Zafer Defne, Ph.D.
My research finds its form in providing answers to questions related to coasts and ocean, based on my knowledge of physical oceanography and experience in data sciences.
Biography
Dr. Zafer Defne received his PhD in Coastal and Ocean Engineering from Georgia Institute of Technology, with a minor in Information Technology Applications in Oceanography. His expertise includes computational fluid dynamics and data analysis. His work on numerical modeling of coastal ocean has been used to assess storm surge, residual circulation, sediment transport and water quality, as well as marine renewable energy. His recent research is on assessment of the physical state of coastal wetlands using geospatial data.
Science and Products
Estuarine Processes, Hazards, and Ecosystems
Estuarine processes, hazards, and ecosystems describes several interdisciplinary projects that aim to quantify and understand estuarine processes through observations and numerical modeling. Both the spatial and temporal scales of these mechanisms are important, and therefore require modern instrumentation and state-of-the-art hydrodynamic models. These projects are led from the U.S....
Estuarine Processes Eutrophication
Increased loadings of nutrients to estuaries have altered ecosystem function by encouraging growth of phytoplankton and macroalgae while inducing large swings in dissolved oxygen and threatening the sustainability of seagrass meadows. We are measuring and modeling these processes to understand the future trajectory of estuarine ecosystems.
Estuarine Processes Tidal Wetlands
Tidal wetlands are an important geomorphic and ecological feature of the coastal zone. Our projects deal with the physical forcings that affect wetland stability over event-to-annual timescales, including wave attack, sediment supply, and sea-level rise.
Estuarine Processes Model Development
We are developing new routines within the COAWST model framework to represent coupled bio-physical processes in estuarine and coastal regions. These include routines for marsh vulnerability to waves, estuarine biogeochemistry, and feedbacks between aquatic vegetation and hydrodynamics.
Spatial distribution of water level impact to back-barrier bays
Water level in semi-enclosed bays, landward of barrier islands, is mainly driven by offshore sea level fluctuations that are modulated by bay geometry and bathymetry, causing spatial variability in the ensuing response (transfer). Local wind setup can have a secondary role that depends on wind speed, fetch, and relative orientation of the wind...
Aretxabaleta, Alfredo; Ganju, Neil Kamal; Defne, Zafer; Signell, Richard P. Role of tidal wetland stability in lateral fluxes of particulate organic matter and carbon
Tidal wetland fluxes of particulate organic matter and carbon (POM, POC) are important terms in global budgets but remain poorly constrained. Given the link between sediment fluxes and wetland stability, POM and POC fluxes should also be related to stability. We measured POM and POC fluxes in eight microtidal salt marsh channels, with net POM...
Ganju, Neil Kamal; Defne, Zafer; Elsey Quirk, Tracy; Moriarty, Julia M. Physical response of a back-barrier estuary to a post-tropical cyclone
This paper presents a modeling investigation of the hydrodynamic and sediment transport response of Chincoteague Bay (VA/MD, USA) to Hurricane Sandy using the Coupled Ocean-Atmosphere-Wave-Sediment-Transport (COAWST) modeling system. Several simulation scenarios with different combinations of remote and local forces were conducted to identify the...
Beudin, Alexis; Ganju, Neil Kamal; Defne, Zafer; Aretxabaleta, Alfredo Exposure potential of salt marsh units in Edwin B. Forsythe National Wildlife Refuge to environmental health stressors
Natural and anthropogenic contaminants, pathogens, and viruses are found in soils and sediments throughout the United States. Enhanced dispersion and concentration of these environmental health stressors in coastal regions can result from sea level rise and storm-derived disturbances. The combination of existing environmental health stressors and...
Defne, Zafer; Ganju, Neil K.; Jones, Daniel K.; Reilly, Timothy J.; Aquino, Kimberly C.; Carbo, Chelsea L.; Kaufhold, Erika E.; Benzel, William M.; Fisher, Shawn C.; Griffin, Dale W.; Iwanowicz, Luke R.; Loftin, Keith A. Spatially integrative metrics reveal hidden vulnerability of microtidal salt marshes
Salt marshes are valued for their ecosystem services, and their vulnerability is typically assessed through biotic and abiotic measurements at individual points on the landscape. However, lateral erosion can lead to rapid marsh loss as marshes build vertically. Marsh sediment budgets represent a spatially integrated measure of competing...
Ganju, Neil K.; Defne, Zafer; Kirwan, Matthew L.; Fagherazzi, Sergio; D'Alpaos, Andrea; Carniello, Luca Mean tidal range in salt marsh units of Edwin B. Forsythe National Wildlife Refuge, New Jersey
Biomass production is positively correlated with mean tidal range in salt marshes along the Atlantic coast of the United States of America. Recent studies support the idea that enhanced stability of the marshes can be attributed to increased vegetative growth due to increased tidal range. This dataset displays the spatial variation mean tidal...
Defne, Zafer; Ganju, Neil K. Sediment chemistry and toxicity in Barnegat Bay, New Jersey: Pre- and post-Hurricane Sandy, 2012–13
Hurricane Sandy made landfall in Barnegat Bay, October, 29, 2012, damaging shorelines and infrastructure. Estuarine sediment chemistry and toxicity were investigated before and after to evaluate potential environmental health impacts and to establish post-event baseline sediment-quality conditions. Trace element ...
Romanok, Kristin M. ; Szabo, Zoltan; Reilly, Timothy J.; Defne, Zafer; Ganju, Neil K. Estimating time-dependent connectivity in marine systems
Hydrodynamic connectivity describes the sources and destinations of water parcels within a domain over a given time. When combined with biological models, it can be a powerful concept to explain the patterns of constituent dispersal within marine ecosystems. However, providing connectivity metrics for a given domain is a three-dimensional problem...
Defne, Zafer; Ganju, Neil K.; Aretxabaleta, Alfredo Conceptual salt marsh units for wetland synthesis: Edwin B. Forsythe National Wildlife Refuge, New Jersey
The salt marsh complex of the Edwin B. Forsythe National Wildlife Refuge (EBFNWR), which spans over Great Bay, Little Egg Harbor, and Barnegat Bay (New Jersey, USA), was delineated to smaller, conceptual marsh units by geoprocessing of surface elevation data. Flow accumulation based on the relative elevation of each location is used to determine...
Defne, Zafer; Ganju, Neil K. Evolution of mid-Atlantic coastal and back-barrier estuary environments in response to a hurricane: Implications for barrier-estuary connectivity
Assessments of coupled barrier island-estuary storm response are rare. Hurricane Sandy made landfall during an investigation in Barnegat Bay-Little Egg Harbor estuary that included water quality monitoring, geomorphologic characterization, and numerical modeling; this provided an opportunity to characterize the storm response of the barrier island...
Miselis, Jennifer L.; Andrews, Brian D.; Nicholson, Robert S.; Defne, Zafer; Ganju, Neil K.; Navoy, Anthony S. Quantifying the residence time and flushing characteristics of a shallow, back-barrier estuary: Application of hydrodynamic and particle tracking models
Estuarine residence time is a major driver of eutrophication and water quality. Barnegat Bay-Little Egg Harbor (BB-LEH), New Jersey, is a lagoonal back-barrier estuary that is subject to anthropogenic pressures including nutrient loading, eutrophication, and subsequent declines in water quality. A combination of hydrodynamic and particle tracking...
Defne, Zafer; Ganju, Neil K. A wetting and drying scheme for ROMS
The processes of wetting and drying have many important physical and biological impacts on shallow water systems. Inundation and dewatering effects on coastal mud flats and beaches occur on various time scales ranging from storm surge, periodic rise and fall of the tide, to infragravity wave motions. To correctly simulate these physical processes...
Warner, John C.; Defne, Zafer; Haas, Kevin; Arango, Hernan G.