharks moved up and down in concert with the IWs. Second, shark vertical distribution changed from vertically extended before the waves, to bottom-layer constrained during the passage of the waves. Compression of vertical range may be related to observed two-way circulation, and shear zone avoidance.
Speaker: Jesús Pineda, Biology
Time: 12:00 p.m.
Location: Ballroom B

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Influences Of Precipitation On Water Mass Transformation And Meridional Overturning In Marginal Seas
The influences of precipitation on the properties of water mass transformation and the strength of the meridional overturning circulation in marginal seas are studied using theoretical and idealized numerical models. Nondimensional equations are developed for the temperature and salinity anomalies of deep convective water masses, making explicit their dependence on both topography as well as on the strength of atmospheric forcing. In addition to the properties of the convective water, the theory also predicts the magnitude of precipitation required to shut down deep convection and switch the circulation into the haline mode. High resolution numerical model calculations compare well with the theory for the properties of the convective water mass, the strength of the meridional overturning circulation, and also for the shutdown of deep convection. The model also shows that for precipitation levels that exceed this critical threshold, the circulation remains in a thermally direct mode even in the absence of deep convection.
Speaker: Michael Spall, Physical Oceanography
Time: 2:15 p.m.
Location: Ballroom H

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A Global Estimate Of Ocean Age And Transit Times Inferred From Radiocarbon Observations
A number of previous observational studies have found that the waters of the deep Pacific Ocean have an age, or elapsed time since contact with the surface, of 700 to 1,000 years. Numerical models suggest ages twice as old. Here we present an inverse framework to determine the mean age and its upper and lower bounds given GLODAP radiocarbon observations, and we show that the potential range of ages increases with the number of constituents or sources that are included in the analysis. The inversion requires decomposing the world ocean into source waters, here obtained using the Total Matrix Intercomparison method at up to 2 by 2 degree horizontal resolution with 11,113 surface sources. We find that the North Pacific at 2,500 meters depth can be no younger than 1,100 years old, which is older than some previous observational estimates. A best estimate of mean age is also presented using the mixing history along circulation pathways. Subject to the caveats that the estimate would benefit from further observations and that radiocarbon cannot rule out the presence of extremely old waters from exotic sources, the deep North Pacific waters are 1,200 to 1,500 years old, which is more in line with existing numerical model results
Speaker: Geoffrey Gebbie

Time: 2:30 p.m.
Location: Ballroom C

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Wave Effects And Stable Boundary Layers On Air-Sea Fluxes
Many internal turbulence aspects of the ocean boundary layer can affect the sea surface temperature, thereby influencing the fluxes of latent heat, sensible heat, and upwelling long wave radiation. In this work we focus on the effects of turbulence created by wave breaking and Langmuir circulations on the sea surface temperature, and on the effects of a strongly stable ocean boundary layer. These varying aspects of the upper ocean are studied singly and in concert through the use of a second moment closure model that models the enhancement of turbulence kinetic energy from both wave breaking and Langmuir circulations. The effect on the surface fluxes of these variations in sea surface temperatures are shown for a range of conditions that are appropriate to the regimes in which they are occurring.
Speaker: Carol Anne Clayson, Physical Oceanography
Time: 3:30 p.m.
Location: Ballroom B


Wednesday, 2/22/2012

Plenary Lecture

How Did We Do:  Academia’s Contributions to the Gulf of Mexico Oil Spill 

When the Deepwater Horizon disaster occurred, marine scientists, most with little background in oil spills, became quickly involved and delivered ideas, initial results, and data to decision makers. These contributions can be traced back to the training, research, and experience of basic marine science allowing academia to make important contributions when applied problems arise.

Speaker: Christopher Reddy, Marine Chemistry & Geochemistry

Time of Presentation: 11:30 a.m.

Location: Ballrooms A-H

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Development Of High-Frequency Broadband Acoustic Scattering Techniques For Imaging, Classification, And Quantification Of Stratified Turbulence And Zooplankton
Narrowband acoustic backscattering techniques have been used to image the ocean interior for decades, resulting in spectacular images of physical processes, such as internal waves, and marine organisms, such as fish and zooplankton. Yet interpretation of the acoustic returns in terms of relevant physical or biological parameters has remained challenging. Emerging broadband acoustic backscattering techniques result in increased range-resolution and spectral coverage, improving imaging, classification, and quantification capabilities. This presentation highlights the power of broadband acoustic backscattering techniques to complement more traditional sampling techniques. Results are presented of the successful application of these techniques to image and parameterize at high-resolution 1) stratified turbulence in an estuarine environment and 2) zooplankton in the northwestern Atlantic. This presentation addresses the circumstances when the increased range resolution alone can result in increased understanding of the small-scale physics and biology, the physics-based interpretation of the acoustic spectra in terms of relevant parameters, and the potential for exploiting the echo-statistics for classification of scattering processes.

Speaker: Andone Lavery, Applied Ocean Physics & Engineering

Time: 3:00 p.m.
Location: Room 250

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Spatial Patterns Of Genetic Variation In The Widespread Cold-Water Bubblegum Coral Paragorgia Arborea
Numerous cold-water corals species have apparent widespread and discontinuous distributions. Many of these are foundation species in hard-bottom benthic ecosystems (e.g the bubblegum coral Paragoriga arborea). Theoretically, differences in the genetic composition of their populations vary with geographic distance and depth. Previous studies have examined the genetic diversity of some of these taxa in a regional context, suggesting that genetic differentiation does not occur at scales of discrete features such as seamounts or canyons, but at larger scales (e.g. ocean basins). However, to date no studies have evaluated such diversity throughout the entire known distribution of a cold-water coral species. We utilized mitochondrial and nuclear genetic variants in a phylogeographic context to examine the compatibility of this morphospecies with the genealogical-phylospecies concept by examining specimens collected over its nearly entire known distribution. Global genetic variation revealed basin scale differences, but no significant correlation with depth. To explore further these patterns of variation, next-generation sequencing approaches are underway.
Speaker: Santiago Herrera, Biology
Time: 3:00 p.m.
Location: Room 150



Thursday, 2/23/2012

From Pipe To The Beach: Weathering Of Macondo Well Oil
Following the Deepwater Horizon disaster, the Macondo well released approximately 160 million gallons of oil. Two years later, oil residues continue to persist. While it is difficult to estimate how much of these residues exist, they can be used to monitor and examine changes in the oil composition as it flowed from the well through the water column to the surface and then to the beach. Here, I will discuss these changes based on the results of numerous analytical methods. In general, rather small changes in the overall composition of the oil occurred after surfacing. Most interestingly, abiotic reactions leading to more polar and oxidized components in the oil residues have been observed in beach samples.

Speaker: Christopher Reddy, Marine Chemistry & Geochemistry

Time: 8:30 a.m.
Location: Ballroom E

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Laboratory Experiments On The Stability Of Two Adjacent Buoyant Coastal Currents
Considerable work is needed to improve our understanding of how buoyant waters transport pollution and sediments along coastlines, in particular, when multiple buoyant sources are present. Laboratory experiments have been used to investigate the stability of two adjacent buoyant coastal currents having different densities. An interesting aspect of the instability of ‘coupled’ fronts is that, in some instances, the instability of one front dominates the evolution and development of the other front. That is, one of the fronts becomes unstable while the other does not, and only after the instabilities grow to large amplitude the ‘stable’ front becomes distorted and ‘follows’ the meandering of the unstable front. This coupled frontal instability presents important differences from the previously studied instability of a single current. The present experiments show that increasing the frontal separation between the two buoyant currents allows the instability to de-couple. Furthermore, the presence of a sloping bottom stabilizes the inner front instability and, due to the reduced water depth, increases the number of meanders of the outer front, hence contributing to de-coupling the instability of the two fronts.
Speaker: Claudia Cenedese, Physical Oceanography
Time: 9:00 a.m.
Location: Room 251

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Assessing The Impact Of Ocean Acidification On Marine Planktonic Calcification Using Satellite Analysis And Earth System Modeling
Marine planktonic calcifiers such as coccolithophores, foraminifera, and pteropods play a fundamental role in the ocean carbon system, a role that may be modified substantially by rising atmospheric CO2 and climate change. We will present results from the initial phase of this study to better constrain the magnitude of ocean acidification and climate change impacts on marine inorganic carbon dynamics. In particular we will present improvements to our primary numerical tool, the new Community Earth System Model, version 1 (CESM, v.1), a variant of the widely used Community Climate System Model (CCSM) that includes fully interactive marine ecosystem and global carbon modules. Comparisons will be made to the earlier version (CCSM v3.0) coccolithophore fields as well as to historical satellite remote sensing (SeaWiFS; MODIS). Characterization of the biogeographic niche for marine calcifiers; i.e., the temperature, circulation and seawater chemistry "phase-space" for calcifiers will be shown.

Speaker: David Glover, Marine Chemistry & Geochemistry

Time: 9:15 a.m.
Location: Ballroom D

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Functional Connectivity Of Coral Reef Fishes In A Red Sea Coral Reef Seascape Assessed By Compound-Specific Stable Isotope Analysis
Tropical marine habitats are under mounting anthropogenic pressure, leading to declines in their function and resilience on a global scale. Maintaining functional connectivity among these habitats is critical for maintaining population resistance and resilience in these systems. However, quantifying movements of individuals within seascapes remains a major challenge. We provide the first use of a new compound-specific stable isotope technique to determine connectivity of a reef fish within a coral reef seascape. Our data revealed significant plasticity in juvenile nursery use that was not apparent from traditional visual surveys. Contrary to the current paradigm of a linear abundance gradient from presumed wetland nurseries to adult reef habitat, we found that seascape configuration played a critical role in determining functional connectivity among habitats. While some juveniles migrated over 30 km from coastal nurseries to coral reefs, others settled into shallow areas around a continental island or directly into adult reef habitats. Identifying linkages among distinct habitats within tropical seascapes will be necessary when developing management strategies to sustain coral reefs and the fisheries they support.

Speaker: Kelton McMahon, Biology

Time: 9:15 a.m.
Location: Ballroom A

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Circulation And Mixing In Greenland's Glacial Fjords Inferred From Pathways And Transformation Of Glacially Modified Waters
Recent studies indicate that the ocean plays a key role in the mass-balance of the Greenland ice sheet through submarine melting of outlet glaciers. These glaciers drain the ice sheet into deep, strongly stratified fjords, many of which are characterized by a subsurface layer of warm, Atlantic-origin water. Greenland’s glacial fjords cannot be explained by traditional fjord paradigms because significant density modification and forcing occurs at the glacier front from melting and from the addition of glacial runoff. Despite the importance of understanding the oceanic heat transport to glaciers, little is known about the basic dynamics of such fjords. Here we use hydrographic surveys of two fjords in southeastern Greenland (Sermilik and Kangerdlugssuaq fjords, which drain Helheim and Kangerdlugssuaq glaciers, respectively) collected from 2008 to 2011, together with continuous records from moored instruments, to identify glacially modified waters and trace their evolution into the ambient stratification. We then use these export pathways of glacially modified water to diagnose the circulation and mixing patterns within the fjords.

Speaker: Rebecca Jackson, Physical Oceanography

Time: 9:30 a.m.
Location: Room 250

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A New Record Of Particle Flux At The Bermuda Atlantic Time-Series Site From Neutrally Buoyant Sediment Traps
We present the results of the first time-series deployment of neutrally buoyant sediment traps (NBSTs) from 2007 to 2010 at the Bermuda Atlantic Time-series Site (BATS). Upper ocean particle flux is a key parameter measured at U.S. ocean biogeochemistry time-series sites. Over the last two decades, biases caused by sample solubilization, swimmer removal methods, and hydrodynamic effects in traditional surface tethered traps have been brought to light. NBSTs have been developed in an attempt to reduce the effect of hydrodynamic biasing. Two NBSTs were deployed each month at 150 m at the same time as surface-tethered particle interceptor traps (PITS) deployed by BATS. In most months the two sediment trap systems agreed within a factor of two, within the range of agreement of two NBSTs or individual PITS tubes. However, on eight occasions over the course of the study there were large excursions in the PITS, which collected up to five times more material than the NBSTs. We investigate the possible causes of the discrepancies between the two systems and also the importance of swimmer removal techniques and sample blanks.

Speaker: Stephanie Owens, Marine Chemistry & Geochemistry

Time: 11:00 a.m.
Location: Ballroom B

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Dynamics Of Wind-Forced Upwelling In The Alaskan Beaufort Sea And Associated Shelf-Basin Fluxes
Upwelling occurs frequently along the continental slope of the Alaskan Beaufort Sea, driven by remote Pacific-born storms (Aleutian lows). These events result in a cross-stream exchange of heat, salt, and nutrients that can significantly impact both the Beaufort shelf and the interior Canada Basin. Here we use wind data, atmospheric re-analysis fields, oceanic data, and a simplified ocean numerical model to investigate the dynamics of the upwelling and the nature and magnitude of the cross-stream exchange. We focus primarily on a single storm event that occurred in November 2002 when the region was roughly 50% covered by pack-ice. The presence of ice enhanced the ocean response to the storm and the return flow was not confined to the bottom boundary layer. This is consistent with the momentum balance which includes a significant contribution from the cross-stream advection of alongstream momentum. An analysis of the parcel trajectories during the storm from the model reveals varying patterns across the shelfbreak and continental slope. Seasonal trends in the upwelling are discussed using a two-year mooring timeseries.

Speaker: Robert Pickart, Physical Oceanography

Time: 11:30 a.m.
Location: Room 250

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Impact Of Ice Cover On Wind-Forced Exchange In The Alaskan Beaufort Sea
The Alaskan Beaufort shelf is fed by Pacific water emanating from Bering Strait, and is strongly wind-forced in fall and winter due to the passage of synoptic storms. The pack-ice tends to be fast on the inner shelf and more mobile farther offshore, modulating the water column response to such storms. Here we use data from the first-ever mooring array extending from the inner shelf to the continental slope to investigate the cross-shelf exchange and water column properties during two wind events characterized by differing ice conditions. In the first event (early December 2008) the ice was mobile everywhere, while much of the shelf was covered by fast ice during the second event (early February 2009). The salinity, temperature and velocity responded strongly to the along-shelf winds when the ice cover was mobile everywhere. By contrast, in the fast-ice case there was no clear relationship between the circulation and the wind except near the shelfbreak where the ice remained mobile throughout the event. The connectivity between the inner and outer shelves and resulting cross-shelf transport is assessed in each case.

Speaker: Jeremy Kasper, Physical Oceanography

Time: 11:45 a.m.
Location: Room 250

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Vertical Structure And Productivity From The Cariaco Time Series: Implications For Interpreting Satellite Ocean Color
Ocean color is an effective tool for estimating primary production where most phytoplankton growth is near-surface. However, in stratified, nutrient-limited environments, some of the production occurs below the mixed layer, and may go undetected by remote sensing. This issue is explored through analysis of vertical profiles of density, primary productivity, chlorophyll, nutrients and phytoplankton in a 14 year, NSF-funded record from the Cariaco (CArbon Retention In A Colored Ocean) Basin time series project located on the Venezuelan continental shelf (10.5° N, 64.67° W). Using a simple 1D model for the vertical nutrient flux and uptake, we explain much of the variability of the vertical nutrient and chlorophyll distribution in the monthly station profiles. The model reproduces essential features of the observed vertical structure based on surface temperature and light penetration, and may be useful for predicting the timing and bias in ocean color-based chlorophyll and productivity within the basin. Unique aspects of the Cariaco Basin and the applicability of the model to other locations are discussed.

Speaker: Melissa Omand, Physical Oceanography

Time: 12:00 p.m.
Location: Ballroom B

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Physiological And Behavioral Responses To Sound In The Longfin Squid (Loligo Pealeii)
While responses to sound have been described in many underwater vertebrate species (e.g., mammals and fish), considerably less attention has been paid to marine invertebrates. Among cephalopods, this is surprising because squid comprise a key component of the ocean’s biomass and play a central role in many marine ecosystems. Here we describe physiological and behavioral responses to sound in squid (Loligo pealeii). Physiological responses were measured using auditory evoked potentials. Hearing ranges and thresholds were established for both pressure and particle-motion components of a sound field. Physiological responses were generated between 20 and 500 Hz, with lowest thresholds between 100-200 Hz. Acceleration alone and brief, low-frequency centered pulses also generated responses. Behavioral responses (jetting and body patterning changes) were initiated in a narrower frequency range (50-300 Hz) and at levels 15-20 dB higher then physiological thresholds. Results suggest squid likely “hear” similar to fish and that squid can sense acoustic stimuli from predators, prey, and ambient or anthropogenic sources. These novel findings are important for understanding controls on habitat ranges, prey selection and predator avoidance in a key marine invertebrate.
Speaker: T. Aran Mooney, Biology

Time: 12:15 p.m.
Location: Room 151

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Time Series Of Pco2, Ph And Aragonite Saturation State In Waquoit Bay National Estuarine Research Reserve – “Estuarine Acidification” And Shellfish
Rising atmospheric carbon dioxide concentrations will tend to increase the dissolved inorganic carbon content (DIC) of coastal waters, lowering their pH and aragonite saturation state (Ωar) values. However, this acidification will be superimposed on the pre-existing carbonate system chemistry of these waters, which in turn reflects both natural processes and human perturbations (e.g., eutrophication). A three-year monthly time series of alkalinity and DIC data from the Waquoit Bay National Estuarine Research Reserve reveals striking annual cycles in seawater pCO2 and pH. Summer pCO2 values are above 700 ppmv throughout the bay, with values above 2000 ppmv in a sub-embayment with restricted flushing; summer pH(total) values are below 7.8 throughout the bay, and below 7.3 in the sub-embayment. These summertime values reflect at least two processes: CO2 release by benthic organic matter decomposition as bay sediments warm each summer, and also acid additions via groundwater discharge and/or oxidation of reduced pore water metabolites. Culture data will be used to illustrate the potential impact of these carbonate system cycles on larval shellfish in the bay.
Speaker: Daniel McCorkle, Geology & Geophysics
Time: 2:00 p.m.
Location: Ballroom G

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Observations Of Surfzone Vorticity
The first field estimates of time-dependent surfzone vertical vorticity are calculated from the flows around a 10-m diameter circular array of 12 current meters. The array was deployed in 1.7-m water depth on the crest of a broad sandbar. Consistent with the hypothesis that surfzone vorticity is generated by finite crest-length breaking waves, changes in vorticity are observed when a breaking crest-end passes through the array. The observations also suggest the vorticity frequency spectrum is red, and assuming a 2D turbulent energy cascade, that finite-crest breaking may be a significant source of energy into the horizontal eddy field. Vorticity statistics will be compared with properties of the wave field, including breaking crest-length, directional spread (hypothesized to control crest-length), and mean alongshore currents. Funded by NSSEFF, ONR, and a WHOI postdoctoral fellowship.
Speaker: David Clark, Applied Ocean Physics & Engineering
Time: 2:45 p.m.
Location: Ballroom I

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Eddy-Induced Particle Dispersion In The Upper-Ocean North Atlantic
Eddy-induced particle dispersion is studied in the upper-ocean North Atlantic using a combination of altimetric sea surface heights, Lagrangian drifter data, and numerically-generated velocity fields. Our analysis demonstrates that transport is inhomogeneous and anisotropic. These effects were quantified by constructing the ``spreading ellipses''. Spreading regimes were analyzed, and significant non-diffusive behavior was found, even at time scales longer than half a year. The influence of the mean advection was studied and diffusivity estimates in the presence of the mean currents were shown to differ significantly from the ``eddy-only'' values. In contrast, the influence of the Ekman velocity on the diffusivity estimates was found to be less significant. The analysis of numerical simulations further demonstrates that the material transport is dominated by eddies with large spatial scales, which can be resolved by altimetry. The anisotropy of dispersion has implications for parameterizing eddy-induced transport in non-eddy-resolving numerical models and is important for modeling distributions of heat, salinity and bio/geochemical tracers.
Speaker: Irina Rypina, Physical Oceanography
Time: 3:45 p.m.
Location: Room 251

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Comparative Study Of The Biogeography And Life History Of North Atlantic Copepods
In this modeling study we address two questions: (1) which factors are responsible for different spatio-temporal patterns of warm- and cold-water copepod species in the Gulf of Maine, and (2) what controls the observed seasonality differences of copepod species between the Gulf of Maine and the North Sea. The biogeographical boundaries of the cold water species Pseudocalanus spp. and the warm water species Centropages typicus overlap in these two shelf areas in the northwestern and northeastern Atlantic respectively, but their life-history characteristics differ significantly. A population model coupled to a three-dimensional ecosystem model including species-specific processes and parameters were used in this study. Our analysis focuses on the relative contribution of feeding strategies, predation control and advection influences. We also tested whether the model with the same parameter set for C. typicus in the Gulf of Maine will reproduce the observed patterns when applied to the North Sea. Differences in the results can reflect site-specific adaptations to the ecosystem and suggest possible missing control mechanisms that need to be included in the model .
Speaker: Christoph Stegert, Biology
Time: 3:30 p.m.
Location: Ballroom D

Friday,  2/24/2012

A Survey Of Waves On Subseasonal Time Scales In The Tropical Pacific Ocean
Data from satellite altimetry and from the TAO/TRITON mooring array are used to characterize and discuss wavelike variability in the tropical Pacific Ocean at periods of days to a few months. The goal is to provide a synthesis view of the variability on subseasonal time scales, with emphasis on an interpretation in terms of wave dynamics. At the higher frequencies (periods of 2-14 days), there is clear evidence for the presence of several basin-scale equatorial wave modes, including Yanai waves and inertia-gravity waves associated with baroclinic modes one and two. At the lower frequencies (periods of 1-2 months), the variability of sea level is dominated by equatorial Kelvin waves and tropical instability waves, although variability resembling barotropic Rossby waves and equatorial Rossby waves is also present.
Speaker: Tom Farrar, Physical Oceanography
Time: 8:00 a.m.
Location: Ballroom H

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Vertical Transport At An Ocean Front
We examine the vertical flux of tracers at an upper ocean front in relation to the eddy dynamics and filament generation arising from frontal instabilities. Using a numerical model, we find that exchange between the mixed layer and pycnocline is significantly enhanced when the frontal density gradient extends into the pycnocline. We explore the implications of such vertical exchange for biological carbon and oxygen fluxes.
Speaker: Jinbo Wang, Physical Oceanography
Time: 8:15 a.m.
Location: Ballroom C

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Observations Of Circulation And Water Mass Transformation In The Eastern Chukchi Sea
Pacific water enters the Chukchi Sea through Bering Strait and progresses northward, impacting numerous aspects of the western Arctic Ocean including ice-melt and ventilation of the upper halocline. In summertime the Alaska Coastal Current (ACC) is the major conduit for warm and fresh Pacific Water. However, to date there have been limited direct observations of the current. Here we use hydrographic and velocity data from multiple summertime surveys to investigate the circulation and intra-seasonal variability of water masses in the Chukchi Sea, with emphasis on the ACC. Contrary to earlier thinking, we demonstrate that the ACC is at times weakly baroclinic, highly variable along the shelf, and can transport multiple water masses that can be objectively defined based on their physical properties. We argue that, in early summer, mixing between surface ACC water penetrating the Chukchi Sea and winter water already on the shelf leads to the formation of a new water mass. This Chukchi Summer Water has the correct density to ventilate the upper halocline, potentially weakening its ability to insulate the deeper warm Atlantic water.
Speaker: Donglai Gong, Physical Oceanography
Time: 8:30 a.m.
Location: Ballroom F

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Estimate Of Global Nitrogen Fixation Rates And Diazotrophic Biomass: Comparing Ccsm Model And Observational Database
Diazotrophs are a key functional group in marine pelagic ecosystems. The biological fixation of dinitrogen (N2) to bioavailable nitrogen forms provides an important nitrogen source for pelagic marine ecosystems and influences primary productivity and organic matter export to the deep ocean. As one of a series efforts of collecting biomass and rate data from different phytoplankton functional groups and model intercomparison, we have constructed a diazotrophic database for global pelagic ocean by collecting direct field measurements of N2 fixation rates and diazotrophic abundances from microscopic counts and nifH gene counts. More than 7,000 data points have been collected covering open oceans, inner seas and coastal regions. Abundance data are converted to diazotrophic biomass by using cell-size estimated biomass conversion factors. The data are used to parameterize and validate the results from the Community Climate System Model (CCSM) model. The model results show a comparable pattern to the database. The global marine N2 fixation rate, diazotrophic biomass and the turnover time of cellular N due to N2 fixation are estimated by accommodating the database and the modeling results.
Speaker: Yawei Luo, Marine Chemistry & Geochemistry
Time: 8:45 a.m.
Location: Ballroom J

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Three-Dimensional Ds Analysis Of Stirring In An Overturning Eddy Circulation
Stirring and mixing in the ocean involves stretching, folding and filamentation of fluid elements. Dynamical systems provides for a very helpful Lagrangian analysis of these processes, one that has been applied successfully to horizontally two-dimensional flow fields. The analysis centers on the calculation of hyperbolic trajectories and their stable and unstable manifolds: so-called Lagrangian Coherent Structures. The analysis applies in situations where the vertical velocity is weak. Our work explores three-dimensional stirring in cases where the vertical velocity is substantial. As a model we use the classical ‘rotating can’ flow, which has a spiraling overturning circulation typical of many ocean eddies. We calculate the three dimensional extensions of stable and unstable manifolds; these form a Lagrangian template for stirring. Chaotic stirring is found in certain regions of the flow field. We compare different methodologies for calculation of the Lagrangian coherent structures and for quantification of the stirring rates.
Speaker: Lawrence Pratt, Physical Oceanography
Time: 9:30 a.m.
Location: Ballroom C

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Structure, Properties, And Heat Content Of Eddies In The Southeast Pacific Ocean
The southeast Pacific (SEP) requires an input of cold water to balance solar heating. One potential source is the offshore transport of cool, coastal waters by eddies. In this study, a variety of observations were used to estimate the effect of eddy transport on upper-ocean temperature in the SEP. Data from the VOCALS-REx field program were used to characterize eddy structure. Cyclonic (anticyclonic) eddies possessed shoaling (depressed) isopycnals, shallow (deep) salinity minimum layers, and high (low) stratification beneath the mixed layer. An intensively surveyed cyclonic eddy had a salty and highly stratified anomaly along the 26.5 kg m-3 isopycnal. The net temperature anomaly of the eddy was negative, including an anomaly of -1oC at 100m depth. A relationship between sea level anomaly and upper-ocean temperature was sought in VOCALS-REx profiles, Argo profiles, drifter observations, and satellite fields. In all of the data, cyclonic eddies were associated with significantly colder temperatures than anticyclonic eddies. Because the eddies had opposite temperature anomalies and occurred at similar frequencies, transport within eddy cores likely has no significant effect on upper-ocean temperature in the SEP.

Speaker: James Holte, Physical Oceanography
Time: 9:45 a.m.
Location: Ballroom H

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Some New Perspectives On Eighteen Degree Water Formation
Evolving ideas of Eighteen Degree Water (EDW) formation will be discussed including two quite different hypotheses on its formation by Worthington and Warren. Worthington’s concept of EDW formation was that it represented a shallow type of mean meridional overturning in the NW Atlantic in which tropical/subtropical characteristics of the near surface waters of the northeasterly-flowing Gulf Stream (GS) were transformed by intense air-sea exchange and returned southwards as a colder, denser water mass. Warren argued that since annual mean heat losses in the region occupied by EDW to the south of the GS were small, EDW was merely renewed locally with advection being unimportant. A recently completed field study of EDW (CLIMODE) is indicating that EDW formation within a given winter can have at least two different dominant physics and distinct locations: one type formed in the Sargasso Sea, largely away from the strong flows of the GS where 1D physics may apply, and a second type formed along the southern flank of the GS, in a region where the background vorticity of the flow and cross-frontal mixing plays a key role in the convective formation process. Because the latter process occurs within the GS frontal zone, cross-frontal fluxes of heat and salt can play a significant role in the GS mode of EDW formation, and impart different water mass characteristics compared to the EDW formed away from the GS in the Sargasso Sea.

Speaker: Terry Joyce, Physical Oceanography

Time: 10:30 a.m.
Location: Ballroom J

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Local Oceanic Thermal Response To Atmospheric Forcing: The Gulf Stream Region
The dominance of the Gulf Stream (GS) in the local heat balance is observed in an hourly 14-month record of unprecedented surface mooring measurements from November 2005 to January 2007. Instrumentation on the buoy provided a high quality record of air-sea exchanges of momentum, heat, and freshwater flux; and oceanographic sensors recorded the upper ocean variability in the upper 600 m. The mooring was at times south of the GS and at other times north of the GS. Our intent is to isolate the local oceanic response to the atmosphere from the advective variability of the GS. A one-dimensional heat budget analysis indicates that the magnitude of the advective contribution to the heat budget is one order of magnitude larger than that associated with atmospheric forcing when south of the GS and on the same order of magnitude as the atmospheric forcing when north of the GS. Through an EOF analysis, the impact of GS and atmospheric forcing are decomposed, allowing the linear local oceanic thermal response to be isolated. This linear air-sea interaction is particularly prominent during the periods of active cold air outbreaks and sustained heating. Case studies of the summer detail the oceanic response to atmospheric forcing in the GS region.

Speaker: Xujing Jia Davis, Physical Oceanography

Time: 11:15 a.m.
Location: Ballroom J

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Turbulence-Mediated Settlement Responses In Larval Oyster Crassostrea Virginica
The settlement of competent larvae to the seafloor is an important transition in the life history of the eastern oyster (Crassostrea virginica), representing a shift from the larval pelagic to adult benthic stage. Settlement is thus the final stage of larval dispersal, and understanding how oyster larvae disperse and settle in suitable habitats is important for design of marine protected areas and our expectations of how coastal anthropogenic influences will affect this commercially important species. Despite its obvious importance, the cues that induce oyster settlement are poorly understood. We hypothesize that increased turbulence levels induce a settlement (downward vertical velocity) response in competent larval oysters, as it indicates the potential presence of nearby shallow benthic habitats. In this talk, we present experimental population-level swimming responses resulting from increasing turbulence levels in an oscillating-grid tank, isolated from the flow field using particle imaging velocimetry, and propose mechanisms by which larval oysters sense changing turbulence levels in a flow field.
Speaker: Jeanette Wheeler, Biology
Time: 11:00 a.m.
Location: Ballroom E

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A Winter Expedition To Explore The Biological And Physical Conditions Of The Bering, Chukchi, And Southern Beaufort Seas
Our understanding of seasonality, particularly winter conditions, in the Arctic is severely limited. This lack of knowledge has compromised our ability to model and to predict Arctic ecosystems, knowledge critical to our efforts to understand the potential impacts of ongoing climate change. In November-December 2011 we will be conducting a cruise on the USCGC Healy to the to the Bering, Chukchi, and Beaufort Seas. We have identified a set of key transects in the various cross-shelf-slope regimes along which we will conduct physical (hydrography, circulation), chemical (nutrients, dissolved organic matter), and biological (zooplankton, microzooplankton, chlorophyll, marine bird) sampling. Our objectives include describing hydrography, circulation, and aspects of the planktonic, nutrient, and dissolved organic matter environments, identifying the overwintering habitat of Calanus spp. and overwintering strategies of phytoplankton, determining the condition and activity (respiration) of Calanus spp., euphausiids, bacteria, and phytoplankton, and quantifying the course- and fine-scale vertical distributions of plankton and particles in relation to the vertical structure of the water column. Here we present preliminary findings on the hydrography and aspects of the biology from the winter cruise.

Speaker: Carin Ashjian, Biology

Time: 11:45 a.m.
Location: Ballroom F

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A Comparison Of North Pacific And North Atlantic Subtropical Mode Waters In A Climatologically-Forced Model
Subtropical mode water (STMW), a water mass with homogeneous temperature and density and low potential vorticity, is formed in the subtropical gyres of both the North Pacific and North Atlantic Oceans. Eighteen Degree Water (EDW) in the Atlantic and North Pacific Subtropical Mode Water (NPSTMW) in the Pacific have many similarities, including the basic formation processes and physical characteristics. This analysis compares properties and intrinsic oceanic variability of EDW and NPSTMW, within the framework of a high resolution model with climatological atmospheric forcing. Interannual variability is evident in the volume and characteristics of EDW and NPSTMW, but the magnitude of variability is small. The most significant differences are found in the average ages. Circulation patterns lead to a higher average age in the North Atlantic, as EDW is more likely to be advected away from the formation region and remain subducted in the North Atlantic, while NPSTMW is more likely to be reventilated the following winter in the North Pacific. Connections with western boundary current variability are explored.
Speaker: Elizabeth Douglass
Time: 2:00 p.m.
Location: Ballroom J


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Nitrite Residence Times In The Primary And Secondary Nitrite Maxima In The Eastern Tropical Pacific: Insights From The Oxygen Isotopic Composition
Nitrite is a central intermediate in the marine nitrogen cycle, and it is generally held in low concentrations in the ocean. However, nitrite accumulates at the base of the euphotic zone (primary nitrite maximum) and in the center of oxygen deficient zones (ODZ’s) in the secondary nitrite maximum. Here we introduce the idea of using static measurements of nitrite oxygen (O) isotope signatures to quantify the rate of nitrite turnover. Three controlling factors were examined and used to estimate the residence time of nitrite. The oxygen isotopic composition of biologically produced nitrite was estimated using cultures of AOA and AOB, as well as natural seawater communities. Next, the rate and equilibrium isotope effect of abiotic O isotope exchange between nitrite and water were determined at a range of pH and temperatures relevant to seawater. These parameters, together with the isotope effects for nitrite oxidation and reduction were used to estimate the residence times of nitrite in the in the primary and secondary nitrite maxima in the Costa Rica Upwelling Dome and off the coast of Peru.
Speaker: Carly Buchwald, Marine Chemistry & Geochemistry

Time: 3:45 p.m.
Location: Ballroom A

 

 

 

 




 

 

 

 

Last updated: February 9, 2012