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COMPASS Wednesday

Combined OCE MPO ATM Seminar Series

FALL 2021
Wednesdays at 3:00 pm, Seminar Room SLAB 103 / Virtual SLAB 103
(unless stated otherwise)

Aug 25: Nektaria Ntaganou
Department of Ocean Sciences, RSMAS
(one-hour MPO student seminar)

Loop Current System Evolution:
Topographic Controls and 
the Influence of Caribbean Eddies
Zoom Recording Available at COMPASS ON DEMAND

The Loop Current governs the mesoscale circulation in the Gulf of Mexico and connects the Caribbean Sea to the Atlantic Ocean. The Loop Current evolution is influenced by various factors, including topographic controls, the rich eddy field of the region, and flow exchange through the Yucatan Strait with the neighboring Caribbean Sea. These factors contribute to the complexity of the Loop Current and, as a result, to the limitations in the predictability of the system. The focus of this study is on the evolution of the Loop Current under a) the interaction with the topography of the West Florida Shelf and b) the influence of coherent eddy fluxes originating in the Caribbean Sea. The first topic is approached by conducting realistic and semi-idealized numerical simulations to investigate the topographic interactionsThe results suggest that the evolution of the Loop Current into the Gulf of Mexico is influenced by lower layer dynamical processes associated with the bottom topography in the southwestern West Florida Shelf and western Straits of FloridaThe second topic is examined based on objective metrics to evaluate eddy coherence in the Caribbean Sea and quantify the evolution of coherent Caribbean eddies through Yucatan. Results show that a) the flow through the Yucatan Strait that is attributed to a) coherent anticyclonic potential vorticity fluxes and b) the net coherent anticyclonic volume between the Caribbean Sea and the Gulf of Mexico, facilitates Loop Current Eddy growth and detachments. The findings have important implications for advancing the understanding and reliable predictions of the Loop Current, highlighting the role of interaction with shelf slope and inter-basin exchange through a strait. The related dynamics are also important for understanding and predicting the physical connectivity processes between the Gulf of Mexico and the Caribbean Sea. 

Sep 01: Simge Bilgen
Department of Atmospheric Sciences, RSMAS
(one-hour MPO student seminar)

The Role of Ocean Eddies in Climate Variability and Change in the Southern Ocean
Zoom Recording Available at COMPASS ON DEMAND

Over the last few decades, the Southern Ocean (SO) around Antarctica has been cooling, in striking contrast to the rapid warming observed in the Arctic. These negative sea surface temperature trends in the SO are, naively, at odds with greenhouse-gas induced warming over much of the World’s Oceans in recent decades. The trends in the SO are not reproduced by the historical simulations with state-of-the-art coupled models because of the models' deficiencies introduced by, as hypothesized here, missing ocean dynamics associated with meso-scale processes. We show here results that suggest resolved ocean meso-scale processes may be an integral part of observed trends in the SO, and we propose a research strategy to better understand how ocean eddies affect climate variability and change in the SO. The study seeks to understand the delayed warming from a process perspective with specific attend to ocean meso-scale processes, and intend to answer the following questions: 1) How do meso-scale processes affect CO2 response in the Southern Ocean;  2) What changes to the Southern Hemisphere ocean circulation have been caused by change in the zonal wind stress; and 3) How do ocean meso-scale processes affect the sea surface temperature response to the Southern Annular Mode on multiple time scales? The main conclusion from the presented suite of experiments is that the parameterized eddies are not able to mimic the nature of the resolved eddy field during greenhouse gas forcing, but are skillful in representing the SO historical temperature trends with observed wind stress.

Sep 08: Dr. Jochen Horstmann
Adjunct Professor, Department of Ocean Sciences, RSMAS /
Institute of Coastal Ocean Dynamics, Helmholtz-Zentrum Hereon, Geesthacht, Germany

Marine Radar Wind and Wave Measurements for Short-Term Forecasts
J. Horstmann, R. Carrasco, J. Seemann, and M. Streßer
Zoom Recording Available at COMPASS ON DEMAND

Offshore wind energy is one of the most important renewable energy sources. In 2020 Europe had a total installed offshore wind capacity of 25 GW, corresponding to about 5,400 wind turbines. For the operation of these turbines, monitoring of the local wind and wave climate is extremely helpful. Marine radars have shown to be a valuable tool for measuring mean wind vectors and spectral wave parameters (e.g. significant wave height and peak period). However, due to the complex nature of the radar modulation transfer function, the determination of surface wind fields and individual waves in space and time are not yet well developed. Coherent marine radars measure in addition to the backscatter intensity the radial velocity of the scatterers, which is strongly related to surface wind, waves and currents. In this presentation, ongoing work on the development of new methodologies to retrieve ocean surface wind as well as individual wave fields will be introduced. These methods utilize the intensity as well as the Doppler information measured by the radar. Results acquired under various wind and wave situations will be shown and compared to in-situ measurements were possible. These measurements will also be utilized to perform short-term (30-60 s) forecasts of wind gusts and individual waves, which could help to improve the predictive control of offshore wind farms as well as aviation operations out at sea.

Sep 15: Dr. Robert Letscher
Earth Sciences & Ocean Process Analysis Laboratory, University of New Hampshire

Non-Redfield Marine Elemental Stoichiometry:
Its Manifestations and Why It Matters
Zoom Recording Available at COMPASS ON DEMAND

Are the oceans turning into deserts? Rising ocean temperatures, surface water stratification, and decreasing vertical inputs of nutrients are predicted to cause an expansion of warm, nutrient depleted ecosystems of the subtropical gyres at the expense of more nutrient rich, colder waters in the latest class of Earth System Model projections. Such an expansion is predicted to negatively affect a triad of key ocean biogeochemical features: lower phytoplankton biomass, lower primary productivity, and lower carbon export (aka the biological carbon pump). Due to the inextricably linked marine carbon, nitrogen, and phosphorus cycles first identified by Alfred Redfield in 1934, these combined effects should decrease the strength of the ocean CO2 sink in the climate system. Thus, the ocean biogeochemical and ecosystem response to climate warming suggests a positive feedback to further accumulations of CO2 in the Earth's atmosphere. However, it is now recognized that phytoplankton communities contain immense diversity and adaptability that could render the ocean biogeochemical response at least partially resilient to global changes through the shifting effects of changes to marine elemental stoichiometry in the future ocean. I will review the current state of the field with regards to understanding these 'non-Redfield' stoichiometry effects as the ocean biogeochemical community moves past the enduring 'Redfield stoichiometry' paradigm of the past 85 years.

Sep 22: Dr. Pedro DiNezio
Atmospheric and Ocean Sciences, University of Colorado Boulder

Extreme Tropical Variability Under Greenhouse Warming
Zoom Recording Available at COMPASS ON DEMAND

Whether tropical climate variability will increase in response to greenhouse warming is highly uncertain, limiting our ability to predict and attribute changing climatic extremes throughout the world. This question remains unanswered because externally-forced changes in modes of tropical variability cannot be ascertained using historical records or model predictions. We overcame these issues by studying changes in modes of variability under a range of past external forcings, validating them against proxy-inferred changes in variability during Earth's geological history. For the Indian Ocean, we discovered a mode active during the last glacial period driving much stronger variability than currently observed. This mode – inactive today – could remerge by mid-century as this ocean develops oceanographic conditions favoring large-scale air-sea interactions. For the Pacific Ocean, changes in mixed layer depth control the occurrence of extreme El Niño via its influence on momentum coupling between winds and ocean currents. Under glacial conditions, a deeper mixed-layer in the central Pacific, disrupts the generation of extreme El Niño, as seen in paleoclimate records. The opposite occurs under greenhouse warming, when extreme El Niño could become more frequent due to a shallower mixed layer. These predictions, supported by past changes, reveal a heightened risk of increasing climatic extremes exacerbating the impacts of global warming over a large part of the planet.

Sep 29: Yu Gao
Department of Ocean Sciences, RSMAS
(one-hour MPO student seminar)

Mesoscale Air-Sea Coupling and Mixed Layer Variability
in the Southern Ocean
Zoom Recording Available at COMPASS ON DEMAND

We study the mesoscale air-sea coupling and mixed layer depth (MLD) variability in the Southern Ocean. First, we analyze the role of mesoscale heat advection in the Southern Ocean mixed layer heat budget using a regional high-resolution coupled model. We conclude that the oceanic heat advection creates SST anomalies, while the atmospheric turbulent heat fluxes dampen these anomalies. The effects of atmospheric forcing on the ocean are modulated by the MLD variability. Second, we analyze the variability of the MLD using the upper-ocean buoyancy budget in the same regional model. The buoyancy budget analysis shows that the atmospheric forcing and mixing induces the variability in MLD, while the oceanic advection counteracts these effects of the atmospheric forcing. In order to further examine how the mesoscale air-sea coupling affects the MLD variability, we also analyze two sensitivity experiments: the Smooth-Fluxes and Smooth-Winds experiments. Overall, MLD variabilities are enhanced due to the lack of atmospheric damping in both experiments. The spatial change in MLD variability is potentially related to the shift of the jet position in the sensitivity experiments. Third, we analyze how the mesoscale air-sea coupling can affect the MLD variability in global climate simulations. The preliminary results show that air-sea feedback leads to shallower MLD and suppresses the MLD variability. The main conclusion of this study is that intrinsic ocean variabilities control mesoscale airsea coupling, and significantly affects the MLD variability in the Southern Ocean.

Oct 06: Dr. Henry Potter
Department of Oceanography, Texas A&M University, College Station

Upper Ocean Temperature Variability in the Gulf of Mexico
With Implications for Hurricane Intensity
Zoom Recording Available at COMPASS ON DEMAND

Strong winds in tropical cyclones (TCs) mix the ocean causing cooler water from below the thermocline to be drawn upward, reducing sea surface temperature (SST). This decreases the air-sea temperature difference, limits available heat energy, and impacts TC intensity. Part of TC forecast accuracy therefore depends upon the ability to predict sea surface cooling; however, it is not well understood how underlying ocean conditions contribute to this cooling. Here, ~4400 Argo profiles in the Gulf of Mexico were used in a principal component analysis to identify the modes of variability in upper ocean temperature, and a 1-D mixed layer model was used to determine how the modes respond to surface forcing. It was found that the first two modes explain 75% of the variance in the data with high Mode 1 scores being broadly characterized as having warm SST and deep mixed layer, and Mode 2 as having high SST and a shallow mixed layer. Both modes have distinct seasonal and spatial variability. When subjected to the same model forcing, Mode 1 and Mode 2 characteristic waters with equal tropical cyclone heat potential (TCHP) respond very differently. Mode 2 SST cools faster than Mode 1 with the difference most pronounced at lower wind speeds and when comparing early to late season storms. The results show that using TCHP as a marker for SST response during TC forcing is insufficient because it does not fully capture subsurface ocean thermal structure. This underscores the need for continual subsurface monitoring to accurately initialize the upper ocean in coupled TC models.


Oct 20: Dr. Emanuele Di Lorenzo
Ocean Science and Engineering Program, Georgia Tech

Ocean Visions: Catalyzing Solutions for Ocean & Climate Health
Zoom Recording Available at COMPASS ON DEMAND

The Ocean Visions is an initiative and non-profit that brings together a consortium of US research universities that aim at transforming and accelerating the deployment of science and engineering into practicable, scalable, and equitable ocean solutions in collaboration with impact and acceleration partners. With the launch of the Global Ecosystem for Ocean Solutions Programme under the United Nations Decade for Ocean Sustainable Development, the Ocean Visions is bringing together a multi-sector and multi-disciplinary community to co-design and deploy solutions roadmaps to key ocean and climate challenges. In this talk, I will review some of the advances on developing ocean-based solutions to climate change, with a focus on open ocean carbon dioxide removal, and discuss a recent initiative on developing a shared roadmaps for equitable ocean-climate solutions for coastal communities and cities in the US.

Emanuele Di Lorenzo is Professor and Founding Director of the Program in Ocean Science & Engineering at the Georgia Institute of Technology, and Chairman and Co-Founder of Ocean Visions. He obtained a BS in Marine Environmental Science in 1997 from University of Bologna, a Ph.D. in 2003 from the Scripps Institution of Oceanography and conducted postdoctoral work at University of California Los Angeles from 2003-2004. Di Lorenzo is recognized as a world expert in large and regional-scale Pacific Ocean dynamics and climate. Throughout his career he has served in several leadership role for international organizations such as CLIVAR, US CLIVAR, PICES, and ICES, where he led transdisciplinary efforts to understand the impacts of climate on marine and social-ecological systems. In 2019, through a multi-institutional agreement between Georgia Tech, Stanford, MIT, Scripps, WHOI, Smithsonian, MBARI, UGA, Monterey Bay Aquarium and Georgia Aquarium, Di Lorenzo established the Ocean Visions ( — an effort to transform and accelerate the transfer of science and engineering into solutions for the ocean grand challenges. More recently Di Lorenzo has led the establishment of the Global Ecosystem for Ocean Solutions (GEOS) Programme under the United Nations Decade for Ocean Sustainable Development.

Oct 26 (Tuesday, 2:00 pm): Dr. Ved Chirayath
G. Unger Vetlesen Professor of Earth Sciences / Director, Aircraft Center for Earth Studies (ACES)
Department of Ocean Sciences, RSMAS

Introducing ACES – The Aircraft Center for Earth Studies
Recording Available at COMPASS ON DEMAND

I am delighted to join the RSMAS faculty as the new G. Unger Vetlesen Professor of Earth Sciences and Director of the Aircraft Center for Earth Studies (ACES)! In this seminar, I will introduce my vision for ACES and seek to establish its reputation as a collaborative center and resource for the broader RSMAS community. The ACES position presents a compelling opportunity for me to grow a diverse program aimed at developing, testing, and maturing new airborne, underwater, and satellite technologies and platforms to further research of terrestrial, oceanic, and atmospheric environments. In my present research, I have developed sensing systems that span all three of these disciplines and I would be eager to work with others to design and integrate instrumentation to advance their science goals on airborne platforms. I am bringing eight funded research projects with me to RSMAS and will highlight some of the capabilities and capacity ACES has at present and into the future from fluid lensing & MiDAR remote sensing instruments to a solar electric high-altitude drone to a solar-electric research vessel already developed and integrated at RSMAS. Concurrently, I would like to grow a program in aeronautics with hands-on student training in design, manufacture, and flight testing of airborne platforms and drones, as well as sensing hardware, culminating in participation in the global student solar flight competition. Finally, I would like to translate my experience in growing SmallSat and CubeSat programs at Stanford and NASA  for the past decade to RSMAS. The end goal for many airborne sensing systems is Earth orbit. A CubeSat program at RSMAS spanning faculty with a diverse set of science interests would be game-changing for Earth Science and an invaluable hands-on experience for students. Together, these maturing technologies present promising new ways in which to investigate terrestrial, marine, and aerial systems on Earth, and, ultimately, aid in the search for extraterrestrial life within our solar system and beyond.

Oct 27: Dr. Hilary Close
Department of Ocean Sciences, RSMAS
(Candidate for Promotion and Tenure)

Marine Metabolisms Recorded in Natural Stable Isotopes:
From Microbes to the Global Carbon Cycle

Current climate trends are likely to cause major ecological shifts in the world’s oceans. The effects of such ecosystem change on the marine carbon cycle are under debate, in part due to uncertainties in the relative contribution of microbial versus animal food web processes in the biological carbon pump. Stable isotopes hold promise as long-lived tracers of such processes: Natural variations in the carbon and nitrogen isotope ratios of organic matter can reflect a range of autotrophic and heterotrophic metabolisms. However, these metabolic signatures can be obscured within the complex mixture of living and degraded material that makes up marine organic matter. I will discuss how my lab uses isotopic analyses of individual organic compounds to distinguish specific microbial and animal metabolisms contributing to carbon and nitrogen cycling in environments ranging from the upper water column to seafloor methane seeps. I will highlight our recent progress toward developing a framework by which to quantify the relative contributions of microbes and zooplankton to the global biological carbon pump.

Nov 03: Kelsey Malloy
Department of Atmospheric Sciences, RSMAS
(one-hour ATM student seminar)

Understanding the Summer Asia-North America Teleconnection
and Its Modulation by ENSO: A Tale of Three Models
Zoom Recording Available at COMPASS ON DEMAND

Seasonal forecasts of summer continental United States (CONUS) rainfall have relatively low skill, partly due to a lack of consensus about its sources of predictability. The East Asian monsoon (EAM) can excite a cross-Pacific Rossby wave train, also known as the Asia-North America (ANA) teleconnection. We have analyzed the ANA teleconnection between observations and model simulations from the Community Atmospheric Model, version 5 (CAM5), comparing experiments with prescribed climatological SSTs and prescribed observed SSTs. Observations indicate a statistically significant relationship between a strong EAM and increased probability of positive precipitation anomalies over the U.S. west coast and the Plains-Midwest. The ANA teleconnection and CONUS rainfall patterns are improved in CAM5 experiment with the observed SSTs, suggesting that SST variability is necessary to simulate this teleconnection over CONUS. Distinct ANA patterns are detected between ENSO phases, with the Niña-related patterns in CAM5 disagreeing with observations. Using linear steady-state quasi-geostrophic theory, we conclude that incorrect EAM forcing location greatly contributed to CAM5 biases, and jet stream disparities explained ENSO-related CAM5 biases. Finally, we have compared EAM forcing experiments in different mean states with a simple dry atmospheric general circulation model to isolate the dry atmospheric response from ocean and land-moisture influences. Overall, the ANA pattern is well described by dry dynamics on the seasonal-to-interannual timescale.


Nov 17: Dr. David Ortiz-Suslow
Department of Meteorology, Naval Postgraduate School, Monterey, California

Insights Into Air-Sea Interaction Gained During FLIP's Final Mission
Zoom Recording Available at COMPASS ON DEMAND

In the Fall of 2017, the Coupled Air Sea Processes and Electromagnetic ducting Research (CASPER) project conducted a large-scale air-sea interaction field study in the Southern California Bight. As part of a coordinated effort to characterize the marine atmospheric boundary layer from the oceanic thermal skin to the boundary layer top and inversion, the Floating Instrument Platform (FLIP) was deployed with an extensive compliment of atmosphere and ocean sensing systems. This mission to Southern California would inevitably be the iconic platform's last science mission. This presentation will focus on a subset of the FLIP data collected during CASPER-West, namely the surface layer measurements made from the air-sea interaction mast: a densely instrumented vertical array with overlapping profiles of bulk and perturbation wind, temperature, and humidity from 3 to 16 m above the ocean surface. This is a truly unique dataset and through our analysis we have gleaned key insights into several air-sea interaction processes and mechanisms. The findings from a selection of these studies will be discussed in detail, emphasizing the implications these results have on our understanding and prediction of coupled processes. These studies have only grasped the surface of this rich data set and avenues for further study will be discussed.

Nov 24: NO SEMINAR (Thanksgiving Recess)

Dec 01: Dr. Francisco J. Beron-Vera
Department of Atmospheric Sciences, RSMAS

Geometric Thermal Geofluid Mechanics
Zoom Recording Available at COMPASS ON DEMAND

Driven by growing momentum in two-dimensional geophysical flow modeling, I introduce a general family of "thermal" rotating shallow-water models. The models are capable of accommodating thermodynamic processes, such as those acting in the ocean mixed layer, by allowing buoyancy to vary in horizontal position and time as well as with depth, in a polynomial fashion up to an arbitrary degree. Moreover, the models admit Euler-Poincare variational formulation and possess Lie-Poisson Hamiltonian structure. Such geometric mechanics properties provide solid fundamental support to the theories described with consequences for numerical implementation and the construction of unresolved motion parametrizations. In particular, it is found that stratification halts the development of small-scale filament rollups recently observed in a popular model, which, having vertically homogeneous density, represents a special case of the models presented here. Time permitting I will present an application showing how geometric thermal geofluid mechanics casts new light on Sargassum inundation in the Caribbean Sea.

Dec 08: Dr. Chengfei He
Department of Atmospheric Sciences, RSMAS

Deciphering the Deglacial Evolution of Asian Monsoon
and Its Associated Water Isotope
Recording Available at COMPASS ON DEMAND

The climate change during the last deglaciation is characterized by several abrupt fluctuations, notably the Heinrich Stadial 1 (HS1, ~18-14.5 ka), Bølling-Allerød (BA, 14.5-12.9 ka), and Younger Dryas (YD, 12.9-11.7 ka). These abrupt events as well as long-term climate variability are well preserved in stable water isotope (δ18O) proxy over the globe, which is an invaluable indicator for past temperature and hydroclimate. In particular, a large number of speleothem δ18Ocs discovered across the pan Asian monsoon regions show highly consistent variability during the last deglaciation. However, their evolution mechanism, as well as implications to Asian monsoon, remain highly controversial. To decipher the evolution of water isotope and associated Asian monsoon change, an isotope-enabled Transient Climate Experiment (iTRACE) of the global climate in a state-of-the-art isotope-enabled Earth system model is conducted. The iTRACE successfully reproduces the oxygen-isotope and Asian monsoon evolutions. Accompanied by the homogeneous oxygen isotope signal across the Asian monsoon regions, the monsoon hydroclimate is characterized by a heterogeneous response, with a dipole response in East Asia and an identical response between North China and South Asia. It is revealed that the variability of speleothem δ18Oc is determined by upstream moisture source over the Indian Ocean in summer. The pan-Asian summer monsoon hydroclimate is driven by high-level westerly, low-level monsoon flow, and South Asia-North China teleconnection. Both of them are primarily caused by the change of the Atlantic Meridional Overturning Circulation (AMOC) and solar insolation. Our simulation further identifies a dramatic change of deglacial autumn monsoon in East Asia (EAAM). The magnitude of EAAM anomaly is comparable to the summer monsoon, however, its evolution is independent of stable water isotope signal. The variability of EAAM results from the convergence between anomalous northerly wind and anomalous southerly wind associated with an anticyclone at Western North Pacific, as a response to the slowdown of the AMOC in HS1 and YD.

Dec 09 (Thursday, 11:00 am): Dr. Alan Li
NASA Ames Research Center, Mountain View, California

NASA NeMO-Net – Gamifying & Automating Marine Habitat Mapping
Using Citizen Science & Neural Networks
Recording Available at COMPASS ON DEMAND

Recent advances in machine learning and computer vision have expanded capabilities for benthic habitat mapping through airborne and satellite remote sensing. This is of particularly interest to the marine biology community, as these new technologies can allow the automated processing and analysis of large quantities of collected data, especially within remote regions that are sensitive to anthropomorphic pressures and global climate change. NASA NeMO-Net, the neural multi-modal observation and training network for global coral reef assessment, is an open-source deep convolutional neural network and interactive active learning training software designed specifically to address these issues; its goals are to accurately assess the present and past dynamics of coral reef ecosystems through determination of percent living cover and morphology as well as mapping of spatial distribution. We present here a two-fold approach: 1) an interactive citizen science video game for desktop and iOS devices where users interactively label morphology classifications over mm-scale 3D coral reef imagery captured using diver photomosaic imagery, the UAV enabled NASA FluidCam instrument, and satellite datasets, and 2) the convolutional neural network (CNN) deep learning system that uses the label data collected through the citizen science app to train a classifier that is able to account for discrepancies between data sources, quality, and context to generate semantically segmented maps of shallow marine habitats. For the active learning application, NeMO-Net trains players on domain-specific knowledge through interactive tutorials and periodically checks players’ input against pre-classified coral imagery to gauge their accuracy and utilize in-game mechanics to provide personalized classification training. Players can rate the classifications of other players, unlock rewards and join a global community as they explore and classify coral reefs and other shallow marine environments. NeMO-Net’s convolutional neural network (CNN) models is then used to semantically segment 2D satellite imagery as well as projections of 3D coral reconstructions using the previous user input data as training datasets. In partnering with Mission Blue, the National Oceanic and Atmospheric Admistration (NOAA), and the Living Oceans Foundation (LOF), NeMO-Net leverages an international consortium of subject matter experts to provide both proper training for citizen scientists and the generation of a labeled datasets to ingest into machine learning algorithms for global coral reef identification. Our results, based upon minimally pre-processed WorldView-2 and Planet satellite imagery, show a total accuracy of approximately 85% and 80%, respectively, over 9 classes when trained and tested upon a chain of Fijian islands imaged under highly variable day-to-day spectral inputs.

Alan S. Li received his B.S. in Mechatronics Engineering at the University of Waterloo, Canada, in 2009 and his M.S. and Ph.D. in Aeronautics and Astronautics Engineering at Stanford University, CA, USA in 2011 and 2017, respectively. Since 2016, he has been a Research Engineer at NASA Ames Research Center in Mountain View, CA, within the Laboratory for Advanced Sensing (LAS), Earth Sciences Division. His previous work involves dynamic modeling of satellites, guidance and control, as well as the optimization of satellite scheduling. His research interests include next-generation remote sensing technologies and machine learning as applied to remote sensing datasets. Dr. Li is a IEEE, AIAA, and American Geophysical Union member, and was awarded the Outstanding Paper Award for Young Scientists at the 41st COSPAR Scientific Assembly in 2016.

Dec 09 (Thursday, 2:00 pm): Dr. Heidi Hirsh
NOAA-CIMAS, Miami / Mountain View, California

From a Single Palauan Seagrass-Coral Community
to the Span of the NOAA National Coral Reef Monitoring Program:
Understanding Local Drivers of Coral Reef Biogeochemistry
Recording Available at COMPASS ON DEMAND

Understanding the drivers of nearshore biogeochemical variability is critical for evaluating how coral reefs will respond to present and future ocean acidification (OA) stress. I will present the results of a 16-day deployment on Ngeseksau Reef, Republic of Palau, where dense beds of seagrass are fringed (and often co-located) with healthy coral communities. Analysis of coupled biogeochemical and hydrodynamic measurements provides a high-resolution record of seagrass-coral metabolism across a range of light availability, depth, and seawater residence time. Primary producers in this community (mainly seagrass) appear to provide windows of elevated pH during which local calcifying organisms may experience some refuge from acidification stress. After discussing this Palau case study, I will broaden our scope to Pacific basin-wide carbonate chemistry analysis, presenting a synthesis of observed spatial and temporal patterns in the reef carbonate system across the Pacific as well as preliminary efforts to model nearshore carbonate chemistry at sub-island scales. To meaningfully predict present and future nearshore OA impacts, we must account for the complexity of the local benthic community, as well as connectivity between offshore and onshore carbonate chemistry conditions. We quantify this connectivity through estimates of nearshore residence time to determine the degree to which the benthos influences the chemistry of the overlying water column. I will present preliminary modeling results for Guam, where we have utilized offshore and reef carbonate chemistry data, local hydrodynamic model outputs, and descriptions of nearshore benthic cover. Together, records of benthic composition, residence time, and oceanic carbonate chemistry allow us to better describe the environmental and ecological drivers of reef-scale processes modifying local biogeochemistry.

Heidi Hirsh is a marine biogeochemist interested in understanding the characteristics of coastal ecosystems that impact community resilience to local and global stressors, particularly ocean acidification (OA). During her Ph.D. at Stanford University, she researched spatiotemporal biogeochemical variability in kelp forest (Monterey Bay, California) and seagrass (Republic of Palau) systems to assess the potential for local amelioration of acidification stress by photosynthetic uptake of carbon dioxide. In her current postdoctoral research with the Cooperative Institute of Marine and Atmospheric Science (CIMAS), she is utilizing NOAA's National Coral Reef Monitoring Program (NCRMP) biogeochemical records, along with local hydrodynamic model outputs and descriptions of benthic community composition, to build statistical models predicting coral reef carbonate chemistry. Ultimately, this correlational modeling will link offshore and nearshore carbonate chemistry, allowing better estimation of carbonate system processes in under-sampled environments and contributing to robust forecasts of OA conditions on coral reefs. Heidi currently lives in Mountain View, CA, where she works remotely with advisors and collaborators in Miami, FL and Honolulu, HI.

Dec 20 (Monday, 11:00 am): Dr. Amina Schartup
Scripps Institution of Oceanography, University of California San Diego

The Biogeochemical Cycle of Mercury in an Era of Environmental Change

Mercury is a naturally occurring element mined and released by humans for more than 3,000 years. Human activities release inorganic forms of mercury that make up most of the mercury present in the environment. However, only the organic form of mercury – methylmercury – biomagnifies in food webs and is associated with neurodevelopmental disorders and cardiovascular impairments. Understanding the microbial reactions and geochemical conditions conducive to the formation of methylmercury has been the focus of many years of research due to its global impacts on the health of fish-consuming wildlife and human populations. Most of the methylmercury exposure for human populations is from marine ecosystems due to bioaccumulation in predatory fish at levels a million times higher than in seawater. This presentation will provide an overview of recent advances in the understanding of mechanisms of methylmercury formation, uptake by phytoplankton, biomagnification in marine food webs, and human exposure. I will also discuss how global environmental changes are affecting the mercury cycle. My approach combines new field data collection, experimental measurements, isotopic tools, and numerical modeling. While this presentation is on the mercury cycle, I will briefly showcase how my approach and tools are easily transferable to other elements and compounds (e.g., selenium, plastics).

Amina Schartup is an Assistant Professor at the Scripps Institution of Oceanography (SIO). Before coming to SIO in 2019, Prof. Schartup was a Research Associate at the Harvard School of Public Health and the Harvard School of Engineering and Applied Sciences. Prof. Schartup also spent two years as an AAAS Science and Technology Policy Fellow at the NSF Office of Polar Program – Arctic Section developing a federal guidance document on pursuing ethical research in the Arctic. Amina Schartup is a recipient of the 2020 Sloan Research Fellowship awarded in "recognition of distinguished performance and a unique potential to make substantial contributions to her field". She received the 2020 Early-Career Research Fellowships by National Academies' Gulf Research Program given to "individuals who have demonstrated superior scholarship, exceptional scientific and technical skills, and the ability to work across disciplines". Prof. Schartup also received a 2021 Scialog Collaborative Innovation Award in Microbiome, Neurobiology and Disease offered to "exemplary early-career scientists from multiple disciplines and institutions across the U.S. and Canada to identify challenges and opportunities in an area of global significance". Prof. Schartup holds a Ph.D. in oceanography from the University of Connecticut, an M.Sc. in geochemistry from the Institut de Physique du Globe de Paris, and a B.Sc. in chemistry from Paris Descartes University.