Joseph Park

Climate Links and Variability of Extreme Sea-Level Events at Key West, Pensacola, and Mayport, Florida

Analysis of long-term coastal tide records at Key West, Pensacola, and Mayport, Fla. examines the variability of extreme high-water events. Linear trends of event water level at Key West and Pensacola support findings elsewhere that increases in extreme water level are consistent with increases in global mean sea level. A link between event variables and the Atlantic multidecadal oscillation (AMO) is found at the Key West and Pensacola stations. Mayport does not exhibit such a link, likely the data are confounded by estuarine flows and oceanographic interactions with the St. Johns River. Quantile regressions and extreme value distributions suggest dynamic trends in the event variables at Key West and Pensacola as a function of AMO, indicating an increased variability in relation to linear models that should be of interest to coastal planners and forecasters.

Scenario-Based Projection of Extreme Sea Levels

ABSTRACT Obeysekera, J. and Park, J., 2013. Scenario-based projection of extreme sea levels. Heavily populated urban centers and natural areas located in low-lying coastal regions are highly vulnerable to sea-level extremes. Historical data at many tide gages suggest that changes over time in extremes generally follow the rise in mean sea level. Assuming this observation to hold in the future, a relationship between mean sea-level rise and its associated extremes with a generalized extreme value distribution can provide future return levels of extreme sea levels. Current projections of future sea level, which include varying degrees of acceleration, may result in large increases in extremes that need to be accounted for in the evaluation of existing coastal projects or in the planning of new ones. Because precise quantitative estimates of the uncertainties in sea-level rise projections are not available, scenario-based approaches have been suggested for project evaluation and design. Here, we propose a general method based on the synthesis of extreme value statistics with sea-level rise scenarios that allows any combination of linear or nonlinear local and global sea-level rise components and can accommodate the nonstationary evolution of sea-level extremes. The temporal variation of the design level of protection for coastal projects, expressed as the return period of extreme events, and the future behavior of the risk are explored. The concepts are demonstrated through application to tide gage data at several locations in the United States.

Probabilistic Projection of Mean Sea Level and Coastal Extremes

AbstractFundamental uncertainties governing sea level rise projections are associated with the rate of acceleration in global sea level rise and the local factors affecting relative sea level. Recent models and observations of global ice sheets and their contributions to sea level, as well as climate models, suggest that significant sea level acceleration is imminent, yet observational data from tide gauges and satellites have not yet found rates consistent with some of the projections. To allow coastal planners a way to incorporate the uncertainties of acceleration, a synthesis of observed sea level data with selected distributions of acceleration and the current rate of rise is proposed to provide probabilistic estimates of future sea levels. The resulting distributions can be adopted in a risk-based framework to assess project vulnerability. As geophysical understanding of the climate-forced sea level dynamics improves, the selection and veracity of these distributions and their sea level projections w...

Seasonal Variability of Tidal Currents in Tampa Bay, Florida

AbstractAn analysis of tidal current variability is performed over seasonal scales for an 11-year record of estuarine currents at two locations in Tampa Bay, Florida. From 2002 to 2012, bimonthly harmonic analyses were performed on current observations collected near the entrance to Old Tampa Bay and at the Sunshine Skyway Bridge. The resultant tidal constituents and nontidal residual were then correlated with other parameters to determine potential physical forcing. Comparison with local wind data suggests that the land-sea breeze cycle can have significant impact on diurnal tidal current flow. Periods of strong land-sea breeze are found to have up to a 30% increase in K1 amplitude compared with periods of weak land-sea breeze. Subtidal weather-scale wind forcing with periods from 2 to 7 days demonstrates a strong correlation with nontidal residual flow, likely resulting from both direct wind forcing as well as the modification of along-estuary water-level gradients. Additionally, the M2 constituent corr...