With increased ocean and air heating, extremes will probably become more common.
Stormwater and Runoff
With increased ocean and air heating, extreme weather is becoming more common in some areas with more intense storms, flooding, and stormwater runoff; more extreme droughts are also documented or predicted in some areas USGCRP (2018). The annual number of billion-dollar extreme weather events in the U.S. has quadrupled since 1980 and average annual damages have more than quadrupled (approx. $17B to $82B) (NOAA, 2020). The summaries in these subsections are, in part, from recent reviews including Herring et al., (2018), USGCRP (2018), Parkinson and Siedel (2018), and IPCC (2019).
More rainfall means increased runoff of fertilizer and sediments into the watershed from tributaries, road sources, and land which contributes to build-up of more muck on the bottom of the lagoon (IRL CCMP, 2019). Old wastewater infrastructure can also be further overloaded and leak at scales ranging from fields of septic tanks through large public sewer facilities, especially with sea level rise and more storm flood events (Young, 2020). These and other factors can combine to increase the chances of harmful algal blooms and ecosystem-scale impacts that include fish kills and threats to public health. At the scale of coastal utilities, many other challenges will occur without adaptation planning and action to develop climate-ready public water infrastructure (e.g., Bloetscher et al. 2011).
Source: City of Port Orange, Volusia County, FL
Source: National Hurricane Center
Increasing ocean heat content and rapidly intensifying hurricanes (including several Category 5 hurricane near-misses of the Indian River Lagoon between 2016 and 2019) can damage large swaths of seagrasses, mangroves, and reefs in our region (e.g., Steward et al., 2006; NOAA Coral Reef Prog., 2020). Human social and economic systems in coastal areas are also highly vulnerable (e.g., Carter et al. 2018; USGCRP, 2018), as many long-time Florida residents know. For example, Hurricanes Jeanne and Francis heavily impacted dozens of communities in the IRL region for years after landfall in 2004 (TCPalm, 2019).
More recently, record high sea surface temperatures, with reduced wind shear and other factors, have been associated with higher than usual major hurricane activity in the North Atlantic in 2017 (e.g., Lim et al., 2018; Klotzbach et al., 2018). September 2017 had more Atlantic named storm days, major hurricane days, and accumulated cyclone energy than any other month on record (Klotzbach et al., 2018).
Extremes in Storms and Drought
Reduced rainfall during drought conditions can also be punctuated by heavy rain events. Results in coastal areas can include pronounced estuarine salinity swings, higher pulses of runoff, and amplified erosion (USGCRP 2018; Parkinson and Siedel 2018). More of these events along the lagoon can impact water quality with both short- and long-term impacts that can further degrade availability and quality of habitat for coastal plant and animal species. For example, several species of IRL fishes are threatened by overdevelopment and changes in freshwater inflows. These impacts can be amplified by climate change drivers such as hotter temperatures and more extreme weather. These changes add to existing pressures on IRL fishes already threatened by overdevelopment, herbicides, and water flow changes, including the River Goby, Bigmouth Sleeper, and Opossum Pipefish (Gilmore et al., 1992).