Lecturer: Fiammetto Straneo
Affiliation: Woods Hole Oceanographic Institution
Title: Glaciers on the loose: navigating the perilous waters of ice sheet-ocean interactions and interdisciplinary science
Session #: Society Award Lectures
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Collapsing ice shelves and increased iceberg calving reflect the widespread speed up of glaciers in Greenland and Antarctica that, over the last two decades, has tripled the contribution of ice sheets to sea level rise. The rapidity of these changes has come as a surprise, revealing major gaps in our understanding of how ice sheets respond to a changing climate. Recently, increased melting under floating ice shelves and at the edge of marine-terminating glaciers, associated with warming ocean waters, has emerged as the trigger for glacier speed up, making ice sheet-ocean interactions a scientific priority underlying efforts to improve predictions of climate change and sea level rise. This is a challenging task because it requires collaboration across multiple disciplines, developing new technologies, and coupling ice sheet and ocean models. This lecture focuses on advances in our understanding of these changes based on observations at the edge of massive calving glaciers in iceberg-choked fjords in Greenland using helicopters, icebreakers, fishing vessels, and autonomous vehicles. Here, melting is caused by intrusions of warm, subtropical waters into the fjords and enhanced by muddy plumes of surface melt released hundreds of meters below sea level. Progress in this emerging field of glacier/ocean interactions has only been possible thanks to a community-wide effort and exemplifies how the nature and scale of the complex problems facing earth scientists today require an inclusive, collaborative, and interdisciplinary approach that is fundamentally different from the more traditional, competition-based culture in which so many of us are accustomed to working.
Lecturer: Steve Emerson
Affiliation: University of Washington
Title: Evaluating the Ocean’s Biological Carbon Pump
Session #: OS027-O
Video (requires AGU login)
The flux of biologically-produced organic carbon from the surface ocean (the biological pump) plays an important role in maintaining the pCO2 of the atmosphere and the oxygen content within the ocean interior. Evaluating this flux and the mechanisms controlling it are necessary to determine marine carbon cycle feedback to climate change. The three primary methods for determining the biological pump: field measurements, satellite remote sensing, and global climate models suggest different geographic distributions of the flux. The accuracy of model and remote sensing results can be judged against field measurements with the assumption that annual net community production (ANCP) is equal to biological carbon export on time scales of a year or more. Three time-series test cases comparing: satellite-derived carbon export, ANCP determined from oxygen and inorganic carbon mass balances, and sediment trap fluxes, demonstrate the complexities of interpreting satellite data. Field determinations indicate much less geographic variability of the biological pump than satellite-derived fluxes, but annual measurements are not presently sufficient in number or geographic distribution to provide credible calibration. One approach for expanding the number of field estimates of the biological pump is to follow decades of oxygen mass balance studies at ocean time-series stations in which ANCP has been stoichiometrically related to annual net biological oxygen production calculated from models of time-series O2 measurements. Unmanned platforms provide a feasible, affordable method for increasing the number of oxygen time-series locations. About ten percent of the profiling floats of the Argo program have oxygen sensors, but until recently the accuracy of O2 measurements has not been sufficient to determine the air-sea oxygen flux, which is the major term in the upper ocean mass balance. Recent in situ calibration methods for O2 sensors suggest it is now feasible to measure accurate oxygen concentrations that can be used to determine the net annual biological oxygen production, and hence the biological carbon pump, in a wide variety of productivity regimens of the world’s oceans.
Lecturer: Dennis Hansell
Affiliation: University of Miami, USA
Title:Dissolved Organic Matter in the Ocean Carbon Cycle
Session #: 176
Twenty-five years ago, dissolved organic matter (DOM) held modest interest to the ocean science community; the few measurements reported suggested a huge yet relatively quiescent pool. As the ocean carbon cycle emerged as a major uncertainty though, and our ignorance of DOM was highlighted, biogeochemical considerations of the pool gained a momentum that continues today. Misdirections were common at that restart as our understanding of DOM’s dynamics was flawed, costing several years and great investment to overcome. This presentation tells the story of complacency, false starts, determination and compelling advances in this burgeoning discipline.
Lecturer: Lisa Levin
Affiliation: Scripps Institution of Oceanography
Title: Deep Margins Under Pressure: Sustaining Biodiversity and Function where Climate Change and Humans Collide
Session #: OS53F-02
The ocean’s deep continental margins (200 – 3000 m) extend for over 150,000 km and cover 45 million square km. Once considered monotonous and of limited environmental value, we now recognize that they are highly heterogeneous and that the diverse habitats and organisms provide key ecological functions and ecosystem services. Driven by increasing CO2 in the atmosphere, continental slopes are experiencing rapid changes in temperature, oxygen and pH. At the same time they are increasingly exploited for their fisheries, energy and mineral resources. This talk will highlight natural- and climate-change induced hypoxia, acidification and warming on upwelling margins. Natural variations in space and time provide lessons about the evolutionary and ecological responses of animals, communities and ecosystems to individual and multiple stressors. We ask, to what extent do they foretell the future? The overprint of stress from climate change is likely to increase ecosystem vulnerability to human disturbance from oil and gas extraction, fishing and minerals mining, with threats to biodiversity and lowered resilience. These challenges demand a global commitment to improved stewardship of deep-ocean ecosystems and resources. Sustaining the integrity of the deep ocean will require integration of oceanography, biodiversity and conservation science, technology, informatics, economics, policy, law and communication, as well as engagement of stakeholders.
Lecturer: Debbie Steinberg
Affiliation: Virginia Institute of Marine Science
Title: Long-term Changes in the Role of Zooplankton in Ocean Biogeochemical Processes
Session #: 039
Zooplankton play an integral role in the cycling of elements in the sea through their grazing and metabolism. Zooplankton time series reflecting climate or other environmentally-influenced changes in zooplankton biomass and community structure can be used to determine associated changes in biogeochemical cycling, and to predict future changes. Analysis of time series from diverse environments, including the Bermuda Atlantic Time-series Study and the Palmer Antarctica Long-Term Ecological Research program, indicates long-term changes in zooplankton export processes, such as fecal pellet production and diel vertical migration. These changes can have significant effects on the magnitude of the biological pump, which regulates in part atmospheric carbon dioxide and hence can impact climate. Changes in zooplankton community structure also affects the quality and quantity of dissolved inorganic and organic matter they produce, which in turn can affect microbial communities. The role of some major taxa (common to both ecosystems is the significance of gelatinous zooplankton– salp blooms, to export), and process rates in major habitats (mesopelagic zone) are still needed to better incorporate the role of zooplankton into predictive biogeochemical models.
Lecturer: Charles Eriksen
Affiliation: School of Oceanography, University of Washington
Title: The Autonomous Revolution: Transforming Ocean Observation with Mobile Platforms
Session #: OS13H-01
The development and use of high endurance autonomous vehicles is changing the nature of ocean observation. The ocean’s description historically is based on ship observations, but automatic means have contributed increasingly over the last half century. First fixed, then orbiting, and now fully mobile platforms contribute to a growing data stream. Autonomous vehicles, once restricted to observing over the course of a day, now have endurances of months or years. These high endurance vehicles tend to be less encumbered by traditional constraints associated with access to the sea. Recent advances portend full-depth coverage of the deep ocean in autonomous vehicle missions lasting a year or more with basin-wide range.
Lecturer: Robert Anderson
Affiliation: Lamont-Doherty Earth Observatory
Title: Wind-Driven Upwelling in the Southern Ocean, Atmospheric CO2, and the End of the Last Ice Age
Session #: IT24C-01
Beginning with a review of recently-published evidence, I will propose that changes in the Southern Hemisphere westerlies, forced by extremely cold “stadial” events in the North Atlantic Ocean, were responsible for increased upwelling in the Southern Ocean, warming of Antarctica, and rising atmospheric CO2 during the termination of the last ice age. Evidence will then be presented that similar north-south teleconnections occurred throughout the last glacial cycle, beginning with the end of the Eemian (the period of maximum warmth during the last interglacial). Thus, large Northern Hemisphere ice sheets are not a prerequisite for the north-south teleconnections associated with these abrupt climate events. Finally, I will propose that North Atlantic stadial conditions of extended duration represent an essential element in the termination of an ice age. Stadial conditions of long duration are necessary to raise atmospheric CO2 above a threshold level high enough to sustain warm interglacial conditions globally.
Lecturer: Rana Fine
Affiliation: Rosensteil School, University of Miami
Title: Chlorofluorocarbons: The Oceans’ Inadvertent Canary
Session #: OS42A-01
The phased-out chlorofluorocarbons have been powerful tools in understanding climate-related oceanic processes. About 1% of the CFCs released over the last century are stable compounds in the Earth’s oceans. Like bomb tritium, CFCs are transient tracers. They add a “time stamp” to water masses. CFC derived ages are used to calculate rates of biogeochemical processes – including inventories of anthropogenic CO2 and denitrification rates. CFC data are utilized in determining rates of subduction, mixing, and water mass formation. They have aided in identification of new circulation pathways, and in validating oceanic circulation models. We also focus on the application of CFCs to identify changes in ocean ventilation at thermocline and intermediate levels – on decadal time scales. And we will examine how CFCs are employed today in the deep meridional overturning circulation – a major element of the Earth’s climate system.
Lecturer: Victoria Fabry
Affiliation: California State University, San Marcos
Title: Ocean Acidification: Hunamkind’s Global Geochemical Experiment with Uncertain Ecological Consequences
Session #: 201
Oceanic uptake of anthropogenic CO2 is altering the seawater chemistry and can have significant impacts on marine biota and ecological processes. The average pH of surface oceans has dropped by 0.1 units since the industrial revolution and, if carbon dioxide emissions continue unabated, will drop another 0.2 to 0.4 units by 2100. Elevated pCO2 is driving the shoaling of the CaCO3 saturation horizon in many regions, particularly in high latitudes and areas that intersect with pronounced hypoxic zones. As the seawater chemistry changes, many calcifying organisms will be adversely impacted, which could lead to decreased biodiversity and cascading effects through marine systems. Few data on the consequences of ocean acidification are available for many organisms, processes other than calcification, and for coastal regions, which generally are not well-represented in global models. The small number of studies at climate-relevant pCO2 values presently provides poor predictive ability to quantify future impacts to food webs and other ecosystem processes. Suggestions for future research will be presented, based on regions, taxa, and processes believed to be most vulnerable to ocean acidification over seasonal to centennial timescales.
Lecturer: Edouard Bard
Affiliation: College de France
Title: The Last Deglaciation as a Test Bench for Studying the Mysteries of Ocean Evolution
Session #: OS23F-01
In contrast with the last few millennia that are characterized by a rather stable climate, the period between 21000 and 6000 years before present experienced a complete reorganization of all climate compartments, e.g. atmosphere, ice sheets and ocean, together with their associated ecosystems and biogeochemical cycles. This period of first-order changes is fascinating for climatologists, since it allows them to study switches between equilibrium modes and transient variations at various spatial and temporal time scales. The last deglaciation is still a great source of scientific inspiration and remains a period full of interesting questions for the entire scientific community. Although several paleoclimatic and paleoceanographic events representing first-order changes have been known for many years (e.g. famous events such as Heinrich #1, Bolling, MWP1A, Allerod, Younger Dryas, 8.2K -), it is only recently that dating has become sufficiently accurate and precise to allow meaningful comparisons with model simulations performed in a transient mode. Indeed, significant progress has been made in geochronology for this period by investigating annually-laminated sediments and improving radiochronological tools based on uranium series isotopes and radiocarbon. In addition, paleoceanographic records covering the last deglaciation are now available at a global scale, including tropical sites that are very remote from the main center of variation linked to the melting of former ice- sheets on each side of the North-Atlantic basin. To illustrate the progress in this research field, I will first review what we know about the sea-level rise during deglaciation based on coral reefs, and then go on to consider the associated changes in the Atlantic, Pacific and Indian oceans, both for the surface waters and deeper layers. Records from marginal seas, coastal zones and river mouths will also serve to illustrate the complex linkage between sea level and paleoceanographic changes.
Lecturer: Barbara Hickey
Affiliation: School of Oceanography, University of Washington
Title: Freshwater Influences on Coastal Productivity and Harmful Algal Blooms
Session #: OS32Q-01
An appreciation for the effects of freshwater plumes in the coastal zone, often overlooked in our community’s enthusiasm for the more obvious effects of winds, has been emerging in recent papers and presentations: clearly, freshwater effects can exert a dominant control on plankton growth and variability in some instances. For example, one paper has shown that annually-averaged coastal chlorophyll as well as higher trophic level productivity along the North American west coast does not appear to be related to the strength of upwelling-favorable winds-freshwater effects are invoked as one explanation for the relatively high chlorophyll and productivity off the Washington and British Columbia coasts. Another paper attributes the growth and rapid spread of toxic algal blooms in the Gulf of Maine in 2005 to the existence of a narrow freshwater-forced coastal current. In this lecture data from recent and ongoing interdisciplinary studies are used to explore new ideas on the effects of freshwater plumes on regional marine ecosystems. In particular, impacts on regional nutrient supply, local production and enhanced or inhibited transport of coastal plankton blooms will be discussed. Although freshwater nutrient input in some regions is associated with a high nutrient load, coastal freshwater plumes derived from many larger North American rivers are relatively devoid of macronutrients-nutrients from watersheds are utilized in the estuary before the water emerges onto the shelf. Even in this case, freshwater plumes may play a critical role in macronutrient delivery to the continental shelf-for example, nutrient-rich upwelled shelf water can be entrained into an outgoing freshwater plume as the water exits the estuary. This mechanism is particularly important at the mouth of the Columbia River, usually resulting in a persistent phytoplankton bloom within the river plume itself. Farther north, nutrient-rich upwelled shelf/slope water is pulled into the Strait of Juan de Fuca at depth to compensate estuarine outflow, then mixed upward into the outflowing freshwater layer. This process provides a spatially extensive (several 10’s of kilometers wide and long) nutrient source for the coastal region that persists whether or not local upwelling is occurring along the coast (such as in summer 2005). Nutrients from this source can be advected regionally 100’s of kilometers along the shelf, potentially providing upwelling source waters over a very broad area. Additional mixing of nutrients into surface layers over the shelf may occur via entrainment when a freshwater-driven coastal current flows over underlying nutrient-rich shelf water. Freshwater plumes can also be critical to the maintenance and/or distribution of harmful algal blooms. The effect on a particular bloom depends on whether a bloom is located seaward, shoreward or within a river plume and on whether vertical migration is possible (such as in Alexandrium fundyense). For example, it has been hypothesized that the density front on the seaward side of the Columbia plume may inhibit blooms of toxic Pseudo-nitzschia generated offshore from ever arriving at the coast where they could be ingested by razor clams. On the other hand, as shown in the Gulf of Maine, toxic blooms entrained into a coastal freshwater current may be transported more quickly to other sites because alongshore velocities are usually much greater in such features than in currents driven by wind alone. In some instances plankton blooms may be trapped near the coast on the inshore side of a plume, extending residence time in the coastal zone, thus accumulating chlorophyll (perhaps a regional ecosystem benefit) or extending contact time between shellfish and toxic blooms (not a beneficial result overall).
Lecturer: Alice L. Alldredge
Affiliation: Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara
Title: Marine Snow and Gels: Hot Spots of Biogeochemical Cycling, Biological Activity, and Sedimentation in the Sea
Session #: OS31B-01
Video (scroll down to Wednesday)
Much of the organic carbon sequestered in the deep sea and ocean bottom sediments as relatively rare, large detrital particles generically known as marine snow. Because they are enriched in organic matter, microbes, and nutrients, these large particles also serve as hot spots for biological and chemical process in the water column. Recent evidence reveals that abundant carbohydrate gel particles in the ocean, formed from the dissolved exudates of phytoplankton and bacteria, are intricately involved in the formation of marine snow. These discoveries are changing the way we conceptualize the pelagic zone on small scales. We no longer imagine seawater as a relatively homogeneous fluid in which float a spectrum of dispersed molecules, particles, and organisms, but instead see it as a rich hydrated matrix of transparent organic gels, detritus, and cob-web like surfaces which provide microscale physical, chemical, and biological structure. This talk will focus on the origins, fate, and significance of marine snow and gels in the sea, including their role in carbon cycling, sedimentation and carbon flux , food webs, and chemical and biological transformation.
Lecturer: Lawrence Mysak
Affiliation: McGill University, Dept. of Atmospheric and Oceanic Sciences
Title: The Oceans and Climate: Earth System Models and Their Application to Abrupt and Not-so-abrupt Changes
Session #: OS32N-01
During the past decade, a new class of geosphere-biosphere models of the Earth system has been developed for investigating long-term as well as abrupt climate changes, both past and future. These models, known as Earth system Models of Intermediate Complexity or EMICs (Claussen et al., 2002, Climate Dynamics), have been used extensively, for example, in scoping out future climate change scenarios, estimating the effects on climate of deforestation and afforestation, and exploring the mechanisms for decadal-to millennial scale variability. This 2004 Sverdrup Lecture will focus on the role of the ocean thermohaline circulation (THC) in several of these phenomena. Results will be shown from a number of EMIC modelling groups, including that at McGill. In particular, simulations will be presented of the THC collapse during very cold climates, millennial-scale Dansgaard-Oeschger cycles, the last glacial inception, and the initiation of the next ice age.
Lecturer: William Jenkins
Affiliation: Woods Hole Oceanographic Institution
Title: What Oceanographers are Learning From Transient Tracers
Session #: OS11F-01
A number of substances have been released into the environment on a global scale from humankind’s activities. Observation of the passage of these tracers into and through the oceans is providing us with a remarkable opportunity to examine the rates, pathways, and mechanics by which material fluxes occur. Such information is critical to our understanding of how the ocean participates in the grand biogeochemical cycles, the earth system, and long-term climate regulation. This understanding is important for forecasting and possibly ameliorating natural and anthropogenic global change. How we extract this information from the evolving distributions of transient tracers is in itself an unfolding story. In general, there are three basic but related approaches that are used. The first involves “pathway visualization” whereby the observed distributions highlight the routes whereby these tracers propagate into the ocean interior. Observations from the WOCE and other programs provide us with compelling pictures of transient tracer distributions never before seen. This visualization provides geographic information about where the tracers have reached, and within some broad time-scale. A second approach involves the diagnosis of various transport properties directly from the observed fields, whether by regression calculations, inversions, or Green function estimates. Such calculations often lead to some estimate of the flow field, such as advection or turbulent mixing rates; or to a measure of inherent biogeochemical reactivity, such as adsorption, consumption, or particulate transport. A related approach involves the direct calculation of “tracer ages”, which provide some measure of the ventilation time-scale of the water masses. Such a calculation, however, has subtle issues associated with it. Finally, comparison of observed tracer fields with prognostic model calculations has been used for evaluation and intercomparison of model performance. So what are we learning from these observations? Firstly, we are learning how to extract the information from the observations, and gaining a sense of the limitations of the tools we use. Secondly, we are able to combine tracer age information with other tracers and geostrophic constraints to estimate absolute velocities, along with mixing and subduction rates in a subtropical gyre. Thirdly, we can accurately calculate oxygen consumption rates, and from this, export production and carbon transport on large space and time scales. Such information is valuable to constraining and modeling large-scale biogeochemical fluxes. In this lecture, I present examples of these approaches, with emphasis on one specific system: tritium and its inert daughter helium-3.
Lecturer: Jorge Sarmiento
Title: The Ocean Carbon Cycle: How Well Do We Understand It?
Lecturer: Cindy Lee
Affiliation: SUNY StonyBrook, Marine Science Research Center
Title: Particle Fluxes in the Sea
Session #: OS12G-01
Lecturer: Michael McPhaden
Affiliation: NOAA / PMEL
Title: The 1997-98 El Nino in Review: Lessons and Challenges for Climate Research
Session #: OS32F-01
The 1997-98 El Nino, one of the strongest on record, has been called The Climate Event of the Century. The event unfolded rapidly in the tropical Pacific beginning in early 1997, and by July 1997 sea surface temperature anomalies in the eastern Pacific reached historic highs. The subsequent evolution of this event through mid-1998 led to spectacular impacts on global weather variability and Pacific marine ecosystems. This presentation reviews recent progress in climate observations and predictions as exemplified by the 1997-98 El Nino event. A major contributor to this progress has been the development of an ocean observing system comprised of complementary satellite and in situ measurements. The data from this observing system were used to initialize and validate model forecasts of the 1997-98 event, and to provide high definition monitoring of the event in real-time. The observations also provided new insights into the dynamics of coupled ocean-atmosphere interactions in the tropical Pacific, and highlighted issues concerning the relationship of El Nino to both shorter time scales associated with the intraseasonal Madden and Julian Oscillation, and longer time scales associated with interdecadal variability and global warming. Thus, while the 1997-98 El Nino serves to emphasize fundamental advances made in seasonal-to-interannual climate research in the past 10-15 years, it also raises new challenging reseach questions for the future.
Lecturer: Paul Quay
Title: Is a Balanced Carbon Budget Measurable in the Surface Ocean?
Session #: OS42D-01
A substantial effort has been expended during the JGOFS program to measure the magnitude of biological carbon production and export rates in the surface ocean. The major carbon fluxes measured typically include the vertical settling of particulate organic carbon (POC), primary production and new (exportable) production. Carbon fluxes associated with the export rate of dissolved organic carbon (DOC), the advective and diffusive transport of dissolved inorganic carbon (DIC) and the air-sea CO2 exchange rate have been derived indirectly, for example, by coupling advection or gas transfer rates with measured concentration gradients. Most of the carbon flux estimates have substantial uncertainties. The likelihood that coordinated carbon flux measurements, like those made during a JGOFS process study, yield a balanced surface carbon budget will be quantitatively examined. Specifically DIC and organic carbon budgets will be constructed for the equatorial Pacific based on carbon fluxes measured during the JGOFS-EqPac program. Issues raised by this examination include the discrepancy between POC flux estimates and measured new production rates and the less important role of DOC (versus POC) export. The analysis finds that there is a low probability (1 in 3 chance) that a balanced surface carbon budget can be measured in the equatorial Pacific given the uncertainties of the individual flux estimates. This raises the question of whether a carbon balance is a useful test of individual carbon flux estimates. The most pressing uncertainties in our ability to determine a surface carbon balance will be discussed.
Lecturer: Michael McCartney
Affiliation: Woods Hole Oceanographic Institution
Title: The North Atlantic Ocean in Climate and Climate Change
Lecturer: Margaret Delaney
Title: Paleoceanography: State of Art and the Future