Jul 23, 2019

Recent increase in catastrophic tropical cyclone flooding in coastal North Carolina, USA: Long-term observations suggest a regime shift

by
Hans W. Paerl, Nathan S. Hall, Alexandria G. Hounshell, Richard A. Luettich, Karen L. Rossignol, Christopher L. Osburn, Jerad Bales
,
Scientific Reports
  • Finds a period of unprecedentedly high precipitation since the late-1990’s, and a trend toward increasingly high precipitation associated with tropical cyclones over the last 120 years consistent with observations elsewhere and with predicted changes in a warming climate
  • States that, since the late-1990’s, coastal North Carolina (NC) has been impacted by 36 tropical cyclones, with three recent storms resulting in 2-percent or less annual exceedance levels flood events in the NC coastal plain
  • Examines continuous rainfall records for coastal NC since 1898, and takes a closer look at the apparent increased frequency and magnitudes of extreme tropical cyclone-driven flood events since 1999 in North Carolina
  • Questions whether the apparent increased frequency and magnitudes of such events is just coincidence or whether there is a regime shift in tropical cyclone flooding and associated ecosystem impacts
  • Looks at three extreme floods resulting from high rainfall tropical cyclone events in the past 20 years:
    • At Kinston, NC, Hurricane Floyd (1999) was rated a 2-percent exceedance level flood
    • The most recent Hurricane Florence (2018) also resulted in a 2-percent annual exceedance level year flood
    • Peak flow following Hurricane Matthew (2016) resulted in a 0.8-percent annual exceedance level flood in Kinston, NC
  • Finds that these three rainfall events are a consequence of the increased moisture carrying capacity of tropical cyclones due to the warming climate
  • States that the observations are consistent with similar observations elsewhere and with predicted hydrologic, nutrient and carbon flux changes taking place in a warming climate
  • The authors state they do not offer a full attribution analysis, which may be conducted in a variety of ways including numerical modeling that replicates the events our observations are consistent with observations elsewhere and with predicted changes in a warming climate
  • Concludes that rather than attributing a particular event to global warming, we should consider whether a warming climate made these events more likely, which our records suggest is the case for coastal NC